abrupt mousterian aurignacian boundary at c 40 ka bp accelerator 14c dates from l arbreda cave catalunya spain abstract the cultural transition from mousterian to aurignacian is abrupt at l arbreda cave and occurs within a homogeneous sedimentary unit with no visible lithologic changes fragments of milligram size charcoal were collected immediately above and below the cultural boundary for radiocarbon dating by accelerator four charcoal fragments from the lowest basal aurignacian level yielded dates of 37 7 1 0 37 7 1 0 39 9 1 2 and 38 7 1 2 ka bp average 38 5 1 0 ka bp these ages are similar to three dates from the same cultural horizon at el castillo cave in cantabria and both sets of dates are significantly older than the earliest reported for the aurignacian in the aquitaine and in other parts of central and western europe the dates are in accord with similarly early dates for aurignacian in bulgaria and suggest that appearance of aurignacian peoples is synchronous across europe three fragments from the uppermost mousterian level yielded dates of 39 4 1 4 34 1 0 75 and 41 4 1 6 ka bp discounting the spurious 34 1 ka bp result these dates are slightly older average 40 4 1 4 ka bp but overlap with counting error the basal aurignacian dates the data show that the transition from mousterian to aurignacian was chronologically abrupt at this location these results strongly support the replacement hypothesis

lake banyoles northeastern spain a last glacial to holocene multi proxy study with regard to environmental variability and human occupation analyses of a 67 m long sediment core from lake banyoles northeastern spain have revealed evidence for the palaeoclimate history of the northern iberian peninsula investigations have included hi

tree roots methodological review and new development in dating and quantifying erosive processes exposed roots have been used in dendrogeomorphology since the 1960s to determine erosion rates this was done by using the root axis as the relative position of the former soil layer and then relating this measure to the age of the root in order to quantify the amount of soil erosion over time recently wood anatomical research revealed the possibility of determining the first year of exposure of roots due to specific anatomical changes within the respective annual ring as a consequence using exposed roots that are still in contact to the soil surface it is possible to reconstruct the size and position of the root at the time of exposure consequently a new equation is presented to calculate the thickness of the eroded soil layer allowing a detailed reconstruction of erosion rates the technique also helps to determine if the root was exposed by erosional processes or just by its ongoing secondary growth without any erosion involved

development of partial rock veneers by root throw in a subalpine setting rock veneers stabilize hillslope surfaces occur especially in areas of immature soil and form through a variety of process sets that includes root throw near westcliffe colorado usa data were collected from a 20 500 m transect on the east slope of the sangre de cristo mountains ages of pit mound complexes with rock fragments exposed at the surface by root throw ranged from recent freshly toppled tree to unknown complete tree decay calculations based on dimensions of the pit mound complexes estimated time of tree toppling sizes of exposed rock fragments and percentage rock covers at pit mound complexes as well as within the transect area indicate that recent rates of root throw have resulted in only partial rock veneering since late pleistocene deglaciation weathering of rock fragments prevents development of an extensive rock veneer and causes a balance achieved within an estimated 700 years between the rates of rock fragment exposure by root throw and clast disintegration by chemical reduction the estimated rate of rock fragment reduction accounts for part of the fluvial sediment yields observed for forested subalpine areas of western north america copyright 2005 john wiley sons ltd

u series dating of fossil teeth and carbonates from snake cave thailand abstract snake cave thailand is an important site for the study of the evolution in southeast asia leading to a discovery of rich and various faunas including a human tooth fossils of large and small mammals converge to indicate on the basis of faunal assemblage a late middle pleistocene age for the fossiliferous layers on the other hand previous u series dating of carbonates furnished a lower limit for the fossils of about 130 ky in order to achieve a better comprehension of the chronology of the cave the uranium series method for absolute age determination has been applied to some carbonates older than those studied previously and to fossils themselves we used the isochron technique approach to yield valuable ages because spleleothem samples consist in a mixture of calcite and detrital contamination the results obtained suggest that the main fossiliferous level is older than about 160 ky the application of the u series method to tooth samples from this tropical cave leads to erroneous ages probably because of post depositional groundwater movements

successful application of uranium series dating of fossil bone abstract a novel approach to uranium series disequilibrium dating is presented and used successfully to date bones from several european archaeological and palaeontological sites a method is described based on a proposed mechanism of uranium uptake and fixation derived from present understanding of the biochemistry of fossilizing bones and the geochemistry of uranium stability of uranium in fossil bone is predicted under particular conditions of local depositional environment and the importance of the inhomogeneous distribution of uranium through bone to uranium series dating is explained sample bones from several different sites have been examined taking into account the three factors of uptake mechanism uranium distribution and sedimentary environment and have yielded ages in good agreement with those derived by alternative dating methods or from chronologically fixed stratigraphical positions

new slip rate estimates for the creeping segment of the san andreas fault california new continuous and differential global positioning system gps measurements of recent slip rates and 30 yr alignment array offsets from the central creeping segment of the san andreas fault yield a maximum right lateral slip rate of 25 1 mm yr this slip rate is 20 slower than the 30 mm yr slip rate accepted for this segment of the fault and 35 slower than the 39 mm yr slip rate predicted between the sierra nevada great valley block and the pacific plate new continuous gps measurements between pairs of sites that flank the creeping segment at intersite distances of 1 0 km and 70 km give relative fault parallel slip rates of 28 2 and 30 2 mm yr respectively these observations indicate that right lateral deformation rates increase with distance from the fault possible explanations for the gradient observed in the geodetic data are elastic strain accumulation along the creeping segment or significant distributed deformation on off fault structures

u series dates for stalagmitic flowstone e riss wurm interglaciation at grotte du lazaret nice france abstract several samples of stalagmitic flowstone ensemble e at grotte du lazaret nice france were dated by u series isotopes the results show that this speleothem began to grow about 130 000 yr b p and continued to about 70 000 yr b p coinciding almost exactly with the last interglaciation isotope stage 5 even though ensemble e is not in direct stratigraphic relation with the cave deposits this study shows that the acheulian artifacts industry and fauna within lazaret are older than the riss wurm interglaciation

u series dating of collagen a step toward direct u series dating of fossil bone abstract fossil bones are often the only material that may be dated by numerical methods a commonly accepted method of bone dating is the radiocarbon method but radiocarbon dating is limited to material younger than 40 60 ka to date direct dating of bone samples by u series methods has not been successful because of post depositional uranium uptake this paper tests the use of u series dating of bones in a new way by dating the collagen extracted from fossil bones low uranium content in collagen extracted from recent and fossil bones suggests that no uranium accumulates in this bone phase ratios of c n commonly used as an indicator of bone preservation were also measured here modern bones and bone collagen showed 230 th activity at background levels confirming their recent age u series and radiocarbon methods applied to collagen extracted from fossil bone of ursus spelaeus collected in magurska cave tatra mts poland gave consistent results analyses of collagen extracted from bones collected in bi nik cave krakow wielun upland poland indicate that there is a high risk of contamination by modern material especially when working with large samples close to the dating method limit

erosion balance and slope evolution under continental humid temperate climate an appalachian example quebec canada abstract solid and dissolved matter net output from a sample slope subdivided into 5 homogeneous segments is estimated from multi annual erosion measurements in a small low relief watershed covered with till derived soils chemical processes prevail all over except on the most inclined segments 8 10 mainly in the slope inflexion zone this is consistent with the constantly humid climate the fresh earth material and the dense vegetation cover polynomial fitting of solute and total losses against slope length and angle are used to predict profile evolution the latter thus mainly results from rock controlled lowering of the inferior segments on which water maintains its aggressiveness and backwearing of the inflexion zone where mechanical action prevails altitude differences which are controlled by unequal rock resistance consequently should increase since weathering on upper segments under podzolisation processes should be less and less effective because of the depletion of easily alterable minerals this trend can be suspended by surficial horizon ablation triggered by treethrow and natural fires

problems encountered in the u th dating of fossil red deer jaws bone dentine enamel from lazaret cave a comparative study with early chronological data previous chronological data such as biochronological data u series and electron spin resonance esr data on stalagmitic flowstone e and samples from the sea deposit b are discussed most of these early studies show a deposition of the archaeological levels c during the oxygen isotopic stage 6 for testing the u th dating the method was applied for the first time to the three tissues bone dentine and enamel from fossil cervus elaphus jaws in order to date directly the archaeological levels of lazaret cave twenty seven bones 21 dentine and 17 enamel samples from 30 jaws and two tibias have been analysed by alpha spectrometry the results show a large range of apparent dates with an open system behaviour for the majority of samples the ages range between 50 and 200 ka the main set of data shows that the ages increase upward in the stratigraphic sequence with low values near the base of the sequence the u th apparent ages of dentine are in better agreement with the ages of their respective enamels than with bones the older the u th ages of the bones the larger the uranium content difference between the bone and dentine samples from the same mandible is observed for some samples from all levels of the continental fill a sequence of episodes of uranium isotope leaching and accumulation has resulted in increased uranium isotope ratios and modified uranium content yielding anomalous ages at lazaret cave u th dating on bone and dentine was not successful but data will be used for esr dating

association between cedar decline and hillslope stability in mountainous regions of southeast alaska old growth forests experiencing widespread decline of yellow cedar chamaecyparis nootkatensis in southeast alaska have a 3 8 fold increase in the frequency of landslides we report here on an investigation of the cause of this increased slope instability time since death of cedar was assessed using surveys around landslide sites root decay on dead trees was used to estimate the decline in the apparent soil strength provided by roots changes in soil hydrology were measured with 120 piezometers located in areas of healthy cedar healthy spruce hemlock and sites with cedar decline relative influences on slope stability by changes in soil moisture and root strength were evaluated with a simple stability model at most sites soil depth is 0 7 m and the loss of root strength has an important and possibly dominant influence on slope instability in soils deeper than 1 m changes in pore pressure have a proportionately larger influence on slope stability landslides appear most likely when cedar decline reaches snag class iv approximately 50 years after tree death when most of the cedar root strength is lost and root strength from secondary growth has yet to develop

