late quaternary river incision rates and rock uplift pattern of the eastern qilian shan mountain china abstract the uplift rate and pattern of the qilian shan mountain which lies in the northeast margin of the tibetan plateau are key to understanding the dynamics of crustal deformation in the northeastern tibetan plateau in this work late quaternary terraces in seven river valley sections in the eastern qilian shan mountain are studied to determine terrace abandonment ages by osl optical simulating luminescence and terrace heights by gps global positioning system surveys river incision rates since 76 ka bp are calculated ranging from 0 37 mm a to 1 49 mm a distribution of river incision rates shows that higher river incision rates 0 85 1 49 mm a are located at the rivers upstream reaches where mean mountain elevation is 4000 m and relatively lower incision rates 0 32 0 62 mm a are located at the mountain front where the mean mountain elevation is

seismic images of continental lithosphere seismic reflection profiles in usa and west germany over thirty years ago showed strong reflections from the lower crust but technical advances through the 1970s were needed for the method to image the continental lithosphere the british institutions reflection profiling syndicate birps found advantage in working offshore and has obtained over 12 000 km of profiles around britain during the past decade giving the densest regional coverage anywhere reflections are observed from strata in sedimentary basins from low angle faults that can be followed from surface to mid crust from a laterally variable reflective zone in the lower crust from the moho and from fault like features in the upper mantle there is evidence around britain that faults bounding sedimentary basins are older structures which have been reactivated it is argued that lower crustal reflectivity around britain is mainly due to anastomosing ductile shears which accommodate extension in the lower crust commensurate with extension in the upper crust by faulting and block rotation there is also evidence of reflections preserved from older orogenic features so that reflections interpreted as extensional ductile shears in the lower crust may also derive from older features that have been reactivated most reflections in the lower crust arise from rocks that have been highly strained evidence of lateral variability in the reflective character of the moho suggests that the moho has been actively involved in the structural evolution of the lithosphere upper mantle reflections are interpreted as shear zones which transfer crustal deformation through the lithosphere

oxygen isotope calibration of the onset of ice rafting and history of glaciation in the north atlantic region we report here that dsdp site 552a cored with the hydraulic piston corer on the west flank of rockall bank recovered an undisturbed sequence of alternating white deep sea carbonate oozes and dark coloured layers that are rich in glacial debris oxygen isotope analysis of the sequence together with detailed nannofossil and palaeomagnetic stratigraphy shows that the first major horizon of ice rafting occurred at about 2 4 myr and was preceded by a minor pulse of ice rafting at about 2 5 myr the carbon isotope record shows that the site has been bathed by a water mass of similar characteristics to present day north atlantic deep water at least since 3 5 myr

late cenozoic extension in sw bulgaria a synthesis abstract southwest bulgaria forms the northern margin of the aegean extensional province since the early pliocene c 4 ma this region has accommodated southward or sse extension at several millimetres per year superimposed on c 400 m of post early pliocene regional uplift this sense of deformation superseded earlier extension oriented ene wsw which is estimated to have begun in the early late miocene c 10 9 ma and lasted until c 4 ma the regional topography is dominated by nnw sse striking grabens and normal fault escarpments relics from this time normal faults that are now active cut across these older structures although in some localities normal faults that were oriented obliquely to the earlier extension have remained active also oblique to the modern extension sense it is suggested that this present phase of extension relates to the modern sense of deformation throughout the aegean region and to the modern geometry of the north anatolian fault zone nafz which is independently inferred to have existed since c 4 ma the earlier ene wsw extension is inferred to have involved two phases the first predating the nafz and the second synkinematic with its initial phase of slip during c 7 4 ma when its geometry and the overall sense of deformation in the aegean region were different from at present some previous studies have inferred that sw bulgaria experienced large scale extension on low angle normal faults in the mid miocene or earlier however the limited evidence in support of this view is open to other interpretations and after due consideration can be discounted

dating of sirius group tillites in the antarctic dry valleys with cosmogenic3he and21ne we measured in situ produced cosmogenic3he and21ne in boulder and bedrock surface samples in and near sirius group tillites from two localities in southern victoria land antarctica pyroxene quantitatively retains cosmogenic3he for millions of years the deposit at mt fleming has a minimum exposure age of 6 5 ma while 6 ma is a probable minimum age for the table mountain tillite these lower limits not taking into account erosion of the sampled surfaces are based on the samples with the highest concentrations of cosmogenic noble gases and currently accepted production rates since the plagioclase bearing mt fleming samples almost certainly lost part of their cosmogenic ne the minimum exposure age at this location is presumably even 50 higher than the stated value the concentrations of cosmogenic ne in our samples constrain uplift rates of the transantarctic mountains to 170 m ma these data contradict the hypothesis of a collapse of the east antarctic ice sheet in the pliocene coupled with high uplift rates and support the model of a stable ice sheet since the middle miocene

cenozoic uplift of southwest england the uplift history of southwest england is inferred using a composite dataset including marine and fluvial terraces and karstic data the estimated post mid pliocene uplift increases eastward from 130 m in west cornwall and 135 m in south devon to 150 m in the hampshire basin the post early pleistocene uplift likewise increases eastward from 55 m in west cornwall to 60 m in south devon and 80 m in hampshire landscape and thermochronological evidence also indicates eocene uplift caused by the british tertiary igneous province magmatism this component tapers eastward from 300 m in west cornwall to 50 m in south devon with subsidence in east devon this uplift accompanied magmatic underplating the mafic layer added to the basal crust thins eastward from 6 km in west cornwall to 2 km in south devon evidently tapering to zero farther east the laterally variable crustal properties caused by this variation in underplating have affected the post mid pliocene uplift the study region is thus intermediate in terms of crustal strength and landscape evolution between central southern england with no underplating and ireland where 10 km thick underplating has resulted in extreme late cenozoic landscape stability the eocene mantle plume related uplift is distinct from the post mid pliocene phase which the modelling indicates has been driven by surface processes and thus by climate change copyright 2010 john wiley sons ltd

river terrace systems in north west europe an archive of environmental change uplift and early human occupation abstract staircases of large scale aggradational river terraces are a notable feature of many valleys in the temperate lattitudes particularly in areas beyond the reach of the erosive activities of pleistocene ice sheets it is now recognized that the cyclic fluctuations of climate during the quaternary have driven the generation of terraces through the direct and indirect influence of both temperature and precipitation on fluviatile activity where fossiliferous deposits are preserved within terrace sequences it is often possible to date these and to correlate them with the oceanic record thus providing an important framework for the evidence of environmental change on land middle and late pleistocene terraces in different areas can commonly be seen to have formed in synchrony with glacial interglacial cycles or with longer periodicity megacycles climatic forcing alone is insufficient to cause terraces to form however uplift is also necessary so that terrace sequences can provide a useful record of crustal movement in northwest europe where some of the best known studies of river terrace sequences have been carried out the fluviatile deposits are also an important repository for palaeolithic artefacts from which a record of early human occupation can be reconstructed

the pleistocene of northern france a table of stratigraphic correlation has been established between the different provinces of the quaternary paleogeographic regions of northern france extending from brittany to alsace and from the welshbelgium basin to the paris basin initially based on loess and slope deposits in the framework of the aeolian periglacial zone of northwestern europe paepe and sornme 1970 lautridouand sornme 1974 these correlations not only include data from brittany but also provide sequences from achenheim alsace to enable correlation with more continental european areas

chronology of neogene and quaternary uplift and magmatism in the caucasus constraints from k ar dating of volcanism in armenia abstract the greater caucasus is one of earth s highest actively uplifting mountain ranges the adjoining caspian sea basin contains a substantial proportion of its hydrocarbon reserves like other parts of the former soviet union the neogene and quaternary chronology of these important regions has not previously been well defined it has thus been impossible to obtain reliable estimates for rates of processes such as uplift of the caucasus and sedimentation in the caspian sea previous studies have established the relative timings of events in the region using correlation schemes between volcanism glaciations and the stratigraphy of the caspian basin however a range of absolute chronologies has previously been proposed for these sediments and igneous rocks based mainly on different interpretations of their magnetostratigraphic records by k ar dating we determine the ages of volcanism at three localities in armenia as 1 1 0 8 and 0 8 ma using these data and other evidence we propose a revision to the chronology of this region in which a distinctive brief interval of normal magnetic polarity in the local sedimentary and volcanic magnetostratigraphic records is matched to the cobb mountain event in the global record rather than the olduvai event or an earlier subchron as had previously been thought we thus interpret a 1 5 ma timing for the start of volcanism in the lesser caucasus and also suggest a 1 2 ma timing for the late akchagyl transgression of the caspian sea a key event in the regional stratigraphy when this water body reached its greatest extent we tentatively correlate this transgression with the melting event following glaciation during stage 36 of the oxygen isotope timescale which was thus the first time during the pleistocene when eastern europe was covered by a lowland ice sheet time averaged since 1 ma the flanks of the eastern greater caucasus mountains are shown to have uplifted at 0 6 mm a 1 and the lesser caucasus at 0 3 mm a 1 we show that the rate and spatial scale of this uplift are too great to be the result of plate convergence and suggest instead that this uplift is caused by crustal thickening due to inward lower crustal flow to beneath these mountain ranges at the start of magmatism in both the greater and lesser caucasus the estimated crustal thickness was 45 km we thus suggest that this magmatism has been caused by heating of the mantle lithosphere due to earlier crustal thickening the temperature rise required to initiate magmatism being the same in both cases

