revised calendar date for the taupo eruption derived by 14c wiggle matching using a new zealand kauri 14c calibration data set taupo volcano in central north island new zealand is the most frequently active and productive rhyolite volcano on earth its latest explosive activity about 1800 years ago generated the spectacu

source parameters of the 1992 melilla spain mw 4 8 1994 alhoceima morocco mw 5 8 and 1994 mascara algeria mw 5 7 earthquakes and seismotectonic implications source mechanisms of the melilla alhoceima and mascara earthquakes including fault plane solutions waveform modeling and spectral analysis are presented strike slip solutions have been obtained for the melilla and alhoceima earthquakes and reverse faulting for mascara teleseismic p wave inversion using broadband data show a complex mechanism for the alhoceima earthquake formed by two subevents at very shallow depth 7 and 8 km and scalar seismic moments of 1 1 10e 17 n m and 4 8 10e 17 n m the mascara earthquake was a single event with a shallow depth 4 5 km and a scalar seismic moment of 3 3 10e 17 n m results of the alhoceima melilla and mascara earthquakes together with 53 focal mechanisms in the region show a regional stress regime that corresponds to horizontal compression in a nw se direction associated with the convergence between eurasia and africa a change of the stress regime in the plate boundary of the ibero maghrebian region has been found

pollen and lignin records of late quaternary vegetation lake washington analyses of lignin oxidation products and pollen for an 11 meter core from lake washington provide independent but similar reconstructions of the late quaternary vegetation in the puget lowland an exception is in sediments of the late pleistocene where pollen percentages and influx values suggest conifer forest whereas lignin compositions suggest a treeless source region this dissimilarity appears to result from different major provenances eolian transport of pollen to the lake from adjacent or downstream drainage basins as opposed to fluvial transport of lignified plant debris only from the lake washington drainage basin

high resolution imagery of active faulting offshore al hoceima northern morocco abstract two recent destructive earthquakes in 1994 and 2004 near al hoceima highlight that the northern moroccan margin is one of the most seismically active regions of the western mediterranean area despite onshore geodetic seismological and tectonic field studies the onshore offshore location and extent of the main active faults remain poorly constrained offshore al hoceima high resolution seismic reflection and swath bathymetry have been recently acquired during the marlboro 2 cruise these data at shallow water depth close to the coast allow us to describe the location continuity and geometry of three active faults bounding the offshore nekor basin the well expressed normal left lateral onshore trougout fault can be followed offshore during several kilometers with a n171 e 3 trend westward the bousekkour aghbal normal left lateral onshore fault is expressed offshore with a n020 e 4 trending fault the n030 e 2 bokkoya fault corresponds to the western boundary of the plio quaternary offshore nekor basin in the al hoceima bay and seems to define an en echelon tectonic pattern with the bousekkour aghbal fault we propose that these three faults are part of the complex transtensional system between the nekor fault and the al idrissi fault zone our characterization of the offshore expression of active faulting in the al hoceima region is consistent with the geometry and nature of the active fault planes deduced from onshore geomorphological and morphotectonic analyses as well as seismological geodetic and geodynamic data

the crustal domains of the alboran basin western mediterranean the alboran basin in the westernmost mediterranean hosts the orogenic boundary between the iberian and african plates although numerous geophysical studies of crustal structure onshore iberia have been carried out during the last decade the crustal structure of the alboran basin has comparatively been poorly studied we analyze crustal scale images of a grid of new and reprocessed multichannel seismic profiles showing the tectonic structure and variations in the reflective character of the crust of the basin the nature of the distinct domains has been ground truthed using available basement samples from drilling and dredging our results reveal four different crustal types domains of the alboran basin a a thin continental crust underneath the west alboran and malaga basins which transitions to b a magmatic arc crust in the central part of the alboran sea and the east alboran basin c the north african continental crust containing the pytheas and habibas sub basins and d the oceanic crust in the transition towards the algero balearic basin the alboran basin crust is configured in a fore arc basin west alboran and malaga basins a magmatic arc central and east alboran and a back arc system in the easternmost part of the east alboran basin and mainly algero balearic basin the north african continental crust is influenced by arc related magmatism along its edge and was probably affected by strike slip tectonics during westward migration of the miocene subduction system the distribution of active tectonic structures in the current compressional setting generally corresponds to boundaries between domains possibly representing inherited lithospheric scale weak structures

seismic evidence of current controlled sedimentation in the alboran sea during the pliocene and quaternary palaeoceanographic implications abstract a seismic analysis of the pliocene and quaternary stratigraphy was conducted in the alboran sea westernmost mediterranean using more than 1250 profiles consisting of single and multi channel seismic records this allowed for the updating and renaming of the stratigraphic boundaries and the establishment of a new pliocene and quaternary seismic stratigraphy for the alboran sea after the relocation of the base of the quaternary from 1 8 to 2 6 ma the boundaries of the stratigraphic division are as follows the messinian m at 5 96 to 5 33 ma the intra lower pliocene p0 at ca 4 5 ma the top of the zanclean p1 at ca 3 3 ma the base of the quaternary bqd at ca 2 6 ma the top of the gelasian q0 at ca 1 8 ma the intra lower quaternary q1 at ca 1 12 ma and the top of the calabrian q2 at ca 0 7 ma additionally for the first time the seismic analysis allowed us to present and discuss the evidence of contourite features reaching the scale of the alboran basin contourite drifts plastered sheeted elongated separated and confined monticular drifts and erosive features terraces scarps moats and channels were developed under the continuous influence of mediterranean water masses light and dense after the opening of the strait of gibraltar in the latest miocene 5 46 ma there are at least two primary factors controlling the contourite features based on the seismic analysis as follows i tectonics which has governed the relocation of the main mediterranean flow pathways and their circulation patterns and ii climate which has influenced both water mass conditions interfaces and hinterland sediment sources conditioning the morpho seismic expression and growth pattern of the drifts and terrace formation dimensions the distribution of contourite features through time and space has allowed us to propose the three following main scenarios for ocean circulation since the opening of the strait of gibraltar atlantic zanclean flooding the pliocene sea with two different stages for the dense circulation and the quaternary sea with well defined and stable interfaces for the atlantic waters aw light and dense mediterranean waters

devensian lateglacial environmental changes in britain a multi proxy environmental record from llanilid south wales uk abstract a multi proxy environmental record for the devensian weichselian lateglacial and early holocene periods which includes pollen plant macrofossil coleopteran geochemical and stable isotope data is described from a site at llanilid south wales uk the geochronology of the sequence is derived from two age depth models which show a broad measure of agreement over much of the profile this data set provides the basis for a detailed reconstruction of changing environmental conditions in western britain during the transition from the last cold stage to the present holocene interglacial ca 15 000 10 000 cal yr bp two marked cooling episodes are recorded during the course of the lateglacial interstadial greenland interstadial 1 with mean july temperatures falling by more than 5 c from a maximum of around 20 c during the early interstadial and by a further 4 5 c around 13 100 cal yr bp the initial drop in temperature led to a reduction in juniperus scrub while the second and more abrupt temperature decline resulted in a significant contraction in areas of betula woodland a relatively slight and short lived warming during the later interstadial enabled tree birch to expand once again mean july temperatures of 10 11 c characterised the loch lomond younger dryas stadial greenland stadial 1 between ca 12 600 and 11 400 cal yr bp during which time a scrub tundra with betula salix and a range of open habitat taxa became established locally the onset of the holocene interglacial at ca 11 400 cal yr bp is marked by an abrupt temperature rise of the order of 9 c and by the rapid expansion of betula woodland the llanilid palaeoclimate record is similar to that from the gransmoor site in northeast england and also to the climatic sequence inferred from the grip ice core particularly during the later part of the lateglacial interstadial ca 14 000 12 600 cal yr bp during the loch lomond younger dryas stadial and in the early holocene the llanilid chronology is less secure during the early part of the lateglacial interstadial pre 14 000 cal yr bp but it is possible that warming may have begun earlier in this part of western britain than in greenland

are the seismological and geological observations of the al hoceima morocco rif 2004 earthquake m 6 3 contradictory abstract seismic hazard is associated with recent and present fault activity in mountain ranges in the betic rif alpine mountain chain tectonic activity started in the cretaceous and topographic uplift continues since tortonian times as a consequence of the nw se oblique convergence between africa and eurasia the deformation is active and produces seismicity that sometimes has catastrophic consequences the al hoceima earthquake february 24 2004 considered one of the largest earthquakes ever recorded instrumentally in the westernmost mediterranean m 6 3 caused great damage in the region seismological studies agree that the main shock was situated on land at the limit between the external and internal zones of the rif at a depth of 10 14 km the focal mechanism points to a strike slip solution with a nw se oriented p axis quite similar to those of the significant 1994 earthquake swarm located to the north the epicenter aftershocks distribution would signal the presence of a n s oriented sinistral fault activated by the nw se regional compression associated to plate boundary convergence in this setting the seismogenic fault ruptures related to these seismic events are expected to have reached the earth s surface however detailed field work carried out 1 month after the earthquake does not evidence any n s strike slip coseismic fault in the epicentral area the main observed effects were landslides damages to constructions and locally open cracks indicating an unexpected nw se extension scarce n s faults are normal the main ones being located several kilometers away from the epicentral area to explain this apparent contradiction between geological and seismological observations we propose a decoupled tectonic model with crustal detachments that separate a deep brittle crust from an upper crust undergoing uplift and the development of large folds and normal faults this geological setting common to internal zones of cordilleras may need to be taken into account in future paleoseismicity studies and in the assessment of seismic hazard

an integrated geophysical investigation of recent seismicity in the al hoceima region of north morocco abstract data produced by the moroccan national seismological network and marine seismic reflection profiles are used to investigate the most seismically active region in morocco located on the mediterranean coast at the intersection of the rif mountain belt and the submarine alboran ridge this region in the vicinity of the city of al hoceima marks an east west transition in the marine and land deformation styles of the distributed plate boundary between africa and iberia and was the site of an m w 6 0 earthquake on 26 may 1994 the epicenter of the al hoceima earthquake is relocated onshore refining the initial submarine location close to the alboran ridge the spatial distribution of foreshocks and aftershocks shows a ne sw trend that continues partly offshore and is subparallel to the earlier yet still prominent miocene geologic structural trend the predominantly strike slip focal mechanism for the al hoceima event is characteristic of earthquakes in the region marine seismic reflection profiles that intersect the offshore region of seismicity image active high angle faults with possible strike slip components the seismicity trend is not directly related to the submarine alboran ridge or the geomorphologically prominent nekor fault deformation appears to be occurring on a number of subsidiary strike slip faults that together compose a ne sw zone of distributed shear the distributed strike slip and documented normal faulting taking place in the eastern rif mountains although characteristic of the rif region are in contrast to the thrusting style of deformation that occurs farther to the east in the algerian tell atlas this may be related to the reported lateral variations and evolution of the convergent plate boundary in these regions during the neogene and quaternary times