geochronology of early human settlements in java what is at stake abstract despite the fact java island is a volcanic area it has been challenging to build a chronological framework of its early human settlements from the oldest lower pleistocene homo erectus up to the dispersals that followed the last glacial maximum lgm various dating methods are implemented on volcanic effluents sedimentary deposits speleothems and also on fossils including direct analyses on human remains thanks to radiometric and palaeodosimetric grounded techniques as well as to magnetostratigraphy however a number of results must be considered with caution in order to identify specific bias originating from reworking of volcanic effluents or post depositional geochemical evolution such bias might well explain apparent contradictions between absolute dating results and other chronologically significant proxies e g biostratigraphy converging age estimates resulting from the implementation of several dating methods though being sometimes less precise seem to have a higher reliability

a physics based approach of deep interseismic creep for viscoelastic strike slip earthquake cycle models most geodetic inversions of surface deformation rates consider the depth distribution of interseismic fault slip rate to be time invariant however some numerical simulations show down dip penetration of dynamic rupture into regions with velocity strengthening friction with subsequent up dip propagation of the locked to creeping transition recently bruhat segall 2017 developed a new method to characterize interseismic slip rates that allows slip to penetrate up dip into the locked region this simple model considered deep interseismic slip as a crack loaded at its down dip end and provided analytical expressions for stress drop within the crack slip and slip rate along the fault this study extends this approach to strike slip fault environments and includes coupling of creep to viscoelastic flow in the lower crust and upper mantle we employ this model to investigate interseismic deformation rates along the carrizo plain section of the san andreas fault this study reviews possible models elastic and viscoelastic for fitting horizontal surface rates using this updated approach we develop a physics based solution for deep interseismic creep which accounts for possible slow vertical propagation and investigate how it improves the fit of the horizontal deformation rates in the carrizo plain region

the velocity field along the san andreas fault in central and southern california the velocity field within a 100 km broad zone centered on the san andreas fault between the mexican border and san francisco bay has been inferred from repeated surveys of trilateration networks in the 1973 1989 interval the velocity field has the appearance of a shear flow that remains parallel to the local strike of the fault even through such major deflections as the big bend of the san andreas fault in the transverse ranges of southern california across strike profiles of the fault parallel component of velocity exhibit the expected sigmoidal shape whereas across strike profiles of the fault normal component of velocity are flat and featureless no significant convergence upon the fault is observed even along the big bend sector of the fault simple dislocation models can explain most of the features of the observed velocity field but those explanations are not unique about 35 mm yr of relative plate motion is accounted for within the span of the trilateration networks geologic studies indicate that the secular slip rate on the san andreas fault is about 35 mm yr the agreement between these two estimates implies that most of the strain accumulation is elastic and will be recovered in subsequent earthquakes the relative motion observed across the san andreas fault 35 mm yr plus that observed across the eastern california shear zone 8 mm yr accounts for most 43 mm yr of the observed north america pacific relative plate motion 47 mm yr

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

laser ablation u series analysis of fossil bones and teeth abstract over the past decade we have applied laser ablation icp mass spectrometry u series analysis to a large number of bones and teeth the method is fast and provides high resolution data of u series isotopes which give insights into the complexity of uranium migration into within and out of bones in this paper we present our laser ablation approach in detail from the experimental set up to data reduction and uranium diffusion modelling laser ablation analysis can now be applied with minimum damage complete diffusion data sets can be obtained by laser drilling which leaves a hole of around 200 m in diameter and 1 2 mm depth if the natural u diffusion follows a simple single stage process valuable age information can be obtained in other cases highly complex u migrations have been observed which make any age assessment impossible two examples from wadjak and callao illustrate the potential of nearly non destructive laser ablation u series analysis of human skeletal tissues the results demonstrate the physical presence of modern humans in south east asia at a time when our species just started to migrate into europe

geologic versus geodetic deformation adjacent to the san andreas fault central california we combine geologic and global positioning system gps data to characterize the style and magnitude of off fault deformation across the san andreas fault system in central california geologic structures record 12 km of both fault parallel and fault perpendicular displacements across creeping and locked portions of the san andreas fault analysis of 150 gps site velocities suggests that the borderlands record 4 6 mm yr of fault parallel and 3 5 mm yr of fault perpendicular motion alongside the creeping segment where elastic strain is minimized the distribution of both long term geologic and short term geodetic deformation is affected by basement type where more deformation is concentrated northeast of the san andreas fault on franciscan basement we suggest that at least half the fault parallel gps deformation measured by gps bordering the creeping segment must be accommodated by geologic structures this permanent deformation needs to be incorporated into dynamic models of the fault system elastic modeling of the san andreas fault in central california which incorporates its well known transition from locked to creeping behavior near parkfield predicts first order variations in the gps velocity field along the fault and corresponding variations in dilatational strain rates the strain rate pattern is dominated by a large contractional region northeast of the transition from locked to creeping behavior and a large extensional region southwest of the transition the former coincides with the coalinga and kettleman hills anticlines the growth and development of which seem to have occurred under at least two kinematic conditions we suggest that the onset of fault creep in central california promoted the growth of these folds by implication fault creep has been active over geologic time scales

the last interglaciation in alaska stratigraphy and paleoecology of potential sites at least 20 localities in alaska contain deposits that may provide information on the last interglaciation oxygen isotope substage 5e these widely dispersed localities include river bluffs coastal bluffs and terraces elevated marine shorelines lake basins and artificial excavations most of the inferred interglacial deposits contain macrofossils or pollen that are older than the range of radiocarbon dating and commonly indicate climate as warm as or warmer than the present at a few localities evidence for deep thaw of permafrost also indicates a warm paleoclimate at eight localities the old crow tephra occurs at or below organic deposits that may represent substage 5e the tephra occurs beneath conspicuous organic deposits at fairbanks the yukon palisades and holitna lowland and directly above a peat bed at hogatza mine at birch creek halfway house ky 11 and imuruk lake the tephra occurs within a paleosol or organic deposit but other organic horizons that more likely indicate interglacial conditions occur at higher stratigraphic levels the varied stratigraphic relations of the old crow tephra suggest that it may have been deposited close to the boundary between isotope substages 6 and 5 which is dated at about 130 ka in the marine record and between 132 and 140 ka on land these age relations suggests that the tephra may have been deposited about 135 5 ka validating the recent fission track age determination of 140 10 ka for this deposit six coastal localities contain deposits of probable interglacial age and these commonly are associated with evidence for eustatic sea levels higher than those of the present beach and sublittoral sediments of the pelukian transgression occur up to 12 m asl along the northwest coast of alaska and are correlative with barrier island and lagoonal sediments on the alaskan arctic coastal plain both sets of deposits commonly contain extralimital mollusks and microfauna that indicate marine water slightly warmer than present and suggest that seasonal sea ice did not extend south of bering strait during the last interglacial as it does today farther south elevated marine terrace deposits on amchitka island contain marine invertebrates that indicate a climate warmer than at present peat horizons in coastal exposure at goose bay and coastal terraces at lituya bay contain pollen spectra that suggest forests like those of the present day and spruce macrofossils exposed on baldwin peninsula indicate boreal forest more extensive than at present sediments from several lakes in northwestern alaska may contain continuous records of the last interglaciation a major warm interval possibly isotope substage 5e has been identified in a core from squirrel lake by a peak in picea pollen that indicates forest extension beyond present limits similar pollen records are potentially available from two maars which formed in the cape espenberg area more than 125 ka terrestrial organic deposits thought to record the last interglaciation occur interstratified with marine and glaciogenic sediments in the nushagak lowland of southwest alaska and on baldwin peninsula in kotzebue sound extensive exposures along the copper and nenana rivers may also contain organic deposits that record the last interglaciation

influences stationnelles sur l alteration chimique des sols derives de till sherbrooke que canada abstract in a small watershed of the canadian appalachians five trenches were studied in two catenas facing each other one forested the other under recent prairie vegetation 100 years of age to investigate the character of chemical weathering in these sites on the top of the forested catena there was a humo ferric fragic podzol and further down and orthic gleysol the other catena had a humo ferric fragic podzol then downwards a grey gleyified luvisol and a luvic fragic gleysol percolating waters near these trenches were sampled regularly at various depth the distribution of the ions on the meadow side indicated on one hand that h 4 sio 4 na and mg 2 in percolating waters are related to the total volume of soil through wich waters percolate that the dissolution of aluminium is accelerated in acid sites upslope and that the solubility of iron reaches a maximum in the zone influenced by the water table on the other hand calcium which is easily liberated in the high sections is in part fixed when the solutions get concentrated iron and aluminium are soon traped silicium is less mobile than the basic cations the constituants of primary minerals organize as follows concentration of al 2 o 3 and fe 2 o 3 upslope when the contrary is for the basic oxydes and sio 2 this trend stands out more clearly in the top 30 cm thus on top of the forested catena chemical weathering is intense the aluminium and iron oxydes are highly evacuated in this podzol at the same altitude in the prairie podzol which probaly had 100 years ago a less acidifying vegetation hardwoods than in the first case feldspars and micas are degraded and we find mostly transformed minerals montmorillonite al minerals are very much less degraded downslope because of their confined position and the high ionic content of the percolating waters

