thermomagnetic characteristics in late orogenic granites and gneisses of the southern appalachian piedmont abstract thermomagnetic curves have been obtained for samples from 25 granites and gneisses in georgia south carolina and north carolina this data set can be divided into two distinct curve types type i includes rocks which exhibit no distinct curie points and a linear decrease in magnetization with increasing temperature type ii curves exhibit a distinct curie point over a range of temperatures expected for magnetite 500 580 c synthetic samples constructed from magnetite and hematite powder exhibit type i behavior when the hematite to magnetite ratio is high e g 15 1 examination of polished sections shows relatively coarse grained magnetite only in type ii rocks we interpret our data to indicate that type i thermomagnetic curves are dominated by relatively large hematite magnetite ratios while type ii granites are characterized by relatively coarse grained magnetite type i granite samples have low magnetic susceptibility values less than 4 10 4 cgs while most type ii granite samples have higher values the type i granites are invariably18o enriched whereas type ii granites typically exhibit low18o 16o ratios these relationships are consistent with previously reported correlations of susceptibility generally indicative of magnetite content and oxygen isotopic trends in the southern appalachian piedmont

paleomagnetic study of cambrian potsdam group sandstones st lawrence lowlands quebec abstract we report paleomagnetic results from oriented drill core samples collected at 10 sites 80 samples from the covey hill and 19 sites 96 samples from the overlying fossiliferous cha teauguay formations of the gently dipping late cambrian potsdam group sandstones exposed in the st lawrence lowlands of quebec stepwise thermal demagnetization analyses ave revealed the presence of two predominant groups of coherent magnetizations c 1 and c 2 after simple correction for bedding tilt the c 1 group magnetization is a stable direction d 332 i 18 with unblocking temperatures t ub between 550 and 650 c present in the older covey hill formation this direction is probably a chemical remanence acquired during the covey hill diagenesis and carried predominantly by hematite the c 2 group magnetization d 322 i 9 is present at 13 sites of the younger cha teauguay formation this is probably carried by magnetite and represents a penecontemporaneous depositional drm characterized by t ub spectra 400 550 c we believe that c 2 is relatively younger than c 1 based on a combination of arguments such as the presence of opposite polarities internal consistency similarity and common occurrence of c 1 and c 2 respectively in the covey hill and cha teauguay members the corresponding paleomagnetic poles c 1 46 n 149 e dp dm 3 5 and c 2 37 n 156 e dp dm 2 5 are not significantly different from most of the other late cambrian dresbachian franconian poles derived from sediments exposed in the southern region texas of the north american craton which are also believed to have been deposited during croixian sauk sea transgression similar to the potsdam sandstones although adequate faunal control is lacking in particular for the covey hill formation this comparison with the cratonic poles suggests a late cambrian age to the potsdam poles the agreement between the results also gives the evidence for internal consistency of cratonic poles at least for late cambrian the incoherent c 3 group remanence d 250 i 15 is commonly present at 7 sites in both the formations this may not correspond to a reliable paleomagnetic signal the other remanence c 4 d 180 i 10 is found only at 3 sites located in the uppermost stratigraphic levels of the cha teauguay formation the corresponding paleomagnetic pole 40 n 107 e does not differ significantly from the ordovician and some late cambrian poles the present data are insufficient to resolve a problem in apparent polar wander for middle and late cambrian time posed by the existence of high latitude poles for some strata of middle cambrian age and low latitude poles for some strata of late cambrian age

human impact and slope dynamics evolutionary trends in the monoclinal relief of adriatic area of central italy abstract the present work deals with a large area of the marche abruzzi monoclinal relief which is made up of a clayey sediment succession with sandy conglomeratic levels alternating at varying stratigraphic heights the east verging monocline was generated by an intense quaternary tectonic uplifting it differs approximately in the west east and in the southern directions forming three wide morphostructures the deep fluvial down cutting disjointed the monoclinal relief into a succession of high hills which give the area a typical cuesta morphology with fronts facing the western quadrants the present study aims at contributing to the knowledge of recent slope morphodynamics by analyzing the spatial distribution and state of activity of fast hydro erosion processes and superficial mass movements correlations are made between these phenomena and the morphotectonic and lithological features of the various sectors in the area with particular reference to agricultural land use the present research underlines how the badlands represent the most spectacular form of fast erosion whereas the landslide phenomena which affect the prevalently loamy clayey eluvial colluvial covers are the most widespread processes despite the distribution density and recent or current evolutionary trends are generally associated with different morphostructural features of the various sectors of the area they prove to be strictly controlled by agricultural exploitation and by the connected techniques and types of cultivation

rainfall runoff and sediment transport relations in a mesoscale mountainous catchment the river isabena ebro basin this paper examines the relations between rainfall runoff and suspended sediment transport in the isabena basin during a quasi average hydrological year the isabena is a mesoscale river basin that drains a mountainous area comprising patches of highly erodible materials badlands the paper includes an analysis of the different hydrological and sedimentary responses of the catchment to a similar rainfall thirty four floods were studied with a very variable response observed runoff coefficients ranged from 0 32 to 33 the sedimentary response was also highly variable with maximum suspended sediment concentrations ssc oscillating between 0 1 and 90 g l 1 and flood sediment loads varying from 27 to 54 000 t per hydrological event most sediment load was concentrated in spring when competent floods occur frequently pearson correlation matrix and backward stepwise multiple regression indicate that the hydrological response of the catchment is strongly correlated with total precipitation event duration and rainfall of the previous days very low correlation was observed with rainfall intensity the relation between rainfall and sediment transport followed the same trend sediment variables e g total load and ssc were significantly correlated with variables such as total rainfall and rainfall over the previous days although the significance level was lower in comparison with the runoff related variables there was again no correlation between sediment variables and rainfall intensity on going research in the area suggests that apart from rainfall factors such as sediment availability in the badlands and accumulation of sediment in the channels influences the river s sedimentary response the non linear hydrosedimentary response is reflected in the wide range of runoff coefficients and sediment loads that have been observed in response to similar amounts of precipitation

paleomagnetism of the cambrian moore hollow group texas evidence for a primary magnetization carried by detrital magnetite petrographic and paleomagnetic studies of the cambrian moore hollow group texas establish the presence of three magnetic minerals and several components of magnetization hematite is the dominant carrier of the magnetic remanence in most samples and is primarily a diagenetic replacement of preexisting fe bearing phases hematite dominant samples have characteristic directions which range from shallow easterly to shallow southerly this distribution suggests multiple components of magnetization acquired at various times in the paleozoic the paleopole obtained for an unmineralized breccia 135 7 e 15 4 n represents either a chemical remanent magnetization of middle ordovician to early silurian age or a vector addition of two or more cambrian through silurian components mineralized breccias at the silver creek mississippi valley type deposit yield a permian direction 117 0 e 51 6 n because hematite in this deposit predates mineralization the permian age represents a maximum age for the mineralization at silver creek many samples contain goethite as a replacement of fe dolomite glauconite and pyrite the direction of magnetization carried by goethite is near the present geomagnetic field or in a minority of samples antipodal to it rounded ti magnetite was identified by sem in magnetic extracts from siliciclastic poor facies irm acquisition and thermal demagnetization confirms the presence of magnetite in these samples some samples contain an apparent modern viscous remanent magnetization the dominant component 72 samples 10 sites has a site mean declination of 93 8 and inclination of 14 5 with an 95 8 5 corresponding to a pole position at 163 0 e 0 6 s the presence of detrital magnetite polarity changes lack of evidence for prolonged burial and the proximity of this pole position to other late precambrian cambrian poles suggest that this component of magnetization indeed reflects the late cambrian paleopole for cratonic north america

dendrogeomorphology in badlands methods case studies and prospects soil and vegetation are interacting factors controlling erosion soil degradation processes may affect the normal tree and shrub development and inversely vegetation can modulate the velocity and intensity of soil development or denudation a dendrogeomorphological approach can be used to study these interactions allowing to obtain a date and estimate mean or specific erosion rates this is especially useful in an unrecorded badlands and gullied environments where the scarce vegetation may be the only proxy available to quantify the different geomorphic processes which have occurred this paper provides a fundamental review of the dendrogeomorphological methodology applied to erosion measurement in badlands focusing on the response of the vegetation to the geomorphic processes this paper a describes the methodology developed to estimate erosion rates with exposed roots b shows new advances through case studies and finally c discusses future lines of research to reduce methodological uncertainties and for making dendrogeomorphology more widely applicable

