assessment of the impact of climate and anthropogenic factors on holocene mediterranean vegetation in europe on the basis of palaeohydrological records abstract correlations between lake level and river activity records from the western mediterranean and palaeohydrological records from northern africa and central europe suggest a distinction in the western mediterranean region between an early holocene period characterised by cooler and moister conditions than at present favourable to temperate deciduous trees and after 5000 yr bp a later holocene period with a warmer and drier climate the second phase was favourable to the extension of evergreen sclerophyllous trees possibly reinforced by human activities these two successive holocene periods reflect orbitally induced changes in summer insolation furthermore superimposed on this general climatic trend century scale climatic oscillations punctuated the whole holocene period decreases in river activity in the western mediterranean region occurred at ca 11 500 10 500 9000 7000 4000 3000 2000 and 800 cal yr bp these decreases coincided with lake level lowering in jura eastern france and glacier retreat in the northern alps and could be associated with a temporary expansion of sclerophyllous trees this general pattern could have resulted from an alternatingly southward northward displacement of the atlantic westerly jet

les affleurements de series sedimentaires pre pliocenes dans le bassin mediterraneen nord occidental abstract the dsdp site 372 leg 42 proved the outcropping of miocene layers off menorca island but a reexamination of several multichannel seismic profiles shows that these outcrops are common in many continental rises of the northwestern mediterranean basin three phenomena act together to explain these features first we have many evidences of deep contour currents which sweep the foot of the continental slope and removed the plio pleistocene deposits second extensive erosion occurring during the messinian event caused outcropping of the miocene beds third the continental rise with a thinned continental crust has a lower subsidence rate than the oceanic crust and the miocene beds are flexured seaward

a 300 kyr high resolution aridity record of the north african continent new oxygen isotope data and a high resolution carbonate record of a core from the northwest african margin are presented in combination with geochemical zr rb ratio al ba organic carbon and biogenic opal fluxes and sedimentological median grain size parameters to show variations in african continental aridity wind strength and upwelling productivity the carbonate record is diluted by the supply of aeolian dust from the arid saharan region of north africa and is seen to vary with a characteristic sawtooth pattern indicating rapid increases in dust flux followed by gradual declines spectral analysis of the carbonate profile and comparison with specmap stacked oxygen isotope and etp solar radiation profiles shows that the precessional 23 kyr insolation induced african climate system is decoupled from global ice volume climate changes operating on a 100 kyr frequency detailed studies of glacial terminations i ii and iii confirm the presence of rapid short timescale climatic variations in aridity

holocene climatic changes in the western mediterranean from south east france to south east spain abstract holocene climatic changes along coastal regions from south east france to south east spain were studied using pollen ratios comparing modern pollen rain vegetation and climate along selected transects from the atlantic ocean to the mediterranean we obtained threshold values of two different ratios corresponding to the different climatic conditions along the transects these pollen ratios and threshold values were employed to characterize the holocene climatic changes from nine mediterranean coastal sites the results were compared with data from marine and continental pollen sequences distributed in the western mediterranean basin and with additional regional data independent of human activity lake level fluctuations alpine glacier advance and retreat chronology 14 c anomaly and cooling phases in eastern france and central europe the role of anthropogenic activities and climate on the changes in vegetation is discussed six major changes in vegetation cover were identified they correspond to aridification phases that occurred around 9500 9000 yr bp 10 900 9700 cal bp 7500 7000 yr bp 8400 7600 cal bp 4500 4000 yr bp 5300 4200 cal bp 3700 3300 yr bp 4300 3400 cal bp 2600 1900 yr bp 2850 1730 cal bp and 1300 1000 yr bp 1300 750 cal bp these arid episodes were regional responses to more global climatic changes and determined the changes in the vegetation cover humans undoubtedly enhanced the vegetation changes but none the less had to adapt to these new climatic conditions

dansgaard oeschger and heinrich event imprints in alboran sea paleotemperatures past sea surface temperature sst evolution in the alboran sea western mediterranean during the last 50 000 years has been inferred from the study of c37 alkenones in international marine global change studies md952043 core this record has a time resolution of 200 years allowing the study of millennial scale and even shorter climatic changes the observed sst curve displays characteristic sequences of extremely rapid warming and cooling events along the glacial period comparison of this alboran record with 18o from greenland ice greenland ice sheet project 2 core shows a strong parallelism between these sst oscillations and the dansgaard oeschger events five prominent cooling episodes standing out in the sst profile are accompanied by an anomalous high abundance of neogloboquadrina pachyderma sinistral which is confined to the duration of these cold intervals these features and the isotopic record reflect drastic changes in the surface hydrography of the alboran sea in association with heinrich events hl 5

origin of the northern atlantic s heinrich events as first noted by heinrich 1988 glacial age sediments in the eastern part of the northern atlantic contain layers with unusually high ratios of ice rafted lithic fragments to foraminifera shells he estimated that these layers are spaced at intervals of roughly 10 000 years in this paper we present detailed information documenting the existence of the upper five of these layers in odp core 609 from 50 n and 24 w their ages are respectively 15 000 radiocarbon years 20 000 radiocarbon years 27 000 radiocarbon years about 40 000 years and about 50 000 years we also note that the high lithic fragment to foram ratio is the result of a near absence of shells in these layers although we are not of one mind regarding the origin of these layers we lean toward an explanation that the heinrich layers are debris released during the melting of massive influxes of icebergs into the northern atlantic these sudden inputs may be the result of surges along the eastern margin of the laurentide ice sheet

hydrometeorological controls and erosive response of an extreme alpine debris flow on 29 august 2003 an intense convective storm system affected the fella river basin in the eastern italian alps producing rainfall peaks of approximately 390 mm in 12 h the storm triggered an unusually large debris flow in the ungauged rio cucco basin 0 65 km2 with a volume of approximately 78 000 m3 the analysis of the time evolution of the rainstorm over the basin has been based on rainfall estimates from radar observations and data recorded by a raingauge network detailed geomorphological field surveys carried out both before and after the flood of august 2003 and the application of a distributed hydrological model have enabled assessment of flood response estimation of erosion volumes and sediment supply to the channel network the accounts of two eyewitnesses have provided useful elements for reconstructing the time evolution and the flow processes involved in the event liquid peak discharge estimates cluster around 20 m3 s 1 km 2 placing this event on the flood envelope curve for the eastern italian alps the hydrological analysis has shown that the major controls of the flood response were the exceptional cumulated rainfall amount required to exceed the large initial losses and the large rainfall intensities at hourly temporal scales required to generate high flood response at the considered basin scale observations on the deposits accumulated on the alluvial fan indicate that although the dominant flow process was a debris flow sheetflood also contributed to fan aggradation and fluvial reworking had an important role in winnowing debris flow lobes and redistributing sediment on the fan surface this points out to the large discharge values during the recession phase of the flood implying an important role for subsurface flow on runoff generation of this extreme flash flood event copyright 2009 john wiley sons ltd

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

origin and consequences of cyclic ice rafting in the northeast atlantic ocean during the past 130 000 years deep sea sediment cores recovered from the northeast atlantic ocean were examined in order to elucidate the influence of the earth s orbital parameters on major ice rafting analyses of coarse grained ice rafted debris and planktonic foraminifers revealed a strong reaction to the precession signal since 130 000 yr b p dropstone layers have been deposited each half period of a precessional cycle 11 000 1000 yr ice rafting occurs during times of winter minimum summer maximum insolation and summer minimum winter maximum insolation in the first case high summer insolation forces meltwater discharge from the ice sheets into the polar seas which subsequently enhances formation of sea ice during the winter in the second case growth of continental ice enhances iceberg production which also leads to a salinity reduction of surface seawater both situations result in a southward penetration of polar water thus the marine record of dropstones documents ice rafting not only during weichselian stades but also during cold events within interstades the regularity of ice rafting yields a useful framework to calibrate and elucidate climatic changes not only in the region of the north atlantic ocean but also in remote areas such as the pacific ocean and the antarctic

factors controlling late cenozoic continental margin growth from the ebro delta to the western mediterranean deep sea abstract the ebro continental margin sedimentation system originated with a messinian fluvial system this system eroded both a major subaerial canyon cutting the margin southeastward from the present ebro delta and an axial valley that drained northeastward down valencia trough post messinian submergence of this topography and the pliocene regime of high sea levels resulted in a marine hemipelagic drape over the margin late pliocene to pleistocene glacial climatic cycles drainagebasin deforestation and sea level lowstands combined to increase sediment supply cause the margin to prograde and create a regime of lowstand sediment gravity flows in the deeper margin the depositional patterns of regressive transgressive and highstand sea level regimes suggest that location of the sediment source near the present ebro delta throughout the late cenozoic southward current advection of sediment and greater subsidence in the southern margin combined to cause generally asymmetric progradation of the margin to the southeast thicker less stable deposits filling the messinian subaerial canyon underwent multiple retrograde failures eroded wide gullied canyons and formed unchanneled base of slope sediment aprons in the central margin area other margin areas to the north and south developed a series of channel levee complexes on the basin floor the formation of valencia valley over the messinian subaerial valley and earlier faults led to draining of about 20 of the ebro pleistocene sediment from channel levee complexes through the valley to prograde valencia fan as much as 500 km northeast of the margin thus the ebro margin has two growth directions mainly southeastward during higher sea levels and eastward to northeastward during lower sea levels the northeastward draining of turbidity currents has produced unusually thin and widely dispersed turbidite systems compared to those on ponded basin floors during the past few centuries man s impact has exceeded natural controls on ebro margin growth deforestation of the drainage basin more than doubled the normal holocene sediment supply and construction of dams then reduced the supply by 95 this reduction of the past 50 years has caused erosion of the delta and contamination of bottom sediment because normal holocene sediment discharge is not available to prograde the delta or help dilute pollutants

evolution of channel morphology and hydrologic response in an urbanizing drainage basin the dead run catchment in baltimore county maryland has undergone intense urbanization since the late 1950s reconstruction of the channel planform from topographic maps dating back to the 1890s and aerial photographs dating back to the 1930s indicates that the channel has remained stable in planform since at least the 1930s the relative stability of dead run contrasts with the alterations in channel morphology reported for other urbanizing streams in the piedmont physiographic province of the eastern united states trend analyses of discharge records in dead run show that urban development and stormwater control measures have had significant impacts on the hydrologic response of the catchment the flood hydraulics of the dead run catchment are examined for the event that occurred on 22 june 1972 in association with hurricane agnes a two dimensional hydraulic model telemac 2d was used with a finite element mesh constructed from a combination of high resolution lidar topographic data and detailed field survey data to analyse the distribution of boundary shear stress and unit stream power along the channel and floodplain during flooding from hurricane agnes the spatial and temporal distributions of these parameters relative to channel gradient and channel valley bottom geometry provide valuable insights on the stability of the dean run channel the stability of dead run s channel planform in spite of extreme flooding and decades of urban development is most likely linked to geological controls of channel and floodplain morphology copyright 2006 john wiley sons ltd