seismicity and active tectonics in the alboran sea western mediterranean constraints from an offshore onshore seismological network and swath bathymetry data seismicity and tectonic structure of the alboran sea were derived from a large amphibious seismological network deployed in the offshore basins and onshore in spain and morocco an area where the convergence between the african and eurasian plates causes distributed deformation crustal structure derived from local earthquake data suggests that the alboran sea is underlain by thinned continental crust with a mean thickness of about 20 km during the 5 months of offshore network operation a total of 229 local earthquakes were located within the alboran sea and neighboring areas earthquakes were generally crustal events and in the offshore domain most of them occurred at crustal levels of 2 to 15 km depth earthquakes in the alboran sea are poorly related to large scale tectonic features and form a 20 to 40 km wide nne ssw trending belt of seismicity between adra spain and al hoceima morocco supporting the case for a major left lateral shear zone across the alboran sea such a shear zone is in accord with high resolution bathymetric data and seismic reflection imaging indicating a number of small active fault zones some of which offset the seafloor rather than supporting a well defined discrete plate boundary fault moreover a number of large faults known to be active as evidenced from bathymetry seismic reflection and paleoseismic data such as the yusuf and carboneras faults were seismically inactive earthquakes below the western alboran basin occurred at 70 to 110 km depth and hence reflected intermediate depth seismicity related to subducted lithosphere

evidence for a mazama like tephra deposited ca 10 000 bp at copper lake banff national park alberta mazama tephra is a widespread mid holocene stratigraphic marker dating to ca 6845 bp and is considered useful for the correlation of holocene events in western north america we present evidence from copper lake alberta for a tephra layer that underlies mazama tephra and appears to be a discrete tephra layer but that is indistinguishable from the conventional mazama tephra by microprobe analysis of glass shards three alternative hypotheses are considered to explain this tephra underlying mazama in situ position of an earlier mazama like tephra recycling of tephras and settling of tephra slabs through the gyttja the size distributions of birch pollen grains indicate that the mazama like tephra is in primary stratigraphic position in the early holocene gyttja and that sediment recycling has not destroyed the integrity of copper lake sediment stratigraphy it is concluded that most probably a mazama like tephra was deposited between 9700 and 10 500 bp if this in situ hypothesis is correct the id

kinematics of the western africa eurasia plate boundary from focal mechanisms and gps data summary the western mediterranean displays a complex pattern of crustal deformation distributed along tectonically active belts developed in the framework of slow oblique plate convergence we used earthquake and global positioning system gps data to study the present day kinematics and tectonics of the africa eurasia plate boundary in this region crustal seismicity and focal mechanisms analysed in terms of seismic moment release and seismic deformation outline the geometry of major seismic belts and characterize their tectonics and kinematics continuous gps data have been analysed to determine euler vectors for the nubian and eurasian plates and to provide the global frame for a new mediterranean gps velocity field obtained by merging continuous and campaign observations collected in the 1991 2005 time span gps velocities and displacements predicted by the nubia eurasia rotation pole provide estimates of the deformation accommodated across the tectonically active belts the rather simple deformation occurring in the atlantic region characterized by extension about perpendicular to the middle atlantic and terceira ridges and right lateral motion along the gloria transform fault turns into a complex pattern of deformation occurring along broader seismic belts where continental lithosphere is involved our analysis reveals a more complex fragmentation of the plate boundary than previously proposed the roughly e w trending mainly compressive segments i e southwestern iberia northern algeria and southern tyrrhenian where plate convergence is largely accomodated across rather localized deformation zones and partially transferred northward to the adjacent domains i e the algero balearic and tyrrhenian basins are interrupted by regions of more distributed deformation i e the rif alboran betics tunisia libya and eastern sicily or limited seismicity i e the strait of sicily which are characterized by less homogeneous tectonics regimes mainly transcurrent to extensional in correspondence of the observed breaks tectonic structures with different orientation interfere and we find belts with only limited deformation i e the high and middle atlas the tunisian atlas and the offshore tunisia libya belt that extends from the plate boundary into the nubian plate along pre existing tectonic lineaments our analysis suggest that the sicilian pelagian domain is moving independently from nubia according to the presence of a right lateral and extensional decoupling zone corresponding to the tunisia libya and strait of sicily deformation zone despite the space variability of active tectonic regimes plate convergence still governs most of the seismotectonic and kinematic setting up to the central aeolian region in general local complexities derive from pre existing structural features inherited from the tectonic evolution of the mediterranean region on the contrary along calabria and the apennines the contribution of the subducted ionian oceanic lithosphere and the occurrence of microplates i e adria appear to substantially modify both tectonics and kinematics finally gps data across the gibraltar arc and the tyrrhenian calabria domain support the hypothesis that slab rollback in these regions is mostly slowed down or stopped

age and impacts of the caldera forming aniakchak ii eruption in western alaska the mid holocene eruption of aniakchak volcano aniakchak ii in southwest alaska was among the largest eruptions globally in the last 10 000 years vei 6 despite evidence for possible impacts on global climate the precise age of the eruption is not well constrained and little is known about regional environmental impacts a closely spaced sequence of radiocarbon dates at a peatland site over 1000 km from the volcano show that peat accumulation was greatly reduced with a hiatus of approximately 90 120 yr following tephra deposition during this inferred hiatus no paleoenvironmental data are available but once vegetation returned the flora changed from a cyperaceae dominated assemblage to a poaceae dominated vegetation cover suggesting a drier and or more nutrient rich ecosystem oribatid mites are extremely abundant in the peat at the depth of the ash and show a longer term increasingly wet peat surface across the tephra layer the radiocarbon sample immediately below the tephra gave a date of 1636 1446 cal yr bc suggesting that the eruption might be younger than previously thought our findings suggest that the eruption may have led to a widespread reduction in peatland carbon sequestration and that the impacts on ecosystem functioning were profound and long lasting

improved age modelling and high precision age estimates of late quaternary tephras for accurate palaeoclimate reconstruction abstract the role of tephrochronology as a dating and stratigraphic tool in precise palaeoclimate and environmental reconstruction has expanded significantly in recent years the power of tephrochronology rests on the fact that a tephra layer can stratigraphically link records at the resolution of as little as a few years and that the most precise age for a particular tephra can be imported into any site where it is found in order to maximise the potential of tephras for this purpose it is necessary to have the most precise and robustly tested age estimate possible available for key tephras given the varying number and quality of dates associated with different tephras it is important to be able to build age models to test competing tephra dates recent advances in bayesian age modelling of dates in sequence have radically extended our ability to build such stratigraphic age models as an example of the potential here we use bayesian methods now widely applied to examine the dating of some key late quaternary tephras from italy these are the agnano monte spina tephra amst the neapolitan yellow tuff nyt and the agnano pomici principali app and all of them have multiple estimates of their true age further we use the bayesian approaches to generate a revised mixed radiocarbon varve chronology for the important lateglacial section of the lago grande monticchio record as a further illustration of what can be achieved by a bayesian approach with all three tephras we were able to produce viable model ages for the tephra validate the proposed 40 ar 39 ar age ranges for these tephras and provide relatively high precision age models the results of the bayesian integration of dating and stratigraphic information suggest that the current best 95 confidence calendar age estimates for the amst are 4690 4300 cal bp the nyt 14320 13900 cal bp and the app 12380 12140 cal bp

out of tune the dangers of aligning proxy archives abstract tuning is a widespread technique to combine date and interpret multiple fossil proxy archives through aligning supposedly synchronous events between the archives the approach will be reviewed by discussing a number of literature examples ranging from peat and tephra layers to orbital tuning and 18o series from marine and ice deposits potential problems will be highlighted such as the dangers of circular reasoning and unrecognised chronological uncertainties and some solutions suggested fossil proxy research could become enhanced if tuning were approached in a more quantitative reliable and objective way and especially if individual proxy archives were non tuned and kept on independent time scales

which fault destroyed fes city morocco in 1755 a new insight from the holocene deformations observed along the southern border of gibraltar arc in this paper we present the first estimate of the holocene deformation along the southern front of gibraltar arc morocco and the first field constraints on the local 1755 ce fes meknes surface rupturing earthquake which could be associated to the great lisbon earthquake m 8 5 in november 1st 1755 using satellite imagery aerial photographs and field investigations we carried out a morphotectonic study along the 150 km long southern rif front srf to identify the most recent evidences of tectonic activity analyzed offset alluvial deposits confirm that i the last 5 ka cumulative deformation leading to a slip rate of 3 5 1 mm yr for this segment of the srf is consistent with the gps derived horizontal shortening rate of 2 4 mm yr and ii a recent major earthquake ruptured a 30 km long segment along the srf based on deposits dating and historical seismicity we propose that this seismic event occurred in 1755 as a local earthquake even though this 1755 local event cannot be considered as a strong aftershock of the main lisbon seismic event m 8 5 their temporal closeness their occurrence under the same convergent stress regime nnw sse oriented compression and the fact that fes meknes area was strongly shaken during the lisbon earthquake raises the question of the possible triggering of the fes earthquake anyway our new results suggest that most of the nubia rif belt convergence is accommodated by the srf making it potentially the most destructive structure of the rif

polyphase tectonic evolution of fore arc basin related to step fault as revealed by seismic reflection data from the alboran sea w mediterranean 25 pages 14 figures 1 table seismic reflection and bathymetric data collected during the marlboro and saras cruises are stored at sismer and seanoe sea scientific open data edition https doi org 10 17600 11480100 https doi org 10 17600 12450090 and https campagnes flotteoceanographique fr campagnes 12000010

ages of 24 widespread tephras erupted since 30 000 years ago in new zealand with re evaluation of the timing and palaeoclimatic implications of the lateglacial cool episode recorded at kaipo bog abstract tephras are important for the nz intimate project because they link all three records comprising the composite inter regional stratotype developed for the new zealand climate event stratigraphy nz ces here we firstly report new calendar ages for 24 widespread marker tephras erupted since 30 000 calendar cal years ago in new zealand to help facilitate their use as chronostratigraphic dating tools for the nz ces and for other palaeoenvironmental and geological applications the selected tephras comprise 12 rhyolitic tephras from taupo nine rhyolitic tephras from okataina one peralkaline rhyolitic tephra from tuhua and one andesitic tephra each from tongariro and egmont taranaki volcanic centres age models for the tephras were obtained using three methods i 14 c based wiggle match dating of wood from trees killed by volcanic eruptions these dates published previously ii flexible depositional modelling of a high resolution 14 c dated age depth sequence at kaipo bog using two bayesian based modelling programs bacon and oxcal s p sequence function and the intcal09 data set with sh offset correction 44 17 yr and iii calibration of 14 c ages using oxcal s tau boundary function and the shcal04 and intcal09 data sets our preferred dates or calibrated ages for the 24 tephras are as follows youngest to oldest all mid point or mean ages of 95 probability ranges kaharoa ad 1314 12 taupo unit y ad 232 10 mapara unit x 2059 118 cal yr bp whakaipo unit v 2800 60 cal yr bp waimihia unit s 3401 108 cal yr bp stent unit q 4322 112 cal yr bp unit k 5111 210 cal yr bp whakatane 5526 145 cal yr bp tuhua 6577 547 cal yr bp mamaku 7940 257 cal yr bp rotoma 9423 120 cal yr bp opepe unit e 9991 160 cal yr bp poronui unit c 11 170 115 cal yr bp karapiti unit b 11 460 172 cal yr bp okupata 11 767 192 cal yr bp konini bed b 11 880 183 cal yr bp waiohau 14 009 155 cal yr bp rotorua 15 635 412 cal yr bp rerewhakaaitu 17 496 462 cal yr bp okareka 21 858 290 cal yr bp te rere 25 171 964 cal yr bp kawakawa oruanui 25 358 162 cal yr bp poihipi 28 446 670 cal yr bp and okaia 28 621 1428 cal yr bp secondly we have re dated the start and end of the lateglacial cool episode climate event nzce 3 in the nz ces previously referred to as the lateglacial climate reversal as defined at kaipo bog in eastern north island new zealand using both bacon and oxcal p sequence modelling with the intcal09 data set the ca 1200 yr long cool episode indicated by a lithostratigraphic change in the kaipo peat sequence to grey mud with lowered carbon content and a high resolution pollen derived cooling signal began 13 739 125 cal yr bp and ended 12 550 140 cal yr bp mid point ages of the 95 highest posterior density regions bacon modelling the oxcal modelling generating almost identical ages confirmed these ages the lateglacial cool episode ca 13 8 12 6 cal ka bp thus overlaps a large part of the entire antarctic cold reversal chronozone ca 14 1 12 4 cal ka bp or ca 14 6 12 8 cal ka bp and an early part of the greenland stadial 1 younger dryas chronozone ca 12 9 11 7 cal ka bp the timing of the lateglacial cool episode at kaipo is broadly consistent with the latitudinal patterns in the antarctic cold reversal signal suggested for the new zealand archipelago from marine and terrestrial records and with records from southern south america

