tectonic and environmental evolution of quaternary intramontane basins in southern apennines italy insights from palaeomagnetic and rock magnetic investigations summary southern apennines is characterized by active extensional tectonics with ne sw stretching direction the seismicity of the region is very well understood and continuously monitored in contrast the onset of extensional tectonics is chronologically poorly constrained the aim of this study is that to give important constraints on the development of extensional regime and the onset of the continental deposition during quaternary in southern apennines we report the results of palaeomagnetic and rock magnetic analyses from four quaternary small intramontane basins in the picentini mountains southern apennines the sedimentary sequences are located at different altitudes from 600 to 1200 m a s l and were deposited in fluvial lacustrine environments we sampled 29 sites in clays and lacustrine limestones from tizzano piano del gaudo and acerno basins and in red palaeosoils and matrix supported conglomerates from the iumaiano basins in the clay and limestones samples magnetite titano magnetite hematite and iron sulphide have been recognized as the main magnetic carriers whereas magnetite and hematite characterize the iumaiano conglomerates and red soils palaeomagnetic results have been integrated with published radiometric data in order to constrain the age of each sedimentary basins sites from the iumaiano basin which represents the substrate of the tizzano and piano del gaudo basins show a reverse polarity and therefore have been attributed to the lower matuyama chron in contrast palaeomagnetic data from tizzano basin show a transition from reversed to normal polarity along the exposed section which has been interpreted as the matuyama brunhes transition sites from acerno and piano del gaudo basins show a normal polarity which according to radiometric and pollen data have been correlated to the brunhes epoch on the base of such results we discuss the tectonostratigraphic evolution of the basins and the role of extensional tectonics in this portion of the southern apennine during the quaternary

latest miocene to quaternary horizontal and vertical displacement rates during simultaneous contraction and extension in the southern apennines orogen italy foreland contraction and hinterland extension in the southern apennines orogen of italy produced a complex spatial and temporal pattern of vertical and horizontal displacement remarkably late miocene to mid pleistocene foreland migration of the contractional front at 16 mm yr 1 was not accompanied by uplift and the frontal thrust belt remained at or below sea level only following a mid pleistocene reduction in horizontal displacement did the frontal thrust belt and foreland begin uplift at 0 5 mm yr 1 a rate that increased to 1 mm yr 1 after 125 ka although the extensional hinterland experienced net subsidence during formation of the tyrrhenian basin an extensional transition zone adjacent to the frontal thrust belt records sustained uplift at 0 3 mm yr 1 the interaction of preexisting crustal structure and deep tectonic processes resulted in time integrated displacement rates suggesting steady state deformation for periods of 106 years displacement rate changes were abrupt and occurred over intervals of 105 years or less

central arctic surface ocean environment during the past 80 000 years stable oxygen and carbon isotope and sedimentological paleontological investigations supported by accelerator mass spectrometry 14 c datings were carried out on cores from north of 85 degrees n in the eastern central arctic ocean significant changes in accumulation rates provenance of ice rafted debris ird and planktic productivity over the past 80 000 years are documented during peak glacials i e oxygen isotope stages 4 and 2 the arctic ocean was covered by sea ice with decreased seasonal variation limiting planktic productivity and bulk sedimentation rates in early stage 3 and during termination i major deglaciations of the circum arctic regions caused lowered salinities and poor oxygenation of central arctic surface waters a meltwater spike and an associated ird peak dated to similar to 14 12 14 c ka can be traced over the southern eurasian basin of the arctic ocean this event was associated with the early and rapid deglaciation of the marine based barents sea ice sheet a separate termination ib meltwater event is most conspicuous in the central arctic and is associated with characteristic dolomitic carbonate ird this lithology suggests an origin of glacial ice from northern canada and northern greenland where lower paleozoic platform carbonates crop extensively out

ice moraine and landslide dams in mountainous terrain we review recent work on ice moraine and landslide dams in mountainous terrain thus complementing several comprehensive summaries on glacier dams in intracontinental and arctic areas of low relief we discuss the roles of tectonic and climatic forcing on ice moraine and landslide dam formation and sudden drainage and focus on similarities and differences between their geomorphic impacts on confined valleys drained by steep bedrock and gravel bed rivers despite numerous reported failures of natural dams in mountain belts throughout the world their relevance to long term dynamics of mountain rivers remains poorly quantified all types of dams exert local base level controls thus trapping incoming sediment and inhibiting fluvial bedrock incision pervasive geomorphic and sedimentary evidence of outburst events is preserved even in areas of high erosion rates suggesting that sudden dam failures are characterized by processes of catastrophic valley floor aggradation active channel widening and downstream dispersion of sediment during which little bedrock erosion seems to be achieved we find that in the absence of direct evidence of former dams a number of similarities among the geomorphic and sedimentologic characteristics of catastrophic outburst flows may give rise to ambiguous inferences on the dam forming process this is especially the case for tectonically active mountain belts where there is ample and comparable potential for the formation and failure of ice moraine landslide and polygenetic dams concomitant with climatic oscillations or earthquake disturbance hence the palaeoclimatic implications of erroneously inferring the cause of dam formation may be significant we recommend that future research on natural dams in mountainous terrain addresses a climate and earthquake controlled systematics in the pattern of formation and failure b quantification of response of mountain rivers to catastrophic outburst events and their concomitant process sequences c elaboration of a comprehensive classification of natural dams in mountainous terrain with special attention to polygenetic dams d physical based modelling of dam formation failure and routing of water and sediment outbursts and e quantitative controls on the contribution of natural dams to sediment budgets in mountainous terrain

paleoglaciation of the tibetan plateau and surrounding mountains based on exposure ages and ela depression estimates the tibetan plateau holds an ample record of past glaciations and there is an extensive set of glacial deposits dated by exposure dating here a compilation is presented of 10be exposure ages from 485 glacial deposits with 1855 individual samples on the tibetan plateau and ela depression estimates for the glacial deposits based on a simple toe to headwall ratio approach to recalculate the tibetan plateau exposure ages 10be production rates from 24 calibration sites across the world are compiled and recalibrated yielding an updated global reference 10be production rate the recalculated exposure ages from the tibetan plateau glacial deposits are then divided into three groups based on exposure age clustering to discriminate good well clustered from poor scattered deglaciation ages a major part of the glacial deposits have exposure ages affected by prior or incomplete exposure complicating exposure age interpretations the well clustered deglaciation ages are primarily from mountain ranges along the margins of the tibetan plateau with a main peak between 10 and 30 ka indicating glacial advances during the global lgm a large number of deglaciation ages older than 30 ka indicates maximum glaciation predating the lgm but the exposure age scatter generally prohibits accurate definition of the glacial chronology the ela depression estimates scatter significantly but the main part is remarkably low average ela depressions of 337 197 m for the lgm and 494 280 m for the pre lgm indicate restricted glacier expansion

geometry kinematics and deformation rates along the active normal fault system in the southern apennines implications for fault growth throw rates throws and kinematic data have been collected from a localised system of active normal faults in the southern apennines italy to assess how its growth history differs from that for a distributed fault system in the central apennines both show evidence for fault interaction in that 1 faults located centrally along strike have higher throws and throw rates than distal faults and 2 cumulative throw and throw rate profiles summed across strike show central maxima with values decreasing to zero at fault system tips however although throw rates increased through time in the central apennines we are unable to resolve such changes if they exist for the southern apennines specifically throw rates derived from offsets of 18 ka geomorphic surfaces are consistent with total throws in the southern apennines when extrapolated back through time but overestimate total throws in the central apennines by a factor of 2 4 suggesting an increase in throw rate through time for the latter we discuss why some fault systems appear to have throw rates that are constant through time whilst others accelerate during growth interaction

a geologically constrained monte carlo approach to modeling exposure ages from profiles of cosmogenic nuclides an example from lees ferry arizona we present a user friendly and versatile monte carlo simulator for modeling profiles of in situ terrestrial cosmogenic nuclides tcns our program available online at http geochronology earthsciences dal ca downloads models html permits the incorporation of site specific geologic knowledge to calculate most probable values for exposure age erosion rate and inherited nuclide concentration while providing a rigorous treatment of their uncertainties the simulator is demonstrated with 10be data from a fluvial terrace at lees ferry arizona interpreted constraints on erosion based on local soil properties and terrace morphology yield a most probable exposure age and inheritance of 83 9 14 1 19 1 ka and 9 49 2 52 1 21 104 atoms g 1 respectively 2 without the ability to apply some constraint to either erosion rate or age shallow depth profiles of any cosmogenic nuclide except for nuclides produced via thermal and epithermal neutron capture e g 36cl cannot be optimized to resolve either parameter contrasting simulations of 10be data from both sand and pebble sized clasts within the same deposit indicate grain size can significantly affect the ability to model ages with tcn depth profiles and when possible sand not pebbles should be used for depth profile exposure dating

paleohydraulic reconstruction of the largest glacial lake missoula draining s glacial lake missoula glm was the source of earth s largest known peak flood discharges onto the channeled scabland northwestern united states the original studies of glm were based on geomorphological mapping of lake sediments and shorelines more recently studies have emphasized the computational fluid dynamics of downstream megaflood routing and characteristics in the channeled scabland and adjacent areas however actual details of the lake draining processes glm have received little scientific attention in this paper we employ two dimensional hydraulic modelling to understand the paleoflow conditions for different scenarios of draining glm at its highest stands values are calculated for three glm drainage hydrographs 2 6 13 17 10 6 m 3 s 1 that previous studies had estimated for outlet flows consistent with regional mapping and with the original interpretation of fluvial geomorphology by other studies the modelling shows that lake silt sequences in the gorges of glm must postdate the most highly energetic outburst events from the lake this is because the flows generated in the lake by megaflood outflows are sufficiently energetic to erode any accumulated silt deposits in contrast the gravels underlying the silts in these zones include boulder sized clasts largescale cross stratification and 70e100 m high bars forms all of which indicate very high energy flood flow conditions the modelling also shows that the paleohydraulic conditions which developed in the lake basin during the largest megaflood outflows would be capable of accounting for the observed bedrock scour at rainbow lake pass various high eddy deposits eddy bars of flood gravel in gorges and the giant ripple marks subaqueous gravel dunes that were classically described in the 1940s previous studies interpreted the glacial lake silt rhythmites and related deposits such as the ninemile section as evidence for numerous fillings and drainings of glm our modelling suggests that these inferred events must have been relatively low in energy and magnitude relative to the earlier outburst s that emplaced the flood gravels subaqueous gravel dunes and scabland like erosion surfaces

