structures caused by repeated freezing and thawing in various loamy sediments a comparison of active fossil and experimental data in this paper the authors present the results of both macroscopic and microscopic investigations on structure development created by repeated ice lensing in various loamy experiments experimental data are compared with observations performed on active forms in high arctic and alpine mountain environments those observations are also compared with phenomena observed in fossil periglacial formations of western europe platy and short prismatic structure formation is bonded to the hydraulic and thermal conditions during ice segregation when a long series of alternating freezing and thawing affects platy structures the fabric evolves also being influenced by slope and drainage conditions cryoturbations frostcreep and gelifluction can appear they are characterized by specific microfabrics which are better developed with an increasing number of cycles this is clear in experiments where hydraulic and thermal parameters are better controlled vesicles are also a prominent characteristic of the surface horizon in experiments and arctic soils the genesis of vesicles is discussed on the basis of new observations and is related to the mechanical collapse of frost created aggregates under the mechanical work of soil air escape during soil saturation by water at thaw

an example of an accretionary forearc basin from northern central anatolia and its implications for the history of subduction of neo tethys in turkey deformed sedimentary sequences of late cretaceous middle eocene age located between the sakarya continent and the anatolian complex have been interpreted as the fill of a forearc basin the history and structure of this basin are critical for understanding the evolution of the neo tethyan subduction in the middle east i test and elaborate upon this interpretation on the basis of three basic outcrop areas of upper cretaceous lower tertiary sedimentary sequences confined to a northeast southwest trending belt in north west ankara these are the alci kinik and orhaniye areas they expose two different sedimentary sequences called alci and orhaniye in the alci area the sequence starts at the base with the continental red clastic rocks on the erosional surface of an underlying ophiolitic melange and continues upward into the shallow marine reefal buildup of the late maastrichtian age the upper half of the alci sequence is separated from its lower half by a local disconformity and dominated by the continental debris flow deposits composed mostly of volcanic material by contrast both the kinik and orhaniye areas are characterized by a thick continuous and coarsening upward sequence overlying conformably the underlying ophiolitic melange the lower half of the orhaniye sequence is dominated by a deep marine flysch its middle part by continental clastic material and the topmost part by the shallow marine reefal buildup lower contact relationships lithologic composition facies distribution internal structures and the regional tectonic settings of both sequences strongly suggest that the above mentioned three outcrops preserve the remnants of a peripheral accretionary forearc basin forming the north northwestern margin of the haymana polath accretionary forearc basin during middle campanian middle eocene time this peripheral basin is here named orhaniye accretionary forearc basin

tectonics and magmatism in turkey and the surrounding area this volume contains 23 papers from a range of international contributors describing recent research into the tectonics and magmatism of turkey and its surroundings this region is sited at the collision zone between eurasia and afro arabia and as such provides an extraordinarily complete and well exposed record of the staged tectonic evolution of this sector of the alpine himalayan orogen the geological history of this area involves separation of continental fragments from the margin of gondwana their migration across the tethyan oceans the subsequent closure of these oceans and finally the development of the neotectonic regime which continues to evolve to the present day such a comprehensive record is relevant to the understanding of collisional zones worldwide the volume is divided into five sections tethyan evolution neotethyan ophiolites post tethyan basin evolution neotectonics and igneous activity the first two sections deal with tethyan oceans whose growth and subsequent closure dominated the geodynamic framework in the mesozoic and cenozoic the subsequent sections deal with more recent geological developments from the balkan peninsula in the west to the transcaucasus in the east that followed consumption of the tethyan oceans there is a broad mix of papers throughout the volume wide ranging review papers on ocean development and extensional tectonics are followed by detailed descriptions of petrology and geochemistry and geographically focused studies on basin evolution specific aspects of extensional and strike slip tectonics and discussions of the relationship of magmatic activity to the tectonic development of the area tectonics and magmatism in turkey and the surrounding area presents up to date results and ideas from a large number of international contributors on a wide range of current research activity in this region it is essential reading for all geoscientists with an interest in both academic and applied aspects of eastern mediterranean geology

factors controlling sediment yield from small intensively cultivated catchments in a temperate humid climate abstract data on sediment yield from 26 small cultivated catchments 10 10 000 ha in central belgium were collected based on sedimentation rates in small flood retention ponds area specific sediment yield varies from 0 4 to 20 6 t ha 1 year 1 for catchments ranging from 7 to 4873 ha various catchment properties were analysed in order to understand this large variation in sediment yield catchment area alone explains 64 of the observed variance in area specific sediment yield although no other parameter could explain more it is concluded that catchment area is not a valid parameter to link with sediment yield overall catchment geomorphology e g presented by the hypsometric integral is much more important in controlling sediment yield the lack of data however made this not very clear a multiple regression model including three morphological catchment properties is a valuable tool to predict total sediment yield t year 1 from catchments in central belgium this model has an efficiency of 0 81 furthermore it was concluded that the within catchment spatial distribution of parameters for instance slope steepness is very important but difficult to obtain one single representative value the use of spatially distributed erosion and sediment delivery models is therefore necessary accurate sediment yield data like the one presented in this study however are needed to validate these models

