paleomagnetic secular variation at the azores during the last 3 ka 1 we report on 33 new paleomagnetic directions obtained from 16 lava flows emplaced in the last 3 ka on sao miguel the largest island of the azores the data provide 27 well dated directions from historical or 14c dated flows which together with 6 directions previously gathered from the same flows by johnson et al 1998 yield the first paleomagnetic directional record of the last 3 ka from the atlantic ocean within flow directions are consistent suggesting that inclination swings from 60 to 25 and declination changes between 10 to 20 reflect variations in the geomagnetic field over the last 3 ka to a first approximation the declination record is consistent with predictions from cals3k 4 and gufm1 global field models conversely inclination values are lower than model predictions at two different ages 1 four sites from the 1652 ad flow yield i 48 instead of i 63 predicted by gufm1 2 data from several flows nicely mimic the inclination minimum of 800 1400 ad but inclination values are lower by 10 than cals3k 4 model predictions by interpolating a cubic spline fit on declination inclination versus age data we tentatively infer the directional evolution of the geomagnetic field at the azores from 1000 bc to 1600 ad the obtained curve shows three tracks in virtual overlap during the 1000 800 bc 800 500 bc and 400 700 ad time spans

sea level change along the italian coast during the holocene and projections for the future published and new sea level data are used to provide projections of sea level change in italy for the year 2100 by adding new isostatic and tectonic component to the ipcc and rahmstorf projections comparison of the observations from more than 130 sites with different geomorphological and archaeological sea level markers with the predicted sea level curves provides estimates of the vertical tectonic contribution to the relative sea level change the results are based on the most recent anu model for the ice sheets of both hemispheres including an alpine deglaciation model on the basis of the eustatic tectonic and isostatic components to the sea level change projections are provided for marine inundation scenarios for the italian coastal plains for the year 2100 that today are at elevations close to current sea level

complex multiple cosmogenic nuclide concentration and histories in the arid rio lluta catchment northern chile terrestrial cosmogenic nuclide tcn concentrations measured in river sediments can be used to estimate catchment wide denudation rates by investigating multiple tcn the steadiness of sediment generation transport and depositional processes can be tested measurements of 10be 21ne and 26al from the hyper to semi arid rio lluta catchment northern chile yield average single denudation rates ranging from 12 to 75 m myr 1 throughout the catchment paired nuclide analysis reveals complex exposure histories for most of the samples and thus the single nuclide estimates do not exclusively represent catchment wide denudation rates the lower range of single nuclide denudation rates 12 17 m myr 1 established with the noble gas 21ne is in accordance with palaeodenudation rates derived from 21ne 10be and 26al 10be ratio analysis since this denudation rate range is measured throughout the system it is suggested that a headwater signal is transported downstream but modulated by a complex admixture of sediment that has been stored and buried at proximal hillslope or terrace deposits which are released during high discharge events that is best evidenced by the stable nuclide 21ne which preserves the nuclide concentration even during storage intervals the catchment wide single 21ne denudation rates and the palaeodenuation rates contrast with previous tcn derived erosion rates from bedrock exposures at hillslope interfluves by being at least one order of magnitude higher especially in the lower river course these results support earlier studies that identified a coupling of erosional processes in the western cordillera contrasting with decoupled processes in the western escarpment and in the coastal cordillera copyright 2008 john wiley sons ltd

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

palaeomagnetic dating of two recent lava flows from ceboruco volcano western mexico ing j escalante supported studies with the micromag agfm and the curie balance and e nava warranted the functionality of the laboratory computers and the network this work was supported by unam project in 112712 hb and fjpc and conacyt grant no 180032 hb and anm fjpc has received funding from the european union s horizon 2020 research and innovation programme under the marie sklodowskacurie grant agreement no 659901

global cooling initiated stony deserts in central australia 2 4 ma dated by cosmogenic 21ne 10be stony deserts are durable indicators of aridity but until now have not been directly dated using 21ne and 10be produced in surface rocks by cosmic rays we show that australian stony deserts formed 2 4 ma at the time when global cooling initiated the quaternary ice ages and intensified aridity induced major landscape changes in central australia this is the first direct determination of stony desert ages using a new method for determining cosmogenic 21ne in the presence of various neon components from other sources

effects of bedrock landslides on cosmogenically determined erosion rates abstract the successful quantification of long term erosion rates underpins our understanding of landscape formation the topographic evolution of mountain ranges and the mass balance within active orogens the measurement of in situ produced cosmogenic radionuclides crns in fluvial and alluvial sediments is perhaps the method with the greatest ability to provide such long term erosion rates although deep seated bedrock landsliding is an important erosional process in active orogens its effect on crn derived erosion rates is largely unquantified we present a numerical simulation of cosmogenic nuclide production and distribution in landslide dominated catchments to address the effect of bedrock landsliding on erosion rates results of the simulation indicate that the temporal stability of erosion rates determined from crn concentrations in sediment decreases with increased ratios of landsliding to bedrock weathering rates within a given catchment area and that as the frequency of landsliding increases larger catchment areas must be sampled in order to accurately evaluate long term erosion rates in addition results of this simulation suggest that sediment sampling for crns is the appropriate method for determining long term erosion rates in regions dominated by mass wasting processes whereas bedrock surface sampling for crns may generally underestimate long term erosion rates response times of crn concentrations to changes in erosion rate indicate that climatically driven cycles of erosion may be detected but that complete equilibration of crn concentrations to new erosional conditions may take tens of thousands of years comparison of simulated crn derived erosion rates with a new data set of such rates from the nepalese himalaya underscore the conclusions drawn from the model results

australian desert dune fields initiated with pliocene pleistocene global climatic shift development of continental aridity has been linked to late cenozoic global cooling but the evidence is indirect based on terrestrial loess deposits and eolian silt in marine sediments whereas direct dating of the inception of arid landforms has been frustrated by a lack of suitable methods here we report the first age determination of a major arid zone dune field based on cosmogenic 10 be and 26 al measurements of drill cores from dunes in the simpson desert central australia results show that the dune field began to form ca 1 ma whereas dating using quartz optically stimulated luminescence indicates episodic dune building during late quaternary ice ages less intense desertification began earlier the previous cosmogenic exposure dating showed that neighboring stony deserts began to form at the onset of quaternary ice ages 2 4 ma aridity deepened and the dune field formed when ice age cycles increased their amplitude and switched their periods from 40 k y to 100 k y ca 1 ma

large scale erosion rates from in situ produced cosmogenic nuclides in european river sediments abstract we have calculated long term erosion rates of 20 100 mm kyr from quartz contained 10be in the bedload of middle european rivers for catchments ranging from 102 to 105 km2 these rates average over 10 40 kyr and agree broadly with rock uplift incision and exhumation rates historic soil erosion rates and erosion rates calculated from the measured sediment loads of the same rivers moreover our new erosion rate estimates correlate well with lithology and relief however in the regen neckar loire and meuse catchments cosmogenic nuclide derived erosion rates are consistently 1 5 4 times greater than the equivalent rates derived from measured river loads this may be due to the systematic under representation of high magnitude low frequency transport events in the gauging records which cover less than a century alternatively the discrepancy may derive from spatially non uniform erosion and preferential tapping of deeper sections of the irradiation profile a third explanation relates the high cosmogenic nuclide derived erosion rates to inheritance of an elevated pleistocene erosion signal uncertainties associated with the cosmogenic nuclide derived erosion rate estimates are not greater than the potential errors in conventional estimates therefore the cosmogenic nuclide approach is an effective tool for rapid catchment wide assessment of time integrated rates of bedrock weathering and erosion and we anticipate its fruitful application to the quaternary sedimentary record

