climate instability during the last interglacial period recorded in the grip ice core isotope and chemical analyses of the grip ice core from summit central greenland reveal that climate in greenland during the last interglacial period was characterized by a series of severe cold periods which began extremely rapidly and lasted from decades to centuries as the last interglacial seems to have been slightly warmer than the present one its unstable climate raises questions about the effects of future global warming

u pb and sm nd isotopic constraints on the evolution of the paleoproterozoic perapohja belt northern finland ten localities representing metasedimentary and igneous rocks from the northern part of the paleoproterozoic perapohja belt fennoscandian shield were sampled for zircon u pb dating by la mc icp ms and sm nd analysis by tims the results revealed two phases of granitic magmatism that took place at 1 99 ga and 1 79 1 77 ga the former age 1989 6 ma was given by the kierovaara granite pluton representing the first example of felsic plutonism of this age in northern finland though a type felsic volcanic rocks of the same age have previously been recognized the strongly negative initial nd values obtained for granitoids ranging from 3 9 to 11 4 are compatible with the previous sm nd data indicating the presence of archean basement in northern finland at the time of granite emplacement a garnet whole rock sm nd age of 1752 14 ma was measured for a mica gneiss constraining the time of metamorphic cooling down to the closure temperature of garnet detrital zircon grains from quartzite samples belonging to the jatulian palokivalo formation and a stratigraphically unassigned lithodemic unit the mellajoki suite yielded solely archean zircon populations in contrast our sample from the martimo formation representing kalevian sedimentation revealed a 66 paleoproterozoic detrital zircon component with the youngest zircon grains showing an age of ca 1 91 ga the new age data allow us to constrain the depositional time of this sedimentary unit between ca 1 91 and 1 88 ga the latter being the time of the synorogenic plutonism our geochronological data coupled with recent data from other karelian belts suggest that the depositional time period for rocks assigned to the kaleva spans ca 150 ma and the simple division of these rocks into two non coeval units the lower and upper kaleva has become problematic

gully systems under undisturbed indigenous forest east coast region new zealand abstract gully erosion is commonly associated with agricultural landscapes where vegetation clearance and farming practices increase runoff leading to fluvial incision however gully erosion can also occur in forests that have undergone some form of disturbance either natural or resulting from human impacts this paper reports on recent gully development within areas of undisturbed indigenous forest as a result of a high magnitude rainfall event on the east coast of new zealand s north island this region through a combination of crushed and sheared rock types steep topography and tectonic and climatic setting has high natural rates of erosion exacerbated by european deforestation in the late 19th and early 20th centuries sequential air photographs spanning a 58 year period between 1939 and 1997 were used to classify and document the growth and recovery of gully systems in the 14 1 km 2 headwaters of the mangaoporo catchment following a severe cyclone in 1988 with a rainfall of 535 mm there were 21 active gully systems within the indigenous forest on photography prior to 1988 only four gully systems were present during this period there were 8 major rainfall events 150 250 mm despite further 5 rainfall events of 150 250 mm between 1988 and 1997 all gully systems showed signs of recovery with a combined reduction in active area of 37 the nature and location of these features is strongly influenced by lithology orientation of jointing and bedding and to a topographic threshold defined by catchment slope and catchment area

mineral magnetic characteristics of podzolic soils developed on sand dunes in the lake gosciaz catchment central poland a number of samples from the a0 a2 b and c horizons have been collected from podzolic soils in the lake gosciaz catchment in central poland the catchment is very uniform consisting of 2 6 m high sand dunes with sparse stands of pine and a grass undervegetation radiocarbon dates of fossil soils covered by dune sand within the same type of environment as the lake gosciaz catchment indicate that the main dune forming phase is of older dryas age magnetic measurements have been carried out on bulk samples and on particle size fractions from the different soil horizons with respect to our mineral magnetic study it can be concluded that the soils are very uniform over the entire catchment relatively high concentrations of magnetic grains are found in the humus layer particularly in the 4 m size fraction as indicated by the highest x xfd sirm and hirm values the most likely mechanism for the magnetic enhancement in these podzolic top soils is continued burning processes low magnetic concentrations in the a2 horizon are due to eluviation and chelation local conditions can lead to a range of magnetic minerals precipitating in the b horizon

rock magnetic and paleomagnetic study on a 27 m long core from lake chapala western mexico paleoenvironmental implications for the last 10 ka abstract we report detailed rock magnetic and paleomagnetic results from a 27 m long sedimentary core collected at depocenter of lake chapala western trans mexican volcanic belt rock magnetic parameters point to psd grain size titanomagnetites as the dominant magnetic mineralogy observed variations in both concentration and grain size dependent magnetic parameters reflect changes in the sediment supply through the studied depth but mainly during the last half century stable characteristic remanent magnetization representative of secular variation of the geomagnetic field was retrieved after alternating field demagnetization of the natural remanent magnetization nrm the comparison of the obtained magnetic inclination and declination logs against the corresponding curves predicted by the global geomagnetic field model sha dif 14k enables to establish an alternative sedimentation rate independent age depth model for the whole core in reasonably good agreement with the one calculated using conventional radiocarbon dating this approach works not only for lake chapala but also for lake chalco the correlation established between rock magnetic parameters and paleoenvironments based on diatom identification of representative samples within specific zones can be considered as a novel proxy methodology this approach opens a new perspective for new more detailed rock magnetic paleomagnetic and paleoenvironmental investigations for better paleoclimatic reconstructions

geomorphic changes in a complex gully system measured from sequential digital elevation models and implications for management high resolution digital elevation models dems were derived from sequential aerial photography of an active uvio mass movement gully complex in new zealand s north island east coast region to measure geomorphic changes over approximately one year the gully showed a complex behaviour combining uvial and mass movement erosion deposition and reworking of materials stored in an active debris fan during the measurement period 5200 1700 m3 of material were eroded from the 8 7 ha gully complex and 670 180 m3 from the 0 8 ha depositional fan giving a total of 5870 1710 m3 for the entire gully complex fan system the results provide a high resolution description of gully behaviour over a short time period and also demonstrate that mass movement slumping and debris ows accounted for almost 90 per cent 4660 200 m3 of the sediment generated this erosional response is described in terms of gully evolution by comparing the gully complex to other systems in the region in various stages of development the effect of gully evolution on geomorphic coupling between the gully complex and channel system is described and coupling is also shown to vary with the magnitude and frequency of rainfall events from a land management perspective the success of strategies such as tree planting to mitigate against gully erosion depends on the stage of gully development particularly on whether or not mass movement erosion has begun in contrast to gully rehabilitation efforts elsewhere basin wide afforestation in the early stages of gully incision is favoured over riparian planting given that mass movement assisted by excessive groundwater pressure is the main process leading to uncontrollable gully expansion to protect land effectively against continuing gully erosion of headwater catchments and resulting downstream aggradation it is necessary for land managers to understand the spatial and temporal variability of gully development fully so that mitigation efforts can be targeted appropriately copyright 2003 john wiley sons ltd

a gully complex model for assessing gully stabilisation strategies abstract the north island east coast region is one of the areas most seriously affected by gully erosion both in new zealand and globally despite extensive efforts to mitigate erosion within the last fifty years the overall area of actively eroding gullies has increased in this study we present a gully model and its application for assessing the effectiveness of several afforestation scenarios to mitigate gully erosion in the east coast region the model uses empirical relationships to represent the major physical processes and environmental factors governing gully sediment yield 1 vertical degradation incision 2 spatial extension growth 3 stabilisation closure 4 the influence of forest cover and 5 the influence of the underlying geologic terrain overall the model shows a good fit and deviates only 6 from the observed actively eroding gully area and 8 from the number of actively eroding gullies the application of the model to assess past and future afforestation schemes indicates that 1 past afforestation efforts were effective in reducing sediment yield by approximately 33 in the waipaoa catchment and by 16 in the waiapu catchment from what it would have been without afforestation 2 the most effective strategy to minimize gully erosion is to reforest all present and newly initiating gullies which would halve the annual sediment yield by 2050 and 3 the earlier the planting is completed the more effectively afforestation will minimise gully erosion

