seasonal changes in the hydrological and erosional response of a hillslope under dry mediterranean climatic conditions montes de malaga south of spain the mediterranean eco geomorphological system was analysed at one representative hillslope of the geological unit of montes de malaga province of malaga spain under dry mediterranean climatic conditions the research was divided into two stages first the eco geomorphological pattern of the slope and some physical properties of the soil were analysed second the hydrological and erosional response of the eco geomorphological system was analysed by applying simulated rainfall to the main elements of the system and using closed plots with different lengths this hydrodynamic analysis was carried out during two periods crucial for the mediterranean environment in hydrological terms the end of the dry season or the beginning of the active hydrodynamic season and the middle of the wet season the results show that i the hydrophobic behaviour of soil is the predominant runoff generation mechanism that accounts for sediment movement ii once soil was moistened in the wet season it lost its hydrophobicity and the saturation of soil became a predominant runoff generation mechanism and iii there was high variability in hillslope runoff with evident hydrological disconnections which made the hydrodynamic response of the eco geomorphological system complex due to the absence of a clear predominance of abiotic or biotic factors

the erosional response of calcareous soils along a climatological gradient in southeast spain abstract the erosional response of calcareous soils along a climatological gradient in alicante se spain was studied the erosional response was defined in terms of indicators obtained from field rainfall simulation experiments and laboratory studies of soil aggregation measurements were made at seven sites on limestones and marls between benidorm with an annual average rainfall of 400 mm yr 1 and coll de rates annual rainfall 900 mm yr 1 the sites were on matorral vegetation affected to varying intensities by grazing and fire at the seven locations soil aggregation was studied by sieving by the single water drop test and by a microscan particle sizer rainfall simulation experiments were made on circular 55 cm diameter target area plots using the calvo simulator at an intensities between 35 and 59 mm h 1 on limestone it was found that on bare surfaces the coarse soil aggregation increases with depth at the highest sites and decreases at the lower sites the benidorm surface soil has the highest erodibility the least stable soils are at the lower intermediate sites on marls the aggregate stability is generally high in contrast to those under cultivation simulated runoff from the wetter limestone sites is very low the driest areas have the highest runoff and sediment yields trends with climate suggest that the erosional responses of the soils indeed increase with aridity and temperature but local factors have a large effect particularly at intermediate altitudes a clear relationship like that found in israel by lavee on a similar lithology does not exist

paleomagnetism and magnetic fabric of the deformed redbeds of the cap de la chevre formation brittany france abstract we present the results of a palaeomagnetism and magnetic fabric study in six sampling sites of the lower ordovician redbeds of the cap de la chevre formation crozon peninsula france measurement of anisotropy of magnetic susceptibility ams shows that these beds are affected by a weak but significant tectonic strain during the hercynian folding of the armorican palaeozoic cover samples containing small elliptical reduction spots allowed us to check the control of strain on ams site mean ams data were then used to provide strain estimates at each site analysis of remanent magnetization through thermal and chemical stepwise demagnetization procedures allowed us to isolate three magnetic components component a defined in the lower unblocking temperature range is a recent overprinting which clusters around the present day dipole field direction components b and c defined respectively in the intermediate and higher unblocking temperature ranges appear to be pretectonic in age the fold test however is inconclusive for both because of the significant dispersion still remaining after the simple tilt correction assuming that at least a part of this dispersion is due to strain we have applied the strain removal technique using ams derived strains at each site this results in a clustering of component c from four sites allowing recovery of the primary ordovician paleomagnetic direction d 261 i 71 95 11 in contrast unstrained component b shows a small circle distribution containing the formation mean of unstrained component c the hypothesis that component b and c distributions arise from beds being tilted during a long term magnetization acquisition in the ordovician field is discussed taking into account the extensional geodynamic context during deposition of lower palaeozoic redbeds in brittany

