paleomagnetic reconstruction of the global geomagnetic field evolution during the matuyama brunhes transition iterative bayesian inversion and independent verification abstract the earth s magnetic field changed its polarity from the last reversed into today s normal state approximately 780 000 years ago while before and after this so called matuyama brunhes reversal the earth magnetic field was essentially an axial dipole the details of its transitional structure are still largely unknown here a bayesian inversion method is developed to reconstruct the spherical harmonic expansion of this transitional field from paleomagnetic data this is achieved by minimizing the total variational power at the core mantle boundary during the transition under paleomagnetic constraints the validity of the inversion technique is proved in two ways first by inverting synthetic data sets from a modeled reversal here it is possible to reliably reconstruct the gauss coefficients even from noisy records second by iteratively combining four geographically distributed high quality paleomagnetic records of the matuyama brunhes reversal into a single geometric reversal scenario without assuming an a priori common age model the obtained spatio temporal reversal scenario successfully predicts most independent matuyama brunhes transitional records therefore the obtained global reconstruction based on paleomagnetic data invites to compare the inferred transitional field structure with results from numerical geodynamo models regarding the morphology of the transitional field it is found that radial magnetic flux patches form at the equator and move polewards during the transition our model indicates an increase of non dipolar energy prior to the last reversal and a non dipolar dominance during the transition thus the character and information of surface geomagnetic field records is strongly site dependent the reconstruction also offers new answers to the question of existence of preferred longitudinal bands during the transition and to the problem of reversal duration different types of directional variations of the surface geomagnetic field continuous or abrupt are found during the transition two preferred longitudinal bands along the americas and east asia are not predicted for uniformly distributed sampling locations on the globe similar to geodynamo models with cmb heatflux derived from present day lower mantle heterogeneities a preference of transitional vgps for the pacific hemisphere is found the paleomagnetic duration of reversals shows not only a latitudinal but also a longitudinal variation even the paleomagnetically determined age of the reversal varies significantly between different sites on the globe the described bayesian inversion technique can easily be applied to other high quality full vector reversal records also its extension to inversion of secular variation and excursion data is straightforward

coupled deep water flow and climate variability in the middle pleistocene north atlantic abrupt changes in the strength of the atlantic meridional overturning circulation comprising northward flow of warm water and a cold southward return flow are implicated in abrupt climate changes in the late pleistocene a sensitive place to assess this circulation is in the cold return flow of deep western boundary currents here in records of flow speed and isotopic composition of surface and bottom waters from a deep western boundary current location near the northern source of north atlantic deep water we show both orbital and millennial scale coupling between deep ocean flow and climate in the middle pleistocene 0 75 0 87 ma when the boundary conditions in terms of the mean state and amplitude of climate change were different from more recent periods the coupling appears as a phased series of events initiated by reduced vertical density gradients and initial ventilation of deep waters the occurrence of these events in interglacials during the middle pleistocene suggests that the millennial scale climate variability in the north atlantic was more pronounced at that time than previously thought this demonstrates that given the right boundary conditions rapid climate shifts can also occur during relatively warm climate conditions

mound development as an interaction of individual plants with soil water erosion and sedimentation processes on slopes in the mediterranean region semi natural shrubland communities named matorral often present a discontinuous cover where isolated perennial plants alternate with bare inter plant areas in such ecosystems the patchy distribution of the vegetation is usually associated with microtopographic sequences of mounds that develop under isolated plants and break the overall slope continuity in this study the influence of three representative species of the mediterranean matorral rosmarinus officinalis stipa tenacissima and anthyllis cytisoides on slope microtopography is determined and the processes that take part in the development of microtopographic structures beneath the plant canopy are identified the influence of slope gradient plant species and plant parameters on the shape and height of microtopographic structures is also studied the shape of the microtopographic structures is described by using a two dimensional microprofilemeter and mound height is determined by measuring in the field a mound height index defined as the distance from the top to the bottom of the mound the results obtained show that plant species play a major role in the shape and height of the microtopographic structures whereas terrace type structures generally develop under anthyllis shrubs microtopographic forms associated with rosmarinus and stipa plants vary with slope gradient the almost symmetric mound type structures that develop under these two species on gentle slopes change into terrace type structures as slope gradient increases moreover statistically significant differences exist between the three species with regard to mound height mean values of mound height are 19 4 14 6 and 4 3 cm under the canopy of stipa rosmarinus and anthyllis respectively plant parameters essentially roughness and slope gradient have a significant influence on mound height index four main processes were identified as affecting mound development in the studied field site sedimentation differential interrill erosion differential splash erosion and bioturbation plant species interact in different ways with these processes according to their morphologies since stipa and rosmarinus plants are more efficient than anthyllis shrubs in controlling water erosion in retaining sediments and in modifying soil properties under their respective canopies they give rise to higher microtopographic structures that facilitate water and nutrient storage by plants on slopes copyright 2000 john wiley sons ltd

paleoenvironmental changes at the lower pleistocene montalbano jonico section southern italy global versus regional signals abstract integrated high resolution data from calcareous plankton assemblages foraminifera and nannofossils together with geochemical and mineralogical investigations have been collected at the on land montalbano jonico section southern italy in order to reconstruct the paleoenvironmental changes through marine isotope stages mis 23 37 time series analysis on globigerina bulloides and cassidulina carinata 18o records and on selected calcareous plankton proxies mainly revealed the occurrence of precession and obliquity forcing the deposition of sapropel layers which are interbedded in the montalbano jonico section was driven by water column stratification insolation cycle i 104 and enhanced sea surface water productivity insolation cycle i 112 i 102 and i 86 different paleoenvironmental conditions mark the sedimentary evolution of the section from 1240 to 1082 ka mis 37 mis 32 high percentage abundances of warm and oligotrophic planktonic foraminifera and calcareous nannofossil taxa indicate the establishment of oligotrophic and stratified surface water conditions a key paleoenvironmental change occurred during mis 31 from about 1080 to 1065 ka which was a very warm interglacial characterized by an increase of tropical subtropical globigerinoides ruber group and globigerinoides trilobus and low salinity braarudosphaera bigelowii sea surface water taxa during this interval more humid climate conditions coupled with changes in local paleomorphology may have triggered a higher and unusual freshwater input and the creation of a new entry point for sediment supply into the basin from a different drainage area from about 1065 to 1010 ka mis 30 mis 29 a cool and dry climate prevailed in the circum mediterranean area during a time of precession maxima this favored lowered sea surface temperatures and an increase of polar water neogloboquadrina pachyderma left coiling there are also indications of a reduction of the terrigenous input from the new source area from 1010 ka upward mis 28 mis 23 the higher abundances of globigerina bulloides turborotalita quinqueloba and calciosolenia spp indicate enhanced productivity conditions probably related to high turbidity of sea surface waters triggered by a more conspicuous sediment input from land analysis of the long term trends in the multiproxy patterns suggests that the major paleoenvironmental changes occurred as a consequence of the combined effect of orbitally controlled global climate and regional processes

residual circulation in shallow estuaries 1 highly stratified narrow estuaries long wave theory and simple turbulence closures have been used to show that three distinct types of circulation highly stratified weakly stratified and partially mixed arise in narrow shallow estuaries from the finite amplitude of the tide and the interaction of stratification with vertical mixing each type has a different dominant process causing the vertical exchange of salt and fresh water on the flood and each gives rise to a characteristic residual circulation the tidal circulation in highly stratified shallow estuaries described herein is the result of a finite amplitude internal motion driven by the barotropic tide shear instabilities at the interface are the major vertical exchange mechanism the residual circulation is caused primarily by ebb flood asymmetry in interface position and thickness a model based on our theoretical analysis shows that the interface thickness on flood is much less than the depth of flow up to a critical tidal amplitude at which the two layer flow is destroyed and correctly predicts the tidal amplitude of the neap spring transition in the columbia river estuary tidal frequency internal wave motion is not found in weakly stratified and partially mixed estuaries because of the reduced tidal shear shear instabilities are weak or absent and the residual circulation assumes a very different character as described in part 2

reconciling astrochronological and 40ar 39ar ages for the matuyama brunhes boundary and late matuyama chron when five matuyama brunhes m b boundary records from the north atlantic are placed on isotope age models produced by correlation of the 18o record directly or indirectly to an ice volume model the m b boundary lies consistently at the young end of marine isotope stage 19 with a mean age for the midpoint of the reversal of 773 1 ka standard deviation 0 4 kyr 7 kyr younger than the presently accepted astrochronological age for this polarity reversal 780 781 ka two recently proposed revisions of the age of the 40ar 39ar fish canyon sanidine fcs standard to 28 201 0 046 ma and 28 305 0 036 ma would adjust 40ar 39ar ages applicable to the m b boundary and other reversals and excursions back to 1 2 ma to ages older than the new astrochronological ages by 8 24 kyr the variables used to construct the ice volume models cannot account for the discrepancy the fcs standard age that best fits the astrochronological ages is 27 93 ma which is within the uncertainty associated with the commonly used value of 28 02 0 16 ma but younger than the recently proposed fcs ages the edc2 and edc3 age models in the dome c antarctic ice core yield ages of 771 7 ka and 766 4 ka respectively for the 10be flux peak that denotes the paleointensity minimum at the reversal boundary implying that the edc2 rather than edc3 age model is consistent with the observations from marine sediments at least close to the m b boundary

biogeomorphology revisited looking towards the future although biogeomorphological research is well established with many studies on a range of two way interrelations between organisms and geomorphology in different environments there is little consensus over what constitutes biogeomorphology why it might be useful and where it is heading starting with definitions of core biogeomorphic processes we consider the need for future biogeomorphological studies to evaluate the crucial links between bioprocesses biological community dynamics and inorganic earth surface processes five key applications of biogeomorphological research are identified the roles of organisms in environmental reconstruction trace fossil analysis extraterrestrial geomorphology environmental engineering and the built environment some key research directions and methodological challenges for future biogeomorphological research include expanding the spatial and temporal coverage of datasets investigating the role of bioprocesses in landform development tackling scale issues investigating the relevance of nonlinear dynamical ideas to biogeomorphology and developing better sampling and monitoring techniques for bioprocesses