extreme rainfall and flooding from orographic thunderstorms in the central appalachians 1 the central appalachian region has experienced some of the largest rainfall accumulations in the world at time intervals less than 6 h including the 18 july 1942 smethport pennsylvania storm that produced 780 mm in less than 5 h the envelope curve of central appalachian flood peaks at small drainage areas less than 1000 km2 is dominated by orographic thunderstorm systems like the smethport storm orographic thunderstorm systems that have produced catastrophic flooding in the central appalachians are examined through observational and numerical model analyses using the weather research and forecasting wrf model analyses suggest that the frequency of catastrophic flooding varies over the central appalachian region and that small scale variation may be linked to the role of complex terrain in altering thunderstorm dynamics catastrophic flooding along the western margin of the central appalachians is dominated by four storms that occurred on 18 19 july 1889 1942 1977 and 1996 which were associated with warm season extratropical systems and were characterized by rapidly moving storm elements in complex terrain along the eastern margin and interior of the central appalachians catastrophic flooding is linked to four terrain locked orographic convective systems that occurred 17 18 june 1949 18 19 august 1969 27 june 1995 and 11 august 2003 wrf model simulations of the little river storm june 1949 rapidan storm june 1995 smethport storm 18 july 1942 and redbank storm 18 19 july 1996 are used to characterize ingredients of catastrophic rainstorms in the central appalachians

self repair of compacted vertisols from central queensland australia vertisols have the inherent ability to self repair because of high clay contents and clay type that govern volume change a study was undertaken to correlate soil inherent properties with two indicators of structure improvement based on tensile strength and clod porosity of compacted soil cores before and after wet dry cycles in order to minimize inter soil differences vertisols under similar cropping regimes and from the same climatic region in queensland australia were selected a soil repair index rt 1 based on compressive strength of soil cores was related to soil inherent properties and shrinkage indices colestd and lsmod using multiple regression results showed that compressive strength of soil cores after a single wet dry cycle after compaction was sufficient to rank vertisols in terms of their capacity to improve structure after compaction clay content and clay activity cec clay on their own were poor indicators of soil repair fine sand was shown to be an important component in the repair process lsmod and colestd predicted rt 1 equally well and indicated that vertisols with colestd values 0 15 and lsmod 12 would be expected to have sharper reductions in tensile strength compared to those with lower values after just one wet dry cycle clod porosity was poorly related to soil inherent properties 2008 elsevier b v

upper limits of flash flood stream power in europe abstract flash floods are characterized by strong spatial gradients of rainfall inputs that hit different parts of a river basin with different intensity stream power values associated with flash floods therefore show spatial variations that depend on geological controls on channel geometry and sediment characteristics as well as on the variations of flood intensity this stresses the need for a field approach that takes into account the variability of the controlling factors post flood assessment of peak discharge after major floods makes it possible to analyse stream power in fluvial systems affected by flash floods this study analyses the stream power of seven intense return period of rainfall 100 years at least in some sectors of the river basin flash floods that occurred in mountainous basins of central and southern europe from 2007 to 2014 in most of the analysed cross sections high values of unit stream power were observed this is consistent with the high severity of the studied floods the highest values of cross sectional stream power and unit stream power usually occur in mediterranean regions this is mainly ascribed to the larger peak discharges that characterize flash floods in these regions the variability of unit stream power with catchment area is clearly nonlinear and has been represented by log quadratic relations the values of catchment area at which maximum values of unit stream power occur show relevant differences among the studied floods and are linked to the spatial scale of the events values of stream power are generally consistent with observed geomorphic changes in the studied cross sections bedrock channels show the highest values of unit stream power but no visible erosion whereas major erosion has been observed in alluvial channels exceptions to this general pattern which mostly occur in semi alluvial cross sections urge the recognition of local or event specific conditions that increase the resistance of channel bed and banks to erosion or like short flow duration reduce the geomorphic effectiveness of the flood

hillslope and channel contributions to the hydrologic response 1 this paper develops a new framework to analyze the relevance of hillslope with respect to channel processes in the generation of the hydrologic response at different scales the dependence between basin response and geomorphic features of channels and hillslopes is analyzed through the mean and variance of travel times under simple but realistic dynamical hypotheses and within the framework of the rescaled width function the distribution of travel times is also studied in association with variations of the fraction of saturated areas with small values of the saturated fraction the channel network controls most of the mean and variance of travel time distribution vice versa when the basin is saturated the properties of this distribution may be significantly affected by hillslope processes these properties depend also on the basin size with the role of hillslope processes becoming more important in the smaller basins furthermore the average residence time is related to contributing area and drainage density through a simple expression which is shown to be consistent with previous empirical laws

response and recovery of a subalpine stream following a catastrophic flood the july 15 1982 lawn lake flood in rocky mountain national park colorado was caused by the failure of a 79 yr old earthen dam peak discharges of the flood far exceeded naturally occurring flows and it caused severe channel disturbance along most of roaring river and some parts of fall river this study documents the geomorphic response of a 5 km reach of fall river in the 5 yr following the flood in 1983 the first year after the lawn lake flood snowmelt flows were well above average these high flows together with very high sediment yields from roaring river resulted in significant geomorphic changes on reaches of fall river downstream during the 1983 snowmelt runoff 15 5 x 106 kg of bed load sediment was eroded from the upper part of the study area these loads were at least 1 000 times higher than before the lawn lake flood most of this sediment was then deposited in a highly sinuous reach of fall river in the lower part of the study area this reach had not been much affected by the lawn lake flood but sedimentation during the period of high flow in 1983 completely filled in the channel resulting in the formation of a continuous 2 3 km long depositional zone in 1984 sediment yield from roaring river declined dramatically and this trend continued for the next 3 yr by 1987 the bed load sediment yield in the upper reaches of fall river was only about 0 4 x 106 kg yr the decline in sediment loads resulted in progressive erosion and recovery of the original channel of fall river in the depositional zone reach recovery in the upstream part of the depositional zone was complete by 1985 recovery in the downstream part of the depositional zone took longer because of the continued supply of sediment and because the sediment was mobile less of the time as of 1987 about 80 of the material initially stored in the sedimentation zone had been eroded bed load sediment yields at a sampling site 1 km downstream of the terminus of the depositional zone ranged from 5 x 106 to 11 x 106 kg yr but showed no significant decline over the 5 yr study period the average rate of bed load transport through this reach was at least 100 times greater than before the lawn lake flood but few discernible channel changes resulted from the higher loads

holocene climate variability in europe evidence from δ18o textural and extension rate variations in three speleothems time series o isotope profiles for three u th dated stalagmites have revealed that for much of the holocene a site on the atlantic seaboard sw ireland exhibits first order 18o trends that are almost exactly out of phase with coupled 18o curves from two southern european sites se france and nw italy in the irish stalagmite cc3 from crag cave sw ireland low 18o at 10 000 cal yr bp reflects cool conditions by the early to mid holocene 9000 6000 cal yr bp 18o had increased reflecting the onset of warmer conditions on the atlantic seaboard this shift to higher 18o was accompanied by a marked increase in the stalagmite extension rate reinforcing our interpretation that this was a period of relative warmth except for an episode of increased extension rate about 5500 yr ago 18o in the crag stalagmite exhibits a gradual decrease accompanied by declining extension rates between 7800 and 3500 cal yr bp interpreted as a cooling trend there is evidence for increases in both 18o and stalagmite extension rate in the period from 3500 cal yr bp to the present day suggesting a return to warmer conditions on the atlantic seaboard in the stalagmite from nw italy er76 grotta di ernesto trentino province the early holocene c 9200 7800 cal yr bp is characterised by high 18o probably indicative of warm and or dry conditions exceptionally low 18o from 7800 to 6900 cal yr bp at this site reflects a well defined wet phase cerin wet phase in the last three millennia this stalagmite exhibits a shift to lower 18o interpreted as some combination of cooler and or wetter conditions unlike the irish stalagmite the italian sample does not show a correlation between 18o and extension rate instead its extension rate correlates roughly with 13c presumably reflecting a climate driven vegetation change in the early holocene 18o in the french stalagmite cl26 grotte de clamouse herault province se france was low relative to its holocene average for much of the period since c 3500 cal yr bp this stalagmite exhibits higher 18o than in the early holocene suggesting warmer conditions like the irish stalagmite the french sample exhibits a well defined correlation between 18o and extension rate had drip water availability been the dominant control on 18o at this semi arid site then higher 18o would have been accompanied by lower not higher extension rates this suggests strongly that temperature rather than rainfall amount was the dominant control at this site while conclusions regarding the patterns of climate variability on a continent scale must remain tentative because of the limited number of stalagmites studied we argue that early holocene warm conditions on the atlantic seaboard irish site coincided with relatively cool conditions at the clamouse site by c 3500 yr ago the pattern appears to have been reversed

millennial scale variability in the productivity signal from the alboran sea record western mediterranean sea primary productivity of the alboran sea western mediterranean is reconstructed for the time interval 48 000 to 28 000 years bp using the following geochemical proxies calcium carbonate barium excess baexcess total organic carbon toc and alkenone concentration the records show a consistent pattern that indicates enhanced productivity during dansgaard oeschger d o warm periods at the same time deep water conditions were favorable for organic matter preservation in the sediments as indicated by the variation in redox sensitive elements such as mn cr or v and by the 13c record of benthic foraminifers the alboran sea productivity variation during d o cycles is explained by the succession of two climatic scenarios that led to latitudinal shifts of the westerly wind system this mechanism would also account for the variability in the deep water ventilation of the western mediterranean sea

humid tropical expansive soils of trinidad their geotechnical properties and areal distribution abstract expansive soils occur in abundance in the central and southern regions of trinidad and contribute to extensive landsliding and building and pavement damage since there is little documentation available in this country on these soils this study is undertaken to develop the necessary data to cope up with the deleterious nature of these soils disturbed and undisturbed soil samples are obtained from a large number of sites covering both regions and tested for grain size classification suction and potential swell measurements based on the results of these tests a modified plasticity chart and a multi parameter criteria are presented to identify the expansive soils according to the degree of their expansivity the results have shown that these soils exist in an overconsolidated state and theirin situ water contents are high and are generally at plastic limit as a result their potential swelling capability is apparently somewhat restrained further a hazard map is presented showing areas of potential danger from expansive soils to light engineering structures