from extension to shortening tectonic inversion distributed in time and space in the alboran sea western mediterranean 2d seismic reflection data tied to biostratigraphical and log information from wells in the central and south eastern alboran sea have allowed us to constrain the spatial and temporal distribution of rifting and inversion normal faults tilted basement blocks and growth wedges reveal a thinned continental crust that formed in response to nw se extension to the east a secondary sw ne trend of extension affects the transitional crust adjacent to the oceanic algerian basin the maximum thickness of syn rift sediments is 3 5 km and the oldest recorded deposits are serravallian the wnw ese yusuf fault formed a buttress separating and accommodating variable extension between two different tectonic domains the thinned continental crust of alboran and the oceanic spreading of the algerian basin late tortonian to present day nw se africa eurasia plate convergence drove shortening and reactivation of some of the earlier extensional structures as reverse and strike slip faults forming complex compartmentalised sub basins tectonic inversion coexisted with the formation of new faults and folds inversion was partial along the habibas basin and al idrisi fault but complete along the alboran ridge where some sw ne trending faults were perpendicular to the recent nw se plate convergence and were reactivated as thrusts the wnw ese yusuf fault is oblique to the convergence vector and therefore reactivation is mainly expressed as transpressional deformation volcanic rocks intruded along the alboran ridge and yusuf faults during the latest stages of extension formed rheological anisotropies that localised the later inversion

identification and correlation of visible tephras in the lake suigetsu sg06 sedimentary archive japan chronostratigraphic markers for synchronising of east asian west pacific palaeoclimatic records across the last 150 ka abstract the lake suigetsu sg06 sedimentary archive from honshu island central japan provides a high resolution palaeoenvironmental record including a detailed record of explosive volcanism from japan and south korea thirty visible tephra are recorded within the 73 m long sg06 core which spans the last 150 ka here we describe and characterise these tephras based on major element glass composition which is useful for the identification and correlation of these tephras and the age models of the records in which they are found utilising the large number of radiocarbon measurements n 600 from terrestrial plant macrofossils in the lake suigetsu sg06 record we are able to provide precise and accurate ages for the tephras from eruptions within the last 50 ka glass compositional data of some of the largest eruptions from japan k ah at aso 4 aso a aso d and ata sampled at proximal outcrops are also presented these data show that the major element glass chemistry is distinctive for many of the visible sg06 tephra units and allows some of the layers to be correlated to known eruptions from volcanoes in japan and south korea namely k ah sg06 0967 u oki sg06 1288 at sg06 2650 aso 4 sg06 4963 sg06 4979 k tz sg06 5181 aso abcd sg06 5287 and ata sg06 5181 the following ages were obtained for the sg06 tephra units 3 966 4 064 cal ka bp 95 4 probability range for the sg06 0588 tephra 10 242 10 329 cal ka bp 95 4 probability range for sg06 1293 19 487 112 sg06 2012 ka bp 2 for sg06 1965 28 425 194 sg06 2012 ka bp 2 for sg06 2504 28 848 196 sg06 2012 ka bp 2 for sg06 2534 29 765 190 sg06 2012 ka bp 2 for sg06 2601 29 775 191 sg06 2012 ka bp 2 for sg06 2602 43 713 156 sg06 2012 ka bp 2 for sg06 3485 46 364 202 sg06 2012 ka bp 2 for sg06 3668 49 974 337 sg06 2012 ka bp 2 for sg06 3912 50 929 378 sg06 2012 ka bp 2 for sg06 3974 and improved ages for two of the most important tephra markers across japan the k ah 7 165 7 303 cal ka bp at 95 4 probability range sg06 0967 and at tephra 30 009 189 sg06 2012 ka bp at 2 sg06 2650

bayesian tools for tephrochronology it is suggested that bayesian statistical methods for radiocarbon data interpretation already widely used in archaeology also have potential to improve the dating of tephra layers and hence enhance their use for tephrochronology by re analysing data from a recently published paper in which the authors sought to identify the calendar date of the eruption of fourteenth century ad kaharoa tephra a key marker in new zealand prehistory it is shown that bayesian methods can be used to draw together a coherent collection of radiocarbon data undertake formal outlier detection and include prior information regardless of the calibration curve adopted the distribution of likely dates for the kaharoa eruption is multimodal by including prior information from wiggle matched dendrochronology the uncertainty on the estimate of the calendar date is reduced from a range of about 100 years to about 25 years i e 648 623 cal bp with modes at 638 and 632 cal bp using sensitivity analysis however it is shown that such estimates are affected by the quality and nature of the prior information available as a result we urge tephrochronologists to seek fastidiously both high quality radiocarbon data and reliable stratigraphic sequences that might inform future geochronological model building

compressional tectonic inversion of the algero balearic basin latemost miocene to present oblique convergence at the palomares margin western mediterranean interpretation of new multichannel seismic reflection profiles indicates that the palomares margin was formed by crustal scale extension and coeval magmatic accretion during middle to late miocene opening of the algero balearic basin the margin formed at the transition between thinned continental crust intruded by arc volcanism and back arc oceanic crust deformation produced during the later positive inversion of the margin offshore and onshore is partitioned between n50 e striking reverse faults and associated folds like the sierra cabrera and abubacer anticlines and n10 20 e sinistral strike slip faults like palomares and terreros faults parametric subbottom profiles and multibeam bathymetry offshore structural analysis available gps geodetic displacement data and earthquake focal mechanisms jointly indicate that tectonic inversion of the palomares margin is currently active the palomares margin shows a structural pattern comparable to the north maghrebian margins where africa eurasia plate convergence is accommodated by ne sw reverse faults nnw sse sinistral faults and wnw ese dextral ones contractive structures at this margin contribute to the general inversion of the western mediterranean since 7 ma coeval to inversion at the algerian margin shortening at the alboran ridge and al idrisi faults occurred later since 5 ma indicating a westward propagation of the compressional inversion of the western mediterranean

major and trace element characterization expanded distribution and a new chronology for the latest pleistocene glacier peak tephras in western north america keuhn s c froese d g carrara p e foit jr f f pearce n j g rotheisler p 2009 major and trace element characterization expanded distribution and a new chronology for the latest pleistocene glacier peak tephras in western north america quaternary research 71 2 201 216 sponsorship nserc discovery grant alberta ingenuity new faculty award to duane froese

imaging the growth of recent faults the case of 2016 2017 seismic sequence sea bottom deformation in the alboran sea western mediterranean

the spatial distribution of holocene cryptotephras in north west europe since 7 ka implications for understanding ash fall events from icelandic eruptions abstract we present distribution maps for all cryptotephras distal volcanic ash layers younger than 7 ka that have been reported from three or more lakes or peatlands in north west europe all but one of the tephras originates from iceland the exception has been attributed to jan mayen we find strong spatial patterning in tephra occurrence at the landscape scale most but not all of the tephra occurrences are significantly spatially clustered which likely reflects atmospheric and weather patterns at the time of the eruptions contrary to expectations based on atmospheric modelling studies tephras appear to be at least as abundant in ireland and northern scotland as in scandinavia rhyolitic and other felsic tephras occur in lakes and peatlands throughout the study region but andesitic and basaltic tephras are largely restricted to lake sites in the faroe islands and ireland explanations of some of these patterns will require further research on the effects of different methodologies for locating and characterizing cryptotephras these new maps will help to guide future investigations in tephrochronology and volcanic hazard analysis

role of soil pore structure in water infiltration and co2 exchange between the atmosphere and underground air in the vadose zone a combined laboratory and field approach the soils above caves represent a membrane that regulates the connection between the underground environment and the outside atmosphere in this study soils from two different field sites cueva de altamira and cueva del rull in spain are investigated field results are analysed and linked to laboratory tests several laboratory experiments are performed to quantify co2 diffusion coefficients and water infiltration rates in these soils under different degrees of soil water saturation and compaction tests confirm that the grain size distribution organic matter content mineral composition and water content of soils affect gas transport through the soil pore network both field and lab results reveal that altamira soil has a coarser texture and therefore has higher co2 diffusion coefficients infiltration rates and hydraulic conductivity values than rull soil rull soil contains a higher proportion of fine particles and organic matter which explains the lower fluid transport coefficients when soils are near saturation fluid transport does not depend on the physical properties of soil but depends on the soil water content in this state liquid transport regulates the available space within the soil pores which leads to a reduction in the gaseous diffusion coefficient of the soil after rainfall episodes the connection between the exterior atmosphere and underground cavities is hindered due to a rise in the soil water content which is responsible for the closure of the overlying membrane this study demonstrates that soil produced co2 reaches the underground atmosphere through diffusion processes that are controlled by the intrinsic properties of soil porosity grain size distribution texture mineralogy and organic matter content and soil water content

mount mazama eruption calendrical age verified and atmospheric impact assessed geochemical identification of mount mazama ash in the greenland ice sheet project 2 gisp2 ice core gives a calendrical age of 7627 150 cal yr b p 5677 150 b c for the eruption thus providing a more accurate early holocene stratigraphic time line than previously available the gisp2 record of volcanically derived sulfate suggests a total stratospheric aerosol loading between 88 and 224 mt spread over an 6 yr period following the eruption of mount mazama taking into account the likelihood of some tropospheric aerosol transport to greenland realistic estimates of the resulting atmospheric optical depth range from 0 6 to 1 5 these values may have produced a temperature depression of 0 6 to 0 7 c at mid to high northern latitudes for 1 3 yr after the eruption these results indicate that the 5677 b c eruption of mount mazama was one of the most climatically significant volcanic events of the holocene in the northern hemisphere we also calculate a maximum stratospheric cl release of 8 1 mt by the eruption which may have led to substantial stratospheric ozone depletion

