tributary trunk stream relations in a cut and fill landscape a case study from wolumla catchment new south wales australia at the time of european settlement of the south coast of new south wales australia in the mid nineteenth century river courses were discontinuous throughout wolumla catchment within a few decades of settlement intact valley fills had been transformed into incised channels along trunk streams this induced associated patterns of secondary incision into tributary valley fills three of the primary subcatchments in wolumla catchment became fully incised while an upland swamp and a floodout i e sand sheet deposits atop an intact valley floor remain in mid catchment of the fourth subcatchment of the 70 lower order tributaries which join the trunk streams in the four subcatchments 27 have incised 12 of which are discontinuously incised incision of tributary streams in wolumla catchment cannot be explained by subcatchment area and slope relations the position of the trunk stream channel within the valley floor trough is the key determinant of whether or not tributary streams have incised changes to river morphology since european settlement have altered the linkage of tributary streams to the trunk stream impacting directly on the within catchment transfer of water and sediment

gully incision as a key factor in desertification in an arid environment the negev highlands israel abstract gully incision has been eroding the alluvial sediments and loess soils deposited and developed along the valleys in the arid and semiarid regions of israel this phenomenon is critical in the arid regions of the negev highlands where the agricultural fields the main floral biomass and the areas which have the highest grazing value are limited to narrow valleys filled with redeposited loessial sediments the headcut migration and gully development in the region were studied between 1990 and 2001 in three representative drainage basins zipporim revivim and sekher during flood events the runoff penetrates the alluvial cover of the valleys forming vertical headcuts which gradually retreat up the valley the runoff is channeled into narrow gullies preventing the floodwater from spreading over the whole width of the valley the change in irrigation efficiency along the valleys is reflected in a sharp estimated drop of 70 90 in the floral biomass causing the reduction of the range value by 83 99 during the monitoring time interval 1990 2001 the linear gully retreat in the study area ranged between 12 3 and 250 m an average rate of 1 12 22 7 m year 1 for each gully head the process is accompanied by erosion of soil which has high agricultural and range value the total soil losses in these sites ranged between 800 and 9000 m3 at an average rate of 81 818 m3 year 1 for each gully head which is equivalent to 121 1227 mg year 1 during the monitoring period approximately 0 11 0 87 ha of land lost its agricultural and range value in each basin under study at an average rate of 0 01 0 079 ha year 1 since the byzantine period 1400 bp approximately 6 5 ha which is 10 of the land that had high agricultural and range value in the zipporim valley lost its value due to gully erosion no recovery effects of the gully channels were found in the nearby region the soil erosion is generated by a long term natural dynamic change in the soil rock ratio evolving within the drainage basins through time since the termination of the last glacial phase the loessic sediments originally deposited within the drainage basins during the late pleistocene glacial stage are being removed under the present holocene climate in several erosion stages this ongoing phenomenon is causing degradation of soil and biomass and is severely reducing the agricultural and range potential of the region these parameters indicate that an ongoing process of desertification is active in the arid environment of the negev highlands and is advancing in proportion to the headcut retreat rates in the region the soil erosion and headcut retreat have been active in the negev highlands for the last few millennia if these processes continue in the future the negev highlands region will lose its agricultural potential within a few millennia however the fact that the ancient inhabitants of the region implemented successful long term land conservation techniques already 3000 years ago implies that a sustainable land management policy can be adapted to the negev highlands as well as to other semi arid regions in the middle east

