solar cycles and depositional processes in annual be 10 from two varved lake sediment records beryllium 10 concentrations be 10 con were measured at annual resolution from varved sediment cores of lakes tiefer see tsk and czechowskie jc for the period 1983 2009 similar to solar cycles 22 and 23 calibrating the be 10 con time series against complementing proxy records from the same archive as well as local precipitation and neutron monitor data reflecting solar forced changes in atmospheric radionuclide production allowed i identifying the main depositional processes and ii evaluating the potential for solar activity reconstruction be 10 con in tsk and jc sediments are significantly correlated to varying neutron monitor counts tsk r 0 5 p 0 05 n 16 jc r 0 46 p 0 03 n 22 however the further correlations with changes in organic carbon contents in tsk as well as varying organic carbon and detrital matter contents in jc point to catchment specific biases in the 10be con time series in an attempt to correct for these biases multiple regression analysis was applied to extract an atmospheric be 10 production signal be 10 atmosphere to increase the signal to noise ratio a be 10 composite record be 10 composite was calculated from the tsk time series be 10 composite and jc be 10 atmosphere is significantly correlated to variations in the neutron monitor record r 0 49 p 0 01 n 25 and matches the expected amplitude changes in 10be production between solar cycle minima and maxima this calibration study on 10be from two sites indicates the large potential but also partly site specific limitations of be 10 in varved lake sediments for solar activity reconstruction c 2015 elsevier b v all rights reserved less

10be inventories in alpine soils and their potential for dating land surfaces abstract to exploit natural sedimentary archives and geomorphic landforms it is necessary to date them first landscape evolution of alpine areas is often strongly related to the activities of glaciers in the pleistocene and holocene at sites where no organic matter for radiocarbon dating exists and where suitable boulders for surface exposure dating using in situ produced cosmogenic nuclides are absent dating of soils could give information about the timing of landscape evolution this paper explores the applicability of soil dating using the inventory of meteoric 10be in alpine soils for this purpose a set of 6 soil profiles in the swiss and italian alps was investigated the surface at these sites had already been dated using the radiocarbon technique or the surface exposure determination using in situ produced 10be consequently a direct comparison of the ages of the soils using meteoric 10be and other dating techniques was made possible the estimation of 10be deposition rates is subject to severe limitations and strongly influences the obtained results we tested three scenarios using a the meteoric 10be deposition rates as a function of the annual precipitation rate b a constant 10be input for the central alps and c as b but assuming a pre exposure of the parent material the obtained ages that are based on the 10be inventory in soils and on scenario a for the 10be input agreed reasonably well with the age using surface exposure or radiocarbon dating the ages obtained from soils using scenario b produced ages that were mostly too old whereas the approach using scenario c seemed to yield better results than scenario b erosion calculations can in theory be performed using the 10be inventory and 10be deposition rates an erosion estimation was possible using scenario a and c but not using b the calculated erosion rates using these scenarios seemed to be plausible with values in the range of 0 57 mm ky the dating of soils using 10be has several potential error sources analytical errors as well as errors from other parameters such as bulk soil density and soil skeleton content have to be taken into account the error range was from 8 up to 21 furthermore uncertainties in estimating 10be deposition rates substantially influence the calculated ages relative age estimates and under optimal conditions absolute dating can be carried out age determination of alpine soils using 10be gives another possibility to date surfaces when other methods fail or are not possible at all it is however not straightforward quite laborious and may consequently have some distinct limitations

five million year10be record in chinese loess and red clay climate and weathering relationships 10be measurements in bulk samples in different size fractions in selective chemically leached fractions of several representative loess paleosol sequences and in the underlying red clay sediments from the chinese loess plateau back to ca 5 ma were made using the ams accelerator mass spectrometer our data support but considerably extend the earlier studies of shen and beer and their colleagues in the upper 0 75 ma luochuan loess paleosol sequences the effect of climatic change is dramatically expressed by10be concentrations 1 in the red clay sediments for which we estimate model accumulation rates of 5 8 and 8 7 m ma 1 for the upper sequences in lingtai and baoji respectively 2 in the paleosols where soil maturation processes are manifest in the10be distribution within different size fractions accompanied by downward movement to zones of high authigenic mineral concentration and 3 in loess samples which at deposition had an appreciable endowment of10be from the dust source regions on the basis of leaching experiments we estimate that on average the paleosol layers lost about 3 3 of their initial10be content to the underlying layers by transport with water finally we estimate that the relative average zonal precipitation rate during glacial periods was 2 3 the average interglacial value the estimates of the initial10be concentrations and dust composition are consistent with the measured values for the recent atmospheric dust falls sampled from the loess plateau and the shandong peninsula

10be records of sediment cores from high northern latitudes implications for environmental and climatic changes the 10be records of four sediment cores forming a transect from the norwegian sea at 70 n core 23059 via the fram strait core 23235 to the arctic ocean at 86 n cores 1533 and 1524 were measured at a high depth resolution although the material in all the cores was controlled by different sedimentological regimes the 10be records of these cores were superimposed by glacial interglacial changes in the sedimentary environment core sections with high 10be concentrations 1 109 at g are related to interglacial stages and core sections with low10be concentrations 0 5 109 at g are related to glacial stages climatic transitions e g termination ii 5 6 are marked by drastic changes in the 10be concentrations of up to one order of magnitude the average 10be concentrations for each climatic stage show an inverse relationship to their corresponding sedimentation rates indicating that the 10be records are the result of dilution with more or less terrigenous ice rafted material however there are strong changes in the 10be fluxes e g termination ii into the sediments which may also account for the observed oscillations most likely both processes affected the 10be records equally amplifying the contrast between lower glacials and higher interglacials 10be concentrations the sharp contrast of high and low 10be concentrations at climatic stage boundaries are an independent proxy for climatic and sedimentary change in the nordic seas and can be applied for stratigraphic dating 10be stratigraphy of sediment cores from the northern north atlantic and the arctic ocean

boundary scavenging in the pacific ocean a comparison of 10be and 231pa concentrations of u th 231pa and 10be were measured in holocene sediments from two cores collected off the west coast of south america two cores from the east pacific rise two from the equatorial pacific and one from the south pacific central gyre our results together with data from 5 cores reported in the literature show that boundary scavenging plays a major role in the removal of 10be from the pacific ocean deposition rates of 10be at three margin sites are more than an order of magnitude greater than at sites of red clay accumulation in the deep central pacific deposition of 231pa is 4 to 5 fold greater at the margin sites the residence time of 10be with respect to chemical scavenging defined as its inventory in the water column divided by its rate of removal to the sediments varies regionally from 1000 years at the red clay sites in the deep central pacific to 100 years at the margin sites different factors control boundary scavenging of pa and be for example scavenging of 231pa is enhanced by metal oxide coatings of particles whereas this seems to have little influence on the scavenging of 10be 1990

large variations in holocene solar activity constraints from 10be in the greenland ice core project ice core 1 cosmogenic radionuclides extracted from ice cores hold a unique potential for reconstructing past solar activity changes beyond the direct instrumental period taking the geomagnetic modulation into account the solar activity in terms of the heliospheric modulation function can quantitatively be reconstructed in high resolution throughout the holocene for this period our results reveal changes in heliospheric modulation of galactic cosmic rays significantly larger than the variations reconstructed on the basis of neutron monitor measurements of galactic cosmic rays for the last 50 years moreover the 10be data from the greenland ice core project ice core as well as 14c support a high current solar activity however although the reconstruction of solar activity on long timescales is difficult our result suggests that the modern activity state of the sun is not that exceptional regarding the entire holocene this extended solar activity record provides the basis for further detailed investigations on solar and cosmic ray physics as well as on solar forcing of the earth s climate whose importance is suggested by increasing paleoclimatic evidences

a 200 kyr record of cosmogenic radionuclide production rate and geomagnetic field intensity from 10be in globally stacked deep sea sediments the reconstruction of geomagnetic field intensity variations during the last 200 kyr from paleomagnetic data is at present the subject of numerous studies and major debate there is currently no generally accepted record here we present a global stacked record of 230thex normalized 10be deposition in marine sediments representing relative variations in 10be production rate which are translated into field intensity variations the record shows major periods during which the field intensity was between 10 and 40 of the present day value namely 30 42 60 75 85 110 and 180 192 kyr b p our results are compared to independently derived paleomagnetic studies and th u calibrations of 14c dates on corals during most of the observed period the geomagnetic field intensity was weaker than today resulting in an overall 30 reduced value for the last 200 kyr

magnetotelluric evidence for thick skinned tectonics in central taiwan taiwan is the type example of an arc continent collision numerous tectonic models have been proposed for this orogen and include both thin skinned and thick skinned lithospheric deformation these models predict very different structures at middle and lower crustal depths but insuffi cient geophysical data exist to unequivocally distinguish between them long period magnetotelluric mt data were collected in central taiwan in 2006 2007 to constrain the crustal resistivity structure a two dimensional inversion of these mt data revealed a prominent electrical conductor that extends across the decollement predicted by the thin skinned model this feature is interpreted to be due to 1 2 saline fl uids and is inconsistent with the thin skinned model in contrast the thick skinned model predicts this feature since fl uids are generated in the crustal root through metamorphism quantitative correlation of the resistivity and seismic velocity models supports small volume high salinity fl uids in a thickened crust as the cause of this conductor