the montalbano jonico marine succession an archive for distal tephra layers at the early middle pleistocene boundary in southern italy abstract the lithological content and mineralogical assemblage of main tephra layers v1 v2 v3 v4 v5 v7 embedded in the montalbano jonico succession have been fully characterized major element analyses were carried out on the juvenile glass fractions and main crystal phases and trace element contents were determined on glasses extracted from the thickest layer of the sequence v5 single crystal 40 ar 39 ar laser fusions were performed on sanidine from the v4 layer yielding a weighted mean age of 773 9 1 3 ka the vulture volcano is likely the source of two tephra layers v3 and v4 embedded to the middle part of the interval b of the sequence which represent the oldest products of this center ever found moreover the v4 layer was emplaced near the matuyama bruhnes chron boundary and thus serves as an important chronostratigraphic marker complete chemical characterization of v5 allows us to suggest the campanian volcanic zone as its eruptive source corroborating the idea that activity there began at 720 ka and spanned most of the middle pleistocene finally we insert our new framework from the montalbano jonico sequence into a reappraised tephra sequence from the middle pleistocene to present in southern italy which results in a more robust series of tephrostratotypes and improves the reliability of inter archive correlations

the lower and middle pleistocene geological record of the san lorenzo lacustrine succession in the sant arcangelo basin southern apennines italy abstract a facies analysis and preliminary palaeoclimate and biochronology investigation are presented for the san lorenzo lacustrine deposits outcropping in the pliocene to pleistocene satellite sant arcangelo basin southern apennines facies analysis shows that sedimentation developed in the inner zone of a terrigenous dominated fresh water lake the pollen record shows repeated alternations between two distinct vegetational assemblages one dominated by steppe taxa and the other one by forest taxa the faunal assemblage is indicative of a late biharian mammal age the palaeomagnetic survey yielded three polarity intervals throughout the succession the middle one is of reversed polarity and is associated with a volcaniclastic layer radiometrically dated at approximately 1 ma and thus the two normal polarity intervals are identified as the jaramillo subchron and the base of the brunhes chron the detailed geological and paleontological analyses as well as the preliminary results from the palynological and magnetostratigraphical investigation indicates that these deposits may contain a continuous record of both climatic changes and tectonic activity within the sant arcangelo basin during the early and middle pleistocene

overview of the montalbano jonico area and section a proposal for a boundary stratotype for the lower middle pleistocene southern italy foredeep abstract in the southernmost part of the southern apennine foredeep crops out a well exposed and continuous succession about 500 m thick of muds and muddy silts and several interbedded volcaniclastic layers on the basis of nannofossil biostratigraphy it ranges from large gephyrocapsa to pseudoemiliania lacunosa zones that indicate the upper part of the lower pleistocene and the lower part of the middle pleistocene the vertical distribution of both invertebrate fossil assemblages and teleostean otoliths points out changes in the primary environmental parameters particularly bathymetry sedimentation rate and oxygen concentration the observations allowed the reconstruction of several deepening shallowing cycles within a general regressive framework the montalbano jonico composite section is likely to represent a regressive portion of a third order cycle in which relevant tectonic pulses should be the main reason for the general shallowing possibly related to the beginning of the filling up phase of the southern part of the apennines foredeep the two recognized fourth order cycles could be related to tectonoeustatic causes the higher frequency cyclicity represented by several fifth order cycles seems to be mainly connected with astronomical relationships the montalbano jonico section could be suitable for defining the lower middle pleistocene boundary stratotype the potential gssp could be located close to the small gephyrocapsa p lacunosa zonal boundary near a biohorizon rich in delectopecten vitreus a muddy dark grey sapropelitic layer rich in chondrites ichsp and in oxygen isotopic stage 25 another potential location of the gssp of middle pleistocene could be near the volcaniclastic horizon v4 close to the isotopic stage 19 boundary

particle trapping in estuarine tidal flows particle trapping in estuarine turbidity maxima etm is caused primarily by convergent mean and or tidal fluxes of sediment the result is an approximately bell shaped along channel distribution of vertically integrated tidal cycle mean suspended sediment concentration observations from the columbia river estuary suggest that 1 strong two layer or internal along channel residual and overtide flows are generated by time varying stratification and 2 correlations between the near bed velocity and the suspended sediment fields at these frequencies are important in landward transport of sediment a new spatially and temporally integrated form of the sediment conservation equation has been derived to analyze this trapping process time changes in tidally averaged sediment concentration between two estuarine cross sections can be shown to be related to the divergence of the seaward river flow transport the divergence of velocity shear sediment stratification correlations for the mean flow and each tidal constituent and net erosion or deposition at the bed vertically integrated variables other than seaward river transport are absent from this integrated balance analysis of sediment fluxes using this balance supports the idea that internal residual and overtide circulations are primarily responsible for the landward sediment transport on the seaward side of etm found near the upstream limits of salinity intrusion the balance also shows that attempts to represent fluxes causing trapping of sediment in an etm as a product of a time mean vertically integrated along channel gradient and a diffusivity inevitably lead to the appearance of countergradient transport and thus a negative diffusivity on the seaward side of the etm this result occurs because the trapping process is inherently nonlinear and at least two dimensional and because a one dimensional representation is physically unrealistic

surface and deep ocean circulation in the subpolar north atlantic during the mid pleistocene revolution 1 we investigated surface and deep ocean variability in the subpolar north atlantic from 1000 to 500 thousand years ago ka based on two ocean drilling program odp sites feni drift site 980 55 29 n 14 42 w and bjorn drift site 984 61 25 n 24 04 w benthic foraminiferal stable isotope data planktic foraminiferal faunas ice rafted debris data and faunally based sea surface temperature estimates help test the hypothesis that oceanographic changes in the north atlantic region were associated with the onset of the 100 kyr world during the mid pleistocene revolution based on percentage of neogloboquadrina pachyderma s records from both sites surface waters during interglacials and glacials were cooler in the mid pleistocene than during marine isotope stages mis 5 and 6 in particular interglaciations at bjorn drift site 984 were significantly cooler faunal evidence suggests that the interglacial arctic front shifted from a position between the two sites to a position northwest of bjorn drift site 984 after ca 610 ka as during the late pleistocene we find faunal evidence for lagging surface warmth at most of the glacial initiations during the mid pleistocene each initiation is associated with high benthic 13c values that are maintained into the succeeding glaciation which we term lagging nadw production these findings indicate that lagging warmth and lagging nadw production are robust features of the regional climate system that persist in the middle to late pleistocene

timing of the matuyama brunhes geomagnetic reversal decoupled thermal maximum and sea level highstand during marine isotope stage 19 recent high resolution magnetic and microfossil data from a long core penetrating the osaka group japan are astronomically tuned and reassessed to reveal detailed stratigraphic features across the matuyama brunhes mb polarity transition during marine isotope stage mis 19 the sediments have a uniform and high average accumulation rate of 63 cm ky astronomical tuning based on six calibration points including a clear mis 19 2 sea level lowstand dates the main mb boundary mbb to 777 6 ka the sea level peak of the mis 19 3 highstand to 780 7 ka and the climatic thermal maximum tm to 776 4 ka the mb transition began with a short lived normal polarity episode that occurred before the highstand at mis 19 3 and terminated with multiple rapid reversals that occurred between highstand mis 19 3 and lowstand 19 2 the tm just postdates the termination of the mb transition and occurs about 4000 years after the sea level peak the delayed tm is also observed at gesher benot ya aqov israel and on the mediterranean coast and possibly at lake baikal in high resolution records from chinese loess paleosols and deep sea sediments the rapid reversal zone of the mbb has a very similar climatostratigraphic character these magneto climatostratigraphic features in mis 19 are useful for correlating between terrestrial and marine sediments the delay in warming relative to the sea level highstand seems to have been due to a cloud albedo effect induced by an increase in galactic cosmic ray flux during an extremely low magnetic field intensity interval

geographical distribution of transitional vgps evidence for non zonal equatorial symmetry during the matuyama brunhes geomagnetic reversal abstract paleomagnetic records of the matuyama brunhes polarity reversal obtained recently from the northern equatorial and southern latitudes of the atlantic sector display a distinct symmetry with respect to the equator the virtual geomagnetic pole vgp paths from the mid latitude sites in the northern and southern hemispheres dsdp site 609 and core v16 58 are nearly coincident tracking northward through the americas the vgp path from the equatorial site odp site 664 tracks northward through eastern asia nearly antipodal to the other two paths modeling results indicate that superimposing an h 1 3 geometry onto a reversing axial dipole explains the sense of equatorial symmetry exhibited by these three records these results are consistent with the bulk of the data available from other records of this polarity transition suggesting that the transitional vgps during this reversal tend to fall along two distinct longitudinal bands the grouping of transitional vgps suggests that there is a strong geographical control over the reversal process an apparent correlation between the longitudinal bands of transitional vgps and the location of the major flux concentrations in the radial component of the historical geomagnetic field at the core mantle boundary 1 suggests that the processes which cause these flux concentrations may have influenced the geometry of the matuyama brunhes transitional field