reconciliation of late quaternary sea levels derived from coral terraces at huon peninsula with deep sea oxygen isotope records a major discrepancy between the late quaternary sea level changes derived from raised coral reef terraces at the huon peninsula in papua new guinea and from oxygen isotopes in deep sea cores is resolved the two methods agree closely from 120 ka to 80 ka and from 20 ka to 0 ka ka 1000 yr before present but between 70 and 30 ka the isotopic sea levels are 20 40 m lower than the huon peninsula sea levels derived in earlier studies new high precision u series age measurements and revised stratigraphic data for huon peninsula terraces aged between 30 and 70 ka now give similar sea levels to those based on deep sea oxygen isotope data planktonic and benthic 18o data using the sea level and deep sea isotopic data oxygen isotope ratios are calculated for the northern continental ice sheets through the last glacial cycle and are consistent with results from greenland ice cores the record of ice volume changes through the last glacial cycle now appears to be reasonably complete

an ams radiocarbon method to determine the emplacement time of recent deep sea turbidites abstract this paper reports the evaluation of a novel method based on accelerator mass spectrometer ams radiocarbon dating of planktonic foraminifera to evaluate the times of emplacement of recent deep sea turbidites it assumes that the standing stock of relatively large 150 m planktonic foraminifera in the bioturbated surface mixed layer of box cores represents an integration of the flux from the water column since the turbidite was emplaced and exploits the potential of the ams method to analyse the resultant small samples which can be readily separated the method is evaluated by application to three atlantic turbidites which form the present day sediment surfaces on the horseshoe madeira and tagus abyssal plains the time of emplacement of madeira abyssal plain turbidite is estimated at 1120 730 and 870 years before present each 120 140 years in three different cores the resultant weighted mean emplacement time 930 76 years before present is somewhat older than previous estimates by geochemical methods the times of emplacement for the horseshoe 240 and 140 years before present each 120 years and tagus 300 120 years before present abyssal plains are both consistent with initiation by the lisbon earthquake of 1755

ice dammed lakes and rerouting of the drainage of northern eurasia during the last glaciation during the quaternary period ice sheets centred over the barents and kara seas expanded several times onto mainland russia and blocked northflowing rivers such as the yenissei ob pechora and mezen large ice dammed lakes with reversed outlets e g toward the caspian sea formed south of these ice sheets some lakes are reconstructed from shorelines and lacustrine sediments others mainly from ice sheet configuration ice dammed lakes considerably larger than any lake on earth today are reconstructed for the periods 90 80 and 60 50 ka the ages are based on numerous optically stimulated luminescence osl dates during the global last glacial maximum lgm about 20 ka the barents kara ice sheet was too small to block these eastern rivers although in contrast to the 90 80 and 60 50 ka maxima the scandinavian ice sheet grew large enough to divert rivers and meltwater across the drainage divide from the baltic basin to the river volga and that way to the caspian sea climate modelling shows that the lakes caused lower summer temperatures on the continent and on the lower parts of the ice sheet the final drainage of the best mapped lake is modelled and it is concluded that it probably emptied within few months we predict that this catastrophic outburst had considerable impact on sea ice formation in the arctic ocean and on the climate of a much larger area c 2003 elsevier ltd all rights reserved less

geomorphological paleontological and 87sr 86sr isotope analyses of early pleistocene paleoshorelines to define the uplift of central apennines italy abstract the eastern border of the middle valley of the tiber river is characterized by several plio pleistocene paleoshorelines which extend for about 100 km along the western margin of the central apennines italy we studied these paleoshorelines by the means of geological and paleontological analyses and new 87 sr 86 sr isotope analyses the youngest and uppermost paleoshorelines have been detected and mapped through detailed geologic and stratigraphic surveys which led to the recognition of nearshore deposits cliff breccias alignments of lithophaga borings fossil abrasion notches and wave cut platforms the altitude of these paleoshorelines decreases almost regularly in the nnw sse direction from 480 to 220 m a s l measurements of the 87 sr 86 sr isotope ratio have been conducted on corals and mollusks collected from sediments outcropping close to the paleoshorelines the isotopic dating results indicate numerical values that range between 0 70907 and 0 70910 all over the 100 km outcrop these results together with biostratigraphic data constrain the age of the youngest paleoshorelines to 1 65 1 50 ma these paleoshorelines are thus considered almost isochronous giving an estimated uplift rate of 0 34 0 17 0 03 mm a moving from nnw to sse shape length and continuity of the 100 km long observed movements indicate that the studied paleoshorelines are an important marker of the quaternary uplift of the central apennines

tectono stratigraphic modelling of the sardinian margin of the tyrrhenian sea rifting of the east sardinia passive margin was characterised by a southeastward migration of the site of extension through time in the first stage of rifting 9 7 ma lithospheric thinning was mainly localised near sardinia crustal and subcrustal thinning factors averaged across the whole transect were 1 12 and 1 5 respectively at 7 ma i e immediately before the onset of the messinian salinity crisis the basin floor was at depths of up to 1000 m in the west and less than few hundred metres in the east during the second stage of rifting between 7 and 5 ma the site of main extension was located in the central part of the future margin with average crustal and subcrustal thinning factors of 1 18 and 1 63 respectively at 5 ma after the termination of the messinian salinity crisis the morphology of the basin floor had changed substantially with depths in general between 700 and 1000 m extension during the last rifting stage before oceanic crust formation at 3 5 ma was mainly concentrated in the southeastemmost part of the profile average crustal thinning factors increased dramatically to i 95 while the subcrustal one remained almost unchanged 1 64 the analysis of temporal changes of thinning factors shows that the opening of the tyrrhenian oceanic basin can be adequately explained with a depth dependent pure shear geometry with crustal and subcrustal thinning being accommodated on the same vertical column subcrustal thinning factors in the initial stages of rifting were higher than the crustal ones but the two become comparable approaching break up the regional compensation of changing loads coupled with a very deep depth of necking is consistent with the observed subsidence trend and basin stratigraphy

an end to the last interglacial highstand before 120 ka relative sea level evidence from infreschi cave southern italy abstract the timing duration and evolution of sea level during the marine isotope stage 5e mis 5e highstand is a subject of intense debate a major problem in resolving this debate is the difficulty of chronologically constraining the sea level fall that followed the peak of the highstand this was mainly controlled by ice sheet dynamics the understanding of which is relevant for assessing future sea level behavior due to global warming here we use stratigraphical and geochoronological u th dating and tephra fingerprinting evidence from the infreschi archaeological cave marina di camerota southern italy to constrain relative sea level rsl evolution during the mis 5e highstand and younger stages uranium thorium dating of speleothem deposition phases places the maximum highstand rsl at 8 90 0 6 m a s l as indicated by the near horizontal upper limit of lithophaga boreholes measured for along a 3 5 km coastal cliff section geochronological data show that rsl fell more than 6 m before 120 ka suggesting a duration of the last interglacial highstand significantly shorter than proposed in some previous studies modelling shows that the rsl trend predicted by the ice 5g and ice 6g ice sheet simulations is consistent with our data but requires an additional significant reduction of both greenland and antarctic ice sheets to match the height of the local maximum highstand if no correction for tectonics is applied reconciling field data and models requires an earlier and likely shorter duration of the mis 5e highstand this suggests that our new data can constrain global ice volume variations during the penultimate deglaciation as well as glacial inception at the end of the last interglacial according to our chronology there is no local evidence of higher than present day sea levels after 120 ka

late quaternary ice sheet history of northern eurasia the maximum limits of the eurasian ice sheets during four glaciations have been reconstructed 1 the late saalian 140 ka 2 the early weichselian 100 80 ka 3 the middle weichselian 60 50 ka and 4 the late weichselian 25 15 ka the reconstructed ice limits are based on satellite data and aerial photographs combined with geological field investigations in russia and siberia and with marine seismic and sediment core data the barents kara ice sheet got progressively smaller during each glaciation whereas the dimensions of the scandinavian ice sheet increased during the last ice age the barents kara ice sheet attained its maximum size as early as 90 80 000 years ago when the ice front reached far onto the continent a regrowth of the ice sheets occurred during the early middle weichselian culminating about 60 50 000 years ago during the late weichselian the barents kara ice sheet did not reach the mainland east of the kanin peninsula with the exception of the nw fringe of taimyr a numerical ice sheet model forced by global sea level and solar changes was run through the full weichselian glacial cycle the modeling results are roughly compatible with the geological record of ice growth but the model underpredicts the glaciations in the eurasian arctic during the early and middle weichselian one reason for this is that the climate in the eurasian arctic was not as dry then as during the late weichselian glacial maximum

glacial lake vitim a 3000 km3 outburst flood from siberia to the arctic ocean abstract a prominent lake formed when glaciers descending from the kodar range blocked the river vitim in central transbaikalia siberia glacial lake vitim evidenced by palaeoshorelines and deltas covered 23 500 km2 and held a volume of 3000 km3 we infer that a large canyon in the area of the postulated ice dam served as a spillway during an outburst flood that drained through the rivers vitim and lena into the arctic ocean the inferred outburst flood of a magnitude comparable to the largest known floods on earth possibly explains a freshwater spike at 13 cal ka bp inferred from arctic ocean sediments

