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

indicators of aqueous alteration in cm carbonaceous chondrites microtextures of a layered mineral containing fe s o and ni a petrographic and transmission electron microscopy study of the mighei murchison and murray cm carbonaceous chondrites shows that much of the cm matrix material was probably produced by aqueous alteration of olivine pyroxene sulfide and metal the amount of cm matrix appears to be proportional to the degree of alteration as suggested by mcsween 1979 and microtextures of pcp poorly characterized phase provide evidence of the progressive alteration pcp is divided into two major types one occurs in chondrules and aggregates and consists largely of an fe ni s o phase type i and the other occurs in matrix and consists of the fe ni s o phase and cronstedtite in various proportions type ii microtextures of pcp suggest that it resulted from a three stage alteration process 1 1 type i was produced by alteration of kamacite in chondrules and aggregates presumably early in the parent body regolith 2 2 as the alteration advanced olivine and pyroxene were converted to serpentine type i pcp separated from chondrules and aggregates into the matrix during regolith gardening simultaneously the fe ni s o phase reacted with si released by alteration of olivine and pyroxene producing well formed platy cronstedtite and coherent intergrowths of the fe ni s o phase and cronstedtite the fe ni s o phase also recrystallized into platy and pod like crystals fe s ni cr and p were leached out of type i pcp and were deposited as small grains of fe ni sulfides magnetite chromite and a mineral unidentified containing fe ni cr and p as a result pcp came to consist primarily of the fe ni s o phase and cronstedtite i e type ii pcp 3 3 during continued alteration the well formed crystals of the fe ni s o phase cronstedtite and their intergrowths in type ii pcp were replaced by poorly formed fibers in comparison to other cm chondrites mighei murchison and murray are relatively unaltered their matrices retain abundant amounts of the fe ni s o phase and cronstedtite commonly as distinctive pcp grains which account for a large proportion of the fe in these meteorite matrices in more altered cm chondrites much of the fe ni s o phase was probably consumed to produce cronstedtite magnetite and sulfides with further alteration cronstedtite itself reacted with the serpentine to form ferroan serpentine thus the cm matrix was increasingly enriched in mg with alteration and pcp was increasingly degraded and intimately mixed with the magnesian phyllosilicates

oxygen isotope studies of carbonaceous chondrites abstract the carbonaceous chondrites display the widest range of oxygen isotopic composition of any meteorite group as a consequence of the interaction of primordial isotopic reservoirs in the solar nebula these isotopic variations can be used to identify the reservoirs and to determine conditions and loci of their interactions we present a comprehensive set of whole rock analyses of cv co ck cm cr ch and ci chondrites as well as selected components of some of these meteorites a simple model is developed which describes the isotopic behavior during parent body aqueous alteration processes the process of thermal dehydration also produces a recognizable effect in the oxygen isotopic composition

calcrete profile development in quaternary alluvial sequences southeast spain implications for using calcretes as a basis for landform chronologies a detailed study of the morphology and micro morphology of quaternary alluvial calcrete profiles from the sorbas basin shows that calcretes may be morphologically simple or complex the simple profiles reflect pedogenesis occurring after alluvial terrace formation and consist of a single pedogenic horizon near the land surface the complex profiles reflect the occurrence of multiple calcrete events during terrace sediment aggradation and further periods of pedogenesis after terrace formation these complex calcrete profiles are consequently described as composite profiles the exact morphology of the composite profiles depends upon 1 the number of calcrete forming events occurring during terrace sediment aggradation 2 the amount of sediment accretion that occurs between each period of calcrete formation and 3 the degree of pedogenesis after terrace formation simple calcrete profiles are most useful in establishing landform chronologies because they represent a single phase of pedogenesis after terrace formation composite profiles are more problematic pedogenic calcretes that form within them may inherit carbonate from calcrete horizons occurring lower down in the terrace sediments in addition erosion may lead to the exhumation of older calcretes within the terrace sediment calcrete inheritance may make pedogenic horizons appear more mature than they actually are and produce horizons containing carbonate embracing a range of ages calcrete exhumation exposes calcrete horizons whose morphology and radiometric ages are wholly unrelated to terrace surface age composite profiles are therefore only suitable for chronological studies if the pedogenic horizon capping the terrace sequence can be clearly distinguished from earlier calcrete forming events thus a detailed morphological micro morphological study is required before any chronological study is undertaken this is the only way to establish whether particular calcrete profiles are suitable for dating purposes copyright 2003 john wiley sons ltd

late quaternary large scale rotational slides induced by river incision the arroyo de gor area guadix basin se spain the arroyo de gor is a highly incised stream up to 200 m that has eroded into the pliocene pleistocene infill of the guadix basin in the betic cordillera se spain this paper concentrates on a particular reach of this stream namely the cenascuras gorafe reach where abundant inactive rotational slides can be recognized on both hillslopes of the canyon shaped valley the rotational slides have surface areas of 5 15 ha and volumes of mobilized material of 5 15 hm3 these rotational slides can be recognized by their main scarps which are still well featured at both margins of the valley as well as by the counter hillslope rotation of the strata in their bodies the surfaces of rupture are concave their width being greater than their length i e the landslides are elongated in a direction perpendicular to the landsliding displacement and parallel to the stream at depth the surfaces of rupture developed on fine grained sediments mostly clays underlying the conglomerates and sands affected by the rotational slides the clays at the surface of rupture are smectite rich and show several features produced by the landsliding such as striations and sigmoidal shaped structures the cenascuras gorafe canyon has been developed by a combination of entrenchment fracturing and landsliding initial deep entrenchment of the stream is attributed to a base level lowering related to the capture of the former endorheic basin by the gualdalquivir river in the late pleistocene this river incision created a canyon with subvertical unstable walls which due to gravitational instability would give way to vertical open tension cracks some distance from the canyon edge the tension cracks would end at depths equal to the base of the canyon which also coincides with the contact between the conglomerates and the underlying clays the rotational slides are thought to have occurred during heavy rains by a combination of piping which would have lengthened the tension cracks and infiltration which would reduce the shear strength along the gently dipping contact between conglomerates and the underlying clays thus the blocks bounded by the tension cracks and the subhorizontal lithological contact would slide under their own weight on the subhorizontal surfaces of reduced shear strength several age constraints lead us to tentatively assign the landslides to the isotope stage 5 around 32 ka an interglacial period agreed to be wetter and slightly warmer than the present day semi arid climate

non nebular origin of dark mantles around chondrules and inclusions in cm chondrites abstract our examination of nine cm chondrites that span the aqueous alteration sequence leads us to conclude that compact dark fine mantles surrounding chondrules and inclusions in cm chondrites are not discrete fine grained rims acquired in the solar nebula as modeled by metzler et al accretionary dust mantles in cm chondrites evidence for solar nebula processes geochim cosmochim acta 56 1992 2873 2897 nebular processes that lead to agglomeration produce materials with porosities far higher than those in the dark mantles we infer that the mantles were produced from porous nebular materials on the cm parent asteroid by impact compaction a process that produces the lowest porosity adjacent to chondrules and inclusions compaction was followed by aqueous alteration that formed tochilinite serpentine ni bearing sulfide and other secondary products in voids in the interchondrule regions metzler et al reported a correlation between mantle thickness and the radius of the enclosed object in yamato 791198 we find no correlation when all sizes of central objects and dark lumps are included but a significant correlation r2 0 44 if we limit consideration to central objects with radii 35 m a moderate correlation is also found in que 97990 we suggest that impact induced shear of a plum pudding like precursor produced the observed mantles these were shielded from comminution during impact events by the adjacent stronger chondrules and inclusions some mantles in cm chondrites with low degrees of alteration show distinct layers that may largely reflect differences in porosity typically a gray uniform inner layer is surrounded by an outer layer consisting of darker silicates with bse bright speckles the cm chondrite objects characterized as primary accretionary rocks by metzler et al did not form in the nebula but rather on the parent body the absence of solar flare particle tracks and solar wind implanted rare gases in these clasts reflect their lithified nature and low surface volume ratios during the period when they resided in the regolith and were subject to irradiation by solar particles the clasts are analogous to the light colored metamorphosed clasts in ordinary chondrite regolith breccias which also lack solar flare particle tracks and solar wind gas

the mediterranean mare nostrum of earth sciences the mediterranean area is one of the most appealing natural laboratories in the world to study geodynamic and paleoclimatic processes on different scales consequently the mediterranean sea can be considered as the mare nostrum our sea of earth sciences its semi enclosed land locked configuration in a convergent setting between africa in europe in combination with its latitudinal position makes the mediterranean extremely suitable to study both fundamental plate tectonic processes and astronomically induced oscillations in climate for many years to come the mediterranean will certainly remain a fascinating area where an integrated and multi disciplinary approach will increasingly contribute to our understanding of geological geophysical geodetical and geochemical processes in an accurate and high resolution time frame

a new chronology for the middle to late miocene continental record in spain abstract the first detailed chronology for the middle to late miocene continental record in spain is presented based on high resolution magnetostratigraphic data of mammal bearing sections which were studied in several basins calatayud daroca teruel valles penedes duero and jucar cabriel our results indicate that these sections compose an almost complete magnetostratigraphic succession from the lower aragonian mn4 to the middle turolian mn12 seven successive mammal neogene mn zone boundaries are directly dated in these sections which often contain faunas of two successive zones in superposition the three oldest boundaries are dated in the aragonian type area calatayud daroca basin the mn4 mn5 boundary vargas section occurs in chron c5cr o with a corresponding age of 17 26 0 01 ma the mn5 mn6 boundary aragon section in chron c5acn 0 8 with an age of 13 75 0 03 ma and the mn6 mn7 8 boundary aragon section in the interval c5ar 1n c5ar 3r with an age of 12 75 0 25 ma the mn7 8 mn9 aragonian vallesian boundary occurring in chron c5r 1n at 11 1 ma and the mn9 mn10 boundary in chron c4ar 3r at 9 7 0 1 ma are recorded in the valles penedes basin vallesian type area and are supported by the results from the duero basin torremormojon section in the turolian type area teruel basin the mn10 mn11 vallesian turolian boundary la gloria section occurs in chron c4an y at 8 7 0 1 ma taking into account the pre existing data from the jucar cabriel basin the mn11 mn12 boundary cabriel valley section is recalibrated to c4n 1n at an age of 7 5 0 1 ma