analysis of soil surface component patterns affecting runoff generation an example of methods applied to mediterranean hillslopes in alicante spain abstract spatial patterns of soil surface components vegetation rock fragments crusts bedrock outcrops etc are a key factor determining hydrological functioning of hillslopes a methodological approach to analyse the patterns of soil surface components at a detailed scale is proposed in this paper the methods proposed are applied to two contrasting semi arid mediterranean hillslopes and the influence of soil surface component patterns on the runoff response of the slopes was analysed a soil surface components map was derived from a high resolution photo mosaic obtained in the field by means of a digital camera rainfall simulation experimental data were used to characterise the hydrological behaviour of areas with a specific pattern of soil surface components by means of the parameters of the horton equation plot runoff data were extrapolated at the hillslope scale based on the soil surface component maps and their hydrological characterisation the results show that in both slopes runoff generation is concentrated up and downslope with a water accepting area in the centre of both slopes disrupting the hydrological connectivity at the slope scale this reinfiltration patch at the centre of the slope is related to the type of soil surface component and its spatial pattern herbaceous vegetation and on top rock fragments increase the infiltration capacity of soils at the centre of the slope in contrast embedded rock fragments rock outcrops as well as crusted surfaces located in the upper and lower slopes favour runoff generation in these areas in addition a general pattern of water contribution areas downslope is apparent on both slopes the south facing slope shows a higher hydrological connectivity and more runoff 55 of the surface of the south facing slope produces runoff at the end of a 1 hour rainfall event and 17 3 of the surface is covered by a runoff depth between 0 5 and 1 mm while on the north facing slope only 38 of the surface produces runoff under the same conditions longitudinal connectivity of runoff is higher at the south facing slope where more runoff generating surfaces appear and where the vegetation pattern favours the connectivity of bare areas

characterization of the magnetic fabric of rocks abstract an inextensive system of magnetic susceptibility anisotropy factors is suggested which is sufficient in the majority of practical applications for characterizing the magnetic fabric of rocks the system involves three newly devised factors the corrected anisotropy degree the shape factor and the difference shape factor the first of these characterizes the quantity of anisotropy somewhat better than the commonly used anisotropy degree the shape factor characterizes the quality of anisotropy i e the shape of the susceptibility ellipsoid in a convenient way its definition is based on a certain analogy between the anisotropy ellipsoid and the strain ellipsoid the difference shape factor can replace the shape factor when only the differences between the principal susceptibilities are given while the mean susceptibility is unknown

archean regional transpression and paleomagnetism in northwestern ontario canada abstract the archean metamorphic rocks of the superior province of the canadian shield occur in lithologically defined belts or subprovinces the tectonically more stable interiors of belts possess consistent primary components of magnetic remanence in the case of the quetico belt these stable directions are tightly grouped about 005 55 with some minor dispersion and most were acquired during the cooling that followed syntectonic recrystallisation this study examines the directions of primary remanence components for rocks along the margins of the quetico belt within 4 km of the strongly deformed vertical ene trending boundaries the boundaries are known to have experienced dextral transpression involving penetrative single phase deformation which out lasted metamorphism within a few kilometres of the belt boundaries the primary remanence components are re distributed along a vertical ene trending great circle girdle which is nearly parallel to the plane of transpressive shear and regional schistosity it is suggested that the effects of transpression have mechanically deflected the components of primary remanence toward this plane

nonlinearity of ecogeomorphic processes along mediterranean arid transect the study was conducted along a climatic transect extending from the judaean mountains mean annual rainfall 700 mm annual mean temperature 17 c to the dead sea mean annual rainfall 100 mm annual mean temperature 23 c a high correlation was found between climatic conditions and factors and processes of the ecogeomorphological system the values of certain factors and processes such as soluble salt content and overland flow increase with increasing aridity whereas those of others such as soil organic matter content clay content aggregate size and stability and infiltration rate diminish with increasing aridity these trends express the long term effect of the prevailing mean climatic conditions in the research stations conditions that led to the development of various types of soil and of plant communities it was also found that for many of the factors and processes examined such as organic matter content salt concentration aggregate stability infiltration rate and overland flow yield the rates of change with respect to position along the transect are not linear and that a climatic threshold value exists in the zone with a mean annual rainfall of about 300 mm and in which the p t ratio is about 17 which creates a sharp boundary between arid and mediterranean ecogeomorphological systems while in arid systems erosion occurs mainly through physical mechanical processes under mediterranean systems it is governed mainly by chemical and biological processes the significance of the existence of a sharp boundary between the arid and the mediterranean zones is that even a relatively slight increase in the annual mean temperature and or a slight decrease in the mean annual rainfall is liable to shift the boundary towards the mediterranean zone and accelerate desertification processes