paleomagnetic correlation of late quaternary lava flows in the lower east rift zone of kilauea volcano hawaii paleomagnetic data reflecting paleosecular variation psv of the geomagnetic field are used to correlate individual lava flows in the lower east rift zone of kilauea volcano this area has been recently mapped based on petrography stratigraphy soil development and degree of weathering of the flows eight 14c dates also provide a framework for the relative age assignments site mean directions of remanent magnetization for historic flows in this region indicate that local magnetic anomalies do not mask the psv signal that within flow angular differences are generally 5 and that temporal resolution of the paleomagnetic directions is of the order of 100 years the paleomagnetic correlations do not conflict with the observed stratigraphic relationships and psv reference curves from dated lava flows and lake sediments have also been used to help determine the sequence of directional groups paleomagnetic grouping of flows into eruptive events indicates a different and perhaps more refined eruptive history for the lower east rift zone than implied by the geologic mapping alone the number of individual flows based on petrographic distinctions is likely the same but the frequency of events including petrographically distinct flows is apparently lower than previously thought flows from ridge crest vents bifurcated by the rift indicate formation of the central graben in this region after 300 years ago possibly related to the 1790 eruptions along dual fractures

scale dependence of lithological control on topography bedrock channel geometry and catchment morphometry in western scotland abstract we propose that a scale dependent topographic signature of erodibility arises due to fluvial and glacial erosion acting on different parts of the landscape at different times for 14 catchments in western scotland we define three levels of substrate erodibility in order of decreasing resistance quartzite rocks nonquartzite rocks and zones of fault related fracture then using digital topographic and planimetric data coupled with field measurements we identify regression based scaling relationships between substrate erodibility and morphometric parameters at two spatial scales catchment scale morphometry shows a weak to variable relationship with substrate metrics overall erodibility can be inferred from catchment steepness indices i e channel steepness index and relief ratio but the existence of multiple exceptions could confound a more general application of this approach nonetheless major valley troughs trace fault zones and nonquartzite rocks leaving much of the higher and stee

the mt moio eruption etna stratigraphy petrochemistry and 40ar 39ar age determination with inferences on the relationship between structural setting and magma intrusion abstract mt moio is the most peripheral scoria cone of etna volcano and rises above the peloritani mountains sedimentary basement 18 km north of the volcano summit geological and tephrostratigraphic studies and 40ar 39ar age determinations were used to characterize the eruption and constrain its occurrence to 29 ka ago during the activity of the ellittico volcano the volcanic edifice active before the actual one the mongibello volcano the mt moio eruption formed a large scoria cone and a widespread tephra fallout deposit indicating that vigorous explosive activity produced an eruptive plume minor effusive activity produced a small lava flow at the end of the eruption geochemical data indicate that the composition of erupted magma became less evolved during the eruption mugearite basalt hawaiite thus mt moio deposits have been divided into lower and upper sequences characterized by similar depositional facies based on the classification of etna flank eruptions available in the literature mt moio can be classed as an eccentric sensu rittmann and class b eruption historic flank eruptions e g 1669 1763 2001 2002 03 formed deposits that are petrochemically and stratigraphically similar to those of mt moio the general trend of the mt moio eruptive fissure corresponds to that of extensional neotectonic lineaments in the apenninic maghrebian chain indicating that the structure of the basement played a role in controlling the ascent of the volatile rich magma during ellittico volcano activity

late quaternary landscape evolution in the keep river region northwestern australia abstract this paper evaluates the late quaternary chronostratigraphic context of archaeological sites in the keep river region northern territory australia cosmogenic dating luminescence dating and sediment characterisation reveal sedimentary processes commencing from erosion of the escarpment and plateaux source through temporary storage in sand sheets to final deposition in alluvial floodplains erosion of the sandstone plateaux 5 mm ka 1 and escarpment faces probably 50 100 mm ka 1 provide the main sediment source for the adjacent sand sheets which have evolved over the past 100 000 years as the product of ongoing cycles of accumulation and denudation the rate of sediment accumulation is lowest near the escarpments on the low energy sediment limited sand sheets 1 and greatest near the main streams 400 mm ka 1 that have more numerous sediment sources collectively luminescence ages indicate an apparent increase in sediment accumulation rate in the sand sheets from 100 mm ka 1 in the late pleistocene to over 200 mm ka 1 in the holocene this most likely reflects enhanced monsoonal activity following postglacial marine transgression palaeosol horizons in the creek profile distinguished by sediment mottling mark potentially significant palaeoenvironmental and palaeoclimatic changes during the quaternary

palaeomagnetic refinement of the eruption ages of holocene lava flows and implications for the eruptive history of the tongariro volcanic centre new zealand

10be constrains the sediment sources and sediment yields to the great barrier reef from the tropical barron river catchment queensland australia abstract estimates of long term background sediment generation rates place current and future sediment fluxes to the great barrier reef in context without reliable estimates of sediment generation rates and without identification of the sources of sediment delivered to the reef prior to european settlement c 1850 determining the necessity and effectiveness of contemporary landscape management efforts is difficult here using the 2100 km 2 barron river catchment in queensland australia as a test case we use in situ produced 10 be to derive sediment generation rate estimates and use in situ and meteoric 10 be to identify the source of that sediment which enters the coral sea near cairns previous model based calculations suggested that background sediment yields were up to an order of magnitude lower than contemporary sediment yields in contrast in situ 10 be data indicate that background 43 t km 2 y 1 and contemporary sediment yields 45 t km 2 y 1 for the barron river are similar these data suggest that the reef became established in a sediment flux similar to what it receives today since western agricultural practices increased erosion rates large amounts of sediment mobilized from hillslopes during the last century are probably stored in queensland catchments and will eventually be transported to the coast most likely in flows triggered by rare but powerful tropical cyclones that were more common before european settlement and may increase in strength as climate change warms the south pacific ocean in situ and meteoric 10 be concentrations of coral sea beach sand near cairns are similar to those in rivers on the atherton tablelands suggesting that most sediment is derived from the extensive low gradient uplands rather than the steep more rapidly eroding but beach proximal escarpment

eroding australia rates and processes from bega valley to arnhem land we report erosion rates determined from in situ produced cosmogenic 10 be across a spectrum of australian climatic zones from the soil mantled se australian escarpment through semi arid bedrock ranges of southern and central australia to soil mantled ridges at a monsoonal tropical site near the arnhem escarpment climate has a major effect on the balance between erosion and transport and also on erosion rate the highest rates averaging 35 m ma 21 were from soil mantled transport limited spurs in the humid temperate region around the base of the se escarpment the lowest averaging about 1 5 m ma 21 were from the steep weathering limited rocky slopes of kings canyon and mt sonder in semi arid central australia between these extremes other factors come into play including rock type slope and recruitment of vegetation we measured intermediate average erosion rates from rocky slopes in the semi arid flinders and macdonnell ranges and from soil mantled sites at both semi arid tyler pass in central australia and the tropical monsoonal site at soil mantled sites in both the se and tropical north soil production generally declines exponentially with increasing soil thickness although at the tropical site this relationship does not persist under thin soil thicknesses and the relationship here is humped results from tyler pass show uniform soil thicknesses and soil production rates of about 6 5 m ma 21 supporting a longstanding hypothesis that equilibrium soil mantled hillslopes erode in concert with stream incision and form convex up spurs of constant curvature moreover weathering limited slopes and spurs also occur in the same region the average erosion rate for rocky sandstone spurs at glen helen is 7 m ma 21 similar to the tyler pass soil mantled slopes whereas the average rate for high quartzite spurs at mount sonder is 1 8 m ma 21 the extremely low rates measured across bedrock dominated landscapes suggest that the ridge valley topography observed today is likely to have been shaped as long ago as the late miocene these rates and processes quantified across different undisturbed landscapes provide critical data for landscape evolution models