1855 and 1991 surveys of the san andreas fault implications for fault mechanics two monuments from an 1855 cadastral survey that span the san andreas fault in the carrizo plain have been right laterally displaced 11 0 2 5 m by the 1857 fort tejon earthquake and associated seismicity and afterslip this measurement confirms that at least 9 5 0 5 m of slip occurred along the main fault trace as suggested by measurements of offset channels near wallace creek the slip varied by 2 to 3 m along a 2 6 km section of the main fault trace using radiocarbon dates of the penultimate large earthquake and measurements of slip from the 1857 earthquake we calculate an apparent slip rate for the last complete earthquake cycle that is at least 25 lower than the late holocene slip rate on the main fault trace comparison of short term broad aperture strain accumulation rates with the narrow aperture late holocene slip rate indicates that the fault behaves nearly elastically over a time scale of several earthquake cycles therefore slip in future earthquakes should compensate the slip rate deficit from the 1857 earthquake

three dimensional investigation of a 5 m deflected swale along the san andreas fault in the carrizo plain topographic maps produced from light detection and ranging lidar data are useful for paleoseismic and neotectonic research because they pro vide submeter representation of faulting related surface features offset measurements of geomorphic features made in the field or on a remotely sensed imagery commonly assume a straight or smooth i e undeflected pre earthquake geometry here we present results from investigation of an 20 cm deep and 5 m wide swale with a sharp bend along the san andreas fault saf at the bidart fan site in the carrizo plain california from analysis of lidar topography images and field measure ments the swale was initially interpreted as a channel tectonically offset 4 7 m our observations from exposures in four backhoe excavations and 25 hand dug trenchettes show that even though a sharp bend in the swale coincides with the trace of the a d 1857 fault rupture the swale formed after the 1857 earthquake and was not tectonically offset subtle fractures observed within a surficial gravel unit overlying the 1857 rupture trace are similar to fractures previously documented at the phelan fan and ly4 paleoseismic sites 3 and 35 km northwest of bidart fan respectively collectively the fractures suggest that a post 1857 moderate magnitude earthquake caused ground cracking in the carrizo and cholame stretches of the saf our obser vations emphasize the importance of excavation at key locations to validate remote and ground based measurements and we advocate more geomorphic characterization for each site if excavation is not possible online material figures of trench logs

radiometric dating of quaternary deposits and the hominid mandible of lake banyolas spain we report results of u series analyses of the travertine matrix surrounding the banyolas mandible that indicate an age of 45 4 ka bp the mandible an archaic hominid fossil generally deemed of mid pleistocene age was recovered from a travertine matrix in 1887 similar analyses on 21 travertine samples from quarries near the discovery site yield coherent u series dates in correct stratigraphic order ranging from 44 ka bp to 117 ka bp isotopic composition of these samples and the mandible matrix show no evidence of open system behaviour coherent isotopic results from adjacent quarries support the validity of the date on the mandible travertine and we conclude the mandible is much younger than previously believed

age of the final middle palaeolithic and uluzzian levels at fumane cave northern italy using 14c esr 234u 230th and thermoluminescence methods abstract this article presents and discusses the chronological layout of the final mousterian and uluzzian levels of fumane cave in northern italy using 14 c esr and tl methods given its complex sedimentary and cultural succession fumane is a key site to assess the middle upper palaeolithic transition in southern europe and to explore neanderthal behaviour and to compare it with the first aurignacians large ranges defined by the esr and tl dates cover the radiocarbon ages for units from a11 to a4 respectively from 42 8 to 32 5 ka bp become progressively younger in agreement with the stratigraphy despite high dispersions within the same unit our estimates using chronometric data seem to support the hypothesis that the sequence may cover almost 10 000 radiocarbon yr and that from comparison with the sedimentological and palaeoecological data the late middle palaeolithic and the early upper palaeolithic at fumane occur in sediments formed under moderately cool to mild climatic conditions correlated to the hengelo interstadial shifting towards cooler and drier conditions finally comparisons between the fumane data set and other sites in the north adriatic region are discussed

plant induced weathering of a basaltic rock experimental evidence abstract the active role of higher plants in the weathering of silicate minerals and rocks is still a question for debate the present work aimed at providing experimental evidence of the important role of a range of crop plants in such processes in order to quantitatively assess the possible effect of these diverse plant species on the weathering of a basaltic rock two laboratory experiments were carried out at room temperature these compared the amounts of elements released from basalt when leached with a dilute salt solution in the presence or absence of crop plants grown for up to 36 days for si ca mg and na plants resulted in an increase in the release rate by a factor ranging from 1 to 5 in most cases ca and na seemed to be preferentially released relative to other elements suggesting that plagioclase dissolved faster than the other constituents of the studied basalt negligible amounts of fe were released in the absence of plants as a consequence of the neutral ph and atmospheric po2 that were maintained in the leaching solution however the amounts of fe released from basalt in the presence of plants were up to 100 to 500 fold larger than in the absence of plants for banana and maize the kinetics of dissolution of basalt in the absence of plants showed a constantly decreasing release rate over the whole duration of the experiment 36 days no steady state value was reached both in the absence and presence of banana plants however in the latter case the rates remained at a high initial level over a longer period of time up to 15 days before starting to decrease for fe the maximum rate of release was reached beyond 4 days and this rate remained high up to 22 days of growth of banana the possible mechanisms responsible for this enhanced release of elements from basalt in the presence of plants are discussed although these mechanisms need to be elucidated the present results clearly show that higher plants can considerably affect the kinetics of dissolution of basalt rock therefore they need to be taken into account when assessing the biogeochemical cycles of elements that are major nutrients for plants such as ca mg and k but also micronutrients such as fe and nonessential elements such as si and na

fault slip and earthquake recurrence along strike slip faults contributions of high resolution geomorphic data article i nfo understanding earthquake eq recurrence relies on information about the timing and size of past eq ruptures along a given fault knowledge of a fault s rupture history provides valuable information on its potential future behavior enabling seismic hazard estimates and loss mitigation stratigraphic and geomorphic evidence of faulting is used to constrain the recurrence of surface rupturing eqs analysis of the latter data sets culminated during the mid 1980s in the formulation of now classical eq recurrence models now routinely used to assess seismic hazard within the last decade light detection and ranging lidar surveying technology and other high resolution data sets became increasingly available to tectono geomorphic studies promising to contribute to better informed models of eq recurrence and slip accumulation patterns after reviewing motivation and background we outline requirements to successfully reconstruct a fault s offset accumulation pattern from geomorphic evidence we address sources of uncertainty affecting offset measure ment and advocate approaches to minimize them a number of recent studies focus on single eq slip distribu tions and along fault slip accumulation patterns we put them in context with paleoseismic studies along the respective faults by comparing coefficients of variation cv for eq inter event time and slip per event and find that a single event offsets vary over a wide range of length scales and the sources for offset variability differ with length scale b at fault segment length scales single event offsets are essentially constant c along fault offset accumulation as resolved in the geomorphic record is dominated by essentially same size large offset in crements and d there is generally no one to one correlation between the offset accumulation pattern constrained in the geomorphic record and eq occurrence as identified in the stratigraphic record revealing the higher resolution and preservation potential of the latter while slip accumulation along a fault segment may be dominated by repetition of large nearly constant offset increments timing of surface rupture is less regular

stratigraphic evidence for seven meters of dextral slip on the san andreas fault during the 1857 earthquake in the carrizo plain the smallest geomorphic offsets along a 35 km section of the san andreas fault in the carrizo plain vary from 7 to 10 m our three dimensional excavation of alluvial deposits a few km southeast of wallace creek confirms that at least 6 6 to 6 9 m of dextral slip occurred there during the latest large earthquake in 1857 dates on detrital charcoal suggest that the last event prior to the 1857 earthquake occurred before a date within the range a d 1305 to 1623 the 3 m range in smallest offsets along this portion of the fault may reflect either a 3 m variation in slip along the san andreas in 1857 or 2 to 3 m of slip during an event prior to 1857 observations made after the recent landers earthquake are compatible with the hypothesis of large local variations in slip during a single earthquake but do not explain the cause of such variations off fault dextral rotations would be one plausible explanation however paleoseismic data in the carrizo plain are too sparse to allow rejection of the alternative hypothesis that slip in the event prior to 1857 was only 2 to 3 m an amount of slip which would be several times too small to fit a time predictable model

longevity of treethrow microtopography implications for mass wasting abstract this study examines and compares methods of dating pit mound microtopography formed by tree uprooting and provides 14 c evidence for the longevity of these landforms microtopography can often by dated by reference to known meteorological phenomena or within certain age constraints by dendrochronologic means we used 14 c analysis of buried wood and charcoal in treethrow mounds in michigan and wisconsin u s a to arrive at estimates of the geochronometric ages of treethrow mounds results indicate that mounds in these areas often persist for more than 1000 years which are two to five times longer than published estimates by less reliable methods the longevity of treethrow mounds in these regions is ascribed to l sandy porous soils which minimize runoff 2 a continuous mat of forest litter and vegetation cover 3 surface concentrations of gravel which may act as an armor 4 large initial size of the features and 5 soil freezing implications are that rates of mass movement due to uprooting may be substantially less than studies from other regions suggest

tectonic geomorphology of the san andreas fault zone from high resolution topography an example from the cholame segment abstract high resolution topographic data along fault zones are important aids in the delineation of recently active breaks a 15 km long portion of the south central san andreas fault saf along the southern cholame segment contains well preserved tectonic landforms such as benches troughs scarps and aligned ridges that indicate recurring earthquake slip recently acquired lidar topographic data along the entire southern saf b4 project have shot densities of 3 4 m 2 computed from the lidar returns digital elevation models dems of 0 25 to 0 5 m resolution using local binning with inverse distance weighting and 0 8 m or larger search radii depict the tectonic landforms at paleoseismic sites well enough to assess them confidently mapping of recently active breaks using a lidar only based approach compares well with aerial photographic and field based methods the fault zone varies in width from meters to nearly 1 km and is comprised of numerous en echelon meter to kilometer length overlapping sub parallel fault surfaces bounding differentially moving blocks that elongate parallel to the saf the semantic variations of what constitutes active and the importance of secondary traces influence the breadth and complexity of the resulting fault trace maps

geochronological position of badlands and geomorphological patterns in the guadix baza basin se spain abstract the guadix baza basin is one of a number of intramontane depressions located within the betic cordillera se spain where the geological and geomorphological evolution is controlled by tectonic activity the basin ceased to be closed after capture by the atlantic network when five main land systems developed late pleistocene geological evolution basically consisted of erosional modelling when badlands were deeply incised in highly erodible materials marls and silts three travertine platforms and several palaeolithic sites were used to determine that this main incision period fell within a 115 000 48 000 yr range there are few signs of geomorphological evolution of this basin in the last 48 000 yr based on these geomorphological data and soil development tectonic uplift of the basin probably played a secondary role in its evolution and climatic conditions in southern iberia in the 144 000 48 000 yr period were more humid and variable than later