channel evolution controlled by valley configuration during 70 years in a severely erosive catchment mangaoporo river new zealand abstract we examined the channel evolution process in a 19 5 km course in the mangaoporo river catchment area 72 6 km2 in the east coast region of north island new zealand over 70 years using aerial photographs and cross sectional survey records the catchment experienced expansive deforestation during the late 19th and early 20th centuries which accelerated the growth of the gully complexes the manner of the evolution was controlled largely by the underlying lithology that determined the valley configuration in the upstream confined section where hillslope and channel processes were closely coupled continuous sediment supply from gully complexes gradually converted the channel course from a narrow single thread to wide braided reaches or from sediment transfer to storage zones this change was accompanied by a decrease in unit stream power usp in 1939 the usp was above 200 w m2 in most of the upstream section while 40 of the usp values were near or below 50 w m2 in 2012 2013 because a narrow reach situated at the end of the storage zone limited the amount of sediment travelling further the downstream reaches were gradually disconnected from the upstream section and the channel forms changed more moderately than in the upstream section this reduction in sediment travelling with distance transformed a once braided reach at the end of the course to development of a supply limited condition with time the overall channel evolution was accelerated by major rainfall events including prolonged rainfall in 1956 and cyclone bola in 1988 which activated gully complexes and contributed to subsequent channel widening particularly in the upstream section although reforestation starting in the 1980s contributed to deactivation of gully complexes after 1988 the difficulty in controlling their total remission together with the lower usp values of the river in 2012 2013 compared to those before the previous major wet events indicate that the river has been evolving in an irreversible direction triggered by land use changes of more than a century ago

development and controlling factors of gullies and gully complexes east coast new zealand sequential aerial photographs of a small headwater catchment in the waiapu basin east coast region north island new zealand were interpreted to measure and analyse temporal changes in active area of gullies and gully complexes for a longer time span 1939 2003 and with higher temporal resolution compared to previous studies we focus on the conditions leading to the development of gullies and gully complexes under pasture and forest by using topographic thresholds slope area relationships of catchments for the initiation of gullies and gully complexes in addition the influence of two different lithologies as well as the occurrence of major rainfall events was related to gully activity twenty gullies and four gully complexes occupying 62 5 ha or 12 5 per cent of the catchment area occurred in the study catchment between 1939 and 2003 however the majority of these were not active at all of the dates studied gullies developed in the sandstone dominated tapuwaeroa formation tended to attain their maximum size by 1957 with a mean catchment area of 2 1 ha gullies developed in mudstone of the whangai formation attained their maximum size in 1939 with a mean catchment area of 4 31 ha exceptions are gullies which developed into mass movement deposits or into an earth flow deposit as well as gullies developed under indigenous forest topographic threshold values for gullies under pasture and indigenous forest show that values for gullies under forest plot far above the threshold line of gullies under pasture indicating that the topographical threshold for gully development under forest is higher compared to under pasture a threshold value of 9 4 ha in catchment area is needed for the development of gully complexes under pasture all located in the whangai formation and with the same orientation as the strike of the mudstones gully complex area and dominance of mass movement erosion increased with larger catchment area a decreasing distance to the threshold line for gullies under pasture indicates a later development for gully complexes no gully complexes developed under indigenous forest indicating that the threshold value for gully complex development is higher than for gully complexes under pasture and was not reached in the study area a model of shifting topographical threshold for gully development for a given catchment is developed which depends on land use when a catchment has an indigenous forest cover the topographical threshold is very high after conversion to pasture threshold values decrease drastically with the invasion of scrub the threshold slowly increases and returns to a similar level to that under indigenous forest after reforestation development of gullies and gully complexes is a highly dynamic phenomenon and phases of expansion and inactivity indicate that models describing only unidirectional advancing stages without periods of inactivity are not suitable therefore this study adds more phases to models of gully and gully complex development in the east coast region the threshold line for gully initiation under pasture and a value of 9 4 ha in catchment area for gully complex initiation permits one to predict which catchments under similar environmental settings develop gullies and gully complexes on a physical basis this enables land managers to implement sustainable land use strategies to reduce erosion rates of gullies and gully complexes copyright 2006 john wiley sons ltd

quantifying sediment connectivity in an actively eroding gully complex waipaoa catchment new zealand abstract using a combination of airborne lidar 2005 and terrestrial laser scanning 2007 2008 2010 2011 sediment delivery processes and sediment connectivity in an 20 ha gully complex which significantly contributes to the waipaoa sediment cascade are quantified over a 6 year period the acquisition of terrain data from high resolution surveys of the whole gully fan system provides new insights into slope processes and slope channel linkages operating in the complex raw terrain data from the airborne and ground based laser scans were converted into raster dems with a vertical accuracy between surveys of 3 of sediment annually with a standard deviation of 20 806 m 3 the volumes of debris eroded from those areas dominated by surface erosion processes were higher than in areas dominated by landslide processes over the six year study period sediment delivery from the source zones to the fan was a factor of 1 4 times larger than the volume of debris exported from the fan into te weraroa stream the average annual volume of sediment exported to te weraroa stream varies widely from 23 195 to 102 796 m 3 fluctuations in the volume of stored sediment within the fan rather than external forcing by rainstorms or earthquakes account for this annual variation no large rainfall events occurred during the monitoring period therefore sediment volumes and transfer processes captured by this study are representative of the background conditions that operate in this geomorphic system

rock magnetic proxies of climate change in the loess palaeosol sequences of the western loess plateau of china summary results of the first detailed study of the climate proxy record in the loess palaeosol sequence at xining one of the few palaeoclimate sites in the currently arid western loess plateau of china illustrate the importance of making many types of rockmagnetic measurements other than susceptibility a multiparameter approach yielded confirmation that here as elsewhere in the loess plateau the susceptibility enhancement in palaeosols was caused primarily by ultrafine magnetite and maghaemite nevertheless magnetic enhancement was caused not exclusively by changes in relative grain size but also by variations in concentration and mineralogy of the magnetic fraction the effects of concentration variations were removed through normalization of susceptibility and anhysteretic remanence with saturation magnetization and saturation remanence respectively the resulting signal was ascribed more confidently to variation in magnetic grain size which in turn was interpreted as a better proxy of pedogenesis than simple susceptibility variations in magnetic mineralogy were also determined to constrain interpretations further the data were then used to discuss climate history at xining finally results from xining were compared with other western sites and contrasted with eastern sites in summary 1 data is presented from a new loess plateau site which also appears to yield a global climate signal 2 a demonstration is made of a more rock magnetically robust way to separate concentration composition and grain size controls on susceptibility and other magnetic parameters and 3 models are provided for inter regional comparisons of palaeoclimate proxy records

late pleistocene and holocene paleoenvironments of chalco lake central mexico abstract in order to establish paleoenvironmental conditions during the late quaternary four cores from the basin of mexico central mexico were drilled in chalco lake located in the southeastern part of the basin the upper 8 m of two parallel cores were studied using paleomagnetic loss on ignition pollen and diatom analyses based on 11 14c ages the analyzed record spans the last 19 000 14c yr b p volcanic activity has affected microfossil abundances both directly and indirectly resulting in absence or reduction of pollen and diatom assemblages important volcanic activity took place between 19 000 and 15 000 yr b p when the lake was a shallow alkaline marsh and an increase of grassland pollen suggests a dry cold climate during this interval abrupt environmental changes with increasing moisture occurred from 15 000 until 12 500 yr b p the lake level increased and the pollen indicates wetter conditions the highest lake level is registered from 12 500 to ca 9000 yr b p the end of the pleistocene is characterized by an increase in humidity from 9000 until ca 3000 yr b p chalco lake was a saline marsh and the pollen record indicates warmer conditions after 3000 yr b p the lake level increased and human disturbance dominates the lacustrine record