sedimentary stable isotope and micropaleontological records of paleoceanographic change in the messinian tripoli formation sicily italy abstract the tripoli formation 6 96 5 98 ma of the central sicilian basin provides a good record of the paleoceanographical changes that affected the mediterranean during the transition from slightly restricted conditions to the onset of the messinian salinity crisis the falconara gibliscemi section has been selected for an integrated approach at a high resolution scale using sedimentology stable isotopes of the carbonates and microfossils the sedimentary succession includes 46 precession controlled cycles resulting from the periodical increase in biosiliceous productivity diatomites that followed the deposition of marls and pinkish laminites which appear as sapropel type deposits induced by the oceanic fertilization by terrestrial nutrients during wet periods higher scale environmental changes are superimposed to this precession forced rhythmicity there is a general trend of increasing basin restriction from near marine conditions at the base of the tripoli to semi closed settings in its uppermost part which are the prelude of the salinity crisis this pattern reflects the hydrological response of the mediterranean to the progressive decrease of the atlantic inputs and an enhanced influence of the climate on depositional conditions however this evolution is not linear and shows successive phases of different duration during the first period until 6 71 ma open atlantic mediterranean exchanges maintained relatively stable marine conditions the second period 6 71 6 29 ma marks an important step in the basin restriction with a wider range of salinity fluctuations and an increased bottom stagnation the 6 71 ma event which is correlated at a mediterranean scale may have resulted from shallowing of the mediterranean gateway under a tectonic control this shallowing reduced the oceanic inputs resulting in an increased climatic constraint of the mediterranean hydrology during the third period 6 29 6 03 ma an increase of the surface water salinity resulted in stressful conditions for the marine microfauna the 6 29 ma change is a major step in the restriction that may be correlated with the intensification of the glaciation recorded in the atlantic which could have enhanced the effects of the tectonic closure the last two cycles 48 and 49 that underlie the calcare di base witnessed the rapid transition to a semi closed mediterranean setting characterized by large variations of salinity from diluted to hypersaline conditions under a dominant climatic control and by the nearly complete disappearance of the marine organisms long trend environmental changes recognized within the tripoli formation resulted from a complex set of interfering factors controlling the water fluxes exchanged between the mediterranean and the world ocean most of the rapid changes identified in falconara gibliscemi at 7 16 6 71 and 6 29 ma that occurred simultaneously in the western and eastern mediterranean were mainly controlled by the stepwise tectonic closure of the atlantic connections although a glacio eustatic overprint cannot be completely excluded

the tortonian salinity crisis of the eastern betics spain the late miocene depositional history of the lorca and fortuna basins both occupying an internal position in the eastern betics of spain is marked by a regressive sequence from open marine marls via diatomites and evaporites to continental sediments based on facies similarities these evaporites have often been correlated to the well known mediterranean evaporites of the messinian salinity crisis although this correlation was never substantiated by reliable chronological data in this paper we present an integrated stratigraphy of this regressive sequence which shows that the evaporites of the lorca and fortuna basins are entirely of late tortonian age and as such have no relation with the messinian salinity crisis the main phase of basin restriction resulting in deposition of diatomites and evaporites took place at 7 8 ma while the last marine deposits massive evaporites of the lorca basin are dated at 7 6 ma consequently this tortonian salinity crisis of the eastern betics had a duration of approximately 200 kyr while continental deposition prevailed throughout the entire messinian as also revealed by the fossil mammal record the tortonian salinity crisis of the eastern betics is obviously related to a local phase of basin restriction caused by uplift of the metamorphic complexes at the basin margins probably in concert with strike slip activity along sw ne trending fault systems the development of a submarine sill is of crucial importance for the increase in salinity because it allows marine waters to continuously enter the basin at the surface while it restricts or prevents the outflow of dense saline waters at depth furthermore we show that evaporite and diatomite cyclicity in these restricted basins is predominantly related to precession controlled circum mediterranean climate changes and that glacio eustatic sea level changes only play a minor role it is remarkable that the lithological sequence of the tortonian salinity crisis mimics in many aspects that of the messinian salinity crisis this suggests that the diatomaceous facies is an essential part of the lithological sequence associated with basin restriction fl 2000 elsevier science b v all rights reserved

mineralogy and petrology of chondrules and inclusions in the mokoia cv3 chondrite all objects 100 m in apparent diameter in five polished thin sections of the mokoia cv3 chondrite were studied and classified number and volume percentages and mean apparent size of each type of chondrule and inclusion were determined three major types of olivine chondrules were observed igneous chondrules recrystallized chondrules and chondrules that appear to be accretional aggregates coarse grained cai s have igneous textures and mineral parageneses while fine grained cai s are aggregates containing varying proportions of al rich concentric objects ca rich chaotic material and inclusion matrix chondrules and refractory inclusions in mokoia and allende are broadly similar in texture and mineral chemistry but mokoia refractory inclusions contain phyllosilicates rather than feldspathoids and melilite rich cai s are more abundant in allende we think that most cai s formed during the metamorphism partial melting and incomplete distillation of primitive dust aggregates when they were heated in the solar nebula in the process ca rich melt appears to have been physically separated from al rich residues producing the observed fractionation of ca from al into distinct constituents of cai s some cai s may be aggregates of devitrified amorphous metastable condensates inclusion matrix may have condensed from silicate rich vapors produced during distillation mokoia inclusion matrix contains phyllosilicates that are probably primitive nebular material

a large mammal site in a meandering fluvial context fonelas p 1 late pliocene guadix basin spain sedimentological keys for its paleoenvironmental reconstruction abstract the fonelas p 1 large mammal site is located stratigraphically in the youngest unit late pliocene pleistocene of the endorheic fill of the guadix basin betic cordillera at the site location this unit is represented by fluvial sediments of the basin s axial drainage system the general succession of the site consists of stacked fining upward cycles basically beginning with gravel and or sand filling a meandering channel and concluding with floodplain mud and carbonate each of the cycles is made up of four facies associations determined by sedimentological analysis of the sections measured in the paleontological excavation of the site these associations correspond to sedimentation in definite areas of the fluvial system a filling of a sinuous channel at maximum activity b levee deposits c abandoned channel and d floodplain in the cycle in which the site is located there is a fifth association e where the main fossil concentration is found fonelas p 1 this is a facies bioturbated by mammals moving over sediments of the abandoned channel association c by space time reconstruction of the fluvial environments we can infer that the morphological depression caused by a meander abandonment due to chute cut off was used as a hyena den the animal settlement ended when overflow from the laterally migrating active channel began to bury the abandoned meander with floodplain sediments

facies architecture geochemistry and palaeoenvironmental reconstruction of a barrage tufa reservoir analog betic cordillera s spain continental carbonates are currently of high interest for the oil and gas industry as they have proved to be good reservoir rocks in brazil and angola offshore oil fields in this article a tufa system in which continental carbonates formed mainly in the pliocene rambla becerra tufa system guadix basin betic cordillera s spain is described in detail and a model proposed for its formation and evolution through time several stages of tufa growth have been identified in the field intercalated between stages of progradation of alluvial fan sediments the tufa system connects laterally with the fluvial system developed in the axial valley of the guadix basin during the pliocene and the pleistocene indicating that the tufa formation was coetaneous with the periods of lateral expansion of the fluvial system floodplain that in previous works have been interpreted as more humid stages and potentially warmer the absence of extraclasts in the tufa sediments points to the low activity of the alluvial fans during the tufa formation and therefore supports the idea that the main tufa growth happened during more humid stages and the alluvial fans developed further during the more arid periods which is consistent with other recent findings in the guadix basin the tufa growth is represented by four main stages the second one bearing the best example to study as a potential reservoir analog as the main outcrop is a discrete body with a specific geometry and facies distribution this main outcrop is a mound shaped tufa build up formed by prograding sigmoids of clastic tufa interpreted as the ramp like buttresses developed after a barrage in a barrage tufa system from a preliminary isotopic study of the carbonates forming the barrage tufa system and by comparison with other tufas and travertines the oxygen and carbon stable isotopes point to an intermediate situation between a palustrine tufa and a travertine this information when added to the sedimentological data supports the idea that water feeding the tufa system probably had different sources a meteoric one coinciding with the surface runoff and a groundwater one probably in the form of springs fed by groundwater from the nearby aquifers that still exist in the mesozoic carbonates that form the external zones of the betic cordillera in the area

iron rich aureoles in the cm carbonaceous chondrites murray murchison and allan hills 81002 evidence for in situ aqueous alteration iron rich aureoles in cm carbonaceous chondrites are previously unidentified domains of aqueously altered matrix material whose feo content may exceed that of the surrounding matrix by up to more than 15 wt we describe the petrography and mineralogy of these objects in the cm chondrites murray murchison and allan hills alh 81002 the size of fe rich aureoles ranges from a few hundred microns to several millimeters in diameter and appears to be a function of the degree of alteration of the host chondrite the origin of fe rich aureoles is related to the alteration of large metal grains that has resulted in the formation of characteristic pcp rich reaction products that are frequently observed at the centers of the aureoles this suggests that fe rich aureoles in cm chondrites are the result of the mobilization of fe from altering metal grains into the matrix the fact that fe rich aureoles enclose numerous chondritic components such as chondrules calcium aluminum rich inclusions cais and mineral fragments as well as their radial symmetric appearance are strong evidence that they formed in situ and that significant directional fluid flow was not involved in the alteration process this and additional constraints such as the distribution of s and other elements as well as the inferred alteration conditions are consistent with in situ parent body alteration the observations are however entirely incompatible with preaccretionary alteration models in which the individual cm chondrite components have experienced diverse alteration histories the presence of numerous intact aureoles in the brecciated cm chondrites murray and murchison further suggests that the alteration occurred largely after brecciation affected these meteorites therefore the progressive aqueous alteration of cm chondrites may not be necessarily coupled to brecciation as has been previously proposed