a re examination of the evidence for a plio pleistocene marine transgression on the chiltern hills iii deposits a petrological re examination of the deposits that wooldridge and linton used as evidence for a plio pleistocene marine transgression on the chiltern hills indicates that many are fluvial and some have been reworked in a periglacial climate however those from little heath and rothamsted hertfordshire and lane end buckinghamshire are confirmed as marine and plio pleistocene subsidence during the pleistocene is suggested by the northeasterly decline in height of the few truly marine deposits

preservation of miocene glacier ice in east antarctica antarctic climate during the pliocene has been the subject of considerable debate one view holds that during part of the pliocene east antarctica was largely free of glacier ice and that vegetation survived on the coastal mountains1a 4 an alternative viewpoint argues for the development of a stable polar ice sheet by the middle miocene which has persisted since then5a 10 here we report the discovery of buried glacier ice in beacon valley east antarctica which appears to have survived for at least 8 1 million years we have dated the ice by 40ar 39ar analysis of volcanic ash in the thin overlying glacial till which we argue has undergone little if any reworking isotope and crystal fabric analyses of the ice show that it was derived from an ice sheet we suggest that stable polar conditions must have persisted in this region for at least 8 1 million years for this ice to have avoided sublimation

mathematical modeling of graded river profiles numerical modeling of the longitudinal profiles of rivers at grade is accomplished using the basic equations of open channel flow sediment transport equations and empirical relations for downstream variation in flow discharge sediment discharge sediment caliber and channel width only in some cases are the computed stream profiles fit exactly by any one of the commonly supported mathematical function analogs to graded profile form exponential logarithmic or power function but in most cases any of these functions can provide a fit with a degree of error smaller than would be noted in treating field data profiles dominated by spatial change in fluid and sediment discharge are distinctly power functions while profiles dominated by sediment size reduction are not necessarily exponential in form other important controls on profile shape are the degree of downstream width change in response to increasing discharge and the general range of sediment size a dynamic model of a river s approach to grade

evidence for dynamic coupling of surface processes with isostatic compensation in the lower crust during active extension of western turkey western turkey in the eastern part of the aegean region is extending slowly with extension no faster than 0 5 mm yr 1 across any individual active normal fault up to 15 km of southward extension has occurred in the most active 100 km wide part of this region since 15 ma indicating a typical strain rate of 3 10 16 s 1 rivers carry a sediment flux of 4 106 m3 yr 1 westward to the aegean sea coast with offshore sedimentation at 1 mm yr 1 sediment loading causes coastal areas to subside much faster than would be expected from the extension alone most of this sediment is derived from regional erosion of inland areas to the east at a typical rate of 0 1 mm yr 1 this erosion being isostatically compensated by uplift it is suggested that the lower crustal material displaced by sediment loading near the coast flows east to isostatically compensate the erosion the average eastward velocity of this lower crustal channel flow beneath the aegean coast is estimated as 1 mm yr 1 the maximum velocity is 2 mm yr 1 this case study thus indicates the general point that isostatically compensated erosion and lower crustal channel flow can affect the evolution of sedimentary basins that are surrounded by eroding landmasses factors that are often neglected

crustal structure of the central and southern north sea from birps deep seismic reflection profiling through the generous gift of shiptime on m v mobil search in june 1987 birps british institutions reflection profiling syndicate was able to acquire nearly 1500 km of deep seismic profiles recorded to 16s twt in a regional survey across the central and southern north sea reflective lower crust beneath the southern north sea basin gives way laterally to a zone of mid crustal reflections within the london brabant platform these mid crustal reflectors are interpreted as due to crustal shearing although whether related to stretching during basin formation or to some earlier event remains enigmatic sub crustal sw dipping reflections are observed at the edge of the london brabant platform across the mid north sea high n s profiles show distinctive patterns of lower crustal reflectivity that indicate lateral variability in structure and character on a scale of 30 50 km these are interpreted as crustal units relating to the iapetus suture developed during the caledonian orogeny they may have been modified however during carboniferous basin development or subsequently the absence of any distinctive sub crustal reflectors associated with the iapetus suture where a caledonian subduction zone should have existed tends to suggest that sub crustal reflections observed elsewhere around britian are not subduction related but are more likely to be from younger faults or shear zones relating to lithosphere extension and basin formation onshore wide angle recording in northern england of the marine seismic source produced good quality data the high resolution obtained has revealed details of mid crust pcp and moho pmp reflections from around 18 and 30 km depth respectively not observed before in this area both reflectors show events of laterally variable reflectivity that appear as bands of discontinuous reflection segments

the 1984 july 19 north wales earthquake a lower crustal continental event indicating brittle behaviour at an unusual depth summary attention has recently been focused on the structure and composition of the lower crust in continental areas it is generally believed that except in special circumstances ductile behaviour below mid crustal depths precludes the brittle processes that cause earthquakes the 1984 july 19 earthquake in north wales occurred at the unexpected depth of 23 km we report here the location of the larger aftershocks and the relocation of the main shock with respect to one of them the lower crustal depths of the events are confirmed by tests with a wide range of models the occurrence of earthquakes at these depths may be related to low heat flow in the region

the sedimentology and palaeoecology of the westleton member of the norwich crag formation early pleistocene at thorington suffolk england extensive sections in the thorington gravel quarry complex in eastern suffolk include the most complete record to date of sedimentary environments of the westleton beds member of the norwich crag formation new palaeoecological and palaeomagnetic evidence is presented which confirms that the member was deposited at or near a gravelly shoreline of the crag sea as sea level fluctuated during a climatic ameloriation within or at the end of the baventian pre pastonian a stage tiglian c4c substage

a simple heat flow quality function and appraisal of heat flow measurements and heat flow estimates from the uk geothermal catalogue abstract a comprehensive database of temperature heat flow thermal conductivity and geochemistry is the basis of geothermal modelling the latest revision 1987 of the uk geothermal catalogue ukgc contains over 2600 temperatures at over 1150 sites and over 200 observations of heat flow about 93 of the temperature data are from depths less than 2000 m and about 50 are bottom hole temperatures bht heat flow density distribution models can be expanded to include estimates of heat flow derived from bht and thermal conductivity data contained in the ukgc a simple quantitative assessment of the quality of individual heat flow measurements has been devised based on the type and frequency of temperature and conductivity measurements and the borehole depth the dimensionless quality function hfq has been defined so that for a heat flow borehole with two equilibrium temperature measurements made across an interval with a mean depth of 1 km or greater with complementary thermal conductivity determinations made at intervals of 1 m across this zone the heat flow quality function is 1 0 over 50 of the uk heat flow dataset has a hfq function less than 0 10 the 4 highest quality observations have values above 1 0 the same function can be used to assess the quality of estimates of heat flow by assigning quality functions to various types of temperature and thermal conductivity observation schemes appraisal of the uk heat flow dataset indicates that some of the observational data have a similar quality rating to estimates of heat flow derived from convolution of temperature and thermal conductivity data for deep boreholes within the catalogue in eastern england the heat flow density pattern is significantly modified by incorporation of estimates of heat flow from deep boreholes which have hfq values comparable with early heat flow measurements made in this region

the upper pleistocene deposits at cassington near oxford england for much of the middle and all of the upper pleistocene the upper thames valley has remained outside the limit of ice advance the main agents of landform evolution have been the river thames and its tributaries which have cut down episodically and in so doing have abandoned a series of river terraces this study reports the findings of an investigation into exposures in the deposits underlying the floodplain terrace at cassington near oxford england the sequence exposed reveals a stratigraphy of basal predominantly fine grained lithofacies overlain by coarser gravel lithofacies the fluvial architecture of these deposits indicates a major change in fluvial style from a low energy meandering to a high energy braided channel system the flora and fauna from the lower fine grained lithofacies display a marked change from temperate at the base to colder conditions towards the top indicating a close association between deteriorating climate and changing fluvial depositional style amino acid and luminescence geochronology from the basal fine grained lithofacies suggest correlation with oxygen isotope stage 5 and hence it is argued that the major environmental change recorded at the site relates to the oxygen isotope stage 5 4 transition deposition of much of the overlying gravel sequence probably occurred during oxygen isotope stage 4 suggesting that the latter half of the devensian may be less significant in terms of fluvial landscape evolution in the upper thames valley than was believed previously c 1998 john wiley sons ltd