chemical weathering studies in relation to geomorphological research in southeastern canada abstract although chemical weathering provides fundamental information relevant to geomorphology the subject has been overlooked during the 20th century in canada this paper provides an overview of the current state of canadian research on chemical weathering in southeastern canada and takes into account three spatial and temporal contexts 1 the formation of bedrock morphology by chemical weathering 2 occurrences characteristics and age of saprolites and 3 contemporary chemical denudation rates long term geomorphological evolution of southeastern canadian landscapes shows that chemical weathering has played an important role an example is taken from the laurentide region of the canadian shield north of montreal quebec the present topography resulted from the stripping of the former weathering mantle and from the probable subsequent modification of the weathering front first by the action of hillslope processes and rivers and then by glaciers before and during plio pleistocene times the present landscape reflects the timing of the formation of erosion surfaces and of the stripping of the paleozoic cover rocks and exposure of the shield since the late seventies several isolated occurrences of saprolite soil profiles have been discovered in eastern canada and prompted a renewal of the study of these materials about the cenozoic evolution of these regions one of the problems in this field of research is the dating of saprolites and their inclusion in a chronostratigraphic framework along with the other cenozoic surficial deposits and landforms because of the multiple factors involved in the development of secondary minerals in saprolites during the course of weathering it is preferable to distinguish the dating of saprolites from the study of their mineralogical and geochemical evolution fortunately several new techniques are becoming available for the absolute dating of surficial deposits and saprolites including the use of cosmogenic radionuclides saprolites provide a strong potential field of research for our understanding of the geological evolution of eastern canada during the cenozoic contemporary weathering and erosion rates are fields of research that have gained increasing interest recently since modeling landscape geochemical response can be applied to various environmental stress situations such as acidification by rain and forest harvesting rock type may be the main factor explaining the large differences between watersheds in fact variability of cation removal in the temperate zone is probably most closely related to flow paths of water investigations at different scales from entire watersheds to slopes to individual pedons highlight the problem in the catamaran brook watershed new brunswick water chemistry is explained by a mix of groundwater and soil solution from the horizons at the base of the floodplain soils geochemical mass balances based on net outputs give little information on the weathering reactions of primary minerals the weathering products or on the nature of the weathering processes that provide the dissolved load of streams mineralogic and petrographic analysis of selected soil pedons are necessary to determine weathering reactions and their role as sources or sinks for bases silica aluminum and iron in the various compartments through which water percolates before it reaches the stream

the role of trees in the geomorphic system of forested hillslopes a review abstract forested hillslopes form a special geoecosystem an environment of geomorphic processes that depend strongly on forest ecology including the growth and decay of trees changes in structure disturbances and other fluctuations hence the following various functions of trees are reviewed here their role in both biomechanical and biochemical weathering as well as their importance for the hillslope geomorphic subsystem and for transport of soil material via tree uprooting and root growth special attention is paid to tree uprooting a process considered the most efficient and most frequent biogeomorphological indicator of bio physical activity within forest in complex terrain trees have varied implications for soil formation in different environments boreal to tropical forests and altitudes in this paper an attempt has been made to emphasize how trees not only modulate geomorphic processes but also how they act as a direct or indirect agent of microrelief formation the most striking example of which being widespread and long lasting pit and mound microtopography based on the analyzed literature it seems that some problems attributed to forest ecology can have a fundamental effect on forested hillslope dynamics a relationship which points to the need for its integration and interpretation within the field of geomorphology the biology of individual trees has a key influence on the development of e g rock faces weathering front migration and changes in the soil biomantle within upper and lower forest belts additionally forms and sediments depend largely on the horizontal and vertical extent volume and structure of root systems as well as on active processes taking place in the root zone and rhizosphere furthermore although trees to a large extent stabilize slope surfaces their presence can also have a dual effect on slope stability due to tree uprooting a process which in some circumstances can trigger mass movements e g debris avalanches so far several attempts at quantifying the influence of trees on slopes have been made via the use of mathematical equations enabling researchers to calculate 1 the root plate volume of uprooted trees 2 the amount of soil displacement due to tree root growth and 3 rates of erosion sedimentation and soil creep in light of the reviewed literature the most urgent issue appears to be the need for a thorough study of the interactions and feedbacks occurring between trees and geomorphic systems e g soil mixing and biotransport by trees in different climate zones altitudes and time frames especially in terms of the development of forest ecosystems during the holocene

landslides on coastal sage scrub and grassland hillslopes in a severe el nino winter the effects of vegetation conversion on sediment delivery during the 1997 1998 el nino record rainfall triggered 150 shallow landslides within a 9 5 km2 area near santa barbara cal ifornia they were studied to analyze the sediment delivery to val ley floors from landslides in coastal sage scrub and converted grasslands the conversion of coastal sage to grasslands primarily to provide pasturage for cattle is common in the region and the landscape s response may affect water quality reservoir infilling and debris flow hazards we explore the relationship between lateral root reinforcement and landslide volume by developing a slope stability analysis that incorporates root cohesion along the sides of the failure the stability analysis correctly predicts an inverse re lationship between landslide volume and hillslope angle in the sage the volumes of failures in the grasslands do not vary systemati cally with slope and are generally smaller than those in the sage from aerial photograph analysis and field mapping we find that there are 22 9 failures per square kilometer in the grasslands com pared to 13 2 failures per square kilometer in the sage despite the lower failure density in the coastal sage greater failure volumes and longer transport distances delivered more sediment to valley floors with a specific volumetric flux of 2 8 3 10 2 m 3 m 1 for this el nino compared to 1 73 10 2 m 3 m 1 in the grasslands we con clude that the conversion from vegetation with stronger and deeper roots coastal sage to vegetation with weaker and shallower roots grass has caused a pulse of increased landsliding in the grasslands because the soils are currently too thick for the prevailing root reinforcement we suggest that over time soils in the grassland hollows will become thinner as the evacuation by landslides is re peated until the landsliding rate declines to balance the soil sup plied from local colluvium production and diffusive processes upslope

the lower acheulian site of ambrona soria spain ages derived from a combined esr u series model abstract the lower paleolithic sites of ambrona and torralba soria spain are often associated with each other because of their proximity although they do not represent the same morphostratigraphic unit systematic and extensive excavations were conducted at these sites by an american team during the 1960s and 1980s recently 1989 2000 a spanish team has reactivated the research by initiating a new interdisciplinary project in the central sector and west of the ambrona site a stratigraphy has been established with six units from as1 at the base to as6 at the surface corresponding to fluvial lacustrine deposits in which abundant fauna associated with acheulian artefacts were found the most abundant species were elephant horse deer and aurochs other species like carnivores occur in small numbers only the lithic assemblage is relatively sparse and consists of a few bifaces choppers and several flake tools distributed throughout levels as1 to as5 the fauna and the lithic industry therefore document human presence at ambrona during the middle pleistocene in order to verify the presumed antiquity of the ambrona deposits horse teeth sampled in levels as1 as2 and as6 were analysed using combined esr u series us methods the samples from the lower levels as1 and as2 underwent a very recent uranium uptake as indicated by the u series dates ranging between 5 and 18 ka in contrast a more conventional postmortem uranium uptake was observed in the upper level samples as6 in the enamel and dentine tissues while a light u leaching was observed in the cementum the combined esr u series dates obtained on these samples suggest a minimum age of approximately 350 ka contemporaneous of osi 9 or the end of osi 11 for the ambrona site

u series dating of impure carbonates an isochron technique using total sample dissolution abstract u series dating is a well established technique for age determination of late quaternary carbonates materials of sufficient purity for nominal dating however are not as common as materials with mechanically inseparable aluminosilicate detritus detritus contaminates the sample with extraneous th we propose that correction for contamination is best accomplished with the isochron technique using total sample dissolution tsd experiments were conducted on artificial mixtures of natural detritus and carbonate and on an impure carbonate of known age results show that significant and unpredictable transfer of radionuclides occur from the detritus to the leachate in commonly used selective leaching procedures the effects of correcting via leachate residue pairs and isochron plots were assessed isochrons using tsd gave best results followed by isochron plots of leachates only

quaternary tectonic activity of the carboneras fault in the la serrata range se iberia geomorphological and chronological constraints the eastern betic shear zone ebsz in southern iberia is known to accommodate part of the 4 5 mm yr convergence between africa and iberia but its seismic hazard is not sufficiently understood for an accurate risk assessment one of the main structures of the ebsz the left lateral 150 km long carboneras fault displays no clear instrumental and historical activity despite being morphologically expressive detailed geomorphological mapping geochronological analysis and structural observation on the la serrata segment of the carboneras fault were designed to investigate its recent evolution quaternary sediments and geomorphic features were targeted and 42 new numerical ages were obtained based on 66 samples thermoluminescence u series 14c 10be the chronological framework of la serrata was constructed by combining these numerical ages with a conceptual model previously developed in the region which assumes that alluvial fan aggradation was produced during cold and dry periods glacials and stadials whereas stability and phases of calcrete formation were favored during warm and wetter periods interglacials and interstadials the spatial distribution of dated alluvial fans suggests an early phase of uplift that probably occurred between 1 ma and 56 6 ka in the northeastern portion of the study area whereas in the southwest sector the main uplift phase occurred later than 110 3 ka a decline in fault activity would have taken place after 30 8 ka vertically offset dated units indicate minimum dip slip rates of 0 05 mm yr and 0 18 mm yr averaged for the last 1 ma and the last 110 3 ka respectively deflected channels and associated dated units yield a minimum left lateral strike slip rate of 1 31 mm yr averaged for the last 110 3 ka the most recent fault movement of the fault could be younger than ad 637 our results suggest therefore that the carboneras fault is among the fastest in iberia and should be considered in future hazard analyses

surface processes and interactions with forest vegetation on a steep mudstone slope stolowe mountains sw poland abstract in this study we recognize complex physical biotic abiotic interactions on a steep forested slope in the moderately elevated mountain terrain of the sudetes central europe using geomorphological pedological and dendrochronological methods on the forested hillslopes of mt rogowa kopa the evidence of disturbance in natural systems is widespread in the geomorphic subsystem its most obvious manifestation is the origin and disappearance of pit and mound microtopography resulting from tree uprooting 82 pit and mound associations have been mapped on a test slope providing quantitative data for calculating sediment flux the flux is around 2 10 4 m 3 m 1 year 1 hence less than suggested in the literature but within the same order of magnitude nevertheless in the long term such a transport rate is comparable with the one typical for creep while it affects a greater thickness of hillslope regolith tree bending and abrupt changes in tree ring width are indicators of disturbed tree growth causally linked to soil creep of mudstone derived regolith eccentric growth is best recorded in wet years and in younger trees which have to adapt to the pre existing pit and mound surface topography we offer a conceptual model that links biotic and abiotic factors and discuss implications of the widespread tree uprooting we suggest that veneers of angular clasts and occasional larger boulders are not necessarily residuals of washed pleistocene solifluction mantles but may result from root plate degradation after uprooting recent catastrophic wind events may through tree uprooting lead to structural changes in cover deposits so that they lose their inherited periglacial signatures