paleobiogeography of scleractinian reef corals changing patterns during the oligocene miocene climatic transition in the mediterranean abstract during the oligocene miocene greenhouse to icehouse climatic transition the biogeography of reef corals or zooxanthellate like scleractinian corals was gradually changing from a pan tropical tethyan province in the eocene to three reef coral provinces of the western atlantic caribbean indo pacific and mediterranean our reefcoral database encompasses updated and homogenized data on paleoenvironmental and systematics of scleractinian corals occurring in the oligocene and miocene outcrops from circum mediterranean regions provided by most of relatively recently published data in the literature and by the study of published and unpublished collections of coral specimens from the same area including the important collections housed at the mnhn paris and our own collections as there is no validated direct criterion for the identification of the coral zooxanthellate symbiosis in the fossil record and considering the difficulty to use the biogeochemical approaches in the context of this study the subjectivity of the morphological criteria and the relative recent age of the fossil corals we are dealing with a uniformitarian approach has been used for inferring the symbiotic status of scleractinian genera in reefcoral among the 158 genera included in our database 93 can be considered as zooxanthellate and 10 have a doubtful zooxanthellate status this relatively exhaustive database was used to reconstruct the temporal and spatial distribution of scleractinian corals in the mediterranean during the oligocene miocene time in order to discuss the interplaying effects of the global cooling at that time the re organization of the tethyan realm resulting from the african arabian and eurasian plate collision and the emergence of the alpine chains driving the gradual northward movement of the whole region outside the tropical subtropical belt it is shown that the structure of the mediterranean z coral oligocene miocene paleobiodiversity was characterized by many geographically restricted genera with a moderate to short stratigraphical range and a few long ranging widespread genera a major consequence of this structure is that the extinction pattern has proceeded through the preferential extinction of rare occurrence genera through time the potential rapid long distance dispersal of most coral larvae compared to the size of the oligocene miocene mediterranean explains why no biogeographical subprovinces can be distinguished for the z coral fauna on a local scale ecological processes tend to sort coral taxa by limiting z coral development to geographically restricted and discontinuous areas this accounts for the large amount of geographically restricted taxa forming the mediterranean coral fauna the interaction of plate tectonics alpine orogenesis and climate at local to subregional scales exerts strong controls over the spatio temporal distribution of z coral assemblages within the circum mediterranean realm in particular we suggest that the richness and composition of the eastern atlantic coral fauna are indirectly related to the opening and closure of the eastern seaway connection with the indian ocean which controlled the e w circulation of surface waters and hence the westwards dispersal of pelagic larvae at the scale of the whole region the gradual regional climatic change produced by the northwards migration of the entire area superimposed on the global cooling appears in large part responsible for the extinction pattern of z corals through time in the mediterranean biogeographical province

sensitivity of mediterranean thermohaline circulation to gateway depth a model investigation 1 the neogene sedimentary record of the mediterranean sea holds evidence for changes in water properties and circulation these paleoceanographic changes have been attributed to changes in the flow through the ocean gateway between the mediterranean sea and the atlantic ocean we use an oceanic general circulation model to achieve quantitative physics based understanding of the effect of changes in the depth of the gateway such as may result from tectonic activity or variation in sea level to isolate these effects we use idealized basin geometry and impose simplified atmospheric forcing a reference experiment with present day sill depth demonstrates that the model simulates reasonably well the main features of the present day mediterranean thermohaline circulation as inferred from observations and previous numerical studies subsequently a series of sensitivity simulations is performed with different sill depths the model results show that mediterranean temperature salinity and thermohaline circulation depend strongly on sill depth as the sill depth decreases the upper overturning cell is quasi linearly reduced in strength while contrary to what one would expect the deep cell intensifies and does so in a nonlinear way we find that a shoaling of the sill depth induces a blocking effect on the outflow waters which creates a strong recirculation in the deep layers strengthening the deep cell nevertheless deep water formation is reduced and as a consequence the ventilation of the deep layers diminishes we identify three different circulation modes of the mediterranean thermohaline circulation depending on the sill depth shallow sill moderate sill and deep sill modes coupled with strong weak and negligible blocking effects respectively our results are consistent with the pre messinian paleoceanographic record of the mediterranean sea and may be useful to understanding the behavior of other land locked basins both extant and from the geological past

messinian paleoenvironmental evolution in the lower guadalquivir basin sw spain based on benthic foraminifera abstract benthic foraminiferal assemblages of a drill core from the lower guadalquivir basin northern gulf of cadiz sw spain have been analyzed in order to reconstruct the paleoenvironmental evolution in the vicinity of the betic seaways during the messinian the core consists of marine sediments ranging from the latest tortonian to the early pliocene changes in the abundance of certain marker species planktonic benthic ratio p b ratio paleodepth estimated with a transfer function content of sand grains and presence of glauconitic layers indicate a complete transgressive regressive sea level cycle from the bottom to the top of the section an abrupt sea level rise from inner middle shelf to middle slope is recorded at the lowermost part of the core latest tortonian earliest messinian followed by a relatively rapid shallowing from middle slope to outer shelf magnetobiostratigraphic data show that this sea level fall postdates the onset of the messinian salinity crisis msc in the mediterranean finally the early pliocene deposits are interpreted as inner middle shelf changes in the benthic foraminiferal assemblages through the core are mainly controlled by the trophic conditions specifically by the quantity and quality of the organic matter reaching the sea floor the upper slope and part of the outer shelf assemblages are highly diverse and dominated by shallow infaunal species indicating a generally mesotrophic environment with moderate oxygenation these environments have likely been affected by repeated upwelling events documented by increased abundance of uvigerina peregrina s l an opportunistic species thriving in environments with enhanced labile organic matter supply the assemblages of the transitional interval between upper slope to outer shelf and of the outer shelf are generally characterized by a relatively low diversity and epifaunal shallow infaunal taxa indicating oligotrophic and well oxygenated conditions the inner middle shelf assemblages are characterized by very low diversity and dominance of intermediate to deep infaunal taxa suggesting an eutrophic environment with low oxygen content these assemblages are dominated by nonion fabum and bulimina elongata two taxa that are able to feed from continental low quality organic matter most likely derived from river run off the paleoenviromental evolution on the atlantic side of betic and rifian seaways is similar during the messinian with a messinian continuous sea level lowering driven by regional tectonic uplift and upwelling related waters reaching the upper slope this study will further contribute to understand the role of tectonics on the sea level changes as well as on the closure of the atlantic mediterranean gateways that led to the msc and on the paleoceanography on the atlantic sides of these corridors

a reconstruction of late miocene mediterranean circulation patterns using benthic foraminifera abstract extensive research on the late miocene mediterranean has solved a number of questions concerning the development of the area but questions remain on for instance the mediterranean water circulation patterns knowledge of preferably quantitative oxygen contents of water masses could be of help to reconstruct paleo circulation and understand how this contributed to the development of the mediterranean messinian salinity crisis msc bottom water oxygenation is usually estimated qualitatively or semi quantitatively at best from abundances of infaunal benthic foraminifera from stable carbon isotope data or redox sensitive elements we present data from six mediterranean land sections and one section located at the atlantic side of the rifian corridor as an atlantic reference location we introduce a semi quantitative reconstruction of oxygen levels at the sediment water interface employing a simple index that operates on a scale from 1 low oxygen to 5 normal to high oxygen using this method we present a tentative reconstruction of the mediterranean water circulation in the period preceding the continuous development towards the msc which started at 7 17 ma we found that during the late miocene an anti estuarine circulation was likely quite comparable to the modern pattern deep water formation appears to have existed in the central northeastern part of the basin around 7 2 ma constriction of the rif corridor morocco led to restricted exchange of mediterranean and atlantic water masses a reduction of the deep circulation and decreasing bottom water ventilation deep water formation weakened and the mediterranean hydrography changed thoroughly eventually contributing to the development of the msc

the upper tortonian lower messinian at monte dei corvi northern apennines italy completing a mediterranean reference section for the tortonian stage abstract a high resolution integrated stratigraphy including biostratigraphy magnetostratigraphy tephrostratigraphy and cyclostratigraphy is presented for the upper tortonian and lower messinian upper miocene at monte dei corvi numerical age control comes from a combination of magnetobiostratigrapic dating and astronomical tuning while radioisotope dating of ash layers produced less reliable ages the deep marine succession is characterized by large scale non repetitive stratigraphic changes allowing the discrimination between a lower brownish rossini and euxinic shale interval the sedimentary cycles which occur superimposed on these large scale changes are related to astronomical climate forcing astronomical tuning of the sedimentary cycles provides not only absolute ages for biostratigraphic events reversal boundaries and volcanic ash layers but also for the observed non cyclic changes these can be linked to environmental and geodynamic changes in the mediterranean region preceding the messinian salinity crisis the beginning of the brownish interval marked by tripartite cycles at 8 017 ma coincides with tectonic re arrangements in the mediterranean such as compression in the betics and opening of the rifian corridor at 7 616 ma the change to the calcareous rossini interval can be linked to tectonic uplift in the northern apennines and the deepening of the rifian corridor while the betic corridor became restricted coinciding with the end of evaporite deposition in the eastern betics the change to euxinic shales at 7 168 ma reflects basin wide restriction marked by diatomite and sapropel formation in the mediterranean basin related to the severely constricted betic and rifian corridors the occurrence of a tripartite construction of cycles in the euxinic shales at 6 719 ma coincides with diatomite formation in the eastern mediterranean uplift and shallowing in the northern apennines and further constriction of the atlantic gateways we conclude that late tortonian early messinian tectonic and environmental events occur remarkably synchronously in the mediterranean basin and most likely result from a combination of geodynamic processes and eccentricity controlled climatic changes in combination with the upper serravallian and lower tortonian interval which includes the formal tortonian global stratotype section and point gssp the monte dei corvi is the only complete section in the mediterranean covering the entire tortonian stage we therefore propose the monte dei corvi section as tortonian reference section particularly for the mediterranean region in addition it may serve as a unit stratotype for the tortonian