high resolution climate stratigraphy across the matuyama brunhes transition from palynological data of osaka bay sediments in southwestern japan abstract this study presents a high resolution palynological analysis of a sedimentary core from osaka bay japan straddling marine oxygen isotope stage mis 19 i e across the matuyama brunhes magnetic polarity boundary mbb comparison with the standard marine oxygen isotope curve bassinot f c labeyrie l d vincent e quidelleur x shackleton n j lancelot y 1994 the astronomical theory of climate and the age of the brunhes matuyama magnetic reversal earth and planetary science letters 126 91 108 demonstrates that variations in vegetation and the basinal environment coincided with global ice volume changes the late mis 20 is characterized by boreal climate with coniferous forest in mis 19 the forest was generally dominated by fagus and quercus lepidobalanus suggesting onset of humid climatic conditions slightly cooler than the present excluding coastal vegetation components climate during mis 19 can be subdivided into three stages the early stage including substage 19 3 is characterized by high seasonality in precipitation this contrasts with the very abundant year round precipitation that is inferred for the late stage from substage 19 2 to substage 19 0 which is characterized by cool temperate coniferous taxa including cryptomeria the very high precipitation rates of the latter persisted at least up to substage 18 4 there was no apparent vegetational response to the sea level highstand of 19 3 in contrast a short lived thermal maximum event took place ca 6 7 kyr later i e in middle mis 19 this event is characterized by increases in the warm temperate element quercus cyclobalanopsis the mbb the recommended criterion for defining the lower middle pleistocene boundary took place in middle mis 19 these lines of evidence indicate that the occurrence of the mbb corresponded with a shift towards warmer and wetter climatic conditions similar warming and wetting events across the mbb are also observed in pollen records from southern italy and central japan this possibly provides long distance correlation and may suggest a connection between the earth s magnetic field and climate

rock magnetism and palaeomagnetism of the montalbano jonico section italy evidence for late diagenetic growth of greigite and implications for magnetostratigraphy summary the montalbano jonico mj section cropping out in southern italy represents a potential candidate to define the lower middle pleistocene boundary and it has been proposed as a suitable global stratotype section and point gssp of the ionian stage middle pleistocene the mj section is the only continuous benthic and planktonic 18o on land reference in the mediterranean area for the mid pleistocene transition spanning an interval between about 1240 and 645 ka combined biostratigraphy and sapropel chronology tephra stratigraphy and complete high resolution benthic and planktonic foraminiferal stable oxygen isotope records already provide a firm chronostratigraphic framework for the mj section however magnetostratigraphy was still required to precisely locate the brunhes matuyama transition and to mark the gssp for the ionian stage we carried out a palaeomagnetic study of a subsection ideale section of the mj composite section sampling 61 oriented cores from 56 stratigraphic levels spread over a ca 80 m thick stratigraphic interval that correlates to the oxygen isotopic stage 19 and should therefore include the brunhes matuyama reversal the palaeomagnetic data indicate a stable and almost single component natural remanent magnetization nrm a characteristic remanent magnetization chrm was clearly identified by stepwise demagnetization of the nrm the chrm declination values vary around 0 and the chrm inclination around the expected value 59 for a geocentric axial dipole field at the sampling locality this result indicates that the section has been remagnetized during the brunhes chron a preliminary study of 27 additional not azimuthally oriented hand samples collected at various levels from other parts of the mj composite section indicates that all the samples are of normal polarity and demonstrates that the remagnetization is widespread across the whole exposed stratigraphic sequence a series of specific rock magnetic techniques were then applied to investigate the nature of the main magnetic carrier in the study sediments and they suggest that the main magnetic mineral in the mj section is the iron sulphide greigite fe3s4 scanning electron microscope observations and elemental microanalysis reveal that greigite occurs both as individual euhedral crystals and in iron sulphides aggregates filling voids in the clay matrix therefore we infer that the remagnetization of the section is due to the late diagenetic growth of greigite under reducing conditions most likely resulting in the almost complete dissolution of the original magnetic minerals iron sulphide formation in the mj section can be linked to migration of mineralized fluids our inferred timing of the remagnetization associated with greigite growth represents the longest remanence acquisition delay documented in greigite bearing clays of the italian peninsula so far

the geomorphic influences of beaver dams and failures of beaver dams abstract uncounted millions of beaver ponds and dams existed in north america prior to european contact and colonization these ponds acted as sediment traps that contained tens to hundreds of billions of cubic meters of sediment that would otherwise have passed through the fluvial system removal of beavers by overtrapping in the 16th 19th centuries severely reduced their number and the number of ponds and dams dam removal altered the fluvial landscape of north america inducing sediment evacuation and entrenchment in concert with widespread reduction in the wetlands environments partial recovery of beaver populations in the 20th century has allowed reoccupation of the entirety of the pre contact range but at densities of only one tenth the numbers nevertheless modern beaver ponds also trap large volumes of sediment in the high hundred millions to low billions of cubic meters range failure of beaver dams is a more common phenomenon than often assumed in the literature during the past 20 years numerous cases of dam failure have been documented that resulted in outburst floods these floods have been responsible for 13 deaths and numerous injuries including significant impacts on railway lines

a magnetostratigraphic reassessment of correlation between chinese loess and marine oxygen isotope records over the last 1 1 ma abstract we present a magnetic polarity based paleoclimatic correlation between chinese loess and marine oxygen isotope stage mis records over the last 1 1 ma this revised land ocean comparison indicates that inconsistent occurrence of the matuyama brunhes boundary which lies in mis 19 in marine sediments and occurs either at the base lower part of loess l8 or the uppermost part of soil s8 in chinese loess is due to regional and or local climate variability across the chinese loess plateau and does not need to be attributed to lock in effects of loess remanence acquisition associated with pedogenesis this result implies that the geomagnetic polarity boundaries in chinese loess in general are reliable chronostratigraphic time markers therefore astronomically tuned timescales for chinese loess that presume a downward shift of polarity boundaries due to a time lag in remanence acquisition may have overestimated ages of certain loess paleosol units

vegetation and climate across the early middle pleistocene transition at montalbano jonico southern italy abstract pollen analysis of the montalbano jonico marine succession mjs southern italy provides a continuous vegetational record between 858 ka and 745 13 ka which includes marine isotope stage mis 19 now considered the closest orbital analogue to the holocene a comparison between paleoclimate proxies and global signals of past climate change allows the pollen record to be interpreted in terms of major environmental and climate modifications through mis 21 18 at the orbital and sub orbital scale this is also central to understanding migration patterns of the genus homo interglacials are expressed by the dominance of a mesophilic vegetation typical of a warm temperate and relatively humid climate deciduous quercus dominated fully temperate arboreal forest already devoid of subtropical taxa wooded steppes to steppes expanded during glacials when cold and dry conditions prevailed at mjs the main expansion of temperate forest dominated by broad leaved trees correlates to mis 19 3 whereas the expansion of steppe vegetation during drier conditions marks mis 19 2 directly above the volcaniclastic layer v4 dated at 773 9 1 3 ka more intensively arid conditions developed during mis 20 and mis 18 the pollen temperature index reaches its minimum in uppermost mis 20 in agreement with a significant cold and arid climate phase of wide significance in the north hemisphere as documented by prominent peaks in north atlantic ice rafted debris ird and mediterranean aeolian dust records on the other hand artemisia a significant component of steppes shows its maximum expansion during earlier phases of mis 18 millennial to sub millenial scale climate variability is evidenced by two abrupt short term pollen events within mis 19 3 which show a dominant increase of the cosmopolitan herbaceous component at around 783 54 ka and 774 84 ka respectively the vegetational and inferred climate changes for mis 19 offer two possibilities 1 to investigate the interglacial climate variability and discuss the linkage between climate and changes in geomagnetic field intensity close to the matuyama brunhes paleomagnetic boundary mbb and 2 to help evaluate the role of the mbb in defining the middle pleistocene global boundary stratotype section and point gssp with respect to point 2 a comparison of data at mjs with the pollen record at the nearby and coeval valle di manche section is relevant and evidences the complex response of vegetation to climate events possibly under the effects of both astronomical and local factors

interactions of plant growth and sediment movement on slopes in a semi arid environment abstract the morphology and architecture of the tussocks of alpha grass stipa tenacissima as well as its associated micro topography have been described in several sites on the south versant of the filabres range in southern spain the annual rainfall of this area is between 225 and 275 mm and plant cover ranges from 20 to 45 the results show the formation of micro topographic mounds upslope of the tussocks which are interpreted as deposition bodies originating from the interception of downslope sediment movement by the vegetated patches the tussock architecture shows an outer growing zone a middle mature zone and a central senescent zone the outward expansion of the tussock is performed by tillers in the growing zone which bend at the nodes and root when they come into contact with the soil surface the mat of dead leaves inside the tussock may prevent the stems from bending and this factor plays a significant role in controlling tussock growth a similar effect on slopes is produced by the mound of sediments which accumulate upslope of the tussock and press upon the growing stems a simple simulation model has been built from the above field observations the model is able to reproduce the tussock shapes found in nature and predicts that at low plant rates the tussocks become unstable and collapse while at higher levels of plant vigour and sediment movement rates sedimentation occurs upslope of the tussock and erosion downslope these foci of sedimentation and erosion are crescent shaped and their relative importance depends on the splash factor

the crotone series a synthesis and new data the crotone series is undoubtedly the best studied early pleistocene succession in the world its matchless location and sedimentary conditions contribute to optimal achievements in biostratigraphy magnetostratigraphy cyclostratigraphy and finally chronology robust stratigraphic correlations are established between the semaforo and vrica areas thanks to field surveys a cored borehole and ash mineralogy and geochemistry the crotone series covers the time interval from 2 47 to 1 21 ma and displays 30 complete glacial interglacial cycles from mis 97 to mis 37 insolation cycles are recorded from i 236 to i 116 by combining lithology sapropels and palynology amorphous organic matter and abundance in pollen grains of riparian trees two indices of anoxic condition development and runoff intensity respectively the understanding of early pleistocene glacial interglacial pollen records is clarified as the response of vegetation to the strong interaction between precession and obliquity has been analysed along several successive climatic cycles modern pollen records from the rhone mouth shed light on the conditions of deposition of the sapropels contributing to specify their intensity and duration c 2010 elsevier ltd and inqua all rights reserved