the age of late pleistocene shorelines and tectonic activity of taranto area southern italy abstract the results of isoleucine epimerization ratios in pelecypods glycymeris sp arca sp and cerastoderma sp and u series dating of bivalves and cladocora caespitosa sampled from different late pleistocene units in the cheradi islands and in the coastal areas of mar piccolo and mar grande near taranto apulia region italy are presented u series measurements on pelecypods and on corals directly associated with mollusc samples provide an independent calibration of amino acid data the d l ratios of isoleucine show a strong correlation with age and thus may be considered as a predictive dating technique this correlation also supports the reliability of u series ages obtained for molluscs these results including the stratigraphic position the lithological lateral continuity the morphological evidence and the palaeontological characteristics of the various units made it possible to attribute them to different marine trangressive phases referable to oxygen isotope stages ois 5e c 5a and 3 no evidence of land emersion between ois 5e and 5c has been found in the area pinkish red sands deposits located above present sea level 1 m have been referred to ois 3 the late pleistocene morphological evolution and uplift of a complex area between the apulian foreland and the bradanic foredeep have been reconstructed due to the lack of incontestable indicators of past sea level stands the facies analysis has been performed on u series dated 89 8 ka ois 5c shoreline north of mar piccolo and an uplift rate ranging from 0 21 0 27 mm yr has been calculated

breaking ground pedological geological and ecological implications of soil bioturbation abstract soil and its biota are fundamental components of the critical zone earth s living skin that most directly sustains life within that zone geologically rapid soil and saprolite displacement by biota particularly invertebrate meso and macrofauna affects a large proportion of earth s soils this was first recognised by late 19th century observers on both sides of the atlantic ocean who regarded bioturbation as fundamental to soil formation throughout much of the 20th century however the agronomical focus of soil scientists and the dominant paradigm of landscape evolution relegated bioturbation as a result many aspects of bioturbation are still not widely appreciated only in the last few decades has a re evaluation commenced in a range of disciplines primary effects of bioturbation which we quantify herein include soil production from saprolite the formation of surface mounds soil burial and downslope transport rates of bioturbation can be as rapid as sustained maximum rates of tectonic uplift in concert with surface geomorphic processes bioturbation alters fundamental properties of soil including particle size distribution porosity the content of carbon and other nutrients and creep flux rate the precise influence of biotic mixing is regulated by its depth function earth s incredibly diverse soil biota also perform a number of functions at a range of spatial and temporal scales that extend beyond soil to landscape evolution ecosystem engineering niche construction and carbon cycling understanding these linkages which have operated since the evolution of trees in the devonian period is of growing importance as we seek a fuller picture of earth s history to predict and manage its future

revised dates of large earthquakes along the carrizo section of the san andreas fault california since a d 1310 30 1 precise knowledge of the age and magnitude of past earthquakes is essential for characterizing models of earthquake recurrence and key to forecasting future earthquakes we present 28 new radiocarbon analyses that refine the chronology of the last five earthquakes at the bidart fan site along the carrizo section of the south central san andreas fault which last ruptured during the fort tejon earthquake in a d 1857 the new data show that the penultimate earthquake in the carrizo plain occurred not earlier than a d 1640 and the modeled 95th percentile ranges of the three earlier earthquakes and their mean are a d 1540 1630 1585 a d 1360 1425 1393 and a d 1280 1340 1310 indicating an average time interval of 137 44 years between large earthquakes since a d 1310 30 a robust earthquake recurrence model of the carrizo section will require even more well dated earthquakes for thorough characterization however these new data imply that since a d 1310 30 the carrizo section has failed more regularly and more often than previously thought

cross dating th u 14c of calcite covering prehistoric paintings in borneo abstract we present the first application of cross dating th u measured by thermo ionization mass spectrometry tims and 14c measured by accelerator mass spectrometry ams of calcite covering prehistoric paintings th u age estimates of cave drapery range from 9800 to 27 300 yr b p while conventional 14c age is estimated between 9900 and 7610 yr b p depending on the dead carbon correction the age discrepancy is attributed to a disturbance of th u and or 14c geochemical systems showing the limits of the geochronological approach applied to this kind of material for the th u system the poor consistency of u data u content 234u 238u activity ratios and apparent ages argue for open system conditions for 14c system variation of the dead carbon fraction dcf and a possible mixing of successive generations of calcite could account for age discrepancy nevertheless one sample shows concordant ages for the two methods compatible ages through corrections for open system conditions are assumed for other samples then the cross dating suggests 9900 yr as the minimum age of the piece of drapery the underlying painting must be older this study of rock art demonstrates the presence of a pleistocene population before 9900 yr in the southeast of borneo whereas previously the only population in evidence in this area was of austronesian type from 5000 to 6000 yrs ago

high resolution topography derived offsets along the 1857 fort tejon earthquake rupture trace san andreas fault the great fort tejon earthquake of 1857 with an 350 km long surface rupture was the most recent major earthquake along the south central san andreas fault saf prior reconstruction of its surface slip distribution and reconstruction of preceding earthquakes along the 1857 rupture trace have contributed to formulation of the characteristic earthquake cem and uniform slip models usm for earthquake recurrence that find wide application in seismic hazard assessment and earthquake forecasting we used the high resolution b4 light detection and ranging lidar topographic data set sufficient for depiction of meter scale tectonic landforms to reevaluate the distribution of surface displacement along the 1857 rupture trace we present 450 offset measurements with displacements below 60 m increasing observation density relative to previous studies by a factor of 2 our results show that the 1857 earthquake had overall an average displacement below 3 5 m with 4 6 m released along the northwestern half of the rupture its along fault slip distribution is smooth at 10 km length scales at 28 less than prior estimates assuming a 10 km rupture depth and a 30 gpa shear modulus reconstruction of pre 1857 earthquakes is impeded by an exponential decrease in observation density with increasing displacement amount offset observation density soon reaches a level where only tentative and nonunique reconstructions are permitted the results of this study question prior surface slipreconstructions of pre 1857 rupture s that were based on a distinctly lower number of offset observations challenging the applicability of the aforementioned earthquake recurrence models to explain saf rupture behavior online material catalog of offset measurements along the 1857 surface rupture trace as well as an annotated map 1 embed inline graphic 1 gif

canadian geomorphology 2000 geomorphology has a distinguished history in canada as old as the country itself initially the science of geomorphology of canada drew on rich british and french scientific traditions but later it developed its own character strongly influenced by the richness and diversity of the canadian landscape the strong imprint of glaciation and the importance of periglacial processes permafrost and sea ice canada is the second largest country in the world its coastline is longer and more varied than that of any other country nearly one third of canada is underlain by permafrost some up to 700 m thick the country s physiography ranges from nearly flat coastal and interior plains to the glacierised mountains of baffin and ellesmere islands british columbia and the yukon its climate and vegetation are equally diverse ranging from the cold semiarid tundra of the high arctic to the temperate rainforest of the pacific coast given this diversity it is not surprising that canada is active in many areas of geomorphic research an incredible spectrum of landforms and geomorphic processes has fostered world class research in canada both by canadians and by scientists from other countries much of this research is field based and empirical rooted in field observation in recent decades however there have been important advances in inductive laboratory and

bioturbation on a south east australian hillslope estimating contributions to soil flux the contribution of bioturbation to downslope soil transport is significant in many situations particularly in the context of soil formation erosion and creep this study explored the direct flux of soil caused by aphaenogaster ant mounding vertebrate scraping and tree throw on a wildfire affected hillslope in south east australia this included the development of methods previously applied to californian gopher bioturbation and an evaluation of methods for estimating the volume of soil displaced by tree throw events all three bioturbation types resulted in a net downslope flux but any influence of hillslope angle on flux rates appeared to be overshadowed by environmental controls over the spatial extent of bioturbation as a result the highest flux rates occurred on the footslope and lower slope the overall contribution of vertebrate scraping 57 0 89 4 g m 1 yr 1 exceeded that of ant mounding 36 4 66 0 g m 1 yr 1 although mean rates were subject to considerable uncertainty tree throw events which individually cause major disturbance were limited in their importance by their scarcity relative to faunalturbation however tree throw might be the dominant mechanism of biotic soil flux on the mid slope provided that it occurs at a frequency of at least 2 3 events ha 1 yr 1 although direct biotic soil flux appears to be geomorphologically significant on this hillslope such transport processes are probably subordinate to other impacts of bioturbation at this site such as the enhancement of infiltration following wildfire copyright 2011 john wiley sons ltd

detailed mass spectrometric u series analyses of two teeth from the archaeological site of pech de l aze ii implications for uranium migration and dating abstract we report th u ages obtained by thermal ionization mass spectrometry of cross sections of two teeth from the archaeological site of pech de l aze ii the aim of this study is to reconstruct the pathways and time dependency of uranium uptake into different constituents of the two teeth a previous esr dating study of the two teeth yielded age estimates in the range of about 130 000 to 200 000 years which was in agreement with the geological assignment of riss for layers from which the specimens were recovered the closed system u series ages of all analyses range from 48 to 137 ka thus yielding age estimates which are between 30 and 90 ka too young the apparent closed system u series ages of the dentine and cement fractions at the top of the teeth are the oldest becoming gradually younger towards the interior of the two teeth the difference between apparent u series ages of dentine at the outer and inner parts of the two teeth is about 35 ka the enamel sections show the same patterns in u concentration and progression of apparent th u ages as the adjacent dentine samples but with generally younger ages our results indicate that uranium migrates both from the top and the base into the dentine of the teeth and from there into the adjacent enamel depending on the position of the sample significant uranium uptake appears to have taken place over many tens of thousands of years modelling the u uptake histories using a parametric model shows that for the cement and dentine components uptake is intermediate between linear uptake lu and early uptake eu closed system the enamel although often assumed to approximate more closely a closed system shows evidence of more recent u uptake these results also imply that it is not possible to use a simple single parameter u uptake model for all components of a given tooth either for u series or esr dating

a test of uranium series dating of fossil tooth enamel results from tournal cave france abstract a series of well preserved mammal bones and horse teeth was analyzed from archaeological levels of tournal cave magdalenian aurignacian and mousterain to test the hypothesis that well crystallized enamel behaves more as a closed system than does whole bone the isotopic composition of bones and tooth enamels from this deposit meet criteria for confidence and gave no reasons to suspect contamination or open system behavior two samples for which231pa could be analyzed showed internal concordance with the respective230th ages in spite of the favourable isotopic criteria however comparison of the u series ages of the bones and the tooth enamel with stratigraphic position and14c control indicated the dates were not meaningful in general both bones and tooth enamels gave ages too young although some were clearly too old neither group showed any systematic increase of age with stratigraphic depth tooth enamel therefore shows no advantage over bone for u series dating for this site in tournal cave both bones and enamel are apparently open to u which is probably cycling as a consequences of post depositional groundwater movement