chemical cycles in pliocene sapropel bearing and sapropel barren eastern mediterranean sediments abstract high resolution 3 4 cm investigations of major and minor elements were carried out on sediment cores from odp leg 160 sites 964 ionian basin 969 mediterranean ridge 967 and 966 northern slope and top of eratosthenes seamount south of cyprus at site 967 element al ratios display pronounced cyclic records that are related to astronomically forced climatic variations sediments from the top of eratosthenes seamount site 966 show a similar pattern to those from site 967 but they are more disturbed by bioturbation and also strongly influenced by long term variations in sediment dispersal sediments from site 969 display similar trends to those from site 964 i e they are characterized by higher mg al slightly higher k al and lower ti al ratios during sapropel formation higher ti al ratios at site 969 compared with sediments from site 964 may be explained by a westward transport of material from a source in the east where ti al ratios are highest sites 966 and 967 elevated mg al ratios at site 969 during sapropel intervals are due to river derived material transported through the kithira strait between peloponnesus and crete from the northwestern aegean sea which originates from ultramafic rocks a change in intermediate water currents current reversal during sapropel formation may explain the enhanced supply of mg rich and the relatively diminished supply of ti rich material we propose that during deposition of the reddish intervals at site 969 a change in circulation did not occur because a drastic decrease in ti al ratios is not evident in these sediments ba peaks indicative of former sapropels are not present ba enrichments in the same sapropel barren intervals at site 967 northern slope of eratosthenes seamount suggest that during such intervals the burn down process was more effective than during the sapropel bearing intervals mn contents in all investigated pliocene sediments correlate with the carbonate contents higher mn contents of the sapropel barren sediments suggest that during time intervals of sapropel formation either mn accumulation at the margins of the permanently oxic upper water column or mn export into the western mediterranean might have occured the latter could only be explained by sub or anoxic conditions in large parts of the water column

vegetation history and palaeoclimate of the last glacial period at lago grande di monticchio southern italy a high resolution palynological study of a 51 m core from lago grande di monticchio southern italy has provided a palaeonvironmental record for the last glacill a annual lamination based chronology supported by radiometric and tephrochronological dates provides an absolute timescale for this record that spans 76 300 years correlations are established between the pollen stratigraphy the grip ice core 18o record and foraminiferal assemblages from atlantic core v23 81 both dansgaard oeschger and heinrich events are reflected by changes in the pollen stratigraphy revised dates are estimated for heinrich events h1 h6 a quantitative palaeoclimate reconstruction based upon the pollen data provides evidence of the climate changes in southern italy associated with these and other fluctuations during the last glacial

rapid environmental changes in southern europe during the last glacial period oxygen isotope records from greenland ice cores1 2 indicate numerous rapid climate fluctuations during the last glacial period north atlantic marine sediment cores show comparable variability in sea surface temperature and the deposition of ice rafted debris3 4 5 in contrast very few continental records of this time period provide the temporal resolution and environmental sensitivity necessary to reveal the extent and effects of these environmental fluctuations on the continents here we present high resolution geochemical physical and pollen data from lake sediments in italy and from a mediterranean sediment core linked by a common tephrochronology our lacustrine sequence extends to the past 102 000 years many of its features correlate well with the greenland ice core records demonstrating that the closely coupled ocean atmosphere system of the northern hemisphere during the last glacial4 extended its influence at least as far as the central mediterranean region numerous vegetation changes were rapid frequently occurring in less than 200 years showing that the terrestrial biosphere participated fully in last glacial climate variability earlier than 65 000 years ago our record shows more climate fluctuations than are apparent in the greenland ice cores together the multi proxy data from the continental and marine records reveal differences in the seasonal character of climate during successive interstadials and provide a step towards determining the underlying mechanisms of the centennial millennial scale variability

abrupt cold spells in the northwest mediterranean hitherto unknown abundance peaks of left coiling l c neogloboquadrina pachyderma from a gulf of lions piston core indicate that abrupt cold spells associated with atlantic heinrich events affected the mediterranean n pachyderma l c is typical of sub polar waters in the open ocean the southern edge of its glacial north atlantic bioprovince reached south portugal only trace abundances of n pachyderma l c are known from quaternary mediterranean sediments suggesting that no significant invasions occured via the strait of gibraltar the gulf of lions abundance peaks therefore seem to reflect area specific thriving of a normally rare but indigenous taxon in the western mediterranean through local favorable habitat development the general planktonic foraminiferal record suggests that the basic hydrographic regime in the gulf of lions with wintertime deep convective overturn was relatively stable over the past 60 kyr under these conditions high abundances of n pachyderma l c would essentially imply temperature reductions of the order of 5 8 relative to the present

catastrophic flooding from an orographic thunderstorm in the central appalachians 1 an orographic thunderstorm system in pendleton county west virginia produced 125 150 mm of rainfall in less than 1 hour on 9 august 2003 rainfall and fluvial impacts were concentrated in the ungauged 2 1 km2 saul s run watershed despite the short duration of the event the flood produced significant fluvial impacts and abrupt changes in the extent of incision and channel widening hydrometeorological analyses of the storm are based on wsr 88d radar reflectivity observations and rain gauge observations the small multicell thunderstorms that produced the saul s run flood were not markedly different from other storms in the central appalachian region on 9 august 2003 detailed surveys of high watermarks and channel floodplain geometry are used for hydraulic analyses of the saul s run flood including estimation of peak discharge at four locations peak discharge estimates at the 1 km2 scale cluster around 18 m3 s 1 placing this event on the flood envelope curve for the mid atlantic region observed rainfall estimated peak discharge and observer notes on timing of peak discharge are used along with a distributed hydrologic model to reconstruct hydrographs at multiple locations hydrologic modeling indicates that land use effects may have significantly influenced extreme flood response in saul s run the wide range of fluvial impacts is consistent with patterns of boundary shear stress and unit stream power derived from a simulation of the saul s run flood using a 2 d depth averaged hydraulic model

effect of sediment transport boundary conditions on the numerical modeling of bed morphodynamics abstractexperimental sediment transport and river morphologic studies in laboratory flumes can use two sediment supply methods an imposed feed at the upstream end or a recirculation of sediment f

catastrophic arid episodes in the eastern mediterranean linked with the north atlantic heinrich events the response of continental climate to the well documented climate oscillations during the last glacial period has been a subject of intense interest yet much less is known about the influence on regional continental climates than in the marine or polar realms of earth the detailed lake level history of the closed lake lisan paleo dead sea in the middle east has been reconstructed from shoreline indications and high resolution u th and 1 4 c chronologies thus providing data on the response of the lake s catchment area to the climate changes during the corresponding period we present a correlation between the newly developed lake lisan level curve for the past 55 k y and the north atlantic heinrich events the correlation indicates a closely connected climate response between these north atlantic events and the hydrologic conditions that prevailed in the eastern mediterranean our findings show that although the generally cooler conditions that prevailed during the last glaciation favored high levels of the lake catastrophic events in the north atlantic which are associated with maximum cooling have been responsible for droughts in the eastern mediterranean we infer that cold water input to the mediterranean originating in the collapse of the north atlantic deep water circulation caused the reduction of evaporation and less precipitation in the eastern mediterranean

geomorphic impacts of flash flooding in a forested headwater basin abstract geomorphic impacts of a july 2001 flood in the hungry mother basin near marion virginia were examined to shed light on the relationships between channel characteristics and the frequency of channel modifying discharges creeks in the study area have been observed for many years with no significant channel changes since at least 1985 the 2001 flood had a recurrence interval of 200 years and caused the only channel change bank erosion and transport of coarse channel material observed in recent decades the paucity of fines in channels before or after the flood and the absence of sub sand sized material in the flood deposits indicates that normal frequent well below bankfull flows are sufficient to transport the apparently limited supply of fines the large particles transported during the 2001 flood after years of inactivity indicate that relatively rare floods are necessary to mobilize this material this suggests the notion of a bimodal dominant discharge on the one hand frequent flows considerably below bankfull levels are sufficient to maintain the channel and prevent significant accumulation of fine sediments and organic matter on the other hand rare floods are necessary to transport the coarser bed material and erode channel banks in the hungry mother area bed material has no relationship to normal flows or to flows with recurrence intervals on the order of 1 3 years bankfull discharge is apparently not related to either the maintenance or channel changing dominant discharges these results suggest that the use of channel dimensions and or bed material as surrogate indicators of hydrologic regimes can be quite complicated and that in some streams bankfull flow has no particular significance in terms of sediment transport and channel modifications

a hydraulic box model study of the mediterranean response to postglacial sea level rise 1 this paper quantifies the role of changing sea level in affecting mediterranean stratification using a new model of the strait basin system which allows for explicit time dependence during the last deglaciation fairbank s meltwater peak 1b leads to rapidly rising global sea levels and a freshening of the oceans and hence increasing influx of ever freshening atlantic water into the mediterranean basin owing to long residence times the salinity of the deep and intermediate water reservoirs would have decreased more slowly so that the basin was more stably stratified for a period with possible implications for sapropel formation our model is used to estimate the size of this reservoir effect in comparison to the freshwater influx from the opening of the black sea at the bosphorus it is found that this mechanism affects the stratification to a similar degree as the black sea opening other climatic mechanisms have also affected the freshwater budget of the mediterranean at this time but their sizes are more difficult to quantify

climate variability in the spanish pyrenees during the last 30 000 yr revealed by the el portalet sequence abstract palynological sedimentological and stable isotopic analyses of carbonates and organic matter performed on the el portalet sequence 1802 m a s l 42 48 00 n 0 23 52 w reflect the paleoclimatic evolution and vegetation history in the central western spanish pyrenees over the last 30 000 yr and provide a high resolution record for the late glacial period our results confirm previous observations that deglaciation occurred earlier in the pyrenees than in northern european and alpine sites and point to a glacial readvance from 22 500 to 18 000 cal yr bp coinciding with the global last glacial maximum the patterns shown by the new high resolution pollen data from this continental sequence chronologically constrained by 13 ams 14c dates seem to correlate with the rapid climate changes recorded in greenland ice cores during the last glacial interglacial transition abrupt events observed in northern latitudes heinrich events 3 to 1 oldest and older dryas stades intra allerod cold period and 8200 cal yr bp event were also identified for the first time in a lacustrine sequence from the central western pyrenees as cold and arid periods the coherent response of the vegetation and the lake system to abrupt climate changes implies an efficient translation of climate variability from the north atlantic to mid latitudes