variability of surface water characteristics and heinrich like events in the pleistocene midlatitude north atlantic ocean biomarker and xrd records from iodp site u1313 mis 16 9 1 a reconstruction of milankovitch to millennial scale variability of sea surface temperature sst and sea surface productivity in the pleistocene midlatitude north atlantic ocean marine isotope stage mis 16 9 and its relationship to ice sheet instability was carried out on sediments from integrated ocean drilling program iodp site u1313 this reconstruction is based on alkenone and n alkane concentrations u37k index total organic carbon toc and carbonate contents x ray diffraction data magnetic susceptibility and accumulation rates increased input of ice rafted debris occurred during mis 16 12 and 10 characterized by high concentrations of dolomite quartz and feldspars and elevated accumulation rates of terrigenous matter minimum input values of terrigenous matter on the other hand were determined for mis 13 and 11 peak values of dolomite coinciding with quartz plagioclase and kalifeldspar peaks and maxima in long chain n alkanes indicative for land plants are interpreted as heinrich like events related to sudden instability of the laurentide ice sheet during early and late deglacial phases of the glacials the coincidence of increased toc values with elevated absolute concentrations of alkenones suggests increased glacial productivity probably due to a more southern position of the polar front alkenone based sst reached absolute maxima of about 19 c during mis 11 3 and absolute minima of 10 c during mis 12 and 10 within mis 11 prominent cooling events mis 11 22 and 11 24 occurred the absolute sst minima recorded directly before and after the glacial maxima mis 10 2 and 12 2 are related to heinrich like event meltwater pulses as supported by the coincidence of sst minima and maxima in c37 4 alkenones and dolomite these sudden meltwater pulses especially during terminations iv and v probably caused a collapse of phytoplankton productivity as indicated by the distinct drop in alkenone concentrations ice sheet disintegration and subsequent surges and outbursts of icebergs and meltwater discharge may have been triggered by increased insolation in the northern high latitudes

orbital forcing of continental climate during the pleistocene a complete astronomically tuned climatic record from lake baikal se siberia abstract a new composite bdp 96 biogenic silica record over the entire pleistocene was generated by splicing bdp 96 1 and bdp 96 2 drill cores from lake baikal crosschecked against a similar record from a nearby bdp 98 drill core a new astronomically tuned age model is proposed based on correlating peak biogenic silica responses with the timing of september perihelia this target is derived from analysis of regional climate proxy responses during the holocene the last interglacial and around paleomagnetic reversals by resolving virtually every precessional cycle during the pleistocene the new age model represents a major improvement compared with previously reported lake baikal timescales the astronomically tuned ages of the pleistocene paleomagnetic reversals are consistent with published dates the minimal tuning approach we used precession only has also aligned high signal power in a narrow obliquity band confirming the strong presence of orbital forcing there are also strong ca 100 ka scale cycles but these are not aligned with the orbital eccentricity despite the location of lake baikal in a continental interior that is highly sensitive to insolation forcing the tuned biogenic silica record reveals a consistent phase difference of 32 ca 4 ka relative to insolation in the obliquity band an inherent lag embedded in a continental proxy record not driven by global ice volume is an intriguing finding another new observation is that long term changes in sedimentation rates in lake baikal appear to be related to the amplitude of orbital forcing both amplitudes and sedimentation rates undergo significant changes during mis 24 mis 19 interval corresponding to the middle pleistocene transition with potential for linking continental and marine climato stratigraphies the new baikal record serves a new benchmark correlation target in continental eurasia as an alternative to june 65 n insolation and odp correlated timescales

mechanisms of tidal oscillatory salt transport in a partially stratified estuary abstracttidal oscillatory salt transport induced by the correlation between tidal variations in salinity and velocity is an important term for the subtidal salt balance under the commonly used eulerian method of salt transport decomposition in this paper its mechanisms in a partially stratified estuary are investigated with a numerical model of the hudson estuary during neap tides when the estuary is strongly stratified the tidal oscillatory salt transport is mainly due to the hydraulic response of the halocline to the longitudinal variation of topography this mechanism does not involve vertical mixing so it should not be regarded as oscillatory shear dispersion but instead it should be regarded as advective transport of salt which results from the vertical distortion of exchange flow obtained in the eulerian decomposition by vertical fluctuations of the halocline during spring tides the estuary is weakly stratified and vertical mixing plays a significant role in the tidal variation of salin

calcareous plankton response to orbital and millennial scale climate changes across the middle pleistocene in the western mediterranean abstract the paleoenvironmental conditions through mis 15 9 at the mediterranean ocean drilling program odp site 975 were interpreted by high resolution study of calcareous plankton assemblages compared with available 18o and 13c records and high resolution paleoclimate proxies from the atlantic ocean sea surface temperatures ssts have been estimated from planktonic foraminiferal assemblages using the artificial neural networks method calcareous plankton varied dominantly on a glacial interglacial scale as testified by the sst record foraminiferal diversity total coccolith abundance and changes in warm water calcareous nannofossil taxa a general increase in foraminiferal diversity and of total coccolith abundance is observed during interglacials warmest ssts are reached during mis 11 while mis 12 and mis 10 represent the coldest intervals of the studied record during mis 12 one of the most extreme glacials of the last million years occurrence of globorotalia inflata and of neogloboquadrinids indicates a shoaling of the interface between atlantic inflowing and mediterranean outflowing waters among calcareous nannofossils the distribution of gephyrocapsa margereli gephyrocapsa muellerae 4 m also supports a reduced atlantic mediterranean exchange during mis 12 superimposed on glacial interglacial variability six short term coolings are recognized during mis 12 and 10 which appear comparable in their distribution and amplitude to the heinrich type events documented in the atlantic ocean in the same interval during these h type events neogloboquadrina pachyderma s and g margereli g muellerae 4 m increase as a response to the enhanced inflow of cold atlantic water into the mediterranean via the strait of gibraltar mediterranean surface water hydrography appears to have been most severely affected at termination v during the h type event ht4 possibly as a response to a large volume of atlantic meltwater inflow via the strait of gibraltar and or to freshwater terrigenous input deriving from local mountain glaciers three additional sst coolings are recorded through mis 14 16 but these are not well correlated with heinrich type events documented in the atlantic ocean in the same interval during these cooling episodes only the subpolar turborotalita quinqueloba increases these results highlight the sensitive response of the mediterranean basin to millennial scale climate variations related to northern hemisphere ice sheet instability and support the hypothesis that the tight connection between high latitude climate dynamics and mediterranean sea surface water features can be traced through the middle pleistocene

estuarine salt conservation a lagrangian approach abstract understanding tidal and mean flow transport mechanisms that maintain the estuarine salt balance against seaward transport by river flow is one of the fundamental questions of estuarine oceanography previous salt transport studies have failed to resolve this problem for two principal methodological reasons in addition to the inherent variability of estuaries first salt transport expansions used to represent the salt balance have included a large number of terms that could not be related to any theory of estuarine circulation and whose physical meaning was thus unclear second it has proven difficult to measure small mean velocities in the presence of much larger tidal variations a new analysis method that expresses lagrangian scalar property transport in terms of time and space variations of eulerian variables is much simpler than expansions previously used and yields new insights into estuarine transport processes this approach like previous expansions is valid for narrow systems in which cross channel transport processes are weak and the ratio of tidal amplitude to mean depth is small a surface boundary condition is used to eliminate one class of troublesome terms the equivalence of the tidal cycle average transport of tidal variations in salinity and the stokes transport of mean salinity is then employed to show that the vertically integrated tidal flow plays no role in the overall salt balance that is seaward transport of salt caused by the river flow can only be balanced by landward transport resulting from correlations between shear and stratification in the mean tidal and overtide flows in a hypothetical inviscid estuary tide and overtide flows would be vertically uniform and outward fluvial salt transport could only be balanced by shear and stratification in the mean gravitational circulation in a more realistic example with strong friction the gravitational circulation would be severely damped and inward transport could only be accomplished by correlations of shear and stratification in the tide and overtide flows

influence of vegetation distribution on sediment yield in forested marly gullies abstract the cover provided by forest vegetation makes it possible to fight erosion efficiently furthermore vegetation barriers can also play a major role by trapping eroded sediments and thus vegetation located downslope of a gully can be important the objective of this study is to highlight the role of vegetation distribution in a marly gully in reducing sediment loss at the outlet to do this sediment yield in gullies with similar geological and geomorphological components but with different vegetation cover and distribution was studied for 2 years sediment traps installed at gully outlets permitted the distinction of active gullies from inactive ones the results show that gully activity is not correlated with the percentage of total vegetation cover but with the percentage of cover of low vegetation in the gully floor this is due to sediment trapping processes and highlights the importance of the spatial distribution of forest vegetation in reducing sediment yield at the gully outlet thus gullies with similar total vegetation cover can have very different activities and inactive gullies exist that are only partially covered with vegetation inactive gullies with as low as 33 vegetation cover occur where vegetation is mainly present in the gully floor the results also show that above 50 cover of low vegetation in the gully floor as a percentage of the gully floor surface gullies are generally inactive

residual circulation in shallow estuaries 2 weakly stratified and partially mixed narrow estuaries long wave theory is used herein to analyze circulation in weakly stratified and partially mixed estuaries unlike the highly stratified systems considered in part 1 the flows considered here have only a minimal tidal frequency internal wave component these estuaries may therefore be modeled as the sum of weakly interacting barotropic and baroclinic modes the dominant factors driving the residual flow are finite amplitude barotropic effects in weakly stratified estuaries and a combination of barotropic effects and steady horizontal density gradient forcing in partially mixed estuaries the dominant vertical exchange mechanism in the weakly stratified case is bottom boundary induced turbulence and that in partially mixed estuaries is believed to be random internal wave interactions a model of the columbia river estuary under weakly stratified conditions accurately predicts the observed residual velocity and salinity fields and the tidal amplitude at which a transition to a highly stratified state takes place the partially mixed state is unstable in the columbia river estuary because the tides and buoyancy input are both too strong