impact of terrain attributes parent material and soil types on gully erosion abstract gully erosion is a worldwide matter of concern because of the irreversible losses of fertile land which often have severe environmental economic and social consequences while most of the studies on the gullying process have investigated the involved mechanisms either overland flow incision seepage or piping erosion only few have been conducted on the controlling factors of gully wall retreat an important if not the dominant land degradation process and sediment source in river systems in a representative 4 4 km 2 degraded area of the drakensberg foothills south africa the main objective of this study was to evaluate the relationship between the rate of gully bank retreat gbr and parent material soil types and selected terrain attributes elevation specific drainage area mean slope gradient slope length factor stream power index compound topographic index and slope curvatures the survey of gully bank retreat was performed during an entire hydrological year from september 2007 to september 2008 using a network of pins n 440 from 110 pits both the gully contours and pin coordinates were determined using a gps with a 0 5 m horizontal accuracy n 20 120 the information on the parent material and the soil types was obtained from field observations complemented by laboratory analysis while terrain attributes were extracted from a 20 m dem generated from 5 m interval contour lines the average gbr value for the 6512 m of gully banks found in the area was 0 049 0 0013 m y 1 which considering bank height and soil bulk density corresponded to an erosion rate of 2 30 ton ha 1 y 1 there was no significant difference in gbr between sandstone and dolerite and between acrisols and luvisols despite a weak one to one correlation with the selected terrain attributes r gbr was the highest at hillslope inflexion points profile and plan slope curvatures close to zero in the vicinity of the head cuts and for drainage areas up to 500 m 2 as both situations experience a high removal rate of the soil material produced from the gully bank collapse and protecting gullies from laterally retreating these results could be used to digitally map the more active gully banks for the improved implementation of preventive measures of gully growth if high resolution dems are available there remained however a certain amount of unexplained variability in the data that further research studies on the mechanisms and associated factors of control of gbr could help to address

episodic late quaternary palaeogully erosion in northern kwazulu natal south africa abstract hillslope deposits in northern kwazulu natal south africa are incised by gullies dongas which expose sequences of buried palaeosols developed within a succession of discontinuity bounded colluvial sedimentary units infilled and buried palaeogully topography attests to at least four geomorphic cycles comprising gully cut and fill and palaeosol formation on hillslopes in the region during the past 135 ka past attempts at dating colluvial stratigraphic units were limited to radiocarbon dating of associated palaeosol organic matter and authigenic soil carbonates this study presents a preliminary set of infra red stimulated luminescence irsl age determinations pertaining to deposition of the succession of colluvial units infilling and burying palaeogullies at several sites of stratigraphic geochronological and palaeoenvironmental importance in the region interpretation of the irsl and 14 c dates in the context of cyclical hillslope processes suggests that past episodes of palaeogully erosion and infill were not synchronous and individual palaeosol landsurfaces were diachronous during the late pleistocene

the use of slingram em38 data for topsoil and subsoil geoelectrical characterization with a bayesian inversion we use the bayesian method to invert a simple two layer pedological horizon 1 d with a topsoil and a subsoil of a surveyed site to be assessed we show how the bayesian method is well suited to the determination of topsoil subsoil features and can be used in particular as a tool for the analysis of parameters to be retrieved in terms of information content our approach is devoted mainly to the assessment of topsoil thickness and of topsoil and subsoil conductivities which are provided in terms of probability density functions we first summarize the methodology implemented with the geonics em38 mk2 conductivity meter and discuss the adaptation of field procedures and post processing methods to mitigate the effects of drift and bias we briefly review some non bayesian approaches and then develop the bayesian approach for the context of our geophysical survey highlighting its merits positivity constraints on thickness and conductivity are included in the form of log parameters a priori knowledge based on an objective choice made by the geophysicist is naturally included in the bayesian scheme we discuss the equivalence problem associated with the application of the slingram method to soil structure analysis the survey of a luvisol at the kwazulu natal south africa site of potshini is used to illustrate an ecological application of the slingram and bayesian methods used to define the geo electrical structure of the near surface soil these algorithms have demonstrated their usefulness in mapping the clay content of the bt horizon associated with the control of encroaching trees c 2013 elsevier b v all rights reserved

late quaternary hillslope evolution recorded in eastern south african colluvial badlands abstract infrared stimulated luminescence irsl ages have been obtained from a sequence of sandy colluvial deposits in northern kwazulu natal comparison of the irsl ages on sand sized potassium rich feldspars with radiocarbon dates on a horizon organic matter from buried palaeosols within the colluvial succession shows good agreement between the dating techniques when compared with palaeoenvironmental records the data suggest that the colluvium accumulated during arid stages of the late quaternary whilst pedogenesis repeatedly occurred at intervals of hillslope stability which may reflect periods of greater humidity temperature does not seem to have been a forcing factor in the landscape development extensive colluviation took place during the arid last glacial maximum but the occurrence of several palaeosols indicates that it was a time of fluctuating climatic conditions