the al hoceima morocco earthquake of 24 february 2004 analysis and interpretation of data from envisat asar and spot5 validated by ground based observations abstract the magnitude mw 6 3 earthquake in al hoceima morocco of 24 february 2004 occurred in the active plate boundary accommodating the oblique convergence between africa and eurasia three different sets of estimates of its source parameters have already been published we try to resolve the discrepancies between them by using additional data including two remote sensing satellite systems envisat and spot5 using a model with a dislocation in an elastic half space we constrain the source parameters the hypothesis of two subevents on distinct faults as inferred from seismological inversions is confirmed here by adopting a cross fault mechanism the rupture began on a left lateral strike slip fault striking at n10 azimuth with 90 cm of horizontal slip and then transferred to a right lateral strike slip fault striking at n312 azimuth with 85 cm of horizontal slip the first fault is at 500 m depth from the free surface and the second fault is at 3 km depth this model is consistent with ground based observations including gps seismology and mapped surface fissures the pair of faults activated in 2004 appears to constitute part of a complex seismogenic structure striking nne ssw that separates the rif tectonic blocks

the 1994 2004 al hoceima morocco earthquake sequence conjugate fault ruptures deduced from insar abstract we study the may 26 1994 mw 6 0 and february 24 2004 mw 6 4 earthquakes that affected the al hoceima region of northern morocco these events are the two strongest earthquakes recorded in this region yet the exact location kinematics and relationships between these earthquakes are poorly known since neither of them produced surface ruptures using synthetic aperture radar interferometry insar we mapped the surface displacement field of the two earthquakes to characterize their seismic source parameters analysis of the interferograms constructed from ascending and descending orbits for both earthquakes and subsequent elastic modeling using slip inversions on triangular fault patches suggest that the two mainshocks occurred on blind conjugate strike slip faults the 1994 earthquake being associated with n23 e trending left lateral fault and the 2004 earthquake with n45 w trending right lateral fault this result contradicts previous inferences on the kinematics location and rupture geometry of the earthquakes deduced from conventional analyses of seismic waveforms and aftershocks distribution the insar analysis reveals the fragmentation of the rif mountain throughout a complex network of conjugate blind faults consistent with the transpression tectonics along the plate boundary in north africa although the two earthquakes took place in the rif thrust and fold belt the late quaternary deformation indicates e w extension in agreement with the nw se and ne sw trending conjugate strike slip faulting

la marge meridionale de la mer d alboran caracteres structuro sedimentaires et evolution recente abstract high resolution seismic reflection profiles 2000 km were collected across the southern continental margin and major structural trends of the alboran sea seismic units are dated on the basis of well known marine neogene onshore sections and offshore dredged samples a better assessment of margin structuration and neogene chronology is made a conformable succession of pliocene quaternary and older series provides evidence for the non evaporitic nature of the upper miocene similar to the facies from the onshore neogene boudinar and melilla basins it also suggests that alboran ridge is in part sedimentary rather than only volcanic this ridge appears as an en echelon anticlinal complex conformable upper miocene and lower pliocene quaternary strata are folded and faulted primarily important manifestation of the movements is dated as pliocene but the main vertical relative movements are of quaternary to recent age as emphasized by well developed divergent strata lying above submarine volcanism probably miocene in age often controls the morphology and structure of the eastern moroccan continental margin and adjacent south alboran basin the latter one is characterised by a thick sedimentary accumulation it is tectonically bounded except on the southwestern part seaward of the bokkoyas cliffs vertical movements occur during much of plio quaternary time prevailing during the quaternary the structure and related morphology of the study area are mainly the result of neotectonic events

physical properties of sorriba cultivated volcanic soils from tenerife in relation to andic diagnostic parameters in volcanic regions soils containing both noncrystalline materials and layer silicates are widespread although the respective contribution of these components to soil physical behaviours is difficult to quantify it is an important issue in the canary islands where andisols and andic soils are transported to the low lands for cultivation sorriba in this new soil environment salinisation and sodification processes induced by irrigation and heavy fertilisation are potential threats to soil degradation the purpose of this work was to evaluate some relevant physical properties of the sorriba cultivated volcanic soils from tenerife in order to relate them to salinity and sodicity soil conditions amounts of layer silicates and remaining andic properties characterised by bulk density qb al and fe extracted with ammonium oxalate alo f eo and p retention an andisol under forest was included in the study as a representative natural reference clay dispersion water release curves and saturated hydraulic conductivity ks were the selected physical properties four distinctive types of water release curves were identified showing sandy behaviour at low suctions while retaining large water holding capacity at large suctions the van genuchten parameters helped to differentiate these curves and identify the main pore size ranges under certain combinations of exchangeable cations distribution salinity and clay mineralogy very low ks values were observed for alo contents lower than 3 the results suggest that the aggregating effect of alo allophanes could not counterbalance soil structure deterioration furthermore only a multivariable analysis carried out on chemistry mineralogy and physical data had the merit to classify the studied sorriba cultivated volcanic soils in terms of soil quality and soil functioning d 2003 elsevier science b v all rights reserved

the offshore yangsan fault activity in the quaternary se korea analysis of high resolution seismic profiles abstract the nne trending dextral yangsan fault is a 190 km long structure in the korean peninsula traced to the southeastern coast the scarcity of quaternary deposits onland precludes any detailed investigation of the quaternary activity and structure of the yangsan fault using seismic reflection profiling we acquired offshore high resolution seismic profiles to investigate the extension of the yangsan fault and constrain its quaternary activity using stratigraphic markers the seismic profiles reveal a nne trending fault system consisting of a main fault and an array of subsidiary faults that displaced quaternary sequences stratigraphic analysis of seismic profiles indicates that the offshore faults were activated repeatedly in the quaternary the up to the east sense of throw on the main fault and plan view pattern of the fault system are explained by dextral strike slip faulting the main fault when projected toward the korean peninsula along its strike aligns well with the yangsan fault we suggest that the offshore fault system is a continuation of the yangsan fault and has spatial correlation with weak but ongoing seismicity

submarine fault scarps in the sea of marmara pull apart north anatolian fault implications for seismic hazard in istanbul earthquake scarps associated with recent historical events have been found on the floor of the sea of marmara along the north anatolian fault naf the marmarascarps cruise using an unmanned submersible rov provides direct observations to study the fine scale morphology and geology of those scarps their distribution and geometry the observations are consistent with the diversity of fault mechanisms and the fault segmentation within the north marmara extensional step over between the strike slip ganos and izmit faults smaller strike slip segments and pull apart basins alternate within the main step over commonly combining strike slip and extension rapid sedimentation rates of 1 3 mm yr appear to compete with normal faulting components of up to 6 mm yr at the pull apart margins in spite of the fast sedimentation rates the submarine scarps are preserved and accumulate relief sets of youthful earthquake scarps extend offshore from the ganos and izmit faults on land into the sea of marmara our observations suggest that they correspond to the submarine ruptures of the 1999 izmit mw 7 4 and the 1912 ganos ms 7 4 earthquakes while the 1999 rupture ends at the immediate eastern entrance of the extensional cinarcik basin the 1912 rupture appears to have crossed the ganos restraining bend into the sea of marmara floor for 60 km with a right lateral slip of 5 m ending in the central basin step over from the gulf of saros to marmara the total 1912 rupture length is probably about 140 km not 50 km as previously thought the direct observations of submarine scarps in marmara are critical to defining barriers that have arrested past earthquakes as well as defining a possible segmentation of the contemporary state of loading incorporating the submarine scarp evidence modifies substantially our understanding of the current state of loading along the naf next to istanbul coulomb stress modeling shows a zone of maximum loading with at least 4 5 m of slip deficit encompassing the strike slip segment 70 km long between the cinarcik and central basins that segment alone would be capable of generating a large magnitude earthquake mw 7 2 other segments in marmara appear less loaded

constraining the age of lateglacial and early holocene pollen zones and tephra horizons in southern sweden with bayesian probability methods the sediment sequence from hasseldala port in southeastern sweden provides a unique lateglacial early holocene record that contains five different tephra layers three of these have been geochemically identified as the borrobol tephra the hasseldalen tephra and the 10 ka askja tephra twenty eight high resolution 14 c measurements have been obtained and three different age models based on bayesian statistics are employed to provide age estimates for the five different tephra layers the chrono and pollen stratigraphic framework supports the strati graphic position of the borrobol tephra as found in sweden at the very end of the older dryas pollen zone and provides the first age estimates for the askja and hasseldalen tephras our results however highlight the limitations that arise in attempting to establish a robust chronologically independent lacustrine sequence that can be correlated in great detail to ice core or marine records radiocarbon samples are prone to error and sedimentation rates in lake basins may vary considerably due to a number of factors any type of valid and realistic age model therefore has to take these limitations into account and needs to include this information in its prior assumptions as a result the age ranges for the specific horizons at hasseldala port are large and calendar year estimates differ according to the assumptions of the age model not only do these results provide a cautionary note for over dependence on one age model for the derivation of age estimates for specific horizons but they also demonstrate that precise correlations to other palaeoarchives to detect leads or lags is problematic given the uncertainties associated with establishing age depth models for sedimentary sequences spanning the lateglacial period however this exercise employing bayesian probability methods represents the best possible approach and provides the most statistically significant age estimates for the pollen zone boundaries and tephra horizons copyright 2006 john wiley sons ltd

high precision ultra distal holocene tephrochronology in north america far travelled volcanic ashes tephras from holocene eruptions in alaska and the pacific northwest have been traced to the easternmost extent of north america providing the basis for a new high precision geochronological framework throughout the continent through tephrochronology the dating and correlation of tephra isochrons in sedimentary records the reported isochrons are geochemically distinct with seven correlated to documented sources in alaska and the cascades including the mazama ash from oregon w7600 years old and the eastern lobe of the white river ash from alaska w1150 years old these findings mark the beginning of a tephrochronological framework of enhanced precision across north america with applications in palaeoclimate surface process and archaeological studies the particle travel distances involved up to w7000 km also demonstrate the potential for continent wide or trans atlantic socio economic disruption from similar future eruptions

the effect of ash and needle cover on surface runoff and erosion in the immediate post fire period abstract hillslopes are thought to be most susceptible to enhanced surface runoff and erosion immediately following wildfire due to removal of protective vegetation and litter cover and in many cases a fire induced reduction in soil wettability this enhanced susceptibility declines as vegetation and litter layer recover for logistical reasons however few studies have been able to examine the responses of burnt terrain immediately following burning and little is therefore known about the effect of the wettable ash layer that often covers the ground until it is redistributed or removed by wind or water erosion here we quantify the effects of ash and needle cast ground cover on surface runoff generation and soil erodibility in the immediate post fire period 2 10 days following a severe wildfire in an aleppo pine forest over calcareous soils in mediterranean eastern spain a homogenous vegetation cover and lack of wind during the fire resulted in 100 ash cover 36 mm mean depth across the study area the ground fire did not consume the tree crowns but its high intensity caused complete tree mortality leading to subsequent needle fall hydrological and erosional responses were measured for fifteen 1 hour rainfall simulations 55 mm h 1 on 0 25 m2 circular plots for each of three terrain types i ash and needle covered ii ash only covered and iii bare furthermore ash and needle cast cover were monitored over an eleven week period on otherwise undisturbed terrain to examine its evolution during the first critical months following burning the soils exhibited no or slight post fire water repellency the overlying wettable ash layer had a porosity of 83 providing a water storage capacity of 30 mm a third of the plots with ground cover did not generate any surface runoff ash needle and ash only plots showed 25 and 18 fold reductions in surface runoff respectively compared to bare terrain mean sediment yield from covered plots was more than two orders of magnitudes lower than from bare plots the ash cover remained unchanged during the first two weeks while overlying needle cast more than doubled heavy rainfall 153 mm over a subsequent six day period removed the ash almost entirely where no needle cast was present whereas on ash and needle covered ground only a limited redistribution and accumulation into litter dams occurred the results quantify the potential importance of ash deposits on the susceptibility of hillslopes to surface runoff and erosion immediately following fire the combination of ash and needle cast appears particularly effective in reducing hillslope responses the outcomes demonstrate clearly that the widely held notion of landscapes being most susceptible to surface runoff and erosion directly after burning is not correct where a fire has resulted in substantial ash deposition instead the susceptibility will be greatest following a storm event of sufficient severity to remove this protective layer and before the onset of vegetation recovery

