variability of el nino southern oscillation activity at millennial timescales during the holocene epoch the variability of el nino southern oscillation enso during the holocene epoch in particular on millennial timescales is poorly understood palaeoclimate studies have documented enso variability for selected intervals in the holocene but most records are either too short or insufficiently resolved to investigate variability on millennial scales1 2 3 here we present a record of sedimentation in laguna pallcacocha southern ecuador which is strongly influenced by enso variability and covers the past 12 000 years continuously we find that changes on a timescale of 2 8 years which we attribute to warm enso events become more frequent over the holocene until about 1 200 years ago and then decline towards the present periods of relatively high and low enso activity alternating at a timescale of about 2 000 years are superimposed on this long term trend we attribute the long term trend to orbitally induced changes in insolation and suggest internal enso dynamics as a possible cause of the millennial variability however the millennial oscillation will need to be confirmed in other enso proxy records

sea surface temperature records in the northern south china sea from mid holocene coral sr ca ratios 1 three mid holocene sea surface temperature sst records spanning more than 30 years were reconstructed for the northern south china sea using sr ca ratios in porites corals the results indicate warmer than present climates between circa 6100 yr b p and circa 6500 yr b p with the mid holocene average minimum monthly winter ssts the average maximum monthly summer ssts and the average annual ssts being about 0 5 degrees 1 4 degrees c 0 degrees 2 0 degrees c and 0 2 degrees 1 5 degrees c higher respectively than they were during 1970 1994 summer ssts decrease from circa 6500 yr b p to circa 6100 yr b p with a minimum centered at circa 6300 yr b p the higher average summer ssts are consistent with a stronger summer monsoon during the mid holocene and the decreasing trend indicates a secular decrease of summer monsoon strength which reflects the change in summer insolation in the northern hemisphere el nino southern oscillation enso cycles were apparent in both the mid holocene coral and modern instrumental records however the enso variability in the mid holocene ssts was weaker than that in the modern record and the sst record with the highest summer temperatures from circa 6460 yr b p to 6496 yr b p shows no robust enso cycle this agrees with other studies that indicate that stronger summer monsoon circulation may have been associated with suppressed enso variability during the mid holocene

evidence for large holocene earthquakes on the compton thrust fault los angeles california 1 we demonstrate that the compton blind thrust fault is active and has generated at least six large magnitude earthquakes mw 7 0 7 4 during the past 14 000 years this large concealed fault underlies the los angeles metropolitan area and thus poses one of the largest deterministic seismic risk in the united states we employ a methodology that uses a combination of high resolution seismic reflection profiles and borehole excavations to link blind faulting at seismogenic depths directly to near surface fault related folding deformed holocene strata record recent activity on the compton thrust and are marked by discrete sequences that thicken repeatedly across a series of buried fold scarps we interpret the intervals of growth as occurring after the formation of now buried paleofold scarps that formed during uplift events on the underlying compton thrust ramp minimum uplift in each of the scarp forming events which occurred at 0 7 1 75 ka event 1 0 7 3 4 ka or 1 9 3 4 event 2 5 6 7 2 ka event 3 5 4 8 4 ka event 4 10 3 12 5 ka event 5 and 10 3 13 7 ka event 6 ranged from 0 6 to 1 9 m indicating minimum thrust displacements of 1 3 to 4 2 m such large displacements are consistent with the occurrence of large magnitude earthquakes mw 7 this multidisciplinary methodology provides a means of defining the recent seismic behavior and therefore the hazard for blind thrust faults that underlie other major metropolitan regions around the world

satellite observation of upwelling along the western coast of the south china sea abstract we observed the evolution of upwelling along the western coast of the south china sea scs the data we used are noaa national oceanic and atmospheric administration satellite avhrr advanced very high resolution radiometer ir infrared images taken in 1996 and 1997 summer at the hrpt high resolution picture transmission receiving station built on tai ping island which is located in the central scs an upwelling intensity defined by the total heat loss in the upwelling cold water region is used to determine the relationship between coastal upwelling and the wind stress derived from the ers 2 european remote sensing satellite data the results show that the upwelling intensity has a good linear relationship with the total alongshore wind stress while it has a low correlation with the cross shore component of wind stress these results imply that the alongshore wind stress is the main factor to pump the cold water up to the sea surface layer meanwhile the satellite infrared images also indicate that the centroid of cold water moved southward from 15 n to 11 n during the observation period the size of upwelling area changed as well and finally evolved into a cold jet stretching offshore along 11 n 12 n in the mid august 1997 satellite infrared and altimeteric data show that the evolution of upwelling region is closely associated with the development of two anticyclonic circulations in the western scs

mineral micro and nano variability revealed by combined micromorphology and in situ submicroscopy abstract a combination of micromorphology and different in situ sub microscopical techniques performed on thin sections of soil saprolite and rock samples was used to assess possible relationships between micro and nano variability and macro and micro environmental conditions of mineral transformation during weathering four examples presented in this study illustrate variability in morphology chemistry and mineralogy of secondary minerals present in pseudomorphs after primary silicate minerals in volcanic soils present in the humid tropics the study was based on micromorphological characterization of secondary clay minerals with complementary submicroscopical analysis such as scanning electron microscopy with energy dispersive x ray analysis sem edxra performed on uncovered thin sections step scan x ray diffraction ssxrd and transmission electron diffraction tem eds carried out either on disturbed powder samples or undisturbed microsamples obtained by micro drilling in thin sections these techniques highlight a very complex mineralogy in pseudomorphs after primary minerals including secondary minerals that generally are assessed to be formed under contrasting physicochemical conditions gibbsite and 2 1 phyllosilicates in a pseudomorph after plagioclase halloysite kaolinite smectite and aluminum and iron oxi hydroxides in pseudomorphs after pyroxenes the study by tem of undisturbed microfabrics of secondary minerals in a clay pseudomorph after pyroxene revealed typical distribution patterns with mineralogical compositions varying over some microns the combination of techniques gave an improved insight on the complexity and variability of the nature composition and distribution of secondary minerals formed during weathering it indicates the influence of sequential weathering processes on mineral micro and nano variability