soil erosion history in central tanzania based on osl dating of colluvial and alluvial hillslope deposits abstract the irangi hills in kondoa district central tanzania are severely degraded by sheet rill and gully erosion using recently developed optically stimulated luminescence osl dating techniques and a detailed study of the hillslope stratigraphy and soils we have determined the sequence of events that gave rise to this highly degraded landscape two major colluvial deposits have been identified on the slopes the oldest colluvium gave osl deposition dates of 14 700 1600 14 200 1500 and 11 400 1300 years ago these dates coincide with the climatic change from dry to wet conditions which took place during the late pleistocene it is possible that the erosion and deposition of the old colluvium occurred as a response to this change this phase of erosion and deposition was followed by a long phase of stability and pedogenetic alteration of the old colluvium a phase of accelerated soil erosion began not later than 900 years ago as indicated by a dated alluvial fan the presence of which indicates that some deeper gullies already existed on upper pediment slopes at that time the second more recent colluvial deposit gave osl dates of 460 40 590 70 and 660 50 years a major period of gully formation and incision with subsequent fan development occurred sometime between 600 and 300 years ago the recent phase of erosion

the character and age structure of valley fills in upper wolumla creek catchment south coast new south wales australia extensive valley fills at the base of the escarpment in upper wolumla creek on the south coast of new south wales australia have formed from a combination of cut and fill processes the valley fills comprise series of alternating horizontally bedded sand and mud units reflecting reworking of detritus from deeply weathered granites of the bega batholith sand units are deposited as sand sheets or splays on floodplain surfaces or in floodouts that form atop intact valley fill surfaces downstream of discontinuous gullies alternatively sands are deposited from bedload and form bars or part of the valley floor within channel fills organic rich mud units are deposited from suspension in swamps or in seepage zones at the distal margin of floodouts within 5 km of the escarpment valley deposits grade downstream from sand sheet and splay deposition in floodouts to mud deposition in swamp and seepage zones radiocarbon dates indicate that virtually the entire valley fill of upper wolumla creek was excavated prior to 6000 years bp remnant terraces are evident at valley margins the valley subsequently filled between 6000 years bp and 1000 years bp producing valley fills around 12 m deep but no greater than 300 m wide reincision into the valley fill on a scale smaller than the present incision phase is indicated at around 1000 years bp following which the channel refilled portion plans dated from 1865 refer to the study area as wolumla big flat and show large areas of swampy terrain suggesting that the valley fill had re established by this time within a few decades of european settlement the valley fill incised once more upper wolumla creek now has a channel over 10 m deep and 100 m wide in places draining a catchment area of less than 20 km2 1998 john wiley sons ltd

evaluation of luminescence dating procedures applied to late holocene colluvium near st paul s mission natal south africa colluvial deposits provide an interesting challenge for luminescence dating techniques because of the short and varied light exposure histories of the grains prior to deposition results of thermoluminescence tl and infrared stimulated luminescence irsl measurements are presented for two stacked colluvial deposits from natal a radiocarbon date for bulk organic matter in the a horizon of the soil formed within the surface of the lower unit provides a means of assessing the suitability of various luminescence procedures for such material the overlying colluvium contains grains bleached to varying extents as shown by the range of eds for the coarse grain feldspar separate obtained using the single aliquot irsl method for this sample all age estimates either by irsl or tl are too large compared with the radiocarbon age indicating that even the irsl signal was not zeroed in all grains before they were buried the underlying colluvium contains grains bleached more uniformly resulting in a smaller ra