the effects of fluctuating base level on the structure of alluvial fan and associated fan delta deposits an example from the tertiary of the betic cordillera spain the villanueva complex is a lacustrine alluvial fan fan delta system which accumulated on the northern margin of the guadix basin during the pliocene five transitional zones can be distinguished from proximal to distal areas proximal alluvial fan mid fan fan fringe transition zone proximal fan delta and distal fan delta lacustrine this paper focuses on sedimentation in the fan fringe and the proximal fan delta areas where the effects of fluctuations in the base level lacustrine level are more easily observed the stratigraphical succession is here characterized by an alternation of fine lacustrine sediments mudstones and siltstones and gravels the gravels appear as isolated channels stacked channels lenses and sheets the isolated channels which have a v shaped profile and better developed wings towards the top appear in the fan fringe zone and in the fan delta the stacked channels originate in the fan fringe zone and evolve laterally and distally to isolated channels the lenticular gravel bodies lenses are well represented throughout the fan delta and present small channels at the base indicating a radial flow pattern finally the sheets are characteristic of the fan fringe zone the first episodes of channel incision occurred at lowstand lake level the channels and lenses developed in rising lake level conditions and sheet deposit took place at highstand lake level although the final form of the lithosome was heavily controlled by the fluctuations in lake level it depended on the relative proportions of gravel and silt sedimentation the gravel siltstone interface therefore represents an equilibrium surface between the proportions of sedimentation of these lithologies the bodies mentioned above are organized in coarsening and thickening upwards sequences tens of metres thick in which a distal to proximal evolution can be observed from isolated channels to lenses or from stacked channels to sheets the building and thickness of these sequences were controlled by fluctuations in the lake level an initial fall in base level caused lengthening of the channels and entrenchment from distal to proximal areas and a continuous increase in supply due to erosion in the drainage basin installed on the subaerial fan when the lake level rose lobes were formed at the channel endings and overbank processes were made possible thus generating radial channels whose levees were formed by amalgamation with the levees of the main lens channels at the same time sheets were formed in proximal areas where the available amount of sediment was greater

the european record of the gerbil myocricetodon rodentia mammalia and its bearing on the messinian salinity crisis abstract the gerbillid myocricetodon is mainly known from the miocene of africa and asia but some small samples of this genus have been identified in southwestern europe interpreted as immigrants driven by the messinian salinity crisis however the specific determination of these european populations and their relationships with african forms have proved controversial the population from negratin 1 guadix basin southern spain was attributed to the african species myocricetodon jaegeri but other european samples have still not been determined at the specific level here we describe the material of myocricetodon from almenara m eastern spain which represents the most abundant sample of the genus known from europe confirming its assignation to m jaegeri we also analyze material from salobrena pino mojon southern spain and castelnou 3 southern france concluding that these samples belong to the same species the presence of these coeval and conspecific populations of myocricetodon is explained by a single migratory event from northern africa the occurrence of myocricetodon interpreted as an indicator of warm and arid conditions is restricted to southern and eastern spain and the southeastermost extreme of france being mainly limited to the mediterranean coast it is absent in other iberian areas such as the granada cabriel and teruel basins despite their rich and well studied record of late miocene mammals this distribution suggests the existence of different environmental more humid conditions in those areas during the latest miocene as already proposed for the granada basin our data also indicate that the presence of myocricetodon in europe was limited to a short interval close to the miocene pliocene boundary contrarily to other gerbils namely debruijnimys which persisted during the pliocene this suggests that myocricetodon could be extremely sensitive to environmental factors and its occurrence in europe was linked to a specific moment of arid conditions

a stratigraphic framework for the pliocene pleistocene continental sediments of the guadix basin betic cordillera s spain the central sector of the guadix basin betic cordillera s spain hosts some of the most significant pleistocene large mammal sites in europe the basin infill is divided into six genetic units the three lower with marine sediments and the remainder mainly continental as the environmental characterization of the sediments is crucial to understand the ecologic and geologic processes leading to the formation of these sites a stratigraphic sedimentologic and petrologic study is presented combining a lithologic correlation with previous biostratigraphic data and new magnetostratigraphic data a detailed litho bio and magnetostratigraphic scheme has been developed for the study area it shows the stratigraphic architecture of the central sector of the guadix basin together with the age and the relative spatial position of the most important mammal sites as well it has been also helpful to identify several isochronous surfaces to establish the exact position and the age of the boundary between the two last units of the continental infill in the guadix basin and to calculate sedimentation rates

correlated petrologic and geochemical characteristics of co3 chondrites many properties of co3 chondrites have been shown previously to have resulted from thermal metamorphism petrologic subtypes 3 0 3 7 have been assigned to members of the group additional properties that correlate with the metamorphic sequence but seem to have resulted from hydrothermal alteration include the modal abundance of amoeboid olivine inclusions aoi chondrule size the types of refractory inclusions and whole rock o isotopic composition the percentage of rimmed aoi increases with petrologic subtype the rims most likely formed during hydrothermal alteration the previously reported correlation between aoi abundance and chondrite subtype is probably an artifact due to the difficulty in recognizing small unrimmed aoi in the least metamorphosed co3 chondrites because large 200 micron size porphyritic chondrules have nearly the same mean size in all co3 chondrites it seems likely that the correlation between chondrule size and subtype is due to alteration of the smallest chondrules to the point of unrecognizability as complete objects in the more metamorphosed co3 chondrites the previously reported decrease in the proportion of melilite rich refractory inclusions with increasing petrologic subtype may have resulted from more extensive hydrothermal alteration in co3 4 3 7 chondrites that converted primary melilite into ca pyroxene andradite and nepheline alteration probably caused the preferential occurrence of o 16 poor oxygen isotopes in the more metamorphosed whole rock samples

quantitative subsidence uplift analysis of the bajo segura basin eastern betic cordillera spain tectonic control on the stratigraphic architecture the bajo segura basin is located in the eastern betic cordillera at present connected with the mediterranean sea to the east it has a complete stratigraphic record from the tortonian to the quaternary which has been separated into six units bounded by unconformities this paper is concerned with the northern edge of the basin controlled by a major strike slip fault the crevillente fault zone cfz where the most complete stratigraphic successions are found the results obtained summarised below are based on an integrated analysis of the sedimentary evolution and the subsidence uplift movements unit i early tortonian is transgressive on the basin basement and is represented by ramp type platform facies organised in a shallowingupward sequence related to tectonic uplift during the first stages of movement along the cfz unit ii lower late tortonian consists of shallow platform facies at bottom and pelagic basin facies at top forming a deepening upward sequence associated with tectonic subsidence due to sinistral motion along the cfz unit iii middle late tortonian is made up of exotic turbiditic facies related to a stage of uplift and erosion of the southern edge of the basin unit iv upper late tortonian consists of pelagic basin facies at bottom and shallow platform facies at top defining a shallowing upward sequence related to tectonic uplift during continued sinistral movement on the basin bounding fault units v latest tortonian messinian and vi pliocene pleistocene p p consist of shallowing upward sequences deposited during folding and uplift of the northern margin of the basin no definitive evidence of any major eustatic sea level fall associated with the messinian salinity crisis has been recorded in the stratigraphic sections studied q 2001 elsevier science b v all rights reserved

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

foraminiferal record of environmental changes messinian of the los yesos area sorbas basin se spain the late messinian of the sorbas basin betic cordillera se spain has been sampled to estimate 1 the paleoenvironmental changes recorded by the benthic foraminifers in pre evaporitic and evaporitic units and 2 the impact of the messinian salinity crisis on the foraminiferal biodiversity in the pre evaporitic unit foraminifers indicate a circalittoral to bathyal environments and show significant changes in bottom water oxygenation simultaneously the occurrences of epiphytic damaged foraminifers and the blocks of porites point out the presence of plant substrates and coral reefs on the infralittoral zone the overlying evaporitic unit is characterized by four subaqeous selenitic gypsum layers and three marine fossiliferous intercalations each episode of gypsum deposition ends with a desiccation event each fossiliferous intercalations traduce a rapid reflooding of the basin by marine waters corresponding to infralittoral to upper bathyal environments with normal marine conditions during the evaporitic period the ecological conditions in the water column were intermittently favorable to the development of marine organisms and moreover the marginal basins of the betic cordillera were not continuously desiccated during the messinian the low percentage of extinct species 5 at the messinian pliocene boundary and the occurrences of benthic foraminifers in the evaporitic unit indicate that the infralittoral to upper bathyal environments have not been completely modified and or barren during the messinian salinity crisis i e the messinian salinity crisis is not associated with a biological crisis

sedimentary basin destruction inferred from the evolution of drainage systems in the betic cordillera southern spain the guadix continental basin developed during the uppermost miocene the pliocene and the pleistocene one axial fluvial system and two transverse systems are interpreted in its alluvial infill in addition there are areas of lacustrine sedimentation permanent in the eastern sector and ephemeral in the western part of the basin from a sedimentological point of view the holocene drainage network shows significant similarities with that which occupied the ancient basin although there are some differences in location these provide information about the processes involved in the transformation of the sedimentary basin into an erosional basin with external drainage most of the data seem to indicate that the capture of drainage from the guadix basin by the guadalquivir river was accelerated principally by tectonic processes related to a recent uplift of a sector of the betic cordillera together with the disappearance of subsident points of the basin the high rate of holocene erosion is partially conditioned by the type of sediment deposited in the basin a low degree of lithification textural heterogeneity etc in comparison with the basement and mainly by the position of the ancient basin in relation to the new relative base level located almost 500 m lower than the position actually occupied by the pleistocene relative base level of the basin

