low long term erosion rates in high energy mountain belts insights from thermo and biochronology in the eastern pyrenees abstract we relate the high elevation of flat topography in the eastern pyrenees to the resurrection of a mountain belt which prior to 12 ma was a low relief landscape or peneplain bevelling eroded stumps of the pyrenean compressional orogen new apatite fission track and u th he data together demonstrate the consistently young age

far field effects of alpine plate tectonism in the iberian microplate recorded by fault related denudation in the spanish central system abstract apatite fission track analysis was performed on 56 samples from central spain to unravel the far field effects of the alpine plate tectonic history of iberia the modelled thermal histories reveal complex cooling in the cenozoic indicative of intermittent denudation accelerated cooling events occurred across the spanish central system scs from the middle eocene to recent these accelerated cooling events resulted in up to 2 8 0 9 km of denudation in the western sierra de gredos and 3 6 1 0 km in the central and eastern gredos assuming a paleogeothermal gradient of 28 5 c and a surface temperature of 10 c the greatest amount of denudation 5 0 1 6 km occurred in the sierra de guadarrama accompanying rock uplift was 4 7 1 0 and 5 9 1 6 km in the eastern gredos and guadarrama respectively most denudation in the gredos occurred from the middle eocene to the early miocene and can be related to the n s stress field induced by the pyrenean compression in the guadarrama the greatest denudation was pliocene to recent of age and seems related to the ongoing nw se betic compression the fact that the formation of the e w trending gredos coincides with the n s pyrenean compression and the creation of the present day morphology of the ne sw trending guadarrama with the younger nw se betic compression indicates that they record the far field effects of alpine plate tectonics on iberia the trend of pre existing lineaments was of major importance in influencing the style and magnitude of these of far field effects

geology mineralogy and human welfare the complex sciences of geology and mineralogy couple the focused sciences of physics chemistry and biology to the diffuse disciplines of ecology and the environment for this colloquium 18 papers have been selected on matters related to human welfare particularly health and both physical and mental wellbeing to demonstrate the importance of new research plans and new instrumentation emerging chemical microscopes using neutrons synchrotron x rays and electrons allow physicochemical characterization of mineral surfaces and adsorbed molecules and ions in soils 1 plant growth depends on subtle interactions between mineral surfaces saline fluids and microbes incorporation of good trace elements into food depends on the interaction of organic and inorganic components as does that of toxic ones one quarter of the wheat and rice crops are lost to mn oxidizing bacteria soils become contaminated with mobile toxic elements including pb cd se and as which can affect plant growth and food safety 2 4 mineral dust blown from drying geological basins pervades the atmosphere and falls to earth with both good results loess soil in central europe china and north america was important for early agriculture and still supports large populations and bad ones air pollution causes lung problems 5 chemical microscopes provide physicochemical analysis of tiny particles particularly useful for distinguishing the natural and industrial components 6

pulsating subsidence during a rift episode stratigraphic and tectonic consequences aptian albian northern spain backstripping analysis has been carried out on nine outcrop sections of the basque cantabrian aptian and albian of northern spain which consist of shallow water marine deposits up to 7000 m thick it reveals four main pulses of common accelerated subsidence i early aptian ii early albian iii lower late albian and iv uppermost late albian separated by tectonic quiescent intervals tectonic subsidence rates of 70 m myr 1 for the aptian and 101 m myr 1 for the albian were recorded sopuerta section the calculated stretching factor referred to a pre rift continental crust of 35 km is bs 1 32 and represents approximately 8 5 km of crustal thinning points of change towards lesser subsidence rate in the curves are correlated with major unconformities in the sections in the basque cantabrian basin and in boreal europe suggesting geodynamic changes related with the opening of bay of biscay minor variations of spreading direction and intensity are proposed to explain the subsidence pulses