space time variability of denudation rates at the catchment and hillslope scales on the tyrrhenian side of central italy studies on denudation rates can provide insight into the influence of climate change tectonics and human activities on landscape evolution research performed in central italy has shown considerable spatial variability of denudation rates in the major river basins these studies have focused mainly on the tyrrhenian side of the italian peninsula where plio pleistocene marine deposits filling nw se elongated sedimentary basins have been uplifted during the quaternary up to several hundreds of meters above present sea level small sub catchments developed on clays are affected by sharp and or rounded edged badlands i e calanchi and biancane representing denudation hot spots in the present day morphoclimatic framework in this paper we analyze the relationships between indirectly estimated denudation rates at the catchment scale and field monitoring data at the hillslope scale we attempt to better understand and quantify all hillslope processes that contribute to seasonal variability of denudation to help with predicting the net input from hot spots to the overall estimated sediment yield at the basin outlets at the hillslope scale we discuss in particular the variability of denudation rates at calanchi and biancane badlands as a function of their different morphoevolution

msi morphometric slope index for analyzing activation and evolution of calanchi in italy article i nfo the calanchi singular calanco are a typical example of italian badlands widespread in areas with hills of clay rich sediments and rocks they appear as a very dense and rapidly evolving drainage system characterized by an alternating pattern of narrow furrows and sharp crests the calanchi can be considered as small hydrographical basins characterized by two possible drainage patterns parallel and dendritic the two patterns show both linear and areal erosion processes in this study calanchi with dendritic drainage patterns were analyzed in three different areas representative of the italian peninsular atri in the abruzzi region mount ascensione in the marche region and orcia valley in the tuscany region for each calanchi the pre erosion topographic surface was reconstructed and the value of msi morphometric slope index was calculated for the surface the volume of eroded material was estimated by comparing the pre calanchi and present surfaces we assumed that slope morphometry influences the type of erosion processes and the efficacy of these processes with respect to the amount of eroded material is a func tion of their duration we deduced that calanchi inception was contemporaneous because the duration of the processes was common to all landforms and probably due to a common climate input moreover the relations among msi eroded volume and erosion processes indicate that over a long period areally distributed surface processes contribute more to total sediment yields than channel flows

the paradox of drowned reefs and carbonate platforms shallow water carbonate platforms and reefs are drowned when tectonic subsidence or rising sea level outpaces carbonate accumulation and benthonic carbonate production ceases drowned platforms are common in the geologic record but they present a paradox if one considers rates of processes involved during the early holocene when sea level rose at rates of 6 000 to 10 000 m yr mm 1 000 yr most reefs and platforms were outpaced by the rising sea during the late holocene with sea level rising 500 to 3 000 m yr in the atlantic caribbean area reefs and platforms started to recover built to sea level and prograded seaward 1 000 m yr is thus a conservative estimate of the average growth potential of modern reefs and platforms independently accumulation rates of prograding platforms in the geologic record suggest growth potential in excess of several hundred microns per year the growth potential of 1 000 m yr exceeds any relative rise of sea level caused by long term processes in the geologic record newly formed ocean crust subsides at a maximum of 250 m yr basin subsidence averages 10 to 100 m yr and sea level rises due to increased sea floor spreading amount to less than 10 m yr rapid pulses of relative rise of sea level or reduction of benthic growth by deterioration of the environment remain the only plausible explanations of drowning the geologic record shows examples of both of these processes global mass extinctions of reefs and platforms occurred in the middle cretaceous eustatic rise due to submarine volcanism or desiccation of a small ocean basin and the late devonian global crisis of ocean environment extraterrestrial cause drowning controlled by regional tectonics prevailed in the jurassic and early cretaceous of the tethyan realm and the drowning of mesozoic platforms in the western north atlantic seems to have been dictated by plate tectonic drift to higher latitudes

island arc carbonates characterization and recognition in the ancient geologic record abstract carbonates of island arc origin that are preserved in paleozoic mesozoic terranes of the north american cordillera exhibit a distinctive suite of paleontologic and lithologic features and share a fundamental similarity with limestones forming in modern volcanic arcs this study provides the first detailed synthesis of carbonate depositional systems in island arcs and documents primary sedimentary constituents based on facies relationships and faunal communities models are developed that show patterns in the long term evolution of shallow marine organisms and the construction evolution and demise of carbonate platforms in island arcs a suite of criteria is identified that may be used to differentiate island arc carbonates from limestones that accumulated in other platform settings biogeographic isolation prolonged subsidence steep submarine slopes and tectonic instability of volcanic edifices contribute to the development of relatively high levels of species endemism impoverished normal marine faunas complex provincial affinities and relict biotas in limestones that are characterized by exceptionally thick platform and periplatform sequences fringing and barrier reefs at the shelf margin extensive lagoonal deposits and rapid lateral and vertical facies changes although destructive tectonic and geologic processes in island arcs may hinder determining the original size and extent of the carbonate platform and particular facies types may not be represented e g fringing and barrier reefs may be replaced by sand shoals at the platform margin many characteristics have potential value for identifying carbonates of island arc origin in the ancient rock record apart from being associated with calc alkaline volcanic and volcaniclastic assemblages the most valuable suite of features for recognizing island arc carbonates is marine biotas that exhibit elevated levels of endemism and mixed paleobiogeographic affinities extraordinary thicknesses of platform shallow marine and periplatform carbonates and rapid facies changes between volcanic and carbonate rocks and between shallow and deep water limestones recognizing that an ensemble of features is distinctive within island arc carbonates considerably enhances identification of volcanic arcs in the ancient geologic record and thus improves the likelihood of successfully unraveling the complex geologic history of ocean basins

the role of the hillside in determining the morphometric characteristics of calanchi the example of adriatic central italy abstract a typical example of badlands in the italian peninsula is the calanchi plural of calanco which may be defined as rapidly evolving very dense and hierarchical drainage systems whose genesis is controlled by mineralogical characteristics the granulometric composition of local lithotypes structural conditions hillside gradient and climate in this work some of the morphometric characteristics of the hillside were compared on a statistical basis with those of the drainage network of the calanchi for two large sample areas in adriatic central italy it was possible to demonstrate how the hillside environment strongly affects the activation of the process and the characteristics of the calanchi depending on their morphometric morphometric characteristics in particular the length inclination ratio of the hillside conditions the hydrographic pattern of the calanco system

effect of anisotropy on the paleomagnetic contact test for a grenville dike we report a detailed paleomagnetic contact test for a mafic dike and its tonalitic gneiss host rock in the precambrian grenville province of canada directions of natural remanent magnetization nrm in the country rock were corrected for assumed deflection by the strong magnetic anisotropy due to the rock fabric using the measured anisotropy of laboratory induced thermoremanent magnetization trm the trm ellipsoids have the same principal axes as the anisotropy of magnetic susceptibility ams ellipsoids but the anisotropy of remanence is more pronounced than the ams anisotropy correction moves nrm directions in the unbaked zone almost 20 bringing them close to typical grenvillian paleofield directions the anisotropy seems to be controlled by multidomain rather than single domain magnetic minerals nrm directions from the baked gneiss near the dike contact after anisotropy correction agree well with the nrm directions from the chilled margin of the early cambrian 570 3 ma dike this positive baked contact test is augmented by the presence of a hybrid zone in which country rock nrms are increasingly overprinted by the dike nrm as one moves from the unbaked toward the baked zone the dike nrm is therefore primary however the virtual geomagnetic pole vgp for the dike nrm 51 n 131 w dp 10 dm 12 n 24 samples or 41 n 153 w dp 13 dm 18 n 4 chilled margin samples does not fall near most established cambrian paleopoles post emplacement tectonic movement of the dike is unlikely it may be that the dike cooled and acquired trm during a geomagnetic field excursion because of its geologically short cooling blocking period of a few tens of years

thirty years of studies on badlands from physical to vegetational approaches a succinct review the scientific subjects addressed in the research into badlands since the publication of bryan and yair s book bryan r b and yair a editors 1982 badland geomorphology and piping geo books norwich 408 pp are briefly analysed with a steadily increasing number of papers per year attention to some aspects such as runoff generation piping and the role of lithology and soils varied whereas the percentage of studies on erosion rates increased steadily over time vegetation was not a subject of research in early papers as most of the papers dealing with vegetation were rather descriptive and published in local or limited diffusion media which contrasts with the present situation when about 40 of papers published in international journals about badlands address some aspect of vegetation however the growth in the attention paid to vegetation and erosion rates was not linked to any increase in papers dealing with badland reclamation badlands are now seen as a group of systems with some common features but diverse dynamics depending mainly on climatic and lithological drivers more attention should be paid in the future to investigating the evolution of these landforms over time mostly through modelling studies whereas emerging technologies foster detailed analyses that were not possible formerly although some badland areas determine on and off site environmental issues others are spots of landscape diversity that merit protection rather than reclamation