environmental conditions vs landscape assessment of the factors that influence small mammal fauna distribution in southern iberia during the latest messinian by mean of stable isotopes tropical conditions during the late miocene in southwestern europe influenced the continental environments although there are previous qualitative environmental interpretations of these continental landscapes during the late miocene quantitative environmental and paleohydrological data are scarce a very long sequence of small mammals allowed to date the different continental drainage stages of the granada basin from latest tortonian to the holocene and to reconstruct qualitatively its environmental evolution the study of the isotopic record of these fossil small mammals and sediments in the stratigraphic sequence of a latest messinian paleo lake in the granada basin has provided quantitative environmental and paleohydrological data in order to know if the fluctuations in the faunal distribution were mainly influenced by the paleogeographic configuration such as changes in the landscape of the basin or by the climatic conditions open habitats with c3 plants predominated estimated quantitative data suggest an oxygen isotopic composition of meteoric waters ranging from 4 9 to 3 9 past temperatures from 2 5 c to 4 7 c higher than the current ones and summer relative paleohumidity from 60 to 70 in this context changes in the landscape such as the reduction of the lacustrine system caused by tectonic activity would affect taxa with high dependence on humid conditions

salt deposition and brine evolution in the granada basin late tortonian se spain abstract a group of sedimentary basins in the betic chain were formed during the middle late miocene as a result of the closure of the tethys during the alpine orogeny in the late miocene tortonian messinian the connections between the atlantic ocean and mediterranean sea were interrupted and those basins hosted major evaporites the granada basin an inner basin located far from the mediterranean contains a thick rock salt deposited during the latest tortonian in the transition from marine to non marine conditions in the centre of the basin three halite bearing units overlie a basal anhydrite bed the lower halite unit the intermediate sandstone unit and the upper halite unit fluid inclusion compositions and bromine concentrations in halite together with stable isotopes 34 s sulfate 18 o sulfate and 87 sr 86 sr indicate a mixture of different inflow waters in the granada basin beginning with a marine lagoon that evolved into a salt pan strongly isolated from the sea saline waters evolved from sulfate rich marine derived to sulfate depleted non marine brines influenced by the addition of cacl 2 rich inputs these cacl 2 rich waters were probably linked to thermal fluids associated with a major crustal fracture system crevillente or cadiz alicante fault system that cuts through the granada basin

the blue angel i the mineralogy and petrogenesis of a hibonite inclusion from the murchison meteorite a detailed mineralogie chemical and petrologic study of the blue angel a relatively large 1 5 mm hibonite containing inclusion from the murchison meteorite was performed in an attempt to understand the mechanisms of formation and modification of hibonite rich inclusions the blue angel inclusion is composed of roughly equal amounts of hibonite and calcite with minor amounts of spinel perovskite diopside and an fe rich silicate the inclusion can be divided into three roughly concentric zones a hibonite rich core a calcite rich mantle and a spinel rich layered rim the mineral chemistry and petrography of the blue angel are consistent with a three stage formation history 1 an early stage of nebular condensation which produced the hibonite perovskite and spinel 2 a moderate temperature stage of aqueous alteration and metamorphism occurring on a small planetary body containing co 2 and h 2o during which calcite was formed in the inclusion and 3 the final emplacement of the blue angel into its present position in murchison the study of the blue angel indicates that extensive alteration of ca al rich inclusions cai may have occurred by aqueous alteration and thermal metamorphism followed by explosive mixing processes on a parent body such metamorphic reactions may involve formation and destruction of phases such as melilite and diopside which have been previously thought to be primary condensates the mechanisms proposed for the formation and modification of the blue angel help to explain the secondary phases and oxygen isotope anomalies found in many cai and eliminate the need for invoking kinetically complicated back reactions at very low pressures with a cool part of the solar nebula the contribution of planetary metamorphism in the formation and alteration of cai must be considered along with nebular processes in order to understand the formation of carbonaceous chondrites

long term control mechanisms of stream piracy processes in southeast spain the guadix basin developed as an endorheic depression during the upper miocene upper pleistocene its principal palaeogeographical characteristics are a large lake in the eastern sector an axial fluvial system and two fluvial systems transverse to it in the western sector the uplift of a central sector of the betic cordillera during the upper pleistocene affected the study area causing northward tilting from the internal zone of the cordillera sierra nevada and sierra de baza step faulting of the plio pleistocene infill of the ancient basin leaving more northern sectors in a lower topographical position alteration of fluvial current profiles and displacement of the ancient axial system to a position very close to the divide between the ancient endorheic guadix basin and the guadalquivir basin this facilitated capture of the endorheic basin by the headward erosion of a tributary of the guadalquivir river the region then began to be rapidly eroded as the new base level was now some 500 m lower than that of the ancient basin the present drainage network is similar to that of the ancient endorheic basin as regards the location of the main streams and the distribution of drainage patterns and fluvial styles although flow reversal is found in some stretches and a barbed drainage pattern appears locally as a result of the inheritance of drainage from the ancient basin fluvial superimposition is found in some stretches of the main streams 1997 by john wiley sons ltd

the challenge of dating early pleistocene fossil teeth by the combined uranium series electron spin resonance method the venta micena palaeontological site orce spain the palaeontological site of venta micena orce andalusia spain lies in the eastern sector of the guadix baza basin one of the best documented areas in europe for plio pleistocene biostratigraphy the combination of biochronological and palaeomagnetic results combined with the radiometric data obtained for atapuerca sima del elefante indicated that the venta micena stratum was formed between the jaramillo and olduvai palaeomagnetic events most likely between 1 22 and 1 77 ma five fossil teeth from two outcrops sites a and b were selected to assess the potential of combined uranium series electron spin resonance us esr dating of early pleistocene sites although the us esr results of the first outcrop showed a large scatter between the three teeth the mean age of 1 37 0 24 ma can be considered a reasonable age estimate for venta micena the mean esr age of 0 62 0 03 ma obtained for site b seems to be a severe underestimation when compared with the independent age control this underestimation is attributed to a relative recent u mobilization event that led to some u leaching the results show that any esr age calculations of old samples are extremely sensitive to variations in the measured 230th 234u ratios in dental tissues although the results demonstrate that esr can in principle be applied to early pleistocene sites they also reveal the complexity of dating such old teeth it is necessary to continue research in several directions such as study of the behaviour of esr signals in old teeth and understanding recent u mobilization processes to improve the reliability of the combined us esr dating method applied to early pleistocene times a period for which the number of available numerical dating techniques is very limited copyright 2011 john wiley sons ltd

evolution of the late miocene mediterranean atlantic gateways and their impact on regional and global environmental change marine gateways play a critical role in the exchange of water heat salt and nutrients between oceans and seas as a result changes in gateway geometry can significantly alter both the pattern of global ocean circulation and associated heat transport and climate as well as having a profound impact on local environmental conditions mediterranean atlantic marine corridors that pre date the modern gibraltar strait closed during the late miocene and are now exposed on land in northern morocco and southern spain the restriction and closure of these miocene connections resulted in extreme salinity fluctuations in the mediterranean leading to the precipitation of thick evaporites this event is known as the messinian salinity crisis msc the evolution and closure of the mediterranean atlantic gateways are a critical control on the msc but at present the location geometry and age of these gateways are still highly controversial as is the impact of changing mediterranean outflow on northern hemisphere circulation here we present a comprehensive overview of the evolution of the late miocene gateways and the nature of mediterranean atlantic exchange as deduced from published studies focussed both on the sediments preserved within the fossil corridors and inferences that can be derived from data in the adjacent basins we also consider the possible impact of evolving exchange on both the mediterranean and global climate and highlight the main enduring challenges for reconstructing past mediterranean atlantic exchange

identification of leakage and potential areas for internal erosion combining ert and ip techniques at the negratin dam left abutment granada southern spain abstract at the negratin dam southern spain two main springs derived from the water reservoir were detected on the west side of the mountain ridge matching the location of the left abutment of the dam the seepages appear when the level of the stored water exceeds 622 m above sea level m a s l where some paleochannels are embedded in the silts the water level was at 631 m a s l on the day of the measurements 13 12 23 close to the historical maximum 633 78 m a s l although the water crossing the leaks does not drag particles nowadays this sector may potentially cause internal erosion or piping phenomena implying a loss of water resources and slope instability problems the infiltration areas were evaluated by electrical resistivity and induced polarization methods measured along one profile on the mountain ridge between the water reservoir and the springs we determine that the infiltrations zones are characterized by low resistivity and high chargeability distributed in small areas we demonstrate that these methods are a reliable tool to detect and characterize infiltration zones and they are the first step to planning mitigation actions to avoid the piping phenomena

aqueous alteration of chondrules in the cm carbonaceous chondrite allan hills 81002 implications for parent body alteration abstract alh 81002 is a cm carbonaceous chondrite that has petrographic characteristics suggesting that it experienced a high degree of aqueous alteration but has entirely escaped parent body brecciation in this study we report the results of a systematic investigation of the alteration of more than 35 chondrules in alh 81002 that belong to specific well defined chondrule types our results show that the extent of chondrule alteration is almost exclusively controlled by the properties of the chondrule phases although these chondrules taken as a group show highly variable degrees of alteration no evidence for differences in the alteration histories of chondrules has been found instead the widely varying rates of alteration of chondrule phases such as forsteritic and fayalitic olivine clinoenstatite orthopyroxene and augite are sufficient to explain the diversity of chondrule alteration in alh 81002 chondrules with similar primary textural and mineralogical characteristics e g type ia type iia etc show remarkably similar degrees of alteration detailed studies of the alteration products of chondrules show that they retain a detailed record of the alteration history of the chondrules from the earliest to last stages and provide strong evidence for the compositional evolution of the altering fluid contrary to what might be expected the fluid composition appears to be the dominant controlling factor on the composition of serpentines that replace olivines pyroxenes and mesostasis the consistent degree of alteration observed in chondrules of the same type in alh 81002 indicates that they were altered under the same conditions for similar lengths of time such conditions are most consistent with alteration in a parent body environment in addition the compositional and textural uniformity of rim material chondrule alteration phases and vein fillings in chondrule components throughout alh 81002 also argue strongly that alteration occurred after accretion several observations on alh 81002 provide additional constraints and modifications on existing models of in situ parent body alteration for example inferences on the degree of alteration of cm chondrites based on the extent of brecciation as a parameter of the alteration degree appear to be compromised in addition models which suggest that tochilinite serpentine pcp rich objects have resulted from the break up of chondrules during brecciation are also inconsistent with our observations on alh 81002