a cosmic trip 25 years of cosmogenic nuclides in geology terrestrial cosmogenic nuclides produced by secondary cosmic ray interactions in the atmosphere and in situ within minerals in the shallow lithosphere are widely used to date surface exposure of rocks and sediments to estimate erosion and weathering rates and to date sediment deposition or burial their use has transformed geomorphology and quaternary geology for the first time allowing landforms to be dated and denudation rates to be measured over soil forming time scales the application of cosmogenic nuclides to geology began soon after the invention of accelerator mass spectrometry ams in 1977 and increased dramatically with the measurement of in situ produced nuclides in mineral grains near earth s surface in the 1980s the past 25 yr have witnessed the development of cosmogenic nuclides from their initial detection to their prevalence today as a standard geochronological and geochemical tool this review covers the major developments of the past 25 yr by comparing the state of the field in 1988 with that of today and by identifying key advances in that period that moved the field forward we emphasize the most commonly used in situ produced nuclides measured by ams for geological applications but we also discuss other nuclides where their applications overlap our review covers ams instrumentation cosmogenic nuclide production rates the methods of surface exposure dating measurement of erosion and weathering and burial dating and meteoric 10 be in memoriam devendra lal 1929 2012 whose vision inspired the field

the influence of particle composition and particle flux on scavenging of th pa and be in the ocean we have examined the relative affinity of th pa and be for sorption from seawater onto particles of variable composition opal carbonate lithogenic particles and organic carbon nuclide concentrations in particles collected from time series sediment traps were normalized by the dissolved nuclide concentration in the overlying water column in order to compute partition coefficients under conditions spanning a wide range of particle flux and particle composition our results suggest that the affinity of particles for pa and be increases with their increasing opal content and decreasing carbonate content while the affinity of particles for th increases with increasing carbonate content and decreases with increasing opal content we find no correlation between the aluminosilicate content of particles and their affinity for scavenging of any of these elements extrapolating to a pure caco3 end member the partition coefficient for th 9 0 106 g g 1 is 40 times greater than for pa and roughly 100 times greater than for be whereas for a pure opal end member the partition coefficient for th 3 9 105 g g 1 is slightly less than that for pa and be partition coefficients decrease with increasing particle flux in open ocean settings but not in an ocean margin region this kinetic effect reflects the increasing contribution of unaltered surface material reaching the sediment traps as particle flux increases the degree of fractionation between pa and th and between be and th depends on the opal carbonate rain ratio these results challenge the use of sedimentary 231pa 230th and 10be 230th ratios as simple proxies of particle flux however the strong dependence of nuclide scavenging on the opal carbonate rain ratio may provide a needed tool for reconstructing past changes in planktonic community composition

beryllium 10 in the greenland ice core project ice core at summit greenland concentrations of the cosmogenic isotope 10be have been measured in more than 1350 samples from the greenland ice core project grip ice core drilled at summit greenland although a dust associated component of 10be retained by 0 45 m filters in some of the samples complicates the interpretations the results confirm that the first order origin of 10be concentration variations is changes in precipitation rate associated with different climate regimes this effect is seen not only between glacial and interglacial periods but also during the shorter dansgaard oeschger interstadials by contrast the 10be data do not support the interpretation of rapidly varying accumulation i e climate during the last interglacial they can however be used to help place limits on the origin of the ice in these events after taking into account variable snow accumulation effects variations in the 10be flux are observed probably caused by solar and geomagnetic modulation but possibly also by primary cosmic ray variations the most dramatic is a 10be peak 40 000 years ago similar to that found in the vostok ice core thus permitting a very precise correlation between climate records from arctic and antarctic ice cores the 36cl 10be ratio considering either total or only ice associated 10be shows significant variability over the whole core depth thus confirming the difficulty in using this parameter for dating ice cores

numerical earthquake models of the 2013 nantou taiwan earthquake series characteristics of source rupture processes strong ground motions and their tectonic implication on 27 march and 2 june 2013 two large earthquakes with magnitudes of ml 6 2 and ml 6 5 named the nantou earthquake series struck central taiwan these two events were located at depths of 15 20 km which implied that the mid crust of central taiwan is an active seismogenic area even though the subsurface structures have not been well established to determine the origins of the nantou earthquake series we investigated both the rupture processes and seismic wave propagations by employing inverse and forward numerical simulation techniques source inversion results indicated that one event ruptured from middle to shallow crust in the northwest direction while the other ruptured towards the southwest simulations of 3 d wave propagation showed that the rupture characteristics of the two events result in distinct directivity effects with different amplified shaking patterns from the results of numerical earthquake modeling we deduced that the occurrence of the nantou earthquake series may be related to stress release from the easternmost edge of a preexistent strong basement in central taiwan

how the structural architecture of the eurasian continental margin affects the structure seismicity and topography of the south central taiwan fold and thrust belt studies of mountain belts worldwide show that along strike changes are common in their foreland fold and thrust belts these are typically caused by processes related to fault reactivation and or fault focusing along changes in sedimentary sequences the study of active orogens like taiwan can also provide insights into how these processes influence transient features such as seismicity and topography in this paper we trace regional scale features from the eurasian continental margin in the taiwan strait into the south central taiwan fold and thrust belt we then present newly mapped surface geology p wave velocity maps and sections seismicity and topography data to test the hypothesis of whether or not these regional scale features of the margin are contributing to along strike changes in structural style and the distribution of seismicity and topography in this part of the taiwan fold and thrust belt these data show that the most important along strike change takes place at the eastward prolongation of the upper part of the margins necking zone where there is a causal link between fault reactivation involvement of basement in the thrusting concentration of seismicity and the formation of high topography on the area correlated with the necking zone the strike slip reactivation of east northeast striking extensional faults is causing sigmoidal offset of structures and topography along two main zones here basement is not involved in the thrusting there is weak focusing of seismicity and localized development of topography we also show that there are important differences in structure seismicity and topography between the margins shelf and its necking zone

the global average production rate of10be precipitation collected in continuously open containers for about a year at seven sites around the united states was analyzed for10be 90sr 210pb and238u based on these data and long term precipitation 90sr and210pb delivery patterns the stratospheric tropospheric and recycled10be components in the collections were estimated and the global10be production rate was assessed single station production rate estimates range from 0 52 106 atoms cm 2 yr 1 to 2 64 106 atoms cm 2 yr 1 the mean value is 1 21 106 atoms cm 2 yr 1 with a standard error of 0 26 106 atoms cm 2 yr 1

diversity patterns of the vascular plant group zosterophyllopsida in relation to devonian paleogeography abstract the zosterophyllopsida originated in the silurian and became prominent vascular components of early devonian floras worldwide an updated dataset of zosterophyllopsids at species level is analyzed to compare the taxic composition of five putative paleophytogeographic units laurussia siberia northwestern gondwana kazakhstan and northeastern gondwana i e australia china and the shan thai block the high level of endemicity shown by each unit confirms the phytogeographic differentiation and the occurrence of geographical barriers preventing massive floral exchanges between the corresponding regions for the late silurian early devonian time interval statistical analyses conducted on the three largest datasets those corresponding to laurussia siberia and northeastern gondwana indicate that the diversity dynamics of the group followed the same pattern in these regions almost all taxic diversity measures show that specific diversity was greatest in the middle and late pragian diversity dropped significantly thereafter however residual diversity reveals genuine regional patterns from this we show that the radiation of the zosterophyllopsida may have stopped earlier in northeastern gondwana and siberia than laurussia we propose that the onset of these extinctions resulted from the competitive replacement of the zosterophyllopsids by increasingly diversified lycopsids and basal euphyllophytes whose evolution could have been favored by external factors

beryllium 10 thorium 230 and protactinium 231 in galapagos microplate sediments implications of hydrothermal activity and paleoproductivity changes during the last 100 000 years biogenic particle fluxes from highly productive surface waters boundary scavenging and hydrothermal activity are the main factors influencing the deposition of radionuclides in the area of the galapagos microplate eastern equatorial pacific in order to evaluate the importance of these three processes throughout the last 100 kyr concentrations of the radionuclides 10be 230th and 231pa and of mn and fe were measured at high resolution in sediment samples from two gravity cores klh 068 and klh 093 high biological productivity in the surface waters overlying the investigated area has led to 10be and 231pa fluxes exceeding production during at least the last 30 kyr and probably the last 100 kyr however during periods of high productivity at the up welling centers off peru and extension of the equatorial high productivity zone a relative loss of 10be and 231pa may have occurred in these sediment cores because of boundary scavenging the effects of hydrothermal activity were investigated by comparing the 230thex concentrations to the mn fe ratios and by comparing the fluxes of 230th and 10be which exceed production the results suggest an enhanced hydrothermal influence during isotope stages 4 and 5 and to a lesser extent during isotope stage 1 in core klh 093 during isotope stages 2 and 3 the hydrothermal supply of mn was deposited elsewhere probably because of changes in current regime or deep water oxygenation a strong increase of the mn fe ratio at the beginning of climatic stage 1 which is not accompanied by an increase of the 230thex concentration is interpreted to be an effect of mn remobilization and reprecipitation in the sediment