late glacial and holocene sedimentary environments of quesnel lake british columbia abstract at 512 m quesnel lake is the third deepest in north america and at 100 km long its drainage basin spans from the arid interior plateau to the high mountains of the eastern cordillera where small glaciers are a significant source of sediment in most of the lake sediment is 0 to 40 m thick reaching a maximum of just over 100 m thick near the junction of the three arms cores from three locations in the lake provide evidence that the entire holocene record is contained in the upper 4 to 6 m of the sedimentary record where rates of accumulation have been constant or have decreased slowly the highest rates 0 35 to 0 72 mm a occur near points of inflow while the lowest rate 0 22 mm a occurs in a sheltered environment with limited inflow and significant hypolimnic circulation which may flush water and suspended sediment from the water column late pleistocene sediment beneath has a similar acoustic signature to the cored holocene record above suggesting that the sedimentary processes governing its deposition were not greatly different than in the present lake but that extensive glacial and paraglacial sources contributed to a significantly higher rate of accumulation mazama ash analyzed from two locations near points of inflow has an age of 7576 60 cal bp according to our chronology vivianite which is uncommon in lakes of the cordillera occurs in the middle of the cores mainly associated with macroscopic wood fragments and indicates reducing conditions within the sediment

active faulting offshore se spain alboran sea implications for earthquake hazard assessment in the southern iberian margin the southern margin of the iberian peninsula hosts the convergent boundary between the european and african plates the area is characterised by low to moderate magnitude shallow earthquakes although large historical events have also occurred in order to determine the possible sources of these events we recently acquired swath bathymetry tobi sidescan sonar and high resolution seismic data on the almeria margin eastern alboran sea the new dataset reveals the offshore continuation of the ne sw trending carboneras fault a master fault in the eastern betic shear zone and its associated structures n150 and ns faults these structures are active since they cut the late quaternary sedimentary units the submarine carboneras fault zone is 100 km long 5 10 km wide and is divided into two n045 and n060 segments separated by an underlapping restraining stepover geomorphic features typically found in subaerial strike slip faults such as deflected drainage water gaps shutter ridges pressure ridges and ben echelonq folds suggest a strike slip motion combined with a vertical component along the submarine carboneras fault considering the nnw sse regional shortening axis a left lateral movement is deduced for the carboneras fault whereas right lateral and normal components are suggested for the associated n150 and ns faults respectively the offshore portion of this fault is at least twice as long as its onshore portion and together they constitute one of the longest structures in the southeastern iberian margin despite the fact that present day seismicity in the almeria margin seems to be associated with the n150 to ns faults the carboneras fault is a potential source of large magnitude mw 7 2 events hence the carboneras fault zone could pose a

heterogeneity in southern central indian ridge morb implications for ridge hot spot interaction between the rodrigues triple junction and the marie celeste fracture zone basalts from the central indian ridge cir exhibit an enrichment in incompatible elements that increases in intensity northward in addition h2o tio2 al 8 and dy yb ratios increase while na 8 remains unchanged and fe 8 decreases evolution of the enriched magma appears to be affected by elevated water contents which lower the mantle solidus thereby increasing the initial depth of melting as well as delaying plagioclase crystallization however the enrichment affecting the northern samples is not a just function of hydrous mantle melting and crystallization instead of trending toward a small melt fraction from the mantle as predicted by hydrous melting models the cir samples lie on a mixing line between n morb and a source component that closely resembles present day reunion hot spot lavas thus it appears that while hydrous melting and crystallization affect the cir the enriched and wet mantle originates from the reunion hot spot where it migrates eastward toward the cir against the direction of motion of the lithosphere

bayesian modelling of an absolute chronology for egypt s 18th dynasty by astrophysical and radiocarbon methods only a few astrophysical points and synchronisms listed in texts provide anchor points for the absolute chronology of ancient egypt at first we will show how we can re calculate some of these anchor points by using sothic dating based on the arcus visionis method and modelling lunar dates using a bayesian approach then we will discuss two radiocarbon studies carried out on short lived egyptian materials held at the louvre museum that could be attributed to particular reigns or other precise periods using a bayesian approach these dates were combined with the known order of succession and the lengths of reigns sothic and lunar dates were integrated as priors in the model this approach has led to a new proposal for the absolute chronology of egypt s 18th dynasty

new dates for first millennium bc tephra isochrones in ireland three distinct first millennium bc tephras bmr 190 omh 185 gb4 150 have been recognized in irish peat deposits including a previously undated ash bmr 190 we present the results of a programme of high precision 14c wiggle matching on a peat profile containing all three tephras from glen west county fermanagh northern ireland the wiggle match provides highly refined dates of 705 585cal bc for bmr 190 755 680cal bc for omh 185 and 800 758cal bc for gb4 150 the tephras constitute valuable widespread isochrones for palaeoecological research across the first millennium bc when a prolonged 14c calibration plateau between 750 and 400 cal bc presents a major problem to dating and correlating palaeoenvironmental events from multisite multiproxy studies of the period

runoff and soil erosion under rainfall simulation of andisols from the ecuadorian paramo effect of tillage and burning abstract in northern ecuador soils of high altitude grasslands paramos are mainly non allophanic andisols developed on holocenic volcanic ash these soils have a high water retention capacity and are the water tank of central ecuador to assess the effect of land use burning and tillage on soil hydrodynamic properties rainfall simulation was conducted at two different sites at pichincha near quito the simulation was conducted on a recent volcanic ash soil comparing natural tilled and burned plots at el angel the simulation was conducted on a mature non allophanic andisol comparing natural recently tilled and formerly cultivated plots on natural plots the infiltration rate was very high and sediment loss very low results for infiltration rate and runoff indicated that land use change on paramos increased runoff flow and reduced saturated hydraulic conductivity superficial reorganisation of the soil surfaces occurred on tilled plots at both sites this crusting process was fast and resulted in surfaces with very low conductivity at pichincha the same processes seemed to be slower at el angel the soil surface of recent andisols at pichincha was prone to crusting whereas the mature andisol at el angel with a lower bulk density was compacted when the kinetic energy of raindrops was high water repellency occurred after burning at pichincha and following long natural air drying after tillage in the non allophanic a horizon at el angel water repellency combined with the low bulk density of soil aggregates explain the intensity of sediment losses in the abandoned soils after cultivation bare fallow plots erosion occurred in these areas through floating hydrophobic and stable aggregates

surface deformation associated with the mw 6 4 24 february 2004 al hoceima morocco earthquake deduced from insar implications for the active tectonics along north africa we study the surface deformation associated with the 24 february 2004 al hoceima earthquake mw 6 4 that recently affected the rif mountains of mo rocco the coseismic displacement field is mapped using synthetic aperture radar interferometry insar with the envisat esa satellite data acquired in the ascend ing and descending modes our analysis and modeling of insar data suggest that the earthquake is associated with a northwest southeast trending right lateral ap parently blind strike slip fault with a seismic moment reaching 6 8 10 18 n m this result is in contrast with the north northeast south southwest left lateral fault mech anism inferred from the modeling of seismic waves thrust and fold structures of the rif mountains developed during the tertiary period but the recent significant seismic events and late quaternary deformation indicate east west extension accom modated by north south trending normal and northwest southeast and northeast southwest trending conjugate strike slip faults the active deformation illustrates the fragmentation of the rif mountain range due to the africa iberia collision and west southwestward escape tectonics

comparison of conventional k ar and 40ar 39ar dating of young mafic volcanic rocks abstract k ar and 40ar 39ar ages have been measured on nine mafic volcanic rocks younger than 1 myr from the snake river plain idaho mount adams washington and crater lake oregon the k ar ages were calculated from ar measurements made by isotope dilution and k2o measurements by flame photometry the 40ar 39ar ages are incremental heating experiments using a low blank resistance heated furnace the results indicate that high quality ages can be measured on young mafic volcanic rocks using either the k ar or the 40ar 39ar technique the precision of an 40ar 39ar plateau age generally is better than the precision of a k ar age because the plateau age is calculated by pooling the ages of several gas increments the precision of a plateau age generally is better than the precision of an isotope correlation isochron age for the same sample for one sample the intercept of the isochron yielded an 40ar 36ar value significantly different from the atmospheric value of 295 5 recalculation of increment ages using the isochron intercept for the composition of nonradiogenic ar in the sample resulted in much better agreement of ages for this sample the results of this study also indicate that given suitable material and modern equipment precise k ar and 40ar 39ar ages can be measured on volcanic rocks as young as the latest pleistocene and perhaps even the holocene

source analysis of the mw 6 3 2004 al hoceima earthquake morocco using regional apparent source time functions 1 we use small and moderate aftershocks of the 24 february 2004 al hoceima earthquake as empirical greens functions egfs to retrieve the rupture history of the main event the magnitude depth and geometry of faulting were estimated for the main shock and 20 small and moderate aftershocks mw between 3 9 and 5 2 computing moment tensor solutions for the main shock we obtain a moment magnitude of mw 6 3 and a nearly pure double couple source 4 compensated linear vector dipole with predominately strike slip faulting the preferred fault plane has a strike of n11 e a dip of 72 and a rake of 17 fourteen aftershocks having depths 4 km and faulting geometries 11 for the strike of the preferred plane similar to the ones found for the main event were used as egfs apparent source time functions astfs of the al hoceima event were retrieved at twelve regional stations using an iterative time domain deconvolution on the p waveforms at each station time functions are enhanced by stacking of the deconvolved waveforms for different egfs astfs show total durations of 5 to 6 s two consecutive subevents separated by about 3 s and only a weak effect of directivity we further investigate the source history by inverting the set of astfs for the distribution of fault slip and rupture propagation two different source models were selected for presentation one involving one single fault plane and the other involving two parallel fault planes the two fault model fits more accurately the observations and leads to a more plausible slip distribution we estimate rupture dimensions of about 10 10 km2 and 8 8 km2 and moment magnitudes of mw 6 2 and 6 0 for the first and second subevent respectively

the alboran sea western mediterranean revisited with a view from the moroccan margin this paper presents a new depth to acoustic basement map based on a grid of seismic profiles in the western alboran basin the basement is more than 10 km deep an examination of a seismic profile of this region suggests that late oligocene early miocene 5 km thick synrift formation has been accumulated in this basin this west alboran basin has been formed in an extensional setting but in a fore arc position south of the balearic islands then westwards transported behind a subduction zone