hydrothermal frictional strengths of rock and mineral samples relevant to the creeping section of the san andreas fault abstract we compare frictional strengths in the temperature range 25 250 c of fault gouge from safod cdz and sdz with quartzofeldspathic wall rocks typical of the central creeping section of the san andreas fault great valley sequence and franciscan complex the great valley and franciscan samples have coefficients of friction 0 35 at all experimental conditions strength is unchanged between 25 and 150 c but increases at higher temperatures exceeding 0 50 at 250 c both samples are velocity strengthening at room temperature but show velocity weakening behavior beginning at 150 c and stick slip motion at 250 c these rocks therefore have the potential for unstable seismic slip at depth the cdz gouge with a high saponite content is weak 0 09 0 17 and velocity strengthening in all experiments and decreases at temperatures above 150 c behavior of the sdz is intermediate between the cdz and wall rocks

quaternary volcano lacustrine patterns and palaeobotanical data in southern armenia the morphogenetic evolution of the lesser caucasus has been strongly influenced by plio quaternary volcanic and tectonic events and pleistocene glaciations fluvio lacustrine environments indicated by diatomaceous deposits prevailed in the syunik region of southern armenia during the pliocene and pleistocene the pleistocene diatomaceous deposits studied contain leaf impressions and pollen allowing local palaeoclimatic reconstructions the chronology of morphogenetic events has been determined by 17 radiometric dates k ar ar ar u th palaeomagnetic investigations and is placed in a spatial context by a detailed geomorphological map and a 24 km geological transect of the vorotan valley the main area studied before 1 21 ma tectonic movements antecedents of the lower part of the vorotan valley generated extensive lake formations with diatomaceous deposits from 993 ka volcanic eruptions produced lava flows that covered the fluvio lacustrine accumulations during marine isotopic stages 12 6 and 4 glaciers and fluvio glacial deposits were probably present overall the principal uplands and valleys of southern armenia at 53 68 ka mis 3 12 6 ka 10 78 ka and 4 14 ka mis 1 the development of travertines on some slopes and in some valleys highlights temperate and humid climatic phases palaeobotanical studies of leaf and pollen floras show that the vegetation changed several times from forested to steppic phases in response to the climate oscillations of the lower pleistocene this work proposes a first morphogenic and palaeoclimatic reconstruction from the lower pleistocene to the postglacial period when the first settlements of the population in the lesser caucasus were influenced by tectono volcanic events lake level changes and glacialeinterglacial oscillations forced by the obliquity orbital parameter 41 ky cycles

breakage or uprooting how tree death type affects hillslope processes in old growth temperate forests abstract tree breakage and uprooting are two possible scenarios of tree death that have differing effects on hillslope processes in this study we aimed to i reveal the long term structure of the biomechanical effects of trees bets in relation to their radial growth and tree death types in four old growth temperate forests in four different elevation settings with an altitudinal gradient of 152 1105 m a s l ii quantify affected areas and soil volumes associated with the studied bets in reserves and iii derive a general model of the role of bets in hillslope processes in central european temperate forests we analyzed the individual dynamics of circa 55 000 trees in an area of 161 ha within four old growth forests over 3 4 decades basal tree censuses established in all sites in the 1970s and repeated tree censuses in the 1990s and 2000s provided detailed information about the radial growth of each tree of dbh 10 cm as well as about types of tree death we focused on the quantification of i surviving still living trees ii new recruits iii standing dead trees iv uprooted trees and v broken trees frequencies of phenomena were related to affected areas and volumes of soil using individual statistical models the elevation contrasts were a significant factor in the structure of bets differences between sites increased from frequencies of events through affected areas to volumes of soil associated with bets an average 2 7 m3 ha 1 year 1 was associated with all bets of the living and dying trees in lowlands while there was an average of 7 8 m3 ha 1 year 1 in the highest mountain site differences were caused mainly by the effects of dying trees bets associated with dead trees were 7 8 times larger in the mountains effects of dying trees and particularly treethrows represented about 70 of all bets at both mountain sites while it was 58 at the highland site and only 32 at the lowland site our results show a more significant role of bets in hillslope processes including slope denudation in the mountains we would expect a significant decrease of the biogeomorphic effect of trees in managed forests but with a greater relative effect in mountains

stream channel offset and late holocene slip rate of the san andreas fault at the van matre ranch site carrizo plain california sets of well preserved channels offset across the san andreas fault saf at the van matre ranch vmr site in the northwestern elkhorn hills area of the carrizo plain offer the opportunity to measure slip rate and examine geomorphic development of the channels the fault zone and offset channels were exposed by excavation in one fault perpendicular and five fault parallel trenches the geomor phology and stratigraphy in the channels reveal a record of filling by fluvial sedi mentation lateral colluviation and pedogenesis the buried thalweg of the currently active channel is offset 24 8 1 m while the geomorphic channel is offset approx imately 27 6 1 m seventeen samples were collected from channel margin deposits for 14 c dating an oxcal model of the radiocarbon dates with stratigraphic control suggests that the oldest date for channel incision was a d 1160 minimum and maximum slip rates ranging from 29 3 to 35 6 mm yr are derived from different assumptions about the timing of channel incision and offset the resulting slip rates at vmr agree well with the late holocene slip rate of 33 9 2 9 mm yr at wallace creek approximately 18 km to the northwest and imply that within measurement uncertainty the 30 37 mm yr velocity gradient across the saf from decadal time scale geodetic measurements is accommodated across the several meter wide saf zone at vmr over the last millennium

reassessment of a slip budget along the parkfield segment of the san andreas fault historically the parkfield segment has represented a transition in fault behavior along the san andreas fault saf despite a 33 mm yr long term slip rate along the saf slip has not been observed on the cholame segment since the great 1857 fort tejon earthquake during that time the parkfield segment has experienced slip from at least six m 6 0 earthquakes aseismic fault creep and from minor earthquakes data from aseismic slip rate studies and historical earthquake studies allow us to estimate the total slip released along this portion of the saf since 1857 assuming the saf should slip at the long term slip rate a slip deficit of 5 m exists along the cholame segment since 1857 the slip deficit is approximately equivalent to 1857 offsets measured on the cholame and the southeast portion of the parkfield segment thus the slip deficit in southeast parkfield and cholame may be as great as the slip accommodated along these segments in 1857 the slip deficit abruptly decreases to the northwest across the parkfield segment it is 2 m near the town of parkfield and 0 m northwest of middle mountain an m 7 event rupturing all or part of the cholame segment and the southeastern parkfield segment slip decreasing to the northwest would release the accumulated slip and is plausible importantly this study also shows that the change in the pattern of strain release occurs in the middle of the parkfield segment rather than at its ends online material tables showing aseismic and coseismic slip estimations and calculations

uncharacteristic earthquakes on the san andreas fault one model of earthquake recurrence holds that large quakes exhibit regular or characteristic rupture patterns combined with a simple picture of how elastic strain accumulates in the faults this implies that characteristic earthquakes occur at regular intervals in her perspective grant proposes that recent data from study sites along the san andreas fault are difficult to understand with this model the earthquake activity is more irregular and more clustered than the model would suggest

a comparative dating study of bones from little hoyle cave south wales u k abstract four animal bones from little hoyld cave an upper palaeolithic site near tenby in southwest wales have been the subject of a comparative dating study each bone has been dated by three methods radiocarbon amino acid racemization and uranium series disequilibrium the latter based on a new approach to fossil bones the results show a good agreement between the methods with ages generally overlapping well within the quoted 2 uncertainties the bones are derived from a cold climate fauna and the mean date of 17 85 0 12 ka bp indicates that they are contemporary with the main late devensian ice advance when the ice sheet reached within 30 km of the cave the date is very similar to that of the paviland burial 18 46 0 34 ka bp bm 374 in nearby gower which was also ice free during the late devensian glacial maximum

on the limits of using combined u series esr method to date fossil teeth from two early pleistocene archaeological sites of the orce area guadix baza basin spain abstract article history received 6 june 2011available online 9 february 2012keywords combined u series esr dating methodfossil teethfuente nueva 3barranco leonorceearly pleistocene the combined u series electron spin resonance esr dating method was applied to nine teeth from twoearly pleistocene archaeological sites located in the orce area guadix baza basin southern spain fuentenueva 3 fn 3 and barranco leon bl the combination of biostratigraphy and magnetostratigraphy placesboth sites between the olduvai and jaramillo subchrons 1 78 1 07 ma our results highlight the dif culty of dating such old sites and point out the limits of the combined u series esr dating method based on the us model we identi ed several sources of uncertainties that may lead toinaccurate age estimates seven samples could not be dated because the dental tissues had 230 th 234 u ac tivity ratios higher than equilibrium indicating that uranium had probably leached from these tissues it washowever possible to calculate numerical estimates for two of the teeth both from fn 3 one yielded a middlepleistocene age that seems to be strongly underestimated the other provided an age of 1 19 0 21 ma inagreement with data obtained from independent methods the latter result gives encouragement thatthere are samples that can be used for routine dating of old sites 2012 university of washington published by elsevier inc all rights reserved

century long average time intervals between earthquake ruptures of the san andreas fault in the carrizo plain california paleoseismological data constrain the age location and associated magnitude of past surface rupturing earthquakes these are critical parameters for developing and testing fault behavior models and characterizing seismic hazard we present new earthquake evidence and radiocarbon analyses that refi ne the chronology of the six most recent earthquakes that ruptured the south central san andreas fault in the carrizo plain california united states at the bidart fan site modeled 95 percentile ranges of the earthquakes prior to the a d 1857 earthquake are a d 1631 1823 1580 1640 1510 1612 1450 1475 and 1360 1452 the average time interval between the last six earthquakes that ruptured the san andreas fault in the carrizo plain is 88 41 yr this is less than the time since the most recent a d 1857 earthquake less than all reported average intervals of prehistoric earthquakes along the entire san andreas fault and signifi cantly shorter than the 235 yr average used in recent seismic hazard evaluations the new chronological data combined with recent slip studies imply that the magnitudes of the earthquakes that ruptured the southern san andreas fault in the carrizo plain since ca a d 1360 were variable and suggest that the widely held view of rare but great surface rupturing earthquakes along this portion of the southern san andreas fault should be reevaluated 118