evolution of the triassic continental margin northwest anatolia abstract the northwest anatolian basement consists of two distinctly different metamorphic assemblages which were juxtaposed prior to the deposition of liassic cover sediments these include the lower and the upper associations the lower association is mainly represented by triassic metavolcanic and associated metasedimentary units together with a slice of ophiolite the upper association rests on the lower association with a low angle thrust fault and is composed of paleozoic or older schists gneisses and phyllites a transgressive succession begins above the basement with permo carboniferous neritic limestones these platform type carbonates were disrupted by rifting during the early triassic at the initial phase of rifting coarse clastics and associated rift type lavas were formed the rift then evolved into an ocean basin which closed at the end of the triassic the continental margin of the triassic basin underwent regional metamorphism initially high t low p it was followed later by a high p low t metamorphic phase during the metamorphism the continental margin units were multiply deformed by north directed compressive stress later on unmetamorphosed triassic successions of the continental margin were thrust northward onto the metamorphosed part of the same continental margin thus the triassic assemblages of northwest anatolia collectively display the dynamics and various structural affects of the deformation recorded in the continental margin and adjacent oceanic unit

changes in sediment flux and storage within a fluvial system some examples from the rhine catchment the rhine river system can look back on a long history of human impact whereas significant anthropogenic changes to the river channel started only 200 years ago the impacts of land use have been felt for more than 7500 years here we review results from several case studies and show how land use change and climate impacts have transformed the fluvial system we focus on changes in sediment delivery pathways and slope channel coupling and show that these vary in time and depend on the magnitude of a rainfall event these changes must be accounted for when trying to use sediments as archives of land use change and climatic impacts on fluvial systems for example human impact is recorded in slope deposits only as long as rainfall intensity and runoff generation do not exceed the threshold for gullying similarly climatic impacts are only recorded in alluvium when both the landscape is rendered sensitive by human activities e g deforestation and rainfall thresholds for gullying are exceeded copyright 2003 john wiley sons ltd

thermoluminescence dating of quaternary red sand beds a case study of coastal dunes in sri lanka red sand beds that occupy extensive tracts of coastal humid tropics have conventionally been considered undatable results of a first successful attempt to provide an absolute chronology to these sediments based on thermoluminescence dosimetry are presented along with a discussion on the importance of an understanding of ambient geochemistry in the application of the thermoluminescence technique the results on the sri lankan coastal region indicate that the sea level in the region may have been affected by regional tectonics during the past 70 000 years based on in situ finds of geometric microliths in the red sands a date of ca 25 000 years is ascribed to them suggesting them to be substantially older than believed so far

the influence of soil properties on the erodibility of belgian loamy soils a study based on rainfall simulation experiments twenty soils from the leuven region were tested in the laboratory with a rainfall simulator their texture varied from loam to loamy sand on the basis of the results obtained they were classified as a function of the runoff and splash erodibility for every soil several properties were determined and tentatively used to explain the classifications based on the runoff and splash erodibility significant negative correlations were found between silt content aggregate stability c5 10 index water content at saturation and cohesion on the one side and erodibility on the other a positive correlation was found between sand content and erodibility

soil erodibility and processes of water erosion on hillslope abstract the importance of the inherent resistance of soil to erosional processes or soil erodibility is generally recognized in hillslope and fluvial geomorphology but the full implications of the dynamic soil properties that affect erodibility are seldom considered in canada a wide spectrum of soils and erosional processes has stimulated much research related to soil erodibility this paper aims to place this work in an international framework of research on water erosion processes and to identify critical emerging research questions it focuses particularly on experimental research on rill and interrill erosion using simulated rainfall and recently developed techniques that provide data at appropriate temporal and spatial scales essential for event based soil erosion prediction results show that many components of erosional response such as partitioning between rill and interrill or surface and subsurface processes threshold hydraulic conditions for rill incision rill network configuration and hillslope sediment delivery are strongly affected by spatially variable and temporally dynamic soil properties this agrees with other recent studies but contrasts markedly with long held concepts of soil credibility as an essentially constant property for any soil type properties that determine erodibility such as soil aggregation and shear strength are strongly affected by climatic factors such as rainfall distribution and frost action and show systematic seasonal variation they can also change significantly over much shorter time scales with subtle variations in soil water conditions organic composition microbiological activity age hardening and the structural effect of applied stresses property changes between and during rainstorms can dramatically affect the incidence and intensity of rill and interrill erosion and therefore both short and long term hillslope erosional response similar property changes linked to climatic conditions may also significantly influence the stability and resilience of plant species and vegetation systems full understanding of such changes is essential if current event based soil erosion models such as wepp and eurosem are to attain their full potential predictive precision the complexity of the interacting processes involved may however ultimately make stochastic modelling more effective than physically based modelling in predicting hillslope response to erodibility dynamics

hydraulic conditions for rill incision under simulated rainfall a laboratory experiment a series of controlled laboratory experiments were conducted in order to obtain precise data on the hydraulic and sediment transport conditions during rill formation tests were carried out using a crusting prone binary mixed soil in a 15 m long flume at an average slope of 0 087 under simulated rainfall rainfall intensities varied from 30 35 mm h 1 and developed about 70 per cent of the kinetic energy of natural rainfall of similar intensity runoff and sediment discharge measured at the downstream weir were strongly influenced by rill forming processes essentially rill incision reduced runoff discharge as a result of increased percolation in rill channels but increased sediment discharge secondary entrainment processes such as bank collapse also increased sediment discharge at the weir knickpoint bifurcation and colluvial deposition however decreased sediment discharge rills always developed through the formation of a knickpoint the critical condition for knickpoint initiation was the development of supercritical flow and waves which mould and incise the bed prior smoothing of the soil surface by entrainment and redistribution of sediment facilitated supercritical flow statistical analysis showed that hydraulic and sediment transport conditions differed significantly in rilled and unrilled flows the relationship between sediment discharge rill erosion and flow hydraulics was found to be nonlinear conforming to a standard power function in the form y axb rills were also associated with significantly increased sediment transport capacities however rill initiation was not clearly defined by any specific hydraulic threshold instead rilled and unrilled flows were separated by zones of transition within which both types of flow occur

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

dating of quaternary lake sediments from the schirmacher oasis east antarctica by infra red stimulated luminescence irsl detected at the wavelength of 560 nm abstract twelve samples from three antarctic lake cores in the schirmacher oasis east antarctica were selected for dating by a method using infra red stimulated luminescence irsl a spectral study of the luminescence signal from coarse grain plagioclase feldspars by a high sensitivity tl osl spectrometer using a ccd camera showed four wavelength maxima and the comparison of the equivalent doses d e measured at these wavelength namely 280 330 410 and 560 nm yielded different values the ages were calculated using d e obtained at 560 nm

optical and radiocarbon dating at jinmium rock shelter in northern australia the jinmium rock shelter is located in the kimberley region of northern australia claims for ancient rock art and an early human presence at this site1 were based on thermoluminescence ages of 50 75 thousand years kyr for quartz sands associated with buried circular engravings pecked cupules and on thermoluminescence ages of 116 176 kyr for the underlying artefact bearing deposits here we report substantially younger optical ages for quartz sand and ages based on measurements of radioactive carbon in charcoal fragments from the occupation deposit using conventional multiple grain optical dating methods we estimate that the base of the deposit is 22 kyr however dating of individual grains shows that some have been buried more recently the single grain optical ages indicate that the jinmium deposit is younger than 10 kyr this result is in agreement with the late holocene ages obtained for the upper two thirds of the deposit from radiocarbon measurements we suggest that some grains have older optical ages because they receivedinsufficient exposure to sunlight before burial the presence of such grains in a sample will cause age overestimates using multiple grain methods whether using thermoluminescence or optical dating

effect of surface roughness on runoff and erosion in a mediterranean ecosystem the role of fire mechanisms at the micro patch scale influencing runoff and erosion processes following a forest fire were investigated the study was conducted in a mediterranean mountainous region with a mean annual rainfall of 690 mm terra rossa soil and vegetation composed of a dense shrubland of pinus halepensis and quercus calliprinos simulated rainfall experiments were carried out on plots representing different intervals of time elapsed since a fire i e immediately after fire two weeks after fire one year after fire unburned plots were also used for comparison at a local scale great variability was found whereby some patches produced high runoff and sediment yields following fire while others did not the conclusion is that the main effect of fires of low to moderate intensity is to produce a mosaic like surface containing both rough patches in which there is almost no chance for runoff generation and relatively smooth patches in which fire can subsequently lead to higher runoff and erosion rates

thermoluminescence dating of fault scarp derived colluvium deciphering the timing of paleoearthquakes on the weber segment of the wasatch fault zone north central utah the timing of middle to late holocene faulting on the weber segment of the wasatch fault zone utah is constrained by thermoluminescence tl and radiocarbon age estimates on fine grained fault related colluvial sediments the stratigraphy in two trenches excavated across fault scarps is characterized by a stack of three colluvial wedges deposited in response to three separate faulting events the oldest of which buried a soil developed on a middle holocene debris flow thermoluminescence age estimates by the partial and total bleach methods and the regeneration method on fine grained colluvium from the trenches agree within 1 sigma and are concordant with the radiocarbon chronology a synthesis of the tl and 14c age estimates indicate that these three faulting events occurred sometime between 4500 and 3500 between 3200 and 2500 and between 1400 and 1000 years ago detailed investigation of a sequence of fine grained scarp derived distal colluvium shows that much of the sediment was deposited during 600 year intervals immediately after faulting the sedimentation rate of colluvium is inferred to increase shortly after faulting and tl dating of these sediments provides additional information to constrain the timing of faulting events

subduction complex of pre jurassic age northern anatolia turkey in northern anatolia a zone of pre liassic orogenic deformation is located mainly between the internal anatolian massifs and the north anatolian fault this belt consists of metamorphic rocks in blueschist greenschist and amphibolite facies and an ophiolitic dynamometa morphic melange the metamorphic rocks represent deformed and metamorphosed oceanic crust and upper mantle whereas the melange rocks originated in diverse environments in abyssal plain trench arc trench gap and forearc environments the evolution of these assemblages is interpreted as a product of subduction probably associated with the closure of the tethys subduction related deformation and meta morphism terminated diachronously from pre late triassic in the west to pre late liassic in the east probably as a result of the diachronous closure of the tethys

holocene slip rate on the sabzevar thrust fault ne iran determined using optically stimulated luminescence osl abstract fault slip rates and the recurrence interval between earthquakes can be determined from reliable dating of deformed sediments we report optically stimulated luminescence osl ages of alluvial gravels fine grained sediments and colluvial deposits associated with the sabzevar thrust fault in northeastern iran six samples of the late quaternary deposits were dated by osl using the single aliquot regenerative dose sar protocol the osl ages indicate deposition of alluvial gravels in the study region between 30 and 9 13 ka followed by a period of fluvial incision which is ongoing at the present day the alluvial deposits have been uplifted by 9 5 m relative to the river level indicating a holocene slip rate of 1 mm yr and a rate of convergence across the fault of 0 4 0 6 mm yr assuming a maximum fault dip of 60 the average interval between large earthquakes on the sabzevar fault will be 3000 years if the fault dips 60 and less if the fault dip is less the last earthquake to destroy sabzevar was in 1052 a d

osl dating of coarse grain fluvial quartz using single aliquot protocols on sediments from ne peloponnese greece abstract optical ages of quartz extracts in holocene sediments from the north eastern peloponnese greece are reported the single aliquot regenerative dose protocol proposed by murray and wintle 2000 radiation measurements 32 57 73 was used to estimate the equivalent dose in these samples a large inter aliquot scatter in d e values was observed for all samples this is ascribed to heterogeneous bleaching of the samples at deposition to estimate a d e for age calculation a technique is suggested based on the analysis of the d e scatter obtained from nine different quartz samples which were artificially bleached and irradiated this procedure is especially useful when the sample quantity is limited the optical age estimates increase with sampling depth an average aggradation rate of 1 5 mm yr is derived using the osl ages this value is consistent with the known uplift rate of 1 2 mm yr

deformation of laminated silt loam due to repeated freezing and thawing cycles the effect of repeated freezing and thawing cycles on an experimentally produced laminated silt loam was studied with the purpose of obtaining more insight into the genesis of macro and microstructures observed in the loessic formations of northwestern europe the laminated silt loam was subsequently subjected to 18 cycles of alternate freezing and thawing the minimum temperature recorded after 11 days of frost was 7 c at a depth of 5 cm and 4 c at 29 cm the underlying sediments compact loam except its upper part and sand always remained unfrozen the experiment reproduced a seasonal superficially frozen ground new structures and microfabrics in the form of vesicles platy structures shear planes and micro undulations were created by ice segregation and thawing mechanical stress and subsequent frost creep the impact of the freezing and thawing cycles is very strong all the laminae being deformed or broken judging by the abundance and the diversity of the structures created freezing is a more important process than simple drying without frost as is evidenced by the range in temperature chosen for the experiment and the low number of cycles these structures do not necessarily require severe climatic conditions to develop unlike frost cracks or ice wedge casts they could develop in winter conditions similar to those present today in the french southern alps

early middle carnian radiolarian cherts within the eymir unit central turkey constraints for the age of the palaeotethyan karakaya complex abstract a chert pelagic carbonate formation within the mass flow deposits of the palaeotethyan karakaya complex melange in ankara has yielded poorly preserved radiolaria the critical fauna paronaella claviformis kozur and mostler canoptum cucurbita sugiyama canoptum inornatum tekin and canoptum levis tekin is the late early carnian to the early middle carnian in age corresponding to unnamed radiolarian zone and tetraporobrachia haeckeli zone and partly to capnuchosphera lowest occurrence zone this is so far the first finding of deep marine sediments from the karakaya complex in primary association with the olistostromes including the olistoliths of high pressure low temperature hp lt metabasic rocks and paleozoic carbonates in the ankara area considering the available data we suggest that during the late triassic the melange forming processes in the south palaeotethyan margin which is of both tectonic and sedimentary character included subduction of mid triassic oceanic islands hp lt metamorphism exhumation and transportation into the foreland basins on the sakarya continental crust

surface seal development under simulated rainfall on an actively eroding surface surface seals developed under controlled conditions were examined micromorphologically to obtain detailed information on the causal processes five tests were carried out using a crusting prone binary soil in a 5 m long laboratory flume at an average slope of 5 under simulated rainfall of 32 mm h 1 for 1 hour three types of surface seal were identified in thin section disruptional seals were 0 3 0 8 mm thick surface layers formed on interrills by raindrop impact due to i rapid destruction of surface aggregates by direct drop impact ii rearrangement of disrupted fragments and textural separates by splash transport and iii compaction and flattening of surface material by continued drop impact sedimentational seals developed under rill and interrill flow with their structure being dynamically dependent upon local flow conditions they were typically 1 mm often with a complex structure of 2 or more sedimentational layers afterflow seals were extremely thin 50 m skin features with strong continuous orientation of clay particles formed by fine particle deposition after rainfall cessation and not by raindrop impact mechanisms as sometimes thought

characteristics and controlling factors of bank gullies in two semi arid mediterranean environments abstract bank gullies are gullies that are formed due to a height drop caused by a terrace or a river bank which develop by headward retreat in erodible hillslopes this study aims i to investigate the morphology of actively eroding bank gullies i e geometrical characteristics resulting from past erosion and active erosion processes shaping the gully and ii to find relationships with environmental site characteristics such as topographical parameters material properties and climate the ultimate goal is to identify the most important controlling factors of past and present bank gully erosion fifty five active bank gullies formed in different lithologies by various erosion processes have been selected in the guadalentin basin and the surroundings of guadix southeast spain for each bank gully site geometrical and topographical parameters of both the channel and the drainage basin were measured erosion features indicating activity at the gully head such as tension cracks plunge pools undercutting fluting piping and rill or sheet erosion on sloping side walls were mapped and samples were taken from distinct lithological layers that were considered to influence the type and intensity of erosion processes a relationship could be shown between the presence of piping and fluting and a number of material characteristics including particle size distribution dispersion behaviour and electrical conductivity on the other hand lithology appeared not to be a differentiating factor on gully development in the long run as expressed by the total eroded volume v this parameter was most strongly related to the drainage basin area in which the entire bank gully had been formed a o explaining 66 of the variance the relationship is v 1 75 a o 0 59 no significant difference was found between regression lines through sub datasets of different soil textural classes finally multiple regression was used to include both topographical parameters and material characteristics in an explanatory and or predictive equation for the total eroded bank gully volume the results of the analyses using the entire dataset including the sites in the guadalentin as well as in the guadix area have been compared with the results for the separate study areas differences are not only related to topographical and lithological characteristics but may also be the consequence of a different climate in the two areas

investigation of relationships between measured field indicators and erosion processes on badland surfaces at petrer spain abstract indicators were obtained to measure and predict rill erosion and mass wasting in biancana and calanchi like badland areas rainfall simulation experiments were used to find a relationship between soil moisture change and sediment concentration behaviour this relationship appeared to be able to show in its role as indicator differences between materials affected by various degrees of rill erosion or mass wasting indicators explaining this relationship are surface characteristics runoff and infiltration characteristics and chemical and mineralogical soil properties from the experimental study it was concluded that the high infiltration capacity in materials affected by mass wasting resulted in an unstable soil and a high degree of erodibility the materials which were more affected by rill erosion or had a continuous crust at the surface were saturated earlier during the experiment than the other materials this saturation caused an increase in runoff the mechanism is explained as the system crossing a threshold after which flow hydraulics at the surface are more important for erosion processes than dynamic soil properties and infiltration characteristics

petrological reconstruction of triassic seamounts oceanic islands within the palaeotethys geochemical implications from the karakaya subduction accretion complex northern turkey abstract subduction accretion complexes provide unique insight into the tectonic assembly of continental margins and oceanic basins as they record the tectonic stacking and juxtaposition of materials derived from distinct tectonic environments the karakaya complex exposed throughout northern turkey is a good example of an ancient subduction accretion complex that includes a number of pre liassic units that characterize the closure of palaeotethys defining the components of this complex is of crucial importance to understanding the geodynamic evolution of palaeotethys in the eastern mediterranean region in this study we explore the geochemistry of metabasic rocks within the karakaya complex redefining and evaluating one of its main constituents known as the nilufer unit new geochemical results combined with previously published data suggest that the nilufer unit is dominated by oceanic island basalt oib and enriched mid ocean ridge basalt e morb type metabasic rocks which are variably enriched in the most highly incompatible elements relative to normal morb n morb associated alkaline oib type basalts are characterized by highly fractionated and variable rare earth element ree patterns la yb n 4 8 16 2 suggesting melting across the garnet spinel transition derivation from a heterogeneous mantle source and or dynamic melting of a homogeneous source similar nb y zr y systematics of spatially associated oib and e morb type samples may indicate involvement of a shared enriched mantle source s combining both geological and geochemical evidence we suggest that the oib and e morb type assemblages defining the nilufer unit represent seamounts and oceanic islands formed on palaeotethyan oceanic crust which was finally incorporated into a forearc accretionary prism during latest triassic and became a component of the karakaya complex

an assessment of human versus climatic impacts on holocene soil erosion in ne peloponnese greece soil erosion is a natural geomorphological process which can be triggered by both natural climate tectonics or both and anthropogenic e g agriculture perturbation of the ecosystem evidence has accrued that the holocene climate experienced large fluctuations in amplitude and suggestions of human impact on the ecosystem provided by the neolithic revolution dating back to the early holocene have been made the question of whether man or climate was the dominant factor responsible for holocene soil erosion remains unresolved to resolve the reasons for holocene sediment redistribution high resolution chronometric data on sediments derived from colluvial and alluvial archives from southern greece were obtained and combined with available archaeological and paleoclimatic data from the eastern mediterranean these data show a significant correlation between sedimentation rates and settlement history climatic fluctuations are only weakly correlated with sedimentation history the results show high sedimentation rates during the early neolithic 7th millennium bc in southern greece suggesting that holocene soil erosion was triggered by human activity and then amplified by enhanced precipitation this would explain the high sedimentation rates during the early neolithic in connection with enhanced precipitation in the eastern mediterranean which continued until the mid holocene

optical dating studies of quartz and feldspar sediment extracts abstract continuing developmental work into optical dating has led to some clarification of the optical behaviour of quartz and feldspar sediment extracts we have verified the key assumption intrinsic to the method that the optical signal is zeroed completely upon exposure to daylight we also show that the rate of zeroing in optical dating is much more rapid than it is in tl dating studies concerned with the extraction of the thermally stable signal from laboratory irradiated samples showed that problems may arise from medium to high temperature preheating of young samples optical alternatives to thermal stabilization were tested using dye and krypton lasers using a krypton laser we have succeeded in obtaining an equivalent dose of 0 0 0 7 gy for the quartz from a modern intertidal sand and an average dose of 120 22 gy for the feldspar extract of a 70 ka sand unit both were obtained using six wavelengths from the infrared to the violet and no dependence on wavelength was found we found that the photon energies of infrared and deep red light can stimulate luminescence in unirradiated quartz and feldspar extracts of sediments this was not expected and suggests that the process of trap emptying is more complex than we had envisioned but implies a far greater than expected degree of technical flexibility for the optical dating method

human settlement and vegetation climate relationships in the greenland stadial 5 at the piovesello site northern apennines italy the gravettian settlements of europe are considered as an expression of human adaptation to harsh climates in southern europe however favorable vegetation climate conditions supported hunters gatherer subsistence and the maintenance of their large scale networks this was also the case of the north adriatic plain and the apennine mountain ridge in italy traditionally considered lacking evidence the northern part of the apennine ridge has recently yielded the early gravettian site of piovesello located at 870 m a s l survey and excavation revealed lithic artifacts in primary position embedded in loamy sediments radiocarbon dating anthracological and extended palynological and microcharcoal analyses have been integrated to reconstruct the palaeoecological context of this camp which was probably positioned above the timberline in an arid rocky landscape bounding the fronts of local glaciers close to their maximum expansion at the time of greenland stadial gs 5 32 04 28 9 ka cal bp human activity left ephemeral traces represented by lithic artefacts charcoal and the introduction of radiolarites from sources in proximity to the site and of chert from very far western sources evidence from piovesello contributes to the reconstruction of human and vegetation ecology during late pleistocene glaciations and also provides hints for the historical biogeography of petrophytic plants and their orographic relics in the northern apennine