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

halloysite neoformation during the weathering of nephelinitic rocks under humid tropical conditions at mt etinde cameroon abstract mt etinde eruptions are dated at 0 65 ma it is located on the sw oceanic border of mt cameroon and is composed essentially of nephenilitic rocks the weathering of nephelinites has resulted in the formation of a 150 cm deep andic cambisol humic consisting of three horizons ah bw c mineral weathering was studied in detail in two profiles one p 1 developed from unaltered nephelinite nephelinite u and the other p 2 formed from hydrothermally altered nephelinite nephelinite h emphasis was on the impact of hydrothermal alterations on weathering profiles to characterise the signature of halloysite in nephelinitic regoliths and to discuss the evolution of mt etinde soils on the quaternary nephelinitic parent rocks the mineralogy of nephelinite u consists predominantly of clinopyroxene nepheline leucite hauyne titanomagnetite perovskite apatite and sphene nephelinite h differs from nephelinite u by phillipsite calcite occurrence the main weathering products are halloysites 1 nm and 0 7 nm and minor occurrence of gibbsite and hematite sem micromorphological examination coupled with microprobe analyses showed halloysites resulting from in situ alterations of feldspathoids phillipsites and clinopyroxenes 1 nm hydrated halloysite neoformation characterises the alteromorphs of the saprolite while 1 nm and 0 7 nm halloysite coexist in the bw and the ah horizons of both soils during weathering these halloysites had a chemical dependence with parent mineral as follows ce rich halloysite characterises alteromorph after phillipsite fe rich halloysite alteromorph after clinopyroxene ca rich halloysite alteromorph after hauyne and k rich halloysite alteromorph after leucite ce rich halloysite is a tracer of the hydrothermal impact in soils profile the si al ratio is also characteristic of the parent mineral therefore the availability of si is the only factor that controlled the formation of 1 nm halloysite at the base of the saprolite while the presence of 1 nm and 0 7 halloysite in the upper part of the saprolite the bw horizon and the ah horizon suggesting only time controls of the evolution of the profiles by both kinetic wet dry seasons and thermodynamic si bearing factors gibbsite occurs only in the nephelinite h soil its presence is due to the hydrothermal alteration which favoured the development of an intense microporosity allowing the elimination of silica the study highlighted the influence of past hydrothermal activity on the recent weathering process in the humid tropical area

late holocene rupture history of the rose canyon fault in old town san diego implications for cascading earthquakes on the newport inglewood rose canyon fault system

the equivalent strength of geometrical barriers to earthquakes we present a quantitative framework for evaluating the influence of non planar fault geometry on repeated seismic ruptures we model quasistatic ruptures on a non planar fault trace imbedded in a two dimensional elastic medium under in plane strain because of the presence of fault segments that are not parallel to the regional shear stress i e bends the apparent strength at a given point on the fault is not fixed but fluctuates with normal stress compressional features behave as increasingly strong barriers to fracture unless the stored normal stress is released in order to unlock the fault since slip on the fault itself cannot get rid of the normal stress this is achieved through the action of off fault morphological features such as secondary faulting folding and vertical motions that we introduce parametrically in the form of an aseismic relaxation the apparent strength of a fault bend will stabilize in a narrow interval of values after repeated ruptures characterized by a non dimensional hardness parameter whereby the relaxation rate is scaled by the tectonic loading rate on a fault structure having several small widely separated bends three families of events can be identified whose frequency and magnitude depend on the hardness relaxation parameter and the geometry small events that cluster in the tension zones of the bends intermediate size ruptures involving a single interbend segment and large ruptures that break through bends and link on or more interbend segments large multi segment events are most likely to occur for low values of the hardness i e fast relaxation and slow loading rate regions with compressional features act as barriers that stop most ruptures stress is stored at these sites until they themselves break and initiate motion on the smoother long reaches of the fault

reconstruction of storm tsunami records over the last 4000 years using transported coral blocks and lagoon sediments in the southern south china sea large transported coral blocks on reef flats and elevated sedimentation rates in atoll lagoons were demonstrated to be excellent proxies for past strong storms tsunamis in the southern south china sea here we introduce another important proxy coarse fraction contents of lagoon sediments this proxy is based on the principle that coarse fractions of enclosed lagoon sediments are usually controlled by strong sedimentary dynamics on the surrounding reef flat and thus increases in the weight percentages of coarse grained fractions of the lagoon sediments should also reflect strong storm tsunami events or increases in storminess with the size of the content peak as the proxy for the degree of storminess bearing this in mind we measured the contents of the 1 mm grain size fractions referred to as coarse fraction content in an undisturbed lagoon core precisely dated to cover the last 4000 years the decadal resolution data show a systematic variation with some peaks strongly correlated with in timing with strong storm tsunami events dated at ad 1872 15 1685 8 similar to 1680 6 1443 9 1336 9 1210 5 similar to 1201 4 and 1064 30 using wave transported coral blocks using the mean coarsefraction content 9 2 for the entire core as a reference line a total of 77 peaks were identified for the past 4000 years twenty of these peaks are higher than 23 the mean value for peaks that are correlated in age with the six strong storm events identified using independently dated coral blocks among these 23 peaks 13 occurred within the last 1000 years the concentration of contentpeaks in the last millennium could be partially due to higher deposition rates and sampling resolution over the last similar to 4000 years there appears to be a weakly increasing trend in coarse fraction contents towards present time but this trend is not obvious within the last millennium this long term variation may be related to changes in both storminess and reef lagoon morphology however the data do suggest three extremely stormy periods centring around ad similar to 1200 similar to 400 bc and similar to 1200 bc respectively overall this study demonstrates that combined use of transported coral blocks and coarse fraction contents of lagoon sediments provides an excellent means for comprehensive reconstruction of past storm tsunami activity c 2008 elsevier ltd and inqua all rights reserved

