high frequency cyclicity in a vertical alternation of gilbert type deltas and carbonate bioconstructions in the late tortonian tabernas basin southern spain abstract the deltaic succession in the tabernas basin represents the first deposition of marine sediments deposited during the late tortonian transgression that linked the mediterranean sea to the atlantic ocean through the basins of the betic cordillera the 100 m thick succession consists of seven 5 to 20 m thick vertically stacked wave dominated gilbert type deltas towards the top of each unit coral reef patches overlie the delta plain and are in turn overlain by calcarenites formed by accumulation of branching red algae colonies locally the calcarenite deposits fill microkarst depressions developed on the reefal carbonates during emergence unlike the corals the red branching algae colonies grew at a few metres depth under low energy conditions below wave base the calcarenites derived from branching red algae colonies formed when the delta plain was drowned creating the new accommodation space needed for the progradation of the delta forming of the overlying unit the repeated alternation of coral reef carbonates tropical carbonates and carbonates with bryomol skeletal assemblages temperate carbonates in the deltaic succession is linked to relative sea level changes reflecting the sum of glacio eustatic sea level fluctuations and tectonic subsidence each delta unit is represented by a transgressive systems tract built by the stacking of distributary mouth bars capped by reef patches a maximum flooding surface represented by branching red algal calcarenites and a highstand systems tract consisting of progradational wave dominated gilbert type delta because of the general increase in accommodation space controlled by glacio eustatic sea level rise and tectonic subsidence beach topset strata and distributary mouth bars were preserved in the cases studied subsidence rates exceeded the glacio eustatic sea level lows preventing the development of normal lowstand systems tracts in the delta stack

was the black sea catastrophically flooded in the early holocene abstract a catastrophic flooding of the black sea basin was proposed to have occurred during its reconnection to the ocean in the early holocene possible cultural consequences of the flood include the migration of neolithic farmers from around the black sea towards central europe as well as the creation of flood myths stratigraphic and paleo geomorphologic information from danube delta aided by radiocarbon ages on articulated mollusks constrain the level in the black sea before the marine reconnection to ca 30 m below the present sea level rather than 80 m or lower if the flood occurred at all the sea level increase and the flooded area during the reconnection were significantly smaller than previously proposed

the summit erosion surfaces of the inner betic cordillera their value as tools for reconstructing the chronology of topographic growth in southern spain erosion surfaces at the top of mountain ranges have suggested to geomorphologists that the earth s crust can undergo rapid pulses of uplift during which rates of denudation fail to balance with rates of crustal uplift thereby preserving much of the initial plateau topography as it rises to greater elevations here we analyze a regionally extensive population of mappable planar surfaces which crown several major tectonically active sierras of the inner south eastern betic cordillera se spain based on a synthesis of long term landscape evolution involving landform reconnaissance dem based morphometric analysis structural geology sediment provenance analysis and field stratigraphy we conclude that the summit surfaces are a mosaic of discrete post orogenic erosion surfaces that each developed in relation to mediterranean marine base levels at a time when the sierras formed a series of low elevation islands they are not therefore fragments of a once regionally continuous paleoplain the summit surfaces were partly the result of shallow angle detachment faulting during the middle miocene in response to lithospheric slab detachment where evidence exists that the resulting low relief topography was reworked by marine abrasion during the tortonian sea level rise the terminal age of the surfaces is latest miocene age bracketing based on stratigraphic correlations among the many depocentres of the region and on published thermochronological data indicates that some erosion surfaces locally formed in less than 3 million years 8 ma 5 7 ma they were subsequently uplifted to their current elevations 1 7 to 2 km by pliocene to quaternary neotectonics in at least two major pulses

the biostratigraphy and magnetic polarity zonation of the pabbi hills northern pakistan an upper siwalik pinjor stage upper pliocene lower pleistocene fluvial sequence abstract the pabbi hills northern pakistan comprise an upper siwalik fluvial sequence spanning 3 2 0 5 ma the portion 2 2 0 9 ma encompasses most of the pinjor faunal stage ca 2 5 0 6 ma of india and was extensively sampled for vertebrate fossil remains with particular attention to recording spatial and vertical provenance detailed palaeomagnetic sampling confirms earlier investigations in the pabbi hills and allows fossil material to be grouped within time bands of 200 300 kyr over 40 000 vertebrate fossil specimens were found of which ca 10 were diagnostic to taxon and skeletal part the distribution of fossil material was non random and over half came from 20 localities we propose here a mammalian biostratigraphy for the upper pliocene to upper lower pleistocene 2 2 0 9 ma of northern pakistan that expands and revises earlier work the elephas hysudricus faunal interval zone ca 2 7 0 8 ma can be usefully divided into an earlier and a later component the earlier part prior to 1 7 ma includes taxa such as sivatherium canis cautleyi hyaenictis or lycyaena anthracotheres and hippopotamids all of which were probably regionally extinct by 1 4 ma taxa seen after but not before 1 4 ma include crocuta panthera an ursid and a herpestid these changes may indicate that dry season grasslands expanded at the expense of woodland habitats after the early pleistocene thereby reducing arboreal habitats and browsing opportunities

the co evolution of black sea level and composition through the last deglaciation and its paleoclimatic significance abstract the black sea was an inland lake during the last ice age and its sediments are an excellent potential source of information on eurasian climate change showing linkages between regionally and globally recognized millennial scale climate events of the last deglaciation here we detail changes from the last glacial maximum lgm through the transition to an anoxic marginal sea using isotopic strontium and oxygen and trace element sr ca ratios in carbonate shells which record changing input sources and hydrologic conditions in the basin and surrounding region sr isotope records show two prominent peaks between 18 and 16 ka bp cal reflecting anomalous sedimentation associated with meltwater from disintegrating eurasian ice sheets that brought black sea level to its spill point following a sharp drop in sr isotope ratios back toward glacial values two stages of inorganic calcite precipitation accompanied increasing oxygen isotope ratios and steady sr isotope ratios these calcite peaks are separated by an interval in which the geochemical proxies trend back toward glacial values the observed changes reflect negative water balance and lake level decline during relatively warm periods bolling allerod and preboreal and increasing river input less evaporation resulting in higher lake levels during the intervening cold period the younger dryas a final shift to marine values in sr and oxygen isotope ratios at 9 4 ka bp cal corresponds to connection with the global ocean and marks the onset of sedimentation on the black sea continental shelf this date for the marine incursion is earlier than previously suggested based on the appearance of euryhaline fauna and the onset of sapropel formation in the deep basin