the large and destructive 1669 ad eruption at etna volcano reconstruction of the lava flow field evolution and effusion rate trend the 1669 ad flank eruption was the most destructive event on etna volcano in historical times 700 bc and provided because of the presence of numerous quarries and subsurface data the opportunity for a unique case study in which we directly measured the thickness of the lava field moreover analysis of historical documents allowed reconstruction of the temporal evolution of the lava field and estimation of the average effusion rate one hundred and thirty eight thickness measurements acquired from field surveys and subsurface data allowed us to divide the lava field into 12 zones of homogenous mean thickness and to calculate a total lava volume of 607 105 106 m3 corresponding to an average effusion rate of 58 10 m3 s this new volume differs by 24 up to 64 from previously published values the temporal evolution of the cumulative volume and average effusion rate were reconstructed for the first fourteen days from field data and analysis of historical records a short initial phase was characterized by a rapid increase in effusion rate which reached a peak of 640 m3 s after 3 days this was followed by a longer phase in which the flow rate decreased the first 14 days were crucial for the development of the lava field and in this time it covered 72 of its final area and produced most of the damage thereafter the growth of a complex lava tube network promoted lava field lengthening to the city of catania 17 km away from the vent effusion rate trends like those of the 1669 eruption can be adopted for future investigations aimed at assessing the effects of similar events on etna s most highly urbanized area and at other effusive basaltic volcanoes

deflection of paleomagnetic directions due to magnetization of the underlying terrain in the summers of 1989 and 1991 we made 344 near ground level measurements of the ambient geomagnetic field above recent basalts on the island of hawaii using a three component fluxgate magnetometer we studied 12 surface features including a lava pond lava channels long tilted blocks smooth sloping surfaces two fissures and a deep u shaped road cut we observed substantial differences up to 20 between the observed and expected international geomagnetic reference field igrf magnetic field directions over these features except those composed of shelly pahoehoe and a flat horizontally thin lava pond we also observed inclinations that were systematically shallower than the igrf field by up to 5 we show that these shallower inclinations can be explained by the magnetization of the regionally sloping surface of the southern side of the island we found that all of the observed inclination deflections can be explained by simple two dimensional models which assume uniform induced and remanent magnetization parameters in the local terrain our observations imply that the inclination deflections cannot be corrected without a complete knowledge of the preexisting terrain and the remanence in the underlying flows upon which the lavas cooled since this information is rarely available it is difficult or impossible to discriminate between dispersion of paleomagnetic directions caused by the magnetic terrain effect and dispersion due to other factors such as paleosecular variation psv we therefore conclude that psv dispersion parameters cannot be accurately determined from paleomagnetic measurements on highly magnetic volcanic flows we also suggest that some of the geomagnetic excursions inferred from measurements on volcanic rocks may be at least in part due to the magnetic terrain effect it is unnecessary to invoke ad hoc mechanisms such as clastic block or crustal rotations distortion of the top crust or flow deformation to explain the large between site dispersions or inclination anomalies observed in many of the paleomagnetic data from volcanic rocks our observations also bring into question the general reliability of paleomagnetic pole positions inferred from volcanic rocks as a systematic inclination deflection due to local and regional slopes and irregular terrain such as those we observed would lead to a corresponding error in the inferred paleolatitude the magnetic terrain effects also offer alternative explanations for anomalous paleomagnetically inferred plate motions

an example of river pattern evolution produced during the lateral growth of a central polygenic volcano the case of the alcantara river system mt etna italy abstract analysis of numerous geognostic soundings and geophysical investigation data indicates the presence of a wide depression identifiable as the ancient valley of the alcantara river below the northern flank of mt etna surface and subsurface data were used to reconstruct the complex stratigraphic succession filling the paleo alcantara valley consisting of superimposed lava flows interlayered with thick lentiform clastic bodies the evolution of the alcantara river system was defined with reference to the different phases of growth of mt etna the first correlation between volcanic activity and the drainage system refers to the initial phases of alkaline volcanism 170 100 ka during this period the southern watershed of the paleo alcantara valley acted as a morphological barrier to the products of the various volcanoes which gradually grew in the sector now occupied by the valle del bove the paleo alcantara riverbed was sporadically invaded by lava flows generated by peripheral activity of the central edifice a radical modification of the hydrographic pattern of the region began about 45 40 ka as a consequence of the growth of the ellittico volcano the main eruptive centre of the etnean edifice the gradual expansion of this volcano led over a period between about 30 and 25 ka to the northward deviation of the paleo alcantara riverbed the consequent erosion of a section of the watershed with the adjacent hydrographic basin of the paleo s paolo river resulted in the capture of the latter from then on the hydrographic pattern of the area gradually took on the characteristics it has today a water circulation system developed within the thick volcanic pile filling the paleo alcantara valley with the formation of an aquifer which is today one of the most important hydro structures of the whole volcanic edifice and is in part exploited in the eastern side of sicily

the humped soil production function eroding arnhem land australia we report erosion rates and processes determined from in situ produced beryllium 10 10be and aluminum 26 26al across a soil mantled landscape of arnhem land northern australia soil production rates peak under a soil thickness of about 35 cm and we observe no soil thicknesses between exposed bedrock and this thickness these results thus quantify a well defined humped soil production function in contrast to functions reported for other landscapes we compare this function to a previously reported exponential decline of soil production rates with increasing soil thickness across the passive margin exposed in the bega valley south eastern australia and found remarkable similarities in rates the critical difference in this work was that the arnhem land landscapes were either bedrock or mantled with soils greater than about 35 cm deep with peak soil production rates of about 20 m ma under 35 40 cm of soil thus supporting previous theory and modeling results for a humped soil production function we also show how coupling point specific with catchment averaged erosion rate measurements lead to a better understanding of landscape denudation specifically we report a nested sampling scheme where we quantify average erosion rates from the first order upland catchments to the main sixth order channel of tin camp creek the low 5 m ma rates from the main channel sediments reflect contributions from the slowly eroding stony highlands while the channels draining our study area reflect local soil production rates 10 m ma off the rocky ridge 20 m ma from the soil mantled regions quantifying such rates and processes help determine spatial variations of soil thickness as well as helping to predict the sustainability of the earth s soil resource under different erosional regimes copyright 2009 john wiley sons ltd

paleomagnetic dating of the most recent silicic eruptive activity at pantelleria strait of sicily we report on the paleomagnetism of ten sites in the products of the most recent silicic eruptive cycle of pantelleria strait of sicily previously radiometrically dated at 5 10 ka our comparison with proxies for geomagnetic field directions allows us to narrow considerably the time window during which these eruptions occurred the strongly peralkaline composition causes the magmas to have low viscosities locally resulting in strong agglutina tion of proximal fall deposits this allows successful extraction of paleomagnetic directions from the explosive phases of eruptions one of our sites was located in the serra della fastuca fall deposit produced by the first explosive event of the eruptive cycle the other nine sites were located in the most recent explosive pumice fall and agglutinate from cuddia del gallo and cuddia randazzo and effusive khaggiar lava products the very similar paleomagnetic directions gathered from eight internally consistent sites were compared to reference geomagnetic field directions of the last 5 10 ka directions from cuddia del gallo agglutinate and khaggiar flows translate into 5 9 to 6 2 ka ages whereas the fastuca pumices yield a slightly older age of 6 2 6 8 ka hence the most recent silicic eruptive cycle lasted at most a millennium and as little as a few centuries around 6 0 ka paleomagnetically inferred ages are in good agreement with published and calibrated by us 14 c dates from paleosols charcoals sampled below the studied volcanic units whereas k ar data are more scattered and yield 30 older ages our data show that the time elapsed since the most recent silicic eruptions at pantelleria is comparable to the quiescence period separat ing the two latest volcanic cycles