influence of soil surface features and vegetation on runoff and erosion in the western sierra madre durango northwest mexico abstract in mountainous areas runoff and soil erosion are closely linked to soil surface features particularly stoniness depending on the size of rock fragments gravel pebbles stones and or blocks and especially the way they are integrated into the soil matrix they may facilitate or hinder infiltration and promote soil losses the present study examines the role of different soil surface features and their influence on runoff formation and on soil erosion in an area seriously affected by overgrazing based on measurements made on hillslopes for 2 years at the plot scale the results show that grass cover pebbles and sand content increase runoff and erosion inversely slope value tree cover percentage structural stability and organic matter content are negatively correlated with runoff and soil losses it is shown that the correlations can be explained by the major role played by the surface features on hydrologic behaviour of the hillslopes two main surface features were identified and hydraulically characterised namely i crusted surfaces with embedded gravel widespread on gentle slopes which induce high runoff and erosion rates and ii stony surfaces where free pebbles and blocks protect the top soil against raindrops and overland flow kinetic energy and lead to reduce runoff and soil losses

the effects of soil texture and ash thickness on the post fire hydrological response from ash covered soils summary ash increases the post fire hydrological response to rainfall in some situations but decreases it in others and the reasons for this variability are not well defined we used simulated rainfall experiments to determine whether the varying hydrological effect of ash can be attributed to differences in the underlying soil texture or the ash thickness we compared the infiltration rates 1 before and after controlled burns in 0 5 m2 plots underlain by two sharply contrasting soil textures sandy loam and gravelly silt loam and 2 before and after the addition of 0 5 2 5 and 5 0 cm of ash to the burned sandy loam plots with the original ash layer removed the controlled burns left a 1 cm ash layer comprised mostly of silt and fine sand particles that clogged the largest pores in the sandy loam soil reducing the final infiltration rate from 91 mm h 1 to 35 mm h 1 but had no effect on infiltration in the silt loam plots pore clogging also reduced the final infiltration rate by 20 mm h 1 40 and the total infiltration by 16 mm 24 when 0 5 cm of ash was added to the sandy loam plots however increased storage in the ash layer combined with slight increases in the final infiltration rate by 5 and 18 mm h 1 respectively increased the total infiltration by 16 mm 30 and 18 mm 26 respectively with the thicker ash addition treatments thus the varying effect of ash on infiltration and runoff can be at least partially attributed to between site differences in soil texture and ash thickness a thin ash layer

infiltration runoff and soil loss in andisols affected by forest fire canary islands spain depending on the severity of the fire forest fires may modify infiltration and soil erosion processes rainfall simulations were used to determine the hydrological effects of fire on andisols in a pine forest burned by a wildfire in 2007 six burned zones with different fire severities were compared with unburned zones infiltration runoff and soil loss were analysed on slopes of 10 and 30 forest floor and soil properties were evaluated unburned zones exhibited relatively low infiltration 23 and 16 mm h 1 on 10 and 30 slope angles respectively and high average runoff rainfall ratios 43 and 50 on 10 and 30 slope angles respectively which were associated with the extreme water repellency of the forest floor nonetheless this layer seems to provide protection against raindrop impact and soil losses were found to be low 8 and 16 g m 2 h 1 for 10 and 30 slope angles respectively soil cover soil structure and water repellency were the main properties affected by the fire the fire reduced forest floor and soil repellency allowing rapid infiltration moreover a significant decrease was noted in soil aggregate stabilities in the burned zones which limited the infiltration rates consequently no significant differences in infiltration and runoff were found between the burned and the unburned zones the decrease in post fire soil cover and soil stability resulted in order of magnitude increases in erosion sediment rates were 15 and 31 g m 2 h 1 on the 10 and 30 slope angles respectively in zones affected by light fire severity in the moderate fire severity zones these values reached 65 and 260 g m 2 h 1 for the 10 and 30 slope angles respectively copyright 2012 john wiley sons ltd

late pleistocene holocene history of a tectonically active segment of the continental margin nekor basin western mediterranean morocco abstract in active basins tectonics can segment the continental shelf and control its stratigraphic architecture and physiography segmentation can explain the local evolution and morphology of the continental shelf because of sea level variations local tectonic segmentation and hydrodynamic processes here we investigate the tectonically active morocco continental margin southern alboran sea using high resolution seismic profiles and multibeam bathymetric data the active faults bounding the transtensive nekor basin triggered the segmentation of the shelf into three sectors showing different subsidence rates a western sector corresponding to an extensive fault relay a central sector corresponding to the subsiding al hoceima bay and an eastern sector corresponding to the footwall of the trougout senestral normal fault results show that the staircase morphology of the shelf corresponds to successive submarine terraces at the shelf edge st1 mid shelf st2 and inner shelf st3 around 110 m 80 m and 40 to 20 m deep respectively the terraces correspond to the top of prograding wedges seaward and are erosive landward they are correlated with stillstand from the last glacial maximum to the holocene highstand above the terraces sub aqueous dune fields are interpreted as degraded and deposited during the post glacial transgression in the central sector typical delta front seafloor undulations on the shelf and crescent shaped bedforms at the head of marine incisions on the upper slope denote a fluvial influence during the holocene seismic stratigraphy analysis revealed the preservation of six seismic units bounded by polygenic regional unconformities s1 s2 s3 s4 and s5 based on comparison with other mediterranean margins s1 to s5 are attributed to 4th order maximum regressive surface we discuss the local preservation of the system tracts as a function of the vertical motion and the physiography of this tectonically active domain this study provides useful clues for future local paleo seismic analysis and to advance our understanding of sedimentary processes in active areas

a high precision age estimate of the holocene plinian eruption of mount mazama oregon usa the climactic eruption of mount mazama in oregon north america resulted in the deposition of the most widespread holocene tephra deposit in the conterminous united states and south western canada the tephra forms an isochronous marker horizon for palaeoenvironmental sedimentary and archaeological reconstructions despite the current lack of a precise age estimate for the source eruption previous radiocarbon age estimates for the eruption have varied and greenland ice core ages are in disagreement for the mazama tephra to be fully utilised in tephrochronology and palaeoenvironmental research a refined precise and accurate age for the eruption is required here we apply a meta analysis of all previously published radiocarbon age estimations n 81 and perform bayesian statistical modelling to this data set to provide a refined age of 7682 7584 cal yr bp 95 4 probability range although the depositional histories of the published ages vary this estimate is consistent with that estimated from the gisp2 ice core of 7627 150 yr bp zdanowicz et al 1999

dating the glen garry tephra a widespread late holocene marker horizon in the peatlands of northern britain the distal icelandic tephra known as the glen garry layer has been dated by ams 14c at eight ombrotrophic peat bogs from northern england and scotland the geochemistry of all the tephra layers is consistent with there being only one glen garry tephra rather than two or more from eruptions of the same volcanic source at seven of the sites all in scotland the tephra layer was bracketed by 1 cm contiguous samples below at and above the horizon at the one english site walton moss cumbria a suite of 16 ams dates was applied to a 116 cm section of a peat core containing the tephra the resulting dates were calibrated and wiggle matched using the bcal and bpeat programmes to give an estimated age for the glen garry tephra of 2176 cal bp with a 2 range of 2210 1966 cal bp this 244 year range is an improvement on the 410 years calibrated date range for the date without the wiggle match this age estimate will allow future work on peat profiles and other sediments containing the tephra to use the date as a pinning point in age depth models and obviate the need for radiocarbon dating at this period

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

fault identification for buried strike slip earthquakes using insar the 1994 and 2004 al hoceima morocco earthquakes summary the 1994 m w 6 0 and 2004 m w 6 5 al hoceima earthquakes are the largest to have occurred in morocco for 100 yr and give valuable insight into the poorly understood tectonics of the area bodywave modelling indicates the earthquakes occurred on near vertical strike slip faults with the nodal planes oriented nw se and ne sw distinguishing between the primary fault plane and auxiliary planes using either geodetic or seismic data is difficult due to the spatial symmetry in deformation fields and radiation pattern of moderately sized buried strikeslip earthquakes preliminary studies using aftershock locations and surface observations have been unable to identify the orientation of the primary fault plane for either earthquake conclusively we use radar interferometry and aftershock relocation of the earthquake sequence to resolve the ambiguity for the 2004 earthquake inverting the interferograms for a uniform slip model based either of the two potential nodal planes results in similar misfits to the data however the ne sw best fit fault plane has an unrealistically high fault slip to length ratio and we conclude the nw se striking nodal plane is the primary fault plane and slip was right lateral we carry out tests on synthetic data for a buried strike slip earthquake in which the orientation of the fault plane is known a priori independent of geometry missing data and correlated noise models produced assuming the auxiliary plane to be the fault plane have very high fault slip to length ratios the 1994 earthquake had a smaller magnitude and comparisons of model misfits and slip to length ratios do not conclusively indicate which of the nodal planes is the primary fault plane nonetheless the insar data provides valuable information by improving the accuracy of the earthquake location by an order of magnitude we carry out a multiple event relocation of the entire earthquake sequence including aftershocks making use of the absolute locations for the 1994 and 2004 main shocks from our insar study the aftershock locations are consistent with a nw se orientated fault plane in 2004 and suggests that the 1994 earthquake occurred on a ne sw fault perpendicular to the fault which ruptured in 2004 previous tectonic models of the area proposed a bookshelf model of block rotation with nne ssw left lateral faults this model requires modification to accommodate the observation of right lateral slip on a nw se fault plane for the 2004 earthquake and we prefer to interpret the fault orientations as due to a zone of distributed shear with a right lateral fault striking at 115 and conjugate clockwise rotating left lateral faults striking at 25

were there two borrobol tephras during the early lateglacial period implications for tephrochronology abstract a series of ams radiocarbon measurements of terrestrial plant macrofossil remains are presented from a lake sequence in southernmost sweden in an attempt to constrain the age of the borrobol tephra this recently identified ash layer has been frequently suggested as a potentially significant marker horizon for assessing the precise timing of the initial warming in different parts of europe at the start of greenland interstadial 1 gi 1 two different methods are adopted in order to derive a calendar age estimate for this event an age of ca 13 900 cariaco varve yrs bp is derived from a visual wiggle match of the age series to the cariaco basin data set the second approach is based on bayesian probability analysis and constrains the age of the borrobol tephra in southern sweden to between 13 800 14 450 and 13 667 14 331 cal yrs bp 95 confidence using the cariaco and lake suigetsu records as calibration data sets respectively these new age depth models together with the pollen stratigraphy suggest that the borrobol tephra as found in southern sweden falls within the late older dryas gi 1d or the early allerod gi 1c whereas other european sequences indicate that this tephra falls close to the gs 2 gi 1 transition whether or not this indicates that the different occurrences of the bt in northern europe are coeval is discussed and the implications that arise for the application of tephrochronology during this period are outlined

new accelerator mass spectrometry radiocarbon ages for the mazama tephra layer from kootenay national park british columbia canada charcoal fragments recovered from the mazama air fall tephra layer in cores from dog and cobb lakes kootenay national park british columbia yielded accelerator mass spectrometry ages of 6720 70 and 6760 70 14c years bp respectively these two new ages together with other previously published radiocarbon ages on charcoal and twig fragments from mazama air fall deposits indicate that the climactic eruption of mount mazama occurred 6730 40 14c years bp

a revised age for the kawakawa oruanui tephra a key marker for the last glacial maximum in new zealand abstract the kawakawa oruanui tephra kot is a key chronostratigraphic marker in terrestrial and marine deposits of the new zealand nz sector of the southwest pacific erupted early during the last glacial maximum lgm the wide distribution of the kot enables inter regional alignment of proxy records and facilitates comparison between nz climatic variations and those from well dated records elsewhere we present 22 new radiocarbon ages for the kot from sites and materials considered optimal for dating and apply bayesian statistical methods via oxcal4 1 7 that incorporate stratigraphic information to develop a new age probability model for kot the revised calibrated age 2 standard deviations for the eruption of the kot is 25 360 160 cal yr bp the age revision provides a basis for refining marine reservoir ages for the lgm in the southwest pacific