holocene environmental history at the treeline in the northern apennines italy a micromorphological approach the aim of this work is to investigate paleoenvironment at treeline quotas through the help of soil micromorphology it also assesses how the micromorphological approach can provide information in paleoenvironmental studies where paleosols are available as proxy archives nine soil profiles are described across the treeline between 1723 and 1860 m on mt cusna slope 2121 m a s l northern apennines italy undisturbed samples from selected soil horizons are collected in kubiena boxes from field observations all the profiles appear to be composed of two main pedogenetic units the upper one composed of a recent soil of colluvial origin and the deeper one consisting of an underlying more developed buried paleosol thin sections give detailed information about the nature and the origin of both pedological units four principal phases of paleosol development are detected a first period of temperate climate with forest cover and contrasted seasons is followed by a phase of change and then by a successive decrease of forest cover in a last phase the soil experiences frost action under the effect of a colder climate the final deposition of colluvium seems to be very recent historical time moreover multiple colluvial layers are identified colluvial material of different origins could be identified as part of dismantled soils similar to the preexisting paleosol in conclusion with the help of soil micromorphology it is possible to assess the existence of past stable forest at least 100 m above the present treeline the micromorphological approach represents a powerful tool in multidisciplinary paleoenvironmental studies due to its high level of resolution in outlining the individual and successive phases of soil evolution

new evidence from the south china sea for an abrupt termination of the last glacial period abrupt changes in climatic conditions have been seen at high latitudes in the north atlantic1 and the antarctic2 3 at 13 kyr bp it is important to determine whether this abrupt change was confined to high latitude regions or whether it was global here we present results demonstrating an abrupt change in the rate and character of sedimentation in the south china sea at the close of the last glacial period radiocarbon dating and its position in the oxygen isotope shift suggest that this change may be coincident with the changes found at high latitudes

deterioration of the volcanic kerb and pavement stones in a humid environment in the city centre of izmir turkey izmir is the third largest city in turkey and has being the centre of art culture tourism and trade activities throughout the 5 000 years of its history natural stones brought from different parts of the world have been widely used for construction of the prestigious buildings monuments and roads etc in the past in the city renovation of the street pavements and public gathering areas in the city centre has been undertaken by the metropolitan municipality in 2000 and continued through the year of 2001 these renovation activities have mainly been carried out in the streets running parallel to the sea shore volcanic rocks brought from the central anatolia ankara golbasi andesites and kayseri incesu tuffs have been used in the renovation works these rocks have shown extensive deteriorations within 4 years of their usage between 2001 and 2005 under the influence of different environmental factors in this study the deteriorations developed in the recently placed volcanic rocks used as kerb and pavement stones in the city centre of izmir in the light of their mineralogical chemical physical and mechanical properties used locations and the environmental factors are presented

radiocarbon variability in the western equatorial pacific inferred from a high resolution coral record from nauru island we have generated a high resolution coral delta sup 14 c record spanning the last 50 years to document the seasonal and interannual redistribution of surface waters in the western tropical pacific prebomb 1947 endash 1956 delta sup 14 c values average minus 63 per thousand and have a total range of 30 per thousand values begin to increase in 1957 reaching a maximum of 137 per thousand in mid 1983 large interannual variability of up to 80 per thousand closely follows the el ni tilde n o southern oscillation enso during each enso warm phase delta sup 14 c values begin to increase reflecting the reduction of low sup 14 c water upwelling in the east and the invasion of subtropical water into the western equatorial tropical pacific maximum delta sup 14 c values are in phase or lag the corresponding sea surface temperature maxima in the eastern tropical pacific whereas the rapid return to more negative delta sup 14 c is in phase with eastern pacific enso indices the highest amplitude excursions occur during the 1965 1966 and 1972 1973 events when the sup 14 c contrast is highest between the eastern pacific and subtropics the 1982 1983 el ni tilde n o although a larger enso event has a lower delta sup 14 c amplitude reflecting the penetration of bomb radiocarbon into the equatorial undercurrent and the reduced contrast in delta sup 14 c betweenmore thermocline and subtropical surface waters at that time this coral record demonstrates the potential for using similar radiocarbon time series for documenting variability in pacific shallow circulation over interannual and decadal timescales copyright 1998 american geophysical union less

microatoll record for large century scale sea level fluctuations in the mid holocene coral microatolls have been long used as precise indicators of past sea level but their use for precise definition of detailed sea level fluctuations is still rare here we report twelve high precision thermal ionization mass spectrometric th 230 ages for twelve rims of five mid holocene microatolls from all emerged reef terrace at leizhou peninsula northern south china sea this is a tectonically stable area enabling lis to reconstruct both the timing and trajectory of local sea level fluctuations accurately the elevations of these microatoll rims and cores were accurately determined relative to the surface of modern livin microatolls at the same site the results indicate that the sea level during the period of 7050 6600 yr bp years before ad 1950 was about 171 to 219 cm above the present with at least four cycles of fluctuations over this 450 yr interval sea level fluctuated by 20 40 cm on century scales crown copyright c 2009 published by university of washington all rights reserved