an example of intraplate neotectonic activity vilarica basin northeast portugal the vilarica tectonic basin nw iberian peninsula is presented as an example of intraplate neotectonic activity the regional geological setting is first introduced then followed by a brief view on the neotectonic activity in portugal the basin consists of an elongated depression approximately 20 km long and 2 to 3 km wide trending nne ssw it is located astride a late variscan strike slip fault the manteigas braganca fault suggesting that it might correspond to a structural depression related to reactivation movements on that fault mapping of neogene and quaternary cover deposits preserved in the basin and its vicinity was accomplished and numerous evidence of tectonic deformation tilting and faulting affecting the sediments were found other geomorphological criteria are discussed showing the structural origin of the vilarica basin and its neotectonic activity attending to its location on the manteigas braganca fault the vilarica depression is interpreted as a pull apart basin resulting from left lateral strike slip displacement on that fault in the quaternary average fault slip rates are estimated with values comprised between 0 2 mm yr and 0 5 mm yr these slip rates are typical of moderate to moderately high degrees of fault activity and are compatible with the regional faulting geomorphic expression and the relatively important historical and instrumental seismicity affecting the vilarica region finally a geodynamical model is proposed and the studied area is presented in the geodynamic framework

post alleghanian unroofing history of the appalachian basin pennsylvania from apatite fission track analysis and thermal models results of apatite fission track analyses on 29 ordovician through permian sandstones from the appalachian basin in pennsylvania are presented ages range from 111 17 to 184 10 ma mean track lengths of 10 71 0 29 to 13 10 0 17 m with unimodal negatively skewed length distributions are indicative of slow cooling the data separate into two groups on an age versus mean length plot the younger group 111 144 ma is found in the structural depressions of the anthracite basin and the broad top basin and adjacent appalachian plateau the older group 144 184 ma is found in the structurally higher southwestern appalachian plateau and juniata culmination and adjacent central plateau fission track data suggest that the basin cooled slowly after the alleghanian orogeny with culminations cooling earlier than depressions cooling histories modeled from apatite fission track data with maximum temperatures constrained by vitrinite reflectance indicate cooling beginning soon after the alleghanian orogeny except in the juniata culmination which apparently experienced synorogenic cooling and unroofing during formation of the underlying duplex model cooling histories and available geologic information indicate that the foreland basin did not experience mesozoic reheating unroofing histories were modeled from fission track cooling histories using heat flow estimates and burial depths derived from vitrinite reflectance profiles the models suggest that the unroofing history of the appalachian basin in pennsylvania can be divided into three episodes an initial episode of relatively rapid cooling and unroofing late permian early jurassic is attributed to flexural rebound of the foreland in response to erosional removal of alleghanian topographic load initial unroofing rates are higher in eastern pennsylvania than in the west consistent with a flexural model an episode of little to no unroofing middle jurassic late oligocene began contemporaneously with the inception of drift at the atlantic continental margin at this time unloading of the orogen was replaced by subsidence and sedimentation on the new margin without flexural rebound the driving force for unroofing of the basin was removed and unroofing slowed greatly an episode of rapid unroofing over the full width of the basin occurred from the miocene to the present although the driving mechanism for unroofing at this time has not been identified it is consistent with increased sedimentation rates in the middle atlantic offshore basins for the same period

illite and hydrocarbon exploration illite is a general term for the dioctahedral mica like clay mineral common in sedimentary rocks especially shales illite is of interest to the petroleum industry because it can provide a k ar isotope date that constrains the timing of basin heating events it is critical to establish that hydrocarbon formation and migration occurred after the formation of the trap anticline etc that is to hold the oil illite also may precipitate in the pores of sandstone reservoirs impeding fluid flow illite in shales is a mixture of detrital mica and its weathering products with diagenetic illite formed by reaction with pore fluids during burial k ar ages are apparent ages of mixtures of detrital and diagenetic end members and what we need are the ages of the end members themselves this paper describes a methodology based on mineralogy and crystallography for interpreting the k ar ages from illites in sedimentary rocks and for estimating the ages of the end members