calcium carbonate nodules in soils 13o 16o and 13c 12c ratios and 14c contents abstract 18 o values 13 c values and 14 c ages were determined in ten caco 3 nodule populations collected from soil and paleosols in the israeli coastal plain the selected soils were carbonate free when formed and the nodules in them represent either reprecipitation of carbonate illuviated from overlying horizons descending mode or precipitated from a raised brackish water table ascending mode the 14 c ages represent the times of migration illuviation or eustatic movement both climate related and the stable isotopic conditions reflect the environmental conditions at such times the 13 c values of most populations were found to have a wide range and cannot be used to reconstruct former climates this wide range is attributed to microvariations of pco 2 in the soil because the 18 o ranges in the same samples are usually comparable to analytical uncertainties and because the 18 o mean values follow an age correlated pattern they permit us to place the soils in one of three categories in two cases where nodules were soft both turned out to be young 1000 years and to have wide ranges in 18 o values the latter are apparently due to continual re equilibration with new soil solutions in three cases of the descending mode of nodule formation 12 000 14 000 year old hard nodules had very narrow 18 o whose means reflect the rainfall value at that time the period between 12 000 14 000 years b p is independently known to be one of higher precipitation evaporation ratio and of more intensive soil formation these ascending mode populations of hard nodules had narrow ranges in 18 o reflecting a mixture of sea water and rainfall and all turned out to be 3 000 4 000 years old at this period the sea reached its highest elevation resulting in raising the nearcoast water table

elastic wave propagation in fractured media using the discontinuous galerkin method abstractwe have formulated and implemented a discontinuous galerkin method dgm for elastic wave propagation that allows for discontinuities in the displacement field to simulate fractures or faults the approach is based on the interior penalty formulation of dgm and the fractures are simulated using the linear slip model which is incorporated into the weak formulation by including an additional term that is similar to the penalty term but uses the fracture compliance instead of an arbitrary penalty parameter we have calibrated our results against an analytic solution of fracture induced anisotropy for a set of elongated horizontal fractures and we have evaluated numerical examples that simulate the reflection and transmission of waves at a fracture and at fracture interface waves this method can further be used with models containing intersecting fractures and multiple fracture sets in 2d or 3d domains

paleoenvironmental dynamics of low order paleovalleys in the late quaternary palmas cacador summit surface southern brazil abstract the quaternary dynamics of landscapes in the subtropical continental region of brazil is not still well understood pedostratigraphic records of low order paleovalleys paleovalley heads and 1st and 2nd order paleovalleys of the palmas cacador summit surface serve as important resources for the identification of landscape component responses relief soil sediment and vegetation of plateau areas of southern brazil in the light of environmental changes driven by climatic variations of the late quaternary we integrated litho pedo allo and chronostratigraphic descriptions with carbon stable isotope analysis phytoliths indices and 14c and osl dating we found that at 44 86 ky bp there was a change in the hydrodynamics of 2nd order perennial channels humid climate controlled possibly by tectonics at 28 35 to 23 69 to 28 ky bp regressive pedogenesis in dry climate began with a predominance of erosion by overland flows at 2 60 to 23 69 ky bp full regressive pedogenesis occurred under a continuous climate regime of drier characteristics punctuated by millenary climatic fluctuations to a wetter regime of between 4 60 and 19 77 ky bp echoing the results postulated by the knox s model during this period the most pronounced modifications to the landscape were made with a change in vegetation from campo cerrado to campo limpo with changes in erosion patterns caused first by overland flows and then earthflows debris flows and with the gradual silting filling and burying of gullies valley heads and 1st and 2nd order valley bases since 2 60 ky bp the area returned to a predominance of progressive pedogenesis in wet and cold climates finally we found that at the local scale low order basins