feedbacks among climate erosion and tectonics in a critical wedge orogen the interactions among climate erosion and tectonics have long been of interest to geologists but have not yet been united into a single theoretical framework in this study representations of orographic precipitation and fluvial erosion are combined with the concept of a critical wedge orogen the idealized framework captures the basic system dynamics it also allows for a formal analysis of the precipitation and tectonic interactions in terms of feedback factors and gains and so permits a quantitative comparison of their relative strengths the constraint of self similar growth in a critical wedge orogen acts as a tectonic governor whereby changes in orogen size are strongly damped we determine that this negative tectonic feedback is stronger than the precipitation feedback which may be negative or positive depending on whether precipitation increases or decreases with orogen size for an extreme positive feedback unconstrained runaway growth is possible ultimately leading to plateau formation when orographic precipitation leads to a significant rain shadow there is a strong partitioning of rock uplift rates that favors the wet windward flank of the orogen this flank also dominates the response of the whole orogen to changes in climate or tectonic forcing except in the case where a large fraction of the eroded material is recycled into the wedge finally it is demonstrated that the response time of the orogen depends on the feedbacks and is proportional to the gain of the system

dilution of 10be in detrital quartz by earthquake induced landslides implications for determining denudation rates and potential to provide insights into landslide sediment dynamics the concentration of 10be in detrital quartz 10beqtz from river sediments is now widely used to quantify catchment wide denudation rates but may also be sensitive to inputs from bedrock landslides that deliver sediment with low 10beqtz major landslide triggering events can provide large amounts of low concentration material to rivers in mountain catchments but changes in river sediment 10beqtz due to such events have not yet been measured directly here we examine the impact of widespread landslides triggered by the 2008 wenchuan earthquake on 10beqtz in sediment samples from the min jiang river basin in sichuan china landslide deposit material associated with the wenchuan earthquake has consistently lower 10beqtz than in river sediment prior to the earthquake river sediment 10beqtz decreased significantly following the earthquake downstream of areas of high coseismic landslide occurrence i e with greater than 0 3 of the upstream catchment area affected by landslides because of input of the 10be depleted landslide material but showed no systematic changes where landslide occurrence was low changes in river sediment 10beqtz concentration were largest in small first order catchments but were still significant in large river basins with areas of 104 105 km2104 105 km2 spatial and temporal variability in river sediment 10beqtz has important implications for inferring representative denudation rates in tectonically active landslide dominated environments even in large basins although the dilution of 10beqtz in river sediment by landslide inputs may complicate interpretation of denudation rates it also may provide a possible opportunity to track the transport of landslide sediment the associated uncertainties are large but in the wenchuan case calculations based on 10be mixing proportions suggest that river sediment fluxes in the 2 3 years following the earthquake increased by a similar order of magnitude in the 0 25 1 mm and the 0 25 mm size fractions as determined from 10beqtz mixing calculations and hydrological gauging respectively such information could provide new insight into sediment transfer with implications for secondary sediment related hazards and for understanding the removal of mass from mountains

numerical and analytical models of cosmogenic radionuclide dynamics in landslide dominated drainage basins 1 in many tectonically active regions on earth landslides dominate sediment delivery to channels while cosmogenic radionuclides crn represent a valuable tool to document basin averaged erosion rates a better understanding of crn dynamics in these systems is required before erosion rates can be reliably inferred from crn concentrations the stochastic nature of landslides results in variability of crn concentrations in both alluvial and hillslope samples that is both difficult to document and poorly understood to guide sampling strategies we developed a 2 d plan view model to simulate the influence of landslides on crn dynamics we employ a sediment mixing model in which concentrations of crns from material eroded by both landslides and steady processes are combined to evaluate how best to infer erosion rates from crn concentrations this model is further used to test a new analytical solution for the distribution of crn concentrations on hillslopes in a landslide prone system results suggest that for landscapes dominated by deep 5 m landslides only large drainage basins 100 km2 provide consistently reliable estimates of erosion rates from crn concentrations for landscapes dominated by shallow landslides 0 7 2 m smaller basins can produce reliable estimates results further suggest that the distribution of concentrations from hillslope samples could be used to deduce the relative contribution of material derived from landslide and steady processes these findings underscore the need to consider carefully the sources of natural variability in sampling and analyzing crns if properly done the variability can reveal useful information about geomorphic processes in landslide prone areas

fossil cosmogenic 3 he record from k ar dated basaltic flows of mount etna volcano sicily 38 n evaluation of a new paleoaltimeter this study investigates the reliability of a paleoaltimeter based on the elevation dependency of the cosmogenic nuclides production rate the proposed method relies on fossil cosmogenic record indeed measuring the cosmogenic nuclide concentration in an exposed and then buried lava flow combined with an independent estimate by k ar or 40ar 39ar dating of the past exposure duration theoretically allows recording fossil cosmogenic production rates which can thus be converted in paleoelevations this approach was tested by measuring cosmogenic 3he 3hec in olivines and clinopyroxenes of quaternary k ar dated basaltic flows of mount etna volcano sicily 38 n the agreement within uncertainties 1 500 m between current and cosmogenic derived elevations demonstrates the paleoaltimeter reliability however dating imprecision earth s paleomagnetic fluctuations and erosion contemporary to the flow exposure are parameters that may affect the accuracy and the precision of the method on older geological scales their respective influences were thus carefully evaluated and discussed to conclude that the paleoaltimeter can potentially reach resolutions better than 1000 m even for cenozoic records

new and revised palaeomagnetic secular variation records from post glacial volcanic materials in new zealand abstract global databases suffer from a paucity of palaeomagnetic secular variation psv data from the sw pacific region and are often affected by inconsistencies in data quality or available age control of the sampled units here we present new psv records obtained from post glacial 15 kyrs bp volcanic materials mainly lavas from new zealand the new dataset incorporates a compilation and critical assessment of all previous discrete psv data and their age controls and the results of new sampling in the taupo volcanic zone the overall dataset includes 23 directional and 10 absolute palaeointensity records primarily from lavas of rhyolitic or andesitic composition age constraints on the rhyolitic lavas are available from correlation with distal radiocarbon dated tephra deposits age controls on the andesites from field relationships or from 40 ar 39 ar dating directional swings ranging from 326 5 to 26 0 declination and 81 4 to 46 3 inclination and intensity variations from 37 0 to 71 6 t fall well into the range of psv expected for this time frame in new zealand and reproduce features of continuous sediment records

a 30 000 year record of extreme floods in tropical australia from relict plunge pool deposits implications for future climate change relict plunge pool sedimentary sequences provide much longer paleoflood records than normally provided by slackwater deposits and other previously reported paleoflood sedimentary signatures the only two relict plunge pool sedimentary sequences so far reported lie 300 km apart in tropical northern australia and provide a record of extreme floods for the last 30 000 years each of these sequences identify the early to mid holocene and the period immediately prior to the last glacial maximum as the two periods of greatest flood magnitudes of the late quaternary flood discharges at these times were up to five times greater than any floods experienced over the last 4 000 years most climate models predict that the magnitude and frequency of storms and rainfall events will increase under a warmer greenhouse climate the plunge pool sedimentary sequences however show that periods of greatly enhanced discharge compared to present can be associated with both warm wet and cool wet phases of climate