abrupt changes of temperature and water chemistry in the late pleistocene and early holocene black sea new mg ca sr ca and published stable oxygen isotope and 87sr 86sr data obtained on ostracods from gravity cores located on the northwestern black sea slope were used to infer changes in the black sea hydrology and water chemistry for the period between 30 to 8 ka b p calibrated radiocarbon years the period prior to 16 5 ka b p was characterized by stable conditions in all records until a distinct drop in 18o values combined with a sharp increase in 87sr 86sr occurred between 16 5 and 14 8 ka b p this event is attributed to an increased runoff from the northern drainage area of the black sea between heinrich event 1 and the onset of the bolling warm period while the mg ca and sr ca records remained rather unaffected by this inflow they show an abrupt rise with the onset of the bolling allerod warm period this rise was caused by calcite precipitation in the surface water which led to a sudden increase of the sr ca and mg ca ratios of the black sea water the stable oxygen isotopes also start to increase around 15 ka b p although in a more gradual manner due to isotopically enriched meteoric precipitation while sr ca remains constant during the following interval of the younger dryas cold period a decrease in the mg ca ratio implies that the intermediate water masses of the black sea temporarily cooled by 1 2 c during the younger dryas the 87sr 86sr values drop after the cessation of the water inflow at 15 ka b p to a lower level until the younger dryas where they reach values similar to those observed during the last glacial maximum this might point to a potential outflow to the mediterranean sea via the sea of marmara during this period the inflow of mediterranean water started around 9 3 ka b p which is clearly detectable in the abruptly increasing mg ca sr ca and 87sr 86sr values the accompanying increase in the 18o record is less pronounced and would fit to an inflow lasting 100 a

calibration of the early middle pleistocene transition in the continental beds of the guadix baza basin se spain abstract the magnetostratigraphic and palaeontologic studies carried out in two sections in the guadix baza basin se spain have enabled an accurate calibration of the early middle pleistocene boundary in the continental beds of this basin the palaeontological record rodents in the cortes de baza section indicates an age ranging from the earliest pleistocene latest villanyian or early biharian to the late early pleistocene late biharian the whole cortes de baza section is placed in a reversed magnetic interval identified as the upper part of the matuyama chron in the guadix baza basin the middle pleistocene early toringian was already known at the locality of cullar baza i but new studies in the area have resulted in the recognition of early pleistocene deposits in the lower part of the section thus the locality of cullar baza b is placed in a reversed magnetozone correlated with the uppermost matuyama while the locality of cullar baza c is placed in a normal magnetozone correlated to the lower bruhnes epoch therefore the biharian toringian boundary based on the presence of arvicola cantiana falls well within the bruhnes epoch this result is consistent with what is found in other early middle pleistocene sections of spain atapuerca gran dolina

calibration of the late pliocene early pleistocene transition in the continental beds of the guadix baza basin southeastern spain in this paper a survey of the correlation between magnetic polarity and the mammalian succession in the plio pleistocene sequence of the guadix baza basin is presented in this basin a complete continental sequence from the early pliocene to the middle pleistocene is present allowing the correlation of mammalian biozones with the geomagnetic polarity scale two sections of the baza sector of the basin have been analyzed in order to calibrate the pliocene pleistocene transition the galera middle pliocene to early pleistocene and the orce late pliocene to early pleistocene it is concluded that the boundary between the mn 15 late ruscinian and the mn 16 early villanyian is placed between the 2an 3n chron and the 2an in subchron the late villanyian mn 17 extends up to the upper part of chron 2r 1r the entry of the pleistocene marker allophaiomys pliocaenicus can be placed within subchron 2n olduvai

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

magnetostratigraphic characterization of a thick lower pleistocene lacustrine sequence from the baza basin betic chain southern spain abstract the magnetic polarity stratigraphy from a lacustrine sequence of the baza basin betic chain southern spain has been interpreted as having a lower pleistocene age fifty nine paleomagnetic sites have been obtained and a set of 179 specimens has been demagnetized with both thermal and alternating field procedures several magnetic parameters that depend on the lithology have been obtained the characteristic remanent magnetization polarity has been unambiguously recovered over the whole sequence the materials studied span chron 1r 2 located in the upper matuyama epoch this allows the placement of the faunas studied ranging from the late villanyian to the late biharian in the magnetic polarity time scale mpts this work also proves that magnetostratigraphy can be established in lacustrine sediments even with extremely low magnetic intensities

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

channel migration patterns and related sequences in some alluvial fan systems abstract the pendular displacement of a channel system consisting of an area of higher channel density trunk channel zone on both sides of which channel density progressively decreases secondary channel zone can under favourable subsidence conditions lead to the development of alluvial fans characteristic sequences are found in these fans depending on their position in the sedimentary body a marginal position in the fan is thus recognized by the superposition of fining and thinning upwards ftu cycles the upper part of which is made up of important thicknesses of overbank fines all the backsets of bars dipping in the same direction towards the centre of the cone on the other hand a central position is characterized by a higher number of ftu cycles which are incomplete due to erosion of the upper parts corresponding to the higher concentration of overbank fines and the backsets in each cycle dip alternately in opposite directions the displacement of the channel system in a constant direction may be caused by the preferential accumulation of bars on one of the banks of the channel the change in migratory direction giving rise to the pendular movement is caused by the trunk channel reaching the basin margin or the sedimentation area of an adjoining fan palaeogeographic reconstructions of fans using this technique contribute to the analysis of ancient basins small radius fans with a high sweep angle as are characteristic of basin margins subjected to a low sediment supply subsidence ratio ss sb whereas large radius fans with a low as characterize periods with a high ss sb ratio on the basin margin this model can be applied in economic geology studies as the location of an ancient cone permits delimitation of the axial strip with a higher proportion of coarse highly porous channelled facies and the marginal sectors where thick layers of less porous overbank fines are intercalated we here present the example of the alluvial fans in the guadix fm betic cordillera spain which lie on a basin margin ese where the ss s b ratio increased progressively throughout the lower pliocene the detailed analysis of palaeocurrents on the basis of different criteria throughout the arroyo de gor section helps to locate more precisely and confirm the palaeogeographical distribution of the pliocene cone as deduced from sequential analysis

three dimensional coordination number from two dimensional measurements a new method la valeur de n 3 moyenne des coordonnees du neve a trois dimensions peut etre estimee a partir de n 2 nombre moyen des mesures a deux dimensions et a partir d une fonction qui depend uniquement du rapport entre le rayon moyen de voisinage et de celui du grain de l echantillon