accelerated uplift resulting from anglian glacioisostatic rebound in the middle thames valley uk evidence from the river terrace record abstract a relatively simple analysis of the terraces of the middle thames valley reveals a complex sequence of responses to late anglian late middle pleistocene drainage disruption a decrease in the amounts of vertical incision separating the later post anglian terraces strongly suggests a major change in the rate of incision in the middle thames area in the post anglian a late anglian and early post anglian incision rate of 1 45 m ka 1 was quickly replaced by incision at a rate of 0 089 m ka 1 in the later post anglian period the lower incision rate of the later post anglian compares favourably with previous estimates of regional uplift two plausible explanations for the enhanced incision in the late anglian and early post anglian are recognized one related to ponding of the river by anglian ice and the other to glacio isostatic rebound in the latter case the mismatch between expected and actual heights of late anglian deposits would suggest glacio isostatic uplift of the order of 22 25 m

thames river sediments of the british early and middle pleistocene abstract the thames drainage system contains the most complete record of fluvial sediments in the british quaternary the kesgrave sands and gravels form the main body of this sediment having been deposited over an interval that spans the later part of the early pleistocene and most of the middle pleistocene conventional stages pre pastonian a through to early anglian ca 1 2 ma this deposit provides a stratigraphic context for related bio morpho and pedostratigraphic evidence and for the recognition of pre anglian pre oi stage 12 upland glaciation in the welsh mountains and intense periglaciation in lowland england it also facilitates correlation with the stratigraphy of northern europe and the global pattern of orbitally forced climatic change this paper describes the first catchment wide correlation of thames river sediments and proposes a formal redefinition of the lithostratigraphic units concerned the scheme outlined here is based on two lithologically distinctive formations defined at type areas reflecting significant changes in catchment dimensions the earlier sudbury formation was formed when the thames catchment extended into wales and drained northwards across east anglia the later colchester formation was formed after the upper catchment had been reduced in extent to that of the present river but continued to flow across east anglia the whole sediment body is now named the kesgrave group

quaternary glaciations of northern europe this paper presents the outcome of a workshop held in berlin in february 2009 concerned with current research on the glacial history of northern europe including the british isles the methodologies presently used to resolve this topic are outlined particular attention is given to new analytical methods deriving from high resolution remote imaging of glacial terrain both on land and on the sea bed key new stratigraphic sections higher resolution results from conventional geochronological methods like radiocarbon and more recently developed technologies such as luminescence and cosmogenic radionuclide dating the relationships between the results derived from these two methods are discussed in further detail along with possible explanations for these differences an outline of a most likely glacial history of the scandinavian and british and irish ice sheets is presented along with possible links to global climate change as represented by the marine isotope mis record tentative evidence for glaciation is identified in mis 22 16 12 10 8 6 4 and 2 and correlations of phases within the last glaciation are also explored for both the scandinavian and british and irish ice sheets the results show that the character and extent of glaciation in different parts of the region are not synchronous and much more geochronological work is required before regional correlations can be established with confidence

heat flow and thermal structure of the lithosphere across the baltic shield and northern tornquist zone abstract terrestrial heat flow data from archean and proterozoic provinces of the baltic shield its southwestern margin and the tectonic transition to the younger tectonic units of central europe northern segment of the european geotraverse are compiled and examined for local and regional variations a 2 d numerical lithospheric temperature and heat flux model is presented covering 1800 km of the deep seismic fennolora profile across the baltic shield and 500 km of eugeno s northern eugemi seismic lines across the northern tornquist zone and the danish and north german basins thermal lithosphere defined as the outer layer with relatively low temperatures t c in which heat transfer is dominantly by conduction is found to vary markedly in thickness from 85 110 km beneath basins and tornquist zone to about 150 km in central shield areas and 200 250 km in areas of low heat flow along the northern shield profile these results are in very good agreement with seismological information from surface wave dispersion analysis and the refraction wide angle seismic interpretation of fennolora data the combined thermal and seismologic evidence indicates that the uppermost mantle region stratified in seismic velocity is restricted to the upper relatively cold thermal layer which is interpreted to constitute shield lithosphere local and to some extent regional variations in surface heat flow are found to be closely related to variations in near surface radiogenic heat production for the southern baltic shield a heat flow heat production relationship of q 0 32 8 7 6 h 0 is derived regional increase in heat flow from northern and central shield provinces to the shield margin and the tornquist zone is interpreted to be related partly to differences in upper crustal heat generation partly and in southernmost areas mainly to an increased heat flux from the upper mantle upper mantle heat flux is estimated at 20 25 mw m 2 along the northern and central shield transect increasing to 30 40 mw m 2 beneath the shield margin basins and tornquist zone lithospheric thickness variations in this region of northern europe are found to be closely associated with variations in heat flux from the uppermost mantle and perhaps to a large extent controlled by geodynamically determined lateral differences in upper mantle heat flux earthquake focal depth data and information on crustal strength show baltic shield seismicity to be limited generally to the upper 20 25 km brittle part of the crust at temperatures less than 300 400 c maximum source depth of magnetic anomalies at temperatures near 600 c is in the deepest part of the crust near the crust mantle boundary in the southern region about 25 km depth along the tornquist zone and about 35 40 km in southern shield areas and in the uppermost mantle 60 70 km depth in the northern shield areas some petrologic implications are discussed the present deep crust is supposed to be at lower temperature pressure conditions than at early stages of formation however also the present deepest parts of the shield crust 35 40 km are within the stability field of eclogites the general absence of significant gravity anomalies in areas of marked crustal thickness variations indicate high density eclogites to be present in significant amounts in the deep shield crust

the age and nature of the basement of southern britain evidence from sr and pb isotopes in granites the isotopic study of granitic intrusions in southern britain provides an indication of the age and geochemical nature of the south british basement which is otherwise generally obscured from observation by sedimentary cover this paper reports pb isotopic compositions of feldspars in granites from sw england lundy mountsorrel and shap in addition to age and initial 87 sr 86 sr data on two of the granites a review of published rb sr age and isotope data for southern britain and consideration of the new pb data using the plumbotectonics model of doe zartman 1979 indicate that the basement to southern britain has an age of 800 ma with an upper limit of 1200 ma the granites studied in this work have substantial components of crustally derived sr and pb

early and middle pleistocene vegetation history of the medoc region southwest france pleistocene deposits together with their pollen plant macrofossil foraminiferal dinoflagellate and coleopteran remains from five sites along the atlantic coast of the medoc peninsula are described and discussed sediments making up the negade formation are shown to have been laid down under either estuarine or lagoonal conditions when closed quercus pinus tsuga canadensis regional woodland existed comparison with plant records from the netherlands indicates that these deposits are most likely attributable to either the early pleistocene bavel interglacial marine oxygen isotope stage mis 31 or an interglacial of the waalian mis 37 49 or tiglian mis 63 79 in addition clays assigned to the argiles du gurp sensu stricto were similarly deposited in either an estuary or lagoon which subsequently was cut off from the sea a freshwater lake with vegetation dominated by azolla filiculoides then developed this was succeeded by reedswamp and an organic mud termed lignite in the corresponding french stratigraphical records formed regional quercus abies woodland was replaced by one with pinus dominant and pterocarya a minor component comparison with plant records from france and other parts of europe suggest that the clays and organic mud might be correlated with the holsteinian praclaux interglacial mis 11c copyright 2003 john wiley sons ltd

topographic controls on evolution of shallow landslides in pastoral wairarapa new zealand 1979 2003 abstract this study aims to identify topographic influence on shallow landslides and their evolution during 1979 2003 in the pastoral lower north island new zealand landslide affected sites were mapped from aerial photographs and an aster satellite image the two landslide maps were overlaid in a geographic information system arcgis to detect the changes that have taken place in landslide affected areas the change map and the landslide distribution maps were overlaid with three topographic layers of slope gradient slope position and slope aspect that had been derived from a digital elevation model in arcgis the overlay analysis revealed that landslides affected area increased from 23 75 ha in 1979 to 110 97 ha in 2003 the distribution of landslide affected sites is inversely correlated with slope gradient but positively with slope position northern aspects are the most vulnerable to landsliding containing about 78 of the total affected sites moderate slope gradients suffered the most severe landsliding in the lower to middle slopes the overall magnitude and frequency of landsliding is also related to northern and eastern octants on the moderate slope gradients in the low to moderate slope positions although the same topographic setting is conducive to landsliding in both 1979 and 2003 the rate of landsliding varies with topographic setting hence topography is critical not only to landsliding but also to the evolution of sites already affected by landslides such an understanding over large spatial scales is possible only with the use of multitemporal remote sensing data and gis that are able to speed up data collection and analysis