effects of land use changes on badland erosion in clayey drainage basins radicofani central italy abstract hillslopes of the radicofani area in the upper valley of the orcia river southern tuscany region italy consist mainly of early pliocene clayey sediments and are widely affected by frequent badland erosion reforestation with frugal conifers has been carried out in the area over the last 50 years the goal of the present study is to evaluate the impact of reforestation and land use change on erosion rates in nine small drainage basins through a multidisciplinary approach geological geomorphological hydrological and land use characteristics were analyzed by a diachronic confrontation between pre reforestation 1954 and post reforestation 2007 situations aerial photo interpretation and processing in gis allowed us to quantify changes in areas affected by badland erosion land use and variations in erosion rates moreover dendrometric data were gathered from 18 circular sample plots in forest stands of 40 years old this allowed us to evaluate both the adaptability of different forest species to the clayey substrate and reforestation fragmentation the differences between the pre and post reforestation situations led to increases in arable land and forest areas and considerable decreases in erosion rates and badland areas however no significant correlation between the erosion rates and the forest area emerged due to the excessive fragmentation of reforestation cores and relatively small reforested surfaces land reclamation seems to have played a more important role in reducing erosion in the clayey substrate the integrated method presented here is an important tool useful to understand the morphological dynamics of badlands in relation to forest vegetation and for land planning and management

detachment and infiltration variations as consequence of regolith development in a pyrenean badland system the araguas experimental catchment has been monitored to study badland dynamics in the central pyrenees previous studies of weathering processes within the catchment reported strong regolith dynamics associated with seasonal variations in the temperature and moisture regimes a preliminary analysis of hydrological response and suspended sediment transport data recorded at a gauging station also demonstrated seasonal trends the main objective of the present study is to understand the effect of regolith dynamics on sediment detachment and infiltration processes based on field studies using simulated rainfall the experiment design was based on seasonal differences in the physical conditions of surface regolith and the general trends of hydro sedimentological responses rainfall simulations were conducted on small plots using a pressure nozzle similar experimental rainfall conditions were set for all plots rainfall intensity around 45 mm h 1 the results showed strong variations in the infiltration and detachment responses closely associated with the regolith conditions and crusting development infiltration showed seasonal differences in time lag and intensity average infiltration rates ranged from very low 2 05 mm h 1 to moderated high values 44 04 mm h 1 associated to regolith development conditions maximum sediment concentration as an indicator of particles produced by detachment also ranged from moderate 3 g l 1 to extreme values 145 g l 1 mean and minimum infiltration rates showed negative correlations with initial moisture content sediment concentration showed a positive correlation with time lag ponding and sealing time and a negative correlation with initial moisture in terms of seasonal trends infiltration and erosion responses were relatively stable during spring and autumn whereas wide variations were recorded in infiltration rates and sediment detachment during summer and winter as a general conclusion the obtained results indicate that seasonal differences in detachment and infiltration depend on the nature of regolith development copyright 2009 john wiley sons ltd

badland dynamics in the central pyrenees temporal and spatial patterns of weathering processes the genesis and development of badlands is controlled by bedrock lithology topography and climate the development of badlands in the central spanish pyrenees is favoured by the presence of marls and a climate with a marked seasonality the combination of these factors results in active hydrosedimentological processes the aim of the present work was to study the dynamics of badlands in the central pyrenees with a focus on the temporal and spatial patterns of the dominant weathering processes the study area was a small mountain catchment and we focussed on the continuous observation of a number of physical parameters that control regolith development and weathering processes samples collected from different depths at sites with different aspects enabled temporal comparisons of the factors involved in the development of surface regolith that can be considered as indicators of the weathering of the marls these indicators were then related to environmental variables moisture and temperature atterberg limits were established and related to moisture content to explain slope dynamics and related processes finally analyses of carbonate content were performed in the laboratory the results validate the employed methodology supporting our description of weathering processes the established chronological sequence and the relation of these processes to climatic and topographic parameters the results obtained since january 2004 show that the chosen indicators are sensitive to seasonal dynamics variations in temperature and water supply and slope aspect the development and dynamics of regolith on north facing slopes is more active than that on south facing slopes freeze thaw is the main weathering process on north facing slopes while south facing slopes are dominated by the development of crusts associated with wetting drying processes washing effects and lower temperatures upon north facing slopes mean that the dissolution of carbonates is more pronounced in such areas compared with south facing slopes especially within the upper layers of the regolith copyright 2006 john wiley sons ltd

vertic features in a soil catena developed on eocene marls in the inner depression of the central spanish pyrenees scientific interest in marls has expanded in recent years especially in regard to erosion rates weathering processes and stabilization of the resulting sediments however information regarding the properties and evolution of overlying soil is relatively scarce this work analyzes the relationship between mechanical properties and standard properties of soils developed on eocene marls in mountainous regions of the southern central spanish pyrenees it also examines whether these soils have the vertic features traditionally ascribed to them and how these features may vary along a catena the water holding capacity of the soils exhibits a typical catena related trend that increases progressively from low values in upper slope profiles to higher values for the middle slope and valley the soils have a high percentage of silt sized particles quartz and calcite are the main mineralogical components of the fine earth fraction illite represents the major component of the clay fraction the linear extensibility and atterberg limits are positively and significantly correlated to clay content low liquid limit usually less than 30 low soil aggregate stability lower than 25 in ap horizons and high subsidence values n 0 7 are likely factors in the high dispersivity and sliding risk observed for the soils these factors also explain the presence of buried soils and lithological discontinuities in lower slope profiles as well as the relatively limited degree of soil evolution despite a relatively humid climate low porosity mainly of vesicular type and a poor structure facilitate saturation in the wet season and lead to soil reduction processes especially within deep soil horizons along lower parts of hillslopes simulated wetting and freezing treatments were shown to fracture the unaltered marls into small fragments demonstrating the soil s susceptibility to physical weathering given moderate clay content absence of smectites and moderate soil extensibility cole 0 06 cm cm 1 in most horizons topsoil cracking in lower slope profiles is apparently caused by high rates of evaporation during the dry season the soils described here did not meet the requirements of vertic horizons but most meet the diagnostic criteria of having a protovertic horizon despite the absence of swelling and shrinking clays

origin of the magnetization of the wichita mountains granites oklahoma summary the magnetization of the cambrian wichita mountains basement complex consists of several components two of which are shown to be significant the residual primary remanence is associated with the original titanomagnetite and the dominant secondary component is carried by minerals of the ilmenite haematite series the latter has been acquired at temperatures up to 300 c as a result of the regional hydrothermal alteration during late palaeozoic the secondary remanence is of thermochemical origin and carries a memory of a variable ambient field direction which may be modelled as a resultant of the geomagnetic field direction contemporaneous with the hydrothermal process and of the direction of the magneto static field of the primary titanomagnetite although the destruction of the original presumably cambrian remanence has been extreme in a few cases its direction appears to have been recovered the results are complicated by the possibility of a self reversal of secondary remanence as well as geomagnetic field reversal an issue unresolved by the investigation relates to the possibility of generation of magnetite by heat treatment of rock material in the laboratory it is generally concluded that it is difficult to recover the original cooling thermoremanence direction in an igneous intrusion which has been subjected later in its life to extreme conditions of hydrothermal alteration

relationships between suspended sediment concentrations and discharge in two small research basins in a mountainous mediterranean area vallcebre eastern pyrenees abstract the relationships between suspended sediment concentrations and discharge were studied at the can vila 0 56 km2 and ca l isard 1 32 km2 sub basins of the vallcebre research area eastern pyrenees during a period of 5 years that included 67 events of diverse magnitude abandoned agricultural fields and forests are the main land use in the can vila basin whereas the ca l isard basin is mainly forested though there are also some heavily eroded landscapes badlands the most frequent events were of a single discharge peak although double and multiple peaked events were also recorded clockwise positive hysteretic loops occurred in both catchments mainly during the wet seasons when precipitation was of moderate intensity average of 18 mm h 1 and baseflow before the event was rather high average for ca l isard 8 1 l s 1 km 2 and for can vila 11 76 l s 1 km 2 the bulk of stream discharge came from saturated areas whereas sediments came mainly from the stream channels counter clockwise negative hysteretic loops were much more frequent in the ca l isard basin mainly in summer when rainfall intensity was high average of 32 5 mm h 1 and baseflow was low average for ca l isard 0 94 l s 1 km 2 and for can vila 0 73 l s 1 km 2 most of the water and sediment came from the badlands eight shaped loops occurred in transition periods mainly in the ca l isard basin

permian carbonate platform development in an island arc setting eastern klamath terrane california the mccloud limestone eastern klamath terrane california represents one of several areas of carbonate deposition in an early permian island arc west of north america the mccloud formed isolated platforms about 30 km long platform development began on volcanic highs as bank deposits and ramps of mixed volcaniclastic and carbonate sediments continued bank growth resulted in slope deposits of argillaceous spiculitic wackestone limestone conglomerates and limestone turbidites lateral growth of platforms occurred by progradation of slope deposits and platform top deposits consisted mainly of packstone and wackestone of subtidal origin rapid subsidence of platforms resulted in sediment accumulation rates of up to 30 cm 1000 yr the data presented here help to characterize the tectonosedimentary regimes of island arcs in general