new magnetostratigraphic and numerical age of the fuente nueva 3 site guadix baza basin spain abstract sediments of the plio pleistocene guadix baza basin have provided a wealth of information on the first hominin populations in western europe to better constrain the age of the fuente nueva 3 archaeological site within the basin and to complement previous magnetostratigraphic studies two vertical boreholes were taken that provide a continuous record of the lower part of the sequence results indicate that the sequence is dominated by negative inclinations but some additional intervals with positive inclination are also identified in the lower part of the sequence a new cosmogenic nuclide burial age of 1 50 0 31 ma helps constrain the magnetostratigraphic record the abundance of normal polarity directions at the bottom of a borehole may indicate proximity to the olduvai subchron however further analyses are required to confirm this hypothesis

integrated magnetostratigraphy and biostratigraphy of the upper pliocene lower pleistocene from the monte singa and crotone areas in calabria italy the results of a detailed magnetostratigraphic and biostratigraphic study of late pliocene to early pleistocene marine marl sequences from the monte singa and crotone areas in calabria italy are presented the magnetostratigraphy from the monte singa sequence ranges from below the gauss matuyama boundary up to and including the lower olduvai boundary normal polarities at a level corresponding to isotope stage 81 most probably represent the r union subchron from the lower olduvai boundary upward a reliable magnetostratigraphy could not be established due to increased weathering of the marls resulting in mainly secondary magnetizations the magnetostratigraphy from the composite sequence of the crotone area belongs to a large part of the matuyama chron and includes the olduvai subchron the position of the lower and upper boundaries of the olduvai subzone could be established more precisely than from earlier results moreover the upper boundary of the olduvai subzone poses an ambiguity a relatively long normal polarity interval representing the main olduvai subchron and corresponding to a duration of 115 ka is followed by a short 30 ka reversed subchron and the short 15 ka normal vrica subchron another option and more in accordance with the duration of the olduvai subchron in literature would be to consider the complete n r n polarity succession with a total duration of 160 ka as representing the olduvai subchron implying that this olduvai subchron has a short reversed interval in its upper part linear interpolation and extrapolation yield ages for the most important late pliocene early pleistocene biostratigraphic datum levels an age of 1 69 ma is found for the pliocene pleistocene boundary using the conventional polarity time scale dated with radiometric results however hilgen 1 in correlating the sapropel groups and patterns to the precession curve of the earth s orbit obtained significantly different ages for the polarity transitions of the present study according to this astronomically calibrated polarity time scale the age of the pliocene pleistocene boundary is 1 81 ma

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

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

an abrupt drowning of the black sea shelf abstract during latest quaternary glaciation the black sea became a giant freshwater lake the surface of this lake drew down to levels more than 100 m below its outlet when the mediterranean rose to the bosporus sill at 7 150 yr bp 1 saltwater poured through this spillway to refill the lake and submerge catastrophically more than 100 000 km2 of its exposed continental shelf the permanent drowning of a vast terrestrial landscape may possibly have accelerated the dispersal of early neolithic foragers and farmers into the interior of europe at that time

continental deposits magnetostratigraphy and vertebrate paleontology late neogene of eastern spain abstract eleven sections have been sampled for magnetostratigraphy in the fossil mammal productive late neogene basins of eastern spain the characteristic direction of magnetization was determined through progressive thermal and alternating field demagnetization it was possible to correlate the magnetozones from the various sections to the gpts as well as to the fossil mn zones within the sediment the mn zone boundaries based on this correlation are as follows mn 11 12 8 1 my mn 12 13 6 my mn 13 14 4 9 my mn 14 15 4 18 my mn 15 16 3 58 my new fossil lists are presented for the fuente del viso and loma del castillo faunas in the cabriel basin

late pliocene continental magnetochronology in the guadix baza basin betic ranges spain abstract the late pliocene shallow lacustrine sequences in the guadix baza basin betic ranges southeast spain are a suitable setting for mammal chronology because of the abundance of rich mammal bearing sites stratigraphic superposition of late ruscinian and villanyian vertebrate fossils makes the galera section very appropriate for magnetostratigraphic dating sediments are characterized by a weak but measurable magnetization predominantly carried by magnetite other remanence carriers such as iron sulphides and hematite may be significant only in some particular lithologies such as dark palustrine organic silts and red alluvial beds respectively direct correlation of the galera section to the geomagnetic polarity time scale provides a reliable dating of the late ruscinian and villanyian mammal units the ruscinian villanyian boundary mn15 mn16 is found to occur in the lower gauss chron and approximately correlates to the 3 3 ma cooling event observed in stable isotope and planktonic foraminifera deep sea records the earliest occurrence of late villanyian assemblages mn17 in the lower part of the matuyama chron allows dating of the early late villanyian boundary mn6 mn17 to approximately 2 4 2 6 ma based on the presence of late villanyian assemblages underlying the base of the olduvai chron a maximum age of 1 95 ma top of c2r is attributed to the villanyian biharian mn17 mmq boundary a 300 kyr sedimentary gap in the galera section is suggested to correlate with a probable early villanyian hiatus an hypothesis that agrees with the absence of fossils of this age elsewherein the baza formation

reply to comment by j l diaz hernandez and r julia on quaternary landscape evolution and erosion rates for an intramontane neogene basin guadix baza basin se spain abstract we demonstrate that the age of 43 ka obtained for the topmost calcrete layer in the guadix baza remains the only reliable numerical dating of the flat geomorphic surface that marks the end of the sedimentation in the basin consequently the late pleistocene to holocene erosion rates derived from the incision of the present day drainage network into the flat geomorphic surface remain valid the calcrete radiometric ages reported by diaz hernandez and julia 2012 in their comment are untenable due to the contamination with detrital 230 th not corrected with the applied u th technique and the possible mix of textural elements with different ages older inherited grains and newly formed grains diaz hernandez and julia also quote u th ages for travertine terraces formed later than the calcrete layer these ages lack internal consistency probably due to systematic contamination and or weathering of the samples the archaeological ages reported by diaz hernandez and julia are subjected to great uncertainties but independently of the age assumed as most realistic they are completely compatible with the age of 43 ka that we obtained for the topmost calcrete layer in the guadix baza basin