phase lagged warming and the disruption of climatic rhythms during the matuyama brunhes magnetic polarity transition abstract the influence of the geomagnetic field on climate a long hotly disputed issue was examined for the matuyama brunhes mb magnetic polarity transition using palynological and paleomagnetic data sets from a high accumulation rate ca 50 cm kyr sediment core from osaka bay during the period from marine oxygen isotope stages mis 20 to 18 climate change is well correlated with global ice volume variation in the precession cycle with the exception of the early half of mis 19 the postglacial warming after substage 20 2 was interrupted by cooling that began just before the sea level highstand correlated with substage 19 3 and persisted until about a mid point between 19 3 and 19 2 followed by a rapid warming the thermal maximum clearly postdates the highest sea level highstand by 6 7 kyr and the connection between orbital forcing and climate was disrupted the cooling event coincided with the center of the paleointensity low during the mb transition this unusual climate cooling across a sea level peak is very likely related to the field intensity decrease the data from osaka bay may suggest an instance where the geomagnetic field has influenced climate in the past

foraminiferal record and environmental changes during the deposition of the early middle pleistocene sapropels in southern italy a foraminiferal investigation documents the palaeoenvironmental changes across the sapropel units associated with insolation cycles 90 and 86 in the early middle pleistocene im fosso 5 agosto section basilicata southern italy three benthic foraminiferal fossil associations associations a b and c identified by performing hierarchical cluster analysis on the quantitative data can be considered diagnostic of the palaeoenvironmental conditions before during and after the sapropel intervals they indicate a gradual decrease of bottom water oxygenation prior to the onset of sapropel deposition and a rapid return to stable environmental conditions at the end of the sapropel events the constant presence of benthic foraminifera throughout the sapropels implies that the bottom environment was not totally anoxic the high resolution distributional pattern of planktonic and benthic foraminifera within the sapropel associated with i cycle 90 documents a surface water cooling with consequent rapid re oxygenation of bottom waters that subdivides this interval in two phases both of them are characterized by an early subphase with warm climate conditions a decrease of salinity in surficial water layers and dominated by the low oxygen tolerant benthic species globobulimina affinis the late subphase shows thermal stratification during summer and a relatively deep and oxygenated mixed layer during winter in this subphase the contemporaneous replacement of g affinis the bless opportunistic but more resistant to low oxygen conditionsq species with bolivina alata bolivina dilatata and brizalina spathulata the bless resistant to low oxygen conditionsq species indicates the relative oxygen improvement in sediment pore water the frequent changes detected in the sapropel associated faunal composition underline the unstable nature of bottom water oxygen content d 2004 elsevier b v all rights reserved

vegetation response to obliquity and precession forcing during the mid pleistocene transition in western mediterranean region odp site 976 abstract the odp leg 161 site 976 alboran sea is a deep sea section sampled at a water depth of 1108 m in the western mediterranean sea pollen analysis provides a vegetation and climate record of the mid pleistocene transition mpt roughly one million years ago the age model tied to biostratigraphic events was revised by aligning the pollen climate index pci to mediterranean kc01b and global lr04 oxygen isotope records the studied time slice spans the interval 1 09 ma mis 31 to 0 90 ma mis 23 across this interval past phytogeography of nowadays extinct taxa which were rare allows a successful application of the modern analogues technique mat to quantitative climate reconstructions for the mpt five long term obliquity related vegetation successions o1 to o5 and eight short term precession related vegetation successions p1 to p8 are observed within the studied interval these vegetation successions regardless of their duration show the same pattern the progressive replacement of temperate trees by mountainous taxa and then by herbs and steppe maxima precession related successions correspond therefore to as dramatic vegetation changes as those driven by obliquity including a final steppe phase under deteriorated climate conditions wavelet analysis of the pci record shows that the western mediterranean experienced a shift at 1 01 ma from precession dominated frequencies 1 05 1 01 ma to obliquity dominated frequencies 1 01 0 9 ma there is therefore an apparent discrepancy between wavelet analysis results and vegetation dynamic analysis which suggests that obliquity and precession are recorded throughout the entire studied interval this discrepancy could result from the fact that the pci record sums somehow similar vegetation changes wet to dry occurring at different periodicities such a complex vegetation dynamics is mathematically rendered through a single parameter i e principal component which does not successfully catch the subtle combinations of variability occurring at two close periodicities furthermore the pollen inferred early pleistocene vegetation dynamic and climate of the western mediterranean region does not show a decrease of the obliquity response relative to the precession response at the onset of the mpt

three million years of monsoon variability over the northern sahara we present a 3 million year record of aeolian dust supply into the eastern mediterranean sea based on hematite contents derived from magnetic properties of sediments from ocean drilling program site 967 our record has an average temporal resolution of 400 years geochemical data validate this record of hematite content as a proxy for the supply of aeolian dust from the sahara we deduce that the aeolian hematite in eastern mediterranean sediments derives from the eastern algerian libyan and western egyptian lowlands located north of the central saharan watershed 21 n in corroboration of earlier work we relate dust flux minima to penetration of the african summer monsoon front to the north of the central saharan watershed this would have enhanced soil humidity and vegetation cover in the source regions in agreement with results from green sahara climate models our results indicate that this northward monsoon penetration recurred during insolation maxima throughout the last 3 million years as would be expected this orbital precession scale mechanism is modulated on both short 100 kyr and long 400 kyr eccentricity time scales we also observe a strong expression of the 41 kyr obliquity cycle which we discuss in terms of high and low latitude mechanisms that involve southern hemisphere meridional temperature contrasts and shifts in the latitudes of the tropics respectively we also observe a marked increase in sub milankovitch variability around the mid pleistocene transition 0 95 ma which suggests a link between millennial scale climate variability including monsoon dynamics and the size of northern hemisphere ice sheets

the cow as a geomorphic agent a critical review cows are important agents of geomorphological change on the uplands heavy grazing compacts the soil reduces infiltration increases runoff and increases erosion and sediment yield however light and moderate grazing have effects that are much less significant in riparian zones grazing decreases erosional resistance by reducing vegetation and exposing more vulnerable substrate trampling directly erodes banks thus increasing turbulence and consequent erosion future studies should be framed within the hydroclimatological edaphic and geomorphological dimensions of the areas being studied so that controlling variables may be more readily isolated we believe that both empirical studies and deterministic modeling can provide insights as to the effects of grazing on geomorphology

paleoenvironmental changes during sapropel 19 i cycle 90 deposition evidences from geochemical mineralogical and micropaleontological proxies in the mid pleistocene montalbano jonico land section southern italy an integrated micropaleontological geochemical and mineralogical study has been performed across the mid pleistocene sapropel 19 i cycle 90 from the montalbano jonico land section southern italy to reconstruct the paleoenvironmental conditions at time of its formation the sapropel interval is characterized by two oxygen depletion phases phase a and c interrupted by a temporary re oxygenation interval phase b the beginning and the end of sapropel deposition are dated at 957 0 81 kyr and 950 0 86 kyr respectively the duration of the interruption is estimated to 0 350 0 32 kyr the multiproxy approach highlights that deposition of sapropel 19 reflects a period of enhanced freshwater runoff induced by a wetter climate as a consequence of a more efficient fluvial erosion a higher terrigenous input mostly ascribable to a southern apennines source and an increased turbidity of surface waters accompanied most of sapropel deposition biotic and abiotic proxies document that different paleoenvironmental conditions occur through phases a c the beginning of phase a is characterized by warm on land paleoclimate as well as warm and oligotrophic surface water conditions during the upper part of phase a temperature starts decreasing and surface waters appear more productive this change probably represents the prelude to cooler and drier conditions characterizing phase b which displays a river supply reduction and an eolian input increase sahara dust during phase c the restored depleted oxygen environment at the bottom sediments is clearly coupled with the re establishment of humid conditions and increased river supply at the same time enhanced mixing of water column a cooler paleoclimate and increased productivity of surface waters are recorded the latter likely favored by the enhanced mixing of water column and also increased delivery of land derived nutrients the end of phase c is marked by a restored normal run off enhanced productivity in surface waters and low oxygen conditions at the bottom sediments persist slightly above phase c the overall results suggest that the onset of sapropel deposition is related to water stratification that caused low oxygen exchanges with the sea bottom although enhanced productivity characterizes most of the sapropel deposition it was not the primary factor triggering sapropel deposition

on tide induced lagrangian residual current and residual transport 2 residual transport with application in south san francisco bay california the transports of solutes and other tracers are fundamental to estuarine processes the apparent transport mechanisms are convection by tidal current and current induced shear effect dispersion for processes which take place in a time period of the order of a tidal cycle however as emphasis is shifted toward the effects of intertidal processes the net transport is mainly determined by tide induced residual circulation and by residual circulation due to other processes the commonly used intertidal conservation equation takes the form of a convection dispersion equation in which the convective velocity is the eulerian residual current and the dispersion terms are often referred to as the phase effect dispersion or sometimes as the tidal dispersion the presence of these dispersion terms is merely the result of a fickian type hypothesis since the actual processes are not fickian thus a fickian hypothesis obscures the physical significance of this equation recent research results on residual circulation have suggested that long term transport phenomena are closely related to the lagrangian residual current or the lagrangian residual transport in this paper a new formulation of an intertidal conservation equation is presented and examined in detail in a weakly nonlinear tidal estuary the resultant intertidal transport equation also takes the form of a convection dispersion equation without the ad hoc introduction of phase effect dispersion in a form of dispersion tensor the convective velocity in the resultant equation is the first order lagrangian residual current the sum of the eulerian residual current and the stokes drift the remaining dispersion terms are important only in higher order solutions they are due to shear effect dispersion and turbulent mixing there exists a dispersion boundary layer adjacent to shoreline boundaries an order of magnitude estimate of the properties in the dispersion boundary layer is given the present treatment of intertidal transport processes is illustrated by an analytical solution for an amphidromic system and by a numerical application in south san francisco bay california the present formulation reveals that the mechanism for long term transport of solutes is mainly convection due to the lagrangian residual current in the interior of a tidal estuary this result also points out the weakness in the tidal dispersion formulation and explains the large variability of the observed values for tidal dispersion coefficients further research on properties of the dispersion boundary layer is needed