paleomagnetism and age of mafic plutons wichita mountains oklahoma a paleomagnetic reconnaissance 43 samples of the raggedy mountain gabbro group which is comprised of a layered complex of anorthosites anorthositic gabbros and massive gabbro shows 1 stable remanent magnetization and 2 consistent directions which differ significantly from those of the nearby cambrian wichita granite group with exception of one site near the granite contact these results suggest a precambiran age for the gabbro group the difference in pole positions between the granitic and mafic groups demonstrates that the plutonic episodes responsible for the mafic and granitic magmas are significantly separated in time models of formation of the wichita aulacogen should be altered to account for the difference in time between the mafic and silicic plutonism

lithological properties and weathering response on badland hillslopes rills and rill networks are important geomorphological features in clay rich badland areas rill network geometry varies with climate and topography but the lithological properties are also critical rill systems on mudrock and sandstone in alberta badlands were studied to examine progressive changes in material properties as smectite rich mudrocks and sandstones undergo weathering and the impact of seasonal changes in precipitation patterns three plots with well developed rill systems on each unit were examined in may 2001 and 2003 geometric properties were determined along a dense grid and surface and subsurface samples were analyzed for texture crust structure sem mineralogical composition xrd content of major elements xrf aggregate stability and moisture content the rill width depth ratio decreased from 2001 to 2003 on mudrock rill networks the popcorn crust found in 2001 changed to a thin dense crust in 2003 2001 materials had higher na and ca concentrations and the 2003 materials have higher al k concentrations unweathered mudrock shards were subjected to incremental weathering in controlled laboratory conditions depending on moisture input different crust types developed on materials after 10 wetting drying cycles material responded to different amounts of precipitation by alteration from swelling to dispersion

lithostratigraphic and allostratigraphic framework of the cambrian ordovician potsdam group and correlations across early paleozoic southern laurentia the potsdam group is a cambrian to lower ordovician siliciclastic unit that crops out along the southeastern margins of the ottawa graben from its base upward the potsdam consists of the ausable hannawa falls and keeseville formations in addition the potsdam is subdivided into three allounits allounit 1 comprises the ausable and hannawa falls and allounits 2 and 3 respectively the lower and upper parts of the keeseville allounit 1 records early to middle cambrian syn rift arkosic fluvial sedimentation ausable formation with interfingering mudstone arkose and dolostone of the marine altona member recording transgression of the easternmost part of the ottawa graben rift sedimentation was followed by a middle cambrian climate change resulting in local quartzose aeolian sedimentation hannawa falls formation allounit 1 sedimentation termination coincided with latest middle cambrian tectonic reactivation of parts of the ottawa graben allounit 2 lower keeseville records mainly upper cambrian quartzose fluvial sedimentation with transgression of the northern ottawa graben resulting in deposition of mixed carbonate siliciclastic strata of the marine riviere aux outardes member sedimentation was then terminated by an earliest ordovician regression and unconformity development allounit 3 upper keeseville records diachronous transgression across the ottawa graben that by the arenigian culminated in mixed carbonate siliciclastic shallow marine sedimentation theresa formation the contact separating the potsdam group and theresa formation is conformable except locally in parts of the northern ottawa graben where the presence of localized islands and or coastal salients resulted in subaerial exposure and erosion of the uppermost potsdam strata and accordingly unconformity development

discrepancies between experimental observations in natural and synthetic samples abstract the evidence is reviewed by comparing the data obtained from synthetic samples with those derived from natural samples of magnetic minerals present in rocks it is shown that there are many issues which are still unresolved some suggestions are made concerning the future direction of rock magnetic research such as the need for intensified studies of natural samples the aim of this note is not to disclose anything new but rather to open up some lines of thought and draw attention to questions and ideas that may have been lurking in our minds from the very beginnings of paleomagnetism

paleomagnetic and petrologic study of the age origin and significance of early and late paleozoic events in the long mountain granite wichita mountains oklahoma the cambrian long mountain granite exposed in the western wichita mountains oklahoma is red granophyric alkali feldspar granite the red granite abruptly transitions into a green granite in the subsurface both red and green granites have similar geochemical signatures anisotropy of magnetic susceptibility analysis shows that the green granite retains a primary magnetic fabric that is consistent with the sill like emplacement of the wichita granite group demagnetization of green granite specimens yields a characteristic remanent magnetization chrm residing in magnetite with east declinations and moderate down inclinations the paleopole 9 0 n 314 6 e is interpreted as a primary cambrian thermal remanent magnetization or an early magnetization related to deuteric hydrothermal alteration the paleopole position is consistent with some other poles for cambrian igneous rocks in southern oklahoma but is to the southwest of the cambrian part of the apparent polar wander path the red granite contains abundant secondary hematite that occurs in fractures as grain boundary coatings and along cleavage and exsolution planes in alkali feldspars the iron in the hematite appears to be sourced from the oxidation of primary magnetite and ilmenite and the breakdown of silicate ferromagnesian minerals the red granite has about two orders of magnitude lower magnetic susceptibility and natural remanent intensity than the green granite the magnetic fabric is interpreted as an alteration fabric the chrm of red granite has southeast declinations and shallow inclinations and is interpreted as a chemical remanent magnetization crm residing in hematite the paleopole 44 9 s 304 9 e falls near the 290 300 ma segment of the north american apparent polar wander path which is consistent with inferred timing of exposure of the long mountain granite the crm is interpreted to have been acquired during alteration by low temperature weathering fluids near the surface during the late paleozoic the results from the red granite are not consistent with alteration caused by widespread paleoclimatic conditions in the late permian and they are interpreted as related to local tectonic and or weathering events

statistical significance of the fold test in palaeomagnetism summary the significance of the change in direction dispersion on applying the fold test in palaeomagnetism is used as the criterion for deciding whether or not the fold test has statistical significance a set of tables is compiled which can be used for quick application of the test

diagenetic apatite character and in situ ion microprobe u pb age keeseville formation potsdam group new york state an occurrence of diagenetic fluorapatite cement is documented within the cambro ordovician keeseville formation potsdam group near chateaugay in new york state the fluorapatite cement occurs as stratiform layers within ephemeral fluvial quartz arenites which have been reworked by aeolian processes prior to burial the paragenetic sequence includes the following compaction of dust rimmed grains quartz cementation minor kaolinite fluorapatite cementation followed by secondary dissolution porosity and telogenetic hematite cementation mesogenetic illitization of kaolinite may have taken place prior to or following fluorapatite cementation the fluorapatite occurs as elongated bladed crystals that characteristically contain ladder like inclusion rich cores running parallel to crystal length surrounded by clearer rims and larger blocky crystals towards the middle of interstices in situ shrimp analyses of blocky fluorapatite crystals yield a u pb age of 486 29 ma indicating that the cement for

retreat of carbonate platforms response to tectonic processes a seamarc ii and seismic reflection investigation of the deep water margins of carbonate banks in the southeast bahamas has documented the retreat of these isolated platforms since mid cretaceous time this retreat is in sharp contrast to prograding carbonate platforms in the passive northwest bahamas and provides an initial framework within which to view the response of carbonate platforms to tectonic processes processes of retreat include large scale 50 60 km step back of platform margins during the mid cretaceous tectonic subsidence and downfaulting during the late tertiary and large scale collapse of platform margins which may be an active process step back during the mid cretaceous correlates with a global tectonic pulse of ocean crust formation and relative sea level rise downfaulting may be a response to either late tertiary lithospheric bending during subduction and or block rotation along the north american caribbean plate boundary and collapse may be related to earthquake shocks generated by active plate tectonic collision between the southeast bahamas and hispaniola

carbonate platform growth influenced by contemporaneous basaltic intrusion albian of larrano spain carbonate platform growth in active tectonic settings may be strongly influenced by the structural evolution of the basin including volcanic activity in this paper the sedimentary tectonic evolution of the duranguesado carbonate platform larrano in northern spain is described and an evolutionary depositional model is presented the albian duranguesado carbonate platform deposits are dominated by rudist and coral limestones with small intervening argillaceous limestone filled troughs 10 30 m deep the platform succession is divided into two parts the lower platform deposits were intruded by volcanics and tilted before the deposition of the upper platform succession a volcanic vent plug filling an upward flaring pipe occurs in the lower carbonate platform succession the timing of intrusion is well constrained to the early albian tectonic extension and active deep seated strike slip faults induced magma ascent at a fault intersection sedimentological analysis of these areas indicates that before volcanic intrusion they acted as weakened zones of extension and were slightly more subsident basinal areas these sites contain anomalous accumulations of siliceous sponge spicule deposits linked to the release of hydrothermal fluids on the sea floor after the phase of intrusion tilting and erosion of the platform and its associated volcanic products occurred as the intrusion cooled the platform downwarped leading to the formation of an overlying perched capping basin bordered by carbonate platforms over the volcanic plug carbonate mounds grew on local palaeohighs the presence of strike slip and magma emplacement in the duranguesado platform is related to movements between the iberian and european lithospheric plates which were accommodated by rotation and lateral movement of the crust along wrench faults