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

changes in coastline positions during the holocene in the shelf of the northwestern black sea the first evidence for the reconnection of the black sea with the mediterranean sea are euryhaline mollusc species that appear in the bottom sediments lacustrine conditions existed over the larger part of study area at the beginning of the holocene early holocene beds are characterized by a wide distribution of continental facies e g lacustrine marshy and alluvial the lacustrine phase was followed by a marine phase and the transition occurred around ca 8 9 8 5 ka bp the holocene was marked by a gradual increase of mytilus sp shells in sediments reconstructions of coastline positions during the holocene in the northwestern black sea shelf are presented extensive sampling of the study area during several decades allowed the acquisition of a comprehensive data base for paleogeographic reconstructions positions of ancient coastlines are discussed analysis of relief features lithological composition and bottom sediments distribution and faunal complexes allowed identification of paleofacies in the northwestern part of the black sea facial and paloegeographic maps of the holocene discrete time intervals such as the bugazian from ca 10 5 10 to 8 9 8 5 ka bp the vityazevian from ca 8 9 8 5 to 7 1 6 2 ka bp the kalamitian from ca 7 1 6 2 to 4 1 4 0 ka bp and the dzhemetinian from ca 4 1 4 0 to present are presented dating of the sediments is based on uncalibrated radiocarbon determinations study of the granulometry of sediments provided evidence that supports the proposed ancient coastline positions the samples from the cores recovered from different facial zones enabled the characterization of sedimentological environments for each time interval the position of the early holocene coastal sediments is marked out on the level of modern isobaths approximately from 25 to 35 m in the range of time from ca 8 9 8 5 to 7 1 6 2 ka bp the coastline was located at depths from 20 to 25 m the position of the coastline which existed from ca 7 1 6 2 to 4 1 4 ka bp is allocated on the level of modern isobaths from 0 to 15 m comparison of the various positions of the coastline and their facies changes through time indicates that the holocene transgression had a progressively and oscillatory course

a calibrated mammal scale for the neogene of western europe state of the art abstract a magnetobiostratigraphically calibrated mammal scale for the neogene of western europe is presented in this paper the mammal neogene mn units originally proposed by mein report on activity rcmns working groups 1975 have been re defined here on the basis of first appearances of selected small and large mammal taxa the chronology of the lower boundaries of each unit had been established mostly after the significant magnetobiostratigraphic framework developed in the last decade in a number of spanish basins ebro calatayud daroca valles penedes teruel fortuna cabriel and guadix baza in the case of the early and middle miocene particularly mn 1 mn 2 and mn 3 the authors have also taken into account the magnetobiostratigraphic framework developed in the north alpine foreland basin some alternative correlations of the magnetostratigraphic data from this last basin are proposed in order to achieve a higher degree of consistence with the data from the iberian basins a quite well established magnetostratigraphic calibration of the mn boundaries can be proposed for most of the neogene from middle miocene to late pliocene on the other hand the chronological boundaries of the early miocene mn units are still poorly constrained due to 1 scarcity of well studied continuous thick magnetostratigraphic sections 2 the difficulty in defining the boundaries of the mn zones for this time span due to the relative homogeneity and persistence of the fossil rodent faunas and the absence of significant large mammal dispersal events some of the troubles which arise with the application of the mn units strengthen the need to take into account the palaeobiogeographical meaning of these units and their real suitability to date and correlate through extensive geographic areas

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

inclination flattening and the geocentric axial dipole hypothesis abstract william gilbert first articulated what has come to be known as the geocentric axial dipole hypothesis the gad hypothesis is the principle on which paleogeographic reconstructions rely to constrain paleolatitude for decades there have been calls for permanent non dipole contributions to the time averaged field recently these have demanded large contributions of the axial octupole which if valid would call into question the general utility of the gad hypothesis in the process of geological recording of the geomagnetic field earth filters distort the directions many processes for example sedimentary inclination flattening and random tilting can lead to a net shallowing of the observed direction therefore inclinations that are shallower than expected from gad can be explained by recording biases northward transport or non dipole geomagnetic fields using paleomagnetic data from the last 5 million years from well constrained lava flow data allows the construction of a statistical geomagnetic field model such a model can predict not only the average expected direction for a given latitude but also the shape of the distribution of directions produced by secular variation the elongation of predicted directions varies as a function of latitude from significantly elongate in the up down direction at the equator to circularly symmetric at the poles sedimentary inclination flattening also works in a predictable manner producing elongations that are stretched side to side and the degree of flattening depending on the inclination of the applied field and a flattening factor f the twin tools of the predicted elongation inclination relationship characteristic of the geomagnetic field for the past 5 million years and the distortion of the directions predicted from sedimentary inclination flattening allows us to find the flattening factor that yields corrected directions with an elongation and average inclination consistent with the statistical field model the method can be tested using sediments deposited in a known field application of the elongation inclination correction method to two magnetostratigraphic data sets from red beds in asia and pakistan brings the inclinations into agreement with those predicted from modern gps measurements and from global paleomagnetic data there appears to be no compelling reason at this time to abandon the geocentric dipole hypothesis which has provided such an excellent working model for so long

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

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

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

sulfate rich eolian and wet interdune deposits erebus crater meridiani planum mars this study investigates three bedrock exposures at erebus crater an 300 m diameter crater approximately 4 km south of endurance crater on mars these outcrops called olympia payson and yavapai provide additional evidence in support of the dune interdune model proposed for the formation of the deposits at the opportunity landing site in meridiani planum there is evidence for greater involvement of liquid water in the olympia outcrop exposures than was observed in eagle or endurance craters the olympia outcrop likely formed in a wet interdune and sand sheet environment the facies observed within the payson outcrop which is likely stratigraphically above the olympia outcrop indicate that it was deposited in a damp wet interdune sand sheet and eolian dune environment the yavapai outcrop which likely stratigraphically overlies the payson outcrop indicates that it was deposited in primarily a sand sheet environment and also potentially in an eolian dune environment these three outcrop exposures may indicate an overall drying upward trend spanning the stratigraphic section from its base at the olympia outcrop to its top at the yavapai outcrop this contrasts with the wetting upward trend seen in endurance and eagle craters thus the series of outcrops seen at meridiani by opportunity may constitute a full climatic cycle evolving from dry to wet to dry conditions

