morphodynamic evolution of the orb river languedoc france evidence of eustatic tectonic and climatic controls this study aims to reconstruct the cenozoic and pleistocene morphodynamic evolution of the orb a mediterranean river which crosses all the structural units of the south massif central border a geomorphological and sedimentological analysis of detrital deposits was carried out as a basis for correlating the different formations and reconstructing the palaeodrainage heavy minerals were used to reconstruct the main sedimentary palaeochannels since the messinian the successive orb longitudinal profiles show anomalies which can be caused by structure and by interactions between fluvial dynamics and tectonics evidence of volcanic heavy minerals on the faugeres mountains and in the upper pliocene deposits of the languedocian piedmont demonstrates that a north south flow took place during the upper pliocene nevertheless a palaeo orb existed at the place of the present course when the basaltic lava flows were spreading but headward erosion did not reach them until the upper pleistocene because the orb middle and high terraces do not contain volcanic minerals sourced from the escandorgue the successive orb longitudinal profiles show that headward erosion due to pleistocene low sea levels does not reach beyond beziers and that a tectonic hinge has functioned near the shoreline the non lithologic knickpoints are explained by the montagne noire and avant monts uplift up until the pleistocene a progressive continental uplift is necessary to explain the orb terraces staircase in the beziers district and the fluctuations of incision from upstream to downstream are due to laterally differential movements which are isostatic effects of thick regressive deposits on the gulf of lion shelf during the cold periods copyright 2008 john wiley sons ltd

tectonic classification of cenozoic iberian foreland basins abstract the iberian microcontinent stands out because of its intense alpine intraplate deformation this is reflected in a large number of cenozoic basins of very different sizes most of the contacts between topographic highs and basins are thrust or strike slip faults all these basins seem to have undergone a common sedimentary evolution comprising four stages initiation of sedimentation intense syn tectonic infilling change from endorheic to exorheic drainage and accelerated erosion related to fluvial incision this simple evolutionary model shows a migration from east to west in which basins are still tectonically active at the atlantic margin of iberia this common evolution is also found in a series of geometrical characteristics such as the ratio r of length of strike slip fault and length of thrust fault that are very similar in both types of basin border settings thrust related basins are mainly associated with segmented pop downs whereas the main basins have the characteristics of open ramp basins strike slip related basins are mostly transpressive structures although small pull apart basins are usual along the vilarica and messejana faults for basin areas larger than 100 1000 km 2 a constant r value of 0 6 is found including the ebro duero madrid lower tagus and badajoz basins within the iberian microcontinent the total amount of cenozoic contractional deformation was distributed between strike slip and thrust faults with an r ratio close to 0 6 however for small basins this parameter seems to depend on the type of fault range or deformation belt pure strike slip transtension transpression and pop up independently of its local tectonic development

signatures of climate vs sea level change within incised valley fill successions quaternary examples from the texas gulf coast abstract the passive margin texas gulf of mexico coastal plain consists of coalescing late pleistocene to holocene alluvial deltaic plains constructed by a series of medium to large fluvial systems alluvial deltaic plains consist of the pleistocene beaumont formation and post beaumont coastal plain incised valleys a variety of mapping outcrop core and geochronological data from the extrabasinal colorado river and the basin fringe trinity river show that beaumont and post beaumont strata consist of a series of coastal plain incised valley fills that represent 100 kyr climatic and glacio eustatic cycles valley fills contain a complex alluvial architecture falling stage to lowstand systems tracts consist of multiple laterally amalgamated sandy channelbelts that reflect deposition within a valley that was incised below highstand alluvial plains and extended across a subaerially exposed shelf the lower boundary to falling stage and lowstand units comprises a composite valley fill unconformity that is time transgressive in both cross and down valley directions coastal plain incised valleys began to fill with transgression and highstand and landward translation of the shoreline paleosols that define the top of falling stage and lowstand channelbelts were progressively onlapped and buried by heterolithic sandy channelbelt sandy and silty crevasse channel and splay and muddy floodbasin strata transgressive to highstand facies scale architecture reflects changes through time in dominant styles of avulsion and follows a predictable succession through different stages of valley filling complete valley filling promoted avulsion and the large scale relocation of valley axes before the next sea level fall such that successive 100 kyr valley fills show a distributary pattern basic elements within coastal plain valleys can be correlated with the record offshore where cross shelf valleys have been described from seismic data falling stage to lowstand channelbelts within coastal plain valleys were feeder systems for shelf phase and shelf margin deltas respectively and demonstrate that falling stage fluvial deposits are important valley fill components signatures of both upstream climate change vs downstream sea level controls are therefore interpreted to be present within incised valley fills signatures of climate change consist of the downstream continuity of major stratigraphic units and component facies which extends from the mixed bedrock alluvial valley of the eroding continental interior to the distal reaches wherever that may be at the time this continuity suggests the development of stratigraphic units and facies is strongly coupled to upstream controls on sediment supply and climate conditions within hinterland source regions signatures of sea level change are critical as well sea level fall below the elevation of highstand depositional shoreline breaks results in channel incision and extension across the newly emergent shelf which in turn results in partitioning of the 100 kyr coastal plain valleys moreover deposits and key surfaces can be traced from continental interiors to the coastal plain but there are downstream changes in geometric relations that correspond to the transition between the mixed bedrock alluvial valley and the coastal plain incised valley channel incision and extension during sea level fall and lowstand with channel shortening and delta backstepping during transgression controls the architecture of coastal plain and cross shelf incised valley fills

modelled atmospheric temperatures and global sea levels over the past million years the climate has passed through a series of glacials and interglacials over the past million years but the nature of this cyclicity in terms of temperature ice volume and sea level and the underlying causes are not well known bintanja et al use a new method to deduce a one million year time series of these variables the reconstructed records are much longer than other methods have provided for any of these variables individually the most intense glacial stages were 17 c colder than today and most of the continental ice was present in north america strong cooling in the beginning of glacials was found to precede ice sheet build up these findings may shed light on the causes of ice age cycles marine records of sediment oxygen isotope compositions show that the earth s climate has gone through a succession of glacial and interglacial periods during the past million years but the interpretation of the oxygen isotope records is complicated because both isotope storage in ice sheets and deep water temperature affect the recorded isotopic composition1 2 3 4 5 separating these two effects would require long records of either sea level or deep ocean temperature which are currently not available here we use a coupled model of the northern hemisphere ice sheets6 and ocean temperatures forced to match an oxygen isotope record for the past million years compiled from 57 globally distributed sediment cores to quantify both contributions simultaneously we find that the ice sheet contribution to the variability in oxygen isotope composition varied from ten per cent in the beginning of glacial periods to sixty per cent at glacial maxima suggesting that strong ocean cooling preceded slow ice sheet build up the model yields mutually consistent time series of continental mean surface temperatures between 40 and 80 n ice volume and global sea level we find that during extreme glacial stages air temperatures were 17 1 8 c lower than present with a 120 10 m sea level equivalent of continental ice present

a 3 d model of quaternary terrace development simulations of terrace stratigraphy and valley asymmetry a case study for the allier terraces limagne france the combined effects of climate and tectonism on general terrace stratigraphy and valley asymmetry during the last half million years in the allier system france are simulated by a 3 d conceptual model limter this model allows the formulation and evaluation of long term terrace formation scenarios for the allier system simulation results suggest that terrace stratigraphy in the study area is mainly the result of internal dynamics and climatic change local tectonism contributed to the development of unpaired terraces while the general regional uplift played a dominant role in determining terrace formation and preservation in general