time scales of tectonic landscapes and their sediment routing systems abstract in regions undergoing active tectonics the coupling between the tectonic displacement field the overlying landscape and the redistribution of mass at the earth9s surface in the form of sediment routing systems is particularly marked and variable coupling between deformation and surface processes takes place at a range of scales from the whole orogen to individual extensional fault blocks or contractional anticlines at the large scale the attainment of a steady state between the overlying topography and the prevailing tectonic conditions in active contractional orogens requires an efficient erosional system with a time scale dependent on the vigour of the erosional system generally in the range 10 6 10 7 years the catchment fan systems associated with extensional fault blocks and basins of the western usa are valuable natural examples to study the coupling between tectonic deformation landscape and sediment routing systems even relatively simple coupled systems such as an extensional fault block and its associated basin margin fans have a range of time scales in response to a tectonic perturbation these response times originate from the development of uniform steady state relief during the accumulation of displacement on a normal fault c 10 6 years the upstream propagation of a bedrock knickpoint in transverse catchments following a change in tectonic uplift rate c 10 6 years or the relaxation times of the integrated catchment fan system in response to changes in climatic and tectonic boundary conditions 10 5 10 6 years the presence of extensive bedrock or alluvial piedmonts increases response times significantly the sediment efflux of a mountain catchment is a boundary condition for far field fluvial transport but the fluvial system is much more than a simple transmitter of the sediment supply signal to a neighbouring depocentre fluvial systems appear to act as buffers to incoming sediment supply signals with a diffusive time scale c 10 5 10 6 years dependent on the length of the system and the extent of its floodplains stream channels and proximal gravel fans the vocabulary for explaining landscapes would benefit from a greater recognition of the importance of the repeat time and magnitude of perturbations in relation to the response and relaxation times of the landscape and its sediment routing systems landscapes are best differentiated as buffered or reactive depending on the ratio of the response time to the repeat time of the perturbation furthermore landscapes may be regarded as steady or transient depending on the ratio of the response time to the time elapsed since the most recent change in boundary conditions the response of tectonically and climatically perturbed landscapes has profound implications for the interpretation of stratigraphic architecture

crustal thickening and deformation sequence in the footwall to the suture of the variscan belt of northwest spain abstract the sequence of formation and propagation of structures as well as the evolution of crustal thickening in the variscan belt of northwest spain are proposed in this paper the foreland of this mountain belt shows thin skinned tectonics a polyphase deformation with associated regional metamorphism is recognized in the hinterland zones two important culminations the narcea and lugo antiforms are present in an e w cross section through the footwall to the suture of this orogen such culminations are derived from the stacking of several thrust systems generated during two successive periods the sequence of thrust emplacement helps to clarify the formation of different types of structures at the same time in different places in the orogen

overview of naturally occurring earth materials and human health concerns abstract the biosphere and the earth s critical zone have maintained a dynamic equilibrium for more than 3 5 billion years except for solar energy almost all terrestrial substances necessary for life have been derived from near surface portions of the land hydrosphere and atmosphere if aggregate biological activities are less than the rate of nutrient supply and or resource renewal sustained population growth is possible where the replenishment rate of a life sustaining earth material is finite usage may reach a condition of dynamic equilibrium in which biological consumption equals but on average cannot exceed the overall supply although large most natural resources are present in finite abundances for such commodities excessive present day human utilization reduces future availability and thus the ultimate planetary carrying capacity for civilization intensive use of earth materials has enhanced the quality of life especially in the developed nations still natural background levels and earth processes such as volcanic eruptions as well as human activities involving agriculture construction and the extraction refining and transformation of mineral resources have led to harmful side effects involving environmental degradation and public health hazards among naturally and anthropogenically induced risks are bioaccessible airborne dusts and gases soluble pollutants in agricultural industrial and residential waters and toxic chemical species in foods and manufactured products at appropriate levels of ingestion many earth materials are necessary for existence but underdoses and overdoses have mild to serious consequences for human health and longevity this overview briefly sketches several natural resource health hazards included are volcanic ash aerosols gases mineral dusts non volcanic aerosols nanoparticles asbestos fibrous zeolites arsenic fluorine iodine uranium thorium radium radon polonium selenium mercury copper lead chromium and cadmium also noted are health effects of natural disasters and an obligatory future sustainable consumption of natural resources not treated are the overwhelming adverse effects of malnutrition lack of potable water inadequate sanitation fossil fuel usage mining manufacturing and agricultural pollution or environmental pathogens nor are the important impacts of complex mixtures of earth materials considered with rise of the worldwide information network economic globalization and the industrial thrust of developing nations the achievement of natural resource sustainability has emerged as a strategic imperative accompanying increased rates of earth materials consumption and attendant environmental change substantially improved universal public health will require a major global effort integrating collaborations among geoscientists medical researchers and epidemiologists governments and ngos must provide important support of such cooperative efforts and both health and earth scientists must cross disciplinary and national boundaries