strong rocks sustain ancient postorogenic topography in southern africa the cape mountains of southern africa exhibit an alpine like topography in conjunction with some of the lowest denudation rates in the world this presents an exception to the often cited coupling of topography and denudation rates and suggests that steep slopes alone are not sufficient to incite the high denudation rates with which they are commonly associated within the cape mountains slope angles are often in excess of 30 degrees and relief frequently exceeds 1 km yet be 10 based catchment averaged denudation rates vary between 2 32 0 29 m m y and 7 95 0 90 m m y we attribute the maintenance of rugged topography and suppression of denudation rates primarily to the presence of physically robust and chemically inert quartzites that constitute the backbone of the mountains be 10 based bedrock denudation rates on the interfluves of the mountains vary between 1 98 0 23 m m y and 4 61 0 53 m m y the close agreement between the rates of catchment averaged and interfluve denudation indicates topography in steady state these low denudation rates in conjunction with the suggestion of geomorphic stability are in agreement with the low denudation rates 20 m m y estimated for southern africa during the late cenozoic by means of cosmogenic nuclide thermochronology and offshore sedimentation analyses accumulatively these data suggest that the coastal hinterland of the subcontinent may have experienced relative tectonic stability throughout the cenozoic

erosion of an ancient mountain range the great smoky mountains north carolina and tennessee analysis of 10be and 26al in bedrock n 10 colluvium n 5 including grain size splits and alluvial sediments n 59 including grain size splits coupled with field observations and gis analysis suggest that erosion rates in the great smoky mountains are controlled by subsurface bedrock erosion and diffusive slope processes the results indicate rapid alluvial transport minimal alluvial storage and suggest that most of the cosmogenic nuclide inventory in sediments is accumulated while they are eroding from bedrock and traveling down hill slopes spatially homogeneous erosion rates of 25 30 mm ky 1 are calculated throughout the great smoky mountains using measured concentrations of cosmogenic 10be and 26al in quartz separated from alluvial sediment 10be and 26al concentrations in sediments collected from headwater tributaries that have no upstream samples n 18 are consistent with an average erosion rate of 28 8 mm ky 1 similar to that of the outlet rivers n 16 24 6 mm ky 1 which carry most of the sediment out of the mountain range grain size specific analysis of 6 alluvial sediment samples shows higher nuclide concentrations in smaller grain sizes than in larger ones the difference in concentrations arises from the large elevation distribution of the source of the smaller grains compared with the narrow and relatively low source elevation of the large grains large sandstone clasts disaggregate into sand size grains rapidly during weathering and downslope transport thus only clasts from the lower parts of slopes reach the streams 26al 10be ratios do not suggest significant burial periods for our samples however alluvial samples have lower 26al 10be ratios than bedrock and colluvial samples a trend consistent with a longer integrated cosmic ray exposure history that includes periods of burial during down slope transport the results confirm some of the basic ideas embedded in davis geographic cycle model such as the reduction of relief through slope processes and of hack s dynamic equilibrium model such as the similarity of erosion rates across different lithologies comparing cosmogenic nuclide data with other measured and calculated erosion rates for the appalachians we conclude that rates of erosion integrated over varying time periods from decades to a hundred million years are similar the result of equilibrium between erosion and isostatic uplift in the southern appalachian mountains

magnetic anomalies of lava fields in the canary islands possible consequences for paleomagnetic records abstract measurements of the total magnetic field have been performed above the surface of 12 lava flows in the canary islands of la palma and tenerife directions can differ by up to 15 and intensity changes reach 20 the mean flow directions do not coincide and the mean flow virtual dipole moments vdms differ by more than 10 the deviations are linked to topographic features at the surface of the flows and should persist during emplacement of the next overlying flow such effects can thus limit the resolution of paleomagnetic records of detailed geomagnetic features and the field intensity variations above the flows and between the mean flow values could explain a significant part of the scatter inherent to many paleointensity studies historical field variations have been recorded from the same flows and are in agreement with the european curve for the same period however there is also some correlation with the present field which suggest that the underlying magnetized bodies could have affected the paleomagnetic records biases induced by the crustal field would increase considerably during periods of reduced field intensity like during reversals and induce erroneous records samplings performed over large distances within each lava flow would provide the best way to average out the contribution of the anomalies in any case such effects should not be neglected in paleomagnetic studies

refining the holocene eruptive activity at tenerife canary islands the contribution of palaeomagnetism abstract the timing of the holocene volcanic activity of tenerife canary islands is poorly constrained and the volcanological framework for this area is still incomplete most of the eruptions are dated only by a single 14c dating or the ages are simply stratigraphically determined we apply palaeomagnetism increasingly used in the last years to date holocene volcanism to improve the knowledge of tenerife volcanic history we report on the palaeomagnetic dating using the sha dif 14k global model of nine holocene eruptions that produced scoria cones and major lava flows and we compare our results with those previously obtained by 14c method four of the studied eruptions were previously dated by 14c four were stratigraphically constrained and one was never dated so far concerning the first group for boca cangrejo and mna reventada eruptions palaeomagnetic and 14c ages agree while for the others we obtained older or younger ages than radiocarbon data for the second group one or more age ranges smaller than stratigraphic intervals were found finally we provided the first dating 790 723 bce of the mna grande eruption we confirm that palaeomagnetism can be considered an excellent complement to the radiocarbon method because it is applicable on volcanics with nearly all compositions and provides higher resolution dating at least where reliable geomagnetic reference curves are available the improved framework of the holocene volcanic activity of tenerife shows alternating periods characterized by low and high eruptive frequencies with the last 3 kyr characterized by high eruptive frequency and dominated by basaltic eruptions

10be derived denudation rates from the burdekin catchment the largest contributor of sediment to the great barrier reef abstract terrestrial cosmogenic nuclides tcns such as beryllium 10 10be are now routinely used to reconstruct erosional rates over tens of thousands of years at increasingly large basin scales 100 000 km2 in australia however the approach and its assumptions have not been systematically tested within a single large drainage basin this study measures 10be concentrations in river sediments from the burdekin catchment one of australia s largest coastal catchments to determine long term 10 000 years time integrated rates of sediment generation and denudation a nested sampling design was used to test for effects of increasing catchment scale on nuclide concentrations with upstream catchment areas ranging from 4 to 130 000 km2 beryllium 10 concentrations in sediment samples collected from the upstream headwater tributaries and mid stream locations range from 1 8 to 2 89 105 atoms g 1 and data confirm that nuclide concentrations are well and rapidly mixed downstream sediment from the same tributaries consistently yielded 10be concentrations in the range of their upstream samples overall no decrease in 10be concentrations can be observed at the range of catchment scales measured here the mean denudation rate for all river sediment samples throughout the fanning subcatchment 1100 km2 is 18 47 m ma 1 which compares with the estimate at the end of the burdekin catchment 130 000 km2 of 16 22 m ma 1 nuclide concentrations in the lower gradient western and southern catchments show a higher degree of variability and several complications emerged as a result of the contrasting geomorphic processes and settings this study confirms the ability of tcns to determine long term denudation rates in australia and highlights some important considerations in the model assumptions that may affect the accuracy of limited sampling in large low gradient catchments with long storage times

constraining age and volume of lava flow invasions of the alcantara valley etna volcano italy new insights from paleomagnetic dating and 3d magnetic modeling abstract the alcantara river marks the northern border of etna volcano and along its ne sector it forms a narrow nw se elongated valley that is carved in the mts peloritani sedimentary sequences the valley has been invaded by several lava flows during the growth of the main bulk of the stratovolcano edifice in the past 60 ky ellittico and mongibello volcanoes in this paper we have constrained the age of the main lava flows forming the valley floor and reconstructed the length and volume of the main lava flow that impacted this area through a multidisciplinary approach integrating stratigraphic and aeromagnetic data analysis together with new paleomagnetic and 14c dating the new age determinations showed that the evolution of the present day geological and hydrographic setting of the valley was mainly conditioned by a few flank eruptions that occurred in the lower n flank of etna during the activity of the mongibello volcano in particular between 13 9 and 9 7 ka bp the valley floor was filled by the so called alcantara lava flow for its entire length up to the river mouth reaching a maximum length of about 24 km later two other flank eruptions producing the so called mt dolce and solicchiata lava flows occurred at 9 1 7 2 and 7 3 7 2 ka bp respectively covering the eruptive fissure and the proximal portion of the alcantara lava field and generated the most recent northward shift of the riverbed finally 3d magnetic modeling allowed us to calculate the total on and off shore volume of the alcantara lava flow as 1 km3 a value comparable to those of the long lasting historical eruptions of etna conversely the 24 km length reached by this lava flow is anomalously high when compared to lava flows of the past 15 ky likely because its emplacement occurred within the valley floor preventing any possibility of lateral expansion