late quaternary paleoenvironmental records from the western lena delta arctic siberia abstract the three main lena delta terraces were formed during different stages of the late quaternary while only the first floodplain terrace is connected with active deltaic processes the second and third terraces which dominate the western part of the delta are erosional remnants of arctic paleolandscapes affected by periglacial processes the landscape dynamics of the second and the third terraces and their relationship to each other are of particular importance in any effort to elucidate the late quaternary paleoenvironment of western beringia multidisciplinary studies of permafrost deposits on the second terrace were carried out at several sites of the arga complex named after the largest delta island arga muora sise the frozen sediments predominantly consist of fluvial sands several tens of meters thick radiocarbon dated from 52 to 16 kyr bp these sands were deposited under changing fluvial conditions in a dynamic system of shifting river channels and have been additionally modified by synsedimentary and postsedimentary cryogenesis later thermokarst processes affected this late pleistocene fluvial landscape during the lateglacial and the holocene in addition eolian activity reworked the fluvial sands on exposed surfaces at least since the lateglacial resulting in dune formation in some areas contrary to the arga complex the third terrace is mainly composed of polygenetic alluvial and proluvial ice rich permafrost sequences ice complex deposits radiocarbon dated from 50 to 17 kyr bp which cover older fluvial sand units luminescence dated to about 100 50 kyr bp paleoecological records reflect tundra steppe conditions that varied locally depending on landscape dynamics during the marine isotope stage mis 4 and 3 periods and a persistent change to shrub and arctic tundra during lateglacial and holocene periods the study results indicate a continuous fluvial sedimentation environment for the laptev sea shelf in the region of the second lena delta terrace during the late pleistocene and confirm the presence of a dynamic channel system of the paleo lena river that flowed at the same time as the nearby subaerial ice complex deposits were being formed

freshwater megaflood sedimentation what can we learn about generic processes abstract there is growing recognition that sedimentary deposits related to high energy large scale freshwater floods are widespread across the continents and in the main can be related to quaternary outbreak flows from ice dammed lakes such deposits may also occur in the neogene and earlier recognition of these megaflood deposits is hindered by the lack of well conditioned stratigraphic models of depositional successions however descriptions of successions from many locations often exhibit commonalities when compared carefully thus the primary purpose of this paper is to examine and condense the published stratigraphic and sedimentological evidence so as to identify the key signatures of megaflood successions the deposits often are the only record of a flood and so the secondary purpose is to interpret the sedimentary sequences in order to recreate the behaviour of floods through single and multiple events finally some pointers are provided as to those areas of sedimentological research that might be profitably explored in more depth to improve understanding of megaflood dynamics a key characteristic of megaflood deposits is the apparent massive appearance of single units which on closer inspection usually are amalgamated layers of similar grain size distribution individual beds and sets of beds are commonly near horizontal planar and laterally extensive successions evidently are not channelized and extensivity is indicative of simultaneous and coherent deposition over large areas localised large scale clinoforms or smaller scale cross beds are common associated with bar front or dune progradation respectively but otherwise extensivity implies that cross cutting erosional contacts notably steeply inclined examples and small scale scours are not common except immediately around large isolated clasts such as dropstones and ice blocks a common vertical stack of sequences in any one succession consists of 1 basal thick coarse parallel bedded units 2 large scale clinoforms 3 horizontally bedded thin laminated units 4 ripple and dune cross beds 5 silt beds and 6 succession capping debris flow deposits in some cases such a succession usually is indicative of a single cycle of waxing and waning flood flow generally dominated by high concentration suspension deposition onto plane beds the high power allows the transport of fine gravel and coarse sand in suspension leading upon deposition to relatively coarse beds from suspension fall out clay and silt is generally sparse or absent being transported further down the system at the scale of the hydrograph the successions indicate that flows initially accelerate and then decelerate with significant shorter period flow pulses also evident in the sedimentary signatures in parallel bedded sequences primarily during waxing flows bedload transport often was ineffective in sorting sediment due to the high rates of deposition from the highly sediment charged waters resulting in diffuse accretion surfaces at each location similar sequence stacks are common leading to the impression of rhythmic deposition from pulsing flow including from repetitive series of floods although often composed of coarse grains many sequence stacks excluding any debris flows are not dissimilar to turbidity flow sequences the bouma sequence in particular although there is limited experimental evidence for turbidity currents associated with high energy freshwater flows theory does not preclude the deposition of similar sedimentary motifs from high concentration flows such that an analogy between some megaflood sedimentary beds and turbidites is not unreasonable despite considerable variation in megaflood sedimentary successions commonalities occur which are indicative of similar processes of deposition from high energy floods at geographically different locations the changes in style of deposition throughout a succession provide clues as to the nature of the flood flows and this information could be used to improve estimates of flood hydrograph behaviour however hypotheses linking deposit characteristics to flow dynamics are currently ill conditioned and often poorly tested the majority of published studies describe the coarser scale stratigraphy with only passing reference to the fine scale structure of individual beds closer attention to lamination styles particle orientation and syn depositional deformation structures for example should provide information on the flow mechanics at the time of bed deposition thus better consideration of the sedimentology of megaflood deposit beds will lead to better understanding of the controlling hydraulics and should result in better models of flood deposition

meltwater routing and the younger dryas the younger dryas the last major cold episode on earth is generally considered to have been triggered by a meltwater flood into the north atlantic the prevailing hypothesis proposed by broecker et al 1989 nature 341 318 321 more than two decades ago suggests that an abrupt rerouting of lake agassiz overflow through the great lakes and st lawrence valley inhibited deep water formation in the subpolar north atlantic and weakened the strength of the atlantic meridional overturning circulation amoc more recently tarasov and peltier 2005 nature 435 662 665 showed that meltwater could have discharged into the arctic ocean via the mackenzie valley 4 000 km northwest of the st lawrence outlet here we use a sophisticated high resolution ocean sea ice model to study the delivery of meltwater from the two drainage outlets to the deep water formation regions in the north atlantic unlike the hypothesis of broecker et al freshwater from the st lawrence valley advects into the subtropical gyre 3 000 km south of the north atlantic deep water formation regions and weakens the amoc by 30 we conclude that meltwater discharge from the arctic rather than the st lawrence valley was more likely to have triggered the younger dryas cooling

small turbidite systems in a complex tectonic setting sw mediterranean sea morphology and growth patterns abstract three small turbidite systems almeria sacratif and guadiaro each tens of kilometres long are developed in the complex morpho structural setting of the northern alboran sea and have similar primary architectural elements canyons channel levee systems lobes however comparison reveals differences in the axial gradients of their canyons depth physiographic location morphological framework and lateral and longitudinal sedimentary shifts of turbidite deposition the depositional architecture and sedimentary evolution from late pliocene to quaternary seems to be conditioned by number of submarine feeding sources canyons sea level fluctuations and local tectonic e g margin canyon channel gradients faults we group the alboran turbidite systems into two models mud sand rich submarine point source and mud sand rich multiple submarine source ramp

effects of the quaternary sea level change on the subsidence of a sedimentary basin a case study of the osaka bay sedimentary basin japan abstract surface load redistribution related to the quaternary ice age may play an important role on the formation of quaternary sedimentary basin the basin is in fact formed by tectonic processes but the quaternary sea level change may effect the subsequent evolution of the basin in particular the subsidence history thus the time dependent surface load and its concomitant sediment loading produce a maximum crustal subsidence of about 100 m if the following conditions are satisfied 1 maxwell relaxation time of relatively thin lithosphere is less than the period of the glacial and interglacial cycle of 10 5 yr and 2 sediments are sufficiently supplied into the deformed areas by the water loading crustal subsidence of 100 m corresponds to about 20 for the depression of osaka bay basin during the past 1 2 myr these two conditions seem to be satisfied in active island arcs with relatively weak lithosphere and osaka bay sedimentary basin formed in the quaternary is a suitable place to test this mechanism and or to examine its effect on the crustal subsidence related to the sedimentary basin

structural evolution of the tyrrhenian back arc basin abstract the tyrrhenian basin has developed as a marginal basin through drifting of the calabrian sicilian arc system towards the east southeast the main structural features of the basin result from this movement the tensional structures normal faults of the margins are mainly aligned n10 to n30 e the transform faults are oriented n110 n120 e except for a previous structuralization linked to the western mediterranean rifting and drifting the first extensional movements affected the tyrrhenian area as early as lower miocene time during the post burdigalian nevertheless the main rifting phase which led to oceanic accretion was initiated during the late tortonian the narrow central oceanic area generated mainly around the early pliocene is restricted to the rift s axis the marginal basin type of evolution of the tyrrhenian sea is most probably directly linked to subduction of the ionian lithosphere nevertheless interferences between collision in the surrounding apennines calabria or sicilides and subduction processes have dominated this special back arc basin evolution since late tortonian time the tyrrhenian arc shows a regional n120 e oriented tensional pattern short compressional events occur briefly in middle pliocene and middle pleistocene times correlated with brief paroxysmal phases of extension and subsidence the deformation depends on the presence of a subduction zone parallel to the calabrian arc swell which allows the migration of the unblocked segments of the arc in a n120 e direction

a high resolution tephrochronological record of mis 14 12 in the southern apennines acerno basin italy abstract lithological mineralogical and glass chemical analyses on juvenile fragments extracted from 20 tephra layers embedded within the lacustrine sediments of the acerno basin southern apennines italy were carried out together with four sanidine 40 ar 39 ar age determinations the measured ages span the interval between 561 and 493 ka middle pleistocene eruptive activity at roman province volcanoes was identified as the main possible source of the investigated tephra layers some of them were correlated with precise terrestrial counterparts corresponding to large explosive events of the sabatini e g tufo giallo della via tiberina and alban hills volcanic districts e g tufo pisolitico di trigoria the integration of tephrochronology and pollen analyses allowed the acerno lacustrine sedimentation to be constrained between mis 14 and 12 which overlaps with several well studied lacustrine successions of the southern apennines the correlation with other tephrostratigraphic records from intramontane basins in central southern apennines testifies to the wide dispersal of at least three tephra layers that serve as marker layers thus improving the resolution of the middle pleistocene italian tephrostratotype