observation of an abrupt disruption of the long term warming trend at the balearic sea western mediterranean sea in summer 2005 1 the properties of the western mediterranean deep water in a wide area located at the western boundary of the mediterranean sea including the balearic sea have revealed intense changes when observed in summer 2005 between february and june 2005 a temperature drop of 0 14 c reverted dramatically the progressive warming trend of 0 011 c yr 1 that had been observed since 1996 in the waters below 600 dbar north of the balearic channels a similar temperature drop has been observed east of the minorca island below the levantine intermediate water and down to 1500 dbar in the deepest levels a complex thermohaline structure which implies different waters masses as sources was tracked more than 400 km along the western boundary of the mediterranean sea from barcelona to the algerian basin it is suggested that the changes may be linked to the severe 2004 2005 winter occurred at the northwestern mediterranean sea

ocean surface water response to short term climate changes revealed by coccolithophores from the gulf of cadiz ne atlantic and alboran sea w mediterranean the response of coccolithophore assemblages to short term millennial and centennial climatic changes over the last 50 kyr is studied in core m39029 7 from the gulf of cadiz atlantic ocean and core md95 2043 from the alboran sea western mediterranean sea the nannoplankton data are compared with oxygen isotopes u37k sst and other biogeochemical and sedimentological proxies to obtain a new perspective of the paleoceanography and paleoecology of the area during these short term climatic changes coccolithophores indicate that heinrich events he were characterised by the presence of cold low salinity and turbid water masses on both sides of the strait of gibraltar high abundances of the lower photic zone lpz species florisphaera profunda in the gulf of cadiz synchronous with he are interpreted as being an evidence of upper water column stratification on the atlantic side these episodes coincided with input of terrigenous material especially during h2 surface waters during dansgaard oeschger do stadials were also cold and turbid while most of do interstadials were characterised by warm water flora the increase in small placoliths small gephyrocapsa and emiliania huxleyi 4 m which is considered here as a cold water indicator the sharp decrease in large specimens of e huxleyi related to the warming trend in the last deglaciation can be used as a biostratigraphic reference level that marks at least approximately the deglaciation and the beginning of the holocene peaks of f profunda are observed during termination 1 t1 in the alboran sea they are isochronous with the organic rich layer 1 recognised in the western mediterranean in this interval the water column of the region was stratified as a consequence of the global increase in the sea level following the deglaciation quantitative analyses of the coccolithophore assemblage allow us to interpret that coccolithophore production has been higher in the alboran sea than in the gulf of cadiz during the holocene

valencia fan northwestern mediterranean distal deposition fan variant abstract the valencia fan one of the larger deep sea depositional systems in the western mediterranean sea developed in the large depression between the valencia trough and the balearic basin plain six main lithoseismic units are identified and sedimentary processes inferred from 6000 km of sparker profiles this fan is largely formed by channelized and irregularly stratified units the sedimentary processes controlling the development of these units include channelized sediment flows that evolve downfan into sheet flows three fan depositional provinces are differentiated on the basis of the relative proportions of lithoseismic units and the inferred sedimentary processes regularly stratified seismic units predominate in the non fan environments these units are dominated by fine grained deposits resulting from hemipelagic settling and overbank flows from turbid currents distal flows from the continental slopes of the iberian peninsula and balearic islands also contribute materials for the development of these environments the wavy units flanking the upper fan may have resulted from migrating sediment waves or limited mass displacement of the stratified units while the transparent units are attributed to extensive mass flow the valencia valley is largely an erosional feature across which sediments from several source areas bypassed to the distal deep sea depositional system of the valencia fan deposition begins at the mouth of the valley beyond which there is a break in slope the fan migrated upslope and filled the valencia valley from the distal sectors this evolution has been controlled by the interplay between sedimentary processes active in the fan growth and large scale geological factors related to the structural framework of the study area

palaeogeographic implications of the messinian surface in the valencia trough northwestern mediterranean sea abstract sparker 3000 j and 8000 j and multichannel seismic reflection profiles across the valencia trough show a messinian unconformity incised by numerous valleys the main feature of this surface is a large valley that generally underlies the present valencia valley and is deeply entrenched into the miocene deposits the size of this palaeo valley ranges from 0 5 km wide and 15 100 m deep at its western end to 1 6 2 8 km wide and 200 250 m deep downstream an important tributary system is observed with a main canyon 6 8 km wide and 150 200 m deep draining the ebro margin as well as many other smaller valleys draining the catalan and balearic margins downstream other tributaries underlie the present canyons of the catalan margin the location of the tributary system is controlled by the early miocene rift structures the relief of the messinian surface is affected by post miocene deformation that results from salt diapirism extensional faulting and related volcanism late neogene to quaternary volcanic edifices cut the messinian surface and coincide with large residual magnetic anomalies lower pliocene to quaternary salt diapirism in the abyssal plain north of menorca has created a series of structural highs between these highs are deep interdiapiric troughs or basins that have become sediment depocentres during the plio quaternary the complex network of erosional valleys from the valencia trough continental margin demonstrates that the valley system in the basin was not related to the refilling of the mediterranean but to the iberian and balearic margin palaeodrainage that developed during the messinian desiccation the presence of at least three erosional unconformities suggests that there were alternating periods of flooding and retreat of atlantic water during messinian time the messinian subaerial margin with erosional valleys contrasts sharply with the pliocene quaternary marine margin with progradational turbidite systems

isotopic chronology of the sahara and the sahel during the late pleistocene and the early and mid holocene 15 000 6000 bp

geological framework of the ebro continental margin and surrounding areas abstract the eastern and southeastern margins of iberia were affected during neogene time by a rifting tectonic process superimposed on the alpine structures the valencia trough situated off the northeastern coast of iberia has been defined as a rift system that began its activity in late oligocene early miocene time the opening of the valencia trough produced a series of tectonic grabens created by fractures which strike parallel to the coastline as a consequence of the rifting subsidence occurred and depositional sequences of miocene age were subsequently deposited over the triassic and mesozoic basement some of the mesozoic faults were reactivated and affected the tertiary deposits the depositional history was controlled mainly by extensional faulting during the late paleocene early miocene and by rapid subsidence during the late pliocene a second extensional period occurred in the iberian chain resulting in the present configuration of the continental margin in the study area the pliocene quaternary evolution of the margin was largely controlled by fluctuation of the ebro river sediment supply and sea level oscillations

prediction of swelling pressure of soil using artificial intelligence techniques the swelling pressure of soil depends upon various soil parameters such as mineralogy clay content atterberg s limits dry density moisture content initial degree of saturation etc along with structural and environmental factors it is very difficult to model and analyze swelling pressure effectively taking all the above aspects into consideration various statistical empirical methods have been attempted to predict the swelling pressure based on index properties of soil in this paper the computational intelligence techniques artificial neural network and support vector machine have been used to develop models based on the set of available experimental results to predict swelling pressure from the inputs natural moisture content dry density liquid limit plasticity index and clay fraction the generalization of the model to new set of data other than the training set of data is discussed which is required for successful application of a model a detailed study of the relative performance of the computational intelligence techniques has been carried out based on different statistical performance criteria

comparison of oxygen isotope records from the gisp2 and grip greenland ice cores recent results1 2 from the greenland ice core project grip summit ice core suggest that the climate in greenland has been remarkably stable during the holocene but was extremely unstable for the time period represented by the rest of the core spanning the last two glaciations and the intervening eemian inter glacial here we present the complete oxygen isotope record for the greenland ice sheet project 2 gisp2 core drilled 28 km west of the grip core we observe large rapid climate fluctuations throughout the last glacial period which closely match those reported for the grip core however in the bottom 10 of the cores spanning the eemian interglacial and the previous glacia tion there are significant differences between the two records it is possible that ice flow may have altered the chronological sequences of the stratigraphy for the bottom part of one or both of the cores considerable further work will be necessary to evaluate the likelihood of this and the extent to which it will still be possible to extract meaningful climate information from the lowest sections of the cores

critical flow constrains flow hydraulics in mobile bed streams a new hypothesis a new hypothesis predicts that in mobile bed river channels interactions between the channel hydraulics and bed configuration prevent the froude number fr from exceeding 1 for more than short distances or periods of time flow conditions in many steep competent streams appear to be close to critical froude numbers of steep slope 0 01 sand bed streams with considerable freedom to adjust boundaries oscillate between 0 7 and 1 3 over 20 to 30 s cycles with an average of 1 0 at the channel thalweg criticalflow in these streams is maintained by the interaction between the mobile bed and free water surface at highfr which results in a cyclical pattern of creation and destruction of bed forms field observations support that a similar mechanism offlow bed form interaction constrains fr 1 in active bed braided gravel rivers step pool streams laboratory rills lahar runout channels and even some bedrock channels empirical and analytical results show that as slope increases competentflows tend to asymptotically approach criticalflow an assumption of criticalflow would dramatically simplify paleohydraulicflow reconstructions and modeling offlow hydraulics in high gradient streams

the climate of europe 6000 years ago palaeoclimates across europe for 6000 y bp were estimated from pollen data using the modern pollen analogue technique constrained with lake level data the constraint consists of restricting the set of modern pollen samples considered as analogues of the fossil samples to those locations where the implied change in annual precipitation minus evapotranspiration p e is consistent with the regional change in moisture balance as indicated by lakes an artificial neural network was used for the spatial interpolation of lake level changes to the pollen sites and for mapping palaeoclimate anomalies the climate variables reconstructed were mean temperature of the coldest month tc growing degree days above 5 c gdd moisture availability expressed as the ratio of actual to equilibrium evapotranspiration and p e the constraint improved the spatial coherency of the reconstructed palaeoclimate anomalies especially for p e the reconstructions indicate clear spatial and seasonal patterns of holocene climate change which can provide a quantitative benchmark for the evaluation of palaeoclimate model simulations winter temperatures tc were 1 3 k greater than present in the far n and ne of europe but 2 4 k less than present in the mediterranean region summer warmth gdd was greater than present in nw europe by 400 800 k day at the highest elevations and in the alps but 400 k day less than present at lower elevations in s europe p e was 50 250 mm less than present in nw europe and the alps but was 10 15 greater than present in s europe and p e was 50 200 mm greater than present in s and e europe