10be and ba concentrations in west african sediments trace productivity in the past particle reactive elements are scavenged to a higher degree at ocean margins than in the open ocean due to higher fluxes of biogenic and terrigenous particles in order to determine the influence of these processes on the depositional fluxes of10be and barium we have performed high resolution measurements on sediment core geob 1008 3 from the congo fan because the core is dominated by terrigenous matter supplied by the congo river it has a high average mass accumulation rate of 6 5 cm kyr biogenic10be and ba concentrations were calculated from total concentrations by subtracting the terrigenous components of10be and ba which are assumed to be proportional to the flux of al2o3 the meanba al weight ratio of the terrigenous component was determined to be 0 0045 the unusualy high terrigenous10be concentrations of 9 1 109 atoms g al2o3 are either due to input of particles with high10be content by the congo river or due to scavenging of oceanic10be by riverine particles the maxima of biogenic10be and ba concentrations coincide with maxima of the paleoproductivity rates time series analysis of the10be and of ba concentration profiles reveals a strong dominance of the precessional period of 24 kyr which also controls the rates of paleoproductivity in this core during the maxima of productivity the flux of biogenic ba is enhanced to a larger extent than that of biogenic10be applying a model for coastal scavenging we ascribe the observed higher sensitivity of ba to biogenic particle fluxes to the fact that the ocean residence time of ba is approximately 10 times longer than that of10be

ams radiocarbon analyses from lake baikal siberia challanges of dating sediments from a large oligotrophic lake abstract a suite of 146 new accelerator mass spectrometer ams radiocarbon ages provides the first reliable chronology for late quaternary sediments in lake baikal in this large highly oligotrophic lake biogenic and authigenic carbonate are absent and plant macrofossils are extremely rare total organic carbon is therefore the primary material available for dating several problems are associated with the toc ages one is the mixture of carbon sources in toc not all of which are syndepositional in age this problem manifests itself in apparent ages for the sediment surface that are greater than zero however because most of the organic carbon in lake baikal sediments is algal autochthonous in origin this effect is limited to about 1000 500 years which can be corrected at least for young deposits the other major problem with dating lake baikal sediments is the very low carbon contents of glacial age deposits which makes them extremely susceptible to contamination with modern carbon this problem can be minimized by careful sampling and handling procedures the ages show almost an order of magnitude difference in sediment accumulation rates among different sedimentary environments in lake baikal from about 0 04 mm year on isolated banks such as academician ridge to nearly 0 3 mm year in the turbidite depositional areas beneath the deep basin floors such as the central basin the new ams ages clearly indicate that the dramatic increase in diatom productivity in the lake as evidenced by increases in biogenic silica and organic carbon began about 13 ka in contrast to previous estimates of 7 ka for the age of this transition holocene net sedimentation rates may be less than equal to or greater than those in the late pleistocene depending on the site this variability reflects the balance between variable terrigenous sedimentation and increased biogenic sedimentation during interglaciations the ages reported here and the temporal and spatial variation in sedimentation rates that they imply provide opportunities for paleoenvironmental reconstructions at different time scales and resolutions

high resolution records of 10be in endogenic travertine from baishuitai china a new proxy record of annual solar activity abstract the accurate reconstruction of past solar activity is a prerequisite for assessing the role of solar forcing on climate variations cosmogenic 10be produced by galactic cosmic rays and stored in natural archives such as ice cores and lake sediments has been shown to be the most reliable as an indicator of past solar activity although reconstructions at a higher annual resolution have remained elusive due to dating imprecision and uncertainties concerning the effect of depositional processes here we employ a methodology that facilitates the annual reconstruction of past cosmic ray and solar activity variations an annual 10be record is assembled from an endogenic travertine in baishuitai china covering the period 2001 2016 ce we demonstrate that the effect of depositional processes when 10be is incorporated into travertine can be accounted for using the associated 9be and potassium k contents and that the resulting corrected 10be content significantly correlates with the modeled global 10be production rates with a time lag of 1 5 2 5 years our results from the baishuitai endogenic travertine suggest that the 10be record in such carbonate sediments has considerable potential as a high resolution proxy for past cosmic ray and solar activity variations

the chi chi earthquake sequence active out of sequence thrust faulting in taiwan we combined precise focal depths and fault plane solutions of more than 40 events from the 20 september 1999 chi chi earthquake sequence with a synthesis of subsurface geology to show that the dominant structure for generating earthquakes in central taiwan is a moderately dipping 20 to 30 thrust fault away from the deformation front a second subparallel seismic zone lies about 15 kilometers below the main thrust these seismic zones differ from previous models indicating that both the basal decollement and relic normal faults are aseismic

uranium series disequilibrium sedimentation diatom frustules and paleoclimate change in lake baikal abstract the large volume of water approximately one fifth of the total surface fresh water on the planet contained in lake baikal in southeastern siberia is distinguished by having a relatively high concentration of uranium ca 2 nm and together with the surface sediments an unusually high234u238u alpha activity ratio of 1 95 about 80 of the input of uranium to the lake with a234u238u ratio of 2 0 comes from the selenga river profiles of uranium as well as the extent of isotopic disequilibrium in a 9 m sediment core collected on academic ridge generally show high values during interglacial periods corresponding to high diatom frustule numbers difr and biogenic silica bsi data that have been reported elsewhere during glacial periods low difr and bsi uranium progeny 234u and230th were in secular equilibrium with low concentrations of their parent238u radionuclide distributions were interpreted in terms of a quantitative model allowing for adsorption of riverine inputs of uranium onto two classes of sedimenting particles with differing238u232th ratios and uranium progeny in secular equilibrium if the234u238u activity ratio of adsorbed uranium has remained constant mean sedimentation rates can be independently estimated as 3 6 0 6 and 3 7 0 9 cm kyr 1 for the decay of234u and in growth of230th respectively these rates are consistent with a mean rate of 3 76 cm kyr 1 calculated by optimization of the correspondence between adsorbed238u and 18o in dated oceanic sediments the adsorbed uranium apparently tracks variable river flow during interglacials and is drastically reduced during periods of glaciation evidently uranium has not been significantly redistributed within baikal sediments over at least the past 250 kyr and is a unique biologically non essential tracer for climate sensitive processes which provide their own internal geochronometers potentially useful for ages up to 1 myr bp

subsurface imaging taiger experiments and tectonic models of taiwan abstract the seismicity deformation rates and associated erosion in the taiwan region clearly demonstrate that plate tectonic and orogenic activities are at a high level major geologic units can be neatly placed in the plate tectonic context albeit critical mapping in specific areas is still needed but the key processes involved in the building of the island remain under discussion of the two plates in the vicinity of taiwan the philippine sea plate psp is oceanic in its origin while the eurasian plate eup is comprised partly of the asian continental lithosphere and partly of the transitional lithosphere of the south china sea basin it is unanimously agreed that the collision of psp and eu is the cause of the taiwan orogeny but several models of the underlying geological processes have been proposed each with its own evolutionary history and implied subsurface tectonics taiger taiwan integrated geodynamics research crustal and mantle imaging experiments recently made possible a new round of testing and elucidation the new seismic tomography resolved structures under and offshore of taiwan to a depth of about 200 km in the upper mantle the steeply east dipping high velocity anomalies from southern to central taiwan are clear but only the extreme southern part is associated with seismicity toward the north the seismicity disappears the crustal root under the central range is strongly asymmetrical using 7 5 km s as a guide the steep west dipping face on the east stands in sharp contrast to a gradual east dipping face on the west a smaller root exists under the coastal range or slightly to the east of it between these two roots lies a well delineated high velocity rise spanning the length from hualien to taitung the 3 d variations in crustal and mantle structures parallel to the trend of the island are closely correlated with the plate tectonic framework of taiwan the crust is thickest in the central taiwan collision zone and although it thins toward the south the crust is over 30 km thick over the subduction in the south in northern taiwan the northward subducting psp collides with taiwan and the crust thins under northern taiwan where the subducting indenter reaches 50 km in depth the low vp vs ratio of around 1 6 at a mid crustal depth of 25 km in the central range indicates that current temperatures could exceed 700 c the remarkable thickening of the crust under the central range its rapid uplift without significant seismicity its deep exhumation and its thermal state contribute to make it the core of orogenic activities on taiwan island the expanded network during the taiger deployment captured broadband seismic data yielding enhanced s splitting results with mainly sks skks data the polarization directions of the fast s waves follow very closely the structural trends of the island supporting the concept of a vertically coherent taiwan orogeny in the outer few hundred kilometers of the earth

the structure and kinematics of the central taiwan mountain belt derived from geological and seismicity data 1 the structure of the taiwan mountain belt is thought to be that of an imbricate thrust and fold belt developed in a forward breaking sequence above a shallowly dipping basal detachment in recent years however a growing amount of seismicity data from the internal part of the mountain belt indicates the existence of widespread fault activity in the middle and lower crust suggesting that deeper levels of the crust must be involved in the deformation than predicted by the shallow detachment imbricate thrust belt model to address this issue we present new geological mapping together with earthquake focal mechanism and seismic energy release data from the central part of taiwan we concur with the interpretation that the foreland basin part of the western foothills comprises an imbricate thrust system that is developing as a forward breaking sequence that is structurally and kinematically linked to a basal detachment at between 7 and 10 km depth to the east of the foreland basin however in the hsuehshan and central ranges our data show the presence of two fault systems an earlier inactive thrust system with a well developed cleavage is cut by a system of steeply dipping active faults that penetrate to a depth of 25 to 30 km or more in the hsuehshan range the second fault system is best represented by a structural and kinematic model in which this part of the mountain belt forms a zone of transpression with a structural architecture similar to that of a crustal scale positive flower structure eastward in the central range mesozoic basement rocks are over thrusting strongly folded and cleaved deep water sediments of the first now inactive thrust system the involvement of deep crustal levels and mesozoic basement in the second fault system is suggestive of the reactivation of preexisting basin bounding faults that were located on the eurasian continental margin