mounds associated with shrubs in aridic soils of northeastern patagonia characteristics and probable genesis abstract studies of mounds associated with shrub clumps in northeastern patagonia indicate that these forms have an average major diameter of 355 cm and an average height of 41 cm mound cover and density are 40 and 450 mounds ha respectively mound and intermound soils present a similar textural composition as well as a similar coarse fragment content 10 20 root and organic matter contents are significantly higher whereas calcium carbonate is significantly lower in the mound than in the intermound soils mounds may represent a relict land surface level lowered in the intermound area mainly by wash erosion mound development is related to discrete shrub clumps that shelter the underlying soil once established the shrub clump and the underlying mound remain as a stable and self maintained system

vegetation changes during the late early pleistocene at montalbano jonico province of matera southern italy based on pollen analysis pollen analysis of the early pleistocene montalbano jonico section in southern italy reveals cyclic changes driven by climate and eustasy as illustrated by mesothermic vs steppe elements for climate and pinus vs caryophyllaceae amaranthaceae chenopodiaceae and ephedra for eustasy these results are directly compared with oxygen isotope data on globigerina bulloides constrained within a biostratigraphic framework based on nannofossils and foraminifers facilitating a new age calibration for the section marine isotopic stages 37 to 23 1 250 0 900 ma are recorded and compared with global and mediterranean oxygen isotope curves high frequency changes in pollen are related to the mediterranean curve globigerinoides ruber from odp site 967 and superimposed the lr04 stack curve during the early pleistocene pollen recorded global and regional climate changes related to obliquity and precession respectively and regional tectonic evolution precession forcing was caused by mediterranean wetness related to precession the intensified precession effect over climatic cycles that is expected during the middle pleistocene transition is not recorded in the montalbano jonico interval a vegetation changes

climatic patterns revealed by pollen and oxygen isotope records across the matuyama brunhes boundary in the central mediterranean southern italy a c 50 m thick section located in the crotone basin southern italy was investigated using oxygen isotopes pollen and planktonic foraminifera the section records two complete trans gressive regressive cycles mainly driven by glacio eustasy biostratigraphy and oxygen isotope chronology indicate that the section spans from marine isotope stage mis 22 c 0 87 ma to mis 18 3 c 0 73 ma thus straddling the matuyama brunhes m b boundary which occurs in the middle of mis 19 the rich pollen assemblages provide a unique record of the vegetation in the central mediterranean during the early middle pleistocene climatic transition interglacials are characterized by a mesothermic vegetation similar to the present day whereas a rain demanding conifer forest dominates the glacials of mis 20 and mis 18 this is unexpected because it is gener ally considered that during the pleistocene glacials in central mediterranean were characterized by steppe arid conditions by contrast arid conditions occur during the deglaciations these results are inconsistent with the widespread practice of linking glacials with arid conditions in the central mediterranean during pliocene and early pleistocene times this study emphasizes the need to establish more accurate land sea correlation

observations of turbulence in a partially stratified estuary the authors present a field study of estuarine turbulence in which profiles of reynolds stresses were directly measured using an adcp throughout a 25 h tidal day the dataset that is discussed quantifies turbulent mixing for a water column in northern san francisco bay that experiences a sequence of states that includes a weak ebb and flood that are stratified followed by a strong and eventually unstratified ebb and flood these measurements show that energetic turbulence is confined to a bottom mixed layer by the overlying stratification examination of individual reynolds stress profiles along with profiles of richardson number and turbulent froude number shows that the water column can be divided into regions based on the relative importance of buoyancy effects using the measured turbulence production rate p the dissipation rate e is estimated the observed turbulence had values of e nn 2 20 all of the time and e nn 2 200 most of the time suggesting that the observed motions were buoyancy affected turbulence rather than internal waves however at times turbulent froude numbers in much of the upper water column were less than one indicating important stratification effects taken as a whole the data show that stratification affects the turbulent velocity variance q2 most severely that is observed reductions in u9w9 are largely associated with small values of q2 rather than with a dramatic reduction in the efficiency with which turbulent motions produce momentum fluxes finally the dataset is compared to predictions made using the popular mellor yamada level 2 5 closure these comparisons show that the model tends to underestimate the turbulent kinetic energy in regions of strong stratification where the turbulence is strongly inhomogeneous and to overestimate the turbulent kinetic energy in weakly stratified regions the length scale does not appear to compensate for these errors and as a result similar errors are seen in the eddy viscosity predictions it is hypothesized that the underestimation of q2 is due to an inaccurate parameterization of turbulence self transport from the near bed region to the overlying stratification

latest olduvai short lived reversal episodes recorded in chinese loess 1 a duplicate high resolution magnetic record was obtained from two parallel loess sections separated by about 300 m near baoji city southern chinese loess plateau this reveals at least eight short lived reversed polarity episodes in the uppermost part of the olduvai normal polarity subchronozone rock magnetic experiments and anisotropy of low field magnetic susceptibility confirm that the multiple occurrence of short lived reversals is not due to rock magnetic and or sedimentary causes assuming a constant accumulation rate within the olduvai subchron the short episode zone was estimated to span about 24 30 ka and 24 31 ka for the two sections respectively the duration of each short episode ranges from about 0 3 ka to 2 1 ka the present results together with previous worldwide observations show that the occurrence of numerous short reversals is peculiar to the latest olduvai subchron the geodynamo may have been in an anomalous state at that time

paleoenvironmental and climatostratigraphic insights for marine isotope stage 19 pleistocene at the montalbano jonico succession south italy abstract quantitative analyses on pollen and ostracods were performed on the montalbano jonico succession mjs through marine isotope stages mis 18 21 in order to acquire details of paleoenvironmental changes and climate pattern during mis 19 which includes the matuyama brunhes paleomagnetic boundary mbb while the mjs does not record the mbb which is the main criterion for defining the early middle pleistocene boundary it is a candidate global boundary stratotype section and point gssp for the ionian stage and middle pleistocene subseries because of its excellent exposure continuous deposition and astronomically tuned record between mis 37 and mis 16 the new 40ar 39ar age of 773 9 1 3 ka for volcaniclastic layer v4 allows the age model for the succession to be refined ostracod assemblages show significant paleodepth fluctuations at the glacial interglacial scale in agreement with the pollen distality index pinus vs caryophyllaceae amaranthaceae and ephedra which also suggests higher values during mis 19 pollen analysis provides supplementary paleoclimate data that are valuable to reconstruct temperature variation during the identified phases a major expansion of steppic vegetation at 790 ka in the uppermost mis 20 correlates with a significant cold and arid northern hemisphere climate phase as documented by a concurrent peak both in north atlantic ice rafted debris and mediterranean dust records climate conditions recorded in mis 19 3 were similar to those of the present interglacial whereas a dry climate phase marks mis 19 2 at 771 84 ka slightly above the v4 layer millennial scale climate variability occurred during mis 19 as evidenced by two abrupt short term moderately dry pollen events at 783 5 ka and 774 8 ka that could be related to a period of reduced geomagnetic field intensity through the mbb transition additional environmental chronological events accompanied this stratigraphic interval i the volcaniclastic layers v3 and v4 radiometrically dated at 801 2 19 5 ka and 773 9 1 3 ka respectively ii the co occurrence of maximum flooding and thermal maximum in agreement with the previously recorded co occurrence of the neopycnodonte community and tropical subtropical mesopelagic teleostean bonapartia pedaliota close to the increase of quercus and iii the maximum depth md between 777 3 and 773 25 ka as recorded by outer shelf upper slope macroinvertebrate fauna close to the highest value of pollen distality index in mis 19 results enhance the understanding of orbital suborbital paleoenvironmental change during the mid pleistocene and particularly of the climate pattern during mis 19 and across the mbb

biogeomorphological influence of slope processes and sedimentology on vascular talus vegetation in the southern cascades california abstract the vascular vegetation of alpine talus slopes between 2035 and 3095 m altitude was studied at lassen volcanic national park california in the cascade range taluses show a diverse flora with 79 plant species growth forms include coniferous trees shrubs suffrutices herbs graminoids and ferns spatial patterns of plant distribution were studied along 40 point intercept transects plant cover was low 0 32 7 on all slopes spatially variable and showed no consistent trends sedimentological characteristics were determined by photosieving next to 1500 plants this census indicated preferential plant growth on blocks and cobbles with 43 2 and 23 3 of the plants growing on these stones respectively fewer specimens were rooted on pebbles 13 or on stone free gravel areas 20 5 growth forms displayed different substrate preferences 92 5 of the shrubs and 83 of the suffrutices colonized blocks or cobbles but only 57 2 of the herbs and 59 8 of the graminoids grew on large stones plants are associated with large clasts because 1 coarse talus is more stable than fine sediment areas which are more frequently disturbed by various geomorphic processes and 2 large stones help conserve substrate water beneath them while moisture quickly evaporates from fine debris root patterns were studied for 30 plant species 10 specimens for each species were excavated and inspected and several root growth ratios calculated all species exhibited pronounced root asymmetry as roots for most plants grew upslope from their shoot base for 23 species all specimens had 100 of their roots growing upslope for the other 7 species 92 2 99 3 of below ground biomass extended uphill this uneven root distribution is ascribed to continual substrate instability and resulting talus shift as cascading debris progressively buries roots and stems plants are gradually pushed and or stretched downhill various disturbance events affect root development slope erosion following rubble removal often exposes plant roots debris deposition can completely bury plants some may survive sedimentation producing new shoots that grow through accumulated debris shrubs may propagate by layering as adventitious roots develop along buried stems or produce new clones along their roots slope processes may damage and transport plant pieces downhill some species can sprout from severed displaced root or stem fragments vegetation interacts with several geomorphic processes including debris flows grain flows rockfall snow avalanches frost creep and runoff larger plants may alter local patterns of debris movement and deposition damming cascading debris on their upslope side and deflecting sediments laterally to plant margins where they form narrow elongated stone stripes