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

extended range luminescence chronologies suggest potentially complex bone accumulation histories at the early to middle pleistocene palaeontological site of huescar 1 guadix baza basin spain abstract the palaeontological site of huescar 1 contains a diverse faunal assemblage and has played an important role in establishing local scale biozone successions in the guadix baza basin here we provide the first ages for the fossil bearing deposits at this site using a suite of extended range luminescence dating approaches including optically stimulated luminescence osl of quartz supergrains multi grain and single grain thermally transferred osl of quartz and post infrared infrared stimulated luminescence of k feldspars assessments of luminescence characteristics and laboratory quality assurance tests indicate that the huescar 1 sediments are well suited for extended range dating applications and the resultant chronologies obtained using different luminescence approaches display a high degree of consistency our combined luminescence ages reveal that the fossil bearing fluvial sediments at this marginal lacustrine site were deposited 420 460 ka or possibly 420 570 ka which is younger than some of the tentative late early to early middle pleistocene ages inferred from faunal associations comparison of the dating results with taphonomic taxonomic and geomorphic evidence suggests that the site may preserve an admixture of bones in primary depositional context and reworked fossils sourced from potentially older deposits in the surrounding valley as such the luminescence ages obtained for the host sediments may not be contemporaneous with all of the faunal remains preserved at huescar 1

overcoming the stauchwall viscoelastic stress redistribution and the start of full depth gliding snow avalanches 1 when a full depth tensile crack opens in the mountain snowcover internal forces are transferred from the fracture crown to the stauchwall the stauchwall is located at the lower limit of a gliding zone and must carry the weight of the snowcover the stauchwall can fail leading to full depth snow avalanches or it can withstand the stress redistribution the snowcover often finds a new static equilibrium despite the initial crack we present a model describing how the snowcover reacts to the sudden transfer of the forces from the crown to the stauchwall our goal is to find the conditions for failure and the start of full depth avalanches the model balances the inertial forces of the gliding snowcover with the viscoelastic response of the stauchwall we compute stresses strain rates and deformations during the stress redistribution and show that a new equilibrium state is not found directly but depends on the viscoelastic properties of the snow which are density and temperature dependent during the stress redistribution the stauchwall encounters stresses and strain rates that can be much higher than at the final equilibrium state because of the excess strain rates the stauchwall can fail in brittle compression before reaching the new equilibrium snow viscosity and the length of the gliding snow region are the two critical parameters governing the transition from stable snowpack gliding to avalanche flow the model reveals why the formation of gliding snow avalanches is height invariant and how technical measures to prevent snowpack glide can be optimized to improve avalanche mitigation

mechanical and structural properties of weak snow layers measured in situ weak layers such as buried surface hoar or depth hoar frequently form the failure plane of slab avalanches therefore the mechanical properties of such layers in relation to their snow structure have been investigated since it is difficult to transport samples containing a weak layer into cold rooms the mechanical measurements have to be made in situ we investigate strain rate dependency of shear strength by measuring concurrently strength deformation and acceleration using a digital force gauge attached to a 0 05 m 2 shear frame to which an accelerometer and a displacement sensor are fixed in doing so a dynamic force comparable to a driving skier is applied the measurements cover a strain rate range 10 2 to 1 s 1 the samples fail in a brittle manner the shear strength values cover the range 0 2 2 8 kpa the dataset is also used to approximate the coefficient g the shear modulus for different weak layers the snow structure has been analysed macroscopically in the field and for some layers representative snow samples have been extracted in order to prepare in the cold laboratory single sided serial planes with cuts every 0 1 mm recorded by video the analysis of these snow samples should have given the relation between some mechanical properties strength strain and the structural properties due to basic problems in defining the connection between complex snow grains e g surface hoar we were unable to complete this part in due time only preliminary results on this aspect are presented here based on our long term database containing macroscopic structural and strength data of weak layers a relationship between snow type and shear strength has been established

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

calibration of the c 14 timescale over the past 30 000 years using mass spectrometric u th ages from barbados corals uranium thorium ages obtained by mass spectrometry from corals raised off the island of barbados confirm the high precision of this technique over at least the past 30 000 years comparison of the u th ages with 14c ages obtained on the holocene samples shows that the u th ages are accurate because they accord with the dendrochronological calibration before 9 000 yr bp the 14c ages are systematically younger than the u th ages with a maximum difference of 3 500 yr at 20 000 yrbp the u th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration

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

observation of temperature gradient metamorphism in snow by x ray computed microtomography measurement of microstructure parameters and simulation of linear elastic properties the process of temperature gradient metamorphism in snow strongly affects the microstructure and associated mechanical properties of the snow the purpose of this study was to 1 examine the temporal variations in three dimensional snow microstructure under the influence of a strong temperature gradient for 6 days using x ray computed microtomography mct and 2 numerically simulate the linear elastic properties of snow from microtomographic data using a voxel based finite element technique the temporal changes in the snow structure were analyzed in terms of density specific surface area ssa thickness distribution of ice matrix and pores structure model index and mean intercept length mil fabric tensor the structural indices and orthotropic elastic compliance matrix were computed over several sub volumes within the reconstructed volume to account for statistical uncertainties the mean density increased by about 14 on day 1 and no significant trend was observed thereafter the ssa decreased by 22 whereas both the ice and pore thickness distributions widened with time the computed young s moduli were 1 5 4 times larger than previously published dynamic measurements and found to be significantly correlated with ice volume fraction and mil fabric measures the increasing trend in computed moduli during the experiment is consistent with the observed development of thicker vertical ice structures multiple linear regression models of elastic compliances using fabric tensor formulation and ice volume fraction could explain 89 9 93 0 of the variance our results suggest a strong dependence of elastic properties on both density and microstructural fabric

triaxial tests on snow at low strain rate part ii constitutive behaviour fine grained dry snow with a density range of 190 435 kg m 3 was tested in triaxial compression at 12 c with confining pressures varying between 0 and 40 kpa the tests were strain rate controlled with strain rates ranging between 7 4 x 10 7 s 1 and 6 6 10 5 s 1 the analysis of the test results revealed that the relationship between yield stress and viscous strain rate is best given by a power law similar to polycrystalline ice however the power law exponent n is a function of density and varies between 1 8 low density snow p 320 kg in 3 the tests also showed that lower density snow displays a significant non linear stress strain response before yielding two further aspects of the constitutive behaviour of snow were identified 1 the strain rate independence of the post yield work hardening behaviour in compression and 2 the independence of the axial yield stress in relation to the confining pressure the experimental observations are discussed with respect to the mechanical properties of polycrystalline ice which is the constituent material of the load bearing ice skeleton