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

dependence of active normal fault dips on lower crustal flow regimes two key questions are raised by the presence in the basin and range province of subhorizontal normal faults which were active in and around the miocene first how did they develop when their existence seems to be precluded by elementary rock mechanics arguments second if they did slip in the recent geological past why do normal faults now active in the brittle upper crust have steeper dips both in the western usa and elsewhere one may now answer both questions by considering the stress field in regions where the isostatic response during extension involves horizontal flow in the plastic lower crust this stress tensor will have inclined principal axes making it possible for normal faults to form with either very steep or subhorizontal dips depending on the sense of flow this can be controlled by environmental conditions which influence rates of hanging wall sedimentation and footwall erosion and thus determine lateral variations in lithostatic pressure in the lower crust regional scale lateral variations in the geothermal gradient caused by subduction can also influence lower crustal flow regimes in adjacent zones of continental extension enabling extension to occur on low angle normal faults dipping away from the active continental margin

the mid pleistocene climate transition onset of 100 ka cycle lags ice volume build up by 280 ka the mid pleistocene climate transition mpt is the complex climatic change which brought the late pleistocene ice ages we explore the mpt in the time and frequency domains by new methods of time series analysis high resolution oxygen isotope records reveal that the ice volume related increase in 18o mean amplitude 0 29 0 05 1 transition midpoint 922 12 ka duration 40 9 ka significantly preceded the abrupt increase in the amplitude of the 100 ka cycle at 641 9 ka this finding can be quantitatively simulated using a simple ice bedrock model in which due to the additional ice the calving threshold is exceeded the simulated calving events prior to 650 ka are separated by 77 ka whereas after 650 ka they occur pseudo periodically with a mean period of nearly 100 ka the cause for the delay of the 100 ka calving cycle was not a slow bedrock relaxation rather the coincidental combination of insolation existing ice mass and bedrock depression

an analysis of cotswold topography insights into the landscape response to denudational isostasy we have used the nextmap britain digital terrain model dtm to determine the lithospheric response to erosional unloading and the contribution of tectonics in the form of elastic plate flexure to the cotswold scarp and vale landscape the calculations take into account lithology variations and along strike changes in escarpment retreat we show that flexural rock uplift as a result of erosional unloading varies spatially and may contribute up to 50 of the relief in the cotswold region this is supported by morphometric analysis of concavity and steepness for 66 longitudinal river profiles that drain the scarp and dip slope of the escarpment viscoelastic plate models suggest that the uplift is initially rapid up to 8 m ka 1 and essentially complete within 50 ka these initial rates are compatible with an early post anglian incision rate inferred from the thames terraces the staircase terrace pattern suggests however that there have been a number of denudational isostatic events each associated with a climate cycle finally the analysis reveals an inherited proto landscape that has a subdued relief when compared with the modern dtm such a relief is consistent with an early extension of the river thames through the vale of moreton to the north of the present day cotswold hills

pre weichselian quaternary glaciations of the british isles the netherlands norway and adjacent marine areas south of 68 n implications for long term ice sheet development in northern europe within this paper we review the pre weichselian glacial history of northern europe focussing on evidence from the british isles netherlands norway and adjacent marine areas that record the activity of the british bis and scandinavian sis ice sheets the objective of the paper is to examine the long term evolution of the two ice sheets in order to determine their level of synchronicity and their relationship to the plio pleistocene record of northern hemisphere glaciation geological evidence demonstrates striking long term similarities between the behaviour of the bis and sis with a step wise intensification in the glacial signal 1 first ice rafted debris ird input onto the continental margin at ca 2 7 2 6 ma and restricted glaciation prior to ca 1 1 ma 2 initiation of more lowland style glaciation from 1 1 ma 3 repeated shelf edge glaciations from 0 45 ma these steps coincide with a major intensification of the northern hemisphere climate signal at the beginning of the quaternary and the mid pleistocene transition temporal and spatial variabilities in the behaviour of different sectors of the bis and sis appear to reflect regional scale geographic latitude elevation climatic moisture temperature and glaciological deformable beds controls that modulate the build up of ice volume in the main ice accumulation areas relative to global climate forcing and its subsequent lateral expansion 2010 nerc

flexural rotation of normal faults a conceptual model is proposed for the generation of low angle normal faults in metamorphic core complexes the model is based on three assumptions 1 the isostatic response to normal fault motion is of regional extent 2 when a fault segment is significantly rotated from the optimum angle of slip relative to the crustal stress field it is replaced by a new planar fault oriented in the optimum direction and 3 the fault cuts the entire upper crust and fault motion always nucleates in the same region at the base of the upper crust the stress field is considered to be uniform through the crust and the regional isostatic response of the crust to loads is computed using the thin plate flexure approximations active low angle normal faults are difficult to reconcile with rock mechanics theories earthquake focal mechanism studies and geochronologic results indicating rapid cooling of core complex rocks the model does not require active fault slip on low angle faults the flexural response to normal faulting is shown to be significantly affected by anelastic behavior of the crust and by loading due to sedimentation the anelastic response to large bending stresses results in significant reduction in the effective elastic rigidity of the upper crust this can explain the observed short wavelength of topographic response to normal fault loads the model results in 1 a nearly flat lying abandoned normal fault or detachment below slices of upper plate rocks and sedimentary infill 2 a strong contrast in metamorphic grade across the abandoned detachment 3 rapid movement of lower plate rocks from midcrustal depths to shallower depths these results are qualitatively in agreement with geologic observations for core complexes

a global perspective of the european chronostratigraphy for the past 650 ka abstract characteristic global climatic events are employed to interpret the regional land based european stratigraphy the chinese loess record shows well expressed continuous and reliably dated climatic signals of worldwide significance which are well correlated with the marine oxygen isotope stratigraphy the sequence in the surroundings of ferdinandow in poland plays a key role in the correlation of the european stratigraphy with the loess record and the oxygen isotope record in particular the complex but well expressed ferdinandowian interglacial is a key marker because it shows striking similarities with the most pronounced soil complex of the last 700 ka years of the chinese loess sequence s5 and by correlation oxygen isotope stages ois 13 15 it follows that the holsteinian interglacial corresponds with the s4 soil and ois 11 this appears to be confirmed by sequences deposited in the craters of the central massif france problems of regional stratigraphical correlation in europe persist but is suggested that a general framework is now established

post gondwana geomorphic evolution of southwestern africa implications for the controls on landscape development from observations and numerical experiments the relationship between morphology and surficial geology is used to quantify the denudation that has occurred across southwestern africa since the fragmentation of gondwana during the early mesozoic two main points emerge significant denudation of the order of kilometers is widespread except in the kalahari region of the continental interior the denudation is systematically distributed so that the continental exterior catchment draining directly to the cape basin is denuded to a greater depth than the interior catchment inland of the great escarpment the analysis also implies that the majority of the denudation occurred before the beginning of the cenozoic for both the exterior and interior catchments existing models of landscape development are reviewed and implications of the denudation chronology are incorporated into a revised conceptual model this revision implies that the primary effect of rifting on the subsequent landscape evolution is that it generates two distinct drainage regimes a marginal upwarp or rift flank uplift separates rejuvenated rivers that drain into the subsiding rift from rivers in the continental interior that are deflected but not rejuvenated the two catchments evolve independently unless they are integrated by breaching of the marginal upwarp if this occurs the exterior baselevel is communicated to the interior catchment that is denuded accordingly denudation rates generally decrease as the margin evolves and this decrease is reinforced by the exposure of substrate that is resistant to denudation and or a change to a more arid climate the observations do not reveal a particular style of smaller scale landscape evolution such as escarpment retreat that is responsible for the differential denudation across the region it is proposed that numerical model experiments which reflect the observational insights at the large scale may identify the smaller scale controls on escarpment development if the model and natural systems are analogous four numerical experiments are presented in which the roles of antecedent topography resistant substrate climate change and lowering the baselevel of the interior catchment are investigated for an initially high elevation margin bordered by an escarpment the model results suggest several styles of landscape evolution that are compatible with the observations escarpments may retreat in a regular manner but they also degrade and are destroyed only to reform at the drainage divide between exterior and interior catchments