deriving indicators of soil degradation from soil aggregation studies in southeastern spain and southern france soil degradation is perceived as a major threat in the mediterranean region due to changes in land use and possible future climate change soil aggregation parameters are used here to demonstrate their potential as a key indicator for land degradation studies the monitoring of these indicators offers a means of establishing the vulnerability and resilience of geo ecosystems soil aggregation stability and distribution were studied on soils with an open shrubby vegetation cover from several places in southeastern spain and southern france by applying drop tests and determining aggregate size distributions aspect and vegetation cover were incorporated in the soil sampling several indices were derived from these analyses to indicate the degree of soil aggregation this was done by referencing to a base level of aggregation bare soil aggregation it was found that soil aggregates were more stable and were often coarser under vegetation when compared to their immediate surrounding bare areas a similar slightly less clear effect was noted on n facing exposed slopes when compared to s facing exposed slopes long term changes were found by studying cultivated land abandoned fields and land covered by semi natural vegetation on comparable substrate and comparable land units it is clear that soil aggregation and aggregate stability increases with time years it is argued that soil aggregation indices can be used as a key indicator for degradation processes at a fine scale with implications for runoff and sediment generating processes at the hillslope scale

remagnetisation of a rock analogue during experimental triaxial deformation abstract synthetic specimens containing pseudo single domain magnetite were given a univectorial anhysteretic remanent magnetisation they were deformed in a ductile manner at room temperature under a confining pressure of 150 mpa 1 5 kbar the strain rate was 10 5 s 1 and the maximum strain achieved was 23 shortening a weak 0 035 mt magnetic field was present in the pressure vessel during deformation hydrostatic compaction alone produced pressure demagnetisation of low coercivity components of remanence but did not change remanence directions macroscopic differential stress was needed to deform the specimens and this also permitted syndeformational remagnetisation for values of more than 20 mpa 200 bars this added new components of piezo remanent magnetisation prm approximately parallel to the direction of the magnetic field in the pressure vessel they were acquired in all coercivity intervals but the largest components were added below 35 mt the final remanence orientation and its spatial distribution of vector components were dictated by the relative orientations of the remagnetising field and the initial remanence prm contributions almost completely masked the changes related to strain induced grain rotation at these low strains the directions of the externally imposed stress strain axes may not significantly influence the direction of new remanence components prm acquisition occurs when differential stress exceeds a threshold value that probably depends on the previous stress history of the magnetite grains in part this may explain the origin of syntectonic remagnetisation in some naturally deformed rocks where the remanence is not reset by recrystallisation or thermal or chemical processes

experimental deformation of two component irm in magnetite bearing limestone a model for the behaviour of nrm during natural deformation abstract experimental room temperature triaxial deformation at 200 mpa 2 kbar and at a controlled strain rate of 10 5 s 1 is performed on three limestones with magnetic behaviour dominated by single domain magnetite permanent deformation is achieved mainly by twinning of calcite isothermal remanent magnetisation irm in the samples is reduced in magnitude especially when parallel to compressive stress the decrease in magnitude correlates slightly better with peak stress than with strain in accord with previous work in uniaxial tests indicating the role of stress in deformational demagnetisation remanences have their vector plots condensed after deformation particularly in the range 0 30 mt a two component irm is used as a simple model of a multi component natural remanent magnetisation nrm the resultant vector is deflected by the action of stress towards whichever components are least reduced by deformation in the case of magnetite bearing rocks this appears to be the most coercive components in the case of a natural deformation it is predicted that the effects of stress at any stage should be to remove progressively any low coercivity components added to an nrm by remagnetisation during tectonism especially those parallel to compressive stress