holocene sea level oscillations and environmental changes on the eastern black sea shelf abstract a multi proxy study of four sediment cores from the eastern caucasian black sea shelf revealed five transgressive regressive cycles overprinted on the general trend of glacioeustatic sea level rise during the last 11 000 14c yr these cycles are well represented in micro and macrofossil assemblages sedimentation rates and grain size variations the oldest recovered sediments were deposited in the neoeuxinian semi freshwater basin 10 500 9000 14c yr bp and contain a caspian type mollusk fauna dominated by dreissena rostriformis low 18o and 13c values are measured on this species the first appearance of marine mollusks and ostracodes from the mediterranean is established in this part of the black sea at 8200 14c yr bp i e about 1000 2000 yr later than the appearance of marine microfossils in the deeper part of the sea the early holocene bugazian to vityazevian condensed section of shell and shelly mud sediments with at least two hiatuses represent a high energy shelf edge facies it contains a transitional assemblage representing a mixture of caspian and mediterranean fauna this pattern suggests a dual flow regime via the bosphorus after 8200 14c yr bp caspian species disappear and oligohaline species decrease in abundance during the vityazevian prekalamitian cycle later during the middle to late holocene low sea level stands are characterized by shell layers whereas silty mud with various mollusk and ostracode assemblages rapidly accumulated during transgressions restricted mud accumulation as well as benthic faunal composition and abundance suggest high energy and well ventilated bottom water during low sea level stands a trend of 18o enrichment in mollusk shells points to an increase in bottom water salinity during the vityazevian to kalamitian transgressions 7000 to 5700 14c yr bp due to a more open connection with the mediterranean while a pronounced increase in polyhaline species abundance is established during the kalamitian to djemetean transgressions 6400 to 2700 14c yr bp however the composition of the faunal assemblage indicates that bottom water salinity never exceeded modern values of 18 20 psu

last glacial holocene paleoceanography of the black sea and marmara sea stable isotopic foraminiferal and coccolith evidence multi proxy data and radiocarbon dates from several key cores from the black sea and marmara sea document a complex paleoceanographic history for the last v30 000 yr the marmara sea was isolated from both the black sea and the aegean sea during glacial periods when global sea level lowering subaerially exposed the shallow sills at the straits of bosphorus and dardanelles i e lake stage and reconnected through both straits during interglacial periods when rise of global sea level breached the shallow sills i e gateway stage micropaleontological data show that during the lake stage the surface water masses in both the marmara sea and black sea became notably brackish however during the gateway stages there was a low salinity surface layer and normal marine water mass beneath two sapropel layers are identified in the marmara sea cores sapropels m2 and m1 were deposited between v29 5 and 23 5 ka and v10 5 and 6 0 ka respectively micropaleontological and stable isotopic data show that the surface water salinities were reduced considerably during the deposition of both sapropel layers m2 and m1 and calculation using planktonic foraminiferal transfer functions shows that sea surface temperatures were notably lower during these intervals the presence of fauna and flora with black sea affinities and the absence of mediterranean fauna and flora in sapropels m1 and m2 strongly suggest that communication existed with the black sea during these times a benthic foraminiferal oxygen index shows that the onset of suboxic conditions in the marmara sea rapidly followed the establishment of fully marine conditions at v11 10 5 ka and are attributed to black sea outflow into the marmara sea since 10 5 ka these suboxic conditions have persisted to the present the data discussed in this paper are completely at odds with the flood hypothesis of ryan et al 1997 and ryan and pitman 1999 crown copyright 2002 elsevier science b v all rights reserved

magnetic polarity stratigraphy of the middle pleistocene ensenadan tarija formation of southern bolivia abstract the tarija formation of southern bolivia which is well known for its classic vertebrate faunas is of prime importance in understanding of the chronology of the ensenadan land mammal age this formation consists of well exposed and relatively fossiliferous sections of clays clayey silts sands gravels and tuffs which were deposited in a predominately fluviatile regime in a pleistocene structural basin four stratigraphic sections each measuring 110 m or less were studied to establish a magnetic polarity stratigraphy paleomagnetic samples were collected from the finer grained sediments at 100 sites spaced at stratigraphic intervals of 5 m or less all paleomagnetic specimens were demagnetized in alternating fields of least 250 oersteds oe some specimens were also thermally demagnetized at 200 c or more of the 100 sites 77 were ultimately used to determine the magnetic polarity zonation based on the four sections sampled the tarija formation spans a time interval from about 1 my to about 0 7 my b p or perhaps younger the lower half of the composite section is of reversed polarity punctuated by a short normal event this sequence probably represents the late matuyama chron with the jaramillo subchron the upper part of the section is of normal polarity and represents early brunhes time a tuffaceous unit 43 m above the brunhes matuyama boundary yielded a fission track zircon age of 0 7 0 2 by b p these data indicate that the classic tarija fauna is middle pleistocene ensendan in age

holocene marginal marine ostracod successions from the kizilirmak river delta implications for depositional environments and sea level changes at the southern black sea coast abstract holocene delta formations are unique records of regional sea climate interactions the kizilirmak delta is the biggest and richest wetland ecosystem in the black sea region of turkey the black sea was uniquely affected by rising sea levels due to its disconnection from the world oceans during the last glacial period to understand the palaeoenvironmental impact on the delta plain we analysed a 14 5 m long sediment core using palaeoecological ostracod analyses accompanied by a palaeo salinity reconstruction based on sieve pore analysis on the ostracod cyprideis torosa this study depicts the interplay of terrestrial and marine settings forming mesohaline shallow lagoons and deltaic lakes since ca 7 9 ka cal bp lagoons with mesohaline to polyhaline salinities and mesohaline to oligohaline lake environments were identified reconstructed palaeo sea level estimations depict a remarkable environmental variability the lagoon habitats at 7 9 to 7 0 and 5 3 to 4 ka cal bp were dominated by cyprideis torosa marine influence led to ostracod associations with loxoconcha spp and tyrrhenocythere amnicola especially between 7 9 and 7 0 ka cal bp riverine influence in the same period but especially at about 7 7 ka cal bp caused dominating amnicythere spp cyprideis torosa and candona neglecta that characterise short phases of a mesohaline deltaic lake environment at about 7 7 and 7 0 ka cal bp as well as after 4 ka cal bp with a subsequent salinity decrease c neglecta and later on pseudocandona marchica became dominant with an interruption by another short term lagoonal phase that might be associated with a megadrought between 3 7 and 3 0 ka cal bp