beryllium in marine pore waters geochemical and geochronological implications diagenetic remobilization and hydrothermal inputs have been invoked as possible explanations for the discrepancy between the theoretical and measured temporal decrease of the non detrital 10be 9be ratio observed in sediments1 remobilization is also consistent with water column profiles of beryllium which indicate a significant benthic flux from sediments2 to evaluate the impact of diagenetic recycling on the beryllium isotopic composition of marine waters and the effects of this process on the beryllium geochronometer we have analysed the9 be content of interstitial waters from different environments here we report the first pore water profiles for 9be in oxic and suboxic pore waters as well as some preliminary results from hydrothermal sediments collected in the guaymas basin our results suggest that the use of the beryllium isotopes as a geochronometer is not affected either by sedimentary diagenesis at oxic and suboxic sites or by input of hydrothermally derived 9be more than a few kilometres from vent sites

further evidence for diversity in late silurian land vegetation small coalified plant fragments from basal pridoli silurian strata at perton near hereford england comprise isotomously branching smooth axes terminating in vertically elongate sporangia the latter which occasionally bifurcate are characterized by prominent distally concentrated spinous emergences and contain trilete retusoid smooth walled isospores the plants are placed in a new genus and species caia langii comparisons are made with a number of silurian and lower devonian plants with elongate sporangia and particularly with horneophyton a hypothesis is developed that spines on sporangia had a nutritive function the spores are discussed in terms of other records of late silurian early devonian in situ spores

long term climato limnological oscillation during the past 2 5 million years printed in lake baikal sediments the physical properties of long sediment cores bdp96 obtained from the academician ridge of lake baikal eastern siberia show that the changes in the climato limnological environment of the continental interior during the past 2 5 m y clearly reflected global climatic change oscillation in water content and grain size which are closely related to biogenic productivity coincides with marine 18o variation the values for water content and grain size are large during interglacial periods and small during glacial periods milankovitch parameters were also imprinted in the sediments over the past 2 5 m y a 400 ky period as well as a 100 ky period due to eccentricitical parameters is found in addition to other orbital parameter a 40 ky period of obliquitical and a 20 ky period of precessional parameter this indicates that change in solar insolation was closely related to long term variations in climato limnological regime in this area

a rock magnetic record from lake baikal siberia evidence for late quaternary climate change rock magnetic measurements of sediment cores from the academician ridge region of lake baikal siberia show variations related to late quaternary climate change based upon the well dated last glacial interglacial transition variations in magnetic concentration and mineralogy are related to glacial interglacial cycles using a conceptual model interglacial intervals are characterized by low magnetic concentrations and a composition that is dominated by low coercivity minerals glacial intervals are characterized by high magnetic concentrations and increased amounts of high coercivity minerals the variation in magnetic concentration is consistent with dilution by diatom opal during the more productive interglacial periods we also infer an increased contribution of eolian sediment during the colder windier and more arid glacial conditions when extensive loess deposits were formed throughout europe and asia eolian transport is inferred to deliver increased amounts of high coercivity minerals as staining on eolian grains during the glacial intervals variations in magnetic concentration and mineralogy of lake baikal sediment correlate to the specmap marine oxygen isotope record the high degree of correlation between baikal magnetic concentration mineralogy and the specmap oxygen isotope record indicates that lake baikal sediment preserves a history of climate change in central asia for the last 250 ka this correlation provides a method of estimating the age of sediment beyond the range of the radiocarbon method future work must include providing better age control and additional climate proxy data thereby strengthening the correlation of continental and marine climate records

beryllium 10 in continental sediments abstract the concentration of 10 be has been measured in 10 samples taken from a transect of surface sediments beginning in the atchafalaya river and extending across the bay 136 km into the gulf of mexico if corrected for a lower retentivity of sand for be they have a concentration that is constant within 13 this concentration is about an order of magnitude smaller than that of deep ocean sediments for comparison measurements of 10 be in rainwater in a sample of soil and in a deep ocean core were made

dense network intense seismicity and tectonics of taiwan abstract a temporary seismic network consisting of 295 land stations was deployed in 2009 in taiwan to monitor airgun sources during an onshore offshore experiment in taiwan we exploit the continuously recorded dataset to detect and map seismicity in the seismically very active taiwan by combining recent automatic detection and phase picking techniques we successfully generate an initial earthquake catalog of over 8400 events the hypodd algorithm is used to relocate and filter these events this network recorded smaller events than the permanent regional network because of the many stations around the high mountain ranges and the generally high station density along 6 lines the results based on the 2009 data generally reproduce the dominant seismicity features from many years of earthquake monitoring in taiwan in addition we map hitherto unknown dipping zones under the foothills and the central range that may correspond to seismogenic structures

multidecadal to centennial scale 10 be variations in holocene sediments of huguangyan maar lake south china we report a new high resolution holocene be 10 record from huguangyan maar lake in subtropical tropical south china aimed to detect the atmospheric be 10 production signal in low latitude regions after minimizing climatic effects by regression analyses between be 10 concentration and climatic proxies from the same archive we successfully distinguished variations in geomagnetic field intensity and solar activity using 2 000 year low and high pass filtering respectively of the residual be 10 record a proxy of the atmospheric be 10 production rate the resulting be 10 derived record of geomagnetic field intensity is generally comparable with geomagnetic models and the solar modulated be 10 signal shows significant correlations with solar activity proxies the preservation of be 10 production signal in the sediments of this low latitude maar lake highlights the largely unexplored potential as well as limitations of be 10 as a tool to reconstruct variations in solar activity and geomagnetic field intensity plain language summary the atmospheric production rate of cosmogenic be 10 depends on the cosmic ray flux penetrating the atmosphere a process that is mainly controlled by the geomagnetic field strength and solar activity the geomagnetic imprint on be 10 has been well established in previous studies of ice cores and marine sediments the relationship between solar activity and be 10 has also been studied in ice cores and high latitude lakes here we for the first time present a high resolution be 10 record from huguangyan maar lake in subtropical tropical south china over the holocene we successfully separated the atmospheric be 10 production signal from climatic effects that contribute to up to similar to 52 of the variance in be 10 concentration after eliminating the climatic effects variations in both geomagnetic field intensity and solar activity signals were reconstructed from the residual be 10 record using 2 000 year low pass and high pass filtering respectively the geomagnetic and solar modulated be 10 production signals are evaluated by comparisons with independent records this result unambiguously indicates that the be 10 derived solar activity signal at a low latitude subtropical site can be obtained even when the be 10 signal is dominated by regional climate in our case accounting for up to similar to 65 of the variance in the record during the early middle holocene

changes in the carbon cycle during the last deglaciation as indicated by the comparison of 10be and 14c records the variations in atmospheric radiocarbon c 14 concentration during the last 50 000 years can be attributed to changes in the c 14 production rate due to changes in solar activity the geomagnetic field and or interstellar galactic cosmic ray flux and to changes in the global carbon cycle the relative contributions of these processes is the subject of current debate although the discrepancies between the various reconstructions of the past atmospheric radiocarbon concentration increase with age the relatively good agreement over the last 25 000 years allows a quantitative discussion of the causes of the observed c 14 variations for this period using be 10 measurements from greenland summit ice cores we show that in addition to solar and geomagnetically induced production rate changes significant changes in the carbon cycle have to be considered to explain the measured c 14 concentrations there is evidence that these changes are connected to 1 global deglaciation and 2 climate changes in the north atlantic region on centennial to millennial time scales related to changes in the ocean circulation differences between be 10 and geomagnetic field records however suggest that uncertainties of about 20 still exist in determinations of past changes in the c 14 production rate c 2004 elsevier b v all rights reserved less

late holocene multi proxy records of environmental change on the south atlantic island tristan da cunha sediment stratigraphies from three sites one lake one overgrown lake and an exposed section on the island tristan da cunha in the temperate south atlantic were analysed by means of pollen analysis total carbon nitrogen and sulphur content determination magnetic susceptibility measurements and detailed radiocarbon dating the aim of these studies was to reconstruct the late holocene vegetation and climatic variations the oldest sediment sequence extends back to 2300 cal years bp the vegetation was relatively stable up to the arrival of humans in the 17th century the appearance of the introduced taxon rumex acetosa acetosella at c 300 cal years bp and a subsequent decline in forest cover on the lowland plain provide evidence of substantial human influence on the vegetation well before the establishment of the first permanent settlement in the 19th century before the first anthropogenic influence centennial scale fluctuations in the proxy records are interpreted as reflections of local hydrological changes probably caused by variations in precipitation as inferred mainly from changing proportions of pollen derived from telmatic and terrestrial taxa and corresponding changes in the deposition of mineral matter by fluvial erosion lake levels were low between c 1450 and 1050 cal years bp and high between c 1050 and 300 cal years bp these variations coincide with known climatic changes in southern africa and in the north atlantic suggesting that the inferred hydrological changes on tristan da cunha were related to large scale variations in the general oceanic and atmospheric circulation in the atlantic region

magnetotelluric imaging beneath the taiwan orogen an arc continent collision 1 the taiwan orogen has formed since the late miocene by oblique collision between the luzon volcanic arc on the philippine sea plate and the eurasian continental margin this oblique collision has produced an orogen that decreases in age from north to south and permits study of the temporal evolution of an arc continent collision these factors make taiwan a favorable location to study the process of arc continent collision the first long period magnetotelluric mt measurements were recorded in taiwan as part of the taiwan integrated geodynamics research taiger project in 2006 7 measurements were made at 82 sites on three transects across south central and north taiwan that span the breadth of the orogen and cross all major tectonic boundaries robust remote reference processing of the mt time series data resulted in high quality soundings that were modeled in both 2 and 3 dimensions these mt models support predictions of lithospheric deformation i e thick skinned tectonics beneath the central ranges in south and central taiwan but are inconsistent with predictions of orogen scale thin skinned models the mt resistivity model for northern taiwan is consistent with dewatering of the subducting philippine slab and with deformation described by the subducting indenter tectonic model modeling the taiger mt data has definitively shown that conductive and seismically active crustal structures exist to 30 km beneath the orogen these conductive regions interpreted as interconnected fluid map pervasive zones of collisional deformation that are lithospheric in scale