river incision and terrace formation in the late cenozoic of europe abstract late cenozoic environmental changes which affected european rivers are reviewed focusing especially on those of mid pleistocene times c 1 2 0 8 ma or around mis 22 and thereafter these involved dominating but fluctuating cold climate periglacial conditions shorter but major episodes of glaciation and brief interglacials there were also related sea level and tectonic responses the known history of european rivers in this period is individually varied but is predominantly marked by multiple stages of episodic incision the form of which changed in style at around the mid pleistocene transition it is suggested that the nature of climatic oscillations the dating of incision episodes and the processes that achieve this incision are as yet insufficiently understood fluvial process studies suggest that the onset of incision may broadly relate to changes in slope discharge sediment load and calibre and bedrock erodibility and these may all have been transformed as the direct or indirect result of mid pleistocene climatic changes common properties of basal sediments on strath terraces suggest that it was during the extended but variable cold stage episodes that both valley deepening and lateral widening occurred and that climatic change was the principal driver of episodic deep valley incision

coupled modes of large scale climatic variables and regional precipitation in the western mediterranean in autumn the variability of autumn precipitation in the western mediterranean and its relationship to the large scale atmospheric variability during the period 1948 to 1989 is assessed a singular value decomposition analysis is used to establish modes of coupled variability between regional precipitation and geopotential height z300 zonal u wind and meridional v wind wind components at the 300 hpa level the z300 precipitation coupling which accounts for 52 of the total squared covariance is strong during the autumn the first z300 coupled mode in its positive phase is characterised by a dipole structure with negative anomalies over scandinavia and positive anomalies over the iberian peninsula in the z300 and negative precipitation anomalies in the western mediterranean in its negative phase a coupled pattern is found showing a high over low block and positive precipitation anomalies over the mediterranean area the coupling depicted by the second mode is weaker than that found in the first mode the second coupled mode 21 of the total squared covariance is characterised by negative anomalies in the eastern north atlantic and positive ones over north africa and the central mediterranean in the z300 and negative anomalies in the regional precipitation consistent with the results of the two first modes mentioned the coupled patterns of either u wind precipitation or v wind precipitation are found to be coherent with those for z300 precipitation composite maps were obtained to give a representation of the average circulation associated with coherent precipitation variability in the western mediterranean the regional impacts of both modes are investigated and the large scale dynamic patterns presented are important modes of variability taking into account data for the whole of the twentieth century results show that the first singular mode is responsible for the decadal trends and long term changes in precipitation the late 1970s and 1980s is shown as the drier period and the late 1950s and early 1960s as the wettest years of the century

reconstructing the interacting effects of base level climate and tectonic uplift in the lower mino river terrace record a gradient modelling evaluation the origin of the lower mino river terraces in the nw iberian peninsula has been a topic of debate since the 1940s various hypotheses about their main controlling factors have been put forward but general consensus is still lacking field studies of terrace distribution and the weathering of quartzite pebbles in the terrace deposits demonstrated that terrace longitudinal correlation is not parallel to the current river bed in addition the longitudinal profile model fluver2 was used to simulate the profile evolution of the mino river over the past 450 ka a reconstructed longitudinal profile and an offshore climate record were used as inputs several scenarios with variable uplift rates were investigated and evaluated against properties of four selected reaches along the river for a match with the number of terraces their relative altitude timing and sediment thickness an uplift scenario with a net constant vertical uplift rate of 0 08 m ka 1 yielded the best results the best fit scenarios indicate that base level changes from glacioeustatic changes in combination with tectonic uplift are the main driving forces of the observed terrace formation and valley incision contrary to most nw european fluvial systems the timing of upstream controlled sediment supply has a less dominant effect on terrace formation this can be explained by the close proximity to the narrow passive atlantic margin

climatic variability of marine isotope stage 7 direct land sea ice correlation from a multiproxy analysis of a north western iberian margin deep sea core abstract the direct land sea ice correlation performed in the north western iberian margin core md01 2447 shows that marine isotope stage 7 mis 7 is marked by an alternation of five warm and cold periods this climatic variability is in general synchronously detected in marine and terrestrial realms by our record termination iii is marked by three cold episodes the last one interrupts the forest development in north western iberia related to the deglacial climatic amelioration it begins in the middle of termination iii but the maximal cold conditions occur at the beginning of low ice volume conditions mis 7 is characterised by three periods of very low ice volume associated with marine and continental high temperatures in and off north western iberia the correlation of our record with odp site 980 shows that the climatic variability detected in the north western iberian region has also an imprint in northern north atlantic it also highlights that most of the cold periods are associated with iceberg discharges in the north atlantic the comparison of the north western iberian margin sequence with the long european pollen records has allowed refining the correlation of the marine and continental stratigraphy for mis 7

the cape mendocino california earthquakes of april 1992 subduction at the triple junction the 25 april 1992 magnitude 7 1 cape mendocino thrust earthquake demonstrated that the north america gorda plate boundary is seismogenic and illustrated hazards that could result from much larger earthquakes forecast for the cascadia region the shock occurred just north of the mendocino triple junction and caused strong ground motion and moderate damage in the immediate area rupture initiated onshore at a depth of 10 5 kilometers and propagated up dip and seaward slip on steep faults in the gorda plate generated two magnitude 6 6 aftershocks on 26 april the main shock did not produce surface rupture on land but caused coastal uplift and a tsunami the emerging picture of seismicity and faulting at the triple junction suggests that the region is likely to continue experiencing significant seismicity

geomorphological correlation of the tectonically displaced tejo river terraces gaviao chamusca area central portugal supported by luminescence dating abstract a suite of fluvial terraces t1 t6 from top to bottom of the staircase occur along a 70 km stretch of the tejo river in central portugal between the small towns of gaviao and chamusca terrace correlation was based upon the following a aerial photograph analysis geomorphological mapping and field topographic survey b sedimentology of the terrace deposits namely the maximum particle size clast composition and lithofacies identification and c k feldspar infrared stimulated luminescence irsl dating of the three lower terraces levels as quartz optically stimulated osl signal of the samples from these terraces was too close to saturation for all but two samples the two upper terraces t1 and t2 lack suitable materials for luminescence dating e g sands silts but also their probable ages are beyond the upper range of the dating method faults affecting terraces and older deposits have been reported the luminescence dating results suggest that some assignments of local terrace remnants were incorrect because of fault related vertical displacements the luminescence dating procedure also included a correction for anomalous fading in order to obtain more reliable estimates of the burial ages the fading rate was identical for all samples so for correlation of the terraces anomalous fading of the feldspar irsl signal is considered not to be a significant problem the t5 terrace has corrected ages of 42 99 ka the t4 from 107 to 222 ka and the t3 terrace has a minimal age of 300 ka fluvial incision appears to have been principally controlled by regional uplift but also by localised movements along fault structures using the corrected ages of the t4 surface a time averaged incision rate can be quantified as follows 1 0 29 m ka for reach iii 2 0 53 m ka in the chamusca area east side on reach iv and 3 0 13 m ka in the mato miranda area west side on reach iv the less uplifted block according to the geomorphic framework