the last giant continental tortoise of europe a survivor in the spanish pleistocene site of fonelas p 1 abstract the presence of remains of a giant tortoise in the lower pleistocene site of fonelas p 1 guadix basin betic ranges granada southeastern spain is reported and analyzed herein for the first time this finding represents the youngest evidence of a large tortoise in continental europe dating the age of extinction of this successful lineage as several hundred thousand years younger than previously thought so far the most recent record known for continental europe was at least 400 000 years older than the occurrence reported herein vatera greece that for the spanish record being about 1 3 million years older las higueruelas this finding is justified as the youngest evidence of titanochelon a genus recorded in europe since the beginning of the miocene which includes the largest terrestrial turtles known for the entire european fossil record the decrease in the biogeographical distribution area and the final extinction of these temperature sensitive animals in europe is here recognized as a result of the climate changes documented during the pliocene and lower pleistocene the identification of taxa with environmental and ecological requirements as restrictive as those known for the extant and extinct large tortoises living in continental europe 2 0 ma has important consequences thus although the paleoclimatic inferences generally assumed for the whole of europe interpret cooler and drier conditions at the end of the pliocene by the increase of the seasonality and the beginning of the glacial activity in the northern hemisphere the record of fonelas p 1 indicates that in southern europe or at least in the endorheic basins of the betic ranges warmer climatic conditions than in the rest of the continent continued being present in these chronologies of the lower pleistocene being favorable for the persistence of these large tortoises

vertebrate paleontology biostratigraphy geochronology and paleoenvironment of qaidam basin in northern tibetan plateau abstract qaidam basin is the largest terrestrial basin of the tibetan plateau and has the most continuous sedimentary record in the cenozoic although constituting the first known fossil vertebrates of the tibetan plateau and discovered in early scientific expeditions in the 1930s mammalian fossils from qaidam basin have not played a significant role in studying the basin stratigraphy our explorations in the qaidam basin during the past 8 years have resulted in the first well documented collection of fossil vertebrates from there in addition to being the best organisms for terrestrial biostratigraphy in the cenozoic the new fossil vertebrates offer a unique window into the ancient biotas that chronicle the late cenozoic uplift of the plateau and associated environmental changes here we establish for the first time a faunal sequence of early oligocene to early pliocene age four mammalian faunas are recognized olongbuluk mammal fauna middle miocene tuosu mammal fauna early late miocene shengou mammal fauna early late miocene and huaitoutala mammal fauna early pliocene all four mammal faunas can be directly or indirectly tied to a paleomagnetic section in the olongbuluk huaitoutala area permitting robust calibration of the chronology of these faunas at least four fish faunas are also found lulehe fish fauna late early to early late oligocene shengou fish fauna early late miocene eboliang fish fauna late late miocene to early pliocene and yahu fish fauna early pliocene the fish faunas represent the only records of their respective times in the tibetan plateau and thus by themselves cannot be used for age determination however these fish faunas are either integrated into paleomagnetic sections or directly tied to mammal faunas of known ages permitting independent assessment of their chronology zoogeographically qaidam mammal faunas show increasing endemism through time presumably related to topographic barriers formed by the growth and uplift of the tibetan plateau and to climatic changes triggered by the same tectonic process fishes that were trapped in internally drained basins developed pachyostotic morphologies caused by hypersaline environments which are associated with the increasing aridity of the tibetan plateau since early pliocene

paleomagnetic correlation of the mediterranean upper neogene biochronology and villafranchian vertebrate sites of the massif central france magnetostratigraphic studies of pliocene pleistocene continental deposits on the plateau de perrier and in the le puy en velay basin massif central as well as in the riez valensole basin alpes de haute provence mediterranean south provide decisive reference dating of several well known fossil bearing villafranchian sites these are well distributed in the tephrostratigraphy on both sides of the gauss matuyama geomagnetic boundary the roca neyra fauna falls within the matuyama chron while older sediments at les etouaires are situated just above the normal reversed transition the vialette section lies below this reversal within the gauss chron in the riez valensole basin the discovery of the gauss matuyama boundary toward the top of the puimoisson section leads to an excellent correlation with the massif central localities rodents of the seynes zone occur below the reversal while equus appears just above this calibration improves the mediterranean upper neogene biochronology and allows a direct correlation with villafranchian vertebrate sites of the massif central

refinements of the european mammal biochronology from the magnetic polarity record of the plio pleistocene zujar section guadix baza basin se spain abstract the magnetobiostratigraphy study of the 130 m thick zujar section negratin clays unit guadix baza basin spain provides a remarkable opportunity to improve the correlation of european mammal biostratigraphy to the geomagnetic polarity time scale the occurrence of 12 well defined magnetozones and four paleontological sites with diagnostic faunas ranging from the mn 15 biozone ruscinian to the mn 17 biozone villanyian leads to an unambiguous correlation to chrons spanning from the gilbert to the matuyama epochs this provides two new time constraints 1 the boundary between mn 15 ruscinian and mn 16 villanyian biozones is recorded between chron c2an 3n and the base of chron c2an 2n and 2 the boundary between the upper and lower mn 16 subzones villanyian is located between chron c2an 2n and the base of chron c2an 1n the correlation between the ruscinian villanyian boundary and the 3 3 myr b p cooling event seems to be confirmed while the early late villanyian boundary could be tentatively correlated to the glacial event at 2 6 myr b p furthermore mn 15 faunas are found in the lowermost part of chron c2ar which is in agreement with and reinforces the emplacement of the mn 14 mn 15 ruscinian zones boundary at the reversal from chron 3n 1n to chron c2ar

seismic stratigraphy of late quaternary deposits from the southwestern black sea shelf evidence for non catastrophic variations in sea level during the last 10 000 yr abstract detailed interpretation of single channel seismic reflection and huntec deep tow boomer and sparker profiles demonstrates that the southwestern black sea shelf formed by a protracted shelf edge progradation since the miocene pliocene five seismic stratigraphic units are recognized unit 1 represents the last phase of the progradational history and was deposited during the last glacial lowstand and holocene it is divided into four subunits subunit 1a is interpreted as a lowstand systems tract 1b and 1c are interpreted as a transgressive systems tract and subunit 1d is interpreted as a highstand systems tract the lowstand systems tract deposits consist of overlapping and seaward prograding shelf edge wedges deposited during the lowstand and the subsequent initial rise of sea level these shelf edge wedges are best developed along the westernmost and easternmost segments of the study area off the mouths of rivers the transgressive systems tract deposits consist of a set of shingled shore parallel back stepping parasequences deposited during a phase of relatively rapid sea level rise and include a number of prograded sediment bodies including barrier islands beach deposits and thin veneers of seismically transparent muds showing onlap onto the flanks of older sedimentary features a number of radiocarbon dates from gravity cores show that the sedimentary architecture of unit 1 contain a detailed sedimentary record for the post glacial sea level rise along the southwestern black sea shelf these data do not support the catastrophic refilling of the black sea by waters from the mediterranean sea at 7 1 ka postulated by ryan pitman major shimkus maskalenko jones dimitrov gorur sakinc yuce mar geol 138 1997 119 126 ryan pitman touchstone book 1999 319 pp and ballard coleman rosenberg mar geol 170 2000 253 261