discovery of scyphocrinoid loboliths in western junggar xinjiang nw china implications for scyphocrinoid paleobiogeography and identification of the silurian devonian boundary abstract the loboliths which previously have been called plurilocular cystoids in china are actually the bulbous roots of scyphocrinoids which occur only and are widely distributed in the uppermost silurian through the lowermost devonian two quite different types of loboliths can be distinguished the plate and cirrus types loboliths both of which are significant fossils for the correlation of the strata at the silurian devonian boundary two lobolith bearing layers were found in pyroclastic turbidites at the silurian devonian transition in western junggar xinjiang nw china all identified loboliths are of the plate type this discovery provides not only important information for determination of the silurian devonian boundary in western junggar but also for the stratigraphic correlation outside of peri gongwana and laurussia moreover the finds are expanding the knowledge of the paleogeographic distribution of scyphocrinoids across facies boundaries between the paleocontinents

measurement of 10be from lake malawi africa drill core sediments and implications for geochronology abstract the cosmogenic radionuclide 10 be was measured from drill core sediments from lake malawi in order to help construct a chronology for the study of the tropical paleoclimate in east africa sediment samples were taken every 10 m from the core mal05 1c to 80 m in depth and then from that depth in core mal05 1b to 382 m sediment samples were then later taken at a higher resolution of every 2 m from mal05 1c they were then leached to remove the authigenic fraction the leachate was processed to separate out the beryllium isotopes and 10 be was measured at the tams facility at the university of arizona the 10 be 9 be profile from lake malawi sediments is similar to those derived from marine sediment cores for the late pleistocene and is consistent with the few radiocarbon and osl ir measurements made from the same core nevertheless a strong correlation between the stable isotope 9 be and the cosmogenic isotope 10 be suggests that both isotopes have been well mixed before deposition unlike in some marine sediment cores in addition the correlation of beryllium isotopes to a proxy of lake level toc total organic matter from lake malawi indicates that the concentrations of 10 be in the lake sediments result from the combined effects of global and local climates on lake level local hydrology and sediment transport in the lake malawi basin rather than as a direct response to its production in the atmosphere modulated by the intensity of the earth s dipole therefore a direct correlation of the 10 be 9 be to a chronology derived from the paleomagnetic variations measured from marine sediments was not possible nevertheless a comparison of the 10 be 9 be chronology allowing for decay at lake malawi to that of the global marine paleomagnetic record suggests that the bottom of core mal05 1b is no more than 750 ka in age

solar activity during the last 1000 yr inferred from radionuclide records identification of the causes of past climate change requires detailed knowledge of one of the most important natural factors solar forcing prior to the period of direct solar observations radionuclide abundances in natural archives provide the best known proxies for changes in solar activity here we present two independent reconstructions of changes in solar activity during the last 1000 yr which are inferred from be 10 and c 14 records we analyse the tree ring c 14 data shcal intca104 from 1000 to 1510 ad and annual data from 1511 to 1950 ad and four be 10 records from greenland ice cores camp century grip milcent and dye3 together with two be 10 records from antarctic ice cores dome concordia and south pole in general the be 10 and c 14 records exhibit good agreement that allows us to obtain reliable estimates of past solar magnetic modulation of the radionuclide production rates differences between be 10 records from antarctica and greenland indicate that climatic changes have influenced the deposition of be 10 during some periods of the last 1000 yr the radionuclide based reconstructions of past changes in solar activity do not always agree with the sunspot record which indicates that the coupling between those proxies is not as close as has been sometimes assumed the tree ring c 14 record and be 10 from antarctica indicate that recent solar activity is high but not exceptional with respect to the last 1000 yr c 2006 elsevier ltd all rights reserved less

10be in a deep sea core implications regarding10be production changes over the past 420 ka abstract the influx of 10 be into a globigerinid ooze core ch72 02 from the eastern north atlantic has been studied this core contains a depositional record of the first 11 18 o stages covering the last 423 ka it is shown that the marine deposition of 10 be is strongly influenced by the sedimentation of clays clay particles appear 10 times more efficient than the carbonate component as a carrier in bringing 10 be to the bottom sediments in core ch72 02 the deposition rates of 10 be averaged over each oxygen isotope stage for the past 11 stages show a scatter of 40 about the mean value of 6 6 10 8 atoms cm 2 ka 1 however after correction for changes in lithology the data show that the production rate of 10 be over the same period has varied no more than 25 and the variations are not systematic in that high or low 10 be production appear to be associated with either cold or warm climates on the time scale of this investigation intervals of ca 50 ka over the last 420 ka with resolutions as fine as 10 ka for portions of the record it is unlikely that the shielding effect of the solar wind has deviated by more than 25 or the geomagnetic field intensity has deviated by more than a factor of 1 6 from their long term averages

polyphase history and kinematics of a complex major fault zone in the northern taiwan mountain belt the lishan fault abstract the lishan fault is a major fault zone in the taiwan collision belt it separates two major units the hsuehshan range and the backbone range which differ in lithology ages of sediments metamorphic grades and deformation styles despite the importance of the lishan fault its evolution and tectonic behaviour remained poorly known and controversial we therefore carried out a tectonic study which includes both the identification of structures in and along the fault zone and the palaeostress analysis aiming at reconstructing the succession of fault mechanisms the lishan fault zone underwent polyphase evolution with reactivations under different tectonic regimes consistent with the cenozoic history of taiwan 1 1 on the hsuehshan range the earliest events reflect the palaeogene miocene extension of the chinese continental margin 2 2 serial cross sections and observation of ductile brittle structures show east vergent folding indicating that for the most recent compressional evolution related to late cenozoic taiwan collision the lishan fault was a steeply dipping east vergent back thrust the compression occurred along nw se trends inducing thrusting but also along n s ones inducing transpression with reverse sinistral slip the lishan fault thus underwent contraction as well as strike slip during the mountain building of the taiwan orogeny reverse and strike slip fault systems alternated because of permutations 2 3 under the same compressional stress regime of nw se 1 minor compressional events also occurred 3 3 a late extension accommodated by normal faulting reveals the influence of both the n s extension in the okinawa trough northeast off taiwan

transport of10be and9be in the ocean beryllium isotopes 10be and9be have been measured in suspended particles of 1 mm size collected by mid water sediment traps deployed in the eastern pacific at manop sites h 6 32 n 92 50 w water depth 3600 m and m 8 50 n 104 00 w 3100 m for comparison surface sediments from box cores taken from the two sites were also studied the concentrations of10be and9be in sediment trap particles are about an order of magnitude smaller than those in the bottom sediments which contain about 8 109 and 6 1016 atoms g 1 of10be and9be respectively the sediment trap samples collected from 50 m off the bottom showed significant 26 63 contributions from resuspended bottom sediments the10be 9be ratio in trap samples varies from 3 to 20 10 8 the variation may partly result from varied proportion of authigenic detrital material the fluxes of both isotopes exhibit a very strong seasonality the fluxes of10be into the traps at about 1500 m are estimated as 9 105 and 4 105 atoms cm 2 a 1 at sites h and m respectively these values are to be compared with the fluxes into the sediments of 4 5 105 atoms cm 2 a 1 at both locations good correlations exist between10be 9be and27al indicating that the primary carrier phase s for the beryllium isotopes in the water column may be aluminosilicates

beryllium isotopes as tracers of lake lisan last glacial dead sea hydrology and the laschamp geomagnetic excursion abstract the content of the cosmogenic isotope 10be t 1 2 1 39 ma in lacustrine sediments that deposit in lakes with a large watershed is susceptible to both climate and cosmogenic production rate variations in order to distinguish between these two controls we measured 10be and major elements in several sections of the annually laminated sediments of the lake lisan the last glacial precursor of the dead sea that are composed of detrital sediments and primary evaporitic aragonites the sections were selected to represent regional hydrology and climate as reflected by different lake configurations level rise drop and high stands and rapid change in the 10be production rate during the laschamp geomagnetic excursion since the short lived cosmogenic sister of 10be 7be t 1 2 53 3 d has virtually no recycled component the recycled 10be in lake lisan detrital sediments was evaluated by measuring 7be in their modern equivalents modern flood suspended matter dust and mud cracks our results demonstrate that although the recycled 10be component is significant secular variations in the 10be concentration in lake lisan sediments correlate with hydrological variations and geomagnetic excursions during periods of moderate variations in 10be production rate the 10be concentration in the lisan detrital sediments positively correlates with lake level al fe content and the al fe ca mg ratio these correlations suggest that the 10be is adsorbed on the fine silicate component probably clays of the detrital laminae the fine silicates together with carbonates were transported to dead sea drainage basin mainly as airborne dust that after a short residence time was washed into lake lisan as flood suspended matter we suggest that preferential dissolution of carbonates in the flood suspended matter concentrated the residual fine component leading to the positive correlation between 10be and the al fe ca mg ratio during periods of increased water discharge more carbonates were dissolved and hence the 10be concentration in the detrital laminae increased during periods of rapid increase in the 10be production rate e g the laschamp excursion 10be showed a 2 fold increase beyond the above mentioned correlations lake levels and al fe contents this observation suggests that lake lisan can serve as a potential high resolution archive of 10be production rate variations during periods of geomagnetic excursions