active tectonics of the western mediterranean geodetic evidence for rollback of a delaminated subcontinental lithospheric slab beneath the rif mountains morocco surface deformation in morocco derived from five years of global positioning system gps survey observations of a 22 station network four continuously recording gps cgps stations and four international gnss service igs stations in iberia indicates roughly southward motion 3 mm yr of the rif mountains morocco relative to stable africa motion of the rif is approximately normal to the direction of africa eurasia relative motion which is predominantly strike slip and results in shortening of the rif and subsequent crustal extension of the adjacent alboran sea region the sense and the n s asymmetry of the observed deformation i e no evidence for north directed shortening in the betic mountains north of the alboran sea cannot be easily explained in terms of crustal plate interactions suggesting that dynamic processes below the crust are driving the recent geologic evolution of the western mediterranean the model that best fits the observations involves delamination and southward rollback of the african lithospheric mantle under the alboran and rif domains

erodibility and runoff infiltration characteristics of volcanic ash soils along an altitudinal climosequence in the ecuadorian andes abstract soil erosion is a widespread phenomenon in andean south america where many regions are covered with soils derived from volcanic parent materials climate induced differences in the genesis of these soils have been demonstrated along toposequences on volcanic slopes this research was conducted to study the impact of such differential pedogenesis on erodibility and runoff infiltration characteristics along an altitudinal entisols inceptisols andisols sequence in the andes of northern ecuador surface soils were packed into small pans and placed on a 9 slope and a simulated rainstorm with varying intensities was applied for a duration of 30 min the runoff erosion behaviour of the studied volcanic ash soils is strongly affected by their pedological development accumulation of organic matter and precipitation of active amorphous materials at high elevations have led to the formation of well developed andisols with very stable aggregate structure these soils remain wettable when air dried show very high infiltration capacity and consequently low potential for runoff generation and soil erosion low organic matter contents and absence of active amorphous materials at low elevations have led to the formation of weakly aggregated entisols and inceptisols these soils are susceptible to surface crusting which lowers their infiltration capacity and increases their erodibility however in comparison with other soils of different origin and composition the interrill erodibilities determined for these more erodible low elevation soils are classified as low the findings of this study suggest that upland soil erosion is not a major threat to sustainability in the studied volcanic landscape which is generally confirmed by field observations

crustal types and tertiary tectonic evolution of the alboran sea western mediterranean multichannel seismic reflection images across the transition between the east alboran and the algero balearic basins show how crustal thickness decreases from about 5 s two way traveltime twtt 15 km thick in the west east alboran basin to 2 s twtt typical of oceanic crust 6 km thick in the east algero balearic basin we have differentiated three different crustal domains in this transition mainly on the basis of crustal thickness and seismic signature boundaries between the three crustal domains are transitional and lack evidence for major faults tilted blocks related to extension are very scarce and all sampled basement outcrops are volcanic suggesting a strong relationship between magmatism and crustal structure stratigraphic correlation of lithoseismic units with sedimentary units of southeastern betic basins indicates that sediments onlap igneous basement approximately at 12 ma in the eastern area and at 8 ma in the western area linking seismic crustal structure with magmatic geochemical evidence suggests that the three differentiated crustal domains may represent from west to east thin continental crust modified by arc magmatism magmatic arc crust and oceanic crust middle to late miocene arc and oceanic crust formation in the east alboran and algero balearic basins respectively occurred during westward migration of the gibraltar accretionary wedge and shortening in the betic rif foreland basins arc magmatism and associated backarc oceanic crust formation were related to early to middle miocene subduction and rollback of the flysch trough oceanic basement subduction of this narrow slab beneath the alboran basin was coeval with collision of the alboran domain with the iberian and african passive margins and subsequent subcontinental lithosphere edge delamination along the betic rif margins

effect of forest floor characteristics on water repellency infiltration runoff and soil loss in andisols of tenerife canary islands spain abstract given its singular properties and location forest floor litter duff is a key factor in hydrological processes water infiltration research was carried out for the present study in andisols at ten sites six of which had coverings of pine forest and four of rainforest rainfall simulations were conducted on gentle moderately steep and steep slopes 10 30 and 50 to determine infiltration runoff and soil loss as a function of the forest floor characteristics the duff on the pine forest soils consists of moderately porous extremely hydrophobic and consistent semi decomposed organic material which is rich in fungi hyphae the duff on the rainforest soils is formed by highly porous loose semi decomposed organic material the study results highlight the influential role played by the forest floor in infiltration and runoff infiltration barely reaches 20 mm h 1 in pine forest compared to 50 mm h 1 in rainforest as a consequence the pine forest runoff is twice that recorded in rainforest sites the wetting front on gentle and moderately steep slopes evidences the influence of the duff on infiltration in pine forest most of the rainwater remains in the duff and infiltration depends little therefore on the underlying mineral soil properties in rainforest the wetting front extends below the duff and the well developed soil structure is a major factor in water infiltration the differences noted in the two parameters are not found on the steep slopes no soil loss differences are observed between the two vegetation covers and forest floors despite the greater runoff in pine forest the results demonstrate the protective effect of the organic covering and how the stability of the andisols helps combat water erosion processes

laacher see tephra a widespread isochronous late quaternary tephra layer in central and northern europe a late quaternary tephra layer widespread in central and northern europe resulted from explosive plinian and phreatomagmatic eruptions of the laacher see volcano 11 000 yr b p the tephra is distinguished from other late quaternary andesitic rhyolitic airfall tuff layers in northern europe and from basaltic or trachytic tuff deposits in southern europe by its phonolitic composition and abundance of sanidine plagioclase clinopyroxene amphibole and sphene the proximal tephia sequence at laacher see is divided into three main deposits the predominantly plinian deposits of lower and middle laacher see tephra llst and mlst and phreatomagmatic deposits of the upper laacher see tephra ulst the mlst member is further subdivided into beds a b and c1 c2 and c3 the chemical composition of the magma is highly differentiated phonolite in the llst to mlst b sections but mafic phonolite in the mlst c1 to ulst sections all deposits are considered to be isochronous the frequency maximum of 16 radiocarbon datings indicating an eruption about 11 000 50 yr b p distal ash was deposited in three main fans directed to the northeast lst traced up to 1 100 km distance south lst traced up to 600 km and southwest lst traced up to 100 km tephrostratigraphic correlation of the distal ash deposits is based on a the major element composition of glass shards b lithology and c heavy mineral analyses the northeastern fan consists of deposits from llst mlst b and mlst c1 eruptive phases the southern fan comprises mlst a mlst c2 and ulst deposits and the southwestern fan consists exclusively of ash from the ulst eruptive phase northeastern transport of ash during eruptive phases with high plinian eruption columns but southern and southwestern transport of ash along phases of relatively low eruption columns are interpreted in terms of prevailing southwesterly paleowinds at high altitudes tropopause level but northerly winds dominating in the lower atmosphere the laacher see eruption columns were emplaced into an atmosphere vertically zoned with respect to paleowind directions which also explains the near vent shifting of llst mlst b and mlst c1 iso pach axes from east southeast to northeast within the first 20 km of transport

a record of late quaternary vegetation from davis lake southern puget lowland washington abstract pollen and macrofossil analyses of a core spanning 26 000 yr from davis lake reveal late pleistocene and holocene vegetational patterns in the puget lowland the core ranges lithologically from a basal inorganic clay to a detritus gyttja to an upper fibrous peat and includes eight tephra units the late pleistocene pollen sequence records two intervals of tundra parkland vegetation the earlier of these has high percentages of picea gramineae and artemisia pollen and represents the vegetation during the evans creek stade fraser glaciation ca 25 000 17 000 yr b p the later parkland interval is dominated by picea tsuga mertensiana and gramineae it corresponds to the maximum ice advance in the puget lowland during the vashon stade fraser glaciation ca 14 000 yr b p an increase in pinus ontorta pollen between the two tundra parkland intervals suggests a temporary rise in treeline during an unnamed interstade after 13 500 yr b p a mixed woodland of subalpine and lowland conifers grew at davis lake during a period of rapid climatic amelioration in the early holocene the prolonged expansion of pseudotsuga and alnus woodland suggests dry temperate conditions similar to those of present rainshadow sites in the puget lowland more mesic forests of tsuga eterophylla thuja plicata and pseudotsuga similar to present lowland vegetation appeared in the late holocene ca 5500 yr b p

new gps constraints on active deformation along the africa iberia plate boundary abstract we use velocities from 65 continuous stations and 31 survey mode gps sites as well as kinematic modeling to investigate present day deformation along the africa iberia plate boundary zone in the western mediterranean region the gps velocity field shows southwestward motion of the central part of the rif mountains in northern morocco with respect to africa varying between 3 5 and 4 0 mm yr consistent with prior published results stations in the southwestern part of the betic mountains of southern spain move west southwest with respect to eurasia 2 3 mm yr the western component of betics motion is consistent with partial transfer of nubia eurasia plate motion into the southern betics the southward component of betics motion with respect to iberia is kinematically consistent with south to southwest motion of the rif mountains with respect to africa we use block modeling constrained by mapped surface faults and seismicity to estimate the geometry and rates of strain accumulation on plate boundary structures our preferred plate boundary geometry includes one block between iberia and africa including the sw betics alboran sea and central rif this geometry provides a good fit to the observed motions suggesting a wide transpressive boundary in the westernmost mediterranean with deformation mainly accommodated by the gloria azores fault system to the west and the rif tell lineament to the east block boundaries encompass aspects of earlier interpretations suggesting three main deformation styles i extension along the ne sw trending trans alboran shear zone ii dextral strike slip in the betics corresponding to a well defined e w seismic lineament and iii right lateral strike slip motion extending west to the azores and right lateral motion with compression extending east along the algerian tell we interpret differential motion in the rif alboran betic system to be driven both by surface processes related the africa eurasia oblique convergence and sub crustal dynamic processes associated with the long history of subduction of the neotethys ocean lithosphere the dextral slip identified in the betic mountains in southern spain may be related to the offshore fault that produced the great 1755 lisbon earthquake and as such may represent a significant seismic hazard for the west mediterranean region

microearthquake seismicity and fault plane solutions around the nekor strike slip fault morocco abstract three hundred and twenty eight earthquakes recorded in the course of 5 weeks in 1989 in the central rif of northern morocco provided no evidence for activity on the nekor fault the principal geological structure in the region itself most of the seismicity is located northwest of the nekor fault most of the 41 fault plane solutions show mainly strike slip motion left lateral on n s striking planes with p axes trending n145 this deformation is consistent with the n s trending normal faults caused by the e w quaternary extension and with the present relative nw se convergence between africa and europe the active deformation around the eastern rif is better represented by a distributed shear zone than by a strike slip fault