suborbital timescale variability of north atlantic deep water during the past 200 000 years we generated 200 kyr long proxy records of surface and deepwater variability from a subpolar north atlantic core v29 202 enabling us to assess the linkage between surface and deepwater changes on suborbital timescales in particular we used a benthic 13c record to evaluate the deep water response to dansgaard oeschger temperature oscillations and to heinrich events times of massive iceberg delivery to the north atlantic we found that the reduction of north atlantic deep water nadw production was generally associated with cold or dropping sea surface temperatures ssts as indicated by planktonic foraminiferal assemblages the nadw contribution to the site did not drop appreciably during heinrich events h4 through h2 probably because these events followed intervals of prolonged surface cooling already characterized by low rates of nadw production by contrast nadw reduction appears to have been synchronous with h5 sst rise associated with both dansgaard oeschger oscillations and heinrich events was usually accompanied by increasing nadw strength in a few cases the nadw recovery appeared to lag the sst rise however the apparent delay is most likely an artefact of the sedimentary record low concentrations of benthic foraminifera as a result of low benthic foraminiferal abundances during stage 6 the stage 6 benthic foraminiferal 13c record is of lower resolution than the younger part of the record the stage 6 proxy records for surface hydrography nevertheless reveal millennial scale oscillations similar to those seen in stage 3 the available 13c data suggest that nadw weakened in association with the cold portions of stage 6 sst oscillations we also sought to confirm a recent study which concluded that there was little nadw variability during the peak of the last interglaciation marine oxygen isotope substage 5e eemian isotope stage 5 was marked by a trend of increasing benthic 13c in v29 202 rising 13c through isotope stage 5 is also seen in tropical surface water records and at some deep atlantic sites and may reflect the common derivation of these water masses variations of 0 5 superimposed on this rising 13c trend within substage 5e in v29 202 are so far not evident in tropical feed waters and may therefore indicate that nadw production was weaker during the late than mid eemian an electronic supplement of this material may be obtained on a diskette or anonymous ftp from kosmos agu org login to agu s ftp account using anonymous as the username and guest as the password go to the right directory by typing cd apend type ls to see what files are available type get and the name of the file to get it finally type quit to leave the system paper 95pa02089 suborbital timescale variability of north atlantic deep water during the past 200 000 years by d w oppo and s j lehman diskette may be ordered from american geophysical union 2000 florida avenue n w washington dc 20009 15 00 payment must accompany order

routing of meltwater from the laurentide ice sheet during the younger dryas cold episode rooth1 proposed that the younger dryas cold episode which chilled the north atlantic region from 11 000 to 10 000 yr bp was initiated by a diversion of meltwater from the mississippi drainage to the st lawrence drainage system the link between these events is postulated to be a turnoff during the younger dryas cold episode of the north atlantic s conveyor belt circulation system which currently supplies an enormous amount of heat to the atmosphere over the north atlantic region2 this turnoff is attributed to a reduction in surface water salinity and hence also in density of the waters in the region where north atlantic deep water nadw now forms here we present oxygen isotope and accelerator radiocarbon measurements on planktonic foraminifera from orca basin core en32 pc4 which reveal a significant reduction in meltwater flow through the mississippi river to the gulf of mexico from about 11 200 to 10 000 radiocarbon years ago this finding is consistent with the record for lake agassiz which indicates that the meltwater from the southwestern margin of the laurentide ice sheet was diverted to the northern atlantic ocean through the st lawrence valley during the interval from 11 000 to 10 000 years before present yr bp

the evolution of the calabrian arc evidence from paleomagnetic and gps observations abstract the present day arcuate shape of the calabrian arc has been accomplished during neogene and early pleistocene by large and opposite vertical axis rotations along the two arms of the arc clockwise cw rotations have been systematically registered in sicily and calabria whereas counterclockwise ccw rotations were measured in southern apennines such opposite vertical axis rotations ceased in the uppermost part of the lower pleistocene about 1 ma ago along almost the entire calabrian arc and are not observed in the present day gps velocity field the end of the calabrian arc bending during the quaternary marks a decrease in the efficiency of the tectonic processes related to the long lived subduction of the ionian slab which caused the halting of the back arc opening in the southern tyrrhenian sea

structural and sedimentary features in the tyrrhenian margin off campania southern italy abstract the utilization of multichannel seismic reflection profiles permits the identification of the generally e w trending miocene orogenic and plio quaternary post orogenic features of apennine nw se and anti apennine ne sw trends in the campanian margin the former features are constituted by carbonate and or allochthonous sheets which were thrust mainly towards the north and northeast during the miocene tectogenetic phases the latter are represented by extensional structures which affected the orogenic features during plio quaternary times the anti apennine tectonic trend is responsible for the recent late pliocene quaternary and remarkable block faulting differential subsidence of the southern margin as well as for its present morphology the ragged and disconnected pattern of the allochthonous units over the present day slope and their accumulation underneath the shelf area suggest that they are the result of gravitational gliding tectonics gravity cores and 3 5 khz subbottom profiles indicate that the salerno trough and capri basin areas are characterized by a particular neotectonic mobility this is proved by the thick and coarse grained sediment accumulation from steep relief produced by block faulting this faulting created uplift belts serving as sediment source

reconstruction of paleoceanography off nw africa during the last 40 000 years influence of local and regional factors on sediment accumulation abstract a set of 43 sediment cores from around the canary islands is used to characterise this region which intersects meridional climatic regimes and zonal productivity gradients in a high spatial resolution using rapid and nondestructive core logging techniques we carried out fe intensity and magnetic susceptibility ms measurements and created a stack on the basis of five stratigraphic reference cores for which a stratigraphic age model was available from 18 o and 14 c analyses on planktonic foraminifera by correlation of the stack with the fe and ms records of the other cores we were able to develop age depth models at all investigated sites of the region we present the bulk sediment accumulation rates ar of the canary islands region as an indicator of shifts in the upwelling influenced areas for the holocene 0 12 ky the deglaciation 12 18 ky and the last glacial 18 40 ky general observations are an enhanced productivity during glacial times with highest values during the deglaciation the main differences between the analysed time intervals we interpret as result of the sea level effects changes in the extent of high productivity areas and current intensity

evolution of the late quaternary san gregorio magno tectono karstic basin southern italy inferred from geomorphological tephrostratigraphical and palaeoecological analyses tectonic implications the pantano di san gregorio magno is a 4 7 km 2 large tectono karstic basin located in the axial belt of the southern apennines an area affected by intense seismicity the basin was formed in the middle pleistocene and is presently undissected it is filled by lacustrine sediments clays silts and pyroclastic sands passing laterally into alluvial fan deposits geomorphological investigations were integrated with tephrostratigraphical palynological and palaeoecological analyses of a 61 m thick core not reaching the bedrock the multiproxy analysis of the s gregorio magno record shows that over the last 200k yr the basin hosted a freshwater lake with an oscillating level age constraints provided by the tephrostratigraphic record allowed estimation of the sedimentation rate which varied strongly through time evolution of the basin resulted from the complex combination of tectonic subsidence karst processes and changing amounts of sedimentary inputs the latter was influenced by allogenic contributions related both to primary and reworked volcanoclastic inputs and was climate driven the overall evidence which indicates that in the long term the accumulation rate substantially counterbalanced the accommodation space created by faulting suggests that the basin evolution was also modulated by changing subsidence rates copyright 2006 john wiley sons ltd

a review of the milankovitch climatic beat template for plio pleistocene sea level changes and sequence stratigraphy the milankovitch theory of climate change predicts that global ice volume and hence sea level changes were controlled by long term quasi periodic variations in the earth s orbital parameters obliquity precession and eccentricity d 18 o records from deep sea cores are a proxy for sea level changes and have an orbitally tuned chronology covering the last 5 ma the sea level signal in d 18 o data from east equatorial pacific core v19 30 is well calibrated with sea level data from coral terraces on huon peninsula new guinea over the last 140 ka and with less certainty back to 340 ka over the last 140 ka the sea level contribution to benthic glacial interglacial isotopic variation is about 1 2 1 3 or 0 011 m 1 and for core v19 30 the glacial age temperature contribution from deep ocean cooling of 1 7oc is 0 4 independent constraints on late pliocene sea level changes interpreted from shallow marine continental margin records indicate that the sea level d 18 o calibration may not have been the same over the last 2 6 ma and the temperature correction is unlikely to have been the same in all glacial periods and all ocean settings nevertheless the astronomically tuned isotopic records from deep sea cores provide an accurate chronology and approximate the magnitudes of sea level changes over the last 2 6 ma against which the facies architecture of stratigraphic sequences can be analysed and the concepts of sequence stratigraphy properly evaluated 1998 elsevier science b v all rights reserved

late tertiary quaternary tectonics of the southern apennines italy new evidences from the tyrrhenian slope this paper summarises the results of combined structural and geomorphological investigations we carried out in two key areas in order to obtain new data on the structure and evolution of the tyrrhenian slope of the southern apennines analysis by a stress inversion method angelier j 1994 fault slip analysis and paleostress reconstruction in continental deformation p l hancock ed pergamon press oxford 53 100 of fault slip data from mesozoic to quaternary formations allowed the reconstruction of states of stress at different time intervals by integrating these data with those deriving from the stratigraphic and morphotectonic records chronology and timing of the sequence of the deformation events was obtained the tectonic history of the region can be related to four deformation events structures related to the first event that was dominated by a strike slip regime with a nw se oriented 1 and was active since mid late miocene do not significantly affect the present day landscape as they were strongly displaced and overprinted by subsequent deformation events and or deleted by erosion the second and third events that may be considered as the main responsible for the morphostructural signature of the region are comparable with the stretching phases recognised offshore and considered to be responsible for the opening and widening of the tyrrhenian basin in particular the second event with an e w oriented 3 took place in the late miocene earliest pliocene and was first dominated by a strike slip regime that was also responsible for thrusting and folding since late pliocene it was dominated by an extensional regime that created large vertical offsets along n s to nw se trending faults the third event that was dominated by extension with a nw se oriented 3 started in the early pleistocene and was responsible for formation of the horst and graben structure with ne sw trend that characterises the tyrrhenian margin of the southern apennines the fourth deformation event which is characterised by an extensional regime with a ne sw trending 3 started in the late middle pleistocene and is currently active