the river mondego terraces at the figueira da foz coastal area western central portugal geomorphological and sedimentological characterization of a terrace staircase affected by differential uplift and glacio eustasy abstract a geomorphological and sedimentological characterization of the river mondego terraces in the figueira da foz coastal area portugal is presented the relief is dominated by a pliocene a marine sandy unit 10 15 m thick reaching 250 m a s l that covers a shore platform surface the river mondego has incised into the pliocene relief and its long drainage evolution is recorded within a series of inset river terrace landforms these river terraces are better preserved on the right hand northern bank where they form a staircase developed against the uplifted serra da boa viagem structure a set of five river terraces represented by sedimentary deposits or erosional straths are identified namely t1 at 128 125 m t2 at 101 90 m t3 at 70 60 m t4 at 29 24 m t5 at 11 10 m a s l some luminescence dating ages were obtained from the river terrace deposits 390 ka from the middle of t4 170 ka from the top of t4 120 ka from the base of t5 109 ka from t5 average age for three samples and 53 3 ka from a colluvium at 35 m a s l some differences in altitude of the uppermost sedimentary unit and of the terraces are here interpreted as resulting from vertical displacements of active faults during the quaternary the main tectonic structure is the wnw ese trending quiaios fault responsible for the regional tilting towards sw other probably active faults and tectonic lineaments trend nnw sse to n s nne ssw to ne sw and wnw ese this study reports a long term uplift rate of 0 004 0 055 m ka for the last 3 6 ma but 0 017 0 118 m ka for the last 1 8 ma using as references respectively the base and the surface of the uppermost sedimentary unit the facies associations that characterize the older terrace deposits t1 and t2 consist of poorly sorted fluvial sandy gravels and silts but also some colluvium at the top of each terrace the younger terraces t3 t4 and t5 show better developed sedimentary structures and less sedimentary matrix the sedimentary features are indicative of both fluvial and coastal environments estuary and beach as nowadays under conditions of continuous uplift the episodes of river down cutting valley widening and aggradation in the studied area can be attributed to the rise and fall of sea level in response to the global quaternary climatic fluctuations considering the number of terraces and the dating obtained it seems that the control of terrace genesis in this coastal area should be dominated by glacio eustasy whereby episodic valley incision would have been determined by periods of very low sea level probably at 460 410 ka t3 t4 mis12 200 125 ka t4 t5 mis6 and 100 14 ka t5 recent alluvial infill late mis5 mis4 mis3 and mis2 some sandy colluvium deposits on the slopes are probably related with mild cold and wet climate conditions during the period 60 to 32 ka the aeolian dunes are younger cold to temperate dry conditions mis2 and mis1

holocene strath terraces climate change and active tectonics the clearwater river basin olympic peninsula washington state the 400 km 2 clearwater river basin located on the pacific flank of the actively uplifting olympic mountains of western washington state contains a well preserved flight of holocene fluvial terraces we have collected a large data set of numeric ages from these terraces that is used to elucidate the geomorphic fluvial active tectonic and climatic processes that operate at holocene spatial and temporal scales detailed field mapping reveals three prominent holocene straths and their overlying terrace deposits terrace ages fall into three broad ranges ca 9000 11 000 yr b p qt4 4000 8000 yr b p qt5 and 0 3000 yr b p qt6 terrace deposit stratigraphy sedimentology and age distributions allow us to consider two alternative models for their genesis the favored model states that the terrace ages are coincident with lateral incision of the clearwater channel emplacement of the terrace alluvium and the carving of the straths vertical incision of the clearwater channel was primarily relegated to the brief 1000 yr intervals when we have no record of terraces alternatively the straths were carved as the channel incised vertically during the brief time periods between dated terrace deposits and the terrace ages record a subsequent long time of alluviation atop the straths and concomitant termination of vertical incision in both models we envision a clearwater river channel at or near capacity with a temporally variable rate of both lateral and vertical incision small deviations from this at capacity condition are driven by variations in the liberation and delivery of hillslope sediment to the channel we consider several causes for variable hillslope sediment flux in this tectonically active setting including holocene climate change and ground accelerations related to earthquakes holocene rates of vertical incision are reconstructed along nearly the entire clearwater valley from the wide distribution of dated terraces incision rates clearly increase upstream mimicking a pattern documented for pleistocene terraces in the same basin however the rates are 2 3 times those determined for the pleistocene terraces the faster holocene incision rates may be interpreted in terms of an increase in the rates of rock uplift however we favor an alternative explanation in which the holocene rates represent a channel rapidly reacquiring its stable graded concavity following protracted periods of time in the pleistocene when it could not accomplish any vertical incision into tectonically uplifted bedrock because the channel was raised above the bedrock valley bottom by climatically induced alluviation these results illustrate how even in tectonically active settings representative rates of rock uplift inferred from studies of river incision should be integrated over at least one glacial interglacial cycle

lateglacial and holocene coastal evolution in the minho estuary n portugal implications for understanding sea level changes in atlantic iberia the absence of accurate sea level index points in sw europe has long precluded the development of holocene sea level curves and the correct understanding of tectonic activity in order to understan

dating the tejo river lower terraces in the rodao area portugal to assess the role of tectonics and uplift abstract the tejo river is one of the major drainages in iberian peninsula it is a long lived system ca 3 4 ma and provides an archive of long term landscape development and environmental change controlled by tectonics climate and eustasy the most upstream portuguese reach of the tejo river 200 km from the atlantic coast shows evidence for five fluvial terraces t1 to t5 with elevations reaching more than 120 m above the modern river bed a chronological framework for these terraces is established here by integrating geomorphological stratigraphical and archaeological information with ages from luminescence dating optically stimulated luminescence dating of k feldspar involving the correction for anomalous fading of the luminescence signal indicates that the younger terraces have a probable age range of t5 31 to 40 ka and t4 100 to 280 ka we deduce that the related major fluvial changes are likely to have been as follows 10 m of aggradation from 280 to 100 ka 0 06 m ka 14 m of incision from 100 to 40 ka 0 23 m ka 8 m of aggradation from 40 to 31 ka 0 89 m ka 16 m of incision during the last 31 ka 0 52 m ka these values indicate that the duration and rate of both aggradation and river downcutting episodes were variable there is widespread evidence for neotectonic activity in this intraplate region neither eustatic nor climatic changes during the quaternary provide clear trends that might explain the observed pattern of valley incision thus we conclude that this tectonic activity is the most likely driving mechanism in the study area the probable age of the tejo river sediments deposited before the beginning of valley incision allows the calculation of a time averaged incision rate of 0 07 to 0 10 m ka over the last 2 6 ma this long term incision was probably determined by an increase in the relative uplift rate resulting from the intensification of intraplate compressive stress during the late cenozoic fluvial incision stage the rodao depression underwent less uplift than the adjacent areas along the river in which the tejo has incised a narrow valley into basement rock with almost no terrace development terrace formation was also promoted by soft bedrock tertiary arkoses and by impoundment of alluvium behind resistant barriers crossed by the river geomorphological evidence for terrace tectonic offset was also supported by luminescence dating