the relationship between track shortening and fission track age reduction in apatite combined influences of inherent instability annealing anisotropy length bias and system calibration abstract the relationship between reduced track density 0 and reduced mean confined track length l l 0 during annealing has been studied for both spontaneous and induced tracks in four apatite samples with different chemical composition compositional range and origin and with spontaneous tracks giving mean confined track lengths varying from 14 5 m down to 12 3 m in all four apatites induced tracks show a relationship between l l 0 and 0 composed of two regions at higher values the two appear to be equal while at lower values l l 0 is greater than 0 this can be understood qualitatively in terms of the anisotropy of annealing and the bias against revelation of short tracks data from three apatites of uniform composition show near identical relationships in a sample showing a range of apatite compositions the point of divergence from the 1 1 relationship is somewhat higher than in the uniform composition apatites because individual grains anneal at different rates and the presence of highly annealed grains affects the track density more strongly than the mean track length spontaneous tracks show similar relationships to those observed for induced tracks in each sample when the data are renormalised to allow for the natural annealing present in the spontaneous tracks previous studies which led to the idea of length reduction without density reduction for spontaneous tracks did not renormalise density data as well as length data thereby distorting the apparent relationship data for the multi compositional apatite sample where annealing has taken place in geological conditions also agrees with the laboratory annealing data for both spontaneous and induced tracks this consistency suggests that a single process is responsible in all three cases implying that a laboratory based description of annealing can be applied to geological conditions with confidence recognition that spontaneous tracks in apatite are commonly annealed suggests that in general the fission track age should be interpreted as a reflection of both the time over which tracks have been retained and the distribution of etchable track lengths since the latter is a manifestation of the thermal history the fission track age should be interpreted in similar terms

seismic image of the cantabrian mountains in the western extension of the pyrenees from integrated escin reflection and refraction data abstract integrated analysis of normal incidence and large aperture seismic reflection data collected in 1992 and 1993 within the spanish escin and complementary projects provide a first complete n s crustal transect across the northern iberian peninsula and continental margin images of the crustal structure of the cantabrian mountains and their transition to the duero basin and to the cantabrian margin are obtained from a a 65 km long vertical reflection profile escin 2 on land b a 200 km long reversed refraction profile and c wide angle recordings of the marine escin 4 profile consistent results between reflectivity pattern and velocity depth distribution reveal important lateral variations in the deep structure the reflective crust imaged in the escin 2 profile changes its attitude from sub horizontal beneath the duero basin to north dipping beyond the mountain front basement thrusts are observed in the upper crust merging into a detachment at 6 s twt and may have triggered the alpine uplift of the range the moho is identified at the bottom of the reflective lower crust and deepens from 12 to 15 s at the northern end of the profile about 35 km inland modelling of the refraction data laterally extends the seismic image and provides evidence for variscan crustal features beneath the duero basin northwards the velocity in the lower crust decreases and the moho constrained by the wide angle data from profile escin 2 deepens to about 60 km ending abruptly at the shoreline the velocity depth model is constrained along the asturian platform up to the continental slope where the crust mantle boundary is located at 24 km depth this margin moho shows a progressive deepening southwards and extends to the coast where it is found at 30 km depth the present seismic data support an important alpine reworking and thickening of the crust under the cantabrian mountains the onshore offshore transition is marked by an imbrication of two crusts of very different thicknesses this signature offers a strong parallelism with the one previously observed further east across the pyrenees in the ecors seismic profile