tectonic evolution of arcuate mountain belts on top of a retreating subduction slab the example of the calabrian arc 1 in this paper new paleomagnetic results from the calabrian arc are presented together with a critical review of all paleomagnetic data collected in the last decades in southern italy our study is focused on the upper miocene to middle pleistocene deposits of the crati extensional basin a sector of the arc where an abrupt change in the sense of paleomagnetic rotations is observed paleomagnetic data indicate that the crati basin underwent a uniform clockwise cw rotation of about 15 20 in its central and southern part whereas the northern sector is organized in small scale fault bounded blocks which rotated independently we interpret this pattern of deformation as the evidence of the complex nature of this area which represents the boundary between two domains characterized by opposite rotations the southern apennines which rotated counterclockwise and the calabria and sicily which rotated cw integrating these new paleomagnetic data with paleomagnetic data from southern italy we reconstruct the history of paleomagnetic rotations through time paleomagnetic rotations highlight the peculiarity of the formation of the calabrian arc curvature and imply that either an oroclinal bending model or a progressive arc model cannot be simply applied to the calabrian arc formation we describe a realistic tectonic geodynamic model where the progressive curvature of the calabrian arc is framed within the space time evolution of the ionian subduction system

quaternary paleolake formation and cataclysmic flooding along the upper yenisei river abstract a suite of geomorphological and sedimentological features in the catchment of the upper yenisei river in the sayan mountains of southern siberia testifies to the occurrence of cataclysmic floods that flowed down the river evidence of large scale high energy flood events includes 1 gravel dunes up to a few meters high and spaced 50 to 80 m apart in the kyzyl basin 2 landforms such as hanging valleys and paleochannels and 3 flood sediments in a tributary valley the origins of the yenisei floods were likely diverse due to complex hydrological processes operating in the sayan mountains the possibilities include failures of multiple variably impounded ice sedimentary tectonic scarp and lava flow dams paleolakes in the two large intermontane basins of darkhadyn khotgor and todza and other minor basins in the upper yenisei river catchment dating techniques applied to the paleolakes in the darkhadyn khotgor and todza basins revealed their formation during various periods in the middle late pleistocene and holocene flooding from the darkhadyn khotgor appears to explain many of the inferred flood features although contributions by flooding from other paleolake basins cannot be ruled out computer simulation of the flooding caused by a darkhadyn khotgor paleolake ice dam failure indicates a probable peak discharge of 3 5 10 6 m 3 s 1 approximately one fifth that of the floods that formed the channeled scabland in the u s a many of the outburst events probably occurred in the late quaternary but earlier floods could also have occurred

extensional detachment faulting on the tyrrhenian margin of the southern apennines contractional belt italy the tectonic evolution of the campania margin during the late pliocene pleistocene is characterized by extensional deformation coeval with the opening of the marsili oceanic basin the initial stages of stretching are represented in the analysed area by the development of low angle normal faults that extended the belt in the same direction as the direction of spreading recognized for the oceanic basin detachment faulting was accompanied by the onset of magmatic activity and by major uplifts that resulted in the accumulation of thick conglomerate successions in the half grabens that developed in the upper plate of the extensional detachment deformation continued during the mid pleistocene with the formation of strike slip and normal faults trending almost parallel to the spreading direction of the marsili basin these faults dissected the extensional detachment and promoted counter clockwise block rotations about vertical axes which accommodated the ese directed stretching of the marsili basin and the consequent sinistral shear imposed on the southern apennine chain the development of a regional detachment fault along the tyrrhenian margin of campania explains the complex patterns of subsidence and uplift that characterize this area during the pleistocene and fits well within the regional geodynamic framework of the southern tyrrhenian sea

acoustical characterization of sediments by parasound and 3 5 khz systems related sedimentary processes on the southeastern weddell sea continental slope antarctica subbottom profiling was performed during four polarstern expeditions to the southeastern weddell sea continental slope northwest of lyddan ice rise antarctica analogue records from high resolution seismic reflection systems 3 5 khz and parasound were used to classify sediment echo types a comparison between the two systems shows the advantage of the parasound system the smaller beam angle produces a higher spatial resolution which reduces the diffraction hyperbolae considerably the higher vertical resolution and deeper penetration provide more detailed information concerning seismic stratification using four basic echo categories p prolonged l layered d diffraction hyperbolae w wedging subbottoms ten discrete sediment echo patterns were distinguished their regional distribution and the depth of acoustic signal penetration into the sediment were mapped sw ne trending sediment ridges with channels running parallel on the southeastern side of the ridges were traced in the eastern part of the study area the prolonged and highly reflective echo types of the channel bottoms indicate deposition of predominantly coarse grained sediments affected by erosional processes these channels are interpreted as drainage systems for bottom water currents derived from the shelf and steep upper slope the flow direction is towards the northeast counter to the weddell gyre in contrast the sediment ridges show up to 80 m subbottom penetration and an echo type of distinct multi layered reflectors running parallel to subparallel with the surface reflector the sediments of the ridges are interpreted to be levee sediments overspilled from the channels and preferentially deposited on the northwestern flank due to the coriolis force sedimentary units separated by wedge shaped reflectors are widespread on the gently inclined terrace in the middle part of the continental slope these sediments are presumed to be produced by syn sedimentary slumping and proximal debris flows having a northeastern direction of movement

bioturbation into a recently emplaced deep sea turbidite surface as revealed by210pbexcess 230thexcess and planktonic foraminifera distributions abstract this study concerns the surface of a single distal turbidite emplaced on the madeira abyssal plain a few hundred years ago the vertical and horizontal homogeneity of the unit and the low pelagic sediment accumulation rate enable a ready identification of the post emplacement signals of near surface bioturbation data have been gathered to define 210 pb excess 230 th excess and pelagic foraminifera profiles with depth these are used as constant input flux tracers and treated by models conventionally used to determine bioturbation parameters the mixed layer depths 7 11 cm bioturbation coefficients 0 08 0 18 cm 2 y 1 and inventory data 10 23 dpm cm 2 derived from the 210 pb excess data in five out of six cores are similar to those previously observed elsewhere with the same model in the deep sea under steady state sediment accumulation conditions although the mixed layer depths are similar for all three tracers the 210 pb excess bioturbation intensities are larger by a factor of 3 than those estimated from 230 th excess profiles and about an order of magnitude larger than those from the foraminifera profiles it is suggested that the conventional 210 pb excess model and those for other short lived tracers probably over estimate the intensity of biomixing of foraminifera for palaeontological and related geochemical purposes

late quaternary megafloods from glacial lake atna southcentral alaska u s a abstract geomorphic stratigraphic geotechnical and biogeographic evidence indicate that failure of a pleistocene ice dam between 15 5 and 26 ka generated a megaflood from glacial lake atna down the matanuska valley while it has long been recognized that lake atna occupied 9000 km2 of south central alaska s copper river basin little attention has focused on the lake s discharge locations and behaviors digital elevation model and geomorphic analyses suggest that progressive lowering of the lake level by decanting over spillways exposed during glacial retreat led to sequential discharges down the matanuska susitna tok and copper river valleys lake atna s size 50 ka duration and sequential connection to four major drainages likely made it a regionally important late pleistocene freshwater refugium we estimate a catastrophic matanuska megaflood would have released 500 1400 km3 at a maximum rate of 3 106 m3 s 1 volumes for the other outlets ranged from 200 to 2600 km3 and estimated maximum discharges ranged from 0 8 to 11 3 106 m3 s 1 making lake atna a serial generator of some of the largest known freshwater megafloods

constraining the timing of the most recent cataclysmic flood event from ice dammed lakes in the russian altai mountains siberia using cosmogenic in situ 10be ice dammed lakes were repeatedly formed in intermontane basins in the russian altai mountains throughout the pleistocene these cataclysmic outburst floods caused by ice dam failures were documented as earth9s largest flood waves by other geoscientists using in situ 10 be we successfully dated surfaces of flood associated boulders located in a former lake basin and downvalley from a former ice dam our precise surface exposure ages suggest that all boulders were associated with the most recent out of a number of cataclysmic floods that occurred at 15 8 1 8 ka the field location of the boulders implies that they were deposited by the largest late pleistocene flood that drained the chuya katun lake completely following initial dam failure a published reconstruction of the late glacial paleoenvironment in the vicinity of the former ice dam indicates that dam failure was likely a result of climatically induced downwasting of glaciers the failure of the ice dam provides more evidence for the timing of widespread warming during the late glacial in southern russia this flooding event in the headwaters of the ob river coincides with a freshwater peak as recorded in isotopic records of the kara sea and the arctic ocean

quaternary uplift vs tectonic loading a case study from the lucanian apennine southern italy abstract uplift rates have been calculated for a large sector of the lucanian apennine axial zone of the southern apennines italy using both geomorphological observations elevation values ages and arrangement of depositional and erosional landsurfaces and other morpho tectonic indicators and stratigraphical and structural data sea level related facies fault kinematics and offset estimations these data have been compared with those derived from clay mineralogy of mesozoic pelagic successions lagonegro units outcropping in the same sector of the chain which gave information on tectonic loading the values of the quaternary uplift rates of the southern apennines axial zone vary from a minimum of 0 2 mm yr to a maximum of about 1 2 mm yr intermediate values 0 5 0 7 mm yr have been calculated for the other studied areas using geomorphological features and late pliocene to pleistocene successions involved in the genesis of erosional and depositional landsurfaces the same rates 0 6 mm yr have been obtained for a large time span about 2 ma in the melandro basin and adjacent maddalena mts therefore during the last 2 ma the total uplift amount of the axial zone of the lucanian apennine is about 1 2 1 3 km with local peaks of 1 5 km on the other hand the mesozoic pelagic units experienced a tectonic loading of 4 5 km as estimated by means of illite crystallinity in the range 0 6 1 1 2 percentage of illitic layers in illite smectite mixed layers 60 90 and white mica polytypes in the range of 10 35 the quaternary uplift and the related erosion rates of the southern apennines are unquestionably due to strike slip faulting and above all due to extensional tectonics coupled with thermal isostatic regional raising the gap of several kilometres derived from the comparison between uplift rates and tectonic loading values may be explained only by different exhumation modalities starting from late miocene time