simulating internal and external controls on fluvial terrace stratigraphy a qualitative comparison with the maas record palaeohydrological studies indicate that the use of sedimentary palaeoclimatic indicators in fluvial sediments still requires rigorous calibration of the climatic controls on the formation of those indicators an explorative attempt is made using a simulation experiment with the fluver2 model the simulation illustrates that climate control on the erosion sedimentation behaviour of a large fluvial system differs along the fluvial system while in the uplifting hinterland only glacial extremes are recorded as sediments with a relatively limited preservation chance as terraces due to the uplift the more downstream reach towards the hinge zone displays a sensitive fluvial record registering even stadial interstadial dynamics well preserved in an extensive glacial interglacial terrace staircase downstream in a subsiding basin the most complete sedimentary record is preserved which still contains temporal gaps of approximately 20 related to the spatial delay effects of the external control of climate and related base level change a systematic comparison of simulated climate changes and resulting fluvial dynamics illustrates that due to the internal control of fluvial systems a one to one correlation between recorded fluvial dynamics and climate change becomes less the further one moves downstream along the longitudinal profile a qualitative comparison of the simulation results with the maas record reveals an interesting match suggesting that the simulated system dynamics may well apply the maas system

tilting neotectonics of the guadiamar drainage basin sw spain the guadiamar river ows from the southern iberian massif to the guadalquivir foreland basin sw spain its drainage basin displays asymmetries in the stream network the arrangement of alluvial terraces and the con guration of the trunk river valley the stream network asymmetry was studied using morphometric measures of transverse topographic sym metry asymmetry factor and drainage basin shape the alluvial terraces were studied through the lithologic logs of more than a hundred boreholes and eld mapping the morphometric methods demonstrate a regional tectonic tilting toward the sse causing both the migration of the guadiamar river toward the east and the migration of the guadiamar tributaries toward the southwest as a consequence of the guadiamar river migration an asymmetric valley developed with a steep eastern margin caused by river dissection and a gentle western margin where the main alluvial deposits are found the ages obtained using the 14c analysis of samples from several alluvial deposits show that the river migration and thus tilting has occurred during the holocene as well as earlier in the quaternary this interpretation revises the guadiamar longitudinal fault assumed by previous studies copyright 2003 john wiley sons ltd

bedrock incision rock uplift and threshold hillslopes in the northwestern himalayas the topography of tectonically active mountain ranges reflects a poorly understood competition between bedrock uplift and erosion dating of abandoned river cut surfaces in the northwestern himalayas reveals that the indus river incises through the bedrock at extremely high rates 2 12 mm yr 1 in the surrounding mountains the average angles of hillslopes are steep and essentially independent of erosion rate suggesting control by a common threshold process in this rapidly deforming region an equilibrium is maintained between bedrock uplift and river incision with landsliding allowing hillslopes to adjust efficiently to rapid river down cutting

increasing vegetation and climate gradient in western europe over the last glacial inception 122 110 ka data model comparison high resolution terrestrial pollen and marine planktic and benthic isotopes coarse fraction and n pachyderma s analyses have been performed in the marine isotope stage mis 5 interval of images core md99 2331 retrieved in the northwestern iberian margin this study shows the occurrence of a zeifen interstadial stadial succession on land and in the ocean during the first part of mis 5e in northwestern iberia the eemian is marked from 126 to 122 ka by the development of deciduous quercus forest at the same time as mediterranean forest colonised southern iberia and deciduous quercus corylus forest occupied northernmost european regions from 121 to 115 ka carpinus betulus forest developed in nw iberia indicating a winter cooling by 2degreesc on land and an increase in annual precipitation by 100 200 min along with a sea surface temperature sst decreasing trend off iberia a similar cooling has been documented at the same time in northern germany 52degreesn by the replacement of deciduous forest by coniferous abies picea formations implying a southward displacement of the deciduous tree line between similar to60degreesn and 50degreesn as early as 120 ka the southward migration of the tree line between 72degreesn and 58degreesn simulated by the earth model of intermediate complexity mobidic from 122 and 120 ka and considered as a major process to initiate the last glaciation is therefore compatible with data between 115 and 110 ka the substantial ice accumulation in northern high latitudes mis 5e 5d transition was synchronous with successive drops c26 and c25 in northeastern atlantic sst in northwestern iberia abies pinus trees developed at the expense of quercus carpinus forest a tundra like environment occupied northern germany marking the end of the interglacial in northwestern europe at 115 ka and boreal forest likely colonised northeastern france the first displacement of the vegetation belts at 121 ka was enhanced at 115 ka indicating an amplification of the vegetation and climate gradients in northeastern atlantic and european borderlands probably related with the well developed ice caps at that time the comparison between the general trend in the estimated and simulated mobidic winter and summer temperatures for latitudes between 35 and 45degreesn shows that both follow quite straightforwardly the precession signal although the simulated and reconstructed temperatures agree better in the south than north of 40degreesn annual precipitation is exhibiting opposite trend in the data and in the model this contradiction is likely the fact that the zonal climate simulated by the model may not accurately represent the regional climate features as reconstructed from the pollen c 2004 elsevier b v all rights reserved

complex tectonic and tectonostratigraphic evolution of an alpine foreland basin the western duero basin and the related tertiary depressions of the nw iberian peninsula abstract the tectonic and tectonostratigaphic evolution of foreland basins and related tertiary depressions are the key to investigate deformation history and the uplifting of the continental lithosphere of the alpine pyrenean orogeny the northern part of the duero basin is the foreland basin of the cantabrian mountains which are in turn the western part of the pyrenean orogen we have studied the western sharp end of the duero foreland basin and its relation to the tertiary deposits of the nw iberian peninsula and the topography evolution in order to propose a coherent tectonic and tectonosedimentary model that could explain all tertiary deposits we have analysed the depositional environment stratigraphic sequences paleocurrents and established a correlation of the main outcrops besides a detailed structural mapping of the alpine structures that limit and affect the main tertiary outcrops has been carried out the tertiary deposits of the nw iberian peninsula depressions are affected and fragmented by alpine structures that limit their extensions and locations the stratigraphic succession is similar in the nw tertiary outcrops they are mainly terrigenous and carbonated continental deposits formed by assemblage of alluvial fans developed at the mountains front in arid or semiarid conditions three formations can be identified in the main depressions toral fm santalla fm and medulas fm the nw tertiary outcrops were the western deposits of the duero foreland basin that surrounded the lateral termination of the pyrenean orogen these deposits were fragmented and eroded by the subsequent uplift of the galaico leoneses mountains and the ne sw strike slip faults activity broken foreland basin only the latest stages of some of these outcrops can be considered as intramontane basins as traditionally have been interpreted the sedimentation started in the northeast oviedo infiesto during the eocene and migrated to the west as pontes during the late oligocene early miocene times meanwhile southern areas were far away from the tectonic activity el bierzo o barco monforte sarria depressions