slip on faults in the imperial valley triggered by the 4 april 2010 mw 7 2 el mayor cucapah earthquake revealed by insar 1 radar interferometry insar field measurements and creepmeters reveal surface slip on multiple faults in the imperial valley triggered by the main shock of the 4 april 2010 el mayor cucapah mw 7 2 earthquake co seismic offsets occurred on the san andreas superstition hills imperial elmore ranch wienert coyote creek elsinore yuha and several minor faults near the town of ocotillo at the northern end of the mainshock rupture we documented right lateral slip 40 mm on northwest striking faults and left lateral slip 40 mm on southwest striking faults slip occurred on 15 km and 20 km long segments of the san andreas fault in the mecca hills 50 mm and durmid hill 10 mm respectively and on 25 km of the superstition hills fault 37 mm field measurements of slip on the superstition hills fault agree with insar and creepmeter measurements to within a few millimeters dislocation models of the insar data from the superstition hills fault confirm that creep in this sequence as in previous slip events is confined to shallow depths 3 km

late quaternary upwelling intensity and east asian monsoon forcing in the south china sea foraminifera from two cores off eastern vietnam and the northwestern philippines where modern summer and winter monsoon driven upwelling occurs in the south china sea respectively were analyzed to evaluate the changes in paleoproductivity and upper water structure over the last 220 000 yr we observed enhanced organic carbon flux and a shoaled thermocline when upwelling intensified off eastern vietnam during interglacial ages and off the northwestern philippines during glacial ages this indicates that the east asian summer monsoon increased while the winter monsoon decreased during interglacial ages particularly the upwelling reached a maximum off eastern vietnam during late marine isotopic stage mis 5 and off the northwestern philippines during mis 2 implying that the summer monsoon decreased gradually since mis 5 while the winter monsoon displayed an opposite trend the variations in upwelling proxies exhibit a distinct cyclicity with frequencies near 41 000 yr and 23 000 yr off eastern vietnam in contrast to a strong frequency peak near 100 000 yr off the northwestern philippines we suggest that the east asian summer monsoon has been forced by changes in solar insolation associated with precession and obliquity while ice volume forcing is probably a primary factor in determining the strength and timing of the east asian winter monsoon but with less important insolation forcing

coastal uplift of the san joaquin hills southern los angeles basin california by a large earthquake since a d 1635 late holocene marsh deposits and a shoreline along the coast of the san joaquin hills southern los angeles basin range from 1 to 3 6 m above the active shoreline radiocarbon dating of ancient marsh shows that emergence occurred after a d 1635 the age distribution and geomorphic expression of elevated marsh and shoreline are best explained by tectonic uplift due to a m 7 earthquake radio carbon dates and the historic record of seismicity suggest the earthquake occurred between a d 1635 and 1855 possibly in 1769 the historic record of earthquakes in the los angeles basin begins in a d 1769 and contains no other earthquakes greater than m 6 7 therefore the san joaquin hills earthquake may be the largest historic earthquake in the los angeles basin

influence of the intertropical convergence zone on the east asian monsoon a palaeoclimate record spanning the past 16 000 years with nearly annual time resolution has been obtained from lake huguang maar in china the magnetic properties and titanium content of the lake sediments are thought to reflect changes in the east asian winter monsoon strength thus providing a complement to palaeoclimate archives that record the strength of the rain bearing summer monsoon the records point to an anti correlation between winter and summer monsoon strength best explained by migration of the intertropical convergence zone itcz a belt of low pressure air at the equator interestingly the decline of china s tang dynasty and the mayan civilization broadly coincide with drought periods recorded in lake huguang maar and cariaco basin sediments respectively did major shifts in the position of the itcz catalyse simultaneous events in civilizations on opposite sides of the pacific ocean the asian australian monsoon is an important component of the earth s climate system that influences the societal and economic activity of roughly half the world s population the past strength of the rain bearing east asian summer monsoon can be reconstructed with archives such as cave deposits1 2 3 but the winter monsoon has no such signature in the hydrological cycle and has thus proved difficult to reconstruct here we present high resolution records of the magnetic properties and the titanium content of the sediments of lake huguang maar in coastal southeast china over the past 16 000 years which we use as proxies for the strength of the winter monsoon winds we find evidence for stronger winter monsoon winds before the bolling allerod warming during the younger dryas episode and during the middle and late holocene when cave stalagmites suggest weaker summer monsoons1 2 3 we conclude that this anticorrelation is best explained by migrations in the intertropical convergence zone similar migrations of the intertropical convergence zone have been observed in central america for the period ad 700 to 900 refs 4 6 suggesting global climatic changes at that time from the coincidence in timing we suggest that these migrations in the tropical rain belt could have contributed to the declines of both the tang dynasty in china and the classic maya in central america

source parameters of the 1933 long beach earthquake regional seismographic network and teleseismic data for the 1933 m l 6 3 long beach earthquake sequence have been analyzed both the teleseismic focal mechanism of the main shock and the distribution of the aftershocks are consistent with the event having occurred on the newport inglewood fault the focal mechanism had a strike of 315 dip of 80 to the northeast and rake of 170 relocation of the foreshock main shock aftershock sequence using modern events as fixed reference events shows that the rupture initiated near the huntington beach newport beach city boundary and extended unilaterally to the northwest to a distance of 13 to 16 km the centroidal depth was 10 2 km the total source duration was 5 sec and the seismic moment was 5 10 25 dyne cm which corresponds to an energy magnitude of m w 6 4 the source radius is estimated to have been 6 6 to 7 9 km which corresponds to a brune stress drop of 44 to 76 bars both the spatial distribution of aftershocks and inversion for the source time function suggest that the earthquake may have consisted of at least two subevents when the slip estimate from the seismic moment of 85 to 120 cm is compared with the long term geological slip rate of 0 1 to 1 0 mm yr along the newport inglewood fault the 1933 earthquake has a repeat time on the order of a few thousand years