modern vertical deformation rates and mountain building in taiwan from precise leveling and continuous gps observations 2000 2008 1 to characterize the present day vertical displacement field in the active taiwan orogenic belt 1843 precise leveling and 199 continuous gps measurements from 2000 to 2008 are collected and analyzed in this study vertical velocities derived from the leveling data are placed in a reference frame of the chinese continental margin using continuous gps observations at nearby sites the leveling and gps vertical velocities generally reveal a dome shaped pattern with uplift of 0 2 18 5 mm yr in the interior of the mountain range and subsidence on the flanks of the mountains and coastal plains modern uplift rates in the active fold and thrust belt are generally consistent with geologic uplift rates however present day uplift rates in the central range are faster than the million years averaged exhumation rates the modern subsidence rates are generally consistent with geologic rates except for the rates in western coastal areas due to groundwater pumping present day subsidence in the southern central range and northern coastal range is however inconsistent with long term uplift which may reflect interseismic elastic strain accumulation across faults present day subsidence in northern taiwan occurs in a region of postcollisional orogenic collapse we model the present day and geologic vertical velocities and published gps horizontal velocity data across southern taiwan using a 2 d lithospheric model the model suggests a combined slip rate of 40 mm yr on the frontal thrusts and 45 mm yr on the longitudinal valley fault the model requires an additional source of crustal thickening under the central range to match the observed present day uplift rates

geomagnetic field intensity during the last 60 000 years based on 10be and 36cl from the summit ice cores and 14c abstract based on 10 be 36 cl and 14 c records we reconstruct past changes in the geomagnetic field intensity under the assumption that radionuclide records are mainly influenced by changes in their production rates subsequent comparison of these records with independent geomagnetic field reconstructions allows us to assess the reliability of our approach and to identify periods where our method or the geomagnetic field reconstructions might be problematic the geomagnetic field derived from the 10 be flux to summit in central greenland agrees well with independent geomagnetic field intensity reconstructions however compared to independent palaeomagnetic data the radionuclide record suggests increased geomagnetic field intensities especially for the period from 20 000 to 30 000 years bp 36 cl from the grip ice core agrees well with the 10 be record for the last ice age and hence also the reconstructed geomagnetic field based on the tree ring radiocarbon record it is possible to reconstruct geomagnetic field intensity changes during the holocene a comparison of radiocarbon based and independent geomagnetic field reconstructions indicates that changes in the carbon cycle significantly influenced the atmospheric radiocarbon concentration before 10 000 years bp

tectonic tremor and lfes on a reverse fault in taiwan we compare low frequency earthquakes lfes from triggered and ambient tremor under the southern central range taiwan we apply the pagerank algorithm used by aguiar and beroza 2014 that exploits the repetitive nature of the lfes to find repeating lfes in both ambient and triggered tremor we use these repeaters to create lfe templates and find that the templates created from both tremor types are very similar to test their similarity we use both interchangeably and find that most of both the ambient and triggered tremor match the lfe templates created from either data set suggesting that lfes for both events have a common origin we locate the lfes by using local earthquake p wave and s wave information and find that lfes from triggered and ambient tremor locate to between 20 and 35 km on what we interpret as the deep extension of the chaochou lishan fault

new observations on a pridoli plant assemblage from north xinjiang northwest china with comments on its evolutionary and palaeogeographical significance detailed descriptions of plant remains from a late silurian pridoli locality in xinjiang province northwest china are presented they include junggaria spinosa dou interpreted as identical with cooksonella sphaerica senkevich salopella xingjiangensis dou and a number of sterile axes including one with a leafy appearance superficially resembling a lycophyte and others of probable algal affinity lack of anatomical and reproductive characteristics precludes a more precise assessment of relationships a justification for the pridoli rather than lower devonian age of the assemblage is based on graptolites the composition of the assemblage is compared with coeval ones from europe north america north africa and kazakhstan and has closest similarities with the latter palaeogeographic proximity on the kazakhstan palaeocontinent is postulated but the dearth of global silurian occurrences of land plants make it premature to evaluate the significance of kazakhstan and chinese assemblages in terms of global provincialism in the late silurian the most distinctive element in these assemblages junggaria cooksonella has sporangia with more complex indeed more enigmatic organization than seen in most silurian and early devonian rhyniophytoids

variable be 10 fluxes in lacustrine sediments from tristan da cunha south atlantic a solar record a 650 yr long sediment sequence from a crater lake on tristan da cunha south atlantic was analysed for its be 10 content based on c 14 dating and sedimentary geochemical magnetic and palynological records the period between 900 and 1450 ad appears to have been unusually stable in terms of sedimentation and vegetation and therefore this period was chosen for analysis of the be 10 content during this period of highly organic sedimentation and closed vegetation the pattern of be 10 flux variations follows the be 10 fluctuations from the grip ice core and estimated c 14 production rates well however before and after this stable period variable sedimentation rates have to be accounted for to obtain results that are comparable to the established be 10 c 14 records our data show not only the possibility of obtaining detailed enough be 10 flux data from sedimentary sequences to reconstruct past solar forcing but also how sensitive this type of record is to sedimentary and environmental changes if suitable archives can be found they have the potential to improve reconstructions of solar activity far back in time c 2007 elsevier ltd all rights reserved less

beryllium 10 in deep sea sediments a tracer for the earth s magnetic field intensity during the last 200 000 years abstract we present a new approach for the reconstruction of the earth s magnetic field intensity during the last 200 000 years based on 10 be in deep sea sediments a simple box model that is able to describe boundary scavenging of 10 be in the ocean is used to study the sensitivity of 10 be to changes of water circulation and or varying particle rain rates the model is applied to separate transport and production signal in single 10 be records vertical sediment accumulation rates are used as input values for the model calculations the calculated scavenging factors are applied to correct the 10 be records for boundary scavenging the model corrected 10 be based paleointensity record correlates well with other records from very different archives

10be in chinese loess we report a first series of10be measurements on chinese loess covering the last 750 000 years the10be concentration shows a tendency to decrease with increasing grain size leaching experiments with acid solutions show that10be is strongly bound to particles and therefore mobility due to dissolution can be excluded the10be record in loess shows features similar to those observed in 180 records from deep sea sediments which strongly reflect climatic variations this allows one to correlate the10be loess records with 180 deep sea records and to establish a time scale based on this time scale accumulation rates of loess and10be fluxes can be calculated these reveal generally higher values for cold arid and windy periods than for warm humid and calmer intervals

the oldest flora of the south china block and the stratigraphic bearings of the plant remains from the ngoc vung series northern vietnam abstract several outcrops of the late silurian and devonian of the ngoc vung series northern vietnam yielded plant remains the late silurian localities delivered the earliest known flora of the south china block although the fossils are fragmentary they complement our knowledge about the global composition of the flora the major components of the flora are plants with dichotomous habit and terminal bivalvate sporangia which are close relatives to zosterophylls and zosterophylls plants with possible euphyllophyte affinities and bryophytes are occasionally present this floral composition is similar to that of the rich younger south china block assemblages from the posongchong and xujiachong formations of china considered pragian in age the south china block flora is therefore likely to have been dominated by zosterophylls and pre zosterophylls at least from the late silurian to the pragian i e a 20 million years long period it also strengthens the hypothesis that more derived plants were present on eastern gondwana earlier that elsewhere in the first steps of tracheophyte evolution the devonian localities of the ngoc vung series delivered a thick fibrous stem fragment and a basal euphyllophyte these latter plant remains provide some stratigraphic data the large stem fragment is consistent with an eifelian age for the duong dong formation part of the ngoc vung series as suggested by the brachiopod fauna the accompanying basal euphyllophyte displays a combination of characters axes 3 4 mm wide and lateral branchings that is also consistent with an eifelian age but possibly more characteristic of the emsian flora it is therefore suggested that the stratigraphic range of the duong dong formation might be extended down to the emsian

continental climate response to orbital forcing from biogenic silica records in lake baikal changes in insolation caused by periodic changes in the earth s orbital parameters provide the primary forcing for global ice ages1 6 but it is not clear to what extent the climates in continental interiors are controlled directly by regional variations in insolation and to what extent they are driven instead by the highly nonlinear response of the oceans and ice sheets here we investigate this question using the record of biogenic silica in lake baikal as a proxy for climate change in this high latitude mid continental region we find a good correlation between this record and that of marine oxygen isotopes4 over the past 250 kyr the baikal record exhibits both a strongly nonlinear component manifested in a 100 kyr periodicity and weaker direct insolation components manifested in the 41 kyr obliquity and 23 and 19 kyr precession orbital cycles these results show that even though extreme continental climates such as this are influenced directly by insolation variations they are dominated by the nonlinear rhythm of the oceans and ice sheets

monitoring interseismic activity on the ilan plain ne taiwan using small baseline ps insar gps and leveling measurements partitioning from arc continent collision and backarc extension