synchroneity between marine and terrestrial responses to millennial scale climatic variability during the last glacial period in the mediterranean region land sea climatic proxies have been obtained from the last glacial section of images core md95 2043 western mediterranean sea vegetation and alkenone derived sst curves indicate rapid 150 years and synchronous terrestrial and marine climatic changes paralleling the dansgaard oeschger d o climatic variability over greenland this frequency of climate change can be related to shifts between the two modes of operation of the north atlantic oscillation nao transfer functions applied to the pollen data indicate that there was an amplification of the climatic signal during heinrich events hes in comparison with other d o stadials the development and persistence of both scandinavian and atlantic mobile polar highs over southwestern europe may explain the extreme cooling 10 c and dryness 400 mm during heinrich events 5 and 4 in the mediterranean region comparison of the results of core md95 2043 with similar climatic data from images core md95 2042 located off portugal indicates that thermal and precipitation gradients occurred between the mediterranean and the atlantic sides of iberia within hes hes 4 and 5 are associated with more humid conditions in the atlantic by 200 mm than in the mediterranean site as is the case at the present time this comparison also illustrates the different behaviour of these areas during the d o stadials in contrast with the mediterranean site the atlantic site shows similar precipitation and temperature drops for all the d o stadials including those related to the hes here we propose the operation of different mobile polar highs mph as the driving mechanism for this difference in behaviour between the atlantic and mediterranean sides of iberia hes are related to a stronger influence of the scandinavian mph forcing a severe aridification and cooling of the full iberian peninsula the atlantic mph may have been dominant during the other stadials which would preferentially affect southwestern iberia

holocene atmosphere ocean interactions records from greenland and the aegean sea we compare paleoclimate proxy records from central greenland and the aegean sea to offer new insights into the causes timing and mechanisms of holocene atmosphere ocean interactions a direct atmospheric link is revealed between aegean sea surface temperature sst and high latitude climate the major holocene events in our proxies of aegean sst and winter spring intensity of the siberian high gisp2 k record follow an 2300 year spacing recognised also in the 14c record and in worldwide holocene glacier advance phases suggesting a solar modulation of climate we argue that the primary atmospheric response involved decadal centennial fluctuations in the meridional pressure gradient driving aegean sst events via changes in the strength duration and or frequency of northerly polar continental air outbreaks over the basin the observed natural variability should be accounted for in predictions of future climate change and our timeframe for the aegean climate events in addition provides an independent chronostratigraphic argument to middle eastern archaeological studies

effectiveness of exceptional rainstorms on a small mediterranean basin abstract a comprehensive investigation of rainstorms and their consequent impacts on landscape evolution is geomorphologically important but only scant information may be available on exceptional events because parameters on synoptic conditions rainstorm landforms and hydrology for such events may be incomparable with previous knowledge we studied an exceptional storm on april 2 2006 in the ramot menashe region israel our investigation of rainfall landslides debris flows and channel suggests the effectiveness of such an event on the development of basin scale morphology the storm caused damage and casualties although it covered relatively narrow strips neither direct rainfall nor runoff measurements exist for the most severely affected area of ramot menashe but the geomorphologic evidence combined with high resolution meteorological radar data provides the basic understanding of the processes and hazardous conditions which prevailed at the time in the storm core based on estimation from meteorological radar data 263 mm of rain fell within 3 h with a maximum intensity of 220 mm h 1 for 10 min triggering both sporadic landslides at the soil bedrock contact on the upper slopes and widespread landslides at the fractured massive bedrock contact on the lower slopes the 1st order channels on the alternation of chalk and marl also underwent erosion and the produced sediment deposited on alluvial fans at the confluence with the main channel the specific peak discharges for catchment size of 0 3 10 km2 were 11 to 73 m3 s 1 km 2 higher than any recorded floods in the mediterranean climatic region of israel the effectiveness of the flood for geomorphic work represented by shear stress and stream power per unit boundary area reached 87 398 n m 2 and 212 2134 w m 2 respectively this kind of analysis can be applied to hazard prediction in other areas under similar geomorphological conditions

biometry of emiliania huxleyi and its biostratigraphic significance in the eastern north atlantic ocean and western mediterranean sea in the last 20 000 years abstract a detailed biometric study of coccoliths of emiliania huxleyi has been performed on 34 samples from three sediment cores of the north atlantic ocean and the western mediterranean sea su90 08 m39029 7 and md95 2043 all three cores contain the last glacial interglacial transition marine isotopic stages 1 2 enabling us to study in detail the morphology of this taxon during this period of change one hundred coccoliths of e huxleyi were randomly chosen in each sample distal shield length and width measurements were performed on each of the individuals selected the data show that e huxleyi specimens larger than 4 m are frequent in glacial samples and that these larger forms decreased sharply in abundance during the deglaciation and holocene smaller forms are more abundant in this latter group of samples the decrease in larger forms seems to be time transgressive since it is recorded between 12 and 11 kyr cal bp in southern locations alboran sea and gulf of cadiz and around 8 4 kyr cal bp in the central north atlantic scanning electron microscope analyses indicated that the two forms have the same degree of calcification and hence this parameter should not be used in taxonomic classifications we suggest that the larger coccoliths belong to a cold water variety of e huxleyi which can be distinguished from the small coccolith variety in light microscope analyses by its distal shield length the decrease in the abundance of this larger variety during the deglaciation period could be used as a biostratigraphic event in the north atlantic and mediterranean areas

palaeocurrent reconstruction sediment and thorium focussing on the iberian margin over the last 140 ka sedimentological data in particular sediment grain size from core md95 2040 2465 m water depth and a nearby core omii 9k 1833 m water depth presently under the influence of lower north atlantic deep water and deep intermediate water respectively have been used to reconstruct changes in the vigour of near bottom water flow on the iberian margin the pattern of the palaeocurrent index indicates faster flow during the warm periods and slower in cold this also holds in the younger dryas but there is an added effect of brief collapse of the circulation in termination 1b due to meltwater input the cold periods are generally characterised by elevated clay percentage terrigenous material 2 m diameter and overall sediment accumulation fluxes in comparison warm periods of higher flow have lower depositional flux and a tendency to silt terrigenous material 2 63 m dominance consistent with the higher flow speed and suppression of clay deposition this is in contrast with a recent 230thxs based study of two cores md95 2040 and 2039 j thomson et al earth planet sci lett 165 1999 255 270 which concluded that increased glacial sediment and th focussing was caused by stronger currents the crucial factor is that the controlling speed is that of the flow at the depositional site rather than that of the erosional or transporting flow to the site high glacial maximum fluxes of carbonate 6 g cm 2 ka 1 are largely composed of fine 63 m non coccolith material suggesting a significant detrital component it is proposed that the sediment and th arrive on the lower slope via different routes sediment down slope in bottom nepheloid layers and turbidity currents th scavenged from the water column by organic matter and are rapidly mixed on the bed removal of this material from a large area and its deposition in a small one adjacent to oporto seamount together with a small amount of direct down slope supply accounts for the properties of the deposits allowance for erroneous fluxes due to possible coring expansion stretching of the upper part of md95 2040 does not invalidate these conclusions

role of tree dams in the construction of pseudo terraces and variable geomorphic response to floods in little river valley virginia geomorphic response to a 1985 flood in little river valley northern virginia was different in magnitude and style from the largest historic flood in the same valley in 1949 the primary geomorphic activity during the 1985 flood was severe bank erosion and channel gravel deposition rather than the debris flow and avalanching of the 1949 event an unusual and widespread phenomenon of the recent flood was that large trees eroded and transported by the floodwater were aligned parallel to the river banks and at isolated sites were braced and stacked against trees still standing on the floodplain lateral barriers or dams created from these displaced trees allowed the channel to be locally aggraded above the level of the flood plain in these reaches little if any river gravel was deposited on the floodplain even though the adjacent channel floor was raised well above that surface the river has now shifted around the filled segments leaving flat isolated surfaces underlain by channel gravel standing above the level of the modern floodplain these features may be mistaken for terraces alter they become vegetated and the trees bracing the gravels decay interpreting these surfaces to be terrace remnants would lead to a faulty reconstruction of geomorphic history in the little river valley and other valleys where floodplain morphology is controlled by infrequent flood events

shrinkage and atterberg limits in relation to other properties of principal soil types in israel abstract soil samples collected from 32 sites across israel representing major types were analyzed for their pedological characteristics and mechanical properties correlative relationships between shrinkage measured by the coefficient of linear extensibility cole atterberg limits liquid and plastic and the physical and chemical properties were established and indicate possibilities of estimating mechanical properties from known pedological data strong correlations were noted between mechanical properties and the pedological characteristics reflecting clay mineralogy and texture e g cation exchange capacity specific surface area hygroscopic moisture and clay content these relationships are useful inasmuch as clay mineralogy is usually evident from soil classification sodicity and salinity common in dry soils of semi arid regions may introduce complicating factors such as raising or lowering atterberg limits respectively shrinkage is similarly affected being accentuated at high sodium low salt levels and reduced in highly saline sodic soils organic matter was correlated with liquid and plastic limits but no relationship with shrinkage was noted calcium carbonate also had little influence on atterberg limits the relationships presented may serve as first approximations mechanical properties of the soil groups illustrate the range of values encountered among regions with differing environmental conditions

role of debris flows in long term landscape denudation in the central appalachians of virginia four major storms that triggered debris flows in the virginia west virginia appalachians provide new insights into the role of high magnitude low frequency floods in longterm denudation and landscape evolution in mountainous terrain storm denudation in the blue ridge mountain drainage basins is approximately an order of magnitude greater compared to basins located in the mountains of the valley and ridge province this difference is probably the result of higher storm rainfall from the blue ridge storms radiocarbon dating of debris flow deposits in the blue ridge indicates a debris flow return interval of not more than 2 4 k y in mountainous river basins this finding combined with measurements of basin denudation suggests that approximately half of the long term denudation from mechanical load occurs episodically by debris flow processes although floods of moderate magnitude are largely responsible for mobilizing sediment in lowgradient streams our data suggest that high magnitude low frequency events are the most significant component in delivering coarse grained regolith from mountainous hollows and channels to the lowland floodplains

variability of the large scale general circulation of the mediterranean sea from observations and modelling a review abstract in this paper we present an overview of the most recent findings about the mediterranean sea present day circulation structure both historical observations and numerical model simulations are presented outlining the differences and agreement the model simulations are presented for both an eddy resolving and a coarse resolution numerical model and the results are intercompared the importance of the mesoscales in modifying the large scale flow field is elucidated the critical point is the discovery of the large amplitude interannual variability of the circulation and water mass structure associated with the anomalies of atmospheric forcing over the basin the seasonal variability can be strictly related to changes in heat and momentum fluxes while the interannual variability has a component which is related to the mesoscale field the latter is very intense in the algerian current region and levantine basin but different in structure in the two regions results are shown which confirm the importance of wind driving in establishing the kinetic energy of the flow field by comparing the current transport at the strait of corsica with observations in conclusion the essential characteristics of the present day circulation are associated with the atmospheric forcing and the basin topographic structure results from palaeoceanographic simulations for the last 20 000 years show that changing the atmospheric forcing can cause large changes in the circulation structure which may have affected sapropel formation