numerical modeling of fluvial strath terrace formation in response to oscillating climate many river systems in western north america retain a fluvial strath terrace rec ord of discontinuous downcutting into bedrock through the quaternary their importance lies in their use to interpret climatic events in the headwaters and to determine long term incision rates terrace formation has been ascribed to changes in sediment supply and or water discharge produced by late quaternary climatic fluctuations we use a one dimensional channel evolution model to explore whether temporal variations in sediment and water discharge can generate terrace sequences the model includes sediment transport vertical bedrock erosion limited by alluvial cover and lateral valley wall erosion we set limits on our modeling by using data collected from the terraced wind river basin two types of experiments were performed constant period sinusoidal input histories and variable period inputs scaled by the marine 18 o rec ord our simulations indicate that strath terrace formation requires input variability that produces a changing ratio of vertical to lateral erosion rates straths are cut when the channel floor is protected from erosion by sediment and are abandoned and terraces formed when incision can resume following sediment cover thinning high sediment supply promotes wide valley floors that are abandoned as sediment supply decreases in contrast wide valleys are promoted by low effective water discharge and are abandoned as discharge increases widening of the valley floors that become terraces occurs over many thousands of years the transition from valley widening to downcutting and terrace creation occurs in response to subtle input changes affecting local divergence of sediment transport capacity formation of terraces lags by several thousand years the input changes that cause their formation our results suggest that use of terrace ages to set limits on the timing of a specific event must be done with the knowledge that the system can take thousands of years to respond to a perturbation the incision rate calculated in the field from the lowest terrace in these systems will likely be higher than the rate calculated by using older terraces because the most recent fluvial response in the field is commonly downcutting associated with declining sediment input since the last glacial maximum this apparent increase in incision rates is observed in many river systems and should not necessarily be interpreted as a response to an increase in rock uplift rate

differential impact of small scaled tectonic movements on fluvial morphology and sedimentology the huang shui catchment ne tibet plateau abstract the aim of this paper is to investigate the morphological implications of the interplay between tectonic movements at different rates timescales and spatial extent in a catchment of intermediate size the huang shui river a main tributary of the yellow river in the ne tibet plateau river incision started from a peneplain like surface that developed in post miocene pliocene times at the end of the tertiary a general tectonic uplift of the tibetan plateau initiated river incision this general uplift also caused local fragmentation of the huang shui catchment into blocks kilometers or maximally a few tens of kilometers of local extent that have subsided and or uplifted relative to one another fluvial deposition of 30 m in the subsiding blocks contrasts with erosion and formation of gorges in the uplifted blocks incision into the former peneplain was not continuous but a staircase of terraces developed under climatic influences terrace deposits are sometimes capped by interglacial soils or soil derived material apparently terrace incision occurred at the transition to the next cold period the different rates of uplift and subsidence of the individual blocks resulted in the simultaneous development of erosion and accumulation terraces of different sizes within the same catchment even within the same tectonic block this makes it impossible to connect the terraces of the different blocks except for the three youngest terraces representing the last 300 000 years thus illustrating the uniform tectonic history of the catchment since that time

the fluvial cycle at cold warm cold transitions in lowland regions a refinement of theory abstract a previously established non linear theory of river cyclicity as a response to climate change states that short phases of fluvial instability occur both at the transition from relatively warm temperate to cold periglacial and from relatively cold to warm periods such instability typically starts with vertical erosion successively followed by sedimentary fill of the erosive scar in spite of frequent confirmation of this theory by geomorphological reconstructions a few problems arise first there are fewer incision phases than climatic transitions secondly remnants of erosion at cold warm transitions are scarce in contrast to obvious erosion relics at warm cold transitions furthermore it appears that the incision style is strikingly different at both kinds of climatic transitions similarly the long stable phases are also expressed in terms of different floodplain development in cold and warm periods these arguments require a modification of the general non linear theory at the transition from relatively temperate to colder conditions rivers transformed gradually from a regular low energy single channel course to a periodically high energy multi channel type the latter braided type is characterized by intense lateral movement rather than by deep vertical erosion this results in a well expressed morphology of wide extensive floodplains and terraces in contrast the linear and constrained meandering channels incise with small width depth ratio and build floodplains of limited lateral extent consequences are twofold 1 the spatial limitation of the deeply incised meandering valleys at the beginning of warm periods counts against their recognition 2 relatively strong lateral migration of the braided rivers removes most traces of previous meandering systems which contrasts with the limited lateral activity of confined meandering channels it means that in a warm cold warm alternation generally only one phase of vertical erosion is preserved the one that is caused by the high energy braided river at the start of the cold period

correlating river terrace remnants using an equotip hardness tester an example from the mino river northwestern iberian peninsula abstract this paper describes a new method to distinguish river terrace levels based on clast hardness and degree of weathering measured with an equotip hardness tester the technique was applied to a series of terraces on the mino river in the northwestern iberian peninsula where the lack of suitable material high degree of weathering and intense iron cementation precluded routine dating detailed mapping demonstrated that terrace sediments occupy a range of altitudes that make assignment to a specific terrace and or correlation between levels difficult statistical analysis of the equotip hardness data from quartzite clasts using k means clustering allowed four probable terrace levels to be identified a series of t tests generally supported these groupings a fifth lowermost terrace level was not included in the analysis because of limited exposure above a reservoir clast hardness and degree of terrace weathering were generally consistent with progressive river downcutting the occurrence of faulted sediments however suggested that terrace elevations were modified locally by post depositional tectonic movements which may explain why probable younger terraces in some sectors of the mino river are at higher elevations than older terraces in adjacent sectors the equotip tester helped to resolve stratigraphic uncertainties and to assign deposits to specific terrace levels and was found to be a useful tool to distinguish and correlate river terraces

wet to dry climatic trend in north western iberia within heinrich events abstract the direct sea land correlation applied to core md99 2331 retrieved from the north western iberian margin shows a two phase pattern within heinrich events 4 2 and 1 in the ocean and in the adjacent landmasses changes between wet cold and dry cool conditions in the iberian peninsula detected during these extreme events cannot be explained by a simple oceanographic mechanism related to changes in the strength of the atlantic meridional overturning circulation here we propose an additional atmospheric mechanism able to produce this scenario based on the comparison between the md99 2331 record and other available palaeoclimate sequences from the north atlantic region 18 75 n and 0 75 w the climatic asymmetry observed between mid and subtropical eastern north atlantic latitudes wet dry and the blake outer ridge dry wet during h4 h2 and h1 can be explained by changes in the position of the atlantic jet stream during the first phase of h4 h2 and h1 the atlantic jet stream was located further south following the southward displacement of the oceanic thermal front as far south as 35 37 n on the contrary during the second phase of h4 h2 and h1 the jet stream was located further north following the northward displacement of this thermal front as far north as 42 n from the atmospheric point of view these two phases are reminiscent of the present day negative and positive prevailing modes of the north atlantic oscillation nao respectively but high resolution studies of additional north atlantic key sites and climate simulations are needed to confirm the hypothesis of a nao like mechanism operating on millennial timescales

analysis of drainage basin symmetry as a rapid technique to identify areas of possible quaternary tilt block tectonics an example from the mississippi embayment there is a coincidence of seismicity and major river valleys in the southwestern mississippi embayment that suggests control of the drainage pattern by northwest trending faults pleistocene river terraces reveal a strong southwestward preferred river migration in this region that may be a result of fault block tilting a rapid new technique of drainage basin analysis is herein presented that quantifies transverse topographic basin symmetry these data permit discrimination of random stream migrations and regionally preferred stream migrations and identify the direction of maximum migration if bedrock dip can be shown to be a negligible influence on stream migration then the direction of regionally preferred migration implies a period of ground tilting in that direction drainage basin asymmetry vectors bearing and degree of asymmetry calculated from transverse topographic profiles of 271 4 km basin segments in the study area suggest preferred stream migration in response to west southwest ward ground tilting bearing 259 the eastward regional dip of bed rock horizons only locally influences migration river terrace distributions reveal a chronology of stream migration episodes southwestward migration in the ouachita saline and arkansas river basins occurred during early to middle pleistocene time in the southwestern mississippi embayment a wisconsin early holocene southwestward migration episode is evidenced along southeast flowing reaches of the ouachita and arkansas rivers but not along the southeast flowing reach of the intervening saline river suggesting that these rivers overlie separate northwest trending tilt blocks although this technique does not provide direct evidence of ground tilting it provides a quick look method of identifying possible tilting elements in neotectonic regions using only topographic maps this technique is of greatest utility where active faults are concealed or poorly exposed such as in the mississippi embayment