beryllium isotope systematics of submarine hydrothermal systems abstract both 10 be and 9 be concentrations have been measured in a hydrothermal fluid from the sediment starved east pacific rise at 21 n as well as in fluids and associated sediments from the sediment covered guaymas basin and escanaba trough hydrothermal systems the results show that while the 9 be concentrations in fluids from both types of systems are comparable about three orders of magnitude higher than that of the seawater supplying the systems their 10 be concentrations are significantly different the 10 be concentration in the solution emanating from the studied sediment starved hydrothermal system is at least two times lower than that of the pacific bottom water by contrast the 10 be concentration in hydrothermal solutions from sediment hosted environments are enriched over ambient seawater and are at least one order of magnitude higher than that measured in the 21 n fluid the sedimentary cover being the only available source of 10 be in these systems these data demonstrate that 10 be is an unambiguous tracer of interactions between hydrothermal fluids and recent sediments as an example this study examines hydrothermal solutions from the sediment starved mariana trough back arc basin which have compositions similar in many respects to those from sediment hosted environments however these fluids are depleted in 10 be relative to ambient seawater which precludes interaction with recent sediment as the cause of their peculiar chemical composition

increased production of cosmogenic 10be during the last glacial maximum beryllium 10 half life 1 5 myr is produced by spallation of nitrogen and oxygen atoms by cosmic rays in the upper atmosphere its production rate is proportional to the flux of cosmic rays which is modulated by solar activity and the strength of the earth s magnetic field1 2 weakening of the magnetic field allows more cosmic rays to impinge on the earth s atmosphere thereby increasing 10be production here we report that the ocean wide average accumulation rate of 10be in pacific sediments which reflects the global average production rate of 10be ref 3 was at least 25 greater during the height of the most recent ice age 24 000 16 000 yr ago than during the holocene the past 10 000 yr the higher production rate of 10be records the lower intensity of the geomagnetic field during that period and is consistent with the hypothesis developed to explain the younger 14c ages of fossil corals compared with ages obtained by u th dating4 these results also point to a more general need to consider variations in production rate in geochronological studies using other cosmogenic nuclides

eurasian snow cover variability and northern hemisphere climate predictability we present observational evidence demonstrating dynamic interactions and feedbacks between multi seasonal snow cover and winter time circulation anomalies over mid high latitudes the cooling effect of snow cover is associated with a strengthened and more expansive siberian high with more frequent topographically constrained intrusions west and north early season snow cover variability leads to altered general circulation patterns consistent with the dominant mode of winter variability observed in the northern hemisphere troposphere the implications of the surface atmosphere coupling for seasonal to interannual predictability are also discussed

new observations of the early land plant eocooksonia doweld from the pridoli upper silurian of xinjiang china abstract as an early land plant previously reported from the upper silurian pridoli of xinjiang northwest china and central kazakhstan the circumscription of eocooksonia sphaerica senkevitsch doweld remains ill defined because of the paucity of specimens and poor preservation in marine deposits new specimens of this plant are described from the pridoli aged wutubulake formation of the junggar basin xinjiang new observations and comparisons with the type material from kazakhstan confirm the pseudomonopodial branching pattern which forms an apparent main axis with lateral dichotomously branching systems our specimens demonstrate that the terminal sporangia of eocooksonia doweld consist of a central body and a border with four to eight elongate triangular emergences a character shown in the published illustrations of the type material but not mentioned in the original diagnosis eocooksonia may be close to cooksonia lang and pertonella fanning edwards et richardson in affinities particularly to the latter that has terminal discoidal sporangia with spiny emergences it is deduced that the sporangial central body of eocooksonia contains sporogenous tissues which are covered by a distal surface wall with radiated emergences one sporangium specimen of an unnamed plant is also described from the wutubulake formation of xinjiang it shows a central body with a wide border lacking emergences and represents a taxon superficially similar to eocooksonia

is the lishan fault of taiwan active abstract the lishan fault has been characterized alternately as a major discontinuity in stratigraphy structures and metamorphism a ductile shear zone a tectonic suture or non existent in addition to being a geological boundary it also marks transitions in subsurface structures thus the seismicity to the west of the fault permeates through the upper and mid crust while beneath the central range it is noticeably less and largely concentrated in the upper 12 km a prominent west dipping conductive zone extends upward to meet the lishan fault also the eastward increase of crust thickness from 30 km in the taiwan strait quickens under the lishan fault to form a root of over 50 km under the central range in the past the small magnitude seismicity along the lishan fault has been noticed but is too diffuse for definitive association with the fault recent processing of aftershock records of the 1999 mw 7 6 chi chi earthquake using central weather bureau data and especially data from three post chi chi deployments of seismic stations across central taiwan yielded hypocenters that appear to link directly to the lishan structure the presence of a near 4 km long vertical seismic zone directly under the surface trace of the lishan fault indicates that it is an active structure from the surface down to about 35 km and the variety of focal mechanisms indicates that the fault motion can be complex and depth dependent

magnetic properties of modern soils and quaternary loessic paleosols paleoclimatic implications the magnetic properties of paleosols developed in quaternary sequences of loess have been used for stratigraphic definition correlation with other terrestrial and deep sea sequences and paleoclimatic paleorainfall reconstruction in some loess paleosol sequences including those of the chinese loess plateau tajikistan and the czech republic maxima in magnetic susceptibility values correspond with the paleosol horizons and minima with the least weathered loess layers in other loess soil sequences including those of siberia alaska and argentina the relationship is completely opposite with susceptibility minima associated with the most developed paleosols to account for these opposite relationships the respective roles of 1 magnetic enhancement and 2 magnetic depletion and or dilution in determining soil magnetic properties are investigated for a range of modern soil types most magnetic enhancement is seen in the upper horizons of well drained cambisols absence or loss of magnetic iron oxides is apparent in acid podsol profiles and waterlogged soils for the cambisol profiles significant correlation is found between susceptibility and organic carbon cation exchange capacity and clay content the mineralogy morphology and grain size of soil magnetic carriers extracted from three modern enhanced soils and a paleosol from the chinese loess plateau are also identified by independent petrographic means microscopy and x ray diffraction of magnetic extracts magnetite and maghemite of ultrafine grain size from 0 4 to 0 001 i m are the major contributors to the magnetically enhanced soils weathering can concentrate detrital magnetic grains especially in the fine silt size fractions of soils the magnetic data from the modern soils indicate that interpretation of paleosol magnetic properties must be done on a site specific basis taking into account the possibilities of pedogenic enhancement pedogenic dilution or depletion and allochthonous inputs of magnetic minerals excessively arid wet or acid soils are unable to form significant amounts of pedogenic ferrimagnets well drained intermittently wet dry soils with reasonable buffering capacity and a substrate source of fe show most magnetic enhancement for those soils which favour magnetic enhancement processes correlation has been found between the maximum value of the pedogenic susceptibility and the annual rainfall the almost unique pedogenic system in the chinese loess plateau where variation in soil forming factors other than climate is reduced to a global minimum allows use of the paleo susceptibility values as proxy paleorainfall values to identify the mechanism of any link between magnetic properties for example susceptibility and climate change the mineralogy and grain size of soil magnetic carriers requires detailed investigation given the prospect of 1 quantitative paleorainfall records from continental loess records 2 predictions of present and future climate change and 3 the value of paleoclimate data for testing of numerical climate models such magnetic investigations can contribute significantly to our understanding of past and future environmental change

lake baikal record of continental climate response to orbital insolation during the past 5 million years the sedimentary record of biogenic silica from lake baikal in south central siberia suggests that this region of central asia was impacted by two major cooling episodes at 2 8 to 2 6 and 1 8 to 1 6 million years ago the spectral evolution of this continental interior site parallels the evolutionary frequency spectra for various marine oxygen isotope records in the baikal record the 41 000 year obliquity cycle is particularly strong from 1 8 to 0 8 million years ago variance in the 100 000 year eccentricity band increases during the past 0 8 million years the expected precession frequency of 23 000 years is highest during the past 400 000 years the modulation of the predicted 23 000 and 41 000 year insolation forcing by the 100 000 and 400 000 year eccentricity bands indicates that the transfer of variance from the precession and obliquity frequencies to the eccentricity part of the spectrum occurred in the eurasian continental interior as well as in tropical and high latitude ocean sites

a model for the termination of the ryukyu subduction zone against taiwan a junction of collision subduction separation and subduction boundaries 1 the nw moving philippine sea plate psp collides with the eurasian plate eup in the vicinity of taiwan and at the same time it subducts toward the north along sw ryukyu the ryukyu subduction zone terminates against eastern taiwan while the ryukyu trench is a linear bathymetric low about 100 km east of taiwan closer to taiwan it cannot be clearly identified bathymetrically owing to the deformation related to the collision making the location of the intersection of the ryukyu with taiwan difficult to decipher we propose a model for this complex of boundaries on the basis of seismicity and 3 d velocity structures in this model the intersection is placed at the latitude of about 23 7 n placing the northern part of the coastal range on eup as psp gets deeper along the subduction zone it collides with eup on the taiwan side only where they are in direct contact thus the eurasian plate on the taiwan side is being pushed and compressed by the nw moving philippine sea plate at increasing depth toward the north offshore of northeastern taiwan the wedge shaped eup on top of the ryukyu subducting plate is connected to the eup on the ryukyu side and coupled to the nw moving psp by friction at the plate interface the two sides of the eup above the western end of the subduction zone are not subjected to the same forces and a difference in motions can be expected the deformation of taiwan as revealed by continuous gps measurements geodetic movement along the east coast of taiwan and the formation of the hoping basin can be understood in terms of the proposed model