growth and propagation of buckle folds determined from syntectonic sediments the ubierna fold belt cantabrian mountains n spain abstract the geometry of syntectonic tertiary sediments in the ubierna fold belt can be explained using the buckling folding theory the geometric features of the fold train in the pre orogenic succession also agree with a buckling process each fold grew with progressive and coeval rotation of both limbs although rotation was asymmetric and greater on the forelimb than the backlimb the diachroneity of synrotational sequences progressive unconformities through different folds indicates that fold propagation migrated towards the foreland however the initial folds were tightened during a later deformation stage synchronous with the development of younger folds

western extension of the iberian european plate boundary during the early cenozoic pyrenean convergence a new model abstract a dense seismic net work allows of drawing the western prolongation of the northern boundary of the iberian plate this early cenozoic deformed boundary is disrupted by two prominent nw se transform faults a kinematic reconstruction with a nw late cretaceous lower eocene motion of the iberian plate is proposed the azores biscay rise is interpreted as a short lived subduction zone whereas king s trough could be a transform fault

seismicity analysis at the prestige oil tanker wreck area galicia margin nw of iberia an evaluation of the geological hazard related to the sinking of the prestige oil tanker in november 2002 in the galicia margin nw of iberia was supported by the spanish research agency it included a specific seismic study of the local activity and of the regional seismicity in this margin results of which are presented here published global catalogues show that diffuse seismicity of moderate magnitude events up to 5 6 mb can be associated with the northern flank of the galicia margin with a roughly e w distribution however event locations in this area are poorly constrained due to the inappropriate geometry of permanent seismic networks we collected and analyzed new data from a dense deployment of 10 obs around the wreck site and from a network of 12 land stations at the nw corner of iberia during a 7 months operation period the land network permitted location of 120 events with magnitudes ranging from 1 6 to 4 8 more than 30 of which were not reported by the spanish permanent array confirming the existence of a moderate seismicity in this area five new focal solutions have been obtained for events on land providing additional information about the active faults in the region the obs network ran for 1 month and allowed the location of three earthquakes of magnitude 2 5 near the sinking site four more events have been identified with just a rough determination of their epicenters based on polarization of the p wave arrivals besides these earthquakes the obs data recorded numerous seismic events of different types they include i groups of very short and regularly spaced pulses that can be explained as acoustic calls generated by finback whales ii a large number of short duration seismic events 2 3 s long identified only at individual obs iii local intense monochromatic signals lasting for up to 4 h that can be described as harmonic tremors these last two types of seismic events might be related to hydrothermal activity within the uppermost sediments and deserve additional studies to appropriately establish the seismic hazard of this area 2007 elsevier b v all rights reserved

low temperature exhumation history of variscan age rocks in the western cantabrian mountains nw spain recorded by apatite fission track data abstract this paper presents the first regional study of apatite fission track aft thermochronology to be undertaken in the western termination of the cantabrian mountains nw spain the mountains reach elevations of over 2600 m along the northern coast of spain and are comprised of a variscan crustal section uplifted due to cenozoic shortening along the northern iberian plate the study constrains the pattern and history of exhumation within the paleozoic bedrock over the past c 240 ma twenty one apatite fission track samples range in age from 246 7 26 9 ma to 78 1 3 7 ma with mean track lengths between 10 4 1 8 m and 12 4 1 4 m time temperature path modelling of the data indicates that different rates of continuous cooling took place during the three main tectonic events that affected the area a rapid cooling event that ended by the late jurassic corresponds to topographic decay during unroofing of the variscan orogen and the break up of pangea and is responsible for the largest amount of exhumation westernmost samples cooled coinciding with rifting in the north atlantic and bay of biscay during the late jurassic to early cretaceous by about 100 80 ma most samples had reached or passed through the upper boundary of the apatite partial annealing zone which indicate that regional denudation has not exceeded c 1 7 km since then for geothermal gradients 27 c km and a surface temperature of 15 c only three samples next to fault escarpments in the west cooled below 70 c since 80 ma reaching below 65 c before initiation of incipient subduction along the northern iberian margin by 46 ma an average cooling rate of 1 c ma reflects latest denudation as the new mountainous relief developed since then due to shortening and incipient subduction associated with convergence along the northern iberian plate the cantabrian mountains are one of the few natural examples of a coastal orogen in a juvenile stage of evolution