precipitation and dissolution of gibbsite during weathering of andesitic boulders in humid tropical west java indonesia abstract several weathered andesite boulders sampled in typic humitropepts from the cigudeg area west java indonesia were studied using micromorphological mineralogical xrd tg dta sem edxra and chemical techniques because all data of the boulders are similar only the results of the largest boulder are presented in this paper three zones are distinguished the rim of the boulder core a transition layer and outer layers in the rim of the core weathering attacks the glass matrix and the anorthite rich parts of the plagioclases even before sufficient iron is liberated from pyroxenes goethite is deposited in their cracks as a first step to the formation of a boxwork in the transition layer mono and divalent cations have been lost but al shows an absolute accumulation as gibbsite in plagioclase pseudomorphs and pores it is presumed that the al originates from the more internal parts of the core towards the outer layer gibbsite gets completely removed supposedly as the result of a lowering of ph and the plagioclase pseudomorphs become filled with illuvial kaolinitic clay illuviation of clay and the import of iron from the surrounding soil material put limits to the use of isovolumetric calculations the goethite boxworks after pyroxenes reflect the original pattern of fractures rather than cleavage patterns

the effect of weathering on pore geometry and compressive strength of selected rock types from turkey weathering processes cause important changes in rock porosity besides porosity distribution of pore sizes is significant for the identification of changes due to rock weathering and its effects on fabric the formation of secondary porosity in different types of rock taken from different parts of turkey was examined and the results are presented in this paper the aim of this study was to observe changes in porosity due to weathering effective porosity mercury intrusion porosimetry and optical and scanning electron microscopy were used to evaluate the changes in pore geometry of the rocks additionally the dry density water absorption and uniaxial compressive strength of the rocks at different weathering stages were determined analysis of experimental data showed that microstructure of the rocks in relation to weathering is the main feature which controls their physical and mechanical properties the study revealed that fabric characteristics particularly the pore and fracture geometry are very important characteristics for assessment of the behaviour of weathered rock

continental shelf morphology and stratigraphy offshore san onofre california the interplay between rates of eustatic change and sediment supply abstract new high resolution chirp seismic data acquired offshore san onofre southern california reveal that shelf sediment distribution and thickness are primarily controlled by eustatic sea level rise and sediment supply throughout the majority of the study region a prominent abrasion platform and associated shoreline cutoff are observed in the subsurface from 72 to 53 m below present sea level these erosional features appear to have formed between melt water pulse 1a and melt water pulse 1b when the rate of sea level rise was lower there are three distinct sedimentary units mapped above a regional angular unconformity interpreted to be the holocene transgressive surface in the seismic data unit i the deepest unit is interpreted as a lag deposit that infills a topographic low associated with an abrasion platform unit i thins seaward by downlap and pinches out landward against the shoreline cutoff unit ii is a mid shelf lag deposit formed from shallower eroded material and thins seaward by downlap and landward by onlap the youngest unit iii is interpreted to represent modern sediment deposition faults in the study area do not appear to offset the transgressive surface the newport inglewood rose canyon fault system is active in other regions to the south e g la jolla where it offsets the transgressive surface and creates seafloor relief several shoals observed along the transgressive surface could record minor deformation due to fault activity in the study area nevertheless our preferred interpretation is that the shoals are regions more resistant to erosion during marine transgression the cristianitos fault zone also causes a shoaling of the transgressive surface this may be from resistant antecedent topography due to an early phase of compression on the fault the cristianitos fault zone was previously defined as a down to the north normal fault but the folding and faulting architecture imaged in the chirp data are more consistent with a strike slip fault with a down to the northwest dip slip component a third area of shoaling is observed off of san mateo and san onofre creeks this shoaling has a constructional component and could be a relict delta or beach structure

abrupt shift in subsurface temperatures in the tropical pacific associated with changes in el nino radiocarbon 14c content of surface waters inferred from a coral record from the galapagos islands increased abruptly during the upwelling season july through september after the el nino event of 1976 sea surface temperatures ssts associated with the upwelling season also shifted after 1976 the synchroneity of the shift in both 14c and sst implies that the vertical thermal structure of the eastern tropical pacific changed in 1976 this change may be responsible for the increase in frequency and intensity of el nino events since 1976