geomorphic agents versus vegetation spreading as causes of badland occurrence in a mediterranean subhumid mountainous area abstract previous evidence on the chief role of physical weathering on badland development in the vallcebre area south eastern pyrenees led to the study of the amounts of energy available for the main geomorphic agents and to analyze the results in the light of the patterns of vegetation cover and species distribution in order to explain both the occurrence of these badland forms and their preference for north facing shady hillslopes results showed that the weathering potential provided by freezing is about two orders of magnitude greater than rainfall kinetic energy and that the former strongly depends on hillslope aspect the study of vegetation demonstrated that vegetation is poorer in cover and species composition on shady hillslopes than on sunny ones spontaneous revegetation of these surfaces being restrained by cold thermal conditions rather than by water availability these results show that the occurrence of these badland areas depends on montane climatic attributes that control geomorphic and biological processes and that are different from those that promote the occurrence of badlands in dry mediterranean areas the preference for northern aspects provides evidence for these differences

soil genesis and evolution on calanchi badland like landform of central italy abstract calanchi are badland like erosional landforms common in the mediterranean region which form from accelerated erosion processes the calanchi slopes naked or differently vegetated can be considered as formed by different ecological tesserae originated by the mutual interaction of several factors such as erosion geomorphology microclimatic conditions vegetation ground cover and pedogenesis however information about pedogenesis is rather scarce mainly because the soils developing on calanchi slopes are incessantly disturbed by erosion processes to understand the role of soil evolution on landslide erosion we considered three land facets each one made up of four tesserae t1 to t4 which represented the different steps of soil and vegetal evolution of calanchi the soil of each tessera was described sampled by genetic horizons and the samples were characterized for their physical mineralogical and chemical properties field observations and laboratory data suggest that pedogenesis in the calanchi badlands may progress until a critical threshold indeed advanced plant colonization and solum development improve soil structure increase soil organic matter and favor redistribution of nutrients along the profile the improvement of structure at depth fosters water storage and clay dispersion through soil leaching and reduction of ionic strength of the soil solution making soil less stable depending on the slope gradient the soil weight acquired during rainfall events may trigger landsliding mudflows or collapses that rejuvenate the surface

the sediment budget of a highly dynamic mesoscale catchment the river isabena the paper presents the sediment budget of the isabena basin a highly dynamic 445 km2 catchment located in the central pyrenees that is patched by highly erodible areas i e badlands the budget for the period 2007 2009 is constructed following a methodology that allows the interpolation of intermittent measurements of suspended sediment concentrations and enables a subsequent calculation of sediment loads data allow specification of the contribution of each subbasin to the water and sediment yield in the catchment outlet mean annual sediment load was 235 000 t y 1 specific sediment yield reached 2000 t km 2 y 1 a value that indicates very high sedimentary activity especially in the case of villacarli and lascuarre subcatchments were most badlands are located the specific sediment yield obtained for the entire isabena is 527 t km 2 y 1 a high value for such a mesoscale basin results show that a small part of the area i e 1 controls most of the catchment s gross sediment contribution sediment delivery ratio ratio between sediment input from primary sources and basin export has been estimated at around 90 while in channel storage represents the 5 of the annual load on average the high connectivity between sediment sources i e badlands and transfer paths i e streamcourses exacerbates the influence of the local sediment production on the catchment s sediment yield a quite unusual fact for a basin of this scale

relationships between a new slope morphometric index and calanchi erosion in northern sicily italy the italian badlands or calanchi are common landforms in mediterranean areas including central and southern italy calanchi landforms may be compared to small hydrographic basins these landforms are characterised by dense hierarchical and rapidly evolving drainage systems carved into steep clayey slopes and by a sharply alternating pattern of furrows and narrow generally sharp crests this work presents a study of morphometric characteristics and a statistical analysis for two sites in northern sicily italy on outcrops of silty clay deposits affected by active erosion processes which give this area a typical calanchi landscape in particular factors closely linked to the characteristics of the hydrographic network and slope morphometry were considered and analysed the initial geometry of the slopes was reconstructed and statistically compared with that of the current calanchi slopes including the drainage network a new morphometric index morphometric slope index msi was defined to represent the initial slope geometry as a whole this index was found to be effective in defining the structure of hydrographic networks summarising the characteristics and type of slope evolution and quantifying the rate of soil erosion the rate was determined based on both linear gully erosion and areal landslides sheet and rill erosion morphogenetic processes and our analysis based on msi indicates the dominance of areal erosion msi could also be used for basins larger than calanchi to represent the characteristics of geomorphic processes

palaeomagnetism of early cambrian brigus red shale eastern newfoundland abstract studies of the early cambrian brigus br red shale exposed in conception bay yielded a single stable mean remanence direction of d 265 i 58 reverse polarity before tilt correction and d 279 i 48 k 47 95 6 9 forn 7 sites 25 samples after correction for gentle tilt the corresponding north pole palaeopole position is 27 s 51 e dp dm 6 9 this magnetization is characterized by a linear vector trajectory at higher unblocking temperature t ub spectra 400 680 c the magnetization directions at the low t ub range 400 c are more variable from sample to sample although they typically have steep downward inclinations with no evidence of kiaman overprinting marginal but not statistically significant improvement k 44 77 in the grouping of site means after tilt correction suggests that the predominant univectorial westerly remanance was probably acquired after deposition based on both geological and magnetic evidence the brigus shale formation appears to be remagnetized during siluro devonian times the position of the far sided antipole br 27 n 129 w located in the vicinity of the pole for the cambrian morrison river formation mr at 20 n 146 w which is discordant from the younger palaeozoic late ordovician carboniferous poles reported for the avalon zone is fortuitous since the magnetization of br is most likely secondary the magnetization is younger than the iapetus closure date determined geologically late ordovician consequently the displacement of the avalon zone with respect to the north american craton cannot be estimated the width of the proto atlantic ocean cannot be calculated

dispersed remnants of a northeast pacific fringing arc upper paleozoic terranes of permian mccloud faunal affinity western u s two fragmentary subparallel belts of terranes within the western north american cordillera contain upper paleozoic rocks and are characterized by contrasting lithotectonic assemblages and contrasting permian faunal affinity these two belts are a volcanic arc related successions of permian mccloud faunal affinity mccloud belt and b subduction related accretionary complexes of permian tethy an faunal affinity cache creek belt this paper supports the hypothesis that the fragmentary terranes of the mccloud belt once constituted parts of a northeast pacific fringing arc system and in constrast to some earlier interpretations concludes that the volcanic arc evolved above an eastward dipping subduction zone the absolute distance between this arc and western north america during the late paleozoic cannot be constrained however there is little evidence to suggest closure of a major 10 km ocean basin or protracted periods of westward dipping subduction parts of devonian to permian volcanic island arc sequences of the western u s cordillera are represented in the northern sierra eastern klamath bilk creek grindstone and chilliwack terranes these scattered volcanic arc remnants share several fundamental characteristics 1 the sequences were constructed across continental affinity basement assemblages 2 they underwent similar tectonic evolution during late paleozoic time such as coeval pulses in volcanism and related depositional histories 3 they contain early permian mccloud type fauna of distinctive biogeographic affinity 4 mccloud belt terranes are spatially and possibly genetically related to westward lying accretionary complexes of the cache creek belt which contain fragments of upper triassic blueschist and permian limestone blocks bearing tethyan permian fusulinids and corals based on the presence of distinctive early permian mccloud fauna the island arc remnants discussed in this paper are referred to as the mccloud belt the similarities between mccloud belt terranes suggest that they were once parts of a long lived late paleozoic volcanic arc complex the stratigraphy of these terranes records the tectonic evolution of the volcanic arc volcanism within the paleozoic arc began as early as the early devonian and was succeeded or accompanied by carbonate and epiclastic sedimentation during the middle and late devonian an influx of detritus derived from sedimentary and metasedimentary rocks during the late devonian and mississippian records the uplift and erosion of arc basement sequences an event that was at least locally accompanied by ongoing volcanism a pulse in volcanism during the pennsylvanian and coeval uplift led to the establishment of shallow marine and deltaic volcanogenic and carbonate sedimentation and locally subaerial exposure which persisted into the early early permian elsewhere during the early permian shallow water carbonate deposition was established with only minor influx of volcanogenic debris during the late permian and locally as early as late early permian a major pulse in volcanism occurred and is now represented by voluminous sequences of volcanogenic debris and lavas most of these sequences are overlain by upper triassic carbonate platformal sequences arc volcanism was recorded at least locally until the middle jurassic paleomagnetic data are used to constrain a schematic pre cretaceous reconstruction of these volcanic arc sequences and their associated subduction assemblages the inferred paleogeography of island arc sequences and the adjacent accretionary terranes suggests that volcanism occurred above an east dipping subduction zone with a long lived paleogeographic relation to north america the current structural position of these terranes is largely the result of mesozoic and locally younger deformation