improved alignment of the hengchun fault southern taiwan based on fieldwork structure from motion shallow drilling and levelling data abstract the fault systems of taiwan have been repeatedly studied over many decades still new surveys consistently bring fresh insights into their mechanisms activity and geological characteristics the neotectonic map of taiwan is under constant development although the most active areas manifest at the on land boundary of the philippine sea plate and eurasia a suture zone known as the longitudinal valley and at the southwestern area of the western foothills the fault systems affect the entire island the hengchun peninsula represents the most recently emerged part of the taiwan orogen this narrow 20 25 km peninsula appears relatively aseismic however at the western flank the peninsula manifests tectonic activity along the hengchun fault in this study we surveyed the tectonic characteristics of the hengchun fault based on fieldwork four years of monitoring fault displacement in conjunction with levelling data core analysis uav surveys and mapping we have re evaluated the fault mechanisms as well as the geological formations of the hanging and footwall we surveyed features that allowed us to modify the existing model of the fault in two ways 1 correcting the location of the fault line in the southern area of the peninsula by moving it westwards about 800 m 2 defining the lithostratigraphy of the hanging and footwall of the fault a bathymetric map of the southern area of the hengchun peninsula obtained from the atomic energy council that extends the fault trace offshore to the south distinctively matches our proposed fault line these insights coupled with crust scale tomographic data from across the manila accretionary system form the basis of our opinion that the hengchun fault may play a major role in the tectonic evolution of the southern part of the taiwan orogen

toward the discrimination of fine grained ferrimagnets by magnetic measurements in lake and near shore marine sediments the magnetic properties of low field susceptibility frequency dependent susceptibility fd and susceptibility of anhysteretic remanent magnetisation arm are used to define sets of natural soil and sediment samples within which by the criteria of king et al 1982 and maher 1988 the modal ferrimagnetic grain diameter is less than 0 07 0 1 m within this sample set two distinct groups with low and high values respectively for the quotients arm and arm fd are defined the first group includes sediment samples from sites where published studies propose a detrital origin for the fine grained ferrimagnetic content where catchment samples are available for comparison they fall within the same envelope as do clays from palaeosol samples within chinese loess this envelope of low quotient values also overlaps with the values for the fine grained synthetic magnetite samples within maher s 1988 new mt series the high quotient envelope of values includes sediments from the adriatic sea and clays from saltmarsh and shallow water marine sediments in nw britain in these cases no catchment source is postulated for the fine grained magnetite the size range of magnetite in this set appears to be almost exclusively stable single domain ssd and a bacterial origin seems likely sample sets from estuarine environments between river inflow sites and the open sea show intermediate values which in the case of the potomac are ordered by distance down river although at this stage magnetic measurements alone cannot discriminate between bacterial and fine grained detrital ferrimagnets in sediments they hold out some promise of doing so provided the distinctions proposed here can be substantiated by transmission electron microscopy

meteoric cosmogenic beryllium 10 adsorbed to river sediment and soil applications for earth surface dynamics abstract rainfall scavenges meteoric cosmogenic 10be from the atmosphere 10be falls to the earth s surface where it binds tightly to sediment particles in non acidic soils over the life span of those soils as such meteoric 10be has the potential to be an excellent geochemical tracer of erosion and stability of surfaces in a diverse range of natural settings meteoric 10be has great potential as a recorder of first order erosion rates and soil residence times even though this tracer was first developed in the late 1980s and showed great promise as a geomorphic tool it was sidelined in the past two decades with the rise of the sister nuclide in situ 10be which is produced at a known rate inside quartz minerals since these early days substantial progress has been made in several areas that now shed new light on the applicability of the meteoric variety of this cosmogenic nuclide here we revisit the potential of this tracer and we summarize the progress 1 the atmospheric production and fallout is now described by numeric models and agrees with present day measurements and paleo archives such as from rain and ice cores 2 short term fluctuations in solar modulation of cosmic rays or in the delivery of 10be are averaged out over the time scale soils accumulate 3 in many cases the delivery of 10be is not dependent on the amount of precipitation 4 we explore where 10be is retained in soils and sediment 5 we suggest a law to account for the strong grain size dependence that controls adsorption and the measured nuclide concentrations and 6 we present a set of algebraic expressions that allows calculation of both soil or sediment ages and erosion rates from the inventory of meteoric 10be distributed through a vertical soil column the mathematical description is greatly simplified if the accumulation of 10be is at a steady state with its export through erosion in this case a surface sample allows for the calculation of an erosion rate explored further this approach allows calculation of catchment wide erosion rates from river sediment similar to the approach using 10be produced in situ in contrast to the in situ 10be approach however these analyses can be performed on any sample of fine grained material even where no quartz minerals are present therefore this technique may serve as a tool to date sediment where no other chronometer is available to track particle sources and to measure earth surface process rates in soil suspended river sediment and fine grained sedimentary deposits

pridoli graptolites from northern xinjiang northwest china integration of graptolite dates obtained from two sections in northern xinjiang northwest china permits the recognition of one pridoli biostratigraphic zone the monograptus bouceki biozone grap

three dimensional p velocity structures of the lithosphere beneath taiwan from the analysis of taiger and related seismic data sets 1 the convergence of the philippine sea and the eurasian plates in the taiwan region led to the formation of a young collisional mountain between two subduction zones of nearly orthogonal polarities the geological processes underlying the collision and its relation to subduction are the primary targets of taiger taiwan integrated geodynamic research project newly acquired passive and active sources data on land supplemented by ocean bottom as well as permanent seismic network data are used to derive a new 3 d tomographic velocity model using the 7 5 km sec contour as a marker for crustal deformation two trend parallel roots one under the central range with a maximum depth of 55 km and the other under the coastal range at 40 km are found to extend from southern to central 24 n taiwan between the two roots and lying approximately beneath the longitudinal valley the 7 5 km sec contour rises to 25 km depth in the upper mantle a high velocity zone east dipping and its upper surface coinciding with a wadati benioff zone in the south 22 8 n becomes near vertical and ill defined in the north 23 9 n the crustal deformation as defined by the roots and the along trend variations of the upper mantle structures under taiwan provide key information for the orogeny with the thickening of crust to 55 km or more processes such as eclogitization and delamination may come into play

the first record of cooksonia from south america in silurian rocks of bolivia plant megafossils resembling cooksonia caledonica lang aredescribed from the kirusillas formation in southern bolivia faunal and lithological evidence together with field relation ships advocate a late silurian ludlow age palaeocontinentalreconstructions suggest that the plants grew on the western edgeof gondwana at 50 60 s and indicate that cooksonia hadspread to higher latitudes soon after its appearance in the wenlock

eemian lake development hydrology and climate a multi stratigraphic study of the hollerup site in denmark abstract a classic northwest european open section with lacustrine eemian sediments hollerup has been studied with respect to sedimentology geochemistry stable isotopes diatoms and mineral magnetic analyses and correlated by geochemistry and diatoms to a previously pollen analysed section by andersen 1965 this correlation has enabled the section to be related to muller s 1974 tentative eemian absolute chronology and shows that the hollerup eemian sediments appear to cover c 11 000 yr our studies show that the onset of the eemian was characterized by a major lake level rise followed by an almost 3000 yr long period of high but oscillating lake levels it is argued that the latter part of this period of highly maritime climate can be defined as the eemian climatic optimum this period was interrupted by a few hundred years long phase of low lake level coinciding with the immigration of spruce followed by medium high lake levels the next c 3500 yr coinciding with the carpinus pollen zone seem to have been characterized by fairly humid and mild conditions although slightly more arid than during the preceding optimum the carpinus period ended with a more than 1000 yr long gradual lake level fall and this period of lake level change concurring with the transition into the pinus pollen dominated period terminated with an extreme low lake level event this 300 500 yr long arid phase coincides with a distinct peak in pine pollen and was followed by higher but slightly oscillating lake levels in a cooler climate the end of the eemian seems to have been characterised by a gradual cooling until almost pure clastic sedimentation and a marked expansion of herb pollen grains mark the onset of the weichselian based on regional correlations to other european terrestrial and north atlantic marine proxy records we argue that the distinct hydrologic and climatic events displayed in the hollerup record were possibly caused by a combination of sea level changes changes in the hydrologic cycle and changing oceanic circulation patterns the latter two may have been triggered by the opening and closure of the baltic sea white sea connection the initial build up of continental ice sheets and the first major impacts of meltwater induced freshwater in key areas for thermohaline circulation

the influence of inherited continental margin structures on the stress and strain fields of the south central taiwan fold and thrust belt in this paper we test whether or not structural and morphological features inherited from the eurasian continental margin are affecting the contemporary stress and strain fields in south central ta

last glacial to post glacial 10be fluctuations in a sediment core from the academician ridge lake baikal 10be concentrations sediment composition and sediment accumulation rates were determined in a sediment core from the academician ridge of lake baikal the 10be concentrations vary from 5 07 108 atoms g in the last glacial section to 11 25 108 atoms g in the section representing the post glacial climate stage 10be fluxes on the other hand increase toward the last glacial stage coinciding with an increase of the sediment accumulation rate these facts imply that climate related sedimentation is related to both flux and concentration of the nuclide in the sediment core during the last glacial stage arid conditions in the lake s watershed caused a marked increase in flux of clay particles with low 10be content to the lake resulting in an increased flux but lowered concentration of 10be in the sediments it is suggested that the 10be record of the bottom sediments of lake baikal can be used as a proxy indicator of climate change in central asia

information on past solar activity and geomagnetism from 10 be in the camp century ice core a nearly continuous record of the concentration of 10be from ice core data is compared with the tree ring derived record for 14c over the same period and it is found that short term trends in these data sets provide a record of solar activity no definitive relationship between the long term trends and the geomagnetic dipole moment is found