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

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

paleoenvironmental evolution of the eastern mediterranean during the messinian constraints from integrated microfossil data of the pissouri basin cyprus abstract integrated data of calcareous nannofossils as well as planktonic and benthic foraminifera from the pissouri motorway section on cyprus allow the reconstruction of surface and bottom water paleoenvironments of the eastern mediterranean during the interval preceding the messinian salinity crisis msc contrary to deeper water locations where benthic foraminifera faunas are suppressed or absent just after the tortonian messinian boundary sediments deposited at intermediate water depths do contain benthic assemblages from the earliest messinian onwards a development towards increasingly unfavourable paleoenvironments is reflected in the planktonic and benthic microfossil records of the pissouri section and proceeds with rather discrete time steps that can be correlated to sequences throughout the mediterranean shortly after the tortonian messinian boundary a transition is recorded in the sedimentology and the open marine deeper water taxa disappear from the benthic foraminifera assemblages subsequently the diversity of all fauna groups diminishes the changes recorded at species level in both surface water and sea floor dwelling taxa suggest decreasing circulation of the bottom waters associated with changes in the surface waters most likely due to increasing stratification from 6 73 ma onwards our data indicate a prominent change to more restricted conditions and increasing salinity at the sea floor together with intermittently rising surface water salinity the dominance of oligotypic and monospecific assemblages and the frequent shifts in assemblage compositions of all microfossil groups indicate severely stressed environments after 6 4 ma probably related to increased salinity the major changes in paleoenvironmental conditions including oxygen deprivation due to stagnation and hypersalinity can be explained by hydrographical changes in the mediterranean basin which are probably caused by tectonic movements in the rif corridor acting in concert with astronomical cyclicity evaluation of the paleodepth proxies indicates that the depth of the pissouri basin remained rather constant at 300 500 m with a minimum of 200 m until deposition of the barre jaune the transitional interval towards the evaporites and that early shallowing to neritic depths as was proposed before is highly unlikely

hydrothermal activity and its paleoecological implications in the latest miocene to middle pleistocene lacustrine environments of the baza basin betic cordillera se spain the continental sedimentary record of the baza basin guadix baza depression betic cordillera se spain shows six sedimentary units of lacustrine origin deposited from the latest miocene to the middle pleistocene depending on the interval considered the lacustrine deposits are mainly composed of marls carbonates or gypsiferous evaporites showing lithological mineralogical and geochemical features i e magnesium strontium and sulfur contents celestine deposits and travertine growths that are evidence of intense tectonically induced hydrothermal activity according to the high concentrations of strontium and sulfur as well as the abundance of travertines and magnesium clays the supply of hot waters was greater during the zanclean the gelasian and the calabrian as a result of tectonic activity hydrothermal activity has continued until the present time and is responsible of the hot springs that are nowadays active in the guadix baza depression the paleoenvironmental consequences of these sublacustrine hot springs were that during some intervals the lakes maintained a relatively permanent water table not subject to periodic desiccations in the dry season and warmer temperatures throughout the year this resulted in a high level of organic productivity especially for the calabrian which allowed the development of a rich and well diversified mammalian community similar to those of modern african savannas with tree patches in this mild environment the permanent water sheet favored the presence of drought intolerant megaherbivores such as the giant extinct hippo hippopotamus antiquus the high standing crop biomass of ungulates resulted in the availability of abundant carcasses for scavengers such as hyenas and hominins which explains the very high densities of skeletal remains preserved in the sediments distributed along the lake surroundings

fluffy type a ca al rich inclusions in the allende meteorite abstract allende fluffy type a s fta s are a distinct sub group of ca al rich inclusions whose primary mineral assemblage consists of al rich melilite ak 0 33 spinel that is commonly very v rich perovskite and frequently hibonite some contain relatively coarse grained melilite up to 1 5 mm that is intensely kink banded and commonly reversely zoned hibonite and v rich spinel others contain much finer grained and strain free melilite 50 m and have not been found to contain hibonite or v rich spinel some fta s contain both coarser and finer grained melilite and textural relationships indicate that the latter is replacing the former fta s are characterized by extremely irregular shapes and 60 75 volume per cent of fine grained secondary alteration products many are aggregates of innumerable nodules each of which is surrounded by a wark lovering type rim sequence these nodules are frequently separated from one another by matrix like clastic rim material other fta s do not have nodular structure structural and mineralogical characteristics of their wark lovering rims suggest that fta s did not achieve their shapes by deformation of a liquid or a hot plastic solid in contrast to those in type b inclusions formation of reverse zoning in the coarser grained melilite crystals in fta s cannot be understood in terms of crystallization from a liquid but are readily explainable by condensation from a solar nebular gas during a period of falling pressure further evidence against a liquid origin is the wide range of spinel compositions within individual coarser grained fta s the fact that the reversely zoned melilite crystals cannot have been produced in any kind of sublimation or distillation process precludes formation of these inclusions as volatilization residues fta s are aggregates in some of which are preserved vapor solid condensate grains that formed at high temperature in the solar nebula

climatic control on palaeohydrology and cyclical sediment distribution in the plio quaternary deposits of the guadix basin betic cordillera spain abstract a cyclical pattern can be observed in the central sector of the guadix basin southern spain in the late pliocene quaternary alluvial fan deposits prograding into its axial valley a climatic significance has been attributed to this cyclicity on the basis of sedimentological and preliminary isotopic studies the progradation phases of the alluvial fans are here attributed to more arid time intervals in which the vegetation cover would be less developed erosion and sediment supply would be higher and base level would be lower in contrast the time intervals during which the fluvial system sediments dominated the area are inferred to be wetter and base level higher with vegetation cover retaining the soils and preventing erosion permanent water supply to the river would therefore facilitate the aggradation of the floodplain and prevent progradation of the fans starting from a litho bio and magnetostratigraphical frame provided for the area an age is assigned to the alternation of the reddish sediments of the transverse alluvial fans and the greyish to white fluvio lacustrine sediments of the axial drainage system a cyclicity of ca 100 ky has been identified in most of the alluvial fan progradation phases falling within milankovitch high frequency eccentricity periodicities correlation of the phases with insolation curves is accordingly discussed as a possible origin for the cyclicity finally the results offer new insights into early hominin occupation patterns in the region through the identification of predictable resources of permanent fresh water that would have remained available throughout the recorded time span that includes the early middle pleistocene transition even during times of aridification

high frequency rhythmicity in a mixed siliciclastic carbonate shelf late miocene guadix basin spain a model of interplay between climatic oscillations subsidence and sediment dispersal abstract rhythmites in pelagic sediments can include information on paleoclimate and with orbital cycles this paper documents and interprets an unusual rhythmic succession from a cool water shallow marine shelf that includes features of mediterranean type ramps and open ocean type ramps in the subsiding southwestern margin of the guadix basin southern spain betic cordillera during the late tortonian a 640 m thick succession was deposited over a short period 7 8 7 2 ma this succession contains 30 sedimentary packages or rhythmites each defined by two facies associations a mixed cross stratified siliciclastic skeletal sandstone and a homogeneous marl rich in planktonic foraminifera sandstones ranging in thickness from 3 m to 20 m contain coralline algae bivalves bryozoans benthic foraminifera echinoids and brachiopods typical temperate water shelf biofacies these units exhibit cross strata sets up to four meters high interpreted to have been produced by strong unidirectional currents the marly deposits range in thickness from 2 to 17 m and contain an association of cold water planktonic foraminifera as well as thin sandstone layers that exhibit normal grading corresponding to typical incomplete bouma sequences or a lower division with planar lamination and an upper division of very fine to fine grained sandstone with hummocky and swaly cross stratification on the basis of the sedimentary structures the sandstone layers are interpreted as sporadic turbidity flows and storm ebb surge deposits on the basis of the sedimentary structures the hydrodynamic conditions during deposition of the mixed siliciclastic carbonate interval were high energy based on sedimentary and biogenic features of the rhythmites and their temporal durations ca 20 ka rhythmicity is interpreted to reflect alternating cool wet and cold dry climate episodes driven by precession orbital cycles this occurrence of alternating mixed carbonate siliciclastic sedimentation and pelagic sediments represents a unique occurrence in the geologic record

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

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

on the late miocene closure of the mediterranean atlantic gateway through the guadix basin southern spain abstract the late miocene mediterranean atlantic connection through southern spain is generally thought to have closed during the late tortonian but accurate constraints on palaeobathymetry shallowing rates and closure age are still lacking we present integrated biostratigraphic planktonic benthonic foraminifera and mammals and magnetostratigraphic results from the marine to continental la lancha section of the guadix basin refining the chronology for the miocene pliocene sedimentary sequences of this basin that occupied a central position in the marine gateway in addition we perform palaeobathymetric analyses on the marine sedimentary sequence to reconstruct sea level fluctuations and vertical motions deposition of the lower marine unit took place between 8 1 and 7 85 ma with accumulation rates of 1 m kyr a rapid shallowing from palaeodepths of 500 300 m to a depth of 300 200 m took place at 8 0 ma coinciding with a decrease in downslope transport surprisingly no shallowing trend has been observed towards the unconformable contact with the transitional unit which was deposited in a shallow 90 m marine environment the youngest open marine marls are still indicative for a palaeodepth of 200 m this leads to the conclusion that fully marine environments in guadix persisted until at least 7 85 ma the palaeomagnetic polarity pattern of the upper continental unit in combination with the presence of the murid paraethomys meini in the basal part of this sequence indicates that the entire continental unit at la lancha is attributed to the latest messinian zanclean time this age is in strong contradiction with previous correlations to the late tortonian consequently we conclude that a major hiatus of at least 2 myr comprising most of the messinian stage is present in the guadix basin therefore a late tortonian closure age of the mediterranean atlantic gateway through guadix has not been confirmed by our results so that the possibility of a messinian gateway through southern spain cannot be completely ruled out