formation of the late palaeozoic early mesozoic karakaya complex and related ophiolites in nw turkey by palaeotethyan subduction accretion several pre jurassic tectonic units in nw turkey are crucial to the current debate regarding the timing and direction of subduction of palaeotethys a major ocean that separated eurasia and gondwana in late palaeozoic early mesozoic times the most critical unit is the karakaya complex a deformed low grade assemblage of oceanic origin which comprises a nw verging se dipping stack of tectonostratigraphic units here interpreted as a palaeotethyan accretionary complex the units display lithologies consistent with origins in seamount trench abyssal and rifted carbonate platform settings clastic basin sequences developed on top of the complex other relevant tectonostratigraphic units in the area include ultrabasic rocks of supra subduction zone affinity which tectonically overlie permian carbonate platform units with intervening metamorphic soles and melanges restored structural trends suggest the presence of a southward dipping palaeotethyan subduction zone bordering gondwana related units during the late permian triassic this was probably additional to more important regional northward subduction along the southern margin of eurasia from the eastern mediterranean to the himalayas

early mesozoic subduction in the eastern mediterranean evidence from triassic eclogite in northwest turkey an eclogite forms a 40 m long tectonic lens enveloped in serpentinite within a metabasite phyllite marble unit of permian triassic age in northwest turkey the eclogite consists mainly of garnet omphacite glaucophane and epidote it is associated with other lenses of serpentinite and metagabbro single grain laser probe 40ar 39ar dating of phengites from the eclogite gives ages of 203 to 208 ma corresponding to the triassic jurassic boundary regional geologic considerations also suggest a latest triassic to earliest jurassic metamorphic age for the eclogite and the enclosing metabasite marble phyllite unit the eclogite along with serpentinite and gabbro lenses were probably emplaced as diapirs into the metabasite phyllite marble unit during late triassic subduction the eclogite provides evidence for the often elusive triassic subduction history of the paleo tethys in the eastern mediterranean area

a consistency index and rainwash mechanisms on belgian loamy soils the effects of soil crusting in belgium are particularly conspicuous on the loamy plateaus and hill regions of southern flanders brabant and hesbaye field observations made at the end of rainy winter seasons permitted the making of a simple distinction between a stable soils showing crusting on less than 50 per cent of their total surface without any evident slope wash and b unstable soils crusting over more than 50 per cent of the total surface with evident rainwash and basal colluviation the atterberg limits have been examined for both soil types it was found that the upslope part of the liquid limit curves in the range of low consistencies high water contents is steeper for stable than for unstable soils so a distinctive consistency index c2 10 was deduced from the liquid limit curves which may be used for prediction of the relative sensitivity of topsoils for crusting stable well structured clods are more hydrophobic than unstable material this was made clear by wettability tests under a rain simulator therefore more water must be added to remolded stable material to lower its consistency as is shown by the liquid limit curves crustability decreases and c5 10 values increase with increasing clay and organic matter contents as one would expect stable soils are well aggregated but rain simulator tests also showed that the detachment of this material by raindrop impact is high therefore crumbs and clods of stable soils are relatively more sensitive to splash erosion their erosion results from the ejection of stable aggregates clods of unstable topsoils are compacted and flattened by raindrop impact which causes internal liquefaction micromorphological analysis indicates that typical stable topsoils originate from well structured ap horizons and from bt horizons of grey brown podzolic soils alfisols laminated silt and mudcrust fragments characterize unstable topsoils which originate at least partly from slopewash deposits the external stability of both stable and unstable clods is increased by compaction and by surficial concentration of gravel coarse sands root and other plant fragments thin sections of unstable material show the internal collapse of structures due to liquefaction a clear distinction must be made between the structural stability and the erodability of topsoils

tectonic units of the alpine collision zone between eastern alps and western turkey abstract we present a map that correlates tectonic units between alps and western turkey accompanied by a text providing access to literature data explaining the concepts used for defining the mapped tectonic units and first order paleogeographic inferences along strike similarities and differences of the alpine eastern mediterranean orogenic system are discussed the map allows 1 for superimposing additional information such as e g post tectonic sedimentary basins manifestations of magmatic activity onto a coherent tectonic framework and 2 for outlining the major features of the alpine eastern mediterranean orogen dinarides hellenides anatolides and taurides are orogens of opposite subduction polarity and direction of major transport with respect to alps and carpathians and polarity switches across the mid hungarian fault zone the dinarides hellenides taurides and apennines consist of nappes detached from the greater adriatic continental margin during cretaceous and cenozoic orogeny internal units form composite nappes that passively carry ophiolites obducted in the latest jurassic earliest cretaceous or during the late cretaceous on top of the greater adriatic margin successions the ophiolites on top of composite nappes do not represent oceanic sutures zones but root in the suture zones of neotethys that formed after obduction suturing between greater adria and the northern and eastern neotethys margin occupied by the tisza and dacia mega units and the pontides occurred in the latest cretaceous along the sava izmir ankara erzincan suture zones the rhodopian orogen is interpreted as a deep crustal nappe stack formed in tandem with the carpatho balkanides fold thrust belt now exposed in a giant core complex exhumed in late eocene to miocene times from below the carpatho balkan orogen and the circum rhodope unit its tectonic position is similar to that of the sakarya unit of the pontides we infer that the rhodope nappe stack formed due to north directed thrusting both rhodopes and pontides are suspected to preserve the westernmost relics of the suture zone of paleotethys