mapping badland areas using landsat tm etm satellite imagery and morphological data abstract soil erosion is the most influential component of land degradation for its strong impacts on both natural and agricultural environments in order to support effective intervention and recovery policies for eroded areas monitoring techniques should take into account the space time variability of the processes involved and make use of assessed mapping methodologies as baseline criteria for studying the dynamics of landform development when using multispectral data for mapping eroded areas low spectral separability is a significant limit in areas with complex features where soil materials are frequently remixed by surface runoff since multispectral satellite images are a valuable data source for multi temporal analyses of erosion processes at the medium scale we assessed how accurately a badland area can be identified from landsat tm and etm data a protocol for an optimal mapping was built up by testing the performance of different supervised algorithms and input layers spectral and morphological tests were carried out in a well known badland area of basilicata italy with an extension of 8000 ha results obtained from the use of spectral bands with and without thermal channel and principal components returned an overall accuracy ranging from 53 for classification on first three components to 72 for classification on all bands from tm with low values for the kappa coefficient 0 30 0 50 showing that the spectral information alone are insufficient to accurately identify badland areas in order to improve mapping we found that the integration of slopes and aspects derived from a digital elevation model dem can overcome problems inherent to the low separability of spectral signatures the use of morphological data was tested for different classification algorithms and integration approaches in discriminating badlands the better performing algorithm was mlc maximum likelihood classifier and the best results were obtained by integrating all seven bands including tir with slope and aspect maps as input within the classifier a 0 85 and k 0 75 for both the sensors we selected such parameters because they play an important role in characterising badlands of study area from a morphological perspective but the proposed approach is also conceptually simple and can be easily exported to other areas the obtained results support the hypothesis that the combined use of remote sensing imagery and auxiliary morphological data significantly improves the mapping of badlands over large areas with heterogeneous features thus providing a useful methodology for long term studies on soil erosion processes

temporal distribution of suspended sediment transport in a humid mediterranean badland area the araguas catchment central pyrenees abstract this paper analyses the temporal patterns of suspended sediment yield in the araguas catchment central spanish pyrenees a small experimental catchment with extensive badlands the catchment has been monitored since 2004 to study weathering erosion and hydrological and sediment responses to understand the superficial dynamics of a badland area in a relatively humid environment the development of badlands in the central spanish pyrenees is favoured by the presence of marls and a markedly seasonal climate the continuous observation of selected physical parameters and environmental variables enables us to establish seasonal patterns of weathering processes and identify those factors that control regolith development freeze thaw cycles in winter and wetting drying in spring summer are the main processes involved in regolith weathering thereby controlling slope development in combination with rainfall related erosion processes the 64 floods recorded during the study period december 2005 to january 2007 were used for a hydrosedimentological analysis the main observed features indicate that the araguas catchment reacts to all rainfall events resulting in steep rising and recession limbs on the hydrograph and a very short time lag floods show high suspended sediment concentrations and a heterogeneous temporal distribution related to seasonal variations in surface runoff production these differences increase the degree of complexity involved in studying sediment response suspended sediment concentration and transport mainly depend on rainfall volume maximum rainfall intensity peak flow and runoff occurrence finally the similarities among the obtained hydrographs sedigraphs and hyetographs in combination with the rapid response of most of the floods suggest a large contribution of overland flow derived mainly from infiltration excess runoff upon badland areas accordingly the significant correlations obtained between rainfall intensity and sediment concentration mainly during the dry season which suggest a single source area for both runoff and sediment also support the hypothesis of hortonian hydrological response within badland areas

lithology controls the regional distribution and morphological diversity of montane mediterranean badlands in the upper llobregat basin eastern pyrenees abstract badlands are pervasive in a wide range of environmental conditions across the mediterranean region including arid semiarid and humid environments on montane cold subhumid and humid mediterranean landscapes harsh thermal conditions on north facing hillslopes favour intense bedrock weathering by freezing and impose serious constraints on plant colonization the above are the customary arguments to explain the high abundance of montane badlands on north exposed shady aspects we studied the distribution and morphological diversity of badlands in the upper llobregat basin catalan pyrenees ne spain using remote sensing information high resolution orthophotos and complementary landsat 8 imagery digital elevation data and regional information on lithology badlands extend over about 200 ha in the upper llobregat basin and occur on two different parent materials swelling smectite rich continental garumnian lutites of late cretaceous age and nonswelling illitic marine eocene marls vegetation assessed by remote sensed vegetation greenness is less developed on north facing badland slopes however badland slope aspect distribution varies considerably with lithology while badlands on eocene marls show preferential distribution on north facing shady slopes badland occurrence on garumnian lutites does not reveal clear slope aspect anisotropy patterns lithology also affects slope gradient with badlands on eocene marls showing rougher topography 30 40 average slope angle than on garumnian lutites 20 30 badland morphological differences induced by lithology are discussed in terms of the greater weathering susceptibility and slope instability of the swelling smectite rich garumnian lutites than of the nonswelling eocene marls elevation which broadly controls annual precipitation and winter air temperature within the region shows no clear influence on badland distribution overall our results reveal lithology as the main factor controlling badland distribution and morphological diversity under the montane mediterranean conditions of the upper llobregat basin

tectonic and volcanic influences on the development and diachronous termination of a tertiary tropical carbonate platform abstract the demise of carbonate platforms has variously been related to factors such as tectonics influx of clastic material and environmental stress sometimes in combination with eustatic fluctuations however the precise controls on foundering of platforms are often poorly understood in sulawesi indonesia the extensive syntectonic tonasa carbonate platform of eocene to middle miocene age developed to the west of a volcanic arc and is overlain by middle to upper miocene volcanics these carbonates provide a unique opportunity to study the effects of tectonic and volcanic activity on the development and subsequent demise of a carbonate platform detailed field and laboratory analysis of the tonasa formation reveal that the shallow water deposits of the tonasa carbonate platform had their greatest areal extent in the late eocene although a variety of factors influenced platform development tectonics and volcanism were particularly important influencing platform evolution and diachronous termination in four main ways 1 during the paleogene calc alkaline volcanic activity limited the eastward lateral extent of the platform but had little effect on carbonate sedimentation in western south sulawesi 2 faulting in the latest late eocene resulted in segmentation of the platform and caused localized drowning in hangingwall areas and subaerial exposure on adjacent footwall highs 3 a further phase of faulting in the early to middle miocene just prior to and during the early stages of renewed volcanism in western south sulawesi resulted in reactivation of faults localized tilting of fault blocks formation of new graben and subaerial exposure of faulted footwall highs 4 in the middle miocene the influx of volcaniclastics close to volcanic centers rapidly buried most of the few remaining areas of shallow water carbonates and inhibited renewed carbonate production however carbonate production contemporaneous with volcanism occurred in more distal or localized areas shielded from volcaniclastic input

dynamic evolution of badlands in the roglio basin tuscany italy abstract the roglio basin in the relatively arid central tuscany italy is characterised by the presence of 191 badlands that have developed on pliocene fine grained blue clays a morphometric analysis on the badlands has highlighted that these landforms formation and distribution are primarily related to the steepness of the hill flanks which favour runoff and gravitational processes along with favourable aspects typically the southern ones that experience a stronger solar induced daily thermal variation a detailed physico chemical analysis of the clayey material involved has also been carried out with the specific aim of testing whether this plays a role in the various stages of activity shown by the roglio basin badlands the results indicate that there are no significant differences in the physico chemical properties of an active vs an inactive dormant badland observation and field data however indicate that the dynamic of the roglio basin badlands is strongly controlled by the occurrence of earth flows and the velocity of sediment removal at the bottom of the badlands these two processes variously combined at different intensity in relationship to many local factors are likely to be the main responsible for the different stages of activity shown by the roglio basin badlands

simulating badland erosion with kineros2 in a small mediterranean mountain basin vallcebre eastern pyrenees abstract the ca l isard catchment 1 32 km 2 a sub basin of the vallcebre experimental catchments yields large amounts of sediments about 580 mg km 2 year 1 that are produced in relatively small but very active eroded areas badlands several lines of evidence suggest that there is a delay between sediment production caused by intense summer rainstorms and sediment transport occasioned by the main floods produced by large precipitation events following wet antecedent conditions first a calibration validation exercise was carried out with sediment yield data obtained using containers provided with slot divisors in a badlands micro catchment 1240 m 2 then the model was applied to the main badlands areas in the ca l isard sub catchment for a 4 year period and the simulated sediment yields were compared with the records at the gauging station the test was performed with the generalized likelihood uncertainty estimation glue approach for assessing the uncertainty associated with model predictions which assumes that many parameter sets can give acceptable simulations the results demonstrated the capacity of kineros2 to simulate badland erosion although it showed limited robustness a clear temporal mismatch between erosion and sediment transport and the relevance of sediment stores in the catchment were confirmed while the total weights of sediment were generally under predicted the limited suitability of the area used for calibration or the role of sediment sources not simulated in the approach may account for this shortcoming

how mudrock and soil physical properties influence badland formation at vallcebre pre pyrenees ne spain abstract soils regoliths and their parent materials were investigated in relation to the development of badlands in the pre pyrenees in ne spain on late cretaceous mudrocks under a mountain mediterranean climate whilst all the soils in the area which are developed on mudrocks show a good structure and support a dense plant cover the bare parent materials slake very rapidly giving rise to badlands characterized by high erosion rates several physical chemical mineralogical and micromorphological properties of soils regoliths and related parent materials were analyzed in order to explain their different susceptibility to erosion and to determine which of all these properties are better related to such erosive behaviour only micromorphological and porosity properties were able to explain the erosion susceptibility whilst mineralogical chemical and physico chemical specific surface area properties were not among the aggregate stability tests performed to estimate the relationships of soil components with the susceptibility to erosion the emerson test for macroaggregate evaluation was particularly well suited although no good correlation was found between the emerson test classes and organic matter content we observed that the degree of slaking in organic rich horizons was always lower than in subsurface horizons and regoliths consequently as far as organic rich aggregates are present in the soil surface the influence of water in producing slaking swelling and then erosion will be minimum however when regoliths and rocks are uncovered the influence of water in these particular materials through freeze drying and swell shrinking will give rise to mudrock desintegration leading to accelerated erosion