subdividing the pleistocene using the matuyama brunhes boundary mbb an australasian perspective abstract the last major reversal of the earth s magnetic field the matuyama brunhes boundary mbb dated at 0 78 ma is widely identified in australian and new zealand pleistocene deposits in new zealand the mbb is precisely located in shallow marine sediments of wanganui basin where it corresponds with the base of the new zealand putikian substage a combination of marine biostratigraphy sequence stratigraphy and tephrostratigraphy permit correlation from wanganui basin to other on land sections and deep sea cores in australia the mbb is identified in many continental sequences particularly saline lake basins however chemical weathering has resulted in variable brunhes age normal overprints that are sometimes difficult to remove australasian tektites are a potential lithostratigraphic marker just prior to the mbb but have yet to be identified in the same on land section as the mbb in australia identification of reverse polarity magnetisation in weathered deposits including soils provides a minimum age of 0 78 ma for these materials a widespread arid shift in paleoclimate succeeded the mbb in australia placement of the lower middle pleistocene boundary at the mbb would constitute the most recognisable chronostratigraphic marker in weathered continental deposits

paleomagnetic record at odp site 980 feni drift rockall for the past 1 2 myrs 1 a detailed record of variations in the direction and intensity of the geomagnetic field over the past 1 2 myrs has been obtained from an 120 m thick sedimentary section cored at odp site 980 on the feni drift north atlantic the record has high resolution due to high mean sedimentation rates 11 3 cm kyr for the brunhes chron and 5 5 cm kyr for the matuyama chron paleomagnetic measurements every 1 cm along u channel samples and high quality isotopic age control the iceland basin event is manifest by virtual geomagnetic poles crossing the equator at 190 ka the base of the recovered section lies immediately below the cobb mountain subchronozone that occurs within marine isotope stage 35 normalized remanence data can be correlated to paleointensity records from odp sites 983 and 984 700 km to the nw from site 980 and with lower resolution paleointensity data from the pacific ocean differences between the site 980 paleointensity record and the pacific records are attributed to variable sedimentation rates variable quality age control and inadequacies in the normalization procedure used to derive the paleointensity proxies

the site of coste san giacomo early pleistocene central italy palaeoenvironmental analysis and biochronological overview abstract facies and ostracod analyses have been performed on a continental core drilled at coste san giacomo anagni central italy where a middle villafranchian faunal assemblage was first discovered in 1978 the core intercepted the palaeontological level and penetrated the underlying sedimentary succession previously largely unknown for a total sediment recovery of 40 m in addition new field surveys led to the discovery of hippopotamus sp remains at the faunal site thus pre dating the dispersal of this large ungulate into europe to the middle villafranchian the new sedimentological and palaeoecological data allowed to define a palaeoenvironment mainly ascribable to an alluvial plain characterized by a marsh evolving into a floodplain with overbank deposits and a sand bed fluvial channel this scenario is supported by the reassessed coste san giacomo faunal assemblage consistent with running and or clear waters as well as prairies and grasslands under mild climatic conditions

geomagnetic palaeointensities and astrochronological ages for the matuyama brunhes boundary and the boundaries of the jaramillo subchron palaeomagnetic and oxygen isotope records from odp site 983 we have measured relative geomagnetic palaeointensity proxies palaeomagnetic directions and 18 o for the 700 1100 ka interval from odp site 983 gardar drift north atlantic where mean sedimentation rates are ca 13 cm kyr 1 the age model was generated by matching the benthic 18 o data to the ice volume model and confirmed by tuning the precessional components of both signals for the matuyama brunhes boundary mbb and the boundaries of the jaramillo subchronozone the duration of the polarity reversal process defined by virtual geomagnetic polar latitudes of less than 45 is ca 5 kyr whereas the generally accepted astrochronological estimates for the boundaries of the jaramillo subchronozone lie within the polarity transitions as recorded at site 983 the astrochronological age for the matuyama brunhes polarity transition 780 ka is ca 5 kyr older than the onset of this transition at site 983 775 ka the polarity reversals lie within palaeointensity lows with abrupt recovery of palaeointensity post reversal there is no progressive sawtooth decrease in palaeointensity within the jaramillo subchronozone or between the top of the jaramillo and the mbb but rather within polarity chrons several short intervals of low palaeointensity which sometimes coincide with high amplitude secular variation orbital 100 and 41 kyr periods are present in the palaeointensity record as they are not obviously attributable to climate lithology in these records they may be a feature of the geomagnetic field itself

relative efficiency of three representative matorral species in reducing water erosion at the microscale in a semi arid climate valencia spain abstract in the mediterranean region where rainfall is scarce but often of high intensity the matorral vegetation cover provides essential protection to the soil against the erosivity of rainfall and reduces considerably the water erosion rate three representative species of the mediterranean matorral displaying different morphologies rosmarinus officinalis l stipa tenacissima l anthyllis cytisoides l were selected for study at the microscale plant scale for their relative efficiency in reducing water erosion on slopes the mechanical protection of the soil against raindrop detachment and the improvement of the soil properties by the biological influence of an isolated plant were compared for the three species the quantification of interrill erosion and splash erosion rates under natural rainfall conditions was obtained using erosion microplots of individual plants and splash cups placed at different distances from the plant axis respectively soil samples were also taken in the microenvironment of the plants in order to evaluate possible differential influences of the three species on soil properties relevant to water erosion the results show that the three selected species reduced runoff and soil loss in different ways the screen effect arising from the very dense canopy of stipa tussocks represents an effective way to counteract rainfall erosivity and reducing splash erosion however in the case of rosmarinus in addition to the mechanical protection offered by its canopy and litter covers the latter which lies permanently at the soil surface under the plant canopy improves moreover the topsoil structure because of the important incorporation of organic matter below the canopy cover the role of litter cover in controlling erosion seems therefore to be predominant under rosmarinus as for anthyllis these deciduous shrubs provide little physical protection against the energetic impact of rain at the soil surface as compared to a bare surface nevertheless the three plant species have a positive influence on their microenvironment through the improvement of soil properties under their canopy thus in open matorral patchy vegetation fertile soil islands developed below the plant canopy these differ considerably from the bare soil inter plant areas that give rise to higher soil loss rates

abrupt climate events 500 000 to 340 000 years ago evidence from subpolar north atlantic sediments subpolar north atlantic proxy records document millennial scale climate variations 500 000 to 340 000 years ago the cycles have an approximately constant pacing that is similar to that documented for the last glacial cycle these findings suggest that such climate variations are inherent to the late pleistocene regardless of glacial state sea surface temperature during the warm peak of marine isotope stage 11 mis 11 varied by 0 5 to 1 c less than the 4 to 4 5 c estimated during times of ice growth and the 3 c estimated for glacial maxima coherent deep ocean circulation changes were associated with glacial oscillations in sea surface temperature

lower middle pleistocene ostracod assemblages from the montalbano jonico section basilicata southern italy abstract the montalbano jonico section is a pleistocene sequence about 450 m thick comprising silty clays and silty sands deposited during the upper part of the calabrian stage and lower part of the ionian stage it is a candidate global boundary stratotype section and point for the middle pleistocene subseries ostracod assemblage analyses were carried out on 40 samples from the uppermost levels of the lower pleistocene and the lowermost part of the middle pleistocene with the aim of reconstructing the paleoenvironmental evolution around the matuyama brunhes boundary taxonomic investigations quantitative distribution data and statistical analysis q mode cluster analysis define four intervals correlated with sea level changes linked to marine isotope stages mis 21 18 the lower part of the section ranging from 864 00 to 820 00 ka was deposited in an outer shelf paleoenvironment during a period of high sea level associated with mis 21 the transition to the second interval 815 42 785 62 ka is marked by a shallowing trend reflecting the mis 20 decrease in sea level the overlying part of the section 783 54 749 91 ka yielded assemblages indicating a return to deeper water conditions corresponding to the warm phase mis 19 the uppermost interval was deposited during 746 60 740 54 ka when cooling in mis 18 produced a sea level drop here some levels 164 20 m 745 51 ka 170 10 m 743 05 ka 176 10 m 740 54 ka show the presence of both deep and shallow autochthonous taxa suggesting the occurrence of upwelling episodes during this cold phase in some layers deposited during warm stages the ostracod assemblages indicate the presence of kenoxic bottom waters the lowest paleo oxygen levels are correlated with marine isotope substages 21 3 and 19 1

revised tuning of ocean drilling program site 964 and kc01b mediterranean and implications for the δ18o tephra calcareous nannofossil and geomagnetic reversal chronologies of the past 1 1 myr 1 high resolution color reflectance records of kc01 and kc01b calabrian ridge ionian sea are presented and compared with a modified spliced high resolution color reflectance record of ocean drilling program odp site 964 this comparison revealed that kc01b is characterized by intensive deformation between 27 and 28 5 m piston depth and that some sapropels are tectonically reduced in thickness moreover the piston coring has caused considerable stretching in the top of kc01 and kc01b using a new splice of odp site 964 as guide previous astronomical tuned timescales of kc01b and odp site 964 were evaluated this evaluation resulted in a new sapropel based astronomical timescale for the last 1 1 myr the new timescale implies a much more uniform change in sedimentation rate for the ionian sea cores two prominent excursions to lighter values in the 18o record of the planktonic foraminiferal species globigerinoides ruber occur during marine isotopic stages 12 and 16 applying the new timescale these shifts correspond with maxima in obliquity and are punctuated by minima in the precession cycle they are absent in global ice volume records and are interpreted as reflecting a summer low salinity surface water lens that floats on top of extremely saline intermediate and deep waters at times of the very low sea levels during these glacial periods all biostratigraphic and magnetostratigraphic events found in kc01b and odp site 964 were re dated according to the new timescale and the ages of 33 tephra layers were reviewed the new ages for the calabrian ridge 2 and 3 magnetic events in the brunhes are concordant with minima in the global sint800 composite record derived from worldwide deep sea records of relative paleointensity and have been attributed to the big lost and la palma excursions respectively