reconstruction of late holocene slope and dry valley sediment dynamics in a belgian loess environment to unravel the evolution of a dry valley in the belgian loess area soils and sediments along a slope catena were studied in detail a 67 m long trench was opened from the upper slope to the centre of the valley bottom the exposed soils and sediments showed evidence of severe soil erosion and other human disturbances that significantly changed the valley topography the early holocene slope gradient was up to 25 whereas now it is less than 10 in the thalweg a remnant of the early holocene soil was found underneath colluvial deposits which were more than 3 m thick a chronology for the valley evolution was established based on ams 14c dating of charcoal fragments and optical dating of colluvial sediments the first sediment deposition occurred in the early iron age with an average sedimentation rate of approximately 3 4 1 3 t ha per yr this increased to c 5 4 2 2 t ha per yr during the roman period and further to 18 0 2 2 t ha per yr in the middle ages although sediment accumulation in the

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

biostratigraphic constraints on formation and timing of accretion in a subduction complex an example from the franciscan complex of northern california the determination of the total age coverage of pelagic bedded chert is particularly important in studies of ancient accretionary complexes because the time span represents the minimum travel time of an oceanic plate before accretion at an island arc or continental margin the yolla bolly terrane of the franciscan complex consists of rare metabasalt overlain by bedded radiolarian chert which in turn is overlain by metagraywacke and subordinate slaty mudstone and conglomerate the bedded chert ranges in age from aaleian early middle jurassic to tithonian latest jurassic a lithologic gradation from pelagic bedded chert through hemipelagic siliceous mudstone occurred during the tithonian and thus marks the arrival of the oceanic sediments at the continental margin the tithonian age also agrees with previously reported tithonian to valanginian early cretaceous fossils in the overlying terrigenous metagraywacke both chert and metagraywacke are intruded by gabbroic sills suggesting off ridge volcanism

accreted oceanic materials in japan abstract the phanerozoic circum pacific orogenic belts contain numerous ocean derived materials accreted through plate converging processes japanese islands in particular display various kinds of oceanic materials of different origins including fragments of seamounts oceanic reef limestone morb like rocks and oceanic mantle and pelagic sediments the compilation of these rocks in many subduction complexes of late permian to the present led to following conclusions accretion processes work effectively only for materials primarily composing the upper portion of subducting oceanic crust i e layer 1 and layer 2 many fragments of seamount with alkali basalt 600 hot spot seamount 26 oceanic reef limestone 291 morb like basalt 200 and numerous cherts more than 1000 are recognized as ancient oceanic materials accreted to the japanese islands however gabbros and mantle materials of layer 3 and lower parts of the oceanic lithosphere scarcely occur in subduction accretion complexes except for a few examples of back arc basin or fore arc origin accretion occurs episodically in southwest japan oceanic materials were accreted intermittently in 1 a end permian 2 b middle late jurassic 3 c late cretaceous times 4 d at ca 50 ma and 5 e in miocene times while in northeast japan and hokkaido this occurred in b middle late jurassic c late cretaceous and f early cretaceous times in contrast to the general belief on accretion of younger oceanic plates the majority of japanese subduction accretion complexes were formed during the subduction of plates up to 160 ma old the accretionary events in end permian and middle late jurassic times coincide with northward collision of ancient island arcs oceanic rises or seamount chains of hot spot origin with the asian continent accretion relevant to subduction of older plates may be controlled by the collision subduction process of these topographic reliefs on an oceanic plate in addition the chronological coincidence with the continent collision amalgamation between the sino korean and siberian platforms and between the sino korean and yangtze blocks also implies collision induced voluminous supply of elastics from back arc regions and its contribution to the formation of huge accretionary complexes accreted fragments of ancient seamounts are much smaller than the average size of modern seamounts this implies that most parts of a colliding seamount are not accreted but subducted together with the underlying oceanic crust to much deeper levels with respect to the metamorphic grades for japanese subduction complexes oceanic materials have less than 1 vol in the zeolite facies 15 20 in the prehnite pumpellyite metagraywacke facies and ca 30 in the greenschist glaucophane schist facies and albite epidote amphibolite fades this relationship indicates that the major process for landward accretion of oceanic materials is not off scraping or sedimentary mixing at the trench but underplating subcretion at much deeper levels of a subduction zone