vertical movements on the eastern margin of the tyrrhenian extensional basin new data from mt bulgheria southern apennines italy abstract in this paper we present the results of an integrated stratigraphical geomorphological and morphotectonic study carried out in mt bulgheria a rocky headland located on the eastern margin of the tyrrhenian extensional basin in southern italy such a margin is characterised by the occurrence of uplifted headlands alternated with subsiding half grabens in particular mt bulgheria constitutes the northeastern margin of the gulf of policastro peri tyrrhenian depression in the study area pliocene quaternary continental deposits and erosional landforms are present together with pleistocene wave cut and wave built marine terraces the integrated study of pliocene pleistocene deposits and landforms allowed a detailed reconstruction of the geomorphological evolution of mt bulgheria to be made furthermore the tectonic behaviour of this portion of the tyrrhenian margin during plio quaternary times could be characterised in particular we recognised that a succession of alternated uplift and subsidence episodes affected the headland since the beginning of early pleistocene when the eastward migrating coastline of the tyrrhenian extensional basin reached mt bulgheria the alternated uplift and subsidence events lasted for early and middle pleistocene their cessation in late pleistocene is demonstrated by the occurrence of late pleistocene strandlines at an elevation comparable with that of the 130 ka sea level highstand as recorded in stable areas of the mediterranean region the occurrence of marine terraces allowed the absolute vertical movements to be estimated their summation produced an uplift of the headland of 400 m since the beginning of the santernian 150 m of which occurred in the middle pleistocene along the onshore belt of the tyrrhenian margin of southern apennines other structural highs bordering the peri tyrrhenian depressions provide evidence for subsidence episodes interrupting the prevailing uplift trend recorded during the quaternary this together with the distribution of quaternary marine deposits both downthrown and raised and terraces shows that the tyrrhenian margin of southern apennines was affected by strongly variable vertical movements

arctic ocean deep sea record of northern eurasian ice sheet history the sediment composition of deep sea cores from the central arctic ocean the fram strait and the yermak plateau was analyzed for several parameters to reconstruct the history of marine paleoenvironment and terrestrial glaciation in the last 200 000 years layers with high amounts of coarse terrigenous ice rafted debris ird and often high contents of smectite were deposited during extensive glaciations in northern eurasia when ice sheets reached the northern continental margins of the barents and kara seas and discharged icebergs into the arctic ocean intercalated layers with relatively low ird and smectite contents but abundant planktic foraminifers in the coarse fraction were deposited during periods of atlantic water inflow to the arctic ocean and seasonally open waters leads in a sea ice cover with only few icebergs in the arctic ocean high ird contents in the sediments reflect the presence of ice sheets on the kara and barents seas shelves and the hinterland during the entire oxygen isotope stage 6 ca 190 130 ka in substage 5b ca 90 80 ka at the stage boundary 5 4 around 75 ka and in late stage 4 early stage 3 ca 65 50 ka these results are in excellent correlation with those from recent field work in northern scandinavia european russia siberia and on the shelves relatively low amounts of ird in central arctic ocean sediments from the late weichselian glacial maximum ca 24 18 ka correlate well with the recent reconstruction of a very limited eastern ice sheet extension during this time oxygen and carbon isotope records of planktic foraminifers from the analyzed sediment cores show a number of prominent excursions which can be interpreted as evidence for freshwater events in the arctic ocean the synchroneity of freshwater events and ird input suggests a common source strongest events were associated with deglaciations of the barents and kara seas after the ice sheets had blocked the outflow of large rivers for several millennia the outflow of freshwater from large ice dammed lakes occurred at ca 130 80 75 and 52 ka freshwater events in the central arctic ocean during the last deglaciation ca 18 ka were relatively small compared to the previous events this indicates that during most of the late weichselian glacial maximum a river outflow from northern siberia to the arctic ocean was possible atlantic water inflow to the arctic ocean and seasonally open waters in the ice leads occurred during the interglacials ofoxygen isotope stage 1 and substage 5e during several interstadials stage 3 substages 5a and 5c and to a lesser degree within stadials and glacials stages 2 4 and 6 with the exception ofthe interglacials these periods were times ofstrong ice growth on the continents as revealed by terrestrial data the coincidence suggests that open waters in the arctic ocean and the nordic seas were an important moisture source in addition to more southerly sources which fostered the growth of ice sheets on northern eurasia

a multiproxy approach to reconstruct the environmental changes along the eurasian continental margin over the last 150 000 years abstract sediment cores located along the eurasian continental margin arctic ocean have been studied to reconstruct the environmental changes in terms of waxing and waning of the barents kara sea ice sheets atlantic water inflow and sea ice distribution over the last 150 kyr the stratigraphy of the cores is based on stable oxygen isotopes ams 14 c and paleomagnetic data we studied variations in marine and terrigenous input by a multiproxy approach involving direct comparison of sedimentological and organo geochemical data extensive episodes of northern barents sea ice sheet growth during marine isotope stages mis 6 and 2 have been supported by at least subsurface atlantic water inflow moisture bearing storms low summer insolation and minimal calving of ice ice advance during mis 4 was probably restricted to the shallow shelf between mis 4 and mis 2 large ice sheet fluctuations correspond to contemporary laurentide surging events and indicate short term climatic changes in the arctic ocean as has been recorded in lower latitudes in contrast in low precipitation areas in eastern eurasia glacial activity was rather limited only distinct ice rafted debris ird input during termination ii and early mis 3 reflects severe glaciations on the northern severnaya semlya margin during mis 6 and mis 4 we conclude that 1 oscillations of ice sheets are less frequent along the eastern eurasian margin than in areas with continuous moisture supply like the western eurasian margins and that 2 major fluctuations of the kara sea ice sheet during the last 150 kyr apparently followed the major interglacial glacial mis 5 4 and mis 7 6 transitions rather than the precession 23 kyr and the tilt 41 kyr cyclicity of the earth s orbit as observed for the scandinavian sis and the svalbard ice sheets respectively mangerud j jansen e landvik j y 1996 late cenozoic history of the scandinavian and barents sea ice sheets in solheim a riis f elverhoi a faleide j j jensen l n cloetingh s eds impact of glaciations on basin evolution data and models from the norwegian margins and adjacent basins global and planetary chance special issue 12 pp 11 26 surface and or subsurface atlantic water masses coupled with seasonally ice free conditions penetrated continuously to at least the franz victoria trough during the last 150 kyr however sustained periods of open water were largely restricted to substages 5 5 5 1 and the holocene as indicated by distinct carbonate dissolution and higher accumulation of marine organic matter mom signals of periodic open water conditions along the northern margin of severnaya semlya are of less importance higher production of foraminifera probably due to atlantic water inflow occurred between 38 and 12 14 c kyr and corresponds to periodic atlantic water advection penetrating into the arctic ocean however marine organic proxies indicate a continuous decrease of surface water productivity from the western to the eastern eurasian continental margin due to a more extensive sea ice cover over the last 150 kyr

paleohydrology of late pleistocene superflooding altay mountains siberia cataclysmic flooding is a geomorphological process of planetary significance landforms of flood origin resulted from late pleistocene ice dammed lake failures in the altay mountains of south central siberia peak paleoflows which exceeded 18 x 10 6 cubic meters per second are comparable to the largest known terrestrial discharges of freshwater and show a hydrological scaling relation to floods generated by catastrophic dam failures these seem to have been earth9s greatest floods based on a variety of reconstructed paleohydraulic parameters

origin sedimentary processes and depositional evolution of the agadir turbidite system central eastern atlantic the oligocene to recent agadir turbidite system occurs in the agadir basin abutting against the continental margin off south morocco central eastern atlantic this system is part of the submarine drainage system linking back to the anti and high atlas mountains through the agadir canyon and its sedimentary evolution is shown to comprise lateral shifts of canyon channel overbank and lobe deposits governed by local topography draped palaeorelief seamounts and a contourite ridge and channel avulsions in addition the turbidite system shows an overall retrogradational stacking migrating about 60 km upslope this probably reflects a decrease in gradient on the continental margin gradual basin filling and or a progressive decrease in energy and load of the sediment gravity flows that fed the system the latter change in sediment flux could result from the interplay between the progressive denudation of the source areas together with the climatic change which led to the present arid desertic conditions in the hinterland the seismic features observed with new ultra high resolution seismic tools allow the recognition of the present day sedimentary activity within the agadir turbidite system and this is related among other factors to the active seismicity of the area

palaeoenvironmental dynamics inferred from late quaternary permafrost deposits on kurungnakh island lena delta northeast siberia russia abstract late quaternary palaeoenvironments of the siberian arctic were reconstructed by combining data from several fossil bioindicators pollen plant macro fossils ostracods insects and mammal bones with sedimentological and cryolithological data from permafrost deposits the record mirrors the environmental history of beringia and covers glacial interglacial and stadial interstadial climate variations with a focus on the middle weichselian interstadial 50 32 kyr bp the late pleistocene to holocene sequence on kurungnakh island reflects the development of periglacial landscapes under changing sedimentation regimes which were meandering fluvial during the early weichselian colluvial or proluvial on gently inclined plaines during the middle and late weichselian and thermokarst affected during the holocene palaeoecological records indicate the existence of tundra steppe vegetation under cold continental climate conditions during the middle weichselian interstadial due to sedimentation gaps in the sequence between 32 and 17 kyr bp and 17 and 8 kyr bp the late weichselian stadial is incompletely represented in the studied outcrops nevertheless by several palaeoecological indications arctic tundra steppe vegetation under extremely cold arid conditions prevailed during the late pleistocene the tundra steppe disappeared completely due to lasting paludification during the holocene initially subarctic shrub tundra formed which later retreated in course of the late holocene cooling

instability of the atlantic overturning circulation during marine isotope stage 3 variations in the strength of the atlantic meridional overturning circulation amoc were involved in the occurrences of dansgaard oeschger d o events during marine isotope stage 3 mis3 the stability of the amoc to north atlantic freshwater perturbations is studied using a comprehensive climate model under mis3 boundary conditions an amoc stability diagram constructed from a series of equilibrium freshwater perturbation experiments reveals a highly nonlinear dependence of amoc strength on freshwater forcing the mis3 baseline state is remarkably unstable with respect to minor perturbations the global climate signal associated with a change in amoc strength is consistent with a transition from an interstadial to a stadial state including an annual mean surface air temperature drop of 8 k in central greenland we suggest that minor freshwater perturbations in the hydrologic cycle e g related to ice sheet processes had the potential to trigger d o type climate shifts associated with a threshold in the atmosphere ocean system