catastrophic flooding of the black sea abstract decades of seabed mapping reflection profiling and seabed sampling reveal that throughout the past two million years the black sea was predominantly a freshwater lake interrupted only briefly by saltwater invasions coincident with global sea level highstand when the exterior ocean lay below the relatively shallow sill of the bosporus outlet the black sea operated in two modes as in the neighboring caspian sea a cold climate mode corresponded with an expanded lake and a warm climate mode with a shrunken lake thus during much of the cold glacial quaternary the expanded black sea s lake spilled into to the marmara sea and from there to the mediterranean however in the warm climate mode after receiving a vast volume of ice sheet meltwater the shoreline of the shrinking lake contracted to the outer shelf and on a few occasions even beyond the shelf edge if the confluence of a falling interior lake and a rising global ocean persisted to the moment when the rising ocean penetrated across

timing of the last glacial maximum from observed sea level minima during the last glacial maximum ice sheets covered large areas in northern latitudes and global temperatures were significantly lower than today but few direct estimates exist of the volume of the ice sheets or the timing and rates of change during their advance and retreat here we analyze four distinct sediment facies in the shallow tectonically stable bonaparte gulf australia each of which is characteristic of a distinct range in sea level to estimate the maximum volume of land based ice during the last glaciation and the timing of the initial melting phase we use faunal assemblages and preservation status of the sediments to distinguish open marine shallow marine marginal marine and brackish conditions and estimate the timing and the mass of the ice sheets using radiocarbon dating and glacio hydroisostatic modelling our results indicate that from at least 22 000 to 19 000 calendar years before present land based ice volume was at its maximum exceeding today s grounded ice sheets by 52 5 x 10 exp 6 cu km a rapid decrease in ice volume by about 10 percent within a few hundred years terminated the last glacial maximum at 19 000 250 years

long plio pleistocene terrestrial record of climate change and mammal turnover in southern spain abstract cyclostratigraphic analysis of the pliocene zujar section guadix baza basin southeastern spain has enabled the recognition of a number of climatically forced cycles reflecting alternating dry and wet periods peaks of aridity are recorded at ca 3 95 3 55 3 2 2 8 and 1 8 myr b p the first dry period at about 4 0 myr b p corresponds to the early ruscinian mammal age while the second arid interval at about 3 6 myr b p corresponds to the establishment of the mediterranean double seasonality the significant mammal turnover between the late ruscinian and early villanyian stages is placed between chron 2an 2n and the very base of chron 2an 1n coincident with the dry phase recognized at about 3 2 myr b p the fourth aridity maximum at 2 8 myr b p roughly coincides with the equus event in western europe and is probably related to the beginning of the glacial interglacial dynamics in the northern hemisphere finally the last dry peak at about 1 8 myr b p is probably related to the set of mammalian events characterizing the transition from the late pliocene faunas to those of the early pleistocene

biostratigraphy and geology of the neogene siwalik group of the surai khola and rato khola areas in nepal abstract an almost complete sequence of neogene molasse sediments of the siwalik group in the surai khola khola means small river in nepali area in nepal which was divided into five lithological units includes the upper part of the lower siwaliks the middle and the upper siwaliks it discloses a tectonically uncomplicated southern belt i e the surai khola sequence and a tectonically much disturbed northern belt the upper siwaliks at surai and rato khola yield a rich vertebrate fauna contained within thick bodies of multistoried sandstones the data from the pollen and plant fossils indicate vegetational changes from tropical evergreen forests in the lower and middle siwaliks to dry deciduous forests and grasslands by the beginning of the upper siwaliks biostratigraphically the upper siwalik sediments can be compared with the hexaprotodon sivalensis and the elephas planifrons interval zones of pakistan and with the tatrot and pinjor formations of northwest india palaeomagnetic dating of the surai khola sequence indicate a time scale from 13 to ca 1 million years

laboratory experiments on shear failure of snow using a direct simple shear apparatus snow samples 115 mm in diameter 16 18 mm in height taken from a so called homogeneous layer small rounded particles density 290 kg m 3 were tested in a cold laboratory experiments were performed for strain rates between 7 10 6 s 1 and 5 10 3 s 1 at test temperatures of 5 c 10 c and 15 c the effects of strain rate and temperature on failure stress failure strain stiffness initial tangent modulus and toughness were studied the transition between the ductile and brittle sudden fracture state of failure was found to be at about 1 10 3 s 1 for the snow types tested independent of temperature stiffness proved to be the most temperature dependent property of alpine snow it strongly increases with decreasing temperature failure strain and toughness decrease with decreasing temperature failure stress was found to increase slightly with decreasing temperature the effect is not very distinct but close to statistically significant and might be partly hidden by the scatter in the stress data due to variations inherent in sampling and testing

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

triaxial tests on snow at low strain rate part i experimental device a deformation controlled triaxial apparatus has been developed in order too investigate the mechanical behaviour of alpine snow cylindrical specimens 58 mm in diameter 126 mm in height can be axially deformed by applying tensile or compressive strain rates between 2 4 10 7 s 1 and 2 4 10 2 s 1 compressed air is used to laterally load the snow specimens with pressures of up to 40 kpa the volumetric deformation is found by carefully encapsulating the snow samples in an airtight mylar foil and measuring the expelled pore air during sample deformation the multidimensional stress strain behaviour can therefore be determined and constitutive theories of snow advanced the device is located run the cold rooms of the weissfluhjoch research station of the swiss federal institute for snow anti avalanche research seine 180 tests have been performed over the last four winters the density of the snow specimens varied between 190 and 435 kg m 3 part i of this two part paper discusses the development of the apparatus and the applied testing methodology qualitative results are provided in part ii a detailed analysis of the results is presented and the viscoclastic properties of snow quantified