extensional tectonics graben development and fault terminations in the eastern rif bokoya ras afraou area abstract westward motion of the alboran domain between the eurasian and african plate boundaries determined crustal thickening along the southern border of the gibraltar arc forming the rif cordillera this process developed major sinistral ne sw to ene wsw faults such as the nekor fault inactive since the late miocene however the neogene quaternary boudinar and nekor basins underwent very intense recent tectonic and seismic activity related to n s faults kinematics of this fault set changes with depth while at 10 km faults have a sinistral strike slip kinematics they become normal to normal oblique at surface sfeha trougout and boudinar faults their different kinematics could be explained by the existence of a crustal detachment separating two differently pre structured domains shallow transtensive n s faults trend orthogonal to the coastline decreasing their slip southwards until disappearing paleostress analysis shows a progressive change from e w extension near the coastline up to radial extension in southern areas of major fault terminations the behavior of each fault bounded block is conditioned by its inherited rheological features the sequence of horsts bokoya ras tarf ras afraou corresponds mainly to resistant rocks volcanics or limestones whereas the grabens nekor and boudinar basins are generally floored by weak metapelites and flysch the presence of liquefaction structures interpreted as seismites underlines the continued recent seismic activity of the region the recent structures deforming the two alboran sea margins come to support the continuity at present of orogenic processes undergone by the eastern internal regions of the gibraltar arc involving regional e w extension in the framework of nw se to n s eurasian african convergence

post fire evolution of water repellency and aggregate stability in mediterranean calcareous soils a 6 year study abstract water repellency wr and aggregate stability as are two soil properties generally modified after burning which show several hydrological and soil functioning consequences and may be used as indices for assessing burn severity both properties are strongly related and have major impacts on soil functioning and post fire hydrologic and geomorphological processes in many cases the impact of fire on these properties has been analyzed in the short term however it is also necessary to investigate the magnitude of these changes and their implications for longer periods under specific conditions in this work we have investigated 1 the fire induced changes on soil wr and as in the medium term 6 year period after burning and its distribution within aggregate size fractions 1 2 0 5 1 and 0 25 0 5 mm 2 the relations between post fire as and wr and 3 the interactions between as wr and different factors site time since burning lithology and vegetation type in mediterranean calcareous soils five areas burned during the summer 2006 in southern spain were selected for this study the study sites were characterized by wettable or slightly water repellent calcareous soils with loam to clayey texture under herbaceous vegetation and shrubs soils were characterized chemically and physically while the wr and as of the fine earth and aggregate sieve fractions were determined annually between 2006 and 2011 results show that soil wr was induced in previously wettable or enhanced in slightly or moderately water repellent calcareous soils after moderate severity burning severity of wr from finer aggregates 0 5 1 and 0 25 0 5 mm varied or remained stable but did not contribute to general soil wr assessed in the fine earth fraction as was slightly increased in some cases and both properties returned progressively to pre fire conditions during the study period soil resilience to low moderate severity burning in the study area was very high

revised 14c age for st helens y tephra at tonquin pass british columbia the age of a mount st helens set y tephra at tonquin pass british columbia previously assumed to be 4300 years bp is revised to ca 3400 years bp based on bracketing 14c dates of 3140 70 beta 13558 and 3680 80 years bp beta 13559 the implications of this revision for tephrostratigraphy of this area are discussed

evidence for active subduction beneath gibraltar we report on a marine seismic survey that images an active accretionary wedge west of gibraltar ramp thrusts offset the seafloor and sole out to an east dipping decollement indicating ongoing westward vergent tectonic shortening new traveltime tomographic re sults image a slab of oceanic lithosphere descending from the atlantic domain of the gulf of cadiz passing through intermediate depth 60 120 km seismicity beneath the west ernmost alboran sea and merging with a region of deep focus earthquakes 600 660 km below granada spain together these new data provide compelling evidence for an active east dipping subduction zone

earthquake fracture energy inferred from kinematic rupture models on extended faults 1 we estimate fracture energy on extended faults for several recent earthquakes by retrieving dynamic traction evolution at each point on the fault plane from slip history imaged by inverting ground motion waveforms we define the breakdown work wb as the excess of work over some minimum traction level achieved during slip wb is equivalent to seismological fracture energy g in previous investigations our numerical approach uses slip velocity as a boundary condition on the fault we employ a three dimensional finite difference algorithm to compute the dynamic traction evolution in the time domain during the earthquake rupture we estimate wb by calculating the scalar product between dynamic traction and slip velocity vectors this approach does not require specifying a constitutive law and assuming dynamic traction to be collinear with slip velocity if these vectors are not collinear the inferred breakdown work depends on the initial traction level we show that breakdown work depends on the square of slip the spatial distribution of breakdown work in a single earthquake is strongly correlated with the slip distribution breakdown work density and its integral over the fault breakdown energy scale with seismic moment according to a power law with exponent 0 59 and 1 18 respectively our estimates of breakdown work range between 4 105 and 2 107 j m2 for earthquakes having moment magnitudes between 5 6 and 7 2 we also compare our inferred values with geologic surface energies this comparison might suggest that breakdown work for large earthquakes goes primarily into heat production

development of asymmetric basins along continental transform faults abstract many basins associated with wrench or transform faults are asymmetrical both longitudinally and laterally the sense of basin asymmetry changes along the strike of transform faults geophysical data from the dead sea rift and other transforms indicate that wrench induced asymmetric basins are bounded on only one side by a transform fault this implies that during the evolution of such basins maximum compression was parallel to the transform the direction of extension can change during the geologic evolution of a basin a possible explanation of this observation takes the strength of the fault into into consideration in the case of a weak fault in a strong crust the horizontal principal stresses would probably rotate to orientations parallel and perpendicular to the fault thus minimizing the shear stress on the main fault basins formed by regional extension such as in the east african rift system sometimes show similar features recent studies have shown that these basins often undergo oblique extension this suggests that the asymmetry in these basins may result from simultaneous strike slip motion and fault normal extension similar to the way asymmetry is produced in large transform basins periods of oblique extension can alternate with periods of orthogonal extension the asymmetry formed during periods of oblique extension is often preserved in the stratigraphic record

icelandic volcanic ash and the mid holocene scots pine pinus sylvestris decline in the north of ireland no correlation tephra linked pollen and dendrochronological studies were performed on mid holocene subfossil peats and pines and two lowland raised bogs in the north of ireland the results demonstrated that at these sites contrary to recent findings in the north of scotland there was no temporal link between the decline in pine pollen and tephra from the eruption of the icelandic volcano hekla h4

fire severity and surface rock fragments cause patchy distribution of soil water repellency and infiltration rates after burning although fire induced soil water repellency swr and its effects on soil hydrology and geomorphology have been studied in detail very few studies have considered the effect of rock fragments resting on the soil surface or partly embedded in soil in this research we have studied the effect of rock fragments on the strength and spatial distribution of fire induced swr at different fire severities a fire affected area was selected for this experiment and classified into different zones according to fire severity unburned low moderate and high and rock fragment cover low 60 during 7 days after fire swr and infiltration rates were assessed in the soil surface covered by individual rock fragments and in the midpoint between two adjacent rock fragments with maximum spacing of 20 cm swr increased with fire severity rock fragments resting on the soil surface increased the heterogeneity of the spatial distribution of fire induced swr swr increased significantly with rock fragment cover in bare areas under moderate and high fire severity but quantitatively important changes were only observed under high fire severity in areas with a low rock fragment cover water repellency from soil surfaces covered by rock fragments increased relative to bare soil surfaces with increasing swr in areas with a high rock fragment cover swr increased significantly from non covered to covered soil surfaces only after low severity burning rock fragment cover did not affect infiltration rates although it decreased significantly in soil surfaces after high severity burning in areas under low and high rock fragment cover copyright 2013 john wiley sons ltd

eruptive history and geochronology of mount mazama and the crater lake region oregon geologic mapping k ar and 40 ar 39 ar age determinations supplemented by paleomagnetic measurements and geochemical data are used to quantify the quaternary volcanic history of the crater lake region in order to define processes and conditions that led to voluminous explosive eruptions the cascade arc volcano known as mount mazama collapsed during its climactic eruption of 50 km 3 of mainly rhyodacitic magma 7700 yr ago to form crater lake caldera the mazama edifice was constructed on a pleistocene silicic lava field amidst monogenetic and shield volcanoes ranging from basalt to andesite similar to parental magmas for mount mazama between 420 ka and 35 ka mazama produced medium k andesite and dacite in 2 1 proportion the edifice was built in many episodes some of the more voluminous occurred approximately coeval with volcanic pulses in the surrounding region and some were possibly related to deglaciation following marine oxygen isotope stages mis 12 10 8 6 5 2 and 2 magmas as evolved as dacite erupted many times commonly associated with or following voluminous andesite effusion establishment of the climactic magma chamber was under way when the first preclimactic rhyodacites vented ca 27 ka the silicic melt volume then grew incrementally at an average rate of 2 5 km 3 k y 1 for nearly 20 k y the climactic eruption exhausted the rhyodacitic magma and brought up crystal rich andesitic magma mafic cumulate mush and wall rock granodiorite postcaldera volcanism produced 4 km 3 of andesite during the first 200 500 yr after collapse followed at ca 4800 yr b p by 0 07 km 3 of rhyodacite the average eruption rate for all mazama products was 0 4 km 3 k y 1 but major edifice construction episodes had rates of 0 8 km 3 k y 1 the long term eruption rate for regional monogenetic and shield volcanoes was d 0 07 km 3 k y 1 but only 0 02 km 3 k y 1 when the two major shields are excluded plutonic xenoliths and evidence for crystallization differentiation imply that the amount of magma intruded beneath mount mazama is several times that which has been erupted the eruptive and intrusive history reflects competition between 1 crystallization driven by degassing and hydrothermal cooling and 2 thermal input from a regional magma flux focused at mazama before ca 30 ka relatively small volumes of nonerupted derivative magma crystallized to form a composite pluton because the upper crust had not been heated sufficiently to sustain voluminous convecting crystal poor melt subsequently and perhaps not coincidentally during mis 2 a large volume of eruptible silicic magma accumulated in the climactic chamber probably because of heating associated with mantle input to the roots of the system as suggested by eruption of unusually primitive magnesian basaltic andesite and tholeiite west of mazama

radiocarbon dating of pollen by accelerator mass spectrometry radiocarbon dating of bulk sediments has been the standard method for establishing chronologies in the studies of lake sediment cores which have contributed significantly to our knowledge of late quaternary paleo environments these bulk sediment dates are presumed to be direct ageindicators for the speciments e g pollen or macrofossils which are actually being studied however several recent studies have reinforced long standing apprehensions concerning this presumption in this study we demonstrate for the first time the radiocarbon dating of pollen concentrate samples by accelerator mass spectrometry the dates obtained by this method should provide more reliable radiocarbon chronologies for paleo environmental studies than have been obtainable by bulk sediment dating

deposition models for chronological records abstract long term sedimentary sequences provide a wealth of useful information for research into the palaeo environment especially in relation to past climate change shorter records provide similar information in many archaeological contexts however if such records are to be used to provide precise timing of events and more critically the relative timing between different records methods are needed to provide accurate and precise age depth models for these sequences given the imprecision of individual calibrated radiocarbon determinations it is necessary to use the information we have about the deposition process to refine our chronologies and also to provide interpolation between dated levels in any sequence even with layer counted chronologies the uncertainties are sometimes hard to quantify this paper outlines a range of bayesian models for deposition which have been implemented in the computer programme oxcal these models can be used to combine information from the sediments themselves with radiocarbon or other direct dating information such models have the potential to integrate information between different records and provide a coherent chronology on which to base environmental or archaeological research