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

regolith behaviour and physical weathering of clayey mudrock as dependent on seasonal weather conditions in a badland area at vallcebre eastern pyrenees abstract studies on badland areas in the vallcebre basin pyrenees suggest that erosion rates are controlled by the weathering rate of mudrocks to obtain the temporal pattern of physical weathering and its control on the erosive processes monitoring of regolith temperatures at different aspect depth and lithology and periodical determination of regolith moisture and bulk density were carried out changes in surface regolith have also been monitored by means of photographic techniques using an especially designed tripod finally the hydrological and erosive response of the regolith trough the seasons were studied using rainfall simulations the results obtained support and confirm previous knowledge on the role of frost action in mudrock weathering and the role of subsequent regolith development and wetness status on infiltration and runoff generation these seasonal changes of behaviour are so important that they raise serious questions about the validity of observations or experiments carried out in only one season this work confirms that erosion processes are controlled by regolith formation during winter and regolith depletion by storm rainfall erosion during summer spring and early autumn it also raises important points about annual trends of infiltration and erodibility that should be used as guidelines for modelling runoff and sediment production

sediment budget for subalpine watersheds lake tahoe california usa abstract pinpointing erosional hot spots or sediment source areas within a watershed can be difficult because of the highly non linear and episodic nature of effective runoff and sediment transport continuous monitoring of stream networks can provide insight into sediment source areas not possible from routine sampling by capturing episodic events and integrating entire storm events this paper presents the results of a three year study of spring snowmelt runoff in watersheds of lake tahoe california usa using a network of nine nephelometric turbidometers we estimate that montane badlands comprising 1 2 of the ward creek watershed 25 km 2 contributed 10 39 of snowmelt derived suspended sediment load the badlands are comprised of poorly vegetated and deeply incised gullies formed in parent material of miocene volcanic mudflow breccia the larger 29 5 km 2 blackwood creek watershed also showed high relative erosion rates from volcanic terrain tributaries draining forested granitic and metasedimentary headwater regions had minimal sediment loads monitoring networks indicated that temporary main channel storage regulated release of fine sediment eroded from steep headwater slopes this lag between erosion and delivery may lead to underestimation of gully erosion contribution to sediment budgets

paleomagnetism and rock magnetism of early silurian dunn point volcanics avalon zone nova scotia abstract paleomagnetic results have been obtained from the subaerial volcanics andesites rhyolites ignimbrites from the dunn point formation exposed in the antigonish highlands of the avalon zone nova scotia an early silurian age of 430 15 ma is assigned to these volcanic rocks the age is in agreement with the fossil evidence from conformably overlying sedimentary rocks the volcanic units were tightly folded and metamorphosed to sub greenschist facies during one major and one secondary phase of deformation probably associated with the mid late devonian acadian orogeny this paleomagnetic study is based on 45 samples collected from nine sites the site mean directions of the natural remanent magnetization nrm make a large deviation from the present earth s field with nrm intensities ranging from 10 2 to 10 am 1 the most commonly observed remanence direction a d 153 i 28 obtained from both alternating fields 30 75 mt and thermal 500 560 c treatments yields a corresponding direction a d 0 i 63 after correction for geological tilt a large scatter in direction up to 60 is observed in a and the fold test is not significantly positive a second and less common remanence component b d 146 i 54 which presumably postdates folding is also observed this component is mainly isolated by thermal treatment in the 540 630 c range room temperature isothermal experiments and optical examination of polished sections indicate the presence of magnetite and hematite as the carriers of both a and b directions the corresponding reversed paleomagnetic poles fall at a 163 e 52 n and b 146 e 4 n in close agreement with cratonic north american upper jurassic and late devonian poles respectively in the mid late devonian time interval the avalon zone was situated slightly to the south but close to the north american eastern margin

gypsum scarps and asymmetric fluvial valleys in evaporitic terrains the role of river migration landslides karstification and lithology ebro river ne spain abstract most of the spanish fluvial systems excavated in tertiary evaporitic gypsum formations show asymmetric valleys characterized by a stepped sequence of fluvial terraces on one valley flank and kilometric long and 100 m high prominent river scarp on the opposite side of the valley scarp undermining by the continuous preferential lateral migration of the river channel toward the valley margin leads to vertical to overhanging unstable slopes affected by a large number of slope failures that become the main geological hazard for villages located at the toe of the scarps detailed mapping of the gypsum scarps along the ebro and huerva rivers gypsum scarps demonstrates that landslides and lateral spreading processes are predominant when claystones crop out at the base of the scarp while rockfalls and topples become the dominant movement in those reaches where the rock mass is mainly constituted by evaporites the dissolution of gypsum nodules seasonal swelling and shrinking and dispersion processes contribute to a decrease in the mechanical strength of claystones the existence of dissolution enlarged joints sinkholes and severely damaged buildings at the toe of the scarp from karstic subsidence demonstrates that the interstratal karstification of evaporites becomes a triggering factor in the instability of the rock mass the genesis of asymmetric valleys and river gypsum scarps in the study area seem to be caused by the random migration of the river channel in the absence of lateral tilting related to tectonics or dissolution induced subsidence once the scarp is developed its preservation depends on the physicochemical properties of the substratum the ratio between bedrock erosion and river incision rates and climatic conditions that favour runoff erosion versus dissolution

intra arc sedimentation and tectonism late paleozoic evolution of the eastern klamath terrane california rocks of the eastern klamath terrane redding section in northern california record deposition magmatism and tectonism in an island arc setting volcanism and sedimentation persisted for more than 220 m y spanning devonian to middle jurassic time and yielding thick successions of water laid volcanic debris and lavas with interstratified carbonate and clastic sequences this study focuses on the upper paleozoic rocks within the section the oldest rocks studied within the upper devonian and mississippian brag don formation contain epiclastic debris that was deposited in a submarine fan setting sandstone compositions indicate that quartzose sedimentary and metasedimentary rocks formed the source area for epiclastic debris and that volcanism persisted throughout sedimentation transitional shallow water facies in the upper part of the bragdon interfinger with the overlying baird formation which contains abundant volcanic debris volcanogenic shelf and strandline deposits characterize the lower part of the formation and volcaniclastic turbidites characterize the upper part the baird formation is locally interfingered with the overlying lower permian mccloud limestone which records two stages of early permian carbonate platform development early wolfcampian and late wolfcampian to early leonardian only the younger of the two platforms is present within the study area and it contains more distal facies than those preserved to the south the strata contain abundant fusulinids and corals which provide age constraints for carbonate platform development and form the basis for regional biogeographic correlation the time transgressive upper permian bollibokka group nosoni and dekkas formations succeeds the mccloud limestone comprising thick sequences of volcanogenic debris intercalated lava and in the upper part lenses of shallow water limestone the upper permian strata reflect volcanism and rapid subsidence within the are all upper paleozoic units were intruded by small gabbroic bodies and diabase dikes which may be partly cogenetic with upper permian basalts in the upper dekkas formation the upper paleozoic succession records local pulses of magmatism and variable subsidence rates within the eastern klamath arc mississippian epiclastic rocks reflect uplift of the volcanic arc basement which contained rocks similar to those now exposed in the adjacent yreka terrane or shoo fly complex pulses in volcanism were restricted to mid carboniferous and late permian time diminished volcanism during the early permian allowed development of carbonate platforms rapid fluctuations of sedimentation and sub sidence rates pronounced lateral facies and age variations accumulation of thick volcanic debris aprons during episodic volcanism and sporadic persistence of volcanism during apparent lulls characterized deposition within this succession and are common processes in modern volcanic arcs the stratigraphic record is composed predominantly of volcanogenic rocks and lesser carbonates reflecting events and processes within the arc itself evidence for nearby basins or landmasses is sparse the mississippian epiclastic rocks however which were derived from the arc basement reflect an ultimate sialic crustal source comparison of volcanic arc evolution with the late paleozoic evolution of continental margin and basinal rocks to the east indicates possible paleogeo graphic ties between the eastern klamath volcanic arc and rocks of the golconda allochthon or the north american continent