new u series dates at the caune de l arago france abstract in the beginning of the 1980s the caune de l arago was the focus of an interdisciplinary effort to establish the chronology of the homo heidelbergensis preneandertals fossils using a variety of techniques on bones and on speleothems the result was a very large spread of dates particularly on bone samples amid the large spread of results some radiometric data on speleothems showed a convergence in agreement with inferences from faunal studies we present new u series results on the stalagmitic formation located at the bottom of unit iv at the base of the upper stratigraphic complex samples and splits were collaboratively analyzed in the four different laboratories with excellent interlaboratory agreement results show the complex sequence of this stalagmitic formation the most ancient part is systematically at internal isotopic equilibrium 350 ka suggesting growth during or before isotopic stage 9 representing a minimum age for the human remains found in unit iii of the middle stratigraphical complex which is stratigraphically under the basis of the studied stalagmitic formation overlaying parts of the speleothem date to the beginning of marine isotope stages 7 and 5

slip along the san andreas fault associated with the great 1857 earthquake historical records indicate that several meters of lateral slip along the san andreas fault accompanied the great 1857 earthquake in central and southern california these records together with dendrochronological evidence suggest that the rupture occurred along 360 to 400 km of the fault including several tens of kilometers of the currently creeping reach in central california geomorphic expressions of late holocene right lateral offsets are abundant along the 1857 rupture along 300 kilometers of the 1857 rupture between cholame and wrightwood the youngest discernible offset ranges from 3 to 9 1 2 meters dormancy of the fault since 1857 almost certainly indicates that this latest offset was created in 1857 fault slip apparently associated with the 1857 earthquake varies in a broadly systematic way along the trace of the fault it is relatively uniform along each of several long segments but changes rather abruptly in value between these segments this nonuniform displacement pattern may imply that some segments of the fault rupture more frequently or experience a slower long term slip rate than others the 1857 offsets indicate a seismic moment m o between 5 3 and 8 7 10 27 dyne cm assuming a 10 to 15 km depth of rupture and relatively uniform slip as a function of depth a comparison with the rupture length average slip value and tectonic setting of the california earthquake of 1906 m s 8 1 4 indicates a value of m 8 1 4 for the 1857 event

uranium series isochron dating at el castillo cave cantabria spain the acheulean mousterian question abstract a massive flowstone layer level 23 near the base of the stratigraphic sequence in el castillo cave cantabria spain is dated by the uranium series isochron method to 89 11 10 ka bp the flowstone separates cultural layers traditionally labelled mousterian above and acheulean below the date reported here in association with other recent age determinations for mousterian and acheulean artifact assemblages in western europe calls into question the temporal significance of these archaeological designations in addition it further underlies the importance of the castillo cultural sequence and allows tentative discussion of changing rates of sedimentation in the vestibule of the cave where some 18 m of cultural and geological deposits were laid down during the course of the upper pleistocene

paleoenvironmental context of the early neanderthals of poggetti vecchi for the late middle pleistocene of central italy work on thermal pools at poggetti vecchi in grosseto italy exposed an up to 3 meter thick succession of seven sedimentary units unit 2 in the lower portion of the succession contained vertebrate bones mostly of the straight tusked elephant palaeoloxodon antiquus commingled with stone bone and wooden tools thermal carbonates overlying unit 2 are radiometrically dated to the latter part of the middle pleistocene this time span indicates that early neanderthals produced the human artifacts from poggetti vecchi the elephant bones belong to seven individuals of different ages sedimentary facies analysis and paleoecological evidence suggest a narrow lacustrine palustrine embayment affected by water level fluctuations and at times by hydrothermal water cyclic lake level variations were predominantly forced by the rapid climatic fluctuations that occurred at marine isotope stage mis 6 7 transition and throughout the mis 6 possibly an abrupt intense and protracted cold episode during the onset of mis 6 led to the sudden death of the elephants which formed an unexpected food resource for the humans of the area the poggetti vecchi site adds new information on the behavioral plasticity and food procurement strategies that early neanderthals were able to develop in italy during the middle to the late pleistocene transition

high resolution interseismic velocity data along the san andreas fault from gps and insar 1 we compared four interseismic velocity models of the san andreas fault based on gps observations the standard deviations of the predicted secular velocity from the four models are larger north of the san francisco bay area near the creeping segment in central california and along the san jacinto fault and the east california shear zone in southern california a coherence spectrum analysis of the secular velocity fields indicates relatively high correlation among the four models at longer wavelengths 15 40 km with lower correlation at shorter wavelengths to improve the short wavelength accuracy of the interseismic velocity model we integrated interferometric synthetic aperture radar insar observations initially from advanced land observing satellite alos ascending data spanning from the middle of 2006 to the end of 2010 totaling more than 1100 interferograms with gps observations using a sum remove filter restore approach the final insar line of sight data match the point gps observations with a mean absolute deviation of 1 5 mm yr we systematically evaluated the fault creep rates along major faults of the san andreas fault and compared them with creepmeters and alignment array data compiled in uniform california earthquake rupture forecast version 2 ucerf2 moreover this insar line of sight dataset can constrain rapid velocity gradients near the faults which are critical for understanding the along strike variations in stress accumulation rate and associated earthquake hazard

latest pleistocene and holocene slip rate for the san bernardino strand of the san andreas fault plunge creek southern california implications for strain partitioning within the southern san andreas fault system for the last 35 k y an alluvial succession on the northeast side of the san bernardino strand of the san andreas fault includes distinctive aggradational and degradational features that can be matched with correlative features on the southwest side of the fault key among these are 1 a terrace riser on the northeast side of the fault that correlates with an offset channel wall on the southwest side of the fault and forms a basis for slip estimates for the period ca 35 ka to the present and 2 a small alluvial fan on the southwest side of the fault that has been matched with its most likely source gullies on the northeast side of the fault and forms a basis for slip estimates for the last 10 5 k y slip rate estimates for these two separate intervals are nearly identical the rate for the older feature is most likely between 8 3 and 14 5 mm yr with a 95 confidence interval of 7 0 15 7 mm yr the rate for the younger feature is most likely between 6 8 and 16 3 mm yr with a 95 confidence interval of 6 3 18 5 mm yr these rates are only half the previously published slip rate for the san andreas fault 35 km to the northwest in cajon pass a rate that traditionally is extrapolated southeastward along the san bernardino section of the fault results from plunge creek suggest that about half of the 25 mm yr rate at cajon pass transfers southeastward to the san jacinto fault as proposed by other workers on the basis of regional geologic relations these results indicate that the discrepancy between latest quaternary slip rates and present day rates of strain accumulation across the san bernardino section of the san andreas fault from geodesy can be largely explained by slip transfer between faults leading to spatial variation in rate along the san andreas fault nonetheless the latest pleistocene and holocene slip rate at plunge creek is still somewhat faster than rates inferred for the san bernardino section of the san andreas fault based on elastic block modeling of geodetic data and may be more appropriate than those rates for hazard estimation

promotion of chemical weathering by higher plants field observations on hawaiian basalts abstract an electron microprobe and petrographic microscope were used to study the biota rock interface beneath higher plant communities and lichens as well as unvegetated surfaces on hawaiian basalt flows ranging from a few years to several thousand years in age and currently receiving moderate to extremely high annual rainfall we find dramatic order of magnitude minimum acceleration of weathering rates beneath vascular plants on the youngest flows relative to adjacent non or primitively vegetated controls notably rocks colonized by the common fruticose lichen stereocaulon uulcani bulk dissolution of plagioclase accounts for most of the weathering observed beneath higher plants on these young basalts analysis of older flows under mature forests reveals that chemical weathering beneath vascular plant communities continues unabated for thousands of years after initial colonization moreover such weathering is not limited to exterior basalt surfaces but is commonly found adjacent to joints and vesicles within the rock where it is often associated with fine sub 2 mm diameter plant roots plagioclase dissolution was also observed on lichen encrusted and unvegetated flows a few hundred to thousands of years in age but it was typically much less advanced than beneath higher plants and rarely extended more than several millimeters from exterior rock surfaces chemical denudation rates on older flows with higher plants are at minimum ten times greater than those with only lichens or microbiota in the environments studied if s uulcani and associated microflora resemble the terrestrial precursors to vascular plant communities then the results of studies such as this have implications for the history of atmospheric co 2 and the earth s climate

geomorphology and vegetation on hillslopes interactions dependencies and feedback loops article i nfo the linkages between vegetation and hillslope geomorphology have been the subject of serious study for years but traditionally ecologists and geomorphologists have viewed these interactions as unidirectional on the one hand botanists and landscape ecologists have examined the effects of hillslope features processes and materials on vegetation structure composition and dynamics focus has been placed on the effects of topography elevation slope angle slope aspect edaphic factors rock type and geomorphic disturbance mass movement snow avalanches land surface erosion on the other hand geomorphologists have traditionally treated vegetation as an independent variable that affects landforms and sediment routing at limited spatial temporal scales hillslope vegetation and landforms however co evolve one key is to understand the role of time disturbances and feedbacks that link vegetation and geomorphology on hillslopes the effects of vegetation on mass movement and landscape evolution are being studied in new ways many regional studies claim that vegetation becomes less relevant as one moves to larger and larger watershed scales but ecoregion analysis offers a contrasting view whereas these efforts have produced vehicles of understanding that are simple ordered unified and harmonious they often do not reflect the complexity that leads to multiple possible outcomes place dependent results recent perspectives focus on the two way interplay between vegetation and hillslope geomorphology where establishing cause and effect linkages is made difficult by confounding factors spatial temporal scale location convergence divergence nonlinearity thresholds feedbacks vegetation and geomorphology interactions are controlled by a combination of global factors independent of time and place and the local environmental history continued refinement of fine scale deterministic models should be encouraged but the ability to translate these results to larger scales needs to be explored at large scales future research especially those with predictive modeling as the goal should concentrate on how to increase the generality of concepts and models and should seek to reduce the number of variables and factors considered