autogenic dynamics of alluvial fans in endorheic basins outcrop examples and stratigraphic significance alluvial fans are relatively simple depositional systems due to the direct coupling of sediment sources and adjacent accumulation areas nonetheless general models of alluvial fan evolution and stratigraphy remain elusive due to the great sensitivity of such systems to allogenic controls and their strongly case specific responses autogenic processes intrinsic to alluvial fan dynamics can complicate stratigraphic architectures with effects not easily distinguishable from those of allogenic forcing a distinction is made here between lateral autogenic dynamics tied to spatial sediment distribution over fan surfaces and vertical autogenic dynamics related to independent incision aggradation cycles autogenic mechanisms have been highlighted recently by modelling studies but remain poorly constrained in field based studies examples are presented here from the margins of the cenozoic teruel and ebro basins spain where alluvial fans accumulated thick successions during phases of basin topographic closure and endorheic drainage which promoted forced aggradation fan successions consist of conformable architectures of stacked clastic sheets laterally continuous and with no evidence of internal unconformities inset architectures fan segmentation or preserved incised channels continuous aggradation in these closed basins strongly inhibited vertical autogenic dynamics in the form of fan head and through fan incision due to the forced rise in geomorphic base level and the creation of positive accommodation furthermore the lack of incised channels favoured widespread sediment transport and aggradation over broad fan sectors in relatively short time spans in contrast to the typical occurrence of active lobes and abandoned fan surfaces caused by lateral autogenic dynamics stratigraphic records of alluvial fans developed in endorheic basins are essentially complete and largely unaffected by autogenic processes the latter characteristic implies that they can be more unambiguously interpreted in terms of allogenic forcing because stratigraphic signatures are not complicated by the effects of complex fan autodynamics

major controls on sedimentation during the evolution of a continental basin pliocene pleistocene of the guadix basin betic cordillera southern spain abstract sequence stratigraphy based on climatic tectonic and base level parameters can be used to understand carbonate sedimentation in continental basins the uppermost continental fill of the guadix basin betic cordillera containing both siliciclastics and carbonates is investigated here in its central sector a thick succession of fluvio lacustrine sediments appear hosting several important pliocene and pleistocene macrovertebrate sites fonelas project the need to characterize the stratigraphic and sedimentologic context of these important paleontologic sites has lead to litho magneto and biostratigraphic studies these data together with the sedimentologic analysis of the pliocene and pleistocene siliciclastic and carbonate successions establish a sedimentary model for the fluvio lacustrine sedimentation of the two last stages of sedimentation in the guadix basin units v and vi unit v comprises mostly fluvial siliciclastic sediments with less abundant carbonate beds interpreted as floodplain lakes or ponds the latter unit vi is dominated by vertically stacked carbonate palustrine successions using two pre existent continental stratigraphic models the influence of climate tectonism and stratigraphic base level during the last 3 5 ma on the sedimentary evolution of the fluvio lacustrine system in the guadix basin especially the carbonate sedimentation patterns is outlined

architecture and tectono stratigraphic evolution of the intramontane baza basin betics se spain constraints from seismic imaging abstract the baza basin is a large neogene intramontane basin in the betic cordillera of southern spain that formed during the tortonian late miocene the betic cordillera was produced by nw se oblique convergence between the eurasian and african plates three seismic reflection lines each 18 km long vibroseis method were acquired across the baza basin to reveal the architecture of the sedimentary infill and faulting during basin formation we applied rather conventional cdp data processing followed by first arrival p wave tomography to provide complementary structural information and establish velocity models for the post stack migration these images show a highly asymmetric structure for the basin with sediments thickening westward reaching a maximum observed thickness of 2200 m near the governing baza fault zone bfz three major seismic units including several subunits on top of the acoustic basement could be identified we use stratigraphic information from the uplifted block of the bfz and other outcrops at the basin edges together with available information from neighboring betic basins to tentatively correlate the seismic units to the known stratigraphy in the area until new drilling or surface outcrop data is not available this interpretation is preliminary the seismic units could be associated to tortonian marine deposits and latest miocene to pleistocene continental fluvio lacustrine sediments individual strands of the bfz truncate the basin sediments strong fault reflections imaged in two lines are the product of the large impedance contrast between sedimentary fill and basement in the central part of the basin several basement faults document strong deformation related to the early stages of basin formation some of these faults can be traced up to the shallowest imaged depth levels indicating activity until recent times

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

the late miocene mediterranean atlantic connections through the north rifian corridor new insights from the boudinar and arbaa taourirt basins northeastern rif morocco new data from the neogene boudinar and arbaa taourirt basins northeastern morocco provide constraints on the late miocene evolution of the north rifian corridor the chronostratigraphy of these basins is clarified on the basis of biostratigraphic planktonic foraminifers calcareous nannoplankton and radio isotope ages marine sedimentation in the boudinar basin began during the early tortonian at 10 ma and persisted until the late early messinian at 6 1 ma in the arbaa taourirt basin it occurred between the late tortonian and the earliest messinian paleoenvironmental data benthic foraminifera and pollen grains record a major drowning in association with extensive tectonism in the boudinar basin during the early messinian 7 2 ma synchronously there was a major sedimentological change in the arbaa taourirt basin with progradation of conglomerates and sandstones over late tortonian marls large scale cross bedded sandstones indicate paleo currents flowing from the atlantic ocean toward the mediterranean sea during the late early messinian a shallowing trend occurred culminating with the progradation of reefal carbonates our findings indicate that the north rifian corridor opened at 7 2 ma ensuring atlantic mediterranean connections the corridor was progressively restricted during the late early messinian with complete closure by 6 1 ma the results of this study thus question existing hypotheses for the timing and nature of atlantic mediterranean connections during the late messinian

late miocene paleoenvironmental changes in north africa and the mediterranean recorded by geochemical proxies monte gibliscemi section sicily abstract the astronomically tuned marls of the monte gibliscemi section sicily constitute an archive to trace the late miocene palaeoenvironmental conditions 9 7 7 0 ma in north africa here we have utilised carbonate content and al normalised geochemical proxies to trace changes in terrigenous source area and bottom water ventilation the terrigenous input into the section is dominated by north african river systems draining into the eastern mediterranean the proxy parameters indicate that the palaeoenvironmental conditions in north africa were humid from 9 5 ma onward with high fluvial input to the mediterranean increases in the si al and mg al ratios occurred from 8 4 to 8 2 ma and from 8 05 to 7 75 ma with maximum values similar to those of messinian diatomites these peaks indicate conditions of enhanced biosiliceous productivity and the presence of authigenic clay formation sluggish water circulation in the mediterranean during those times is inferred from the mn al and v al behaviour late miocene changes of the betic southern spain and rifian morocco mediterranean atlantic gateways are interpreted as the driving force for the changes in water circulation and the transgression associated with the opening of the rifian corridor is interpreted to occur at 7 8 ma

evidence for an african iberian mammal dispersal during the pre evaporitic messinian the accurate timing of biogeographic dispersal can be determined by examining the age of fossiliferous strata on either side of a physical barrier here we show that african mammals migrated to iberia and european mammals migrated to north africa at the same time before isolation of the mediterranean sea during the messinian the fossil site of venta del moro spain exhibits western europe s most complete vertebrate fauna for the latest miocene its uniquely cosmopolitan assemblage is evidence of faunal dispersals from africa and asia to europe during the latest miocene glaciation a preliminary paleomagnetic study suggested an age of 5 8 ma for this site but our expanded magnetostratigraphy dates the site at 6 23 ma in addition we recalibrated the paleomagnetic age of the librilla site spain and the north africa site of afoud 1 morocco using the astronomical tuned neogene time scale our results show a two way african iberian mammal dispersal just before 6 2 ma these new ages indicate that an ephemeral land corridor existed between the two continents 250 k y before the onset of the messinian salinity crisis reflecting a tentative initial isolation of the mediterranean sea this corridor developed after tectonics closed the betic seaway at 6 3 ma and during the intensification of the latest miocene glaciation at 6 26 ma when water circulation in the mediterranean became very restricted

origin of spinel rich chondrules and inclusions in carbonaceous and ordinary chondrites our evaluation of three models of the origin of spinel rich chondrules and inclusions includes new calculations of the major element refractory mineral condensation sequence from a gas of solar composition over a wide pressure interval our condensation calculations show that spinel rich chondrules did not crystallize from metastable liquid condensates and that spinel rich inclusions are not aggregates of refractory nebular condensates we propose that spinel rich objects are fractionated distillation residues of small aggregates of primitive dust that lost ca si rich partial melts by evaporation ablation or splashing during collisions this model also explains why spinel rich chondrules and inclusions 1 are usually smaller than melilite rich chondrules and inclusions 2 often have highly fractionated trace element compositions and 3 usually do not contain pt metal nuggets even when they are more enriched in the pt group metals than nugget bearing melilite rich objects

a high resolution coupled riverine flow tide wind wind wave and storm surge model for southern louisiana and mississippi part i model development and validation abstract a coupled system of wind wind wave and coastal circulation models has been implemented for southern louisiana and mississippi to simulate riverine flows tides wind waves and hurricane storm surge in the region the system combines the noaa hurricane research division wind analysis system h wind and the interactive objective kinematic analysis ioka kinematic wind analyses the wave model wam offshore and steady state irregular wave stwave nearshore wind wave models and the advanced circulation adcirc basin to channel scale unstructured grid circulation model the system emphasizes a high resolution down to 50 m representation of the geometry bathymetry and topography nonlinear coupling of all processes including wind wave radiation stress induced set up and objective specification of frictional parameters based on land cover databases and commonly used parameters riverine flows and tides are validated for no storm conditions while winds wind waves hydrographs and high wa