geomorphic changes leading to natural desertification versus anthropogenic land conservation in an arid environment the negev highlands israel the negev highlands in southern israel are currently under an erosive regime causing degradation of soil and vegetation a process which has often been attributed to land mismanagement and overgrazing caused by the local bedouin population to estimate the anthropogenic role in the erosional processes in the negev highlands two similar drainage basins were selected and studied one undisturbed with almost no human impact and the other with intensive human modification including the establishment of roman to early islamic agriculture field observations and luminescence dating indicate that during the late pleistocene glacial period ois 4 and 3 deposition of fluvio loess sediments with minor erosion cycles occurred in the negev highlands severe erosion started during ois 2 and continued into the holocene as the climate shifted during the termination of the pleistocene to the present interglacial phase higher rain intensity generated the incision of gullies and channels into the fine grained alluvial sediments of the previous phase causing extended soil erosion and reducing the natural biomass and the agricultural potential establishment of runoff harvesting farms in the 3rd century interrupted the holocene natural erosion and gully incision and led to the redeposition of up to 3 5 m of fine alluvial loess sediments originating from late pleistocene loess sections this accumulation is not related to any late holocene pluvial climatic phase and is solely the result of farming we conclude that since the end of the pleistocene a dynamic change in the soil rock ratio related to the long term process of adjustment of the geomorphologic system to the holocene climate has been taking place within the drainage basins in the negev highlands the fluvio loess sediments deposited in the region during ois 4 and 3 have been eroding since the latest pleistocene throughout the holocene this process causes degradation of the biomass and agricultural potential and leads onto natural desertification of the region the historical intervention by establishment of runoff harvesting agriculture which as a by product resulted in the accumulation of redeposited loess sediments counteracted the natural trend of soil erosion this was in fact a land conservation act applied by the ancient farmers in the semi arid regions of the middle east deserts this activity and its geomorphic consequences are in contrast to the well documented land degradation trend generated by recent anthropogenic impact on marginal lands elsewhere in any case the human impact either contributing to land degradation or to soil conservation is super imposed on the natural long term trend leading toward desertification

erosion disconformities and gully morphology a threedimensional approach abstract the results of a study of 106 recently formed gullies in bananal in the state of sao paulo brazil is applied in this paper to the analysis of paleogullies detected in the same region bananal is situated in a region where coffee was previously cultivated on the southeastern brazilian plateau the area is characterized by a hilly policonvex relief we observed that gullies tend to cut into hollows on the concave slopes as the slopes in this area were formed by several colluvial deposits setting discordantly we decided to specify the relations between slope geometry and erosion process by the analysis of a three dimensional representation of paleoslope geometry this approach should provide a better insight into the role of hollows and paleohollows in the location of gullies on the slope indeed we observed that gully erosion in the hollows is a common process throughout the upper quaternary of our region this process is in fact responsible for the greatly varying geometry of erosion disconformities between colluvial deposits the morphological patterns of these disconformities led us to associate them with the evolution patterns of active gullies found today in the region

towards chronologies of gully formation optical dating of gully fill sediments from central europe relic gullies are commonplace in the hill landscapes of central and western europe understanding their formation is essential to identify how landscapes respond to environmental change and especially high magnitude rainfall events the relic gully systems were studied intensively but their genesis is still a matter of debate the major problem being insufficient information on the timing of their formation and infilling here we investigate if optical dating of quartz can be used to determine the ages of relic gully systems we studied known age deposits and used quartz grains of different size fractions based on single aliquot regenerative dose protocols equivalent doses were estimated the dose distributions analysed and minimum age models calculated the results show that in many cases optical dating can be successfully applied larger grains seem to be better bleached as optical ages of the coarsest grain size fractions middle sand are in agreement with independent age information from 14c dating and historical sources whereas optical ages of smaller grain size fractions fine sand are overestimates

the palaeoenvironmental interpretation of colluvial sediments and palaeosols of the late pleistocene hypothermal in southern africa colluvial deposits reaching thicknesses of more than 10 m mantle the pediment slopes and choke the streams and river valleys of an area covering about 20 of africa south of the zambezi the sediments are usually deeply incised by gully systems termed dongas which have exposed abundant archaeological remains in the form of stone tools dating from the african middle stone age while the bedrock types in the different areas exhibiting colluvium vary greatly the range in present mean annual rainfall is very narrow being between 600 and 800 mm the grain size characteristics of 55 samples of colluvium show a broad similarity in the percentages of sand silt and clay sized material in the majority of cases the percentage of sand ranges from 45 to 65 silt from 15 to 25 and clay from 10 to 35 the 14c ages of palaeosols in the sediments in swaziland natal and zululand based upon the dating of calcium carbonate nodules and charcoal from cave sediments containing identical stone tool assemblages indicate that colluviation took place between about 30 000 and 12 000 years ago the palaeosols and colluvial sediments of southern africa are indicative of semi arid conditions in which the regolith was stripped from poorly vegetated hill slopes and laid down on gently inclined pediment slopes the age of the deposits supports the contention of several recent workers that the area experienced dry climatic conditions during the last glacial maximum as a result of restricted circulation and reduced sea surface temperatures in the southern ocean