the greenland ice sheet project 2 depth age scale methods and results the greenland ice sheet project 2 gisp2 depth age scale is presented based on a multiparameter continuous count approach to a depth of 2800 m using a systematic combination of parameters that have never been used to this extent before the ice at 2800 m is dated at 110 000 years b p with an estimated error ranging from 1 to 10 in the top 2500 m of the core and averaging 20 between 2500 and 2800 m parameters used to date the core include visual stratigraphy oxygen isotopic ratios of the ice electrical conductivity measurements laser light scattering from dust volcanic signals and major ion chemistry gisp2 ages for major climatic events agree with independent ages based on varve chronologies calibrated radiocarbon dates and other techniques within the combined uncertainties good agreement also is obtained with greenland ice core project ice core dates and with the specmap marine timescale after correlation through the 18 o of o 2 although the core is deformed below 2800 m and the continuity of the record is unclear we attempted to date this section of the core on the basis of the laser light scattering of dust in the ice

late glacial to recent deep sea benthic foraminifera from the northeastern atlantic cadiz gulf and western mediterranean alboran sea paleooceanographic results abstract deep sea benthic foraminifera of the region of water exchange between the mediterranean and the atlantic ocean at the gibraltar strait show significant water mass relationships for the past 18 000 years cores used in this benthic foraminifera analysis were selected according to the context of the distribution of various deep bottom water masses on each side of the gibraltar strait 1 1 on the atlantic side of the strait two cores ks 8228 ks 8229 are located in the present day nadw and one kc 8221 in the upper part of the present mediterranean outflow water 2 2 on the mediterranean side of gibraltar two cores kc 8241 su 8107 are located in the deep water mass and one ks 8230 in the intermediate water mass in the two deep basins 1500 2800 m depth in the gulf of cadiz 1200 1300 m depth in the alboran sea the paleooceanographic changes appear to be in an opposite way for the past 18 000 years the alboran basin shows a paleooceanographic evolution from a well oxygenated nutrient rich environment at about 18 000 yr b p to a nutrient poor oxygen depleted environment from 13 000 to the present time moreover for the time span synchronous with the well known development of sapropels in the eastern mediterranean basins between 10 000 and 7000 yr b p the faunal assemblage shows most unusual characteristics implying drastic environmental conditions conversely in the gulf of cadiz the environment pass as from a biotope occupied by an oxygen depleted nutrient poor water mass at about 18 000 years b p to a biotope occupied by nadw since the younger dryas this agrees with previous data obtained in the northeastern atlantic ocean caralp 1987 in the epibathyal zones 550 800 m depth on both sides of the gibraltar strait paleohydrographic changes do not seem so important according to the present and very late holocene assemblages which are similar on both sides of the strait with a strong east west flow two other stratigraphic episodes have shown the same conditions of water exchanges the end of the isotopic stage 2 and the younger dryas conversely during the last glacial maximum the bolling allerod and the lower holocene westward water fluxes were probably lower at no time the hypothesis of a reversal or a stop in the east west exchanges between mediterranean and atlantic ocean may be justified

abrupt temperature changes in the western mediterranean over the past 250 000 years a continuous high resolution western mediterranean sea surface temperature sst alkenone record spanning the past 250 000 years shows that abrupt changes were more common at warming than at cooling during marine isotope stage mis 6 sst oscillated following a stadial interstadial pattern but at lower intensities and rates of change than in the dansgaard oeschger events of mis 3 some of the most prominent events occurred over miss 5 and 7 after prolonged warm periods of high stability climate during the whole period was predominantly maintained in interglacial interstadial conditions whereas the duration of stadials was much shorter

the last climatic cycle at kopais central greece thick lacustrine sequences from southern europe provide an opportunity to derive continuous records where the chronostratigraphical position of pre holocene stages can be determined with increased confidence here high resolution sediment and pollen analytical results from a 60 m core recovered from the kopais basin central greece spanning the interval from the last interglacial to the early holocene are presented the record shows distinct shifts between open vegetation periods of increased erosion with sediment inwashing and forest periods associated with calcite precipitation in the lake the sequence of major events of the last climatic cycle contained at kopais bears strong similarities to other records in greece but also reveals the presence of high frequency oscillations with higher amplitudes than previously seen at other sites

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

holocene climate variability in the western mediterranean region from a deepwater sediment record 1 the detailed analysis of the international marine past global changes study core md99 2343 recovered from a sediment drift at 2391 m water depth north of the island of minorca illustrates the effects of climate variability on thermohaline circulation in the western mediterranean during the last 12 kyr geochemical ratios associated with terrigenous input resulted in the identification of four phases representing different climatic and deepwater overturning conditions in the western mediterranean basin during the holocene superimposed on the general trend eight centennial to millennial scale abrupt events appear consistently in both grain size and geochemical records which supports the occurrence of episodes of deepwater overturning reinforcement in the western mediterranean basin the observed periodicity for these abrupt events is in agreement with the previously defined holocene cooling events of the north atlantic region thus supporting a strong atlanticmediterranean climatic link at high frequency time intervals during the last 12 kyr the rapid response of the mediterranean thermohaline circulation to climate change in the north atlantic stresses the importance of atmospheric teleconnections in transferring climate variability from high latitudes to midlatitudes

evidence for enhanced mediterranean thermohaline circulation during rapid climatic coolings molecular biomarkers c37 alkenones n nonacosane and n hexacosanol and toc are used together with benthic 18o and 13c data to document the hydrographic response of the western mediterranean sea to rapid climatic variability these proxies are recorded in core md 95 2043 alboran sea affording the study of the dansgaard oeschger d o and heinrich he variability during the last glacial period the results suggest that rapid changes in the western mediterranean thermohaline circulation occurred in parallel to sea surface temperature oscillations enhanced deep water ventilation occurred during cold intervals he and d o stadials probably driven by a strengthening of north westerly wind over the north western mediterranean sea in contrast decreased intensity of the thermohaline circulation is detected during warm intervals d o interstadials which led to low oxygenated deep water masses and better preservation of the organic matter in the sediment

variability of the western mediterranean sea surface temperature during the last 25 000 years and its connection with the northern hemisphere climatic changes sea surface temperature sst profiles over the last 25 kyr derived from alkenone measurements are studied in four cores from a w e latitudinal transect encompassing the gulf of cadiz atlantic ocean the alboran sea and the southern tyrrhenian sea western mediterranean the results document the sensitivity of the mediterranean region to the short climatic changes of the north atlantic ocean particularly those involving the latitudinal position of the polar front the amplitude of the sst oscillations increases toward the tyrrhenian sea indicating an amplification effect of the atlantic signal by the climatic regime of the mediterranean region all studied cores show a shorter cooling phase 700 years for the younger dryas yd than that observed in the north atlantic region 1200 years this time diachroneity is related to an intra yd climatic change documented in the european continent minor oscillations in the southward displacement of the north atlantic polar front may also have driven this early warming in the studied area during the holocene a regional diachroneity propagating west to east is observed for the sst maxima 11 5 10 2 kyr b p in the gulf of cadiz 10 9 kyr b p in the alboran sea and 8 9 8 4 kyr b p in the thyrrenian sea a general cooling trend from these sst maxima to present day is observed during this stage which is marked by short cooling oscillations with a periodicity of 730 40 years and its harmonics

sediment supply and the development of the coarse surface layer in gravel bedded rivers the bed surface of most gravel rivers is considerably coarser than the sub surface or the gravel load transported over it a phenomenon affecting river dynamics morphology and ecology the coarse surface layer often called an armour or pavement has been attributed to an inherent tendency for small grains to settle between larger ones during active transport of all sizes1 2 and to selective erosion or trapping of finer particles when the coarse grains are relatively immobile3 4 where bedload supply is cut off below dams selective erosion causes coarsening5 6 using a simple quantitative model we propose that surface coarsening develops in gravel bedded rivers when local bedload supply from upstream is less than the ability of the flow to transport that load we present laboratory results which support this hypothesis and show that supply reduction causes changes in bedforms and progressive confinement of active bedload transport to a narrow band of finer bed surface bordered by a coarse less active bed it may therefore be possible to relate the degree of river bed surface coarsening to sediment supply resulting from land use

several location methods for underwater shots in the gulf of genoa western mediterranean structural implications abstract during the egt survey 50 underwater shots were detonated on a n s section through the gulf of genoa running from the northern margin 44 12 n towards corsica 42 90 n along the 9 e meridian the aim of this work is in a first stage to establish the propagation model of regional phases in this region and consequently to improve the location of epicentres and afterwards to refine our structural knowledge of this complex crustal area the relocation of these shots was carried out with arrival times of seismic signals recorded at land stations we have used different location methods all of which led to similar crustal models they reveal a low p n velocity area in the northern ligurian sea and in the gulf of genoa with a 20 km thick crust in the southern part approximately south of latitude 43 7n a 4 km thick oceanic crust covered by 8 km of sediments is clearly confirmed using these models a significant improvement of epicentre locations was obtained these improvements to propagation models lead to the two main structural conclusions 1 1 in the southern part of the investigated area the spread of an oceanic type domain as far as the foot of the continental margin 2 2 a sharp transition between the two domains of different stretching rate the northern one with a moho depth of about 20 km and the southern one with an average moho depth of about 14 km these observations substantiate the presence of a transform margin between the rifted gulf of genoa and the oceanic type ligurian basin

a 225 kyr record of dust supply paleoproductivity and the oxygen minimum zone from the murray ridge northern arabian sea abstract analysis of a 15 m long sediment core recovered from the murray ridge northern arabian sea reveals a 225 000 year record of climate induced variations in surface water productivity mid water ventilation and dust input in the northern arabian sea productivity and dust input records closely resemble those from the owen ridge and oman margin also the phase lag of 10 kyr between maximum productivity and precession minimum is in phase with the summer monsoon upwelling record from the owen ridge and the oman margin this implies that the productivity variations in the northern arabian sea during the last 225 kyr are primarily controlled by changes in the indian ocean summer monsoon the winter monsoon obviously played a minor role in the productivity history of the northern arabian sea another result from this study is that the mg al record from the murray ridge nicely documents the post glacial flooding of the persian gulf which is the main glacial source for dolomite dust in this region finally it is concluded that the intensity of the omz co varies with surface water productivity being weak during periods of reduced summer monsoon especially during glacial periods