bedrock bedding landsliding and erosional budgets in the central european alps we explore the controls of the litho tectonic architecture on the erosional flux in the 370 km2 glogn basin european alps in this basin the bedding and schistosity of the bedrock dip parallel to the topographic slope on the nw valley flank leading to a non dip slope situation on the opposite se valley side while the dip slope condition has promoted the occurrence of landslides e g the c 30 km2 deep seated lumnezia landslide the opposite non dip slope side of the valley hosts 100 m deeply incised tributary streams 10be concentrations of stream sediments yield catchment averaged denudation rates that vary between 0 27 0 03 and 2 19 0 37 mm a 1 while the spatially averaged denudation rate of the entire basin is 1 99 0 34 mm a 1 our 10be based approach reveals that the lumnezia landslide front contributes c 30 65 of the entire sediment budget although it covers 5 of the glogn basin this suggests a primary control of the bedrock bedding on erosion rates and processes

production of cosmogenic radionuclides at great depth a multi element approach abstract for the last two decades in situ produced cosmogenic nuclides are increasingly applied in earth sciences to quantify surface processes in parallel significant reduction of the analytical uncertainties linked to advances in accelerator mass spectrometry ams allows more precise measurements however among all the published works on cosmogenic nuclides only few studies are dedicated to a better understanding of their production systematic or to a better constrain of the physical parameters involved in their production thus an approach to investigate in situ produced cosmogenic nuclides 10 be 26 al and 36 cl along a single 11 meter long core drilled from the surface and composed of carbonates and quartzose conglomerates has been launched these measurements have been used to quantify muon induced productions based on natural samples for each studied nuclide contrary to the current most oftenly used calculation of muon induced production parameters which are based on irradiation experiments at discrete energies productions based on natural samples are considering the entire energy range of particles reaching the ground surface the evolution of 36 cl concentrations with depth needs to agree with those parameters deduced from 10 be and 26 al data this is optimized when considering a fast muon induced 36 cl production contribution and a spallation production rate at sea level high latitude slhl of 42 0 2 0 atoms 36 cl g ca 1 a 1 1 sigma uncertainty

quantifying denudation rates and sediment storage on the eastern altiplano bolivia using cosmogenic 10be 26al and in situ 14c abstract denudation processes and sediment transfer are investigated in a high elevation low relief environment eastern altiplano bolivia using 10be 26al and in situ 14c analysis in fluvial sediments concentrations of the long lived nuclides 10be and 26al yield consistently low catchment wide denudation rates of 3 29 mm ky 1 integrating over 21 194 ky which reflect the low geomorphic gradients and the discontinuity of fluvial transport along the eastern altiplano margin no significant correlation is recorded between denudation rates of individual catchments and morphological basin parameters slope area elevation this is attributed to the overall little variability in morphology the agreement between the denudation rates and published modern sediment discharge data suggests steady landscape evolution of the eastern altiplano from the latest pleistocene until today while 10be and 26al provide long term estimates on sediment production in situ cosmogenic 14c is used to trace short term sediment storage in situ 14c concentrations are comparatively low indicating that 14c decayed during alluvial storage over at least the past 11 20 ky we assume storage at shallow depth 2 m and consider the influence of soil mantled hillslopes on the in situ 14c concentration our results illustrate the importance of sediment storage even over short distances and demonstrate the potential of in situ 14c to study sediment routing and transfer times within drainage systems however this study also demonstrates that the long lived 10be and 26al nuclides can provide adequate estimates on long term denudation rates even if sediment transport is not fast but interrupted by several thousands of years of storage

scaling factors for the rates of production of cosmogenic nuclides for geometric shielding and attenuation at depth on sloped surfaces abstract the decrease in rates of production of cosmogenic nuclides occurs because of shielding of cosmic rays by mountains sloped surfaces and local rock formations that block them when a large part of the sky is blocked this correction is large and requires detailed model calculations this paper considers three geometries a rectangular obstruction a triangular obstruction and a sloped surface other geometries can be considered as a combination of these the results are presented in terms of formulas and graphs so that the reader can easily apply them to common field situations any use of cosmogenic nuclides in the study of geomorphic processes or forms must consider factors that introduce variations in the production of nuclides

a matlab tool for archaeomagnetic dating a matlab tool for archaeomagnetic dating has been developed in this work well dated palaeosecular variation curves psvcs can be used to date archaeological artefacts with unknown ages the archaeomagnetic direction declination and or inclination and the archaeointensity obtained from the archaeological artefact are compared with a master psvc in addition historical lava flows with controversial ages can be dated using this methodology the dating process follows the descriptions given by lanos 2004 which is based on the combination of temporal probability density functions of the three geomagnetic field elements here we develop an interactive tool in matlab code to carry out archaeomagnetic dating by comparing the undated archaeomagnetic or lava flow data with a master psvc the master psvcs included with the matlab tool are the different european bayesian curves and those generated using both regional and global geomagnetic field models a case study using all the psvcs available in europe and some undated archaeomagnetic data has been carried out to analyze how the different psvcs affect the dating process in addition the dating uncertainty and the relocation error have been analyzed in the european region results show that some regional bayesian psvcs and the regional scha dif 3k archaeomagnetic model are the best choices to obtain an accurate date in europe moreover when it is available the full geomagnetic field vector must be used for archaeomagnetic dating

paleomagnetic secular variation at vulcano aeolian islands during the last 135 kyr abstract paleosecular variation psv of the earth s magnetic field during the last 135 kyr has been investigated in lavas scoriae and pyroclastic rocks of vulcano aeolian islands about 1000 samples have been collected at 77 sites from 25 distinct volcanic units whose age is either known from published isotopical data or constrained on the grounds of statigraphical relationships magnetic mineralogy investigation shows that ti magnetite is the main ferromagnetic mineral at most sites secondary magnetization components are either absent or easily removed by stepwise thermal or alternating field demagnetization the mean site direction of the characteristic remanent magnetization is usually well defined since the semi angle of confidence is greater than 5 at only four sites the mean paleomagnetic direction over the last 135 kyr d 9 4 i 53 2 95 3 5 differs from the geocentric axial dipole gad at vulcano d 0 i 57 8 and might be interpreted as the effect of a long term non axial dipolar component the psv record from vulcano agrees well with those from the lacustrine sediments of lago grande di monticchio 100 kyr bp and lago di mezzano 30 kyr bp located in the italian peninsula brandt et al quat sci rev 18 1999 961 976 the inclination anomaly i found at vulcano corresponds to about half of the shallowing observed in the sediments of the two lakes and the declination anomaly d may be used to tie the declination values derived from azimuthally unoriented cores to the geographical reference system in order to find the optimum site to be used as reference for psv studies in italy the angular values of the earth s magnetic field measured at the 113 repeat stations of the italian geomagnetic network coticchia et al boll geod sci aff 40 2001 277 291 have been analyzed with the relocation via pole method noel and batt geophys j int 102 1990 753 756 the viterbo station lat 42 27 n long 12 02 e proved the best since the mean error is 0 3 for both declination and inclination wherever the original psv site is located in italy a preliminary composite psv curve for the last 30 kyr bp is thus proposed merging and relocating to viterbo the data from vulcano and the curve from lago di mezzano corrected for the gad deviation found at vulcano

a geomagnetic field model for the holocene based on archaeomagnetic and lava flow data abstract we propose a new geomagnetic field model for the holocene period based on archaeomagnetic and lava flow data avoiding the use of lake sediment data the source of data comes from the geomagia50v2 database which has been updated with the new archaeomagnetic and volcanic studies published during the last 3 yr the model called sha dif 14k allows us to analyse the behaviour of the geomagnetic field for the last 14 000 yr from 12 000 bc to 1900 ad for the model construction we use the spherical harmonic analysis in space and the penalized cubic b splines in time both spatial and temporal regularization norms are used to constrain the inversion problem and applied at the core mantle boundary cmb to assure the convergence of the model for the last 3 ka the model predictions agree with those given by the global model arch3k 1 and the european model scha dif 3k for older epochs the new model presents a clear improvement in field resolution with respect to other current models of the geomagnetic field for the holocene for the last 9 ka the time evolution of the dipolar moment obtained from the dipole field shows a clear minimum between 5500 bc and 3000 bc and the well known continuous decreasing trend of the geomagnetic field strength for the last millennium and a half a general view of the time average evolution of the geomagnetic field flux lobes at the cmb for the northern hemisphere suggests a marked lobe of positive magnetic flux when the dipole moment was maximum this lobe vanishes when the dipolar field is decreasing the north polar wander paths of both north magnetic dip and geomagnetic poles were obtained showing an average rate of motion of 5 1 km yr and 3 7 km yr respectively the model shows that the geomagnetic field can be averaged as axial dipolar in 2000 yr within an error of 5 the typical uncertainty of the palaeomagnetic studies finally and following the recent definition of archaeomagnetic jerks we found 8 critical events in the time evolution of the geomagnetic field for the last 8 ka characterized by a maximum in the hemispheric asymmetry of the proposed model the model is available in the earth ref digital archive at http earthref org erda 1897

denudation rates determined from the accumulation of in situ produced 10be in the luquillo experimental forest puerto rico we present a simple method for estimation of long term mean denudation rates using in situ produced cosmogenic 10be in fluvial sediments procedures are discussed to account for the effects of soil bioturbation mass wasting and attenuation of cosmic rays by biomass and by local topography our analyses of 10be in quartz from bedrock outcrops soils mass wasting sites and riverine sediment from the icacos river basin in the luquillo experimental forest puerto rico are used to characterize denudation for major landform elements in that basin the 10be concentration of a discharge weighted average of size classes of river sediment corresponds to a long term average denudation of 43 m ma 1 consistent with mass balance results

geomagnetic secular variation in historical lavas from the canary islands summary the age of historical lava flows on the canary islands can be traced back at least to 1585 ad during the last 400 years eruptions occurred at fairly regular intervals the palaeomagnetic directions of these lavas record the ambient field direction with high precision so that an historical secular variation curve svc can be constructed for the canaries which closely resembles the curve registered at paris the svc can be used as a dating tool for historical eruptions of unknown age and can probably be extended into the last 4000 5000 yr of recent volcanic activity on the canaries

wearing down wearing back and gorge extension in the long term denudation of a highland mass quantitative evidence from the shoalhaven catchment southeast australia the long standing issue of the dominance of scarp retreat versus summit lowering in the denudation of a highland mass is investigated with supporting evidence provided by tertiary basalts throughout the shoalhaven catchment in southeast australia both of these forms of denudation are found to be insignificant compared to the role of fluvial gorge extension over the last 30 m y headward advancement of the shoalhaven gorge has been occurring at approximately 15 times the rate of major escarpment retreat 250 times the average rate of summit lowering and over 500 times the rate of interfluve consumption these estimates show that the headward erosion of gorges is the most important process denuding the highlands in the shoalhaven region and possibly elsewhere in the highlands of eastern australia over the long term the highlands in this region will become considerably more dissected well before they decrease substantially in height or are narrowed this conclusion has important implications for models p

flood flipped boulders in situ cosmogenic nuclide modeling of flood deposits in the monsoon tropics of australia during the quaternary extreme floods along the durack river in the kimberley northern australia dislodged transported and stacked massive meter sized boulders from the underlying bedrock channel floor field evidence identified a population of the boulders to have been overturned after detachment we measured in situ cosmogenic 10 be and 26 al concentrations in six imbricated boulders to constrain the timing of flood events we present a simple numerical model that simultaneously solves the expressions for the predicted nuclide concentrations from the exposed and hidden surfaces of a flipped boulder to calculate the time since it was overturned the ability of the model to unequivocally discern whether a boulder was overturned depends on boulder thickness and the site specific steady state erosion rate of the six boulders sampled our model successfully determined four finite flip ages whereas the other two boulders indicated steady state and were either not flipped or flipped sufficiently long ago for the nuclide profile to have returned to steady state while the two older model ages ca 150 ka and ca 260 ka are strongly sensitive to assumptions made for the local erosion rate correction the two younger flip ages 5 6 1 0 ka and 10 3 1 9 ka are robust against such corrections early to mid holocene major floods have been recorded in other parts of northern australia we suggest that similar holocene floods occurred in the kimberley and that such extreme events may have been widespread in northern australia in the late quaternary our boulder flip model can be applicable to similar deposits associated with other extreme events such as paleo tsunamis

geomagnetic field variations as a dating tool application to sicilian lavas abstract over 40 historically dated mt etna lava flows have been carefully sampled for the purpose of palaeomagnetic analysis the natural remanent magnetization nrm of each lava flow contains a record of both the magnitude and direction of the earth s magnetic field at the time of its eruption our analysis has thus enabled us to determine the change of the magnetic field in sicily through historic times and to construct curves which show this secular variation of the field in both direction and magnitude in this paper the curves are used to reconsider the historical dates attributed to a number of etna lavas dates which had since been questioned by recent palaeomagnetic and geological studies in a similar manner these secular variation curves can be used as a powerful archaeological dating tool by comparison with the nrm of fired artifacts

dating sediment burial with in situ produced cosmogenic nuclides theory techniques and limitations abstract dating sediment burial over million year time scales is crucial in many areas of the earth sciences and archeology but is often difficult using traditional techniques sediment burial can be dated by the radioactive decay of cosmogenic nuclides provided that the sediment was exposed to cosmic rays prior to burial dating calculations are straightforward if sediment is buried deeply and rapidly enough to prevent cosmogenic nuclide production after burial however the analysis can be complicated by postburial production if sediment is insufficiently shielded from secondary cosmic ray nucleons and muons this paper discusses how buried sediments can be dated over timescales up to 5 myr using 26 al and 10 be in quartz

quantitative resolution of the debate over antiquity of the central australian landscape implications for the tectonic and geomorphic stability of cratonic interiors we report the first measure of long 100 myr and short 1 myr term denudation rates from key geologically stable landforms in the davenport range central australia these landforms have previously been assigned a cambrian age which arguably places them amongst the oldest persistent landforms on the continent if not on earth our results from combined apatite fission track thermochronology and in situ cosmogenic radionuclide analyses using 10 be and 26 al show that while average exhumation rates are low the denudation history for this cratonic region is incompatible with extreme sub aerial longevity and long term tectonic and geomorphic stability our revised model for the landscape evolution of this region is consistent with one of maximum burial prior to and during the mesozoic followed by a phase of kilometre scale exhumation that was largely complete by the beginning of the cainozoic we suggest that a similar process of burial and exhumation has probably been responsible for the sub aerial preservation of seemingly ancient landforms elsewhere in australia