overland flow generation mechanisms affected by topsoil treatment application to soil conservation abstract hortonian overland flow is responsible for significant amounts of soil loss in mediterranean geomorphological systems restoring the native vegetation is the most effective way to control runoff and sediment yield during the seeding and plant establishment vegetation cover may be better sustained if soil is amended with an external source four amendments were applied in an experimental set of plots straw mulching sm mulch with chipped branches of aleppo pine pinus halepensis l pm terracottem hydroabsorbent polymer hp and sewage sludge ru plots were afforested following the same spatial pattern and amendments were mixed with the soil at the rate 10 mg ha 1 this research demonstrates the role played by the treatments in overland flow generation mechanism on one hand the high macroporosity of sm and pm together with the fact that soil moisture increased with depth explains weak overland flow and thus low sediment yield due to saturation conditions therefore regarding overland flow and sediment yield ru behaves similarly to sm and pm on the other hand when hp was applied overland flow developed quickly with relatively high amounts this together with the decrease downward in soil moisture along the soil profile proved that mechanisms of overland flow are of the hortonian type

paleomagntism of archean rocks from northwestern ontario ii shelley lake granite quetico subprovince the 2580 20 ma shelley lake granite of the quetico gneiss belt in northwestern ontario preserves two distinct natural remanent magnetizations nrm s of different ages type 1 nrm of either normal 1n or reverse 1r polarity was isolated in 43 samples using three methods stable end point directions orthogonal vector plots and converging remagnetization circles the mean direction based on both 1n and 1r results is d 5 9 i 56 4 k 95 4 95 4 4 n 12 sites which is significantly different from both the present earth s field pef and axial dipole field directions at the site type 2 nrm either normal 2n or reverse 2r was successfully separated from 1n 1r in 13 samples its mean direction combining both polarities is d 70 3 i 27 8 k 20 1 95 9 4 n 13 samples the paleopole sl1 corresponding to 1n 1r falls at 65 8 e 77 6 n near track 6 of the laurentian apparent polar wander path apwp around 2600 ma this remanence is carried principally by primary multido

paleomagnetism of archean rocks from northwestern ontario iv burchell lake granite wawa shebandowan subprovince the late archean burchell lake granite of the shebandowan greenstone belt in northwestern ontario has a characteristic natural remanent magnetization nrm resembling the type 1 nrm of the nearby shelley lake granite of the quetico gneiss belt of 36 stably magnetized samples 21 had predominantly normal polarity 1n nrm and 15 had reverse polarity 1r the mean direction based on stable end point and vector subtracted directions is d 2 3 i 48 9 k 23 9 95 10 0 n 10 sites intersecting remagnetization circles gave a similar direction the corresponding paleopole bl1 lies at 83 2 e 71 1 n near track 6 of the laurentian apparent polar wander path around 2600 ma although the burchell lake pluton is not dated radiometrically neighbouring granites give k ar biotite ages of 2550 2600 ma and it is reasonable to suppose that the nrm dates from the time of intrusion or shortly thereafter a type 2 nrm like that of the shelley lake granite was isolated in 12 samples its mean direction is d

the influence of geomorphological position and vegetation cover on the erosional and hydrological processes on a mediterranean hillslope soil erosion and runoff rates are assumed to be highly dependent on slope position however little knowledge exists about the hydrogeomorphological processes at the pedon scale that support this idea in order to assess the hydrological and erosional behaviour of soils at different slope positions simulated rainfall experiments 55 mm was applied during one hour were carried out on a south facing slope with underlying limestone in south east spain in the mean terms the erosion rates 9 g m2 hr 1 and the runoff coefficients 12 were very low at the scale of measurement 0 25 m2 the slope position does not affect erosion rates when the measurements are carried out under extreme dry conditions during summer the low runoff rates found in summer under thunderstorms of high intensity 5 year return period and the runon into surfaces with higher infiltration rates resulted in no detectable direct surface runoff hortonian at the slope scale this implies that erosion as a consequence of surface overland flow will only take place during events of high magnitude 55 mm hr 1 and low frequency 5 years vegetation is the most important factor determining the soil erosion and runoff rates within the slope 1998 john wiley sons ltd