extension of the astronomically calibrated polarity time scale to the miocene pliocene boundary the early pleistocene to late pliocene astronomically calibrated time scale of shackleton et al 1 and hilgen 2 is extended to the miocene pliocene boundary this is done by correlating the detailed record of caco3 cycles in the trubi and the lower part of the overlying narbone formation rossello composite section sicily to the astronomical record using 1 inferred phase relations between these caco3 cycles and the corresponding orbital cycles of precession and eccentricity and 2 calibration points provided by the previously established astronomical calibration of sapropelitic layers which occur in the topmost part of the caco3 record 2 this correlation allows all small scale caco3 cycles in the rossello composite section to be coded after the correlative precession peak and to be dated astronomically with an accuracy of 1 ky in combination with the available high resolution magnetostratigraphy it further allows the construction of an astronomically calibrated geomagnetic polarity time scale for the major part of the gilbert and gauss chrons this new time scale gives ages for the reversal boundaries of the kaena 3 04 3 11 ma and mammoth 3 22 3 33 ma the gilbert gauss chron boundary 3 58 ma and the reversal boundaries of the cochiti 4 18 4 29 ma nunivak 4 48 4 62 ma sidufjall 4 80 4 89 ma and thvera 4 98 5 23 ma these ages are significantly older than the ages given by conventional time scales age discrepancies gradually increase with increasing age the age of 5 32 ma for the miocene pliocene boundary as defined by the base of the trubi on sicily is almost 0 5 m y 9 5 older than the presently accepted age of 4 86 ma 3 these considerable discrepancies with the conventional time scale can either be explained by an consistent error in the decay constants used in k ar radiometric dating or more likely by diffusional loss of radiogenic argon

tectonic eustatic and climatic significance of raised beaches of val de saire cotentin normandy france detailed mapping morphostratigraphical and geochronological analyses were undertaken in the val de saire cotentin normandy northern france these studies have identified a series of middle and upper pleistocene age deposits overlying four wave cut platforms pf iv pf i which can be associated with temperate high sea level events and equated with mis 11 9 7 and mi substage 5e a sea level stand recorded at 20 m ngf at the la mondree site seems to correspond to mi substage 5c or 5a the completeness of the val de saire record and particularly the width of platform iv mis 11 has so far no equivalent on the south coast of the english channel this study provides contribution to an understanding of the impact of the interglacial glacial cycles in a coastal intraplate situation the cyclicity of the morphogenesis is explained by interaction between eustatic variations and strongly expressed activity of slow uplift ca 60 mm kyr through the middle pleistocene several osl dates from the gravel to sand sequence of the eemian weichselian cycle indicate that these deposits represent the marine regression of the end of the last interglacial

a structural transect between the central north sea dome and the south swedish dome middle jurassic quaternary uplift subsidence reversal and exhumation across the eastern north sea basin

geomorphic limits to climate induced increases in topographic relief recognition of the potential for strong dynamic coupling between atmospheric and tectonic processes has sparked intense cross disciplinary investigation and debate on the question of whether tectonics have driven long term climate change or vice versa it has been proposed that climate change might have driven the uplift of mountain summits through an isostatic response to valley incision because isostasy acts to compensate mean elevations the debate hinges on the question of whether climate change can significantly increase topographic relief or more precisely increase the volume of missing mass between summits and ridges here we show that in tectonically active mountain ranges geomorphic constraints allow only a relatively small increase in topographic relief in response to climate change thus although climate change may cause significant increases in denudation rates potentially establishing an important feedback between surficial and crustal processes neither fluvial nor glacial erosion is likely to induce significant isostatic peak uplift

analysis of tilting near normal faults using calculus of variations implications for upper crustal stress and rheology abstract an initially horizontal surface in the surroundings to a normal fault will after extension tilt towards the fault if in the hanging wall or away from it if in the footwall coseismic deformation of these surroundings can be validly modelled as flexure cumulative deformation on geological time scales has been regarded as flexure also but this has led to the apparent paradox that many observed structures require the effective elastic thickness of the brittle upper crust to be much smaller than its seismogenic thickness this article presents a possible alternative that cumulative deformation of the upper crust near some active normal faults may be regarded instead as partitioned into separation of the blocks that comprise their surroundings through the horizontal component of dip slip on the fault and distributed vertical simple shear in their surroundings which causes them to tilt and takes up the vertical slip on the fault a generalized profile of tilting near a normal fault which approximates a parabola can be derived following two assumptions first the brittle layer retains an elastic term in its rheology on geological time scales such that it resists arbitrary length changes second the brittle layer minimizes its overall vertical deflection thus minimizing the buoyancy force acting on it maximum stress and total strain energy associated with observed profiles of tilting are typically smaller for distributed vertical simple shear favouring this mechanism over flexure

late cenozoic flexural deformation of the middle u s atlantic passive margin despite the century long recognition of regional epeirogeny along the middle atlantic passive margin relatively few studies have focused on understanding postrift uplift mechanisms here we demonstrate that epeirogenic uplift of the central appalachian piedmont and subsidence of the salisbury embayment represent first order flexural isostatic processes driven by continental denudation and offshore deposition our results show that regional epeirogenic processes present on all atlantic type passive margins are best resolved by specific stratigraphic and geomorphic relationships rather than topography a simple one dimensional geodynamic model constrained by well dated baltimore canyon trough coastal plain and lower susquehanna river piedmont stratigraphy simulates flexural deformation of the u s atlantic margin the model represents the passive margin lithosphere as a uniformly thick elastic plate without horizontal compressive stresses that deforms flexurally under the stress of strike averaged vertically applied line loads model results illustrate a complex interaction among margin stratigraphy and geomorphology the isostatic response to denudational and depositional processes and the modulating influence of exogenic forces such as eustasy the current elevation with respect to modern sea level of fluvial terraces and correlative coastal plain deposits or unconformities is successfully predicted through the synthesis of paleotopography eustatic change and margin flexure results suggest that the middle u s atlantic margin landward of east coast magnetic anomaly is underlain by lithosphere with an average elastic thickness of 40 km flexural rigidity d 4 1023 n m the margin experiences an average long term denudation rate of approximately 10 m m y and the piedmont has been flexurally upwarped between 35 and 130 meters in the last 15 m y long term isostatic continental uplift resulting from denudation and basin subsidence resulting from sediment loading are accommodated primarily by a convex up flexural hinge physiographically represented by the fall zone our results elucidate an inherent danger in using topography alone to constrain late stage passive margin deformation mechanisms only through careful synthesis of field stratigraphic and geomorphic elements such as fluvial terraces coastal plain deposits and offshore stratigraphy can age control be extended from the offshore depositional setting to the erosionally dominated continent this study demonstrates that despite a relatively subdued topography the middle u s atlantic margin experiences progressive flexural isostatic deformation similar to that proposed for high relief margins characterized by great escarpments thus margin topographic diversity remains a function of other factors such as lithospheric composition and or structure supracrustal stratigraphy and structure degree of drainage integration drainage divide migration and climate

major river systems of central and southern britain during the early and middle pleistocene central and southern britain was drained by two main river systems during the larger part of the early and middle pleistocene the thames and bytham rivers evidence for these rivers and their quaternary history is represented by their sediments the kesgrave and bytham sands and gravels respectively the geomorphological position of the sediments biostratigraphy and amino acid geochronology evidence from the earlier parts of the early pleistocene tiglian c4b and earlier indicates low energy river systems and marine conditions over much of east anglia for most of the early pleistocene tiglian c4c to the cromerian complex the ancestral thames was the main river with at its maximal extent a catchment that extended into wales and across east anglia and what is now the north sea to join the ancestral rhine during this period glaciers in the uplands of wales and periglacial mass movement elsewhere supplied material to the catchment and it was at this time that the bulk of the sorted quaternary ssediments of lowland britain were deposited the bytham river system has no successor because the landscape now in existence has been fundamentally altered by glacial erosion this catchment drained most of midland england and joined the thames in central east anglia initially the bytham river was a tributary of the thames but over time it extended its catchment and at the beginning of the cromerian complex it became the main river of southern britain with the anglian glaciation 01 stage 121 the bytham river was destroyed and the thames was diverted to its present route through london