a study of non linear tidal propagation in shallow inlet estuarine systems part i observations the offshore tide becomes strongly distorted as it propagates into shallow estuarine systems observations of sea surface elevation and horizontal currents over periods ranging from three days to one year at nine stations within nauset inlet estuary document the non linear interaction of the off shore equilibrium tidal constituents despite strong frictional attenuation within the estuary the overtides and compound tides of m2 s2 and n2 in particular reach significant amplitude resulting in strong tidal distortion high frequency forced constituents in sea surface are phase locked consistently leading the forcing tides by 60 70 resulting in a persistent distortion where falling tide is longer than rising tide forced constituents in currents are more nearly in phase with equilibrium constituents producing flood currents which are shorter but more intense than ebb currents a compound fortnightly tide msf modulates the mean water level such that lowest tides occur during neap phase instead of spring phase this fortnightly tide can be contaminated by storm surge changing the phase characteristics of this constituent implications of the overtides compound tides and lower frequency tides on near bed suspended and dissolved material transport are profound

phytogenic mounds of four typical shoot architecture species at different slope gradients on the loess plateau of china abstract in semi arid regions the spatial pattern of vegetation usually appears as a mosaic of plants surrounded by bare soil phytogenic mounds often develop under these plants and create microenvironments that promote plant establishment this study examined the effects of ground slope and plant shoot architecture on mound formation four species representing different shoot architectures artemisia gmelinii with dense shoot architecture artemisia giraldii with expanding shoot architecture tussock forming bothriochloa ischaemum and sophora viciifolia with a main stem shoot architecture and four classes of slope were selected a two dimensional microprofilemeter was used to measure mound shape and height and mound area was measured using the image pro plus software with a planer mound picture phytogenic mound shapes changed from symmetrical mound type to asymmetrical terrace type as slope increased with increasing slope mound height increased for all species the mound area of s viciifolia decreased and that of a giraldii increased a gmelinii and b ischaemum had a relatively constant mound area irrespective of slope among the plant shoot architecture parameters the basal diameter along the slope d ba significantly correlated with mound height while the plant basal diameter perpendicular to the slope d bp and the total cross sectional area of the stem at the base s n were related to mound area the results indicate that phytogenic mounds on gentler slopes are formed due to the difference in rain splash erosion beneath the plant canopy and surrounding bare surfaces on steeper slopes mounds are formed due to water erosion on bare soil and the prevention of erosion and sediment accumulation under plants plant shoot architecture also influences mound formation species with expanding shoot architecture such as a giraldii that spread laterally to create high density stems and occupy a large area can create relatively large mounds species with main stem shoot architecture such as s viciifolia have a mound area that shrinks rapidly with increasing slope

runoff generation sediment movement and soil water behaviour on calcareous limestone slopes of some mediterranean environments in southeast spain abstract an interpretation of soil hydrology and erosion data obtained from limestone areas in southeast spain is presented in the framework of recent hypotheses on runoff generation mechanisms in mediterranean environments the main objective is to synthesise and harmonise the data in theoretical concepts or behavioural models of hydrological functioning of mediterranean limestone slopes for this purpose data were collected in a typical limestone area with climatic characteristics ranging from subhumid to semiarid several sites were chosen with comparable slopes vegetation and soils along a transect of 20 km to carry out several research projects the data discussed in this paper consist of information on water redistribution within the soil profiles obtained from long duration up to 5 h rainfall simulation experiments with continuous monitoring of soil moisture at different depths runoff and sediment concentration data were obtained i from rainfall simulation experiments with different antecedent soil moisture conditions and ii as natural results from open gerlach plots on runoff and sediment movement over 4 years three conceptual models of water redistribution during the infiltration process could be observed two of them imply nonuniform water redistribution within the soil profile due mainly to macropore flow caused by specific soil surface characteristics at the plot scale runoff generated in bare patches is mainly hortonian in plots with previously wetted soils or soils with high infiltration capacities the generated runoff implies the saturation of the upper soil both types of runoff are discontinuous through time and space the runoff generation mechanisms at the slope scale have been synthesised into two conceptual models a hortonian discontinuous runoff model that takes place in the most degraded slopes or during high intensity rain events and a mixed runoff generation model in less degraded slopes or in previously wet soils where infiltration excess runoff as well as saturation excess runoff can happen on the same slope in both cases slopes behave as a patchwork of runoff and runon areas the size of the runoff or runon patches is dependent on the climatological conditions these control the hydrological disconnection between different parts of the slopes hortonian and saturation runoff can both be generated and infiltrated downslope

the contributions of biogeomorphology to the emerging field of geobiology biogeomorphology has developed into a well established research field over the past 15 years with studies examining a range of two way interrelations between organisms and geomorphology in a variety of terrestrial and marine environments this paper starts by defining the core biogeomorphological processes bioerosion bioprotection and bioconstruction particular emphasis is placed on the study of bioconstructional forms providing a clear definition examples of bioconstructions and crucially examining important interactions between bioconstruction and bioerosion three key areas where biogeomorphological research can directly contribute to the emerging field of geobiology are identified 1 the use of biogeomorphological approaches combined with palaeoecological investigations and predictive modelling in the growing field of carbon sequestration and climate change mitigation 2 providing geomorphological expertise to support the emerging field of astrobiology and 3 the potential contributions of biogeomorphology to the blossoming field of bio geoengineering some key research directions and challenges for future biogeomorphological research include exploring how biogeomorphological studies can contribute to and benefit from collaborations with other fields of geobiology and assisting in the development of a useful effective interdisciplinary toolbox of methods to improve quantification of geobiological processes importantly suggestions are made for potentially fruitful collaborations with geomicrobiologists geochemists and palaeoecologists

millennial to submillennial scale features of the matuyama brunhes geomagnetic polarity transition from osaka bay southwestern japan 1 a high resolution magnetic record of the matuyama brunhes mb reversal transition was obtained from homogeneous marine clay in a 1700 m core from osaka bay the transition stretches over a core length of 6 4 m and yields four short reversal episodes two predate the main mb boundary mbb and two postdate it we made diatom analyses of sediments to estimate relative sea level changes and constructed an age model by correlation with the astronomically calibrated marine oxygen isotope curve the age model shows the short reversal episodes with durations of 1 kyr occurred at 4 5 kyr intervals within stage 19 and the mbb occurred about 5 kyr after the sea level highstand corresponding to isotopic event 19 3 it also shows the paleointensity minimum of 15 20 of the postreversal mean occurred at about 6 kyr before the mbb and another minimum at about 1 kyr after four virtual reverse to normal polarity boundaries found in this study suggest different ages for the mbb could be observed in lava flow studies some millennial to submillennial scale transition features found in this study are compatible with the previous numerical simulations of geomagnetic field reversal

influence of alpine plants growing on steep slopes on sediment trapping and transport by runoff abstract understanding the interactions between soil and the organisms that are conducive to decreasing sediment runoff is a great concern on high elevation ski trails intense rainfalls on steep slopes combined with soil formed on gypsum result in recurrent erosion this study was conducted in the northern french alps to determine the abilities of species 1 to make mounds and 2 to trap sediment and thereby to control erosion at the slope scale we also investigated relevant above ground plant characteristics related to those abilities sediment runoff or deposition was investigated at small and large spatial scales we assessed whether hoof prints in soil reflect sediment runoff at the slope scale by trapping sediment populations of plants growing on two slope angles 25 and 35 and three vegetation cover densities 15 35 60 were surveyed an experiment was also conducted to measure the sediment deposit upslope of target species and over three months during the autumn small mounds were found upslope of the plant and sediment deposit measurements showed that they resulted from a sedimentation process nevertheless the species differed in their capacity to make mounds sesleria caerulea and festuca alpina had the highest amount of sediment deposition over the experimental period among the plant characteristics plant length was positively correlated with mound area while the roundness index of the canopy was negatively correlated with mound height mound formation was also positively related to the number of tillers or shoots sediment accumulation in cow hoof prints was linked to runoff that occurred at the slope scale low deposition in hoof prints means low sediment runoff or a large deposition on mounds due to the increase in vegetation cover all the findings stressed that understanding the processes in action at larger scales requires studying processes at smaller scales

10 be evidence for the matuyama brunhes geomagnetic reversal in the epica dome c ice core every few hundred thousand years earth s north and south magnetic poles swap places for the first time a record of one of these geomagnetic reversals has been found in an ice core because the strength of the field is very low during a reversal the intensity of cosmic rays in the earth s atmosphere is increased this leads to an increase in the quantity of 10be which like 14c is formed by cosmic rays in the atmosphere deposited in the ice it is this 10be enhancement in the ice that has been detected an ice core drilled at dome c antarctica is the oldest ice core so far retrieved1 on the basis of ice flow modelling and a comparison between the deuterium signal in the ice with climate records from marine sediment cores the ice at a depth of 3 190 m in the dome c core is believed to have been deposited around 800 000 years ago2 offering a rare opportunity to study climatic and environmental conditions over this time period however an independent determination of this age is important because the deuterium profile below a depth of 3 190 m depth does not show the expected correlation with the marine record2 here we present evidence for enhanced 10be deposition in the ice at 3 160 3 170 m which we interpret as a result of the low dipole field strength during the matuyama brunhes geomagnetic reversal which occurred about 780 000 years ago if correct this provides a crucial tie point between ice cores marine cores and a radiometric timescale