evidence of abrupt changes in western mediterranean deep water circulation during the last 50kyr a high resolution marine record from the balearic sea abstract the images core md99 2343 recovered from a sediment drift north of the island of minorca in the north western mediterranean sea holds a high resolution sequence that is perfectly suited to study the oscillations of the overturning system of the western mediterranean deep water wmdw detailed analysis of grain size and bulk geochemical composition reveals the sensitivity of this region to climate changes at both orbital and centennial millennial temporal scales during the last 50 kyr the dominant orbital pattern in the k al record indicates that sediment supply to the basin was controlled by the insolation evolution at 40 n which forced changes in the fluvial regime with more efficient sediment transport during insolation maxima this orbital control also modulated the long term pattern of the wmdw intensity as illustrated by the silt clay ratio however deep convection was particularly sensitive to climatic changes at shorter time scales i e to centennial millennial glacial and holocene oscillations that are well documented by all the paleocurrent intensity proxies si al ti al and silt clay ratios benthic isotopic records 13c and 18o show a dansgaard oeschger d o pattern of variability of wmdw properties which can be associated with changing intensities of the deep currents system the most prominent reduction on the wmdw overturning was caused by the post glacial sea level rise three main scenarios of wmdw overturning are revealed a strong mode during d o stadials a weak mode during d o interstadials and an intermediate mode during cooling transitions in addition d o stadials associated with heinrich events hes have a very distinct signature as the strong mode of circulation typical for the other d o stadials was never reached during he due to the surface freshening induced by the inflowing polar waters consequently the wmdw overturning system oscillated around the intermediate mode of circulation during he though surface conditions were more stable during the holocene the wmdw overturning cell still reacted synchronously to short lived events as shown by increments in the planktonic 18o record triggering quick reinforcements of the deep water circulation overall these results highlight the sensitivity of the wmdw to rapid climate change which in the recent past were likely induced by oceanographic and atmospheric reorganizations in the north atlantic region

variable bottom water in the western mediterranean basin the deep water of the western mediterranean has long been considered to have practically constant values of s and between 1909 1910 the thor expedition and the 1970 cruise of the jean charcot the deep water at more than 1800 m depth showed very little variation the small changes which appeared through the years could be due in part to changes in instrumentation analysis and methods of sampling in 1972 and 1973 during the medoc cruises a bottom layer of 200 300 m thickness was found its temperature and salinity showed a small gradient producing at the bottom an increase of potential temperature of about 0 01 to 0 02 c and an increase in salinities of about 0 010 00 relative to a minimum of and s in the deep water at 1800 2000 m these minima of and s were found to be homogeneous horizontally at all stations occupied in the medoc area and in the ligurian sea in 1973 interestingly the bottom layer was not present in 1974 however in november 1981 during the cruise mediprod iv the variable bottom water was again present extending from the ligurian sea and medoc areas along the western coasts of corsica and sardinia to the eastern alboran sea in most cases the maximum values of and s were recorded at the bottom and were higher than the 1973 values by about 0 03 c and up to 0 0150 00 but with a rather high spatial variability by february 1982 cruise dyome ii the situation had become more complicated not only was a layer of minimum and s present but it was underlain by a layer of maximum and s below which a decrease appeared producing a new minimum at the very bottom in addition a number of stations displayed higher values of by about 0 05 c and of s by about 0 0150 00 in the layers of minimum and maximum characteristics as well as on the bottom in contrast to the situation in 1973 high spatial variability was found in the deep layering the variability may have been due to patchy deep convention activity possibly in the ligurian sea the phenomenon of variable bottom water and the processes which produce it may be relevant to our understanding of water mass formation

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

wood mediated geomorphic effects of a jokulhlaup in the wind river mountains wyoming a jokulhlaup burst from the head of grasshopper glacier in wyoming s wind river mountains during early september 2003 five reaches with distinct sedimentation patterns were delineated along the dinwoody creek drainage this paper focuses on a portion of the jokulhlaup route where erosion of the forested banks created 16 large logjams spaced at longitudinal intervals of tens to hundreds of meters aggradation within the main channel upstream from each logjam created local sediment wedges and the jams facilitated overbank deposition during the jokulhlaup field surveys during 2004 and 2006 documented logjam characteristics and associated erosional and depositional features as well as initial modification of the logjams and flood deposits within the normal seasonal high flow channel overbank deposits have not been altered by flows occurring since 2003 field measurements supported three hypotheses that i logjams present along the forested portions of the jokulhlaup route are larger and more closely spaced than those along adjacent otherwise comparable stream channels that have not recently experienced a jokulhlaup ii logjams are not randomly located along the jokulhlaup route but instead reflect specific conditions of channel and valley geometry and flood hydraulics and iii the presence of logjams facilitated significant erosional and depositional effects this paper documents a sequence of events in which outburst floodwaters enhance bank erosion and recruitment of wood into the channel and thus the formation of large logjams these logjams sufficiently deflect flow to create substantial overbank deposition in areas of the valley bottom not commonly accessed by normal snowmelt peak discharges and through this process promote valley bottom aggradation and sediment storage changes in the occurrence of glacier outburst floods thus have the potential to alter the rate and magnitude of valley bottom dynamics in these environments which is particularly relevant given predictions of worldwide global warming and glacial retreat processes observed at this field site likely occur in other forested catchments with headwater glaciers

cyclic variations in the chemical composition of eastern mediterranean pliocene sediments a key for understanding sapropel formation abstract two pliocene mediterranean sediment cores from ocean drilling program odp leg 160 sites 964 pisano plateau ionian basin and 967 lower northern slope of eratosthenes seamount south of cyprus have been analyzed for major and minor elements si ti al fe mg ca k ba cr ni v zn zr by x ray fluorescence analysis at a depth resolution of 3 to 4 cm a total of 430 samples core 964c 9h comprises five sapropels with up to 9 7 total organic carbon toc one 2 5 m thick turbidite and a 50 cm segment of a second turbidite whereas core 967b 9h contains eight sapropels with toc contents of up to 6 7 cyclic variations in carbonate content and detrital matter composition are evident at both sites at site 964 pisano plateau terrigenous detrital matter chemistry reflects periods of stronger saharan dust input higher si al and zr al ratios alternating with fluvial input from the northern borderlands higher mg al ratios cyclicity is not well expressed at this location because turbidites and winnowing occur site 967 eratosthenes seamount sediments are strongly influenced by discharge from the nile river during humid periods low k al and mg al ratios at site 967 sapropels occur only during periods of enhanced nile discharge with correspondingly lower si al ti al mg al k al and zr al ratios accumulation rates of carbonate and terrigenous detrital matter were 30 lower during such episodes because of the reduction in eolian input and carbonate production and or carbonate dissolution periodical ba enrichments which are not only seen in the sapropels but in every k al minimum document the association of enhanced bioproductivity and sapropel formation as calculated from excess ba concentrations productivity increased by up to a factor of five during intervals of intensified nile runoff fluviatile discharge seems to be responsible for an enhanced input of nutrients and suspended matter containing low mg al and k al ratios based on organic carbon concentrations episodes of sapropel formation lasted at least from 1000 to 4000 years at site 964 and from 2000 to 6000 years at site 967 periods of enhanced bio productivity as defined by ba enrichments lasted from 8000 to 12 000 years at site 967 episodes of high river discharge and corresponding nutrient input as well as conditions of sapropel formation seem to have lasted longer in the eastern part of the basin site 967 than at the pisano plateau site 964

floods in mountain environments a synthesis floods are a crucial agent of geomorphic change in the channels and valley floors of mountains watercourses at the same time they can be highly damaging to property infrastructure and life because of their high energy mountain watercourses are highly vulnerable to environmental changes affecting their catchments and channels many factors have modified and frequently still tend to modify the environmental conditions in mountain areas with impacts on geomorphic processes and the frequency magnitude and timing of floods in mountain watercourses the ongoing climate changes vary between regions but may affect floods in mountain areas in many ways in many mountain regions of europe widespread afforestation took place over the twentieth century considerably increasing the amounts of large wood delivered to the channels and the likelihood of jamming bridges at the same time deforestation continues in other mountain areas accelerating runoff and amplifying the magnitude and frequency of floods in foreland areas in many countries in channel gravel mining has been a common practice during recent decades the resultant deficit of bed material in the affected channels may suddenly manifest during flood events resulting in the failure of scoured bridges or catastrophic channel widening during the past century many rivers in mountain and foreland areas incised deeply the resultant loss of floodplain water storage has decreased attenuation of flood waves hence increasing flood hazard to downstream river reaches on the other hand a large amount of recent river restoration activities worldwide may provide examples of beneficial changes to flood risk attained as a result of increased channel storage or reestablished floodplain water storage relations between geomorphic processes and floods operate in both directions which means that changes in flood probability or the character of floods e g increased wood load may significantly modify the morphology of mountain rivers but morphological changes of rivers can also affect hydrological properties of floods and the associated risk for societies this paper provides a review of research in the field of floods in mountain environments and puts the papers of this special issue dedicated to the same topic into context it also provides insight into innovative studies methods or emerging aspects of the relations between environmental changes geomorphic processes and the occurrence of floods in mountain rivers

mediterranean outflow strengthening during northern hemisphere coolings a salt source for the glacial atlantic abstract high resolution grain size and magnetic susceptibility records from the eastern gulf of cadiz site md99 2339 1170 m water depth reveal contourites formed by the mediterranean outflow mow during the last 47 kyr bp oscillations in the mow s intensity occurred in phase with greenland temperature variations with a stronger outflow during northern hemisphere coolings such as dansgaard oeschger stadials heinrich events and the younger dryas benthic 13c data implies the western mediterranean deep water as one of the main sources feeding the outflow current while differential changes in the properties of the mediterranean source and entrained north atlantic central water largely control the mow s strength detailed studies for heinrich events 1 4 and 5 show that the flow strength peaked only when subtropical surface waters prevailed in the eastern gulf of cadiz while incursions of icebergs and subpolar surface water were not favorable for the mow s intensification as the mow was strong when the atlantic s thermohaline circulation thc was weakened the heat and salt injected by the mow into the intermediate north atlantic waters might have preconditioned the thc to switch from the stadial to the interstadial mode

evidence for massive discharges of icebergs into the north atlantic ocean during the last glacial period sediments in the north atlantic ocean contain a series of layers that are rich in ice rafted debris and unusually poor in foraminifera1 here we present evidence that the most recent six of these heinrich layers deposited between 14 000 and 70 000 years ago record marked decreases in sea surface temperature and salinity decreases in the flux of planktonic foraminifera to the sediments and short lived massive discharges of icebergs originating in eastern canada the path of the icebergs clearly marked by the presence of ice rafted detrital carbonate can be traced for more than 3 000 km a remarkable distance attesting to extreme cooling of surface waters and enormous amounts of drifting ice the cause of these extreme events is puzzling they may reflect repeated rapid advances of the laurentide ice sheet perhaps associated with reductions in air temperatures yet temperature records from greenland ice cores appear to exhibit only a weak corresponding signal moreover the 5 10 000 yr intervals between the events are inconsistent with milankovitch orbital periodicities raising the question of what the ultimate cause of the postulated cooling may have been