local stress fields and intraplate deformation of iberia variations in spatial and temporal interplay of regional stress sources tertiary to present deformation in the interior of the iberian peninsula reflects spatial and temporal variations of the activity of the plate boundaries local deformation patterns observed in many of the numerous intraplate tertiary basins and their borders such as the madrid basin and the sierra de altomira are at first sight incompatible with the regional stress field under which they were formed we demonstrate however that they can be explained as the effect of several stress fields that acted on the iberian peninsula from earliest tertiary onward data on local deformation can constrain both magnitudes and directions of forces acting on the plate boundaries of iberia enabling us to estimate the relative importance of the different plate driving and deforming mechanisms providing further constraints on the tectonic evolution of iberia

river terrace formation modelling and 3 d graphical simulation a model on river terrace formation is presented written in pascal and run on a vax 8600 the model calculates the influence of a fluvial system on the relief of an area with macroscopical dimensions 10kmx20kmx0 5km over a period of 2 5 million years model input relies on uplift and alternations in discharge and sediment load as a function of climatic changes the output of the model are 3 dimensional grid drawings which visualize the impact of uplift discharge and sediment load on a landscape model formulation is based on empirical information on fluvial systems which was incorporated in the model by means of a slightly adapted way of finite state modelling in which decisions act as thresholds the model is organized using two entities river and landscape with attributes that have values within a specific realistic domain the model produces plausible x y z and x y t plots in the light of existing geomorphological theories the described modelling procedure shows that it is possible to simulate river terrace formation threedimensionally with the use of empirical information

lithospheric memory state of stress and rheology neotectonic controls on europe s intraplate continental topography abstract to date research on neotectonics and related continental topography development has mostly focused on active plate boundaries characterized by generally high deformation rates the intraplate sedimentary basins and rifts of the northern alpine foreland are associated with a much higher level of neotectonic activity than hitherto assumed seismicity and stress indicator data combined with geodetic and geomorphologic observations demonstrate that europe s intraplate lithosphere is being actively deformed this has major implications for the assessment of its natural hazards and environmental degradation the lithosphere of the northern alpine foreland has undergone a polyphase evolution with an intense interplay between upper mantle thermal perturbations and stress induced intraplate deformation that points to the importance of lithospheric folding of the thermally weakened lithosphere in this paper we address relationships between deeper lithospheric processes neotectonics and surface processes in the northern alpine foreland with special emphasis on tectonically induced topography the objectives are to quantify the effects of ongoing alpine collision and atlantic ridge push on the intraplate deformation in europe and its impact on topography evolution and related natural hazards this paper reviews the four dimensional topographic evolution of the european lithosphere through a multi disciplinary approach linking geology geophysics and geotechnology until now research on neotectonics and related topography development of intraplate regions has received little attention our study examines a number of selected natural laboratories in continental europe from orogen through platform to continental margin these natural laboratories include the carpathians pannonian system the northwest european platform iberia and the atlantic continental margin we focus on lithosphere memory and neotectonics with special attention to the thermo mechanical structure of the lithosphere mechanisms of large scale intraplate deformation late neogene anomalies in subsidence and uplift and links with surface processes and topography evolution

contrasting impacts of dansgaard oeschger events over a western european latitudinal transect modulated by orbital parameters abstract terrestrial and marine proxies pollen planktic and benthic foraminiferal oxygen isotopes alkenone and foraminifer derived sea surface temperatures ssts ice rafted debris from images deep sea cores md95 2042 and su81 18 37 n 10 w md99 2331 and md03 2697 42 n 9 w and md04 2845 45 n 5 w show that western european and offshore environments were strongly affected by dansgaard oeschger d o and heinrich h events we concentrate here on latitudinal variability in the forest cover extent and composition of western europe during the succession of d o events showing new pollen records for core md04 2845 and for marine isotopic stages mis 3 and 4 of core md99 2331 in general cold ssts characteristic of greenland stadials were contemporaneous with the expansion of semi desert or steppic vegetation while greenland interstadials were synchronous with the expansion of forest our data reveal that the amplitude of atlantic and mediterranean forest expansions differs for any given d o warming during the glacial period 74 18 ka in the western mediterranean d o 16 17 and d o 8 and 7 corresponding to minima in precession were associated with strong expansion of forest cover contrasting with weak expansion of forest cover during d o 14 and 12 the opposite pattern is revealed at the atlantic sites further north the strongest greenland warmings are recorded for d o 19 11 and 8 this contrasting latitudinal climatic scenario is compared with other northern hemisphere records revealing similarities between the mediterranean climate and the asian monsoon regime which may relate to a summer atmospheric teleconnection between the two regions comparable to the present day situation parallels between mediterranean climate enhancement and peaks in global methane ch 4 during the last glacial period suggest a significant role of monsoon activity in determining ch 4 emission from wetlands

fluvial responses to climate and sea level change a review and look forward summary fluvial landforms and deposits provide one of the most readily studied quaternary continental records and alluvial strata represent an important component in most ancient continental interior and continental margin successions moreover studies of the long term dynamics of fluvial systems and their responses to external or allogenic controls can play important roles in research concerning both global change and sequence stratigraphy as well as in studies of the dynamic interactions between tectonic activity and surface processes these themes were energized in the final decades of the twentieth century and may become increasingly important in the first decades of this millennium this review paper provides a historical perspective on the development of ideas in the fields of geomorphology quaternary geology vs sedimentary geology and then summarizes key processes that operate to produce alluvial stratigraphic records over time scales of 103 106 years of particular interest are changes in discharge regimes sediment supply and sediment storage en route from source terrains to sedimentary basins as well as changes in sea level and the concept of accommodation late quaternary stratigraphic records from the loire france mississippi usa colorado texas usa and rhine meuse the netherlands rivers are used to illustrate the influences of climate change on continental interior rivers as well as the influence of interacting climate and sea level change on continental margin systems the paper concludes with a look forward to a bright future for studies of fluvial response to climate and sea level change at present empirical field based research on fluvial response to climate and sea level change lags behind a the global change community s understanding of the magnitude and frequency of climate and sea level change b the sequence stratigraphic community s desire to interpret climate and especially sea level change as forcing mechanisms and c the modelling community s ability to generate numerical and physical models of surface processes and their stratigraphic results a major challenge for the future is to catch up which will require the development of more detailed and sophisticated quaternary stratigraphic sedimentological and geochronological frameworks in a variety of continental interior and continental margin settings there is a particular need for studies that seek to document fluvial responses to allogenic forcing over both shorter 102 103 years and longer 104 106 years time scales than has commonly been the case to date as well as in larger river systems from source to sink studies of quaternary systems in depositional basin settings are especially critical because they can provide realistic analogues for interpretation of the pre quaternary rock record