fluvial geomorphology and neotectonic activity based on field and gpr data katrol hill range kachchh western india abstract the largely rocky and rugged landscape of the katrol hill range composed of mesozoic rocks and structurally controlled occurrences of quaternary sediments is delimited to the north by north facing range front scarps of the seismically active e w trending katrol hill fault khf the landscape and drainage characteristics of the katrol hill range are documented together with ground penetrating radar gpr investigations along the khf to delineate its nature for understanding neotectonic activity in the contemporary tectonic setting the overall geomorphology is controlled by the south oriented tilt block structure of the range indicated by its pronounced influence on the morphology and drainage network the drainage comprises north flowing and south flowing rivers with the drainage divide located close to the northern edge of the range which also marks the highest topographic elevations the narrow zone between the crest line and the drainage divide has been identified as the zone of gorges where gorges and deeply incised fluvial valleys have been formed within quaternary sediments by the various north flowing streams the quaternary sediments consist of bouldery colluvial deposits in front of the range front scarps valley fill miliolites and alluvial deposits of late pleistocene age within the back valleys and scarp derived colluvium forming the youngest deposit based on the geomorphic and stratigraphic evidence three major phases of quaternary tectonic uplift in the katrol hill range are inferred the oldest pre miliolite phase middle pleistocene was followed by a prominent phase of fluvial incision with formation of gorges during early holocene and then by the last one during late holocene continuing at present uplift of the range occurred in well marked phases during the quaternary in response to differential uplift along the khf under an overall compressive stress regime gpr investigations at selected sites show that the khf is a steep south dipping reverse fault near the surface which becomes vertical at depth this suggests neotectonic reactivation of the khf under a compressive stress regime responsible for active southward tilting of the katrol hill range

the northwest african slope apron a modern analogue for deep water systems with complex seafloor topography the northwest african slope apron is an interesting modern analogue for deep water systems with complex seafloor topography a sediment process map of the northwest african continental margin illustrates the relative roles of different sedimentary processes acting across the entire margin fine grained pelagic and hemipelagic sedimentation is dominant across a large area of the margin and is considered to result from background sedimentary processes alongslope bottom currents smooth and mould the seafloor sediments and produce bedforms such as erosional furrows sediment waves and contourite drifts downslope gravity flows debris avalanches debris flows and turbidity currents are infrequent but important events on the margin and are the dominant processes shaping the morphology of the slope and rise the overall distribution of sedimentary facies and morphological elements on the northwest african margin is characteristic of a fine grained clastic slope apron however the presence of numerous volcanic islands and seamounts along the margin leads to a more complex distribution of sedimentary facies than is accounted for by slope apron models in particular the distribution and thickness of turbidite sands are controlled by the location of the break of slope which is itself controlled by the pre existing submarine topography

deformation of the 125 ka marine terrace in italy tectonic implications in peninsular italy marine terraces and shorelines created during oxygenisotope substage 5e known historically as the tyrrhenian highstand provide a reliable and homogeneous datum of vertical motions during the past 125 000 years published accounts of 121 locations on the tyrrhenian inner edge were reinterpreted and used to calculate both local and regional uplift rates the data show arching of southern italy between the tyrrhenian and the adriatic coasts and of the calabrian arc between the sangineto and the longi taormina tectonic lineaments at rates of up to 1 2 mm yr for the past 125 ka they also suggest that the present configuration of the southern apennines is the product of post early pleistocene regional uplift superimposed on tortonian to early pleistocene thrusting uplift patterns are characterised by different wavelength in different geodynamic settings suggesting a close link with the depth of the causative tectonic sources

terrigenous sedimentation processes along the continental margin off nw africa implications from grain size analysis of seabed sediments the terrigenous fraction of seabed sediments recovered along the north west african continental margin illustrates spatial variability in grain size attributed to different transport mechanisms three subpopulations are determined from the grain size analyses n 78 of the carbonate free silt fraction applying an end member modelling algorithm g j weltje 1997 the two coarsest endmembers are interpreted as representing aeolian dust and the fine grained end member is related to fluvial supply the end member model thus allows aeolian fallout to be distinguished from fluvial sourced mud in this area the relative contributions of the end members show distinct regional variations that can be related to different transport processes and pathways understanding present day sediment dispersal and mixing is important for a better understanding of older sedimentary records and palaeoclimate reconstructions in the region

repeated megafloods from glacial lake vitim siberia to the arctic ocean over the past 60 000 years abstract cataclysmic outburst floods transformed landscapes and caused abrupt climate change during the last deglaciation whether such events have also characterized previous deglaciations is not known arctic marine cores hint at megafloods prior to oxygen isotope stage ois 2 but the overprint of successive glaciations means that geomorphological traces of ancient floods remain scarce in eurasia and north america here we present the first well constrained terrestrial megaflood record to be linked with arctic archives based on cosmogenic nuclide exposure dating and optically stimulated luminescence dating applied to glacial lake sediments a 300 m deep bedrock spillway and giant eddy bars 200 m high we reconstruct a history of cataclysmic outburst floods from glacial lake vitim siberia to the arctic ocean over the past 60 000 years three megafloods have reflected the rhythm of eurasian glaciations leaving traces that stretch more than 3500 km to the lena delta the first flood was coincident with deglaciation from ois 4 and the largest meltwater spike in arctic marine cores within the past 100 000 years isotope event 3 31 at 55 5 ka the second flood marked the lead up to the local last glacial maximum and the third flood occurred during the last deglaciation this final 3000 km3 megaflood stands as one of the largest freshwater floods ever documented with peak discharge of 4 0 6 5 million m3s 1 mean flow depths of 120 150 m and average flow velocities up to 21 m s 1

paleogeography and quaternary terrace sediments and complexes intermontane basins of prebaikalia southeastern siberia russia abstract several large lake stages interspersed by cycles with low water levels and exposed areas with erosion are recorded in prebaikalia depressions from the upper eopleistocene neotectonic activities were responsible for water level changes and ingression of lake waters into river valleys at the end of the eopleistocene the lake regime was transformed and finally replaced by a river two blocks of different elevation associated with sediment aggregates of the upper vii iv and low iii i terraces can be distinguished in the terrace complex the upper terraces were formed in a limnic environment and the lower terraces formed in a prevailing river environment with subordinate lacustrine conditions

geomorphology and tectonics of uplifted coasts new chronostratigraphical constraints for the quaternary evolution of tyrrhenian north calabria southern italy abstract the tyrrhenian coastal sector of north calabria stretching between torre s nicola and the lao river belongs to the inner extensional sector of the neogene apennines thrust belt it is characterised by a stair of quaternary marine and fluvial terraces representing the geomorphic response to the interaction between the quaternary sea level fluctuations and the regional trend of tectonic uplift experienced by the margins of the tyrrhenian back arc basin since the last century several authors studied the north calabria coasts where the flight of terraces preserves significant marine and continental successions and proposed several paleo geomorphological and tectonic reconstructions in this paper we present a new stratigraphic and morphostructural setting of the north calabria coasts based on both chronostratigraphical constraints obtained from marine deposits and detailed geomorphological analysis a ten order stair of marine terraces stepping between 240 and 0 m a s l was recognized and time constrained by the age of the fornaci s nicola marine succession which was ascribed by integrated paleoecological biostratigraphical and paleomagentic analyses to the early middle pleistocene mis 19 15 in particular the 240 200 and 160 m a s l high strandlines were ascribed to the early pleistocene and the ones between 100 and 15 m a s l to the middle pleistocene the total amount of the vertical motion experienced by the studied area was estimated and evaluation of the average rates of uplift for the middle and late pleistocene times were also given considering the elevation a s l of the oldest terraces a tectonic uplift of at least 240 m was calculated for the north calabria coasts since the early pleistocene times 100 m of which gained from the beginning of the middle pleistocene on the other hand the 8 m high late pleistocene strandlines display a negligible vertical displacement affecting the area during the last 130 ka the entire staircase of terraces preserves a record of slowing down in the rate of uplift which attained an average value of 0 15 mm year during the middle pleistocene

the plio quaternary uplift of the apennine chain new data from the analysis of topography and river valleys in central italy abstract this study aims at the reconstruction of magnitude and timing of surface uplift affecting a wide sector of the central apennines italy by means of morphometric and morphostructural analyses in the chain interiors where stratigraphic and geomorphological markers of past sea level positions are lacking the study is based on analysis of erosional landforms and river valleys a large scale topographic analysis by processing 90 m and 230 m dems is performed the spatial distribution of several morphometric parameters together with characteristic wavelengths of relief allowed the differentiation of three main regions affected by different cumulative surface uplift and tectonic erosional fragmentation a peri tyrrhenian belt an axial belt and a peri adriatic belt particular attention is devoted to fluvial landforms with analysis of longitudinal profiles and geometric pattern of the main drainage lines and their relations with the major structures major differences occur between the tyrrhenian and adriatic valley systems the tyrrhenian drainage mainly consists of longitudinal valleys displaying overall concave up longitudinal profiles the adriatic drainage is mainly constituted by transverse streams and shows less regular longitudinal profiles topographic features and the river valley architecture seem related to different styles and amounts of uplift in the three belts within the study area a coast to coast transect gaeta vasto transect gvt has been investigated in detail focusing the analysis on its axial sector around the apennines main divide main divide area mda a possible scheme of quaternary surface uplift along the gvt is proposed in the mda the main stages of landscape evolution and drainage organization can be reconstructed by means of the analysis of paleosurfaces coupled with study of the relict and present day drainage networks this allowed the recognition of a major phase of surface uplift exceeding 1500 m in the meta mainarde massif that occurred in response to thrusting during the pliocene for quaternary surface uplift a minimum value of 400 m can be estimated this study suggests that during the quaternary the peri tyrrhenian belt suffered a subdued uplift acting over small wavelengths 10 15 km while the axial and peri adriatic belts were subject to a larger and long wavelength 90 km surface uplift with maximum values about 700 m shifted to the ne of the axial belt and tapering to zero towards the adriatic coast the reconstructed pattern of uplift is coherent with the topographic properties of the three belts and with the observed drainage features