chronology and controls of donga gully formation in the upper blood river catchment kwazulu natal south africa evidence for a climatic driver of erosion dongas gullies and badland type terrain are found extensively across interior south africa but the controls on their formation remain contested establishing the timing of donga formation is essential for developing a clearer understanding of the relative importance of natural e g climatic and human e g overgrazing controls here we present optically stimulated luminescence osl ages for colluvial sediments exposed in the sidewalls of dongas and for tributary fan sediments deposited downslope of dongas in the upper blood river catchment eastern south africa the tributary fan ages enable the timing of donga formation to be established since fan sedimentation is a direct result of upslope donga erosion the osl ages indicate that net colluviation and intervening palaeosol formation occurred from prior to 22 ka until 1 6 ka from 0 89 ka to present there has been a shift to net erosion characterised by widespread donga formation and tributary fan sedimentation contemporary donga formation i

luminescence dating applications in geomorphological research abstract chronological control remains critical to the interpretation of environmental change and to establishing long term rates of geomorphological processes radiocarbon dating will continue to be the central technique for age assessment of carbon bearing sediments deposited in the last ca 40 ka but alternative absolute dating strategies are required for older or non carbon bearing sediments they include uranium series dating of precipitated sediments k ar and ar ar dating of primary volcanic materials and cosmogenic isotopic dating of surface exposure ages an additional family of methods collectively termed luminescence techniques is increasingly providing a basis for the age assessment of detrital sedimentary deposits these methods directly date the deposition of detrital mineral grains typically quartz and feldspar and have been demonstrated to provide accurate deposition chronologies for up to 800 ka although 150 ka is more typical in the past decade a subset of luminescence techniques which employ optical sample stimulation methods called optical dating has made it possible to date samples from a much wider range of depositional systems given that the methods directly date sedimentation they allow direct assessment of depositional dynamism in numerous terrestrial and subaqueous including marine sedimentary systems and have demonstrated particular potential in the elucidation of chronologies from aeolian dune and loess fluvial colluvial coastal and volcaniclastic environments this paper provides a summary of the principles of the luminescence especially optical dating methods and shows how recent developments specifically single aliquot dating procedures have dramatically enhanced the scope and potential of the method the luminescence techniques are increasingly being incorporated into a wide range of geomorphological studies which seek to establish the nature of landscape changes over the past interglacial glacial cycle and beyond

the late holocene geomorphic history of the ethiopian highlands supportive evidence from may tsimble abstract alluvial sedimentary archives contain important geochronological and paleo environmental information on past geomorphic processes in semi arid regions for north ethiopia in particular flashflood sediments transported by ephemeral streams can provide interesting chronological information on late holocene land degradation whether or not impacted by climate or land cover changes upstream here we compare geomorphic records with independent regional records of rainfall regime changes land use cover changes and macrohistory supported by optically stimulated luminescence osl dates for fluvial activity at a sediment sequence in the may tsimble catchment in the northeastern highlands we identified two degradation periods over the past 4000 years one broadly from 1500 500 bce and one from 500 ce onwards at least one prior incision phase is responsible for the stabilized gullies that can be seen on photographs around 1900 and another incision phase is dated to the late 20th century based on all datasets we re interpret the geomorphic history of the highlands land degradation is dominantly determined by a human impact although the impact of this human influence does get amplified during dry spells