re evaluation of extension across the pearl river mouth basin south china sea implications for continental lithosphere deformation mechanisms abstract the tertiary pearl river mouth basin in the south china sea is one of relatively few localities where independent estimates of extension from upper crustal normal faulting crustal thinning and subsidence have been compared previous work indicates that these methods all support extension factor 1 8 for this basin however the estimate from faulting used the controversial rigid domino method whereas summing normal fault heaves gives only 1 3 instead this study pursues the possibility that the true value for this basin is 1 3 and the published estimates of extension from subsidence and crustal thinning are exaggerated because they do not take account of outflow of lower crustal material from beneath this basin such outward channel flow will occur when the lithostatic pressure at the base of the brittle upper crust is greater beneath a basin than beneath its surroundings in response to such a pressure gradient material lost from beneath this basin has probably flowed to beneath the adjacent chinese landmass where it isostatically compensates the erosion that has supplied much of the basin s sediment

flow in the lower continental crust as a mechanism for the quaternary uplift of south east england constraints from the thames terrace record abstract the sequence of terraces of the river thames in south east england has been shown to date from the early pleistocene onwards and to provide an indication of the quaternary uplift history of the region using this evidence supplemented by altitudes of pliocene and early pleistocene marine sediments we have determined the pliocene and quaternary uplift histories of five representative localities clacton colchester and dartford for the lower thames and cookham and reading for the middle thames these uplift histories have been modelled using a physics based technique which calculates the isostatic response involving flow in the lower continental crust induced by cyclic loading at the earth s surface our results suggest that the late pliocene and early pleistocene part of the uplift history of our study region was initiated following the deterioration in climate starting at 3 1 ma which marked the start of upland glaciation elsewhere in europe the later increase in uplift rates in the middle pleistocene followed the start of intensified cyclic loading by very large continental ice sheets during and after oxygen isotope stage ois 22 at 0 87 ma dartford cookham and reading in the interior of south east england are all shown to have begun to uplift quite rapidly at rates of up to 0 1 mm a 1 following the start of forcing at 3 1 ma they have since uplifted by distances which increase gradually westward from 200 to 250 m of which a uniform 70 m has occurred since ois 22 at 0 87 ma in contrast clacton and colchester near the present north sea coastline experienced slow subsidence until the late early pleistocene but have nonetheless uplifted since ois 22 by similar distances to the other sites

forested arctic evidence from north greenland shallow water marine sediments of the kap kabenhavn formation at lat 82 30 n perry land north greenland contain an abundance of well preserved remains of terrestrial vegetation and invertebrate fauna indicative of a mosaic of forest tundra environments having similarities to present conditions in labrador the presence of foraminifera faunas marine molluscs and one mammal species supported by studies of paleomagnetism and amino acid diagenesis suggests an age of 2 ma at the pliocene pleistocene transition at this time the arctic tree line was located 2500 km to the north of its present position in the northwest atlantic region and forest tundra vegetation existed in lowland areas bordering on an arctic ocean without perennial sea ice cover

lithospheric dynamics and the rapid pliocene quaternary subsidence phase in the southern north sea basin abstract we present stratigraphic modeling and quantitative analysis of the pliocene and quaternary subsidence of the southern north sea basin during the late pliocene well before the onset of quaternary glaciation the subsidence rate in the southern part of the north sea basin showed a ten fold increase relative to previous tertiary rates the high pliocene quaternary subsidence rate is consistent with the direction and state of the present intraplate stress field in northwest europe one possible consequence of the modern compressional stress field in northwest europe is reactivation of faulting in the central graben resulting in localized stretching and the development of pull apart basins alternatively the acceleration in late pliocene subsidence rates could be due to localized flexural downwarping of the lithosphere in the central graben caused by an increase in the level of intraplate compression both mechanisms succesfully predict the major characteristics of the overall quaternary subsidence history and stratigraphy gravity modeling suggests that the mechanism of localized stretching dominates the recent tectonostratigraphic evolution of the southern north sea

quaternary evolution of the corinth rift and its implications for the late cenozoic evolution of the aegean summary we present geological and morphological observations at different scales to constrain rates of faulting and the distribution of deformation in the seismically active aegean region we focus first on the 130 km long corinth rift an asymmetric graben where a flight of terraces of marine origin are uplifted we show that the edges of the terraces lie in the footwall of the normal fault bounding the corinth rift and correspond to sea level highstands of laic pleistocene age using a detailed analysis of aerial and spot imagery supported by field observations we have mapped 10 terrace platforms and strandlines ranging in elevation from 10 to 400 m over distances of 2 to 20 km from the fault the elevation of the terraces inner edges was estimated at 172 sites with an error of 5m this data set contains a precise description of the uplift and flexure of 10 different palaeohorizontal lines with respect to the present sea level to date the deformation we correlate the corinth terraces with late pleistocene oxygen isotope stages of high sea level stands and with global sea level fluctuations using a thick elastic plate model consistent with our current understanding of the earthquake cycle and a boundary element technique we reproduce the geometry of the shorelines to constrain both mechanical parameters and the slip on the fault we show that the seismogenic layer behaves over the long term as if its elastic modulus were reduced by a factor of about 1000 all the terraces are fitted for fault slip increasing in proportion to terrace age and the component of regional uplift is found to be less than 0 3 mm yr 1 the best fits give a slip rate of 11 3 mm yr 1 on the main rift bounding fault over the last 350 kyr other geological and morphologic information allows us to estimate the total age of the main fault 1 ma and to examine the mechanical evolution of the corinth rift the minimum observed sediment thickness in the gulf places an extreme check on the results of the modelling and a lower bound on slip rate of 6 7 mm yr 1 40 per cent less than estimated with modelling even this slip rate is nearly 10 times higher than for comparable features in most of the aegean and elsewhere in the world at a larger scale the spacing and asymmetry of the rift systems in the aegean suggest strain localization in the upper mantle with slow extension starting 15 myr ago or earlier the more recent 1 myr rapid phase of rifting in corinth partly reactivated this earlier phase of extension the younger faulting in corinth appears to result from its present location in the inhomogeneous stress field process zone of the south westward propagating tip of the southern branch of the north anatolian fault we extend these relations to propose a mechanical model for the late cenozoic evolution of the aegean as the arabia europe collision progressed in eastern turkey it caused anatolia to move to the west and the north anatolian fault to propagate into the aegean where the early slow extension started to be modified about 5 ma ago the process of propagation dramatically increased the activity of some but not all of the earlier rifts the model we present is compatible with tectonic observations as well as with the seismicity the palaeomagnetic rotations and the displacement field now observed with gps and slr

crustal uplift in southern england evidence from the river terrace records abstract much of the past work on the quaternary rivers of northwest europe has been concerned with river terraces which characterise almost every valley while these terraces are undoubtedly striking features of the landscape the incision achieved by quaternary rivers is equally significant in terms of river behaviour and for an understanding of the factors affecting landform development during the quaternary this paper examines the incision achieved during the quaternary by the thames in both its upper and lower catchments and by the hampshire avon in southern england valley incision rates of ca 0 07 0 10 m ka 1 have been identified although in the lower catchment of the thames these have been enhanced by additional incision in response to glacio isostasy and valley shortening a model is proposed in which regional uplift is recognized as the primary cause of incision by these quaternary rivers possible mechanisms for regional uplift are considered

the growth of geological structures by repeated earthquakes 1 conceptual framework in many places earthquakes with similar characteristics have been shown to recur if this is common then relatively small deformations associated with individual earthquake cycles should accumulate over time to create geological structures following this paradigm we show that existing models developed to describe leveling line changes associated with the seismic cycle can be adapted to explain geological features associated with a fault in these models an elastic layer containing the fault overlies a viscous half space with a different density fault motion associated with an earthquake results in immediate deformation followed by a long period of readjustment as stresses relax in the viscous layer and isostatic equilibrium is restored deformation is also caused as a result of the loading and unloading due to sediment deposition and erosion in this paper the parameters that control the growth of dip slip structures are identified we find that the flexural rigidity of the crust or the apparent elastic thickness provides the main control of the width of a structure the loading due to erosion and deposition of sediment determines the ratio of uplift to subsidence between the two sides of the fault the flexure due to sediment load is much more important in this respect than whether the fault is normal or reverse in character we find that in general real structures are associated with apparent elastic thicknesses of 4 km or less and thus with very low flexural rigidities