aspects of the structural evolution of the lusitanian basin in portugal and the shelf and slope area offshore portugal abstract the study provides a regional seismic interpretation and mapping of the mesozoic and cenozoic succession of the lusitanian basin and the shelf and slope area off portugal the seismic study is compared with previous studies of the lusitanian basin from the late triassic to the cretaceous the study area experienced four rift phases and intermittent periods of tectonic quiescence the triassic rifting was concentrated in the central part of the lusitanian basin and in the southernmost part of the study area both as symmetrical grabens and half grabens the evolution of half grabens was particularly prominent in the south the triassic fault controlled subsidence ceased during the latest late triassic and was succeeded by regional subsidence during the early early jurassic hettangian when deposition of evaporites took place a second rift phase was initiated in the early jurassic most likely during the sinemurian pliensbachian this resulted in minor salt movements along the most prominent faults the second phase was concentrated to the area south of the nazare fault zone and resulted here in the accumulation of a thick sinemurian callovian succession following a major hiatus probably as a result of the opening of the central atlantic resumed deposition occurred during the late jurassic evidence for late jurassic fault controlled subsidence is widespread over the whole basin the pattern of late jurassic subsidence appears to change across the nazare fault zone north of the nazare fault fault controlled subsidence occurred mainly along nnw sse trending faults and to the south of this fault zone a nne ssw fault pattern seems to dominate the oxfordian rift phase is testified in onlapping of the oxfordian succession on salt pillows which formed in association with fault activity the fourth and final rift phase was in the latest late jurassic or earliest early cretaceous the jurassic extensional tectonism resulted in triggering of salt movement and the development of salt structures along fault zones however only salt pillow development can be demonstrated the extensional tectonics ceased during the early cretaceous during most of the cretaceous regional subsidence occurred resulting in the deposition of a uniform lower and upper cretaceous succession marked inversion of former normal faults particularly along ne sw trending faults and development of salt diapirs occurred during the middle miocene probably followed by tectonic pulses during the late miocene to present the inversion was most prominent in the central and southern parts of the study area in between these two areas affected by structural inversion fault controlled subsidence resulted in the formation of the cenozoic lower tagus basin northwest of the nazare fault zone the effect of the compressional tectonic regime quickly dies out and extensional tectonic environment seems to have prevailed the miocene compressional stress was mainly oriented nw se shifting to more n s in the southern part

reproducibility of apatite fission track length data and thermal history reconstruction abstract the ability to derive detailed thermal history information from apatite fission track analysis is predicated on the reliability of track length measurements however insufficient attention has been given to whether and how these measurements should be standardized in conjunction with a fission track workshop we conducted an experiment in which 11 volunteers measured 50 track lengths on one or two samples one mount contained durango apatite with unannealed induced tracks and one contained apatite from a crystalline rock containing spontaneous tracks with a broad length distribution caused by partial resetting results for both mounts showed scatter indicative of differences in measurement technique among the individual analysts the effects of this variability on thermal history inversion were tested using the hefty computer program to model the spontaneous track measurements a cooling only scenario and a reheating scenario more consistent with the sample s geological history were posed when a uniform initial length value from the literature was used results among analysts were very inconsistent in both scenarios although normalizing for track angle by projecting all lengths to a c axis parallel crystallographic orientation improved some aspects of congruency when the induced track measurement was used as the basis for thermal history inversion congruency among analysts and agreement with inversions based on data previously collected was significantly improved further improvement was obtained by using c axis projection differences among inversions that persisted could be traced to differential sampling of long and short track populations among analysts the results of this study while demonstrating the robustness of apatite fission track thermal history inversion nevertheless point to the necessity for a standardized length calibration schema that accounts for analyst variation