quantification of physical ripening in an unripe marine clay soil abstract the process of physical ripening of a soil developed on recently exposed marine clay has been studied in detail by examining the swelling of soil clods subjected to a number of drying and wetting cycles during the wetting cycle solutions with three different cacl2 concentrations were used to study the effect of salts on the swelling the swelling behaviour was represented by a linear swelling characteristic showing that the concentration of solutions clearly influences the swelling based on the swelling characteristics quantitative aspects of physical ripening were investigated in terms of the irreversibility of extracted soil water a linear relationship was noted between the moisture ratio at the threshold of irreversible extraction and the initial moisture ratio based on the relationship a physical ripening index pri is proposed which can be used together with the initial moisture ratio to indicate stages in the ripening process for these soil materials a greater proportion of water could be reversibly extracted from soils which had undergone increasing degrees of ripening

enhanced aridity and atmospheric high pressure stability over the western mediterranean during the north atlantic cold events of the past 50 k y multiproxy paleoenvironmental records pollen and planktonic isotope from ocean drilling program site 976 alboran sea document rapid ocean and climate variations during the last glacial that follow the dansgaard oeschger climate oscillations seen in the greenland ice core records thus suggesting a close link of the mediterranean climate swings with north atlantic climates continental conditions rapidly oscillated through cold arid and warm wet conditions in the course of stadial interstadial climate jumps at the time of heinrich events i e maximum meltwater flux to the north atlantic western mediterranean marine microflora and microfauna show rapid cooling correlated with increasing continental dryness enhanced aridity conceivably points to prolonged wintertime stability of atmospheric high pressure systems over the southwestern mediterranean in conjunction with cooling of the north atlantic

plio pleistocene evolution of the var deep sea fan off the french riviera abstract the var deep sea fan was deposited during the pliocene and quaternary seaward progradation of the var delta within a steep sided flat floored basin formed during the messinian salinity crisis the prominent palaeo var canyon was cut on the slope at the same time following the early pliocene transgression var sediments were initially trapped in the coastal ria formed by sea level incursion of the head of the messinian valley by middle pliocene time gilbert type deltas had prograded to the break of slope modern coastline allowing coarse sediment to reach the basin quaternary coastal uplift and sediment supply from the glaciated alps resulted in a supply of coarse sediment to the fan by the braided var river throughout the quaternary even during sea level highstands such as the present in the earliest pliocene hemipelagic clays accumulated while coarse sediment was trapped in the var ria through the rest of the pliocene a leveed fan valley extended southward from the var canyon which periodically switched locations through avulsion to the east at about the beginning of the quaternary this eastward spillover channel became the main distributary and re occupation of the older south trending channels was blocked by rapid levee progradation and aggradation of mud waves by overbanking of turbidity flows on the var sedimentary ridge during the quaternary channel shifting to the north occurred the quaternary var fan has an unusually steep concave longitudinal profile compared with most passive margin fans the laurentian fan has a similar profile to the var both have a high levee and a gravel and pebble floored fan valley that is essentially a bypass zone compared with the aggradational channel levee systems with lower levees in most passive margin fans this is a consequence of the constant supply of coarse sand gravel and pebbles to the fan even during highstands of sea level the erosive capability of this coarse sediment in ignitive turbidity currents resulted in flushing out of the upper and middle fan valley system thick muddy turbidity currents probably resulting from slumping caused by canyon incision produced the prominent mud waves on the levee the concave longitudinal profile led to rapid sediment deposition at critical points in the valley system as a result of turbidity flow expansion this in turn promoted the development of a left hook in the valley system

relationships between shrinkage indices and soil properties in some new zealand soils abstract shrinkage is a physical process that has profound effects on the agricultural and engineering use of soil this study was undertaken to assess the shrinkage potential of different new zealand soils using the coefficient of linear extensibility cole and to examine relationships between soil shrinkage and selected chemical physical and mineralogical soil properties results indicate that there is a wide range in the shrinkage capacities of different soils with cole values between 0 050 and 0 313 allophane dominated soil samples showed the largest soil shrinkage followed by montmorillonite and halloysite samples with the least shrinkage occurring in the kaolinite vermiculite and chlorite illite dominated samples there was a significant statistical relationship found between cole std determined using natural soil aggregates and cole rod determined using remoulded soil samples r 2 0 85 p std and cole rod were found to be significantly related to specific surface area and soil clay content and inversely related to bulk density cole rod was also significantly related to cec no relationships were found between shrinkage indices and organic matter multiple regression models with terms for specific surface area and clay content could explain 76 and 81 of the variance in shrinkage determined by cole rod and cole std respectively

promotion of meridional overturning by mediterranean derived salt during the last deglaciation we demonstrate that changes in the behavior of the mediterranean outflow water mow prior to and through the last deglaciation played an important role in promoting meridional overturning circulation moc estimation of past mow salt and heat fluxes indicates that they gradually increased through the last deglaciation between 17 5 and 14 6 thousand years ago ka b p where b p references year 1950 net evaporation from the mediterranean exported sufficient fresh water from the north atlantic catchment to cause an average salinity increase of 0 5 psu throughout the upper 2000 m of the entire north atlantic to the north of 25

sortable silt and fine sediment size composition slicing parameters for palaeocurrent speed and palaeoceanography fine sediment size 63 ixm is best measured by a sedimentation technique which records the whole size distribution repeated size measurement with intermediate steps of removal of components by dissolution allows inference of the size distribution of the removed component as well as the residue in this way the size of the biogenic and lithogenic noncarbonate fractions can be determined observations of many size distributions suggest a minimum in grain size frequency curves at 8 to 10 ixm the dynamics of sediment erosion deposition and aggregate breakup suggest that fine sediment behavior is dominantly cohesive below 10 1xm grain size and noncohesive above that size thus silt coarser than 10 ixm displays size sorting in response to hydrodynamlc processes and its properties may be used to infer current speed silt that is f mer than 10 ixm behaves in the same way as clay 2 xm useful parameters of the distribution are the 10 63 ixm mean size and the percentage 10 63 ixm in the fine fraction we cannot use size distributions to distinguish the nature of the currents therefore to infer water mass advection speeds i e the mean kinetic energy of the flow ku regions of high eddy kinetic energy ke must be avoided at the present such abyssal regions lie under the high surface k e of major current systems gulf stream kuroshio agulhas antarctic circmpolar current and brazil falldand currents in the argenthe basin this is probably a satisfactory guide for the pleistocene with regard to the carbonate subfraction of the size spectrum size modes due to both cocco iths and foramlnlferal fragments can be recognized and analyzed with the boundary between them again at about 10 lm the flux of less than 10 lm carbonate at pelagic sites above the lysocline is another candidate for a productivity indicator

european lakes as palaeohydrological and palaeoclimatic indicators abstract lakes in temperate regions have fluctuated in size on annual to millenial time scales changes in water level or depth can be reconstructed by applying geomorphic sedimentological and biostratigraphic methods to transects of sediment cores this systematic field based approach has been used at a number of sites in europe it is illustrated by reconstructions of water level changes in lakes from southern sweden these lakes have shown broadly synchronous changes during the holocene such synchronous changes in water levels at several sites in a region reflect climatic changes inferences about the mechanism of the climatic change depend on identifying both synchronous changes within a region and differences in the direction magnitude and timing of lake level changes between regions continental compilations of lake level data are therefore necessary detailed studies are not available from enough sites but the interpretation of already existing stratigraphic and biostratigraphic data in terms of lake level changes has greatly increased the number of sites available for a continental scale synthesis in europe this eclectic literature based approach is illustrated with examples from southern europe lakes in the mediterranean region were high around the glacial maximum and again somtime during the first half of the holocene in the western mediterranean the peak of late glacial aridity occurred at 15 000 16 000 bp and the lakes were already high again by 12 000 bp in the east maximum late glacial aridity occurred between 13 000 and 11 000 bp and there was a gradual return to wetter climates during the early holocene such that 9000 bp was more arid than 6000 bp most lakes in the mediterranean region were high at 6000 bp the transition to arid conditions after 5000 bp occurred abruptly in the west and more gradually in the east the lakes of southern sweden indicate drier climates in the early holocene ca 9000 bp more effective moisture between 8000 and 6000 bp increased aridity between 5500 and 3500 bp and increased effective moisture again during the last 3000 years the history of lake level changes in southern sweden and the mediterranean region can be partially explained in terms of changes in the direct effects of insolation and in the strength and position of the westerlies and of the subtropical high pressure cell during the late quaternary

review and new aspects concerning the formation of eastern mediterranean sapropels abstract in this paper it is proposed that the formation of eastern mediterranean sapropels occurred in an anti estuarine type of circulation which was to some degree weakened relative to the present in response to reduction of the eastern mediterranean excess of evaporation over freshwater input this reduction of excess evaporation would have been imposed by intensifications of 1 the indian ocean summer sw monsoon influencing the eastern mediterranean via increased nile discharge and 2 the system of mediterranean depressions an element of the westerly atlantic system causing increased precipitation and decreased evaporation both the indian ocean summer monsoon and the westerly atlantic system would be intensified in response to the occurrence of distinct minima in the cycle of precession it is demonstrated that reduced excess evaporation whether or not coinciding with global phases of deglaciation would lead to reduction of surface water salinities in the eastern mediterranean causing isolation of previously formed high salinity cooler deep water thus mixing was severely reduced possibly even restricted to eddy diffusion with only occasional convective events that because of the existing density gradient hardly ever would reach the deepest parts of the basin the consequently diminished oxygen advection down from a few hundred meters in the water column favoured preservation of the sinking organic matter this would however suffice only to enable the formation of sapropels with low organic carbon contents the high organic carbon contents observed in various sapropels are argued to reflect superimposed increases of export production the described scenario accounts for previously reported 1 increases of organic carbon content with increasing depth of deposition within individual sapropels and 2 asymmetrical sequences of sapropel deposition characterized by gradual build up and rather abrupt ending it is furthermore in agreement with 3 isotopic and faunal reconstructions of the history of exchange transports through both the strait of sicily and the strait of gibraltar and 4 faunal and floral reflections of the presence or absence of a distinct deep chlorophyll maximum with its associated increases in export production indicating the presence or absence of a shallow pycnocline within the euphotic layer moreover the described scenario 5 is in no way conflicting with the reports of sapropels in the western mediterranean and 6 seems to be endorsed by occasionally intercalated intervals suggestive of somewhat improved oxygenation amidst anoxic benthic desert levels a situation that has been observed in a few quaternary and pliocene sapropels