quaternary elevation change of the gulf of corinth in central greece dramatic elevation changes have occurred since early pleistocene time in and around the gulf of corinth sedimentary basin in central greece which is actively extending at a maximum rate of ca 2 mm a 1 shoreline deposits younger than 1 million years are found at up to ca 1200 m elevation south of the gulf with sediment from an older plio pleistocene basin above 1750 m the gulf floor in the hanging wall of normal faults along its southern coast has subsided up to ca 1650 m on the same timescale however other hanging wall localities such as the corinth isthmus east of the gulf have uplifted instead during the past million years the gulf has alternated between marine and lacustrine environments in response to glacially induced sea level variations this study establishes its chronology of marine and lacustrine terraces for the past half million years allowing lateral variations in uplift to be investigated to explain the observed elevation changes it is suggested that ca 0 9 million years ago the previously lacustrine gulf became flooded by ca 80 m during an interglacial marine highstand the resulting ca 0 8 mpa increase in lithostatic pressure at the base of the brittle upper crust caused southward lower crustal flow to beneath the older plio pleistocene basin isostatic adjustment uplifted this basin creating unstable topography that enabled rapid erosion this lower crustal flow which since been maintained by the sediment load in the gulf that results from this erosion also causes the hanging wall uplift of the corinth isthmus and other anomalous localities the gulf of corinth is thus an important case study locality for revealing the existence of lower crustal flow during continental extension

evidence for late middle pleistocene glaciation of the british margin of the southern north sea the timing and extent of late middle pleistocene glaciations in england and the southern north sea are controversial topics the recent trent valley palaeolithic project uncovered evidence for a post anglian pre devensian glaciation that affected much of central and eastern england the wragby till of lincolnshire is associated with this glacial event attributed here to marine oxygen isotope stage mis 8 coeval glacigenic deposits in the middle trent suggest that both western and eastern lobes of mis 8 ice reached the derby area these various deposits have been assigned previously to mis 12 10 or 6 although the last can be excluded for the wragby till which is overlain by trent terrace deposits assigned to mis 7 from biostratigraphy and amino acid dating the disposition of these glacigenic deposits within the landscape particularly in relation to terrace deposits of the ancestral river trent and the absence of mis 11 and 9 deposits within the footprint of the glaciation also provide compelling evidence at its maximum extent in eastern england the mis 8 ice reached the peterborough area identifying its extension or otherwise into areas such as north west norfolk and the west midlands requires further work

the somme valley terrace system northern france a model of river response to quaternary climatic variations since 800 000 bp recent research on the somme valley terrace deposits that began in 1987 has resulted in an integrated sequence of geological and geomorphological evidence for this area that is of particular significance for prehistoric investigations this has been achieved using previous evidence and new results from archaeological and geological excavations these include longitudinal profiles cartography and detailed synthesis of sections of alluvial deposits stratigraphy of river deposits and overlying loess sequences the work based on a study of the geometry of the terrace system has resulted in the identification of ninestepped alluvial formations that occur along 70 km of the valley detailed study permits the integration of the various alluvial sequences this suggests that each alluvial sequence results from sedimentation through a single glacial interglacial climatic cycle this hypothesis is confirmed by investigation of soil and loess sequences of the deposits overlying the fluvial sediments the synthesis presented provides a basis for understanding the deposition of the terrace system and an initial chronostratigraphic interpretation for the deposits

uplift driven valley incision and river terrace formation in southern england outside the limits of middle pleistocene glaciation the river basins of southern england contain long cenozoic terrestrial sedimentary records of greatest importance are the river terrace sequences which contain biostratigraphical and sedimentary evidence that testifies to the high amplitude climatic changes of the quaternary however trends in valley development cannot easily be accommodated within the framework of quaternary climatic change it is argued in this paper that episodic incision and terrace development result from uplift a consequence of the interplay between continuing alpine orogenic movements and erosion driven isostasy using a simple linear model height age an uplift rate of ca 7 cm ka 1 is estimated for the terrace sequence in the upper thames valley this preliminary model is evaluated using the records of adjacent basins 1997 john wiley sons ltd

the mechanical feasibility of low angle normal faulting abstract low angle normal faulting is precluded by elementary rock mechanics arguments however the existence of many low angle normal faults in regions such as western north america has long suggested that this familiar theory is incomplete initiation of a low angle normal fault requires the stress tensor within the brittle upper crust to have inclined principal axes which necessitates a substantial shear stress within the vertical plane nonetheless no one has previously identified any specific extensional stress field which is suitably oriented to allow shear failure of previously unfractured rock at a low angle dip of 30 in preference to the steeper dip of 50 60 predicted by standard theory despite previous claims to the contrary this study shows for the first time that appropriately oriented stress fields can exist however they require the shear stress to locally reach 100 mpa near the base of a 10 km thick brittle layer this is only possible under extreme conditions as it requires dramatic lateral variations in the state of stress across the extending region it is suggested that a shear stress of this order can develop due to the combined effects of lower crustal flow which imparts a horizontal shear traction at the base of the brittle layer and loading which imparts shear traction in the vertical plane associated with the isostatic response to changes in heat flow caused by changes to the geometry of subducting slabs beneath an extending region regional patterns of low angle normal faulting in western north america are thus interpreted in terms of changes to the geometry of subduction of the farallon plate

neogene evolution of the denizli region of western turkey the denizli region contains one of the easternmost neogene sedimentary basins in the part of western turkey that takes up ssw extension this isolated active normal fault zone which contains closely spaced en echelon normal fault branches is investigated using field measurements of fault exposures and tilted sediments and seismological observations as a case study to address its style of extension the denizli basin is no more than 1 km thick and has accommodated up to 4 km of extension substantial 20 sediment dips are readily explicable assuming extension is accompanied by distributed vertical simple shear with initial and present day dips of the main normal faults that control extension most likely 54 57 and 45 50 other aspects of the form of this basin require regional uplift at 0 1 mm yr 1 providing the first indication of major tectonic elevation changes in this actively extending region that are not directly related to throw on normal faults

escarpment evolution on high elevation rifted margins insights derived from a surface processes model that combines diffusion advection and reaction experiments with a surface processes model of large scale 1 1000 km long term 1 100 m y erosional denudation are used to establish the controls on the evolution of a model escarpment that is related to the rifting of a continent the model describes changes in topographic form as a result of simultaneous short and long range mass transport representing hillslope diffusive processes and fluvial transport advection respectively fluvial entrainment is modeled as a first order kinetic reaction which reflects the credibility of the substrate and therefore the fluvial system is not necessarily carrying at capacity one dimensional and planform models demonstrate that the principal controls on the evolution of an initially steep model escarpment are 1 antecedent topography drainage 2 the timescale or equivalently a length scale in the fluvial entrainment reaction 3 the flexural response of the lithosphere to denudation and 4 the relative efficiencies of the short and long range transport processes when rainfall and substrate lithology are uniform a significant amount of discharge draining over the escarpment top causes it to degrade only when the top of the model escarpment coincides with a drainage divide can escarpment retreat occur for these conditions an additional requirement for retreat of a model escarpment without decline is a long reaction time scale for fluvial entrainment this corresponds to a substrate that is hard to detach by fluvial erosion and therefore to fluvial erosion that is not transport limited continuous backtilting of an escarpment due to flexural isostatic uplift in response to denudational unloading helps maintain the scarp top as a divide it is essential if the escarpment gradient is to be preserved during retreat in a uniform lithology low flexural rigidities promote steep and slowly retreating escarpments for given rainfall and substrate conditions the morphology of a retreating model escarpment is determined by the ratio of the short range diffusive and long range advective transport efficiencies a low ratio which is interpreted to correspond to a relatively arid climate and weathering limited conditions promotes steep sharp topped escarpments with straight main slopes and escarpment retreat occurs over a wide range of height scales a high ratio interpreted to correspond to a more humid temperate climate produces a convex upper slope and concave lower slope morphology and only major escarpments are predicted to preserve a high scarp gradient lithological contrasts in the model produce more complex morphologies and predict the formation of scarps crowned by an erosionally resistant caprock however resistant caprocks are not an essential requirement for model scarps to retreat we conclude that the inferred controls and model behavior are both consistent with the present day morphology of rifted continental margins and with modern conceptual models of landscape evolution

fluvial deposition on periodically emergent shelves in the quaternary example records from the shelf around britain abstract this paper explores the record of fluvial sedimentation on continental shelves during the quaternary in areas that are shallow seas in the present day during episodes of higher global ice volume than the present which account for a large proportion of quaternary time large parts of the shelf were dry land drained by rivers the latter included extensions of still existing rivers as well as complete systems that are now lost beneath holocene interglacial seas in areas where extensive epi continental seas have formed during interglacials there is considerable potential for large areas of submerged fluvial sediments to survive on the shelf providing evidence of former river courses and for the evolution of these rivers during the late cenozoic examples of now submerged fluvial systems from the shelf to the south and east of britain are examined submerged terraces of the extended river thames have been mapped beneath the southern north sea in the area offshore from the thames estuary further offshore however all evidence of former sub aerial drainage during the last glacial has been removed by erosion and it is uncertain whether the thames and rhine which would have joined in this area flowed northwards to the north sea or southwards to the english channel although the latter is regarded as more likely the rhine thames is just one example of the very large system that would have existed only during low stands their concentrated freshwater output having a potentially significant effect on ocean systems