basalt weathering across scales abstract weathering of silicate minerals impacts many geological and ecological processes for example the weathering of basalt contributes significantly to consumption of atmospheric carbon dioxide co2 and must be included in global calculations of such consumption over geological timeframes here we compare weathering advance rates for basalt wd where d and indicate the scale at which the rate is determined and surface area measured respectively from the laboratory to the watershed scales data collected at the laboratory weathering rind soil profile and watershed scales show that weathering advance rate of basalt is a fractal property that can be described by a fractal dimension dr 2 3 by combining the fractal description of rates with an arrhenius relationship for basalt weathering we derive the following equation to predict weathering advance rates at any spatial scale from weathering advance rates measured at the bet scale w d k 0 a d r 2 e e a r t here k0 is the pre exponential factor 1 29 107 mm3 mm 2 yr 1 ea is the activation energy 70 kj mol 1 and a is a spatial constant related to the scale of measurement of bet surface area 10 7 mm the term a d r 2 is the roughness the roughness fractal dimension can be conceptualized as a factor related to both the thickness of the reaction front and the specific surface area within the reaction front however the above equation can also be written in terms of a surface fractal dimension and the hypothetical average grain radius these fractal dimensions provide insight into reaction front geometry and should vary with lithology once the surface area discrepancy has been accounted for using this method we find a one to two order of magnitude range in weathering advance rates measured at any scale or temperature that can be attributed to factors such as changes in erosional regime parent lithology mechanism climate composition of reacting fluid and biological activity our scaled equation when used to predict global basalt co2 consumption based upon global lithologic maps yields an uptake flux 1 75 1013 mol co2 yr 1 within the predicted error of fluxes estimated based upon riverine measurements

basalt weathering and pedogenesis across an environmental gradient in the southern cascade range california usa abstract basalt rocks occupy substantial land area and play a significant role in global weathering patterns and biogeochemical cycling the objective of this research was to quantify climatic controls of weathering and pedogenic processes on basalt derived soils across an environmental gradient on the western slope of the casacade range of california usa we hypothesized that climate controls mineral neogenesis with cool moist conditions favoring formation of short range order sro materials and warm dry conditions favoring smectite crystalline fe oxyhydroxides and kaolins four pedons were sampled across an elevation gradient 250 2500 m having large variation in mean annual soil temperature 5 17 c and mean annual precipitation 750 1350 mm the soil mineral assemblage was characterized by x ray diffraction selective dissolution total elemental analysis and light microscopy the degree of weathering and mineral assemblage exhibited a clear threshold at the permanent winter snowline 1200 m maximum soil development was noted just below the snowline with soils dominated by kaolinite and dehydrated halloysite crystalline fe oxyhydroxides 48 kg m 2 extensive loss of cations chemical index of alteration cia 95 and clay accumulation 447 kg m 2 in contrast the high elevation snow dominated pedons displayed less intense weathering e g cia

holocene activity of the rose canyon fault zone in san diego california the rose canyon fault zone in san diego california has many well expressed geomorphic characteristics of an active strike slip fault including scarps offset and deflected drainages and channel walls pressure ridges a closed depression and vegetation lineaments geomorphic expression of the fault zone from mount soledad south to mission bay indicates that the mount soledad strand is the most active a network of trenches excavated across the mount soledad strand in rose creek demonstrate a minimum of 8 7 m of dextral slip in a distinctive early to middle holocene gravel filled channel that crosses the fault zone the gravel filled channel was preserved within and east of the fault but was removed west of the fault zone by erosion or possibly grading during development consequently the actual displacement of the channel could be greater than 8 7 m radiocarbon dates on detrital charcoal recovered from the sediments beneath the channel yield a maximum calibrated age of about 8 1 0 2 kyr the minimum amount of slip along with the maximum age yield a minimum slip rate of 1 07 0 03 mm yr on this strand of the rose canyon fault zone for much of holocene time other strands of the rose canyon fault zone which are east and west of our site may also have holocene activity based on an analysis of the geomorphology of fault traces within the rose canyon fault zone along with the results of our trenching study we estimate the maximum likely slip rate at about 2 mm yr and a best estimate of about 1 5 mm yr stratigraphie evidence of at least three events is present during the past 8 1 kyr the most recent surface rupture displaces the modern a horizon topsoil suggesting that this event probably occurred within the past 500 years stratigraphie and structural relationships also indicate the occurrence of a scarp forming event at about 8 1 kyr prior to deposition of the gravel filled channel that was used as a piercing line a third event is indicated by the presence of several fault strands that displace the channel but did not move during the most recent event other events may also have occurred but these data suggest that the return time for surface rupturing earthquakes is no more than about 4 kyr

radiocarbon in corals from the cocos keeling islands and implications for indian ocean circulation annual bands of a porites coral from the cocos keeling islands eastern indian ocean were analysed by radiocarbon for 1955 1985 ad a rapid oceanic response of the site to bomb c is found with a maximum c value of 132 in 1975 this value is considerably higher than those for the northwestern indian ocean suggesting that surface waters reaching cocos are not derived from the arabian sea instead c values for cocos and those for watamu kenya agree well over most of the study interval suggesting that the south equatorial current carries c elevated water rather than c depleted water westward across the indian ocean this implies that oceanic upwelling in the northwestern indian ocean is spatially confined with little contribution to the upper limb of the global thermohaline circulation copyright 2005 by the american geophysical union

seismic constraints on the architecture of the newport inglewood rose canyon fault implications for the length and magnitude of future earthquake ruptures the newport inglewood rose canyon fault zone nirc is an active strike slip fault system within the pacific north american plate boundary in southern california located in close proximity to populated regions of san diego orange and los angeles counties prior to this study the nirc fault zone s continuity and geometry were not well constrained nested marine seismic reflection data with different vertical resolutions are employed to characterize the offshore fault architecture four main fault strands are identified offshore separated by three main stepovers along strike all of which are 2 kilometers or less in width empirical studies of historical ruptures worldwide show that earthquakes have ruptured through stepovers with this offset models of coulomb stress change along the fault zone are presented to examine the potential extent of future earthquake ruptures on the fault zone which appear to be dependent on the location of rupture initiation and fault geometry at the stepover these modeling results show that the southernmost stepover between the la jolla and torrey pines fault strands may act as an inhibitor to through going rupture due to the stepover width and change in fault geometry across the stepover however these results still suggest that rupture along the entire fault zone is possible