late quaternary sedimentation history of the lena delta abstract core and outcrop analysis from lena mouth deposits have been used to reconstruct the late quaternary sedimentation history of the lena delta sediment properties heavy mineral composition grain size characteristics organic carbon content and age determinations 14c ams and ir osl are applied to discriminate the main sedimentary units of the three major geomorphic terraces which form the delta the development of the terraces is controlled by complex interactions among the following four factors 1 channel migration according to the distribution of 14c and ir osl age determinations of lena mouth sediments the major river runoff direction shifted from the west during marine isotope stages 5 3 third terrace deposits towards the northwest during marine isotope stage 2 and transition to stage 1 second terrace to the northeast and east during the holocene first terrace deposits 2 eustasy sea level rise from last glacial lowstand to the modern sea level position reached at 6 5 ka bp resulted in back filling and flooding of the palaeovalleys 3 neotectonics the extension of the arctic mid ocean ridge into the laptev sea shelf acted as a halfgraben showing dilatation movements with different subsidence rates from the continent side differential neotectonics with uplift and transpression in the siberian coast ridges are active both likely have influenced river behavior by providing sites for preservation with uplift in particular allowing accumulation of deposits in the second terrace in the western sector the actual delta setting comprises only the eastern sector of the lena delta 4 peat formation polygenetic formation of ice rich peaty sand ice complex was most extensive 7 11 m in thickness in the southern part of the delta area between 43 and 14 ka bp third terrace deposits in recent times alluvial peat 5 6 m in thickness is accumulated on top of the deltaic sequences in the eastern sector first terrace

a stratigraphic framework for abrupt climatic changes during the last glacial period based on three synchronized greenland ice core records refining and extending the intimate event stratigraphy due to their outstanding resolution and well constrained chronologies greenland ice core records provide a master record of past climatic changes throughout the last interglacial glacial cycle in the north atlantic region as part of the intimate integration of ice core marine and terrestrial records project protocols have been proposed to ensure consistent and robust correlation between different records of past climate a key element of these protocols has been the formal definition and ordinal numbering of the sequence of greenland stadials gs and greenland interstadials gi within the most recent glacial period the gs and gi periods are the greenland expressions of the characteristic dansgaard oeschger events that represent cold and warm phases of the north atlantic region respectively we present here a more detailed and extended gs gi template for the whole of the last glacial period it is based on a synchronization of the ngrip grip and gisp2 ice core records that allows the parallel analysis of all three records on a common time scale the boundaries of the gs and gi periods are defined based on a combination of stable oxygen isotope ratios of the ice 18o reflecting mainly local temperature and calcium ion concentrations reflecting mainly atmospheric dust loading measured in the ice the data not only resolve the well known sequence of dansgaard oeschger events that were first defined and numbered in the ice core records more than two decades ago but also better resolve a number of short lived climatic oscillations some defined here for the first time using this revised scheme we propose a consistent approach for discriminating and naming all the significant abrupt climatic events of the last glacial period that are represented in the greenland ice records the final product constitutes an extended and better resolved greenland stratotype sequence against which other proxy records can be compared and correlated it also provides a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations

ams fabric and tectonic evolution of quaternary intramontane extensional basins in the picentini mountains southern apennines italy in this work we report the results of combined geological structural and anisotropy of magnetic susceptibility ams studies carried out on quaternary deposits in the picentini mountains southern apennines italy the study concerns four small continental basins acerno tizzano iumaiano and piano del gaudo related to fluvial lacustrine depositional environments ranging in altitude from 600 to 1 200 m a s l and strongly incised during recent time stratigraphic and structural analyses integrated by low and high field anisotropy of magnetic susceptibility ams show that the formation of these basins has been controlled by extensional and transtensional tectonics most of the ams sites exhibit a well defined magnetic foliation parallel to the bedding planes a well defined magnetic lineation has also been measured within the foliation planes in the iumaiano tizzano and piano del gaudo basins magnetic lineations cluster around nne ssw trend and are parallel to the stretching directions inferred by structural analysis of faults and fractures on the basis of structural sedimentological and high field ams data we suggest a tectonic origin for the magnetic lineation analogously to what has been observed in other weakly deformed sediments from neogene and quaternary extensional basins of the mediterranean region our results demonstrate that onset and the evolution of the investigated basins have been mainly controlled since lower pleistocene by nw se normal and transtensional faults this deformation pattern is consistent with a prevalent ne sw extensional tectonic regime still active in southern apennines as revealed by seismological and geodetic data

erosional landsurfaces of the campano lucano apennines s italy genesis evolution and tectonic implications abstract within the campano lucano apennines small but widespread relics of gentle erosional landsurfaces gels occur that are elevated several hundred metres above the present valley floors on the basis of our observations the old idea that all these relict landforms can be traced back to a single phase of quasi planation that affected the entire belt after thrust stacking and before a phase of final uplift must be rejected new field evidence and chronological constraints support the conclusion that the gel relics belong to various uncompleted cycles of erosion that occurred just during the construction of the chain i e late miocene to early pleistocene as many recent geological studies have pointed out the southern apennines chain is an arc shaped accretionary wedge that migrated as a thrusting system towards its retreating foreland by means of addition of thrust units to the front and loss of rifted portions at the rear tyrrhenian back arc basin also the spatial distribution of the various generations of gels their ages and their relations to the main structures and syn orogenic formations of the belt seem to agree with this geodynamic scenario here we propose a first approximation conceptual model that considers each generation of campano lucano apennines gels as largely formed when the thrust units on which they rest were located at low elevation near the coastline of the foredeep basin i e shortly after the entrance of those thrust units into the tectonic wedge then each gel as a matter of fact the compartment on which it rested was taken towards more and more internal parts of the wedge as frontal accretion continued owing to this relative migration the fate of each gel carrying compartment was to reach the part of the belt that was affected by extensional block faulting i e the tyrrhenian side of the chain each gel eventually reaching this domain was tectonically fragmented deeply cut by waves of fluvial dissection proceeding from the steep tectonic coast toward the ne and finally also rifted under the tyrrhenian sea other causes of gels fragmentation and dissection were probably the breaching of the chain s outer flank by out of sequence thrust and the up arching of the roof thrust system caused by the formation of deep anticlinal stacks on the contrary when forward propagation of thrusts continued for long periods the gels being carried toward the inner zone of the wedge could not have experienced deep dissection because the increase of their elevation a s l was compensated by their increasing distance from the foredeep coastline maintenance of low gradient along the river valleys thanks to a very low critical taper

morphology sedimentology and palaeohydraulic significance of large gravel dunes altai mountains siberia coarse gravel bedforms which resulted from pleistocene glacial outburst floods are identified as subaqueous dunes comparison of the morphology of these fossil structures with modern dunes shows that the form of two dimensional 2 d transverse dunes and 3 d cuspate and lunate dunes developed in coarse gravels is comparable with sand dune morphology within lesser scale geophysical flows the similarity of the steepest gravel dunes with equilibrium dunes in sand indicates that grain size is not a major factor in constraining primary duneform internal structure indicates that flow over 2 d dunes was relatively uniform but over 3 d bedforms flow was locally variable flow separation and complex streaming of flow occurred over the steepest 3 d dunes cross beds are thin and few approach the angle of repose consequently most dunes did not migrate primarily by avalanching but by stoss entrained gravel transported over the crests rolling down and depositing on the lee slopes the lee formed when flood power was waning some dunes were siightly planed down during falling stage because lee side cross beds tend to be steeper than the angle of the preserved lee slope however silt rich caps indicate that any height reduction was contemporary with the final deposition of foresets post flood modification has been negligible although the modern topography is subdued by loess deposits within the dune troughs lee side sediments are often finer than the stoss slope sediments which indicates

long history of pre wisconsin ice age cataclysmic floods evidence from southeastern washington state abstract cataclysmic ice age floods in the pacific northwest began as early as 1 5 2 5 ma on the basis of an evaluation of surface exposures and recent borehole studies within southeastern washington field evidence suggests at least two episodes of pre wisconsin i e 130 ka glacial outburst flooding a middle pleistocene flood is identified by normal magnetic polarity calcrete capped deposits that yield maximum th u age dates from 200 to 400 ka the deposits with reversed polarity are correlated to early pleistocene 780 ka floods while exposures of pre wisconsin deposits are limited because of erosion and or burial the record of earlier pleistocene flooding is preserved within giant flood bars these bars show incremental growth representing a composite from cataclysmic floods deposited intermittently through the pleistocene in one giant flood bar up to 100 m thick deposits interpreted as matuyama age indicate that the bar had grown to half its present height by 780 ka furthermore matuy

palaeolandscapes of southern apennines during the late early and the middle pleistocene abstract a palaeolandscape reconstruction of the southern apennine chain for the late early and the middle pleistocene is presented with the main aim of highlighting the evolution of this sector of the chain during a key period for the diffusion of palaeolithic humans in the italian peninsula during the calabrian stage 1 8 0 78 ma italy was an elongated peninsula narrower than present extended between the tyrrhenian and the foreland seas with two big islands nowadays gargano and murge in the central part of the foredeep basin this area started to emerge at the end of early pleistocene 1 2 0 78 ma when occasional communications among the islands and the southern apennine peninsula may have occurred probably in conjunction with eustatic low stands this scenario opens interesting questions on the migration pathways followed by ancient palaeolithic humans to reach the site of pirro nord 1 6 1 3 ma nw gargano the definitive emersion of the studied area was completed at the beginning of the ionian stage when several lakes punctuated the axial portion of the chain together with two great active volcanoes roccamonfina and vulture in the surroundings of the palaeo lakes palaeolithic humans started moving from 600 to 200 ka as indicated by the artefacts of acheulean tradition recovered among others at isernia la pineta and notarchirico

spacing of consecutive normal faulting in the lithosphere a dynamic model for rift axis jumping tyrrhenian sea we propose that the flexure of a broken elastic plate can determine the spacing of consecutive and localized zones of shearing on a lithospheric scale the model provides a dynamic explanation for rift axis migration and as a consequence for a wide rift mode of extension calculated values for rift axis shifting are consistent with the available observations and kinematic modelling results in the tyrrhenian basin the quantitative relation obtained between lithospheric fault spacing and the effective elastic thickness t of the lithosphere can be used in an inverse modelling approach in which paleo t e e values are calculated for a basin where the diachronous and spaced nature of rifting is known

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr