identification of neolithic to modern erosion sedimentation phases using geochemical approach in a loess covered sub catchment of south moravia czech republic abstract a colluvial soil with a 380 cm deep humus enriched horizon was studied in a loess region of south moravia czech republic which is characterized by a strong soil material re deposition distribution of soil properties within the colluvial soil profile was used for distinguishing the different sedimentation phases and understanding colluvial soil formation the colluvial profile is stratified into different horizons distinguishable by a specific distribution of basic soil properties soil organic carbon content carbonate content or soil reaction in the profile low organic carbon content 0 6 0 8 and increased carbonate content up to 8 in the upper 260 cm indicates a rapid change of the soil cover and significant admixture of loess parent material in the sediment an abrupt increase of organic carbon content 2 and no carbonates between 300 and 380 cm is evidence of a buried chernozem at this depth antropogenically induced substances such as pesticide residues or increased nutrient content connected to agricultural practices enables the detection of sedimentation periods the peak ddt content up to 0 04 mg kg at the depth of 50 150 cm clearly delineates the material sedimented in the 1950s 1970s and material sedimented in earlier or later stages the same trend can be traced in phosphorus and potassium content given by intensive use of fertilizers at a given time period the potential use of lead and cadmium as another indicator of anthropogenic influence at some stage of soil sedimentation was not proven due to their low concentration in the colluvial profile three phases of soil erosion and sedimentation were distinguished each reflecting different land use and intensity of agriculture the highest amount of soil material 2 m deposited in the colluvial profile can be attributed to the last and shortest erosional phase corresponding to intensive agriculture and massive land consolidation in the last 70 years

tectonic denudation of the shuswap metamorphic terrane of southeastern british columbia large scale over thrusting and regional extension are both known to have been operative within the shuswap metamorphic terrane of the southern omineca belt the monashee core complex of the northern shuswap terrane is interpreted to be a crustal scale duplex that was developed during late mesozoic shortening and thickening of the crust uplift of the monashee complex caused by basement duplexing is estimated to have been in excess of 25 km late cretaceous overthrusting of high grade metamorphic and related plutonic rocks during later stages of uplift and basement duplexing led to weakening of the crust and to gravitationally driven extension of a regional crustal welt shuswap culmination denudation and spreading of this uplifted metamorphic terrane are attributed to displacements across listric normal shear zones and faults localized along the outward dipping flanks of the shuswap culmination total extension across the shuswap culmination at the northern end of the monashee complex is estimated to be no greater than 30 this model of denudation and gravity induced spreading is extrapolated southward into the valhalla and okanagan regions where extension may be far more significant

soil aggregate stability within morphologically diverse areas abstract knowledge of spatial distribution of soil aggregate stability as an indicator of soil degradation vulnerability and its possible prediction are required for many scientific and practical environmental studies the goal of our study was to provide a model for predicting soil aggregate stability within morphologically diverse areas where soil properties have been affected by soil material redistribution due to erosion the study was performed on a study site 6 ha area in the loess region of southern moravia czech republic haplic chernozem which is an original dominant soil unit has been transformed into different soil units eroded phases of chernozem regosol colluvial chernozem and colluvial soil 36 sampling spots were selected in order to represent diverse soils the following soil properties were measured oxidable organic carbon content cox caco3 content phh2o phkcl soil particle density s bulk density d porosity p actual field soil water content field content of iron and manganese in ammonium oxalate extract feo and mno and dithionite citrate extract fed and mnd and mass specific magnetic susceptibility lf and hf the aggregate stability was assessed using various tests to study different disruption mechanisms terrain attributes were derived from a digital elevation model in general the lowest soil aggregate stability was observed on steep slopes which were highly impacted by soil erosion the highest aggregate stability was measured on soils sampled at relatively flat upper parts which were less influenced by erosion processes higher stability was also obtained on toe slopes where the sedimentation of previously eroded soil material occurred the simple correlations revealed that characteristics resulting from the tests studying aggregate slaking due to the compression of the entrapped air water stable aggregate index and coefficient of vulnerability from fast wetting test were positively impacted by the cox p feo mno fed mnd lf and hf values and negatively by the d value the soil aggregate stability was also negatively influenced by the plan and total terrain curvatures i e larger aggregate stability was measured at concave parts in comparison with that at convex parts almost no statistically significant relationships were found in the case of the tests evaluating either aggregate disintegration caused by the micro cracking due to the different swelling or by the physico chemical dispersion due to the osmotic stress or the mechanical aggregate breakdown the multiple linear regressions resulted in the model for estimating the wsa index using the cox content total terrain curvature and actual field soil water content field in this model the cox content positively and the total terrain curvature and field value negatively influenced the value of the wsa index since cox was positively related with iron content and thus also with the magnetic susceptibility the alternative model was proposed for less costly and time consuming wsa estimation the wsa index may be predicted by combining the mass specific magnetic susceptibility lf and hf total terrain curvature and actual field soil water content field

intracontinental contraction in western north america continuity and episodicity contraction in the western north american cordillera exclusive of accreted terranes occurred over a remarkably uniform duration of 110 15 m y between approximately 165 and 55 ma the amount of contraction as much as 285 km was similar from southeastern british columbia to northern nevada and utah although irregularly partitioned between hinterland fold and thrust belt and rocky mountain foreland time averaged contraction rates are 1 5 to 2 5 mm yr the contraction however appears to have occurred in pulses with cumulative duration of 75 m y implying rates during active periods of 2 5 to 3 8 mm yr displacement rates as high as 6 mm yr on some thrust faults suggest episodicity within pulses episodic contraction on 10 to 30 m y intervals corresponds well to episodicity in relative plate motion suggesting rapid response of intra continental kinematics to plate boundary interactions the relationship is nevertheless indirect possibly influenced by the position and number of plates partitioning of displacements across accreted terranes and crustal structure

evolving geographic patterns of cenozoic magmatism in the north american cordillera the temporal and spatial association of magmatism and metamorphic core complexes four maps are presented here that show the location and extent of magmatic fields between eastern alaska and northern mexico during the successive time intervals of 55 40 40 25 25 10 and 10 0 ma and four others show the distribution of metamorphic core complexes during the same cenozoic time intervals the maps are based on u s geological survey and canadian cordilleran data bases contining about 6000 isotopic dates and extensive literature review for nearly 60 ma the development of metamorphic core complexes has coincided with the locus of a really extensive and voluminous intermediate composition magmatic fields the association is suggestive of a close link between magmatism and core complex formation namely that magma directly and indirectly lowers the strength of the crust magmatism thus controls the location and timing of core complex formation the stresses responsible may be inherited from mesozoic crustal thickening locally created by uplift and magmatic thickening of the crust and imposed by the global pattern of plate motions and driving forces since the miocene rates of magmatism extension and core complex formation have declined the modern basin and range province is not a suitable model for the situation that existed during major magmatic culminations the singular event of early miocene time the merging of two large magmatic fields extinguishing the laramide magmatic gap explains several disconnected observations the hyperextension episode of the colorado river corridor rapid reorientation of stress patterns across much of western north america and subsequent rapid tectonic movements in california magma triggered breakup of western north america lithosphere coincided with development of the san andreas transform system thermal destruction of the laramide magmatic gap created a california microplate about 22 ma ago that moved rapidly away from north america thus two plate tectonic processes thermal destruction of the lithosphere bridge and northward growth of a transform system interacted to produce miocene and later tectonic patterns and events

influence of pedon history and washing nature on luminescence dating of holocene colluvium on the example of research on the polish loess areas abstract although colluvium is a valuable record of past human impact there is a lack of a precise method of age determination the luminescence method could be used but the basic difficulty is partial bleaching of quartz grains in this study colluviums from southern poland were investigated using the osl method all examples for this study are colluviums deposited on holocene fossil soils in dry valleys in all cases the area of research has been very well recognized in terms of archaeological significance the youngest 50 year old colluviums were also studied using the 137 cs method the obtained luminescence results are in stratigraphic order and in good agreement with archaeological data and 14 c dating the dated sediment samples are usually well bleached this is not due to transportation on the slope but rather from mixing by ploughing or bioturbation osl dating results together with distributions may therefore be helpful in determining the origin of colluvium this is not possible by examination of macroscopic lithogenetic characteristics as the diagnostic sedimentary structures of colluvium were destroyed by postsedimentation soil processes the results confirmed that soil erosion started in the neolithic

two dimensional modeling of the p t t paths of regional metamorphism in simple overthrust terrains quantitative modeling of metamorphic p t t paths in thrust belts has so far been limited to one dimensional simplification we have developed a two dimensional time dependent finite element procedure capable of tracing and updating fault and strata boundaries during faulting for modeling thermal evolution of overthrust terrains we show that the two dimensionality of an overthrust and the speed and duration of thrusting have significant effects on the p t t paths of rocks in orogenic belts the results suggest that petrological studies of p t paths of rocks from different lateral positions in an orogenic belt along with two dimensional modeling procedure can put strong constraints on models of regional tectonic processes

crustal shortening and eocene extension in the southeastern canadian cordillera some thermal and rheological considerations metamorphic core complexes in the southeastern canadian cordillera were formed during eocene crustal extension shortly within a few millions of years after late jurassic paleocene crustal shortening thermal rheological modeling constrained by geological and geochronological studies of the valhalla core complex and other core complexes in this region is used to investigate two major problems concerning the formation of these core complexes 1 the dynamic links between crustal shortening and extension and 2 the cooling history and unroofing rates during extension thermal rheological effects associated with crustal shortening are integrated through the history of crustal compression since crustal shortening in this region was a long and slow process and cannot be treated as an instantaneous event our results suggest that crustal shortening may have played an important role in eocene extension in the southeastern canadian cordillera by 1 producing a thickened and therefore unstable crust and 2 thermally weakening the lithosphere however heat generated by crustal shortening is not enough to account for the thermal state of the valhalla complex and additional heat sources at depth may be necessary we then investigate thermal evolution during extension in both a simple shear model and a progressive pure stretching model we show that the geotherm in an extensional region is time and space dependent and is affected by many variables including the preextensional thermal history and the mode of extension thus caution needs to be exercised when inferring unroofing rates from thermochronologic data the cooling history of the valhalla core complex may be explained by unroofing at rates of 1 2 mm yr

development of gullies and sediment fans in last glacial areas on the example of the suwalki lakeland ne poland abstract the density of gully network in the suwalki lakeland northeastern poland with typical last glaciation relief is 0 2 km km2 on average and locally reaches 1 2 km km2 most gullies are isolated but sporadically they create dendritic patterns the larger gullies are developed along dellies bowl shaped dry valleys or melt out valleys the smaller and shorter gullies occur on the slopes of melt out depressions and tunnel valleys ages of peat covered by fans at the mouths of larger gullies indicate that gully erosion started between 3520 70 to 2240 100 bp two different units build the fans and infilled the gullies the older unit in the lower part of fans is up to 5 m thick contains sand and gravel that generally originated from the bottom and bank erosion of the gullies and resembles alluvium the younger unit about 2 3 m thick consists of colluvium the fans at the mouths of smaller and shorter gullies are mainly built of colluvium the maximal grain diameter in both units is similar which testifies to a similar intensity of extreme rainfalls the analysed sediments have different characteristics which indicate that the source material and depositional changes are linked to forest clearance and farmland expansion starting in the 7th century ad and continuing in the middle ages

human induced soil erosion and gully system development in the late holocene and future perspectives on landscape evolution the myjava hill land slovakia in humid climate zones like central europe past soil erosion and gullying are strongly connected with agricultural expansion and extreme soil erosion events often play an important role in land abandonment this paper provides a case study to demonstrate the interaction between land use soil erosion floodplain development and land use changes in a 0 order catchment in the babikovce catchment myjava hill land situated in western slovakia sedimentological pedological geoarchaeological and historical data indicate two main periods of intensive hillslope erosion and gullying since the high middle ages in particular a few extreme precipitation events or rapid snowmelts caused intensive runoff events and gullying on cleared land the formation of the gully system and fan deposits in the babikovce catchment and other areas also forced the occurrence of intensive muddy floods and caused floodplain aggradation and meander changes along rivers in the myjava hill land as a result the development of the dense network of permanent gullies in the myjava hill land can be associated with the transformation of woodland into farmland and later land abandonment today the area is highly truncated by soil erosion and very difficult to farm

lithoprobe seismic reflection structure of the southeastern canadian cordillera initial results nearly 270 km of crustal seismic reflection data obtained by lithoprobe in the southern canadian cordillera provide a geometric link between the rocky mountain foreland thrust and fold belt the purcell anticlinorium and the extensional regime superimposed on the crystalline core zone autochthonous north american basement and its overlying deformed and transported cover can be traced from the thrust and fold belt beneath the rocky mountain trench to 20 km depth beneath the central part of the purcell anticlinorium the purcell anticlinorium is cored by foreshortened proterozoic supracrustal rocks that were carried northeastward on a series of west dipping imbricate thrust faults these faults crop out within and east of the anticlinorium and converge downward with subhorizontal detachments above the autochthonous north american basement beneath the western purcell anticlinorium and kootenay arc reflections associated with the purcell stratigraphy and its underlying crystalline basement terminate at about 20 km depth and may be truncated against the east dipping eocene slocan lake fault zone the slocan lake fault zone is clearly imaged from the surface to about 12 km depth and can probably be followed discontinuously to about 25 km depth a west dipping high amplitude reflection from beneath the valhalla gneiss complex outlines the domal geometry of the complex and is probably related to an east verging compressional shear zone

eocene structural development of the valhalla complex southeastern british columbia the valhalla complex a cordilleran metamorphic core complex is a 100 km by 30 km structural culmination within the omineca belt of southeastern british columbia it comprises sheets of granitic orthogneiss ranging in age from 100 to 59 ma with intervening paragneiss of uncertain age and stratigraphic correlation the complex is roofed by the ductile valkyr shear zone and the ductile brittle slocan lake fault zone the upper plate comprises lower grade metasedimentary rocks intruded by middle jurassic plutons the valkyr shear zone and the slocan lake fault zone deform 62 and 59 ma granitic sheets in their footwalls the easterly directed valkyr shear zone is a 2 to 3 km thick zone of distributed ductile strain which is arched over the complex and is exposed around the periphery on the northern western and southern margins the shear zone was active between 59 and 54 ma under amphibolite facies conditions the juxtaposition of upper and lower plates with different structural and metamorphic histories indicates that the valkyr shear zone is a significant structure with large displacement there is evidence to support an easterly rooting direction consistent with an extensional origin its surface breakaway is suggested to be west of the valhalla complex the slocan lake fault zone on the eastern side of the complex is a gently 30 easterly dipping ductile brittle normal fault which roots to the east it was active between 54 and approximately 45 ma and truncates the valkyr shear zone timing and structural relationships indicate that the valkyr shear zone and the slocan lake fault zone are genetically related movement on the ductile valkyr shear zone arching of the complex and displacement on the slocan lake fault zone occurred as a continuum in early to middle eocene time this paper documents the presence of significant eocene ductile strain in the valhalla complex and suggests that the role of extension in this region is more profound than had been previously recognized

pedological analysis as a key for reconstructing primary loess relief a case study from the magdalenian site in klementowice eastern poland abstract the subject of the study was a gentle and smooth loess slope featuring a magdalenian culture site located near the northern edge of the loess belt in eastern poland based on the probing of 130 soil profiles across a 10 10 m mesh within an area of 1 2 ha the land surface after the deposition of weichselian loess was reconstructed soil mapping indicated the patchwork character of the present soil cover which consists of luvisols of varying degrees of transformation resulting from agricultural use partly eroded and buried soils co occur in the upper part of the ridge flat non eroded soils in the middle part and eroded soils in the lower part in the archaeological site area with buried soils at the foot of the slope the thickness of the primary soil cover was reconstructed by means of geostatistical analyses this was used to reconstruct the primary undulating land relief characterised by numerous small convex forms small hillocks and hummocks and concave forms closed depressions and slope troughs these forms were levelled out by soil erosion in the course of agricultural use the planation of relief caused a decrease of the mean inclination by 25 and elevation difference by 13 the greatest changes occurred on the ridge flat where the denudation of small hillocks and the filling of closed depressions took place local inclinations decreased by up to fourfold and in some places the inversion of slope exposure occurred during the 210 years of agricultural use the eroded surfaces subsided by an average of 0 32 m and at most by 0 92 m which corresponds to an average of 1 5 mm and 4 3 mm per annum respectively less than 50 of the eroded soil material was deposited within the investigated slope most of the material was carried off beyond it the accumulated surface however is 2 5 times smaller than the eroded surface hence the accumulation indicators are slightly higher than the erosion indicators

high resolution gully erosion and sedimentation processes and land use changes since the bronze age and future trajectories in the kazimierz dolny area naleczow plateau se poland abstract this paper presents the results of 40 years of research on the gully system in the doly podmularskie catchment 0 35 km in size which is situated in the south western part of the loess covered naleczow plateau in se poland topographic stratigraphic and pedologic investigations and monitoring of a tributary gully gully area 0 7 ha catchment 2 5 ha were combined with historical archaeological and palaeoecological records the results reveal a long and complex history in terms of the temporal and spatial extent and the impact of land use on gully erosion and the long term feed back mechanisms between land use changes and natural processes since the end of the pleistocene phases of gully erosion and subsequent filling occurred in the bronze age and around the 10th to 11th centuries the most severe deepening and expansion of the gully took place in the 17th century the results also show that field structures and land use intensity had a significant influence on the frequency and magnitude of run off soil erosion piping and landslide events the last significant erosion phase started in the mid 19th century with renewed headward retreat and down cutting within older gully fills today most of the catchment is either forested or the land is covered in berry shrubs in the future the area will continue to produce sediments because of the steep slopes and because there are still areas of bare soil with a low resistance to erosion a legacy from past land uses which will remain a factor affecting soil erosion and sedimentation processes in the future this study is an example of how important it is to observe and understand slow geomorphologic processes and rare extreme events in the light of land use changes when investigating long term human environment interactions

evolution of lithospheric strength after thrusting modeling of an eroding thrust belt indicates that immediately after thrusting the lithosphere is about twice as strong as unthickened cratonic lithosphere but after 10 to 20 m y it becomes weaker than cratonic lithosphere reaching a minimum of 40 to 70 of cratonic strength 30 to 100 m y after thrusting this may explain why rifting of thrust belts commonly occurs several tens of million years after thrusting ceases relative weakening results from 1 elevation of the geotherm caused by burial of radioisotope enriched surface rocks and 2 replacement of strong mantle rocks by weak crustal rocks in the lithospheric column low denudation rates enhance weakening by allowing radioisotope enriched rocks to remain buried longer our modeling indicates that 1 magmatism after thrusting is favored by high concentrations of heat producing elements in the lower plate and by slow denudation rates and 2 factors that affect denudation rate such as climate and the development of external drainage can significantly influence evolution of a thrust belt

investigation of vegetation history of buried chernozem soils using near infrared spectroscopy nirs abstract the environmental conditions of the evolution of chernozems in central europe have not been satisfactory explained in this paper seven buried chernozems were investigated using near infrared spectroscopy nirs in order to get information about the former vegetation cover near infrared nir data were collected from organic matter of recent natural grasslands and forests the spectra from these two groups of soils were perfectly discriminated by a multivariate statistical analysis the statistical model was applied on the buried soils there are four types of vegetation development within the chernozems before the burial comparison to other paleoenvironmental proxies shows no major contradiction and confirms the potential of the nirs as a paleopedological proxy the identified changes of vegetation are from grassland vegetation to forest vegetation and vice versa these changes bring new data to the discussion about the pedogenesis of chernozems according to the radiocarbon dating buried soils developed and were preserved not only in the preboreal and the boreal but also in later phases of the holocene

lithoprobe crustal reflection cross section of the southern canadian cordillera 1 foreland thrust and fold belt to fraser river fault seismic reflection data from the south central canadian cordillera covering the interval from the easternmost metamorphic core complexes near arrow lakes to the fraser river fault system along the fraser river reveal a highly reflective and complex crust the base of the crustal reflectivity interpreted as the reflection moho is clearly delineated by a continuous sharp boundary that is essentially planar and slopes uniformly over a distance of 250 km from about 12 0 s in the east to about 10 5 s in the west this virtual lack of relief at the base of the crust contrasts sharply with surface structures that involve 25 km or more of structural relief some of these surface structures can be readily correlated to structures that are outlined by the reflection data and that can be followed into the middle and lower crust even though part of this area was subjected to large amounts of eocene extension the crust is not divisible into transparent upper and reflective lower layers as it is in parts of the u s cordillera three structural culminations the monashee complex the vernon antiform and the central nicola horst are interpreted on the basis of the reflection configuration and the surface geological relationships to have formed initially during jurassic to eocene compression and then to have been modified and exposed during early and middle eocene extension an example of a compressional structure observed on the profiles is the monashee decollement which can be traced from the surface westward into the lower crust extension is manifested along a variety of normal faults including the regionally extensive low angle okanagan valley eagle river fault system moderately dipping faults such as the columbia river and slocan lake faults and high angle faults such as the quilchena creek and coldwater faults both jurassic to eocene compressional shear zones and early to middle eocene extensional shear zones are listric into the lower crust or moho under the intermontane belt

colluvium definition differentiation and possible suitability for reconstructing holocene climate data abstract this study examines whether colluvial soils store climatic data and if these data can be used as proxies colluvial soils as the correlated sediments of soil erosion represent a widespread geoarchive these soils store the morphology data of the eroded soils and contain clues as to the processes of the eroded soils formation as well as indications of the pedogenesis which took place after the deposition all of these processes are closely related to climatic factors especially rainfall this study discusses the genesis of young soils in colluvial sediments and shows that typical soil features may be related to climatic factors furthermore the study investigates the genesis of anthropogenic colluvial sediments which must be seen as a syngenetical product of relief field size time of usage pressure of population farming technique sediment erodibility deposition area and climatic factors to this end pedogenic features are separated from the sedimentological features the results show that the reconstruction of all factors which control the genesis of the formation of a colluvium is still not yet possible this is the necessary precondition for colluvial soils to yield proxy climate data or for the data to be correlated with already existing holocene climate archives as the results of our discussion are ambiguous in their interpretation we conclude that colluvial soils which clearly include climatic information cannot be used for the reconstruction of proxy climate data at present

increasing maturity of kerogen type ii reflected by alkylbenzene distribution from pyrolysis gas chromatography mass spectrometry abstract a series of late devonian to early mississippian type ii kerogens with vitrinite reflectance values ro 0 29 2 41 were analyzed using py gc ms in addition a low maturity kerogen with ro 0 44 was separated into fractions via density gradient centrifugation followed by py gc ms of the alginite and amorphinite maceral concentrates alkylbenzenes and n alk 1 ene n alkane doublets represented the main compound classes identified in all pyrolysates the pyrolysate from alginite featured 1 2 4 trimethylbenzene and toluene as the two most prominent alkylbenzenes in contrast alkylbenzenes in pyrolysates from amorphinite and low maturity bulk kerogens with ro 0 29 0 63 were dominated by 1 2 3 4 tetramethylbenzene with increasing thermal maturity pyrolysates were increasingly dominated by i alkylbenzenes with fewer methyl groups namely by tri and dimethylbenzenes at medium maturity ro 0 69 1 19 and ii by toluene at higher maturity ro 1 30 2 41 with increasing maturity of kerogen type ii the decreasing abundance of highly methyl substituted alkylbenzenes and the parallel increase in less methyl substituted alkylbenzenes in flash pyrolysates suggest that demethylation is an important chemical process in the thermal maturation of kerogen type ii

large landslides and deep seated gravitational slope deformations in the czech flysch carpathians new lidar based inventory abstract moderate relief landscapes such as the czech flysch outer western carpathians cowc in comparison with alpine regions are rarely subject to extensive landslide inventory mapping an understanding of landslides in such a landscape is needed because densely populated hilly landscapes in temperate zones are usually of major socio economic importance in this study we performed the first lidar based landslide mapping for the entire cowc area 7539 km2 one of the most landslide prone regions in europe by calculating various landscape and landslide metrics we infer the distribution frequency area relationships kinematics and controls of mass movements with special attention on large landslides 0 1 km2 and deep seated gravitational slope deformations dsgsds we mapped a total of 13 611 landslides of which 1357 failures are large landslides and dsgsds whereas the lower and more subdued areas in the southern part of cowc are hotspots in terms of the total number of landslides the higher and more topographically pronounced areas in the northeast are affected predominantly by large landslides and dsgsds however landslides with 0 1 km2 are widespread throughout the whole territory of cowc a discrepancy also exists in the spatial distribution of different types of landslides rock slides and dsgsds are dominant in the north east while flow type landslides are dominant in the southern lower topographic relief with claystone dominated flysch we conclude that 1 distinct geological units nappes produce landslide populations with different frequency area distributions 2 stratigraphic composition alongside the tectonic style of flysch formations control the type of landslides 3 dsgsds affect mainly slopes formed by rigid rocks sitting atop soft formations and 4 geological conditions rather than topography control distribution of large landslides and dsgsds in cowc

evolution of hawaiian basalts a hotspot melting model melt generation and extraction along the hawaiian volcanic chain should be largely controlled by the thermal structure of the hawaiian swell and the heat source underneath it we simulate numerically the time and space dependent evolution of hawaiian volcanism in the framework of thermal evolution of the hawaiian swell constrained by residual topography geoid anomalies and anomalous heat flow along the hawaiian volcanic chain the transient heat transfer problem with melting relationships and variable boundary conditions is solved in cylindrical coordinates using a finite difference method the model requires the lithosphere to be thinned mechanically by mantle plume flow melting starts quickly near the base of the plate when the hotspot is encountered thermal perturbation and partial melting are largely concentrated in the region where the original lithosphere is thinned and replaced by the mantle flow the pre shield loihi alkalic and tholeiitic basalts are from similar sources which are a mixture of at least three mantle components the mantle plume asthenosphere and the lower lithosphere the degree of partial melting averages 10 20 with a peak value of 30 near the plume center as a result of continuous compaction melts are extracted from an active partial melting zone of about 10 20 km thickness which moves upwards and laterally as the heating and compaction proceed the rate of melt extraction from the swell increases rapidly to a maximum value of 1 105 km3 m y over the center of the heat source corresponding to eruption of large amounts of tholeiitic lavas during the shield building stage this volume rate is adequate to account for the observed thickness of the hawaiian volcanic ridge melts from direct partial melting of the mantle plume at depth may be important or even dominant at this stage although the amount is uncertain at the waning stage mixing of melts from the mantle flow pattern with those from low degree partial melting of the lithosphere may produce postshield alkalic basalts after the plate moves off the heat source continuous conductive heating can cause very low degree partial melting less than 1 of the lithosphere at shallow depths for about one million years this process may be responsible for producing post erosional alkalic basalts the extraction time for removing such small amount of melts is about 0 4 2 m y similar to the time gap between the eruption of post erosional alkalic lavas and the shield building stage our results show that multi stage hawaiian volcanism and the general geochemical characteristics of hawaiian basalts can be explained by a model of plume plate interaction

impact of microtopography on the geochemistry of soils within archaeological sites in se poland the geochemical record of human impact within three archaeological sites in se poland was analysed the total levels of cd cu pb zn and p were defined the content of the studied elements was found to be higher than the determined geochemical background in all cases significantly higher concentrations 2 3 times of trace metals were found in sediments filling small depressions and foot slope locations these concentrations were often higher than in the profiles within the archaeological objects the vertical distributions of elements were also different from soil profiles located on flat surfaces the study thus confirms that microtopography and soil erosion may impact diversify the initial horizontal and vertical variation of geochemistry of soils within archaeological sites caused by human activity this should be taken into account when using geochemical prospecting in archaeological studies in areas with varied topography

age and source of colluvial sediments at vaihingen enz germany abstract colluvial sediments accumulated on the lower slopes of a ridge as a result of past and present soil erosion were dated by optical 14 c and archaeological methods this allowed us to reconstruct the depositional history of the colluvium and also to identify temporary sedimentary sinks in its transportational pathway a cascade model of colluvium formation is developed colluvial sediments resulting from early soil erosion in the neolithic to iron age periods were mainly deposited on the upper slopes significant deposition on the lower slope occurred for the first time during the iron age and roman period since then deposition rates have increased because of more intensive land use

a geodynamic model for extension in the shuswap core complex southeastern canadian cordillera the shuswap core complex records mesozoic and paleocene crustal shortening with superimposed eocene extension during the shortening phase the crust was thickened and slowly uplifted within at most 20 ma of the climax of compression the crustal welt was rapidly uplifted and tectonically denuded shortening of the continental crust may be balanced in the underlying lithosphere by thickening or underplating forming in either case a lithospheric root beneath the crustal welt we consider a model whereby tertiary crustal extension in the shuswap core complex and possibly also in other segments of the north american cordillera is accounted for by the detachment of this root both the time frame and the stress field resulting from the detachment are compatible with geological and geophysical observations far field stresses played an accommodating role but the potential energy required for extension of the shuswap complex was induced by lithospheric thickening

some aspects of age assessment of holocene loess colluvium osl and 137cs dating of sediment from biala agricultural area south poland abstract at the end of the pleistocene in central eastern europe the accumulation of periglacial loess had already finished from the end of loess accumulation to the establishment of grass cover and forest succession in this area a phase of active modeling of the land surface by slope processes occurred before the beginning of the holocene this activity stopped and mollisol and alfisol formation started these soils are preserved beneath holocene colluvia until the neolithic age the area of loess formations in poland was uninhabited the extensive neolithic agriculture locally induced soil erosion causing slopewash on farmedslopes the scale of this process and establishing the age of the successive stages of the prehistoric soil erosion in loess deposits in poland is a key problem in the investigations of the human environment relationship in prehistory chronostratigraphy of the preserved holocene colluvia is very helpful in the solution of these problems optical osl dating was applied in chronostratigraphical analyses due to expected partial bleaching during sediment transport a single aliquot regenerative dose protocol sar was applied insufficient bleaching during transport on the slope is expected to be a serious problem for luminescence dating of loess colluvia and causes overestimation of the osl age quartz from the study site was suitable for age determination by sar the youngest 50 year old colluvia were also studied using the 137cs method the reliability of the obtained results is discussed in this paper as well as the influence of environmental processes and type of the applied methods on chronological assignments the precise age determination of loess colluvia is important for study of the human impact on the environment the results of osl dating show that soil erosion started in the neolithic with three phases of soil erosion neolithic middle ages and modern

present and past soil erosion rates in catchments of the kraichgau area sw germany abstract in four catchments of the kraichgau area sw germany all covered with loess and distinguished by different combinations of natural and manmade erosion risks total and recent soil losses from the hills were examined the total loss was calculated as difference of quantities of soil material of the mapped soil units compared with a profile under erosion protection the recent loss on the basis of young sediments in the depression using contents of cadmium and lead to distinguish between old and young soil deposits in the depressions in two of the catchments total soil loss from the hills came up to about 90 of the formerly existing luvisol material total soil loss did not correlate with the natural erosion risks inclination slope length but recent soil loss correlated with the manmade erosion risks land utilisation type this recent soil loss ranged from less than 14 t ha 1 yr 1 in the catchment with terraced slopes to 84 t ha 1 yr 1 in a catchment with a high percentage of corn and sugar beet on the cultivated area and with large fields cultivated downslope in a similarly endowed catchment but with transversally cultivated fields a recent soil erosion of 39 t ha 1 yr 1 was calculated methodical problems are discussed

tectonomagmatic evolution of cenozoic extension in the north american cordillera the spatial and temporal distributions of cenozoic extension and magmatism in the cordillera suggest that the onset of major crustal extension at a particular latitude was confined to a relatively narrow belt 100 km pre extension and followed the onset of intermediate and silicic magmatism by no more than a few million years extension began in early eocene time in southern british columbia northern washington idaho and montana farther s extension began at about the eocene oligocene boundary in the great basin and slightly later in the mojave sonora desert region the intervening area at the latitude of las vegas remained quiescent until mid miocene time compositional and isotopic characteristics of most pre miocene magmas are consistent with their containing major components of melted continental crust in mid miocene time two major changes occurred widening of the area of extension and the widespread appearance of basaltic magmas the area affected by extension from southwestern montana to the lake mead region widened to several hundred kilometres by this time extension in southern british columbia northern washington and northern montana had ceased probably before the end of the eocene and extension s of lake mead except in the gulf of california had waned regions affected by the broader belt of extension during late miocene pliocene and quaternary time experienced basaltic magmatism which began along a central rift zone in the northern part of the region and which had within a few million years spread to include most of the region later basaltic activity has tended to concentrate in restricted zones especially near the margins of the extended area we recognize a correlation between the amount of earlier crustal thickening and cenozoic extension and between the length of time after shortening but before extension and the degree to which a given region was intruded by late cretaceous plutons the localization of extension in areas of previous crustal thickening and the dependence of the timing of extension on the thermal state of the overthickened crust is consistent with a simple thermal mechanical model developed in a companion paper sonder et al this raises the possibility that stresses inherent in the north american plate dominated over plate interaction forces as controls of the cenozoic tectonomagmatic evolution of the north american cordillera especially in its earlier stages

stratigraphy and age of colluvial deposits indicating late holocene soil erosion in northeastern germany abstract in the focus of this study are the sedimentary characteristics chronology magnitude and causes of past soil erosion dynamics of an agriculturally intensively used glacial lowland landscape from the mesoscale quillow river catchment sedimentary sections bearing colluvial sediments from different landforms were analysed to explore their geoarchive potential and to establish a local chronology of late holocene soil erosion sections from footslopes contain a rather simple stratigraphy with one topping colluvial horizon of up to 1 m thickness burying a palaeosol in contrast glacial kettle holes preserve more complex sequences partly having several colluvial layers with intercalating palaeosols the most complex stratigraphy is associated with a kettle hole being the ultimate sediment trap for a dendritic gully system forming a 4 m thick sequence of alternating peat and colluvial layers thirty osl ages and 13 radiocarbon ages are used to reconstruct phases of soil erosion potentially human induced soil erosion which is corroborated by local archaeological and palynological data can be traced back to the last c 4000 years the oldest colluvial deposits date back to the late bronze age most datings however cluster within the last 600 years with a peak in the last 200 years ascribing the main phase of local soil erosion to the recent past thus although numerous archaeological finds are detected in the catchment since the neolithic considerable agricultural soil erosion does not occur before the last millennium a compilation of osl chronologies based on colluvial sediments from other regions in central europe shows a more complex erosion history there with a pronounced two or three phased distribution of ages primarily dating into the last c 4000 5000 years this study underlines that in northeastern central europe human impact on landscapes was effective apparently at a later stage as compared to some adjacent regions

spatial delineation of organic carbon rich colluvial soils in chernozem regions by terrain analysis and fuzzy classification abstract colluvial soils are considered to be the direct result of accelerated soil erosion resulting in accumulation of humus rich soil material in terrain depressions and base parts of slopes the organic carbon concentration in these soils and their depth make them an important organic carbon storage mapping the colluvial soils therefore represents an important contribution in total carbon stock estimation a method of delineating colluvial soils is proposed by applying a combination of high resolution digital elevation model analysis and detailed field survey two models based on fuzzy classification of soil units were created using different topographic derivatives as the only input parameters to predict the colluvial soil area on a morphologically diverse study site in the southern moravia czech republic the model that considers only the derivatives with a strong relationship to colluvial soil occurrence reached 71 accuracy in colluvial area delineation while the model combining six commonly used derivatives showed less favorable results the main advantage of the method lies in a low demand of input soil data and its relatively high accuracy

landform transformation and long term sediment budget for a chernozem dominated lowland agricultural catchment abstract the loess hilly lands of the south west foreland of the west carpathians are characterized by favorable climatic conditions smooth topography fertile soils and a long settlement history for the first time we document changes to human induced landforms in a small zero order dry valley 0 28 km2 with calcic chernozem soils and develop a long term sediment budget the original surface was reconstructed based on interpreting records of erosion and deposition from 185 soil cores and six valley cross sections the topography inherited from the pleistocene was transformed through lowering of hillslope ridges and convexities along with infilling of shallow depressions within the original valley bottom on convex convex landforms had an average net erosion of 0 32 0 01 m while average net accumulation in the valley bottom was estimated at 0 20 0 01 m the correlation between change in soil profile depth with profile curvature 0 51 p

landscape related transformation and differentiation of chernozems catenary approach in the silesian lowland sw poland abstract the unfavourable environmental conditions to chernozem development in central europe has led to questions regarding their origin and age and conditions necessary for chernozem persistence in central europe under a humid climate this paper deals with chernozem transformation during the holocene period in sw poland in relation to land morphology the study was based on a catenary approach with additional remarks on parent material homogeneity and soil classification based on textural and geochemical indices the homogeneity of aeolian material loess was proven in the main part of the catena which confirmed that the differentiation of dry and wet chernozemic soil across the catena did not result from the variability of parent material no differences in morphological or physicochemical characteristics of mollic horizons were identified between the well drained and wet sections of the catena the strong redoximorphic features manifested as stagnic or gleyic properties in the lowermost part of catena are therefore secondary features i e developed after the mollic horizon development presumably in late holocene period chernozems with chernic horizon weakly developed subsurface argic horizon and free of redoximorphic features prevail in the central well drained and not eroded section of the catena it has been hypothesized that the loess soils in the uppermost more inclined part of the catena have been truncated by erosion during the first agricultural period then afforested and transformed into luvisols probably due to temporary abandonment of those sites less favourable for farming the soils in the transitional zone received the colluvial addition of humus material from the eroded hill summit however the colour of the humus layer has a chroma too high for a chernic horizon that surprisingly shifted these soils to the kastanozems group this study showed that the direction of transformation of native chernozems in the holocene period was strongly related to their position in the landscape which affected the erosion accumulation intensity and water drainage conditions soil moisture regime as a final result of these transformations a relief related zonality of soils has developed with stagnic gleyic chernozems luvic chernozems colluvial kastanozems haplic luvisols in the lower moist middle well drained and upper colluvial eroded sections of the undulating loess plain respectively

cenozoic volcanism in the california coast ranges numerical solutions we present the results of numerical simulations of cenozoic volcanism in the coast ranges of california associated with the northward migration of the mendocino triple junction mtj three aspects of the thermal evolution and magmatism in the wake of the mtj are investigated 1 mantle flow and thermal perturbation in the slabless window 2 pressure release partial melting in the upwelling asthenosphere and 3 thermally induced crustal anatexis numerical results show that upwelling of asthenosphere in the slabless window causes a drastic change in the thermal structure of the lithosphere and results in significant pressure release partial melting in the upwelling asthenosphere up to 4 5 km of basaltic magma may be produced most of this mafic magma is likely stored near the base of the crust thermally induced crustal anatexis mainly occurs in the deep crust below 20 km where a high degree 50 of partial melting may be predicted most of the crustal melt is probably generated within 1 m y after the passage of the mtj this work also suggests that the spatial and temporal distribution of cenozoic volcanism in the california coastal ranges is directly related to the variation of the relative velocity between the north america and pacific plates in the last 30 m y the voluminous volcanic rocks in the northern california coast ranges correlate to the relatively high velocity between these two plates in the last 10 m y the reduced volcanism in the central coast ranges may be related to the slow migration of the mtj between 10 and 20 ma

heavy metals in the slope deposits of loess areas of the lublin upland e poland abstract the concentration of heavy metals cd cu pb zn has been analyzed in holocene slope deposits of the loess agricultural area in the eastern poland five profiles were examined in general low concentrations of the examined metals were determined on average 50 of the samples exceeded the designated regional geochemical background the average concentrations were cadmium

origin age and transformation of chernozems in northern central europe new data from neolithic earthen barrows in sw poland abstract among the clay illuviated soils dominant in the loess belt in southern poland islands of chernozemic soils are distinguished by their spectacular agricultural productivity however those soils are not marked as chernozems phaeozems in european and world soil maps due to their common excessive wetness and doubts regarding their origin well preserved earthen barrows of the funnel beaker culture discovered recently in muszkowice sw poland offer a unique possibility of pedo archaeological reconstruction the first of such in poland of the pre and post neolithic development of soil cover in loess dominated areas and explanation of the existing differentiation of soil cover into neighbouring chernozems and retisols the buried chernozemic soil phaeozem in muszkowice started to develop in the late pleistocene period mean residence time of humus 12 670 13 000 cal bp until the burial ca 5480 5310 cal bp an at least 22 cm thick mollic horizon has developed with secondary carbonates accumulation at ca 80 cm the barrow mound soil constructed entirely of initially humus rich topsoil material has transformed into retisol with fully developed thick eluvial and illuvial argic horizons and still preserved a high content of humus in the barrow mound soil profile further the surrounding soils are entirely altered into retisols with secondary carbonates starting at 135 160 cm taking into account the palynological reconstruction from the nearest pollen profile in the loess covered area a crucial importance of the open canopy mainly oak forests is concluded for the persistence of chernozems under a temperate increasingly moist climate from the early holocene to the neolithic period in turn the close canopy broadleaf forests mainly beech are considered to be responsible for the rapid transformation of chernozems phaeozems into retisols luvisols in the late holocene chernozems have persisted and probably even rejuvenated only in the areas of permanent settlement since the neolithic until the present time where human activity farming pasturing has eliminated a continuous broadleaf beech close canopy forest cover

temperatures heat flux and frictional stress near major thrust faults we examine the two dimensional advective and conductive transport of heat in a region of thrust faulting both simple theoretical considerations and numerical experiments show that the steady state temperatures near the fault are reduced by a divisor s 1 b z vsin below what they would be with the same heat sources but in the absence of advection in this expression z is the depth to the fault v is the slip rate is the component of the dip of the fault in the direction of underthrusting is thermal diffusivity and b is a dimensionless factor that is essentially equal to one for most forms of heating initial changes in temperatures near the fault are given by t z t t z 0 12vsin t z 0 z these simple formulae are successful because of the neglible influence of lateral conduction of heat at least for slip rates of a few mm yr or more two time constants govern the transition from the initial change in temperature to steady state t1 u v where u is the distance along the fault in the direction of underthrusting from the surface to the depth in question and t2 z 2 2 where z is the depth to the fault when elapsed times exceed the sum of these two time constants temperatures differ from their steady state values by only about 10 percent the numerical experiments indicate that the simple formulae are sufficiently accurate that sophisticiated numerical modeling of temperatures in specific regions is unwarranted putain an application of these simple formulae to measurements of conductive heat flow at island arcs implies that shear stresses at island arcs approach 100 mpa and are greater than 30 mpa calculations of temperatures appropriate for the himalaya suggest that shear stresses of 100 mpa on the main central thrust probably are required to account for the tertiary granites of the region if melting took place after slip began on the thrust similarly the cut off in seismicity at a depth of about 15 km in the himalaya if due to temperatures exceeding 350 to 450 c implies a deviatoric stress close to 100 mpa

prehistoric alteration of soil in the lower rhine basin northwest germany archaeological 14c and geochemical evidence in early holocene chernozems were assumed to have covered the entire loess landscape of the lower rhine basin today mirrored by the distribution of luvic phaeozems these luvic phaeozems have characteristic dark brown bht horizons accumulating clay and humus inherited and translocated from their precursors chernozem black humic a horizons we examined luvic phaeozems along a 33 km long and 2 0 2 5 m deep gas pipeline trench in the lower rhine basin west of cologne along this transect we discovered clusters of hundreds of regularly shaped pits these pits were always connected to the bht horizons of adjacent luvic phaeozems the luvic phaeozem horizons and the pits were investigated by combining methods from geo archaeology geographical distribution within the landscape shape of the pits soil texture geochemistry content of carbon nitrogen and black carbon palaeobotany species determination of charcoals and ams 14 c measurements we found that the luvic phaeozems occurred not only in the loess covered landscape but also in the sandy holocene floodplain and their distribution could not be limited to certain slope positions or parent material carbon and nitrogen concentrations in the luvic phaeozem horizons and pits were larger than in the surrounding luvisols whereas the c n ratios were small 10 material found in the luvic phaeozem pits was clearly different from material found in prehistoric settlements the pits investigated here never contained artifacts and carbon and nitrogen concentrations and c n ratios were smaller we found charcoal particles and black carbon contributed up to 46 of the total organic carbon the ams 14 c ages of charcoals and black carbon indicated that fire occurred from mesolithic 9500 5500 bc to the medieval ages 500 1500 ad and mainly in the late end neolithic period 4400 2200 bc we conclude that i the luvic phaeozem pits and horizons are man made formed during several archaeological epochs between mesolithic and middle ages ii these pits must have been formed outside the actual prehistoric settlements offsite and may serve as a novel archaeological feature iii the purpose of these pits at present is not clear and iv human activity has altered and ultimately formed the investigated soils of the lower rhine basin in prehistoric time

linking forest cover soil erosion and mire hydrology to late holocene human activity and climate in nw spain this article is distributed under the terms of the creative commons attribution noncommercial 3 0 license http www creativecommons org licenses by nc 3 0 which permits non commercial use reproduction and distribution of the work without further permission provided the original work is attributed as specified on the sage and open access page http www uk sagepub com aboutus openaccess htm

the history of soil erosion and fluvial deposits in small catchments of central europe deciphering the long term interaction between humans and the environment a review abstract during the last few decades many case studies focused on the dynamics of fluvial systems in response to hillslope erosion land use impact and climate changes this paper will review the current state of knowledge of the dynamics of past soil erosion and gullying in small catchments

holocene relief and soil changes in loess covered areas of south western germany the pedosedimentary archives of bretten bauerbach kraichgau based on infrared stimulated luminescence irsl dating of loess borne sediments a chronometry of holocene landscape evolution is established for a representative study site in the early settled kraichgau area in south western germany the results show that the gently rolling relief is due essentially to soil erosion and colluvial deposition triggered by humans cultivating the loess soils since the onset of agriculture in the neolithic period levelling of relief is accompanied by alterations in soil type patterns from haplic luvisols before the impact of humans over variably truncated luvisols with bt horizons prevailing at the slope surfaces in the middle ages to calcaric regosols characterizing both sites of erosion and accumulation since then the tremendous changes show that the effects of human activities have been recorded over thousands of years indicating an early anthropocene in a geomorphological and pedological sense most landscapes are probably more modified by humans than thought at first sight as the results show this recognition requires considering that current geomorphological and soil forming processes might work at different frequencies or magnitudes e g by changes of internal system thresholds such as increased erodibility following the complete erosion of a more resistant bt horizon and or in a different direction e g accumulation instead of erosion or sediment transport due to slope angles decreased by former deposition of colluvium than they would in the absence of a human controlled pre history

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

the role of tectonic grain size reduction in the rheological stratification of the lithosphere with the aid of published constitutive flow laws for common crustal and upper mantle rock types it is possible to construct curves showing variation of rock strength with depth in the continental lithosphere assuming a particular crustal stratification of rock types and a particular geothermal gradient such exercises lead to the conclusion that marked changes in strength can occur at major petrological interfaces such as the moho discontinuity which are therefore likely to be associated with a tendency for major sub horizontal detachments to form constitutive flow laws used for such purposes are usually assumed to represent steady state flow at constant rock microstructure

past and present interaction between the catchment and the valley floor upper osoblaha basin ne sudetes slope and foreland abstract the osoblaha basin includes the north eastern slope of the zlatohorska vrchovina ridge and the north eastern foreland area of the undulating glubczyce plateau rainfall ranges from 1000 mm year in the highlands to 650 700 mm year on the glubczyce plateau the mountain part of the osoblaha basin was already penetrated by humans in prehistoric times miners extracted gold from the alluvia and later from the slope covers their activities have left traces such as extant pits in sediments iron and other ores were mined and processed there from the early middle ages onwards in the 12th or 13th century at the latest settlements and towns were founded for mining e g janov zlate hory and by farmers who tilled the land at the foot of the valley slopes this exploitation of the mountainous part of the basin caused significant clearance of beech forests as the wood was used to manufacture charcoal the deforestation of the valley slopes or the introduction of spruce forests in lieu of the beech forests changed the circulation of rain and thaw water exposed slope covers were prone to erosion or liquefaction and transfer towards the mountain valleys flood episodes caused the sedimentation of clayey overbank deposits which cover the valley floor the considerable cohesion of these sediments was conducive to the formation of meandering or anastomosing channels which were a typical feature of the osoblaha valley floor in the area around the confluence of the zlaty potok prudnik in the second half of the 18th century and in the 19th century the glubczyce plateau is a 30 40 km wide area consisting of undulating plateaux ranging from 320 to 240 m a s l these are dissected by dry valleys and descend gently towards the north fertile soils the abundance of local streams and a climate conducive to farming led to this area being settled by farming and herding communities as early as the neolithic period around 7000 bp this initiated the deforestation process and increased soil erosion shown by the colluvia accumulated in the valley heads of dry valleys and by alluvial fan sediments close to their mouths where they entered the main valleys the last stage of farming colonisation of this part of the osoblaha basin initiated by slavs had already led to the development of a dense network of settlements and considerable deforestation in the mediaeval period

pressure temperature time paths of regional metamorphism i heat transfer during the evolution of regions of thickened continental crust the development of regional metamorphism in areas of thickened continental crust is investigated in terms of the major controls on regional scale thermal regimes these are the total radiogenic heat supply within the thickened crust the supply of heat from the mantle the thermal conductivity of the medium and the length and time scales of erosion of the continental crust the orogenic episode is regarded as consisting of a relatively rapid phase of crustal thickening during which little temperature change occurs in individual rocks followed by a lengthier phase of erosion at the end of which the crust is at its original thickness the principal features of pressure temperature time ptt paths followed by rocks in this environment are a period of thermal relaxation during which the temperature rises towards the higher geotherm that would be supported by the thickened crust followed by a period of cooling as the rock approaches the cold land surface the temperature increase that occurs is governed by the degree of thickening of the crust its conductivity and the time that elapses before the rock is exhumed sufficiently to be affected by the proximity of the cold upper boundary for much of the parameter range considered the heating phase encompasses a considerable portion of the exhumation decompression part of the ptt path in addition to the detailed calculation of ptt paths we present an idealized model of the thickening and exhumation process which may be used to make simple calculations of the amount of heating to be expected during a given thickening and exhumation episode and of the depth at which a rock will start to cool on its ascent path an important feature of these ptt paths is that most of them lie within 50 c of the maximum temperature attained for one third or more of the total duration of their burial and uplift and for a geologically plausible range of erosion rates the rocks do not begin to cool until they have completed 20 to 40 per cent of the total uplift they experience considerable melting of the continental crust is a likely consequence of thickening of crust with an average continental geotherm a companion paper discusses these results in the context of attempts to use metamorphic petrology data to give information on tectonic processes 1984 oxford university press

surprisingly small increase of the sedimentation rate in the floodplain of morava river in the stražnice area czech republic in the last 1300 years abstract sediment profiles from the floodplain of morava river in the czech republic have been collected from exposed river banks 4 6 m long sections and cores 2 4 m deep and investigated using a set of geochemical proxies validated by granulometry and conventional geochemical analysis outlined in our previous paper the work was conducted to evaluate the increase in sedimentation rate during medieval and modern time periods correlation of sediments along the current channel belt allows identification of two most important synchronous changes in the channel structure over the past 1300 years in the 13th century and at the end of the 16th century these changes could be related to central european climatic extremes rather than to land cover land use practises analysis of the pollen record in peaty deposits at the floodplain edge allows excluded dramatic deforestation in medieval times maps of the area from the last five centuries revealed direct and indirect signs of past avulsions and clearly show how the original multichannel system was transformed into a single meandering channel in the early 20th century the extrapolated aggradation rate net vertical accretion of floodplain fines except for levee sediments increased from 0 2 0 3 cm year in 700 ad to 0 3 0 4 cm year in 2000 ad depending on the grain size of the sediment this is the smallest yet reported enhancement of siliclastic deposition although morava river watershed has been intensively used for agriculture and its land cover has changed in a manner similar to west and central european rivers