paleoremanence dispersal across a transpressed archean terrain deflection by anisotropy or by late compression the quetico belt is an archean metasedimentary terrain sandwiched between greenstone subprovinces a single regional schistosity is subparallel to magnetic foliation defined by anisotropy of low field magnetic susceptibility ams and anisotropy of anhysteretic remanence aarm aligned micas are the primary cause of ams aligned pyrrhotite is the sole cause of aarm each magnetic subfabric is due to minerals that grew in overlapping intervals in the strain history their slight obliquity may be due to crystallization during noncoaxial strain magnetic fabric ellipsoids suggest varying severity of flattening very strong flattening on the northern boundary less severe on the southern boundary and least severe in the interior the interior and the southern boundary of the belt stretched horizontally and the shortening direction varies gradually from ns in the north to nnw in the south the paleomagnetic record carried by pyrrhotite shows characteristic remanences dispersed around a great circle subparallel to the regional schistosity and magnetic foliations late stress effects rotated paleoremanences into this pattern we discount deflection of the paleofield by anisotropy the pattern of dispersal indicates uniaxial oblate flattening of the region with nnw sse shortening late in the metamorphic cooling history 300 c this postdates schistosity ams and aarm fabrics but it is controlled by the same kinematic pattern

eco geomorphological system response variability to the 2004 06 drought along a climatic gradient of the littoral betic range southern spain abstract one of the main characteristics of the mediterranean climate is the high frequency of droughts which last for a year or more and the appearance of dry spells within the wet season the littoral betic range in the south of the iberian peninsula shows a significant climatic gradient from the straits of gibraltar 1600 mm year 1 to the cabo de gata 150 mm year 1 these differences in climatic conditions result in variations in the elements of the eco geomorphological system at the hillslope scale this study aimed to analyse the immediate consequences of a two year drought period 2004 06 on several elements of the mediterranean eco geomorphological system on three hillslopes under different climatic conditions sub humid dry mediterranean and semi arid the soil water content the pattern of vegetation and some soil properties organic matter content aggregate stability and permeability were analysed before nov 2003 and during nov 2005 the drought period the most important findings were i a reduction in the soil water content which reached values below the wilting point in the wet seasons affecting negatively the water available for vegetation especially in the wettest sites ii a reduction in vegetation cover and the number of plants especially on semi arid field sites iii changes in the organic matter content which aggravate the loss of stability of soil aggregates a process seen more clearly under more arid conditions and iv a reduction of soil permeability in all situations in the climate gradient studied which supposes a priori an increase in erosive processes due to surface runoff these results indicate increased vulnerability of the eco geomorphological system because of the rainfall drought situation

soil erosion and hydrology of the western mediterranean badlands throughout rainfall simulation experiments a review abstract rainfall simulation experiments are widely used in geomorphological research in badland areas this technique contributed significantly to our understanding of badland geomorphology in the mediterranean belt due to the different types of simulated rainfall applied and the variable size of the plots a review of the state of the art is necessary this study confirmed that rainfall simulations are well suited to i analyse runoff infiltration processes and sediment detachment within badlands and ii to establish the factors determining the hydrological and erosion response at interrill scale in badland areas the hydrological response of badlands is characterized by rapid responses low to moderate infiltration rates ranging from close to 0 to 55 mm h 1 and high runoff coefficients i e 60 positive relationships are observed between antecedent soil moisture content and rainfall intensity on the one hand and runoff coefficients on the other sediment concentration and soil detachment rates are among the highest measured on the mediterranean region i e up to 84 8 g l 1 and 4722 4 g m 2 h 1 results show that rainfall intensity runoff coefficient and slope angle have a positive influence on sediment concentration and sediment detachment in the case of rock fragment cover its influence is variable according to the soil cover percentage rainfall simulations increase our understanding of the temporal and spatial variability of the soil erosion processes however rainfall simulation provides mostly qualitative rather than quantitative information because of the small plot size and the simulated rainfall characteristics due to facility for repeating experiments and recording a high quantity of data in short time however this method allows the comparison amongst different environments and soil conditions as the rainfall properties can be reproduced

deformation across the western quetico subprovince and adjacent boundarl regions in minnesota north to northwest directed crustal shortening across the western quetico subprovince and its boundary regions produced a complex deformation sequence within the quetico belt and resulted in concentrated zones of dextral ductile shear in the boundary regions within the adjacent greenstone granite terranes in this paper we review and introduce new data on the regional deformation features and their geometries and discuss the history of generation of these features we attribute the deformation sequence to differential partitioning of shortening and shear strains during dextral transpression associated with oblique convergence and accretion along the southern margin of the superior province the turbiditic wacke in the western quetico subprovince now typically amphibolite facies schist and migmatite underwent an early deformation stage that included recumbent folding f1 and the generation of an s1 bedding parallel foliation this event is most evident along the northern and southern boundaries of the