late holocene erosion and colluvium deposition in swaziland two major colluvia have been differentiated in eastern southern africa a lower bovu 30 ka and an upper mphunga 14 c dating of pedogenic carbonates in paleosols and on archaeological and faunal inference indicate that deposition of the upper colluvium is climate dependent associated with micropedimentation processes operating under semi arid climatic conditions during the late pleistocene hypothermal ca 30 12 ka mid to late holocene radiocarbon dates of pedogenic carbonates derived from several sites in the upper colluvium are thought to be erroneous four new 14 c dates derived from wood and organic detritus interbedded with the upper colluvium in the mkhondvo valley in swaziland indicate that colluviation occurred throughout the late holocene did not cease at ca 10 12 ka and is ongoing dated profiles are used to provide the first reliable estimates of denudation rates in badland areas in southern africa rates at mkhondvo show rapidly accelerating erosion during the latter part of the past 1 ka these results indicate that colluvium genesis in eastern southern africa is more complex than previously envisaged and though probably strongly influenced by climatic regime is highly sensitive to other factors colluvial stratigraphic models in eastern southern africa need to be reevaluated in the light of this new evidence

luminescence dating of hillslope deposits a review abstract luminescence dating determines the last exposure to light of quartz and feldspar mineral grains and thus the time a sediment was laid down prerequisite is that the sediment grains were sufficiently exposed to light prior to deposition for eolian deposits this seems a fair assumption although exceptions may well exist for other depositional environments light exposure prior to burial is often restricted in duration intensity and spectral composition and may result in an age overestimation recent developments now allow dating of sediments that were exposed to only little light prior to deposition the main developments are single aliquot techniques and statistical tests that allow extraction of valid age estimates even from deposits in which bleached and unbleached grains are mixed these developments in combination with the fact that the great majority of sediments near the earth s surface are not of eolian origin have resulted in the large interest in the luminescence dating of non eolian deposits here we review possibilities and challenges of luminescence dating of colluvial deposits we summarize techniques for the detection and handling of insufficiently bleached sediments a common condition in colluvial deposits we give an overview how luminescence dating has been applied on hillslope sediments for reconstructing landscape response to climate change to analyze past fault activity and unravel human induced soil erosion we discuss sampling strategies and give guidelines as to which techniques are best suited to establish luminescence chronologies for colluvium

controlling factors of gullying in the maracuja catchment southeastern brazil hundreds of gullies vocorocas of huge dimensions up to 400 500 m long 150 m wide and 50 m deep are very common in the small maracuja catchment in southeastern brazil these erosional features which occur with an uneven intensity throughout the area started due to bad soil management practices at the beginning of european settlement at the end of the 17th century and nowadays are still evolving but at a slower rate as surface soils are usually very resistant to erosion the outcrop of the more erodible basement saprolites seems to be an essential condition for their beginning an analysis of well known erosion controlling factors was performed aiming to explain the beginning and evolution of these gullies and to understand the reasons for their spatial distribution data shows that geology and mainly geomorphology are the main controlling factors since gullies tend to be concentrated in basement rock areas with lower relief domain 2 of maracuja catchment mainly at the fringes of broad and flat interfluves at the detailed scale 1 10 000 gullies are more common in amphitheatre like headwater hollows that frequently represent upper quaternary gullies paleogullies which demonstrate the recurrence of channel erosion so gullies occur in areas of thicker saprolites domain 2 in places with a natural concentration of surface and underground water hollows saprolites of the preserved non eroded hollows are usually pressurized confined aquifer due to a thick seal of quaternary clay layer in a similar configuration to the ones found in hollows of mass movement mudflow sites in southeastern brazil therefore the erosion of the resistant soils by human activities such as road cuts and trenches valos or their mobilization by mudflow movements seem to be likely mechanisms of gullying initiation afterwards gullies evolve by a combination of surface and underground processes such as wash and tunnel erosion and falls and slumps of gully walls copyright 2005 john wiley sons ltd