controls on gully formation following forest clearing in a humid temperate environment we have constructed a chronology of gully initiation forest clearing and rainfall events for gullies eroded into pine plantations near bombala southeastern australia over the last 15 years the chronology suggests that daily rainfall of 80 100 mm which has a recurrence interval of 1 4 2 years can initiate gully erosion on areas cleared of native forest within the previous year massive gully erosion was experienced from a daily rainfall of 200 mm with a recurrence of 10 15 years resistance to channel initiation effectively recovers within a year of disturbance allowing only a limited opportunity for erosion analysis of the spatial pattern of gully erosion using a digital elevation model shows that gullies were initiated across all landscape positions in contrast to previous studies there is no clear topographic threshold that limits the extent of the gully network we infer that the weak topographic threshold results from low resistance to scour allowing local flow convergence to dominate over topographic accumulation of flow although resistance to scour is low relative to previous studies a process threshold for gully initiation is still a useful simplification of the erosion processes for the soils that we studied the threshold for gully erosion relates to intense scour exposing erodible subsoils

testing the ephemeral gully erosion model egem for two mediterranean environments few models can predict ephemeral gully erosion rates e g creams egem the ephemeral gully erosion model egem was specifically developed to predict soil loss by ephemeral gully erosion although egem claims to have a great potential in predicting soil losses by ephemeral gully erosion it has never been thoroughly tested the objective of this study was to evaluate the suitability of egem for predicting ephemeral gully erosion rates in mediterranean environments an egem input data set for 86 ephemeral gullies was collected detailed measurements of 46 ephemeral gullies were made in intensively cultivated land in southeast spain guadalentin study area and another 40 ephemeral gullies were measured in both intensively cultivated land and abandoned land in southeast portugal alentejo study area together with the assessment of all egem input parameters the actual eroded volume for each ephemeral gully was also determined in the field a very good relationship between predicted and measured ephemeral gully volumes was found r2 0 88 but as ephemeral gully length is an egem input parameter both predicted and measured ephemeral gully volumes have to be divided by this ephemeral gully length in order to test the predictive capability of egem the resulting relationship between predicted and measured ephemeral gully cross sections is rather weak r2 0 27 therefore it can be concluded that egem is not capable of predicting ephemeral gully erosion for the given mediterranean areas a second conclusion is that ephemeral gully length is a key parameter in determining the ephemeral gully volume regression analysis shows that a very significant relation between ephemeral gully length and ephemeral gully volume exists r2 0 91 accurate prediction of ephemeral gully length is therefore crucial for assessing ephemeral gully erosion rates copyright 2001 john wiley sons ltd

application of the egem model to predict ephemeral gully erosion in sicily italy abstract recent research has shown the importance of ephemeral gully eg erosion in the context of global erosion and at the same time the lack of adequate models to estimate it at present the ephemeral gully erosion model egem is the only conceptual model specifically developed for ephemeral gully erosion estimation the main aim of the paper is to evaluate the performance of egem model adapted to local conditions compared with that of simple empirical equations a data set of 92 ephemeral gullies formed between 1995 and 2000 in a wheat cultivated study area in sicily italy was used for the purpose in order to improve egem performance two important adaptations were made both the rain distribution type and the causative rainfall of the hydrological component of egem were modified to reproduce local conditions the egem assumption of a constant depth for the entire length of the ephemeral gully was also modified egem performance was tested with two different rain distribution types three different causative rainfalls and two different eg depths the adaptation of the egem hydrological component improves the volume prediction with respect to the standard version of egem the improvement is mainly due to the rain distribution type whereas causative rainfall seems to be less important the use of adjusted eg depths is however essential to minimise the errors between measured and predicted volumes the capability of egem to predict the ephemeral gully cross section is weak and non significant relationships were found between measured and estimated width a regression analysis between ephemeral gully eroded volume and different morphological topographical and hydrological parameters confirms the great importance of eg length to explain eroded volume r 2 0 64 for the simple correlation between volume and length considering that the adaptation of the hydrological component and the measurement of eg depths are necessary for the eg volumes estimated by egem to be reliable it seems more simple as suggested by other authors to use empirical relations between eroded volume and length performed in different environments until more precise physically based models are developed

reaction and relaxation in a coarse grained fluvial system following catchment wide disturbance abstract the waiapu river catchment drainage area of 1734 km2 is one of the most prolific conveyors of sediment in the world annually delivering roughly 35 mt of fine material to the ocean from eroding gullies hillslopes and reworked sediment on valley floors tectonic and geologic influences in combination with a dynamic climate influenced by tropical cyclones and clearance of vegetation from steep hillslopes predisposes this region to high rates of erosion the bedload sediment regime of the river is strongly influenced by several exceptionally large gullies and gully complexes that produce a coarse grained poorly sorted sediment mixture rapid abrasion and breakdown leads to high rates of suspended sediment yield a wave of bedload material manifesting as elevated bed levels and significant widening of active alluvial fills has been triggered by large inputs of hillslope material from a few key tributary catchments following cyclone bola in 1988 we review the evidence for the relaxation process of the sedimentary system in the subsequent 29 years appraising some of the legacy effects that may endure as associated with reworking of the considerable alluvial stores within the waiapu system we use structure from motion sfm techniques and archival aerial photos to quantify changes in sediment storage at the base of two major gully systems in recent decades a record of over 850 cross section surveys at 62 sites on 10 rivers throughout the catchment 1958 2017 indicates recent transition from a trend of continuous accumulation to downcutting and remobilisation of valley bottom deposits the channel cross sections provide a minimum estimate of sediment flux from source areas to the lower reaches of the river giving a rudimentary but spatially extensive picture of the wave of material cascading through the drainage network the largest impacts occur in the upper steepland rivers closest to the landslide derived sediment supply transport rates here as inferred from cross section change are at a maximum during an aggradational phase following cyclone bola then taper off despite the large sediment accumulations remaining in the system as of 2017 the river is in the process of incising the upper extents of this deposit on a trajectory of recovery toward pre bola conditions the compilation of cross section data provides us with new insights into the sensitivity of particular sites in the landscape as well as the changing relationship between reach sediment storage and transport rates during the response and relaxation phase of a major disturbance in a large catchment

dynamic and static models of gully erosion abstract the main causes of gully formation are anthropogenic factors the clearing of native forests tilling of fallow lands and associated change of the hydrological conditions in the rainfall runoff system gully channels formation is very rapid during the period of gully initiation when morphological characteristics of a gully length depth width area and volume are far from stable this period is relatively short about 5 of a gully s lifetime for the most part of a gully s lifetime its size is near stable maximum value these two stages of gully development led to two types of gully erosion models 1 dynamic models to predict rapid changes of gully morphology at the first period of gully development 2 static models to calculate final morphometric parameters of stable gullies the dynamic gully model is based on the solution of the equations of mass conservation and gully bed deformation the model of straight slope stability was used for prediction of gully side walls inclination the static gully model is based on the assumption of final morphological equilibrium of a gully when averaged for several years elevations and width of gully bottom do not change this stability is associated with a negligible rate both of erosion and sedimentation at the gully bottom it means that flow velocity is less than the threshold value for erosion initiation but is more than the critical velocity of wash load sedimentation the dynamic and static gully models were verified on the data on gullies morphology and dynamics from yamal peninsula russia and new south wales australia

a comparison of different magnetic methods for determining the relative grain size of magnetite in natural materials some results from lake sediments abstract a new rapid method for identifying relative grain size variations in magnetic involves the parameter anhysteretic susceptibility arm i e specific arm obtained in a 1 oe steady field which is particularly sensitive to the single domain sd and small pseudo single domain psd grains of the finer magnetite fraction a second parameter low field susceptibility is relatively more sensitive to the coarser magnetite fraction larger psd and smaller multidomain md grains we can then obtain a measure of the ratio of coarse to fine grain magnetite for large numbers of samples by plotting arversus a simple idealized model based on sized magnetite samples is proposed to explain the use of the armversus plot for detecting relative grain size changes in the magnetic content of natural materials the sediments of three lakes that contain magnetite or a similar magnetic carrier and have a wide range of values of arm and are used to test the model the model is used to interpret the magnetic variations observed and the interpretations are supported by high field hysteresis measurements of the same sediments the combination of the high field hysteresis method of day et al 1 and the arm vs method is a powerful technique allowing the rapid identification of both the relative grain size and domain state for large numbers of samples containing magnetite the armvs method should be used as an intial means of identifying distinct groups of samples the high field hysteresis method should then be applied to a few representative samples from each group to confirm the initial interpretation

gully formation and the role of valley floor vegetation southeastern australia attempts to understand the causes of gully erosion have been hampered by a poor understanding of quantitative changes to the force of flows and the resistance to scour we used flume experiments on an unincised valley floor to determine flow resistance and the critical shear stress for scour under natural and degraded vegetation covers applying the results to sites of gully formation in southeastern australia demonstrates the crucial role that reduced vegetation cover plays in increasing the susceptibility of valleys to channel incision widespread and rapid gully formation in the 19th century required degradation of valley floor vegetation and was not solely the result of land use or climatically induced increases in discharge

lake levels since about 40 000 years ago at lake chalco near mexico city abstract diatoms magnetic susceptibility organic content and14c ages of sediments from a 26 m core suggest that lake chalco in the southern part of the basin of mexico went through a series of major fluctuations during the late pleistocene and the holocene before ca 39 00014c yr b p the lake was very deep about 8 10 m alkaline and saline it then became shallow