weathering mantles and their significance for geomorphological evolution of central and northern europe since the mesozoic abstract weathering mantles saprolites are very widespread in central western and northern europe where they form thick near surface residual deposits often in excess of 50 m they vary in the type of weathering the bedrock lithology involved the topographic setting and the age and stratigraphic context this review paper provides information about the distribution and major characteristics of weathering mantles from a number of key areas including the british isles the central european belt of mid mountains and uplands the scandinavian mountains and the fennoscandian shield it also examines the evidence for weathering etched origin of various landforms including boulders tors inselbergs basins and some regional landforms assemblages major types of regionally important weathering mantles include ferrallitic lateritic saprolites kaolinite rich saprolites sandy to grus mantles and various residuals left after partial dissolution of carbonate rocks although dating of weathering mantles is often circumstantial it appears sufficiently precise to argue for various ages of deep weathering mesozoic pre late cretaceous mantles are particularly widespread but there are also early tertiary and miocene saprolites widely present whilst most grus weathering is likely to be of miocene to pleistocene age individual upland areas have been subjected to multiple episodes of weathering whose legacy is the present day co existence of different weathering products continental and shallow marine deposits around the uplands particularly in the north sea and intra continental graben structures are often dominated by quartz and kaolinite pointing to deeply weathered land surfaces as the source areas and extending the record of weathering on the geological time scale they demonstrate that weathering mantles repeatedly formed and were subjected to erosion and new cycles of weathering were initiated we suggest that deep unroofing of basement structures in many parts of europe has been mainly accomplished by deep weathering and stripping of pre weathered rock the phenomenon of deep weathering has been very important for geomorphology etched landforms vary in size from small residual boulders up to regional characteristic landscapes etchsurfaces such as joint valley landscapes of southern sweden or undulating multi convex and multi concave landscapes of many uplands in central europe deep weathering has played a major part in the geomorphological evolution of europe since at least the late triassic and the concept involving long term etching and stripping provides an appropriate framework to describe and explain both erosional landscapes and sediment features

a regional soil and sediment geochemical study in northern california abstract regional scale variations in soil geochemistry were investigated in a 20 000 km 2 study area in northern california that includes the western slope of the sierra nevada the southern sacramento valley and the northern coast ranges over 1300 archival soil samples collected from the late 1970s to 1980 in el dorado placer sutter sacramento yolo and solano counties were analyzed for 42 elements by inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry following a near total dissolution these data were supplemented by analysis of more than 500 stream sediment samples from higher elevations in the sierra nevada from the same study site the relatively high density data 1 sample per 15 km 2 for much of the study area allows the delineation of regional geochemical patterns and the identification of processes that produced these patterns the geochemical results segregate broadly into distinct element groupings whose distribution reflects the interplay of geologic hydrologic geomorphic and anthropogenic factors one such group includes elements associated with mafic and ultramafic rocks including cr ni v co cu and mg using cr as an example elevated concentrations occur in soils overlying ultramafic rocks in the foothills of the sierra nevada median cr 160 mg kg as well as in the northern coast ranges low concentrations of these elements occur in soils located further upslope in the sierra nevada overlying tertiary volcanic metasedimentary and plutonic rocks granodiorite and diorite eastern sacramento valley soil samples defined as those located east of the sacramento river are lower in cr median cr 84 mg kg and are systematically lower in this suite compared to soils from the west side of the sacramento valley median cr 130 mg kg a second group of elements showing a coherent pattern including ca k sr and ree is derived from relatively silicic rocks types this group occurs at elevated concentrations in soils overlying volcanic and plutonic rocks at higher elevations in the sierras e g median la 28 mg kg and the east side of the sacramento valley median 20 mg kg compared to soils overlying ultramafic rocks in the sierra nevada foothills median 15 mg kg and the western sacramento valley median 14 mg kg the segregation of soil geochemistry into distinctive groupings across the sacramento river arises from the former presence of a natural levee now replaced by an artificial one along the banks of the river this levee has been a barrier to sediment transport sediment transport to the valley by glacial outwash from higher elevations in the sierra nevada and more recently debris from placer au mining has dominated sediment transport to the eastern valley high content of mafic elements and low content of silicic elements in surface soil in the west side of the valley is due to a combination of lack of silicic source rocks transport of ultramafic rock material from the coast ranges and input of sediment from the late mesozoic great valley group which is itself enriched in mafic elements a third group of elements zn cd as and cu reflect the impact of mining activity soil with elevated content of these elements occurs along the sacramento river in both levee and adjacent flood basin settings it is interpreted that transport of sediment down the sacramento river from massive sulfide mines in the klamath mountains to the north has caused this pattern the pb and to some extent zn distribution patterns are strongly impacted by anthropogenic inputs elevated pb content is localized in major cites and along major highways due to inputs from leaded gasoline zinc has a similar distribution pattern but the source is tire wear