development of gully systems under the combined impact of monsoonal climatic shift and neo tectonic uplift over the chinese loess plateau the surface landscape of the chinese loess plateau features densely developed gully systems gully incision and extension are extremely active over the elevated regions of loess hills ridges and tablelands this paper presents the results of investigations on major gullying phases over the loess plateau during the quaternary the objective is to establish a chronology of gullying events and to examine their relations with monsoonal climatic changes and neo tectonic uplifts results from field observations geomorphologic and pedo stratigraphic analysis indicate that pre historical gullying events are recorded by buried palaeogullies and pedo stratigraphic unconformities preserved in loess sections there were four major gullying phases identified at the loess to palaeosol transitions of l6 s5 l3 s2 l2 s1 l1 s0 in the stratigraphy over the loess plateau the age of a gullying event is closely related with the bottom unit of the palaeosol series in the overlying loess blanket the gullying phases were therefore dated to ca 600 ka 240 ka 125 ka and 11 5 ka respectively by loess chronology this means that gully incision occurred when large scale monsoonal climatic shift met with coincided neo tectonic uplift of the land mass neo tectonic uplift provided the gullying with potential for deep down cutting excessive runoff resulted from precipitation brought on by intensified maritime monsoon was a dynamic forcing of the gullying at the transitions of mis 16 15 8 7 6 5 and 2 1 in response to each wave of gully incision and cross section development occurred the outspreading of the tributary gullies and a new order of gullies formed gully density is therefore increased and the loess land became more dissected hills and ridges these results provide new insights into history of gully erosion and long term landscape development in the semi arid loess regions of the world

transient flow of water to a well in an unconfined aquifer applicability of some conceptual models currently available methods for interpreting data from unconfined aquifers are based on analytical solutions which restrict attention to flow in the saturated zone and account for drainage of water from the unsaturated zone through a source term the parameter specific yield sy is assumed to dictate the total quantity of water that is derivable through the desaturation process it is commonly assumed that flow in the unsaturated zone has little effect on flow in the saturated zone and therefore that all the drainable water is instantly delivered at the water table as it declines in response to pumping in a model proposed in 1954 boulton empirically assumed that the drainable water associated with sy is released gradually at the water table as an exponential function of time this concept of boulton is similar to the notion of first order kinetics frequently used to handle chemical transformations boulton s model is considered by some to have no physical basis numerical experiments performed on sand columns with reasonable properties suggest that vertical drainage of water at the water table due to a falling water table is a time dependent process which is mathematically more complex than a simple exponential relation although boulton did not provide a rational physical explanation his exponential assumption has some merit in that it implicitly provides for a time dependent drainage process which seems to occur in the unsaturated zone however the simple exponential approximation is not adequate to account for what is seemingly a complex process it appears that a physically comprehensive model of radial flow in an unconfined aquifer will combine time dependent drainage from above the water table with vertical components of flow in the saturated zone an additional assumption frequently made is that the well can be treated as a line source results from numerical experiments suggest that caution is in order before neglecting effects of well bore storage in interpreting data from tests on unconfined aquifers

palustrine wetland formation during the mis 3 interstadial implications for preserved alluvial records in the south african karoo abstract dryland alluvial successions across interior south africa are a focus of pedosedimentary research because they provide insights into past hydrogeomorphic changes and improve our understanding of allogenic and autogenic controls on fluvial system behaviour this paper focuses on an alluvial succession preserved within the wilgerbosch river on the great escarpment south africa the pedosedimentary architecture of a calcretized palaeosol formed within an abandoned mis 3 51 39 ka floodplain was investigated using grain size micromorphological xrd and mineral magnetic analyses the primary controls on pedogenesis are inferred and the impacts of their products on subsequent landscape development outlined the biologically dominated calcrete micromorphology is consistent with the rhizogenic calcrete variety which together with xrd grain size and soil magnetic data provides evidence for a palustrine palaeowetland system palustrine wetland systems have been documented across interior south africa but the formation of rhizogenic calcretes in association with these systems has to our knowledge not been reported previously we interpret these palaeowetlands to have resulted from basin wide hydrogeomorphic adjustments rather than localised discontinuous channel and floodout processes magnetic enhancement of the soil column overlying the calcrete compared to the overlying floodplain deposits is indicative of moister climate conditions at 51 ka relative to 39 ka we hypothesise that the longevity of geomorphic quiescence coupled with relatively moist climate conditions in early mis 3 resulted in enhanced soil caco3 accumulation the resultant cementation of this abandoned floodplain deposit accounts for an alluvial record that is dominated by older rather than younger e g holocene deposits despite the narrow valley context