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

badass gullies fluvio mass movement gully complexes in new zealand s east coast region and potential for remediation abstract this paper reviews gully erosion in the east coast region of new zealand s north island and conceptualises fluvio mass movement gully complexes as badass gully systems tectonic setting and lithological control with steep slopes and a climate influenced by tropical cyclones predispose hill country in the east coast region to gully erosion the clearance of indigenous forest since the late 1800s has dramatically increased catchment erosion and paved the way for development of large scale fluvio mass movement gully complexes these features are a composite of fluvial and mass movement processes they are conceptualised as badass by not conforming to any existing gully model and by generating disproportionate results in east coast catchment sediment cascades their remediation is discussed but their nature means that prevention is better than a cure

sedimentation rates in lake chapala western mexico possible active tectonic control abstract lake chapala a major natural freshwater reservoir belongs to the watershed of the rio lerma which originates from the mexico city area 450 km eastwards the east west trending lake chapala basin is located on the active tectonic feature citala rift sediments of cores collected in the lake were studied for their 210pb 226ra 137cs and 239 240pu activities in order to evaluate sedimentation rates profiles of magnetic susceptibility allowed stratigraphic correlations to be made since some fine levels display more or less high susceptibility values this allows an average sediment accumulation rate to be calculated the sediment accumulation rate was calculated assuming that the activity at the interface of a defined site is constant in the course of time since any global decrease or increase in the rates could not be observed the direct flux of atmospheric 210pb was evaluated from the inventory in a horizontal soil 0 25 0 3 dpm g 1 except from two cores at the west the fluxes to sediment were higher than the direct atmospheric flux the sedimentation rate s temporal variations along the cores seem to be mainly related to annual precipitation changes with rates lower during the dryness epochs 1945 1957 and 1979 1991 the rates measured in the western part of the lake range approximately from 1 to 2 mm year 1 the lowest rates in the central and eastern areas are higher than 2 4 2 5 mm year 1 and exceed 3 5 mm year 1 0 066 g cm 2 year 1 near the rio lerma prodelta as the lake is not deeper eastward than westward it can be suggested that relative subsidence related to the active tectonic framework compensates the higher sedimentation rate

the magnetic susceptibility of sedimenting material trapped in lough neagh northern ireland and its erosional significance1 the magnetic susceptibility of sedimenting material trapped at two sites in lough neagh has been measured over 1 year the magnitude of susceptibility in one of the traps correlates with rainfall in the catchment suggesting a link between channel erosion and the magnetic properties of eroded sediment

management responses to pulses of bedload sediment in rivers abstract rivers can experience sudden pulses of sediment from human and natural erosion processes that can accumulate in the bed abundant studies have examined the sources and dynamics of sediment pulses and problems caused by these pulses particularly flooding avulsions and habitat simplification much less has been written about what managers can do about sediment pulses and that is the purpose of this review the first option for managers is to do nothing and this decision can be informed by many case studies and by theory on the propagation and character of sediment pulses their diffusion translation and celerity doing nothing should be informed by the secondary effects of sediment pulses on channels including widening avulsions and tributary interactions if managers decide that something needs to be done about the sediment they have four options 1 reducing the sediment supply at source 2 trapping sediment in the channel 3 accelerating sediment transport through a reach and 4 directly extracting sediment the most common of these actions is undoubtedly to reduce the supply at source but there are few examples of the consequences of this for sediment pulses there are even fewer examples of trapping accelerating and extracting sediment all of these options have great potential for managing sediment pulses however they also have the potential to trigger incision of tributaries and of the channel behind the passing sediment wave overall the literature equips managers to understand the dynamics of sediment pulses but it does not yet equip them to confidently manage these geomorphic events

magnetic properties of lake sediments from lake chalco central mexico and their palaeoenvironmental implications lake chalco 99 0 w 19 5 n in the basin of mexico was formed during the pleistocene after the emplacement of the chichinautzin volcanic field that closed the former drainage system the lake sediment record has been influenced by a number of factors including glacial interglacial cycles local volcanism erosion of soils and anthropogenic disturbances the magnetic properties of the lake sediments and the associated tephra layers of the last 16500 yr have been studied it is found that the magnetic properties of the lake chalco sediments are very distinctive magnetic concentration varies by a factor of 1000 and magnetic stability also varies over an extremely wide range the predominant magnetic mineral is titanomagnetite in addition to an imperfect antiferromagnetic phase possibly goethite an unusually large range of coercivities is found in certain of the tephras down core variations in magnetic properties closely follow climatic environmental changes previously established by other proxy methods the late pleistocene and late holocene lake sediments display a higher concentration of magnetic minerals than the early middle holocene sediments in the non volcanic sediments fluctuations in the magnetic concentration reflect changes in both the intensity of erosion as represented by ferrimagnetic and paramagnetic minerals and by the maturing of soils as represented by geothite copyright 2000 john wiley sons ltd

predicting the topographic limits to a gully network using a digital terrain model and process thresholds a digital terrain model is used with process thresholds to predict the extent of a stable gully network in a 5 km2 catchment of the southeastern highlands of australia the model developed by dietnch et al 1992 1993 predicts the topographic controls on channel networks and interprets these in terms of a critical shear stress for channel incision c applied by saturation overland flow we adapt the model slightly to compare the shear stress applied by hortonian overland flow to that applied by saturation overland flow the limits to gully erosion in the catchment are controlled strongly by a topographic threshold that has an inverse relationship between upslope catchment area and local gradient the topographic threshold for channel incision is reproduced using a simple model of hortonian overland flow and a c appropriate for incision into a degraded grass surface c 245 dyn cm2 this is consistent with historical evidence for the timing of gully erosion the study confirms a strong topographic control on the extent of the channel network in a catchment significantly different from the western north america catchments where the topographic threshold was first demonstrated despite its simplicity the model for incision by overland flow appears capable of distinguishing the hydrological processes responsible for channel incision when these are reflected in the relationship between channel network and landscape morphology the model requires relatively simple inputs suggesting it may be useful for mapping gully erosion hazard in actively eroding catchments

observed and modelled distributions of channel and gully heads with examples from se spain and belgium abstract in soil erosion by overland flow sediment discharge is driven by discharge and gradient against the resistance of the soil and vegetation the form of the relationship which is taken as a sum of power law terms may then be inferred from several data sources 1 ephemeral gully head location 2 permanent channel head location 3 slope profile form 4 consistency with evolutionary models and 5 erosion plot data the paper focuses on 1 to 4 in order to understand how far these data constrain the form of the dependence on discharge and gradient field data from mapping a set of ephemeral gully heads after storms show a weak inverse relationship between channel head gradient and catchment area which flattens towards an upper threshold gradient of about 25 these relationships are compared with those theoretically obtained for a range of sediment transport laws which have been previously used and which are analysed to forecast both overall slope profile form and the location of stream heads the theory predicts that the location of ephemeral gully heads produced in a single storm will differ from the long term average stream head location there is a fairly good relationship between theoretical and observed locations associated with the form of the sediment transport law for a single event the location depends on storm magnitude which cannot be well defined from the data sets creating a spread of data with an envelope curve defined for the largest events the empirically acceptable sediment transport equations have also been used to analyse families of slope profiles in a small area and used within a landscape evolution model to generate landscapes which are compatible with those observed in the field and provide confirmation of the long term viability of the expressions obtained to forecast the direction style and rates of landscape evolution in response to land use or climate drivers

a matlab tool for archaeomagnetic dating a matlab tool for archaeomagnetic dating has been developed in this work well dated palaeosecular variation curves psvcs can be used to date archaeological artefacts with unknown ages the archaeomagnetic direction declination and or inclination and the archaeointensity obtained from the archaeological artefact are compared with a master psvc in addition historical lava flows with controversial ages can be dated using this methodology the dating process follows the descriptions given by lanos 2004 which is based on the combination of temporal probability density functions of the three geomagnetic field elements here we develop an interactive tool in matlab code to carry out archaeomagnetic dating by comparing the undated archaeomagnetic or lava flow data with a master psvc the master psvcs included with the matlab tool are the different european bayesian curves and those generated using both regional and global geomagnetic field models a case study using all the psvcs available in europe and some undated archaeomagnetic data has been carried out to analyze how the different psvcs affect the dating process in addition the dating uncertainty and the relocation error have been analyzed in the european region results show that some regional bayesian psvcs and the regional scha dif 3k archaeomagnetic model are the best choices to obtain an accurate date in europe moreover when it is available the full geomagnetic field vector must be used for archaeomagnetic dating

assessing the sources of sediment transported in gully systems using a fingerprinting approach an example from south east china abstract eroded sediment is an important feature of permanent gully s development however obtaining the specific characteristics of the sediment transport in the gully can be difficult thus a composite fingerprinting technique incorporating uncertainty analysis has been employed to investigate the mean relative contribution of sediment sources in permanent gullies in this study 31 tracers were measured at 62 different sampling sites from three layers of a gully wall surface layer sl sandy soil layer ssl and semi weathering rock layer swl and 36 sediment samples from the slumping deposit and alluvial fan of the gullies the sediment source tracing procedure was therefore used to assess the relative contribution of each source the mean relative contribution from the sl to the sediment of the slumping deposit is higher in the active gully g1 and is relatively lower in the potentially stable g2 and stable gullies g3 thus there was no obvious gully bank retreat in g2 and g3 in different places of the g1 alluvial fan the mean relative contribution of the sl ssl and swl ranged from 9 11 36 43 and 46 55 respectively however the sediment contribution of the sl increased in g2 and g3 due to the changes in the erosion type the mean relative contributions of the sl were 33 5 g2 and 30 3 g3 these findings have important implications for the establishment of a scientific basis for permanent gully sediment transport management and control policies

upper and lower plate juxtaposition deformation and metamorphism during crustal convergence trans hudson orogen quebec baffin segment canada abstract the lower plate of the quebec baffin segment of paleoproterozoic trans hudson orogen comprises parautochthonous archean crystalline basement of the superior province 3 22 2 74 ga and imbricated paleoproterozoic rift margin strata 2 04 1 92 ga the collisional upper plate contains 1 allochthonous ophiolitic units 2 00 ga 2 a continental arc terrane narsajuaq arc 1 86 1 82 ga 3 shelf sequence strata ca 1 86 ga and basement orthogneisses ca 1 95 ga 4 foreland basin deposits 1 86 ga and 5 a batholith which intrudes the shelf and foreland basin rocks cumberland batholith 1 86 1 85 ga lower and upper plate assemblages were juxtaposed during a 1 82 1 79 ga accretion collision event and deformed into regional scale folds during two post collisional folding episodes ca 1 76 1 74 ga as a result of the structural relief generated by the post collisional folding and subsequent exhumation all orogenic elements can be directly examined along a 400 km across strike transect in the external zone northern quebec lower plate rift margin units were internally imbricated cape smith belt and translated southward across the superior province basement paleoproterozoic amphibolite facies mineral growth is syn to post thrusting tectonic imbrication has resulted in a structural inversion of the accreted i e upper plate ophiolite stratigraphy north of the cape smith belt mid crustal plutonic units of the narsajuaq arc form an upper plate crystalline wedge whose sole thrust is localized near the thrust belt s basal decollement within narsajuaq arc syn magmatic granulite facies assemblages are retrogressed to amphibolite facies assemblages in proximity to major accretion collision faults in the internal zone southern baffin island a tripartite orogen scale tectonostratigraphy is exposed on the flanks of the post collisional fold structures at the lowest structural level lower plate superior province orthogneisses are imbricated with paleoproterozoic rift margin units and mineral growth is syn thrusting at intermediate structural level upper plate orthogneisses are correlated with the narsajuaq arc in northern quebec at the highest structural level a north facing shelf sequence is structurally overlain by an assemblage of clastic rocks interpreted as a foreland basin sequence dominantly monzogranite plutons of the cumberland batholith are restricted to the upper structural level and indicate pre emplacement imbrication of tectonostratigraphic units within both upper and lower plates granulite facies assemblages are retrogressed to upper amphibolite assemblages in proximity to 1 82 1 79 ga accretion collision structures exposures of superior province basement across the orogen document a progressive increase in the extent of reworking during accretion of upper plate units from a narrow shear zone in the external zone to km scale imbrication and more pervasive shear deformation in the internal zone a minimum of 160 km of basement underthrusting is constrained by the structural overlap of upper plate allochthons on lower plate units basement involvement during post collision shortening is manifest as thick skinned folding indicating coupling across the collisional basal decollement

secular variation in mexico during the last 40 000 years paleomagnetic data are available for mexico from various archives covering irregularly the last 40 000 years data obtained from lake sediments are affected by ambiguous conversion of age to depth and the paleomagnetic data themselves are not of high quality as samples were only demagnetized at one field intensity these lake sediment data are therefore considered as less reliable for construction of a secular variation curve although they may give some qualitative information for the last 25 000 years archeological samples provide data for the period 100 1200 a d their 14 c ages are some times not well constrained with unrecoverable analytical and statistical procedures and often ages were only inferred from the stratigraphic position and the paleomagnetic record the paleomagnetic record of these materials is of high quality with very low internal dispersion although no magnetic cleaning techniques have been applied variations of inclination and declination with time are hampered by large age uncertainties and thus of limited value for the construction of secular variation curves paleomagnetic data from an u th dated stalagmite provide reasonable directions for most of the last 1200 years being of lower quality in those parts with very low remanence intensity the u th age determinations were interpreted in terms of a constant growth rate which might be only valid as a first order approximation recent volcanic rocks from the trans mexican volcanic belt provide 19 paleomagnetic directions of reasonable to high quality and often also absolute paleointensities ages have been determined from 14 c analysis of charcoal or paleosols found below the lavas and extend over the last 40 000 years therefore volcanic rocks provide the most adequate archive for the construction of a secular variation curve but much more volcanic structures need to be dated to obtain a semi continuous secular variation curve comparison of the data from different archives is possible mainly for the last 2500 years and despite the aforementioned problems similar variations of declination and inclination are observed this holds as well when comparing them to data from holocene volcanic rocks from western north america 2002 elsevier science b v all rights reserved

radiocarbon age inversions and progression source and causes in late holocene sediments from lake chapala western mexico the results of eight radiocarbon datings of lake chapala sediments site t46 are presented the age inversions ai observed and their age progression discussed as deduced from some ais and the 210pb activity site chp4 the bioturbation zone in the lake varies over a depth of 5 25 cm the linear sedimentation rates lsrs calculated from 14c ages do not match the lsr calculated from unsupported 210pb activity for the upper sediments this demonstrates the usefulness of dating sediments with complementary radiometric techniques such as short lived isotope counting slic i e 210pb and 137cs this approach leads to the following conclusions 1 the incorporation of detrital particles with ancient carbon into the sedimentary column of the lake occurred by a combination of a the presence of outcrops of hydrothermal petroleum with ages 40 ka ka thousands of years in the lake and b mass transport due to the presence of two elongated gyre circulation patterns integrated by cyclonic circulation counterclockwise in the north portion of the lake and anticyclonic circulation in the southern part 2 consequently the 14c ages of shallow lake sediments have geologic ages one order of magnitude greater compared to their ages determined by the 210pb method 3 a bioturbation mechanism is not necessary to explain the 14c ai in the top 70 cm and from 110 to 150 cm depth of the sediments 4 according to the biological proxies data for the last 600 years b p the paleoclimate at lake chapala has changed from sub humid to dry environmental conditions and eutrophication has increased over the past 100 years due to local input from ongoing agricultural activities

a geomagnetic field model for the holocene based on archaeomagnetic and lava flow data abstract we propose a new geomagnetic field model for the holocene period based on archaeomagnetic and lava flow data avoiding the use of lake sediment data the source of data comes from the geomagia50v2 database which has been updated with the new archaeomagnetic and volcanic studies published during the last 3 yr the model called sha dif 14k allows us to analyse the behaviour of the geomagnetic field for the last 14 000 yr from 12 000 bc to 1900 ad for the model construction we use the spherical harmonic analysis in space and the penalized cubic b splines in time both spatial and temporal regularization norms are used to constrain the inversion problem and applied at the core mantle boundary cmb to assure the convergence of the model for the last 3 ka the model predictions agree with those given by the global model arch3k 1 and the european model scha dif 3k for older epochs the new model presents a clear improvement in field resolution with respect to other current models of the geomagnetic field for the holocene for the last 9 ka the time evolution of the dipolar moment obtained from the dipole field shows a clear minimum between 5500 bc and 3000 bc and the well known continuous decreasing trend of the geomagnetic field strength for the last millennium and a half a general view of the time average evolution of the geomagnetic field flux lobes at the cmb for the northern hemisphere suggests a marked lobe of positive magnetic flux when the dipole moment was maximum this lobe vanishes when the dipolar field is decreasing the north polar wander paths of both north magnetic dip and geomagnetic poles were obtained showing an average rate of motion of 5 1 km yr and 3 7 km yr respectively the model shows that the geomagnetic field can be averaged as axial dipolar in 2000 yr within an error of 5 the typical uncertainty of the palaeomagnetic studies finally and following the recent definition of archaeomagnetic jerks we found 8 critical events in the time evolution of the geomagnetic field for the last 8 ka characterized by a maximum in the hemispheric asymmetry of the proposed model the model is available in the earth ref digital archive at http earthref org erda 1897

geomorphology and forest management in new zealand s erodible steeplands an overview abstract in this paper we outline how geomorphological understanding has underpinned forest management in new zealand s erodible steeplands where it contributes to current forest management and suggest where it will be of value in the future we focus on the highly erodible soft rock hill country of the east coast region of north island but cover other parts of new zealand where appropriate we conclude that forestry will continue to make a significant contribution to new zealand s economy but several issues need to be addressed the most pressing concerns are the incidence of post harvest storm initiated landslides and debris flows arising from steepland forests following timber harvesting there are three areas where geomorphological information and understanding are required to support the forest industry development of an improved national erosion susceptibility classification to support a new national standard for plantation forestry terrain analysis to support improved hazard and risk assessment at detailed operational scales and understanding of post harvest shallow landslide debris flows including their prediction and management

near orthogonal deformation successions in the poly deformed paleoproterozoic martimo belt implications for the tectonic evolution of northern fennoscandia abstract structural mapping integrated with aeromagnetic and anisotropy of magnetic susceptibility ams data form complimentary and robust tools for analysis of regional structures and fabric overprinting relationships this multi scale approach is used to constrain the geometry and tectonic evolution of sparsely exposed and flat lying outcrops of the martimo belt mb of northern fennoscandia the mb records a history of near orthogonal deformations upper greenschist to lower amphibolite facies metamorphism between ca 1 92 1 79 ga the earliest deformation d1 involved east directed thin skin thrusting and the development of recumbent f1 folds and a n s trending s1 fabric d2 deformation is prominent in the central part of the mb and is characterized by n s shortening with the development of e w trending f2 folds an associated pervasive steeply dipping s2 foliation and type 2 fold interference pattern the mb and mellajoki suite exhibit regional scale d2 synformal and antiformal refolded structures respectively d3 is more heterogeneously developed and manifests bimodal orientations with nnw sse and wnw ese structural trends it is pronounced in the central and eastern parts of the mb but weakly developed in the western part the steep dip of s3 in the region suggests that it formed in response to ne sw bulk shortening d4 structures have a conspicuous nne ssw trend that is visible as lineaments on the aeromagnetic image and locally in the field the last deformation event d5 affected almost the entire mb and was characterized by broadly wsw ene oriented crustal shortening the n s oval shape geometry of the eastern part of the mb is attributed to the d5 event contrasting with well developed overprinting relationships between d1 and d3 structures the relative timing of d3 d5 could not be established in the study area but can be inferred from structures with similar trends in the central lapland granitoid complex which is located north of the mb the d1 d5 deformation scheme can be readily reconciled with the tectonic evolution of the lapland savo fennian svecobaltic and nordic orogens of the composite svecofennian orogen the age of d1 in the northern part of the lapland savo orogen is 1 91 ga based on crosscutting granitoids and maximum deposition ages of sedimentary rocks d2 1 90 1 89 ga has been linked to orogen parallel shortening during the late stage of southern part of the lapland savo orogen several orthogonal tectonic events in northern fennoscandia indicate amalgamation of crustal blocks around the core of the archean karelia continent at 1 92 1 77 ga and that fennoscandia was a key component of the columbia hudsonia nuna supercontinent

sm nd and pb isotopic study of mafic rocks associated with early proterozoic continental rifting the peropohja schist belt in northern finland the perapohja schist belt in northern finland rests unconformably on archaean granitoids and marks the early stages of proterozoic crustal evolution in the fennoscandian baltic shield 2440 ma old layered mafic intrusions predate the supracrustal and ca 2200 ma old sills of the gabbro wehrlite association intrude the lowest quartzites and volcanics runkaus of the sequence the sm nd mineral isochron of the penikat layered intrusion gives an age of 2410 64 ma the initial nd values of the penikat intrusion nd 2440 1 6 and the runkausvaara sill nd 2200 0 suggest that these mafic magmas were contaminated by older crustal material the sm nd and pb isotopic results on the 2 44 2 2 ga old runkaus volcanics indicate mobility of pb fractionation of sm nd during late greenschist facies metamorphism and crustal contamination the pb pb data provide an age of 1972 80 ma with a high initial 207pb 204pb ratio 1 8 49 while scattered sm nd data result in an imprecise age of 2330 180 ma with an initial nd value of about zero secondary titanite gives an u pb age of ca 2250 ma the jouttiaapa basalts in contrast ascended from the mantle without interaction with older crust these lree depleted tholeiites mark a break in continental sedimentation and yield a sm nd age of 2090 70 ma their initial nd 4 2 0 5 implies that the subcontinental early proterozoic mantle had been depleted in lree for a long period of time the first lava flows are strongly depleted in lree suggesting that their source was significantly more depleted than the source of mid ocean ridge basalts today

palynological and magnetic susceptibility records of lake chalco central mexico abstract pollen and magnetic susceptibility data from a 11 27 m long core drilled in the central part of lake chalco 99 00 w 19 15 n located at the southeastern part of the basin of mexico are interpreted in terms of paleoenvironmental changes the record of this subtropical highland lake dated by radiocarbon methods spans approximately 24 000 yr b p and documents changes in climate vegetation lake level and volcanic activity seven palynozones were established by using the method of cluster analysis for correlation purposes zones 7 6 and 5 between 20 600 and 18 300 yr b p indicate reduced forests with extensive grasslands relatively high input of sediments by water discharge of surface streams and high lake level the evidences obtained in zone 4 between 18 300 and 17 500 yr b p suggest a dry and warm climate with xerophytic vegetation lower lake level and erosion rates zone 3 between 17 500 and 10 000 yr b p shows a trend to increasing moisture and cooler temperatures volcanic activity during this period is intense and strongly influences the natural environments at around 12 000 yr b p a clear expansion of forests and fulfillment of the lake recorded at the beginning of the holocene an oak forest expansion and a lowering of lake levels are initiated and by the mid holocene zone 2 subhumid temperate conditions are detected although lake level continues to be low the human impact is recorded in the last 4000 yr

a spatial information technology approach for the mapping and quantification of gully erosion abstract in contrast to the effort during the last decades to investigate sheet interrill and rill soil erosion processes relatively few studies have been focused on quantifying and or predicting gully erosion the extension of the use of modern spatial information technologies such as geographical information systems gis digital elevation modelling dem and remote sensing have created new possibilities for research in this field a key issue to be addressed as the basis for predicting the effects of global changes such as land use and climate changes is the mapping and quantification of gully erosion rates including rate of retreat of gully walls and rate of sediment production this research work presents a method to compute the rate of retreat of gully walls and the associated rate of sediment production caused by gully erosion the proposed method uses multitemporal aerial photographs and multitemporal digital elevation models both of which have been processed using gis techniques the research was applied to a sample catchment of 25 km2 located in catalonia spain aerial photographs at scale of 1 30 000 from 1957 and orthophotos from 1993 were used to map gully erosion and determine erosion rates between 1957 and 1993 the rates of channel incision and sediment production were computed from the subtraction of multitemporal digital elevation models the rate of gully walls retreat was 0 2 m year 1 representing a rate of 0 9 m2 year 1 the maximum rate of channel incision 0 7 0 8 m year 1 occurred at the head of the gully and at meandering zones the rate of sediment production caused by gully erosion was 1322 142 ton ha 1 year 1 in comparison with other methods to compute sediment production caused by gully erosion processes the proposed method integrates the losses due to overland flow mass movements and gully deepening and supposes an improvement to locate the areas within the gullies with higher erosional activity

modelling landscape evolution in the waipaoa catchment new zealand a phenomenalogical approach landscape evolution models require detailed strength measurements which are difficult to obtain for large areas we offer an alternative phenomenalogical approach to modelling landscape evolution one that requires few input parameters the phenomena are hills channels floodplains knickpoints and coastal floodplain the model is demonstrated on the highly erodible waipaoa catchment in new zealand a digital elevation model is simulated every thousand years from 63000 bp through to present day there is good agreement between predicted and observed terrace heights and also good agreement between predicted and observed knickpoint locations suggesting the phenomenalogical approach is indeed representing the main drivers of landscape evolution in the waipaoa catchment

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

gully erosion impacts factors and control gully erosion attracts increasing attention from scientists as reflected by two recent international meetings poesen and valentin eds catena 50 2 4 87 564 li et al 2004 gully erosion under global change sichuan science technology press chengu china 354 pp this growing interest is associated with the increasing concern over off site impacts caused by soil erosion at larger spatial scales than the cultivated plots the objective of this paper is to review recent studies on impacts factors and control of gully erosion and update the review on dgully erosion and environmental change importance and research needst poesen et al 2003 catena 50 2 4 91 134 for the farmers the development of gullies leads to a loss of crop yields and available land as well as an increase of workload i e labour necessary to cultivate the land gullies can also change the mosaic patterns between fallow and cultivated fields enhancing hillslope erosion in a feedback loop in addition gullies tend to enhance drainage and accelerate aridification processes in the semi arid zones fingerprinting the origin of sediments within catchments to determine the relative contributions of potential sediment sources has become essential to identify sources of potential pollution and to develop management strategies to combat soil erosion in this respect tracers such as carbon nitrogen the nuclear bomb derived radionuclide 137 cs magnetics and the strontium isotopic ratio are increasingly used to fingerprint sediment recent studies conducted in australia china ethiopia and usa showed that the major part of the sediment in reservoirs might have come from gully erosion gullies not only occur in marly badlands and mountainous or hilly regions but also more globally in soils subjected to soil crusting such as loess european belt chinese loess plateau north america and sandy soils sahelian zone north east thailand or in soils prone to piping and tunnelling such as dispersive soils most of the time the gullying processes are triggered by

development of a new zealand sednet model for assessment of catchment wide soil conservation works abstract much hill country in new zealand has been converted from indigenous forest to pastoral agriculture resulting in increased soil erosion following a severe storm that hit the manawatu wanaganui region in 2004 and caused 62 000 landslides the horizons regional council have implemented the sustainable land use initiative slui a programme of widespread soil conservation we have developed a new zealand version sednetnz of the australian sednet model to evaluate the impact of the slui programme in the 5850 km2 manawatu catchment sednetnz spatially distributes budgets of fine sediment in the landscape it incorporates landslide gully earthflow erosion surficial erosion bank erosion and flood plain deposition the important forms of soil erosion in new zealand modelled suspended sediment loads compared well with measured suspended sediment loads with an r2 value of 0 85 after log transformation a sensitivity analysis gave the uncertainty of estimated suspended sediment loads to be approximately plus or minus 50 at the 95 confidence level it is expected that by 2040 suspended sediment loads in targeted water management zones will decrease by about 40 the expected decrease for the whole catchment is 34 the expected reduction is due to maturity of tree planting on land at risk to soil erosion the 34 reduction represents an annual rate of return of 20 on 20 million nz of investment on soil conservation works through avoided damage to property and infrastructure and avoided clean up costs

linkage of crustal deformation between the archaean basement and the proterozoic cover in the perapohja area northern fennoscandia abstract reconstructed variations in stratigraphic thicknesses combined with mapped variations in fold and thrust belt structural styles and patterns of the entire palaeoproterozoic perapohja belt in northern finland show that both the deposition of the 2 4 1 9 ga supracrustal rocks and the structural evolution during the subsequent svecofennian orogeny 1 9 1 8 ga have been tightly controlled by i the palaeo topography of the archaean 2 5 ga basement and ii the reactivation of archaean basement faults during the multiple stages of rifting and deposition of the supracrustals as well as during subsequent basin inversion and fold and thrust belt development folds and thrusts in the supracrustal sequence are found to be largely detached from the underlying basement along the petajaskoski detachment zone pdz that formed within a mechanically weak stratigraphic unit in the basal part of the perapohja belt stratigraphy the pattern of contractional structures is complex but developed during one phase of simple progressive south vergent thrusting two styles of basement cover linkage are recognised the hard linked style is best illustrated by the reverse sihtuuna fault currently defining the northern margin of the e w to ene wsw trending basement horsts and the overlying anticlines and juxtaposing the stratigraphically lowermost perapohja belt rocks with higher up stratigraphy indicating the fault is inherited after a pre existing basement structure based on the distribution and thickness variation of the palaeoproterozoic supracrustal units the faults bounding the basement horst were active as extensional faults during deposition the soft linked style relationship is evident as abrupt terminations of thrust related elongate domes and localisation of the compressional overprint into the nw se trending central graben understanding the basement architecture and basement cover linkages is highly significant because the majority of the known mineralizations of the belt are located along or close to the basement faults

some factors controlling gully growth in fine grained sediments a model applied in southeast spain abstract gullies in the guadalentin catchment se spain are formed in a variety of lithologies ranging from schists to marls there are clear differences in valley and channel morphology between these two types gully erosion in schists produces large amounts of clastic material that restricts sediment transport leading to a relatively smooth transition from gullies to hillslopes and to broad alluvial valley bottoms with laterally migrating channels gullies in marls contain only limited gravels so gully extension leads to sharply incised gully heads a two dimensional model has been developed to investigate and simulate the distribution of gully heads in the guadalentin the model runs on a smooth initial surface with an added fractal perturbation without some perturbation of the initial surface or material properties symmetry prevents the formation of any channels fractal perturbation was used here to provide initial irregularities at all scales this paper explores the dependence of model response on the form of the sediment transport law initially sediment transport was considered to be transport limited and so depends on the relationship between wash and creep splash this was modified by i altering the exponents for gradient and area to conform with experimental results ii adding a critical tractive power for the initiation of rillwash iii including a more explicit treatment of mass movements iv including terms to reduce the dependence of the model on the computational grid size v providing a basis for explicitly integrating from individual storms to average long term behaviour and most critically vi introducing the effective bedload fraction ebf as a simplifying concept to allow for the selective transportation of eroded sediment this modification allows the model to represent removal of fines in marl rich catchments without the need to introduce a fully explicit travel distance formulation the steep gully heads and vertical side walls developed in marl catchments in the guadalentin basin are qualitatively well represented by the model preliminary tests showed that steep walled gullies are generated where the ebf falls to below about 0 5 if a tractive power threshold is also introduced gentler headcuts are produced selective transportation is thus seen as the critical determinant of steep headcuts in gully systems

erosion process contribution to sediment yield before and after the establishment of exotic forest waipaoa catchment new zealand abstract the east coast region of the north island new zealand is well known for its severe erosion high sediment yields flooding and sedimentation following extensive deforestation of its indigenous forest during the late 19th and early 20th centuries for six decades thereafter extensive grazing cattle and sheep left a legacy of highly degraded hill country much of which has since been retired and planted in exotic forest primarily to control erosion previous studies have documented the extent of gully erosion calculated erosion rates and sediment delivery from gullies to the channel load within the study basin but this has not been quantified for the more extensive mass movement processes including slump earthflow and shallow landslides additionally the magnitude of the effect of reforestation on sediment load at subcatchment level and ultimately on sediment yield at catchment scale for this combination of erosion processes and over the time frame of a rotation of exotic forest 28 years is unknown for a 140 km 2 study basin located in the headwaters of the 2150 km 2 waipaoa river catchment we establish the contribution to basin sediment load by each of these erosion processes spanning a 50 year period that includes a 28 year reforestation effort we quantified the effectiveness of exotic reforestation as an erosion control strategy by using the mapped extent of each of the erosion processes before planting i e 1939 59 as the benchmark against which any subsequent change in eroded area km 2 was measured based on this process based erosion load was calculated for the pre planting period 1939 59 for the period 10 years after planting commenced 1960 69 and again for the period 1970 88 which marked the completion of planting within the study basin the study basin sediment load is then expressed as a proportion percentage of the measured sediment yield mt y 1 of the wider waipaoa river catchment the net area affected by erosion and erosion rates within the study basin peaked at 10 all processes combined and 28000 4000 t km 2 y 1 respectively during the early planting period 45 of study basin planted at this time gullies contributed 59 of the total sediment load at a rate of 2 3 0 3 mt y 1 slumps 34 1 3 0 2 mt y 1 shallow riparian landslides 6 0 2 0 03 mt y 1 and earthflows 1 0 05 0 08 mt y 1 although reforestation proved effective in stabilising shallow landslides and earthflows the resultant reduction in their contribution to basin sediment load and to overall catchment yield was minimal the greatest reduction in sediment load occurred during the latter part of the reforestation period 1970 88 as the numerous small to medium sized gullies stabilised coincident with canopy closure 8 10 years after planting however the larger gully mass movement complexes failed to stabilise in response to reforestation and they remained the dominant source of sediment contributing an order of magnitude more than slumps and two orders of magnitude more than shallow landslides and earthflows basin scale erosion and denudation rates all processes combined but dominated by gullies for the pre reforestation period averaged 22 000 3000 t km 2 y 1 11 mm y 1 peaked during the early reforestation period at 28 000 4000 t km 2 y 1 14 mm y 1 then decreased to 13 500 2000 t km 2 y 1 7 mm y 1 in response to reforestation and averaged 20 000 3000 t km 2 y 1 10 mm y 1 for the duration of the study period significantly the anthropogenic influence following european settlement of the study basin produced degradation rates an order of magnitude greater than the 1 mm y 1 estimated for the 17 6 cal ka bp post last glacial maximum period retirement of the most severely eroding hill country and subsequent establishment of an exotic forest covering 6 of the waipaoa catchment area effected an overall 62 reduction in the erosion affected area and a 51 reduction in the denudation and erosion rates potentially equivalent to an estimated 12 reduction in sediment yield of the waipaoa river we conclude that a greater or similar level of success could be achieved within three decades of forest establishment elsewhere in the east coast region by specifically targeting gully mass movement complexes particularly in high sediment yielding river systems such as the waiapu catchment

palaeomagnetic and rock magnetic analysis of holocene deposits from the adriatic sea detecting and dating short term fluctuations in sediment supply we present palaeomagnetic and rock magnetic results from five cores collected in the basin of the adriatic sea four cores prad2 4 ks02 246 css00 23 and css00 07 were collected along a shore parallel transect whereas the fifth core amc99 01 was retrieved in the central adriatic in 250 m water depth on the floor of the meso adriatic depression after alternating field demagnetization the natural remanent magnetization nrm directions show a characteristic and primary magnetization of the sediments that is representative of secular variation of the geomagnetic field by combining 14c dating and the ages of magnetic inclination features it has been possible to establish an age depth model for all of the cores precise identification of the secular variation features provides a refined chronology that allows us to quantify short term changes in sediment flux from the adriatic catchment as well as changes in sediment routing within the basin rock magnetic parameters indicate a homogeneous magnetic mineralogy dominated by fine grained magnetite variations in both concentration and grain size related magnetic parameters reflect changes in sediment supply between glacial and interglacial stages as well as changes in environmental conditions selective dissolution of magnetic grains is associated with the formation of sapropel s1 during the first part of the holocene although the duration of the anoxic interval varies between cores a significant modification in sediment supply characterizes the late holocene deposits with a marked increase in sedimentation rate occurring during the last few centuries we interpret this as a far reaching response to the rapid construction of the modern po delta under increasing anthropogenic impact

a palaeomagnetic secular variation record from late pleistocene holocene lacustrine sediments from chalco lake basin of mexico palaeomagnetic secular variation is reported for the past 25 000 years from the lacustrine sequence of chalco lake basin of mexico the rock magnetic and palaeodirectional record is obtained from a 11 27 m core drilled in the central sector of the lake 19 25 n 99 w detailed stratigraphy pollen and diatom studies provide a reconstruction of the environmental evolution the depth time scale transformation is derived from nine 14c dates which give depositional rates of 0 28 mm year for the first 3 5 m and 0 80 mm year between 3 5 m and 11 27 m spectral analysis of intensity and directional records shows low frequency components with characteristic periods of 10 500 3200 3400 2900 3000 1400 1500 and 800 900 years in phase oscillations of inclination and intensity records point to drifting non dipole field anomalies mean inclination anomaly is 2 4 which is similar to results from volcanic rocks of the basin of mexico and hawaii and which support a zonal character of the non dipole field the palaeomagnetic vectors describe characteristic loops with dominant clockwise sense in the intervals 2000 5600 12 000 15 000 and 18 600 24 000 years and dominant counterclockwise sense in the intervals from 6500 to 11 000 and 16 600 18 500 years clockwise vector rotation may represent westward drift of non dipole field anomalies though westward drift may also result in counterclockwise vector motion major declination swings are related to environmental and depositional disturbances and without further confirmation they cannot be considered as geomagnetic variations

a process based model for channel degradation application to ephemeral gully erosion abstract ephemeral gullies are important features of soil erosion yielding large amounts of sediment and dissecting the landscape in spite of their agricultural and environmental importance gully erosion is not usually considered in routine schemes for predicting soil loss an event oriented process based model for stream degradation has been adapted for the description of ephemeral gully erosion the initial channel is considered as prismatic formed in a uniform soil profile defined by the watershed swale and receives upstream and lateral runoff the resulting gradually varied flow is computed by the standard step method whereas the erosion assumed transport limited is attributed first to bed erosion and the remainder is dedicated to the bank erosion at the end of each time step channel shape is redefined accordingly with the computed erosion in each reach a sensitivity analysis revealed that particle density particle size and roughness coefficient are the key parameters a calibration of the model simulating the incision of an ephemeral gully in a small watershed with highly erodible soil allowed a proper estimation of soil loss and the gully cross section shapes along the channel with realistic values of the calibrated parameters