the morphostructural setting of mount etna sedimentary basement italy implications for the geometry and volume of the volcano and its flank instability abstract the reinterpretation of more than 2500 subsurface data consisting of geoelectric and borehole prospecting undertaken at mount etna allows reconstructing the contour map of the sedimentary basement this reconstruction highlights a complex asymmetric topography due to the inhomogeneous long term updoming of the region and the interrelationship between the development of the drainage network and flank instability these different processes have produced a major morphological difference between the eastern sector characterised by a 17 km wide horseshoe shaped depression and the other flanks formed by palaeovalleys the origin of the wide horseshoe shaped depression can be attributed to the large scale flank instability processes involving the entire continental margin in the etna offshore this depression of the etna basement was generated by a series of coalescent landslides before the beginning of the eruptive activity of the timpe phase more than 220 ka ago this wide depression is the main cause of the flank instability that produced the gravitational slope failures of the valle del bove about 10 ka ago regarding mt etna s geometry we have estimated a total volume of about 532 km 3 that was emplaced during the past 330 ka resulting in an average rate of volcanic output of 0 0016 km 3 a the reconstruction of the temporal variation of the average eruptive rate highlights a drastic increase of volcanism during the last 100 ka in response to the gradual stabilization of the plumbing system in the etna region that led to the build up of the composite stratovolcano structure the data presented in this paper represent the state of knowledge of the sedimentary basement of etna which can be used for future studies aimed at developing a detailed understanding of the deep structure of the volcano s unstable flanks

geological and geomorphological evolution of the etna volcano ne flank and relationships between lava flow invasions and erosional processes in the alcantara valley italy abstract in this paper the interrelationships between volcanic activity and fluvial events in the alcantara valley are investigated based on the correlation between the stratigraphy of the ne flank of mt etna and subsurface data the geological and geomorphological evolutions of the valley are reconstructed new 1 10 000 scale geological mapping shows that the bulk of this sector of the volcano is made up of the ellittico volcano lava flows though they are widely covered by the products of the eruptive activity of the last 15 ka the present day morphological setting of the alcantara valley is the result of two main evolutionary phases initiated during the activity of the ellittico volcano only one lava flow invasion of the valley floor occurred in the first phase this phenomenon was followed by a long period of erosional processes leading to the entrenchment of the drainage pattern and the erosion of the ellittico lava flow about 20 25 ka ago an important change in the frequency of the lava flow invasions into the valley occurred associated with the final stage of the ellittico volcano activity marking the beginning of the second phase during this phase volcanic processes became predominant with respect to other morphogenetic processes in the alcantara valley lava flows coming from the ne flank of the ellittico volcano caused a radical modification of the morphological setting of this area even though only one lava flow emitted by an eruptive fissure located within the valley partially filled the riverbed during the eruptive activity of the last 15 ka the complete filling of the alcantara valley floor occurred in particular between 15 and 7 ka a lava flow originated from the mt moio scoria cone filled the valley floor for a distance of about 9 km following a short period of erosion an eruptive fissure located within the valley generated a 20 21 km long lava flow that was channelled along the full extent of the alcantara valley and stretches for about 3 km offshore in the ionian sea in the last 7 ka lava flows originating from the ne rift zone produced only temporary damming of the riverbed without any important contribution to the filling of the alcantara valley

continental margin large scale instability controlling the flank sliding of etna volcano abstract etna volcano is affected by a downward sliding of its eastern flank as rapid as a few cm year whose nature is highly debated recently collected marine geological and geophysical data allows a detailed image of the morphostructural setting of the continental margin facing the volcano here a large bulge offsets the margin that is deeply affected by widespread semicircular steps interpreted as evidence of large scale gravitational instability such features permeate the whole margin and extend inshore to the volcano sector where the larger ground deformations are measured both submarine instability and subaerial flank sliding are bounded by two regional tectonic lineaments interpreted as weakness lines these cross the coastline to accommodate the basinward movement of this large sector of the continental margin topped by the etna volcanic pile the new data allows re interpreting the tectonic setting of the coastal belt and proposing a novel structural model highlighting the active role of the continental margin instability to drive the seaward sliding of the volcano s eastern flank this model may suggest why a very active basaltic volcano has so unusually developed in front of an active thrust belt

correlation of welded ignimbrites on pantelleria strait of sicily using paleomagnetism although the oldest volcanic rocks exposed at pantelleria strait of sicily are older than 300 ka most of the island is covered by the 45 50 ka green tuff ignimbrite thought to be related to the cinque denti caldera and younger lavas and scoria cones pre 50 ka rocks predominantly rheomorphic ignimbrites are exposed at isolated sea cliffs and their stratigraphy and chronology are not completely resolved based on volcanic stratigraphy and k ar dating it has been proposed that the older la vecchia caldera is related to ignimbrite q 114 ka and that ignimbrites f d and z 106 94 and 79 ka respectively were erupted after caldera formation we report here the paleomagnetic directions obtained from 23 sites in ignimbrite p 133 ka and four younger ignimbrites and from an uncorrelated and loosely dated welded lithic breccia thought to record a caldera forming eruption the paleosecular variation of the geomagnetic field recorded by ignimbrites is used as correlative tool with an estimated time resolution in the order of 100 years we find that ignimbrites d and z correspond in good agreement with recent ar ar ages constraining the d z eruption to 87 ka the welded lithic breccia correlates with a thinner breccia lying just below ignimbrite p at another locality implying that collapse of the la vecchia caldera took place at 130 160 ka this caldera was subsequently buried by ignimbrites p q f and d z paleomagnetic data also show that the northern caldera margin underwent a 10 west northwest outwards tilting after emplacement of ignimbrite p possibly recording magma resurgence in the crust

high resolution aeromagnetic anomaly map of mount etna volcano southern italy abstract a high resolution aeromagnetic survey of mount etna volcano was carried out by the airborne geophysics science team of istituto nazionale di geofisica e vulcanologia ingv aimed at producing the most detailed magnetic anomaly map existing so far for this area two datasets of the total intensity of the earth s magnetic field were collected at different altitudes to take into account the huge topographic variations of etna volcano that reaches elevations above 3300 m asl one level was flown at the altitude of 2200 m whereas a second one over the central part at about 3500 m of altitude since the region is characterized by a large presence of strongly magnetized volcanic products the survey was carried out acquiring profile lines only in order to optimize the resources from the residual magnetic anomaly analysis we inferred two main trending lineaments 35 n and 0 n that are related to regional tectonic stress field and we interpret the main magnetic anomaly as the effect of thickness variation of magnetized volcanic products due to the complex pre volcanic basement morphology of etna

erosion rates and weathering history of rock surfaces associated with aboriginal rock art engravings petroglyphs on burrup peninsula western australia from cosmogenic nuclide measurements abstract the burrup peninsula and surrounding dampier archipelago in western australia contain the world s largest known gallery of rock art engravings petroglyphs estimated to number up to 1 million images the peninsula is also the site of major industrial development and there are concerns that industrial emissions may adversely affect the stability and longevity of the rock art we have studied the natural processes and rates of weathering and erosion including the effects of fire that affect the stability of rock surfaces and hence the longevity of the rock art using cosmogenic nuclides the concentration of 10 be in quartz yields erosion rates in the range 0 15 0 48 mm 1000 years on horizontal rock surfaces and 0 34 2 30 mm 1000 years on vertical rock faces the former largely caused by mm scale surface flaking are amongst the lowest erosion rates measured by cosmogenic nuclides anywhere in the world the latter are inferred to represent a combination of mm scale flaking and very rare centimetre to metre scale block falls controlled by failure along joint planes such low erosion rates result from a combination of resistant rocks low relief and low rainfall favouring long term preservation of the petroglyphs long enough to encompass the known period of human settlement in australia