paleoseismic event dating and the conditional probability of large earthquakes on the southern san andreas fault california we introduce a quantitative approach to paleoearthquake dating and apply it to paleoseismic data from the wrightwood and pallett creek sites on the southern san andreas fault we illustrate how stratigraphic ordering sedimentolog ical and historical data can be used quantitatively in the process of estimating earth quake ages calibrated radiocarbon age distributions are used directly from layer dating through recurrence intervals and recurrence probability estimation the method does not eliminate subjective judgements in event dating but it does provide a means of systematically and objectively approaching the dating process date dis tributions for the most recent 14 events at wrightwood are based on sample and contextual evidence in fumal et al 2002 and site context and slip history in weldon et al 2002 pallett creek event and dating descriptions are from published sources for the five most recent events at wrightwood our results are consistent with pre viously published estimates with generally comparable or narrower uncertainties for pallett creek our earthquake date estimates generally overlap with previous results but typically have broader uncertainties some event date estimates are very sensitive to details of data interpretation the historical earthquake in 1857 ruptured the ground at both sites but is not constrained by radiocarbon data radiocarbon ages peat accumulation rates and historical constraints at pallett creek for event x yield a date estimate in the earliest 1800s and preclude a date in the late 1600s this event is almost certainly the historical 1812 earthquake as previously concluded by sieh et al 1989 this earthquake also produced ground deformation at wrightwood all events at pallett creek except for event t about a d 1360 and possibly event i about a d 960 have corresponding events at wrightwood with some overlap in age ranges event t falls during a period of low sedimentation at wrightwood when conditions were not favorable for recording earthquake evidence previously pro posed correlations of pallett creek x with wrightwood w3 in the 1690s and pallett creek event v with w5 around 1480 fumal et al 1993 appear unlikely after our dating reevaluation apparent internal inconsistencies among event layer and dating relationships around events r and v identify them as candidates for further inves tigation at the site conditional probabilities of earthquake recurrence were estimated using poisson lognormal and empirical models the presence of 12 or 13 events at wrightwood during the same interval that 10 events are reported at pallett creek is reflected in mean recurrence intervals of 105 and 135 years respectively average poisson model 30 year conditional probabilities are about 20 at pallett creek and 25 at wrightwood the lognormal model conditional probabilities are somewhat higher about 25 for pallett creek and 34 for wrightwood lognormal variance rln estimates of 0 76 and 0 70 respectively imply only weak time predictability conditional probabilities of 29 and 46 respectively were estimated for an em pirical distribution derived from the data alone conditional probability uncertainties are dominated by the brevity of the event series dating uncertainty contributes only secondarily wrightwood and pallett creek event chronologies both suggest varia tions in recurrence interval with time hinting that some form of recurrence rate modulation may be at work but formal testing shows that neither series is more ordered than might be produced by a poisson process

chemical weathering in the volcanic soils of isla santa cruz galapagos islands ecuador abstract forty three soils 130 horizons sampled by the geo pedological mission organized by the state university of gent belgium in 1962 on isla santa cruz galapagos islands were analysed in order to determine their degree of chemical evolution several weathering indices weathering index of parker wip chemical index of alteration cia chemical index of weathering ciw plagioclase index of alteration pia and silica titania index sti and multivariate statistical analysis principal components analysis based on chemical composition were used with the only exception of the sti the indices were highly correlated r 0 85 the highest wip and sti values 20 9 8 2 and 70 2 2 2 respectively were found for soils developed on basalt flows near the coast slightly lower values wip 16 8 5 1 and sti 61 3 4 were shown by brown soils developed from basaltic flows at elevations between 140 and 225 m a s l while the lowest values wip 9 5 and sti 47 6 8 representing the more weathered materials were found for soils located at the highest elevations 400 m a s l and mostly developed on pyroclastic materials tuff and tephra as the chemical composition of the geological material basalt and tephra is highly homogeneous the degree of weathering is likely to depend on climatic conditions controlled by altitude and orientation on the windward slopes of the island a gradient of increasing weathering is observed from the arid conditions predominant at the coast to elevations of 400 500 m a s l where much more humid conditions prevail principal component analysis on elemental composition also supported the interpretation that the degree of weathering first component and soil horizonation second component are both related to climatic conditions both the variation of the chemical indices and the principal components of the geochemical composition are related to the bioclimatic zones soils with the lowest degree of weathering are located in the arid coastal zone slightly higher intensity was found for soils located in the transition and scalesia zones while the most weathered soils appear in the brown zone compared to other volcanic soils studied in the literature soils from isla santa cruz are in the upper range of chemical weathering intensity only comparable to soils from azores islands and canary islands tenerife and la gomera developed on basalts under oceanic conditions

revisiting the 23 february 1892 laguna salada earthquake according to some compilations the laguna salada baja california earthquake of 23 february 1892 ranks among the largest earthquakes in california and baja california in historic times although surface rupture was not documented at the time of the earthquake recent geologic investigations have identified and mapped a rupture on the laguna salada fault that can be associated with high probability with the 1892 event mueller and rockwell 1995 the only intensity based magnitude estimate for the earthquake m 7 8 was made by strand 1980 based on an interpretation of macroseismic effects and a comparison of isoseismal areas with those from instrumentally recorded earthquakes in this study we reinterpret original accounts of the laguna salada earthquake we assign modified mercalli intensity mmi values in keeping with current practice focusing on objective descriptions of damage rather than subjective human response and not assigning mmi values to effects that are now known to be poor indicators of shaking level such as liquefaction and rockfalls the reinterpreted isoseismal contours and the estimated magnitude are both significantly smaller than those obtained earlier using the method of bakun and wentworth 1997 we obtain a magnitude estimate of m 7 2 and an optimal epicenter less than 15 km from the center of the mapped laguna salada rupture the isoseismal contours are elongated toward the northwest which is qualitatively consistent with a directivity effect assuming that the fault ruptured from southeast to northwest we suggest that the elongation may also thus reflect wave propagation effects with more efficient propagation of crustal surface lg waves in the direction of the overall regional tectonic fabric