iberian margin sea surface temperature during mis 15 to 9 580 300 ka glacial suborbital variability versus interglacial stability 1 past sea surface water conditions of the western iberian margin were reconstructed based on biomarker analyses of a marine deep sea core md03 2699 from the estremadura spur north off lisbon providing new insights into orbital and suborbital scale climate variability between marine isotope stage mis 15 to mis 9 580 to 300 ka we use biomarker based proxy records such as the alkenone unsaturated index to estimate sea surface temperature sst the total alkenone concentration to reconstruct phytoplankton productivity and terrestrial biomarkers to evaluate the continental input the results extend the existing biomarker record namely the sst for the iberian margin back to the sixth climatic cycle 580 ka a general trend of stable interglacials contrasts with glacial periods and glacial inceptions which are marked by high frequency variability thus several short lived climatic coolings were identified by large sst decreases the occurrence of ice rafted detritus and high percentages of the tetraunsaturated alkenone c37 4 some of these events were extremely cold and similar in their general trends to the well known heinrich events of the last glaciation we identified eight heinrich type events between 580 and 300 ka the general deglaciation pattern detected between mis 15 and mis 9 is similar in their general trends to that characterizing the more recent climatic cycles i e marked by two coolings separated by a short warming episode which may reflect the southward northward and southward migration of the polar front

modelling the impact of regional uplift and local tectonics on fluvial terrace preservation abstract a terrace formation model terrace combined with a longitudinal river profile model fluver was used to simulate fluvial terrace formation and preservation in the northwest iberian lower mino river basin under the influence of three tectonic conditions namely regional vertical uplift local basin subsidence and localised differential uplift the simulation results were compared against mapped terrace altitudes and deposit thicknesses the best results were achieved by combining all three tectonic factors indicating that specific terrace formation is a complex interplay of regional and local tectonics the best fit regional uplift rate of 0 10 m ka 1 over the past 600 ka is higher than the 0 08 m ka 1 previously estimated for a section farther to the west which can be attributed to an increase in tectonic uplift from the nw iberian atlantic margin toward the east local relative subsidence causes sediment accumulation in the local basin and less sedimentation in the fluvial terraces on the surrounding uplifting blocks different uplift rates on both sides of the valley caused preservation of unpaired terraces which are fill terraces on one side of the valley and strath terraces on the other side usually the formation of fill or strath terraces is considered to be only climate dependent our results indicate that local tectonics can be important in the terrace formation and preservation this suggests that terrace correlations in other river systems based on deposit thicknesses only might be over simplified

large scale distributed deformation controlled topography along the western africa eurasia limit tectonic constraints in the interior of the iberian peninsula the main geomorphic features mountain ranges and basins seems to be arranged in several directions whose origin can be related to the n s plate convergence which occurred along the cantabro pyrenean border during the eocene lower miocene time span the iberian variscan basement accommodated part of this plate convergence in three e w trending crustal folds as well as in the reactivation of two left lateral nne ssw strike slip belts the rest of the convergence was assumed through the inversion of the iberian mesozoic rift to form the iberian chain this inversion gave rise to a process of oblique crustal shortening involving the development of two right lateral nw se shear zones crustal folds strike slip corridors and one inverted rift compose a tectonic mechanism of pure shear in which the shortening is solved vertically by the development of mountain ranges and related sedimentary basins this model can be expanded to nw africa up to the atlasic system where n s plate convergence seems also to be accommodated in several basement uplifts anti atlas and meseta and through the inversion of two mesozoic rifts high and middle atlas in this tectonic situation the microcontinent iberia used to be firmly attached to africa during most part of the tertiary in such a way that n s compressive stresses could be transmitted from the collision of the pyrenean boundary this tectonic scenario implies that most part of the tertiary eurasia africa convergence was not accommodated along the iberia africa interface but in the pyrenean plateboundary a broad zone of distributed deformation resulted from the transmission of compressive stresses from the collision at the pyrenean border this distributed intraplate deformation can be easily related to the topographic pattern of the africa eurasia interface at the longitude of the iberian peninsula shortening in the rif betics external zones and their related topographic features must be conversely related to more local driven mechanisms the westward displacement of the exotic alboran domain other than n s convergence the remaining nnw sse to nw se latest miocene up to present convergence is also being accommodated in this zone straddling iberia and morocco at the same time as a new ill defined plate boundary that is being developed between europe and africa

morphotectonic study of the lower sangro river valley abruzzi central italy abstract this work analyses the morphotectonic setting of the adriatic piedmont of central italy in order to outline the role of tectonics in the development of the fluvial landscape in this area particularly it focuses on the sangro river which flows in the southern abruzzi from the apennines through the piedmont to the adriatic coast the piedmont area developed in a marine environment from the pliocene to the early pleistocene resulting in the deposition of a clayey sandy sequence afterwards regional uplift processes with ne tilting led to the deposition of a regressive conglomeratic sequence as the area evolved into a continental environment this work is based on the qualitative and quantitative study of drainage patterns and on the analysis and correlation of selected morphological evidence of tectonics on fluvial terraces in order to define the role of tectonics in the geomorphological evolution of the lower sangro river valley the drainage network and its statistical azimuthal distributions are analysed the distribution and the transverse and longitudinal profiles of fluvial terraces are investigated and the morphological evidence for tectonics is then assessed river bends linear valleys beheaded and hanging valleys counterflow confluences of streams space and time correlation of these features allows us to highlight the effects of regional uplift tilting and local tectonics on drainage development following the emergence of the piedmont area middle pleistocene uplift and tilting determined a sw ne consequent and parallel drainage progressive incision shaped the sangro valley as a consequent valley local tectonics along nnw sse and wnw ese faults and fractures resulted in the incision of linear valleys beheading the previous sw ne drainage and controlled the development of a rectangular drainage network late middle pleistocene the drainage network was then rearranged by selective erosion processes maintaining a strong inheritance from of its middle pleistocene configuration

climatically controlled river terrace staircases a worldwide quaternary phenomenon a comparison of fluvial terrace sequences from around the world based on data collected as part of international geoscience programme igcp project no 449 has revealed significant patterns river terraces provide important records of uplift which is essential for their formation and of landscape evolution their cyclic formation however almost invariably seems to have been a response to climatic fluctuation sequences in the european core area of igcp 449 which has the longest and most extensive research history have been used as templates for worldwide comparison there is evidence for a global acceleration of uplift at the time of and perhaps in response to the mid pleistocene revolution when climatic fluctuation switched to 100 kyr milankovitch cycles terraces formed prior to this generally consist of wide aggradational sheets that probably each represent formation over several 41 kyr cycles subsequently river valleys became more steeply entrenched and terraces formed in response to the stronger 100 kyr climatic forcing in many cases at approximately one per cycle this paper uses the new data resource to explore differences between records in different climate zones between sequences with variable numbers of middle late pleistocene terraces and between systems in which the all important incision event has occurred in different parts of climatic cycles key records discussed include european examples from the rhine thames somme dniester dnieper don volga and aguas from asia the gediz turkey and orontes syria from north america the south platte and colorado from south africa the vaal and sundays from australia the shoalhaven and from south america the amazon paraguay and tributaries of the colorado and negro