stratigraphic evolution of the paleozoic stikine assemblage in the stikine and iskut rivers area northwestern british columbia the stikine assemblage the basement of stikinia extends 500 km along the western flank of the intermontane belt east of younger coast belt plutons four different stratigraphic successions are characteristic of lower to middle devonian carboniferous and permian rocks in the stikine and iskut rivers area west of forrest kerr creek are penetratively deformed lower to middle devonian island arc volcaniclastic rocks coralline limestone and felsic tuff fringing carbonate buildups in an arc setting are best illustrated in the sequence at round lake where lower carboniferous mafic dominated bimodal submarine volcanic rocks grade upward into two distinctive coarse echinoderm limestone units and medial siliceous siltstone and limestone conglomerate conodont colour alteration indices for lower carboniferous rocks near newmont lake indicate an anomalously low temperature thermal history upper carboniferous permian polymictic volcanic conglomerate and lower permian limestone overlie these strata there t

circum iapetus paleogeography of the precambrian cambrian transition with a new paleomagnetic constraint from laurentia abstract the paleogeography of the precambrian cambrian transition is still poorly known but is fundamental for understanding late neoproterozoic climate extremes and the spatial associations of the rapidly evolving ediacaran and cambrian fauna this period has also been proposed to host unusual geodynamic events such as rapid plate motions and or the bulk tumbling of the earth with respect to its spin axis called true polar wander tpw new paleomagnetic and 40ar 39ar geochronologic results have been obtained from a pair of shallowly emplaced syenitic intrusions in western quebec the mont rigaud and the chatham grenville stocks are related to a failed rift arm of the iapetus ocean both intrusions bear hornblendes which provide overlapping 40ar 39ar plateau ages of 533 2 1 1 ma mont rigaud and 531 4 3 4 ma chatham grenville corresponding to early cambrian nemakit daldynian time characteristic paleomagnetic reversed directions from both intrusions are easterly and shallow d 89 3 i 30 1 95 6 2 k 38 8 n 15 sites and the mont rigaud intrusion also carries antipodal normal polarity directions the combined result yields a north paleopole at location 11 9 s 184 6 e dp 3 8 dm 6 9 placing the montreal region at 16 4 s paleolatitude in the early cambrian in good agreement with late ediacaran and middle to late cambrian paleomagnetic results from laurentia laurentia likely resided at low southerly paleolatitudes throughout the cambrian ruling out a major inertial interchange tpw event for early to middle cambrian time a comparison of late ediacaran to middle cambrian paleomagnetic results from laurentia baltica siberia and elements of west gondwana implies that by early cambrian time a large paleolatitudinal gap existed between laurentia and its presumed conjugate rift margins thus placing a wide iapetus ocean between them the position of baltica within the circum iapetus paleogeography is contentious due to differing interpretations of the few paleomagnetic results during ediacaran time laurentia underwent large apparent polar wander that is manifested as motion from low latitude at 615 ma to the south polar region at 590 575 ma and then rapidly back to low latitude by 565 550 ma the large and perhaps rapid apparent polar wander of laurentia and other continents in the ediacaran remains enigmatic and controversial

structure and porosity of smectitic mudrocks as affected by experimental wetting drying cycles and freezing thawing cycles abstract the erosion rates in the vallcebre basin pyrenees are controlled predominantly by the physical weathering rate of bare regolith i e mudrocks to obtain information on the influence of thermic and moisture regimes on the weathering dynamics laboratory experiments were carried out to investigate how freezing thawing or wetting drying cycles under controlled conditions affect structure and porosity three different clayey mudrocks were selected to represent materials more susceptible to erosion in the studied area the three lithologies identified as ca1r ca2r carr differed mainly in mineral constituents type and quantity of the clay minerals and cation exchange capacity an automated non contact laser profile meter was used to analyse surface microtopography in order to monitor random roughness variations and to calculate bulk density porosity and pore size distribution were carried out with image analysis freezing thawing cycles were the most active in modifying soil surface and bulk structure roughness of ca1r and ca2r was more than doubled at the end of freezing thawing cycles this variation was mostly associated with the whole surface elevation related to the bulk volume increase roughness variations in carr were less pronounced and related to a modification of the microtopography micromorphological observations revealed a platy structure formation induced by repeated ice lensing also porosity was increased by freezing thawing cycles with the formation of a large number of irregular and rounded pores wetting drying cycles did not affect surface roughness and modified bulk density very little in all samples they increased porosity by the formation of large cracks and fissures overall data from wetting drying cycles showed that changes in water content alone did not produce deep structural modifications a mechanism of alteration of soil structure during freezing thawing cycles is proposed

flood based analysis of high magnitude sediment transport using a non parametric method francke t lopez tarazon j a vericat d bronstert a batalla r j 2008 flood based analysis of high magnitude sediment transport using a non parametric method earth surface processes and landforms 33 13 2064 2077 sponsorship sesam catalan government european social fund

short and long term studies of sediment dynamics in a small humid mountain mediterranean basin with badlands abstract badland landscapes are the main sediment sources in the vallcebre area eastern pyrenees catalonia spain short term studies up to 3 years long carried out between 1980 and 1994 were used to estimate the rates of both denudation on bare surfaces and sediment production at the plot scale to analyse the seasonal dynamics of bedrock weathering and regolith behaviour and to study the relationships between geomorphic activity and herbaceous plant colonisation since 1990 stream flow and suspended sediment loads have been monitored using three gauging stations equipped with infrared backscattering turbidimeters ultra sonic beam attenuation solids sensors and automatic water samplers the combination of the two different approaches has been useful for a better perception of the dynamics of the badland systems and to assess the long term contribution of these areas to the basin sediment loads badland erosion at the event scale for a period of 15 years was simulated with the kineros2 model and allowed the long term comparison between badland erosion and sediment yield at the small basin scale badlands are the main source of sediment in the basin for most of the events but infrequent runoff events cause the removal of sediment stores and the activation of other sediment sources the analysis of the uncertainty of sediment yield measurements for a range of record durations demonstrated that long records are needed for obtaining acceptable results due to the high interannual variability relatively low cost short term geomorphic observations may provide information useful for assessing the long term sediment production in these basins with badland areas only if the observations are used to implement a model able to simulate long term observations

palaeomagnetic study of the late precambrian west greenland kimberlite lamprophyre suite definition of the hadrynian track abstract kimberlite and potassic lamprophyre dykes were intensively intruded into the early proterozoic nagssugtoqidian mobile belt of west greenland during an important phase of brittle reactivation in late precambrian early cambrian times ca 580 570 ma and during at least one other minor phase thermal and alternating field demagnetisation studies of 52 of these dykes identify primary components residing in the critical blocking temperature range distributed between shallow westerly and steep positive directions near the axis of the proterozoic shear belt the dykes predominantly lamprophyres have closely grouped shallow directions with a reversal near the margins of the shear belt dykes predominantly kimberlites have steeper and distributed directions the cleaned components of magnetisation appear to be single and the distribution of directions is interpreted to record a migration of the palaeofield axis which intersecting relationships show to have been from shallow to steep the dyke directions are grouped to define representative mean palaeopoles of 215 e 3 n lk1 a 95 3 9 213 e 18 n lk2 a 95 6 1 203 e 46 n lk3 a 95 10 4 and 259 e 54 n lk4 a 95 11 0 a subsidiary direction recorded in five dykes near the southern margin of the shear belt lk5 palaeopole at 297 e 16 s a 95 12 5 is derived entirely from lamprophyres and is possibly silurian in age an rb sr isochron on three lamprophyres of 1227 ma and agreement of the remanence direction with ca 1220 ma rocks from elsewhere in greenland suggests that the lk1 component is wholly or partly of that age the remaining sequence of palaeopoles falls along the hadrynian polar track and the age data relating to this track are re evaluated evidence for a pre 800 ma age is no longer valid and the new data from west greenland confirm that the track is latest precambrian to early cambrian in age it is shown to connect poles of late precambrian and lower cambrian age and to embrace other data from the laurentian shield the rapid passage of the shield across the south pole is consistent with the sedimentation sequences and suggests a high latitude origin for the tillite horizon of this age the hadrynian track is also compared with the contemporaneous record from gondwanaland and it is shown that the two shields were in juxtaposition in the identical reconstruction to the proterozoic supercontinent until earliest cambrian times this discovery links the lower cambrian marine transgression and the widespread ca 580 560 ma alkaline province in the gondwanaland laurentian and fennoscandian shields to major continental break up and it conforms with evidence that the iapetus ocean did not open until cambrian times