seismic signature of variscan and alpine tectonics in nw iberia crustal structure of the cantabrian mountains and duero basin the seismic structure of the crust of the nw iberian peninsula along the cantabrian mountains and their southern foreland the duero basin is investigated from the first data set available from refraction and wide angle reflection profiles the velocity depth distributions obtained along e w and n s transects evidence lateral variations in crustal structure that can be associated to variscan and alpine tectonic episodes the western part of the range toward the variscan hinterland zones as well as the duero basin below the sediments show a crustal structure similar to that of the variscan belt elsewere in europe the total crustal thickness is 30 32 km and three main layers upper middle and lower crust with average velocities 6 0 6 25 and 6 8 km s are resolved some paleozoic structures such as the basal detachment of the cantabrian zone are expressed in the seismic models the crust appears to vary eastward in the external zones the most outstanding feature is a crustal root beneath the highest cantabrian summits where the moho is found at 47 km depth a prominent alpine reworking of the crust in the eastern part of the cantabrian zone is thus revealed and the n s seismic transects delineate a geometry similar to the one found across the central pyrenees in the etude continentale et oceanique par reflexion et refraction sismique ecors profile revealing the importance of the alpine deformations in the northern part of the iberian plate

seismic evidence of alpine crustal thickening and wedging from the western pyrenees to the cantabrian mountains north iberia 1 the alpine collision between the iberian and european plates resulted in a complex crustal structure beneath the northern iberian peninsula as revealed from a new set of seismic refraction wide angle reflection profiles the study area is characterized by two major e w ranges the cantabrian mountains and the pyrenees which are relayed to the south by the iberian chain important variations in crustal thickness and velocity distribution are found in a 560 km long e w transect in contrast to the typical 30 to 32 km thick european variscan crust of the western end of the profile a continuous alpine crustal root is evidenced from the cantabrian mountains to the central pyrenees with a moho depth of 46 48 km locally rising to 40 km depth in between beneath the basque cantabrian basin another outstanding feature is the inferred presence of high velocities of 6 40 6 75 km s at midcrustal depths which can be associated with portions of a lower crustal wedge from the northern european domain indenting the southern iberian crust during the alpine stage of compression this indentation produces the delamination of the iberian crust with northward underthrusting of its lower half and the consequent crustal thickening the indenting wedge has a discontinuous presence along the longitudinal section as it was controlled and or affected by n s to ne sw structures further evidence of the northward subduction of the iberian plate is provided by another profile toward the aquitaine basin while a n s profile across the iberian chain reveals an alpine midcrustal thickening beneath this belt with moho depths of 42 km

a users guide to fission track dating calibration abstract misconceptions regarding the fission track dating method prompt the description of five handling procedures and the derivation of commonly used system calibrations problems of registration geometry inhomogeneous uranium distribution accumulated radiation damage and anisotropic etching largely invalidate all but the population and external detector methods and impose strict limitations upon even their routine application complexities of unique absolute thermal neutron dosimetry are illustrated by the calibration and use of the nbs pre irradiated glass srm 962 the 20 disparity in measured f decay constant values cannot be isolated from neutron fluence measurement and calibration frequently a calibration ratio f is evaluated against an age standard and then split into its component parts to illustrate this interdependence of f and zircon fission track ages in agreement with independent k ar ages are obtained by calculating the same track count data with each of the preferred values of f f 7 03 10 17 yr 1 and8 46 10 17 yr 1 together with appropriate selected neutron dosimetry schemes an alternative approach is presented formally relating unknown ages of samples to known ages of standards either by direct comparison of standard and sample track densities or by the repeated calibration of a glass against age standards practical recommendations are given for the reporting and critical assessment of fission track data