early middle miocene stratigraphic turning points in the alicante region se spain reflections of western mediterranean plate tectonic reorganizations abstract the paper concerns the miocene deposits of the alicante region se spain which forms part of the prebetic and intermediate units representing the former southern passive margin of the iberian continent from the late jurassic up to the miocene the alicante region was the scene of a facies distribution with more continental lagoonal or shallow marine conditions in the north and northwest and more open or deeper marine in the south and southeast the early middle miocene deposits can be divided in three sedimentary cycles each one controlled by a different tectonic regime cycle i aquitanian is deposits after a block faulting phase at about 25 ma related to the formation of the ligurian and balearic troughs cycle ii burdigalian early langhian is separated from first cycle sediments by a complete reorientation of palaeogeography at 19 5 ma due to the collision of iberia with africa the southern part of the region is folded and uplifted and separated from a northern emerged area by a trough cycle iii late langhian serravallian is controlled by strike slip movements caused by the continuing convergence between africa and europe and resulting in the development of a new set of basins at 15 5 ma at the middle late miocene boundary the alicante region emerges thus younger important tectonics could not be dated our results are in conflict with several recent plate tectonic models for the miocene history of the western mediterranean where the internal betic zone is placed juxtaposed to the alicante region prior to the burdigalian

petrography of refractory inclusions in cm2 6 que 97990 and the origin of melilite free spinel inclusions in cm chondrites queen alexandra range que 97990 cm2 6 is among the least altered cm chondrites known it contains 1 8 vol refractory inclusions 40 were studied from a single thin section inclusion varieties include simple banded and nodular structures as well as simple and complex distended objects the inclusions range in mean size from 30 to 530 m and average 130 90 m many inclusions contain 25 15 vol phyllosilicate predominantly mg fe serpentine several contain small grains of perovskite in addition to phyllosilicate the most abundant inclusions in que 97990 consist mainly of spinel pyroxene 35 followed by spinel 20 spinel pyroxene olivine 18 pyroxene 12 pyroxene olivine 8 and hibonite spinel 8 four pyroxene phases occur diopside al rich diopside with 8 0 wt al2o3 al ti diopside i e fassaite and in two inclusions enstatite no inclusions contain melilite aqueous alteration of refractory inclusions transforms some phases particularly melilite into phyllosilicate some inclusions broke apart during alteration melilite free phyllosilicate bearing spinel inclusions probably formed from pristine phyllosilicate free inclusions containing both melilite and spinel sixty five percent of the refractory inclusions in que 97990 appear to be largely intact the major exception is the group of spinel inclusions all of which are fragments whereas que 97990 contains about 50 largely intact refractory inclusions cm2 estimates from literature data imply that more altered cm chondrites have lower modal abundances and lower number densities of refractory inclusions mighei cm 2 3 contains roughly 0 3 0 6 vol inclusions 10 largely intact inclusions cm2 cold bokkeveld cm2 2 contains 0 01 vol inclusions on the order of 6 largely intact inclusions cm 2

geology and chronology of the continental pleistocene archeological and paleontological sites of the orce area baza basin spain abstract the guadix baza basin hosts a continuous continental record of paleoenvironmental paleobiological and geological changes from around 8 ma to 205 ka a remarkable succession of pleistocene mammal sites is found in the lower and upper members of the baza formation in the orce area the upper member contains the early pleistocene paleontological and archeological sites of barranco leon 5 and fuente nueva 3 both sites belong to the early pleistocene zone defined by allophaiomys aff lavocati and a small mimomys savini this zone can be correlated with that of central europe containing mimomys savini and microtus praehintoni these sites are located in the marginal lacustrine deposits of the baza lake system and originated in expanded phases of the main lake when meteoric surface and shallow groundwater inputs were predominant the barranco leon 5 site is related to a sudden event of high energy currents entering a lacustrine palustrine domain these currents transported gravels bones and lithic industries from a short distance maximum hundreds of meters in contrast the diverse levels in fuente nueva 3 do not show evidence of noticeable transport by traction currents the age of the mammal succession and sites is based on magnetostratigraphy in the middle and upper members of the baza formation only reversed polarities are found matuyama epoch the location of the olduvai chron is still unclear and could have not been recorded due to the common hiatuses observed in the sedimentary successions in the lower member normal and reverse polarities gauss epoch are found in the galera and velez salar sections the later contains the site of fuente nueva 1 which is pre olduvai chron in age according to paleontological data and biostratigraphic correlation

geologic evolution of the betic cordilleras in the western mediterranean miocene to the present abstract the betic cordilleras were formed during the eo meso and neo alpine evolution of the western mediterranean area during the neo alpine stage the northward subduction of the african plate took place and the algerian provencal basin opened with the creation of oceanic floor associated space problems produced the expulsion and extensive stretching of the internal zones to the west which in turn disrupted and deformed the external zones of the betic and rif cordilleras these occurrences essentially took place in the burdigalian and continued with diminished intensity into the middle miocene following the suturing of the transcurrent contact between the internal and external zones important n60 90 e and nw se faults occurred the betic cordilleras are characterized as having been deformed by regional horizontal shortening compression oriented wnw ese or nw se which gradually rotated to the nnw sse in the late miocene when its most important intramontane neogene basins were formed the alboran basin with a thinned continental crust was formed as a western prolongation of the opening of the algerian provencal basin with its basic features already apparent in the burdigalian the volcanism present in the southeast of the betic cordilleras and in northeast morocco crossing the alboran basin is mainly late miocene in age it is linked to fracturing and exhibits chemistry related to the different thickness of the crust

water exchange through the betic and rifian corridors prior to the messinian salinity crisis a model study although the present day mediterranean atlantic water exchange has been extensively studied little is known about the dynamics of the betic and rifian corridors that existed before the messinian salinity crisis due to the difficulties in studying the paleogeographic evolution of these corridors physics based knowledge of their behavior is essential to interpret observational evidence and to relate flow structures to gateway geometries here we present the first systematic model study of the water exchange through these gateways we use the parallel version of the princeton ocean model sbpom and a set of idealized bathymetries based on a late tortonian paleogeography this analysis represents a major step forward in the understanding of the behavior of the double gateway system constituted by the late miocene betic and rifian corridors we demonstrate that the siphon scenario involving inflow of cold upwelled atlantic water through the rifian corridor and outflow of mediterranean water only via the betic corridor is unlikely from a physics perspective it is shown that two exchange patterns are possible depending solely on the relative depth of the corridors the implication of this is that geological evidence for the behavior of one corridor provides information about the dimensions of the other we show that disappearance of outflow in one corridor does not necessarily imply its closure and we establish a guideline to determine how geological evidence can be interpreted as indicating one or two layer flow based on the model results we propose new physics based scenarios for the time interval defined for the siphon

ages and stratigraphical architecture of late miocene deposits in the lorca basin betics se spain new insights for the salinity crisis in marginal basins unlike most neogene basins of the betic cordillera where the salinity crisis is dated to the messinian a contradictory tortonian dating was proposed for evaporites of the lorca basin as a consequence complex structural models have been proposed in the literature to explain this discrepancy in the timing of evaporites in order to integrate the lorca basin into the geological context of the western mediterranean domain during the late miocene new sedimentological and stratigraphical studies coupled with new dating were performed which allow us to propose a messinian age for both diatomite bearing deposits and evaporites of the lorca basin these new ages challenge the idea of a tortonian salinity crisis in the lorca basin three main events of base level drop were evidenced during the messinian each event is correlated with successive steps of basin restriction shallow salina evaporites were deposited after a base level fall during the messinian before a final base level drop which led to the entire exposure of the basin this last exposure is interpreted as coeval with the deposition of first evaporites and halite in the deep mediterranean basins the reflooding which allowed the deposition of brackish deposits and a short lived marine incursion occurred at the end of the messinian base level drops occurred during eustatic falls amplified by the gradual uplift of the betic cordillera the exhumation of the tercia ridge along the strike slip alhama de murcia fault system during the messinian probably favoured the gradual restriction of the basin a discussion on correlations of main unconformities between several neogene basins of the betics is proposed suggesting a similar structural evolution at the regional scale

refractory inclusions in the prototypical cm chondrite mighei abstract refractory inclusions in the mighei cm2 meteorite are very abundant 35 being found in three thin sections of the meteorite the most common are pyroxene rimmed spinel rich inclusions that occur in a range of structural and textural types some inclusions are simple aggregates of crystals or rimmed crystals ranging from loose clusters of spinel grains to distended chains of pyroxene rimmed spinel knots others are more compact and may have experienced recrystallization or melting these include nodular spinel inclusions with polygonal granular textured spinel interiors and pyroxene rims ribbons of spinel in some cases with hibonite and or perovskite that are again rimmed by pyroxene and refractory spherules four inclusions are complex aggregates of several texturally distinct objects each collectively mighei inclusions are similar to those in murchison but appear to be somewhat more altered volatility fractionated and unfractionated trace element patterns similar to those found in refractory inclusions in other carbonaceous chondrites are represented in mighei inclusions and in addition some mighei inclusions have volatility fractionated pattern types not previously found in refractory inclusions in three of the complex aggregates fundamentally different trace element patterns are present within different portions of each inclusion meaning that these objects accreted from genetically different components that never equilibrated with one another subsequent to accretion bulk inclusion magnesium isotopic compositions show minor mass fractionation effects fmg values range from 2 3 to 7 5 but the average fmg value is indistinguishable from normal 1 8 1 2 there are no correlations between magnesium isotopic composition and textural type or trace element pattern type the diverse inclusion types in mighei represent a variety of origins and histories textures suggest that the nodular and banded inclusions may have experienced solid state recrystallization whereas the porous and chain like varieties and complex aggregates have not magnesium isotopic compositions and trace element abundances suggest that the mighei inclusions are unlikely to be evaporation residues and are more likely to be the products of condensation or recondensation processes

late tortonian early messinian stepwise disruption of the mediterranean atlantic connections constraints from benthic foraminiferal and geochemical data abstract late miocene marine land based sections in the mediterranean area contain important information on the prelude to the messinian salinity crisis msc integrated bio magneto tephra and cyclo stratigraphy allows for bed to bed correlations of sections throughout the mediterranean and its borderlands and enables correlation with extra mediterranean atlantic sites benthic foraminiferal and geochemical data from five sections were compared to literature data and indicate that a restriction of the mediterranean from the atlantic ocean started during the late tortonian b the continuous development towards the msc started as early as 7 2 ma in the deeper parts of the basin and was enhanced by astronomical forcing and 3 the onset of the msc must have been to a large extent related to differential vertical movements at the betic and rifian corridors the miocene connections between the mediterranean and the atlantic