is vegetation responsible for glacial inception during periods of muted insolation changes the marine isotope stage 11 interglacial centred at similar to 400 ka appears to be the best candidate for understanding climatic changes in the context of low insolation forcing such as that of our present interglacial direct correlation between terrestrial pollen and marine climatic indicators and ice volume proxy from deep sea core md01 2447 off northwestern iberia shows for the first time the phase relationship between southwestern european vegetation sea surface temperatures in the northeastern atlantic mid latitudes and ice volume during mis 11 a warmest 32 000 years long period and three following warm cold cycles occurred synchronously on land and ocean the end of the warmest period sees the glacial inception which coincides with the replacement of warm deciduous forest by conifer pine fir expansion in northwestern iberia and consequently with the southward migration of the tree line in high latitudes in response to declining summer insolation as weak insolation changes alone cannot account for ice growth the associated vegetation changes must now be considered as a potential major feedback mechanism for glaciation initiation during mis 11 c 2005 elsevier ltd all rights reserved

assessment of recent tectonic activity on the nw iberian atlantic margin by means of geomorphic indices and field studies of the lower mino river terraces abstract until recently nw iberia was assumed to be tectonically quiescent stable however a combination of tectono morphological analyses demonstrates that neotectonic movements do occur which are in agreement with recent findings by other workers we use a dem based tectono geomorphic approach in combination with field work to assess the presence and nature of neotectonics in the lower mino catchment in nw iberia the area is characterized by clearly developed lineaments coinciding with paleozoic and mesozoic faults and fractures and remnants of a peneplain stepping down towards the coast longitudinal river profiles show knick points where lithological control can be excluded valley shapes show that some valleys have recently been rejuvenated systematic asymmetry tendencies of river catchments indicate tilting of fault bounded blocks finally at several locations faulted terrace deposits of the mino river have been found the types of motions that can clearly be evidenced by our analyses are normal faulting and tilting of fault bounded blocks little clear evidence exists for strike slip faulting whereas reverse faulting has not been found in this study a striking morphological feature of the study area is the presence of small fault bounded basins along the course of the river mino the tectonic movements take place along inherited paleozoic and mesozoic faults which apparently act as weakness zones the reactivation of these faults under the present day stress conditions is probably the reason for the complicated pattern and style of present day tectonic motions that we find the small basins are particularly difficult to explain they could result from the interaction of partially obliquely reactivated strike slip faults step over and normal faults

external controls on quaternary fluvial incision and terrace formation at the segre river southern pyrenees abstract focusing on climatic and structural tectonic controls we aim to determine their relative importance for the pliocene to quaternary fluvial landscape evolution in the southern pyrenees foreland we investigate the segre river which is one of the major streams of the southern pyrenees that drains the elevated chain towards the ebro foreland basin along its course the segre river has a flight of fluvial cut and fill and strath type terraces preserved that have been mapped based on dem s and geomorphological fieldwork this paper presents the first results of our study and reports on the segre terrace staircase which is characterized by seven major quaternary terrace levels with elevations up to more than 110 m above the modern floodplain at the upper and middle reaches the semi parallel terraces of the segre river occasionally show anomalies featuring extensive gravel thickness and deformation caused by faulting folding and local subsidence the longitudinal correlations of terrace levels reveal increased vertical terrace spacing in the foreland which could originate from enhanced fluvial erosion after the mid pleistocene climate transition in combination with base level lowering controlled by the progressive downcutting of the catalan coastal range since the ebro basin opening late miocene the catalan coastal range which borders the ebro foreland basin to the mediterranean sea was progressively cut down and the exorheic drainage system gradually adjusted to sea level the segre longitudinal terrace profiles and the ebro gorge morphology at the catalan coastal range indicate a base level of about 200 m s l at the beginning of pleistocene terrace formation which implies that the catalan coastal range might have functioned as a local base level upstream of the sea outlet presumably until the late pleistocene alternatively a yet unknown tectonic process might have caused base level lowering and the preservation of terrace staircases at the ebro drainage system

cenozoic tectonic activity in a variscan basement evidence from geomorphological markers and structural mapping nw iberian massif abstract the nw iberian massif is part of an ancient basement that has been considered a seismically stable area with no outstanding cenozoic tectonics however recent seismic activity revealed the need for better knowledge of the cenozoic structures in the area because of the lack of mesozoic deposits and the scarcity of cenozoic sediments as well as the intense deformation of the pre mesozoic variscan basement it is difficult to study the cenozoic tectonic structures in this work the combination of detailed structural mapping and study of geomorphological markers in the variscan basement has allowed recognition of cenozoic tectonic structures kinematics and processes that otherwise would not have been identified the identified structures have been gathered into three groups a ne sw trending strike slip faults mainly sinistral b nnw vergent thrusts that uplift the caurel mountains and galaico leoneses mountains and c e w and ene wsw thrusts that uplift the ancares mountains in a pop up structure the structures cut the pre cenozoic erosion surface and affect the drainage network that shows patterns characteristic of tectonic activity the three groups of structures define sectors with different relief showing a strong link between geomorphological elements and tectonic structures the intense drainage reorganisations observed in the area and the deformation of miocene pliocene deposits point out to a significant late miocene tectonic activity in the region thus the cenozoic tectonic activity in the northwest of the iberian peninsula takes place during an extensive period of time which started with the episodes of compression in the cantabrian margin and it is identified nowadays by the recent seismic activity recorded in the north western iberian peninsula 1995 and 1997 lugo events the seismicity is related to the cenozoic structures identified in the area which move under the present se nw horizontal maximum compression and coincide with the proposed seismogenic faults

geomorphic response of coastal streams to low intermediate and high rates of uplift medocino triple junction region northern california analysis of three dimensional morphological properties of 24 coastal drainage basins that have evolved in areas of low 3 m 1 000 yr rates of uplift near the mendocino triple junction mtj coastal northern california identified channel gradients as the best indicator of tectonism in the landscape lower order tributaries best reflect tectonically controlled differences the largest streams examined of third order are able to adjust to most base level change and maintain their profile form whereas lower order streams farther upstream tend to accumulate the effects of net base level fall and have steepest profiles in the areas of highest uplift rates variations in steepness of first order channel gradients indicate that 1 high uplift rates in the wake of the mtj have existed for at least 73 000 yr and 2 differential tilt of the region to the north and south of the current locus of highest uplift rate is occurring in association with regional uplift although first order streams are excellent indicators of areas of both high uplift rates and regional differential tilting they are less useful in distinguishing between areas of low and intermediate uplift rate analysis of the longitudinal profile of the main trunk stream of ten of the 24 drainage basins using the stream gradient index was more useful to categorize broadly the uplift rates and to distinguish between streams in low and intermediate uplift rate areas although the hypotheses tested herein do not identify the exact mechanism off uplift in the mtj region they do indicate that the nature of deformation is most likely regional tilt rather than crustal shortening with localized compressional folding and thrust faulting they also indicate that geomorphic responses trail in the wake of the uplift rate response caused by development of a slab window beneath the north american plate 1 maximum uplift rates occur 9 km south of the northern boundary of the slab window 2 maximum mean first order channel gradient occurs 16 km south of the northern edge of the slab window and 3 maximum drainage basin relief occurs 20 km south of the northern edge of the slab window associated lag times between passage of the southern edge of the subducted gorda plate slab and geomorphic responses are 160 000 yr for maximum uplift rates 290 000 yr for maximum channel gradients and 370 000 yr for maximum relief