uplift driven valley incision and climate controlled river terrace development in the thames valley uk abstract the sequence of terraces of the river thames in southeast england has previously been shown to span the period from the earliest pleistocene to the present this terrace sequence contains biostratigraphical and sedimentary evidence that testifies to the high amplitude climatic changes of the quaternary large scale fluvial incision resulting in basin wide terrace formation appears to have been concentrated at the warming limbs of the major climatic glacial interglacial cycles when sediment supply was greatly reduced this incision and subsequent valley floor widening created the accommodation space for the later aggradation of the terrace sediments during the following warm cold transitions and during the cold stages when high sediment supply conditions prevailed although the timing of terrace aggradation may be controlled by climate change the progressive valley incision recorded by terrace staircases cannot easily be explained in terms of quaternary climatic change alone and recently developed models suggest that long term incision by the thames has been driven by uplift this paper presents an overview of the available terrace data and tabulates incision amounts and rates between key stratigraphic horizons superimposed upon these broad changes revealed by the complex internal sedimentary architecture of many terrace sediments are the geomorphological system responses to both higher frequency climate driven changes and more localized intrinsic fluvial system adjustments

landscape dissection isostatic uplift and the morphologic development of orogens we examine the morphologic factors that determine the isostatic response to landscape dissection in orogenic terrains in order to quantify the relative contributions of active tectonic uplift and passive isostatic uplift in generating mountain topography we demonstrate that although peaks many times the elevation of an assumed initial plateau can theoretically be generated only moderate amounts of peak uplift can be explained by isostatic rebound in real terrains analysis of topographic data from the european alps and other orogens indicates that isostatic uplift in response to dissection can account for about one fourth of the elevation of the highest peaks if local isostatic compensation is assumed and less if the lithosphere has significant flexural rigidity we conclude that although isostatic uplift can be significant in orogens high peaks are predominantly a consequence of tectonic processes in convergent settings

pliocene palaeotemperature reconstruction for the southern north sea based on ostracoda abstract the development of a large northeastern atlantic shelf ostracod database has confirmed that an intrinsic relationship exists between watermass temperature and the spatial latitudinal distribution of benthonic shelf ostracoda a second pliocene ostracod database using assemblages from four boreholes in the netherlands and a number of localities from the east anglian neogene succession has also been constructed a quantitative method of modern analogues and the squared chord distance dissimilarity coefficient has been employed as a means of calculating the level of similarity between recent and neogene assemblages and therefore to aid in the reconstruction of palaeotemperatures in the southern north sea basin during the pliocene the results in the form of contoured dissimilarity values indicate the presence of at least seven palaeoceanographical climatic phases between ca 5 2 and 1 6 ma bp an early pliocene cooling phase ecozone a in which the fauna is dominated by the cryophilic species palmenella limicola norman elofsonella concinna jones robertsonites tuberculatus sars neomonoceratina tsurugasakensis tabuki and acanthocythereis dunelmensis norman supervenes a period of stable subtropical conditions in the miocene a mid pliocene warming phase ecozone b which has been documented throughout the north atlantic can be recognized in the faunal composition of the sublittoral ostracod assemblages of both the netherlands and east anglia a hiatus between the coralline and waltonian crags is thought to be associated with a deterioration in climatic conditions recent analogues to the netherlands faunas of ecozone c first phase late pliocene cooling ca 2 9 ma bp indicate a decrease of approximately 5 6 c in mean summer surface temperatures a return to elevated temperatures of a mauritanian aspect can be seen in the fauna of the fa2 zone and waltonian crag this amelioration of climate occurred prior to the praetiglian cold phase second phase late pliocene cooling ca 2 4 ma bp which again saw the reintroduction of cryophilic species including baffinicythere howei hazel fimarchinella logani brady crosskey and robertson and hemicythere emarginata sars into the southern north sea during the newbournian and butleyan stages the final phase of the latest pliocene third phase late pliocene cooling is only documented in the ostracod fauna of the norwich crag evidence in the covariance of loxoconchidae and norwegian provincial cryophilic species indicates that the polar front may have been as much as 2000 km further south during the deposition of the chillesford sand member norwich crag fm ca 2 0 1 6 ma bp

the chronology palaeogeography and archaeological significance of the marine quaternary record of the west sussex coastal plain southern england u k abstract the quaternary sediments of the west sussex coastal plain have produced a wide range of floral faunal and archaeological remains these sediments consist of marine sands and gravels exhibiting transgressive and regressive trends which occur from present day sea level to c 43 0 m o d and are overlain by terrestrial silts and cold climate periglacial sediments at the present day coastline channel fill deposits occur below modern beach levels new field observations coupled with a re investigation of old sites and literature suggest that five discrete high stands of sea level may be preserved in the area of the west sussex coastal plain age estimates for these deposits suggest that they span large parts of the middle and upper pleistocene oxygen isotope stages 13 to 5 conformable relationships between many of the marine and terrestrial sediments suggest that the potential exists within the area to correlate the marine and terrestrial quaternary stratigraphic records in addition sediments associated with two of these high sea level stands are associated with extensive buried landsurfaces covering large areas of the coastal plain at some locations these intact landsurfaces are associated with evidence for human activity and represent stratigraphic and cultural resources of international importance

lispb revisited a new look under the caledonides of northern britain summary the lithospheric seismic profile in britain lispb shot in 1974 included a 700 km long north south profile of the crust and upper mantle of northern britain the wide angle seismic data from lispb was of exceptional quality and coverage making a reinterpretation using current modelling programs worthwhile this reinterpretation shows that the original crustal model published by bamford et al 1978 satisfies the observed first arrival traveltimes but that further detail of crustal velocity structure may be obtained by model shows strong variations in crustal velocity structure that appear to be correlated with geological and tectonic structures mapped at the surface the new lithospheric model is compatible with the observed gravity field when converted to appropriate densities and the variations in loading along the base of the density model show that the lithosphere is close to local isostatic equilibrium profiles of the variation of velocity and density with depth from the new model are compared with measurements of lewisian rocks made at confining pressures up to 8 kbar allowing the seismic model to be interpreted geologically a synthetic normal incidence profile of the new model is superimposed on the nearby nec deep seismic reflection profile and the features imaged by the two techniques are compared

the origin of large local uplift in extensional regions large localized uplift is commonly observed in continental regions undergoing extension these observations can be modelled by planar high angle normal faulting of an elastic upper crust overlying an inviscid lower crust isostasy provides the necessary driving force the model quantifies the role of flexural rigidity density variations in the crust and erosion and deposition of sediment

the quaternary history of the central and southwestern celtic sea abstract the british sector of the celtic sea south of the isles of scilly has recently been investigated by the institute of geological sciences igs using several types of bottom sampler and several types of acoustic device by this means the bathymetry has been improved a surface sediment chart constructed and the stratigraphy established by comparison of boreholes with seismic sections a great deal of new information has emerged regarding the late pliocene quaternary history of the area the celtic sea shelf is very wide with a low general gradient and a relatively deep shelf edge the inner shelf is topographically almost featureless whereas the middle and outer shelf are diversified by a series of large tidal sand ridges tsr running approximately normal to the shelf edge the late pliocene quaternary sediments in the area consist of two main formations the late pliocene early pleistocene upper part of the little sole formation and the late devensian early flandrian melville formation both formations appear to be composed predominantly of sand with subordinate gravel and a minor proportion of mud the upper little sole probably consists mainly of fluvial deposits accompanied by subordinate shallow marine deposits in its upper part whereas the melville consists essentially of tidal deposits which have been fashioned probably by the huthnance mechanism into the tidal sand ridges later erosion has developed a gravelly lag pavement layer b across the top of the melville formation and across exposures of upper little sole or older formations between the ridges above this comes a layer of mobile sandy sediment layer a never more than a few metres thick but fashioned in most places into bedforms appropriate to the local current regime these include ripples megaripples sand waves and sand ribbons ice rafting has evidently been responsible for depositing 1 occasional small mounds of material revealed by side scan sonar which are found on the sea bed between the tsr 2 scattered boulders which occur in the normally pebbly lag pavement and 3 scattered outcrops of till revealed by sampling some of which may represent mounds massive marine planation has occurred in the celtic sea shelf area prior to the upper little sole following the deposition of that formation and probably many times during the pleistocene depths of deposition of samples from the upper little sole together with similar data from the almost coeval st erth beds on the cornish mainland indicate that the area has been tilted oceanwards subsidence of the outer shelf area is confirmed by the relatively deep shell edge the most likely mechanism for these displacements appears to be the resolution of large scale gravity anomalies in the asthenosphere