new esr u series dates in yabrudian and amudian layers at qesem cave israel abstract qesem cave is a middle pleistocene site situated 12 km east of the mediterranean coast of tel aviv israel it is attributed to the acheuleo yabrudian cultural complex aycc of the late lower paleolithic period dated to ca 420 200 ka this site exhibits a unique prehistoric sequence where the amudian blade dominated industry is the main cultural component however the scraper dominated yabrudian industry is also represented in distinct contexts at the cave the chronology established by tl applied on burnt flints esr u series on herbivorous teeth and u series on spelothems suggests that qesem cave is one of the oldest sites yielding such a blade industry and a fully fledged trajectory of quina scrapers production this work presents new esr u series dates on four animal teeth unearthed from an amudian central hearth recently published and four other teeth from a yabrudian industry bearing layer in the shelf area the dates range from 249 to 296 ka for the amudian hearth mean age of 280 ka and from 279 to 382 ka for the yabrudian layer mean age of 313 ka these radiometric dates provide new information on the chronology of the amudian and yabrudian industries in the hearth and shelf areas and contribute towards a better understanding of the chronology of qesem cave as a whole this is the first time we have direct dates from amudian and yabrudian context from a single site

paleoseismic evidence of clustered earthquakes on the san andreas fault in the carrizo plain california exposures we have excavated across the san andreas fault contradict the hypothesis that part of the fault in the carrizo plain is unusually strong and experiences relatively infrequent rupture the exposures record evidence of at least seven surface rupturing earthquakes which have been approximately dated by accelerated mass spectrometry radiocarbon analysis of detrital charcoal and buried in situ plants five large earthquakes have occurred since 1218 a d the most recent earthquake event a was the 1857 fort tejon earthquake which we have associated with 6 6 10 m of dextral slip along the main fault trace the penultimate earthquake event b most likely occurred within the period a d 1405 1510 slip from either events b and c combined or from event b alone totals 7 11 m three earthquakes events c d and e occurred in a temporal cluster prior to event b and after approximately a d 1218 the average recurrence interval within this cluster is 73 116 years depending on assumptions events f and g occurred after 200 years b c a depositional hiatus between events e and f may hide evidence of additional earthquakes events b and d within the carrizo cluster of a d 1218 1510 may correlate with events t a d 1329 1363 and v a d 1465 1495 at pallett creek on the mojave segment of the fault this suggests two fault ruptures similar in length to that of 1857 events c and e apparently did not rupture the mojave section which suggests that the carrizo segment has ruptured independently or in combination with segments to the north irregular repeat times of large earthquakes suggest a pattern of clustered events at the end of seismic supercycles

open system modelling for u series and esr dating of teeth abstract the study of the constituents of teeth dentine and enamel by a combination of esr and u series techniques offer unique constraints on the history of uranium migration into these materials our results imply that it is inappropriate to assume a simplified u uptake model for neither the components of a single tooth nor for the faunal remains of a given site however the combination of both methods may provide a new technique for establishing reliable chronologies for archaeological quaternary sites of up to several hundred thousand years

six similar sequential ruptures of the san andreas fault carrizo plain california we document the precise sizes but not the dates of the six latest offsets across the san andreas fault at wallace creek california three and perhaps four of these including the latest in 1857 show dextral offset of 7 5 8 m the third and fourth offsets however are just 1 4 and 5 2 m the predominance of similar offsets for the latest six events suggests that the fundamental properties of the fault system that control slip size do not vary greatly from event to event the large offsets imply that ruptures involving this site are typically more than 200 km long

the challenge of dating early pleistocene fossil teeth by the combined uranium series electron spin resonance method the venta micena palaeontological site orce spain the palaeontological site of venta micena orce andalusia spain lies in the eastern sector of the guadix baza basin one of the best documented areas in europe for plio pleistocene biostratigraphy the combination of biochronological and palaeomagnetic results combined with the radiometric data obtained for atapuerca sima del elefante indicated that the venta micena stratum was formed between the jaramillo and olduvai palaeomagnetic events most likely between 1 22 and 1 77 ma five fossil teeth from two outcrops sites a and b were selected to assess the potential of combined uranium series electron spin resonance us esr dating of early pleistocene sites although the us esr results of the first outcrop showed a large scatter between the three teeth the mean age of 1 37 0 24 ma can be considered a reasonable age estimate for venta micena the mean esr age of 0 62 0 03 ma obtained for site b seems to be a severe underestimation when compared with the independent age control this underestimation is attributed to a relative recent u mobilization event that led to some u leaching the results show that any esr age calculations of old samples are extremely sensitive to variations in the measured 230th 234u ratios in dental tissues although the results demonstrate that esr can in principle be applied to early pleistocene sites they also reveal the complexity of dating such old teeth it is necessary to continue research in several directions such as study of the behaviour of esr signals in old teeth and understanding recent u mobilization processes to improve the reliability of the combined us esr dating method applied to early pleistocene times a period for which the number of available numerical dating techniques is very limited copyright 2011 john wiley sons ltd

present tectonic motion across the coast ranges and san andreas fault system in central california geodetic results from very long baseline interferometry vlbi satellite laser ranging slr and the global positioning system gps are used to estimate angular velocities between the sierran microplate pacific plate and north american plate the sierra pacific pole of rotation lies nearer to the san andreas fault than does the pacific north america pole of rotation and leads to different tectonic implications than if the latter is used the angular velocities show that the san andreas fault system and central california coast ranges accommodate motion of 39 2 mm yr mainly by strike slip faulting all confidence limits following signs in this paper are 95 confidence limits fault normal motion is small is mainly convergent at rates up to 3 3 1 0 mm yr and varies along the coast but is divergent at 2 6 1 2 mm yr across san pablo bay and associated topographic lows across which the sierran and central valley watershed drains to the pacific ocean the mountain ranges tend to be larger where the fault normal convergence rates are larger the low convergence rate 0 5 1 8 mm yr normal to the san andreas fault in the carrizo plain differs sharply from that previously inferred 8 2 1 2 mm yr and 4 9 1 6 mm yr by feigl et al 1993 the difference is due to differences between their and our elastic strain accumulation models and between how their and our pacific plate reference frames are defined the ranges in most places require a minimum of 4 2 1 m y of fault normal convergence at the present rate to attain their present cross sectional area if erosion is neglected more if it is not the amount of convergence previously estimated from a balanced cross section across the diablo range in central california requires 10 8 3 m y of convergence at the present rate the former is consistent with widely held views about the onset of the coast range orogeny but the latter is not both are consistent however with the recent plate reconstructions by s cande j stock and colleagues which indicate that pacific plate motion relative to north america changed to a more convergent direction 20 25 clockwise of its prior direction at ca 8 to 6 ma and not at 3 5 ma as had been previously inferred the inferred change in direction of plate motion is large compared with the present angle of convergence across the straight and narrow segment of the san andreas fault of 0 7 4 7 from which we infer that the sierran microplate changed motion relative to north america at the same time ca 8 to 6 ma as did the pacific plate we further infer that the motion accommodated across the great basin must also have changed at the same time we also examine the hypothesis that stable sliding occurs along the san andreas fault and other northwest striking strike slip faults in central california where the fault normal convergence rate is low or negative and that these faults are unstable where the fault normal convergence rate is high such a relationship appears to hold in general but fails in detail in particular there are substantial sections of fault with small inferred rates of fault normal convergence across which the san andreas fault is locked moreover the creeping section of the san andreas fault i e the section between parkfield and the calaveras junction is the locus of greater fault normal convergence 3 2 1 4 mm yr than is the locked part of the fault 0 5 1 8 mm yr south of parkfield thus this hypothesis is at best a partial explanation for the observed distribution of locked and nonlocked sections of the fault

slip rates and off fault deformation in southern california inferred from gps data and models 1 in southern california fault slip rate estimates along the san andreas fault saf and garlock fault from geodetically constrained kinematic models are systematically at the low end or lower than geologic slip rate estimates the sum of geodetic model slip rates across the eastern california shear zone is higher than the geologic sum however the ranges of reported model and geologic slip rate estimates in the literature are sufficiently large that it remains unclear whether these apparent discrepancies are real or attributable to epistemic uncertainties in the two types of estimates we further examine uncertainties in geodetically derived slip rate estimates on major faults in southern california by conducting a suite of inversions with four kinematic models long term rigid elastic block models constrained by the geologic slip rates cannot fit the present day gps derived velocity field deforming permanent off fault strain elastic block models and viscoelastic earthquake cycle block models constrained by geologic slip rates can fit the present day gps derived velocity field with 28 33 of the total geodetic moment rate occurring as distributed deformation off of the major faults models incorporating viscoelastic mantle flow predict systematically higher slip rates than purely elastic models on many of the major southern california faults with ranges of elastic viscoelastic 29 34 30 37 mm yr for the carrizo saf segment 20 24 20 32 mm yr for the mojave saf segment 14 17 18 22 mm yr for the coachella saf segment 13 19 14 22 mm yr for the san jacinto fault and 5 11 5 11 mm yr for the western garlock fault

weathering and vegetation effects in early stages of soil formation abstract bedrock surfaces in the ouachita mountains arkansas exposed by spillway construction and which had not previously been subjected to surface weathering environments developed 15 20 cm thick soil covers in less than three decades all open bedrock joints showed evidence of weathering and biological activity rock surfaces and fragments also showed evidence of significant weathering alteration the results suggest a soil production function whereby weathering and increases in thickness are initially rapid the rapid initial rate 5 to 10 mm year 1 is facilitated by a weathering favorable regional climate local topography favoring moisture and sediment accumulation and aggressive vegetation colonization the ages of the trees on the bedrock benches suggests that a short period

the stampede tephra a middle pleistocene marker bed in glacial and eolian deposits of central alaska a deformed block of silt incorporated in a push moraine of the lignite creek drift of the nenana river valley in central alaska contains the 10 cm thick stampede tephra the silt block and tephra are folded sheared and cut by multiple fault planes and appear to have been entrained by a glacier and deformed by glaciotectonic processes while frozen the stampede tephra is also found in a paleosol preserved within a sequence of eolian sediments near the tanana river some 175 km to the northeast allowing direct tephrochronologic correlations between the depositional record of quaternary glaciations in the alaska range and eolian sediments in unglaciated central alaska the lignite creek drift predates deposits of the late wisconsin riley creek and penultimate healy glaciations but postdates the stampede tephra indicating that it dates to the middle quaternary and is not part of the tertiary nenana gravel formation