reorientation of remanent magnetism during tectonic fabric development an example from the waynesboro formation pennsylvania u s a abstract a paleomagnetic study of the late early early middle cambrian waynesboro formation in south central pennsylvania reveals a pre folding magnetization which is close to the expected cambrian field at three sites while other site mean directions are rotated by as much as 82 from the expected cambrian field these results are based on detailed thermal demagnetization analysis of 84 red siltstone and sandstone samples from nine sites collected over a 163 km 2 area local faulting fault block rotation and remanence acquisition during rapid apparent polar wander do not appear to be responsible for the observed remanence deviations total strain at the sites as indicated semiquantitatively by the anisotropy of magnetic susceptibility ams of 28 samples has been studied to test the hypothesis that deformation has rotated the remanence directions ams data vary considerably both between sites and within sites and show a path of progressive deformation on a flinn diagram there is a strong positive correlation between the deviation of a sample s remanence from the expected cambrian field and its position along the deformation path suggesting that finite strain fabric development has rotated the magnetizations the study area is structurally contained in the south mountain anticlinorium whose southern margin forms the displacement transfer zone to the southern appalachian alleghenian thrust sheets elliott 1976 if thrusting had continued and incorporated the waynesboro rocks into these thrust sheets the rotated magnetizations could have been incorrectly interpreted to result from rigid thrust sheet rotation

enigmatic origin of ferruginous coprolites evidence from the miocene wilkes formation southwestern washington excrement shaped masses of siderite and limonite have been reported from clay rich sedimentary rocks that range in age from late permian to holocene these objects have been widely accepted as being coprolites but the ferruginous composition absence of internal inclusions and scarcity of associated vertebrate remains suggest that they may instead be pseudofossils created by mechanical deformation of plastic sediment possible abiotic mechanisms include coseismic liquefaction intrusion of sediment into hollow logs or expulsion of sediment in response to gravity alternatively carbon stable isotope ratios indicate that sediment extrusion may have been related to emission of biogenic methane during early stages of diagenesis

runoff generation sediment movement and soil water behaviour on calcareous limestone slopes of some mediterranean environments in southeast spain abstract an interpretation of soil hydrology and erosion data obtained from limestone areas in southeast spain is presented in the framework of recent hypotheses on runoff generation mechanisms in mediterranean environments the main objective is to synthesise and harmonise the data in theoretical concepts or behavioural models of hydrological functioning of mediterranean limestone slopes for this purpose data were collected in a typical limestone area with climatic characteristics ranging from subhumid to semiarid several sites were chosen with comparable slopes vegetation and soils along a transect of 20 km to carry out several research projects the data discussed in this paper consist of information on water redistribution within the soil profiles obtained from long duration up to 5 h rainfall simulation experiments with continuous monitoring of soil moisture at different depths runoff and sediment concentration data were obtained i from rainfall simulation experiments with different antecedent soil moisture conditions and ii as natural results from open gerlach plots on runoff and sediment movement over 4 years three conceptual models of water redistribution during the infiltration process could be observed two of them imply nonuniform water redistribution within the soil profile due mainly to macropore flow caused by specific soil surface characteristics at the plot scale runoff generated in bare patches is mainly hortonian in plots with previously wetted soils or soils with high infiltration capacities the generated runoff implies the saturation of the upper soil both types of runoff are discontinuous through time and space the runoff generation mechanisms at the slope scale have been synthesised into two conceptual models a hortonian discontinuous runoff model that takes place in the most degraded slopes or during high intensity rain events and a mixed runoff generation model in less degraded slopes or in previously wet soils where infiltration excess runoff as well as saturation excess runoff can happen on the same slope in both cases slopes behave as a patchwork of runoff and runon areas the size of the runoff or runon patches is dependent on the climatological conditions these control the hydrological disconnection between different parts of the slopes hortonian and saturation runoff can both be generated and infiltrated downslope