timing and duration of the last interglacial inferred from high resolution u series chronology of stalagmite growth in southern hemisphere high precision th 230 u 238 ages for a stalagmite from newdegate cave in southern tasmania australia define a rare record of precipitation between 100 and 155 ka before the present the fastest stalagmite growth occurred between 129 2 1 6 and 122 1 2 0 ka similar to 61 5 mm ka coinciding with a time of prolific coral growth from western australia 128 122 ka this is the first high resolution continental record in the southern hemisphere that can be compared and correlated with the marine record such correlation shows that in southern australia the onset of full interglacial sea level and the initiation of highest precipitation on land were synchronous the stalagmite growth rate between 129 2 and 142 2 ka similar to 5 9 mm ka was lower than that between 142 2 and 154 5 ka similar to 18 7 mm ka implying drier conditions during the penultimate deglaciation despite rising temperature and sea level this asymmetrical precipitation pattern is caused by latitudinal movement of subtropical highs and an associated westerly circulation in response to a changing equator to pole temperature gradient both marine and continental records in australia strongly suggest that the insolation maximum between 126 and 128 ka at 65 degreesn was directly responsible for the maintenance of full last interglacial conditions although the triggers that initiated penultimate deglaciation at similar to 142 ka remain unsolved c 2001 elsevier science b v all rights reserved

late quaternary paleoceanography of the south china sea surface circulation and carbonate cycles paleoceanographic information from 34 sediment cores is summarized to investigate the glacial interglacial variations in sea surface circulation and late quaternary carbonate cycles in the south china sea judging from the distribution pattern of deposition rates the enormous terrigenous supply by rivers is responsible for the high rate of hemipelagic sedimentation which was even higher during glacial periods paleotemperature maps based on transfer function temperature estimates have revealed a e w gradient of sst for glacial summer and a s n gradient for glacial winter and this agrees well with the clockwise surface circulation in summer and counterclockwise in winter during glacials as shown by a preliminary computer modelling the high resolution paleotemperature curves of core v36 3 from the northern slope show an abrupt cooling event which may belong to the younger dryas carbonate percentage in sediments and preservation of foraminifers and pteropods are used to study the carbonate cycles in the marginal sea it turns out that two mechanisms are functioning there being a basin with large drainage areas vast amount of river borne terrigenous input dilutes carbonate and its intensification during glacial decreases the glacial cac03 being a basin connected with the pacific the fluctuations of lysocline ccd and acd in the scs are related to those in the pacific ocean and dissolution is strengthened at interglacial thus above the present ccd the dilution factor predominates and the atlantic cycles are produced below the present ccd the dissolution factor prevails resulting in the pacific pattern of carbonate cycles

synchronous tropical south china sea sst change and greenland warming during deglaciation the tropical ocean plays a major role in global climate it is therefore crucial to establish the precise phase between tropical and high latitude climate variability during past abrupt climate events in order to gain insight into the mechanisms of global climate change here we present alkenone sea surface temperature sst records from the tropical south china sea that show an abrupt temperature increase of at least 1 c at the end of the last glacial period within the recognized dating uncertainties this sst increase is synchronous with the bolling warming observed at 14 6 thousand years ago in the greenland ice sheet project 2 ice core

mineral neoformation in pore spaces during alteration and weathering of andesitic rocks in humid tropical indonesia abstract the morphology chemistry and mineralogy of minerals newly formed in voids products of weathering of andesitic rocks were studied using optical and submicroscopic techniques on thin sections combined with scanning electron microscopy sem energy dispersion x ray analysis edxra and x ray diffraction analysis on subsamples samples were taken from the core the outer core and the soft outer layers of weathered andesitic boulders in the cigudeg area west java about 75 km south of jakarta indonesia with udic moisture and isohyperthermic temperature regime the neoformed minerals observed in planar voids and cavities comprise 1 1 phyllosilicates goethite and gibbsite and juxtaposed coatings of halloysite mixed layer phyllosilicates goethite and gibbsite the mineral sequences observed confirm former studies on the groundmass of the boulder in the first weathering layer an absolute accumulation of gibbsite takes place further away from the core the gibbsite is redissolved and replaced by illuvial phyllosilicate clay the possibility of inheritance of the 2 1 layer silicates from a hydrothermal alteration is discussed the sharp boundaries in the juxtaposed coatings point to a stepwise sequential rather than a gradual evolution of the microenvironment

holocene marine 14c reservoir age variability evidence from 230th dated corals in the south china sea the south china sea scs is well connected with the western pacific and influenced by the east asian monsoon we have examined temporal variations in radiocarbon marine reservoir ages r and regional marine reservoir corrections delta r of the scs during the holocene using paired measurements of ams c 14 and tims th 230 on 20 pristine corals the results show large fluctuations in both r and delta r values over the past 7500 years yrs with two distinct plateaus during 7 5 5 6 and 3 5 2 5 thousand calendar years before present cal ka bp the respective weighted mean delta r values of these plateaus are 151 85 and 89 59 yrs which are significantly higher than its modern value of 23 52 yrs this suggests that using a constant modern delta r value to calibrate c 14 dates of the scs marine samples will introduce additional errors to the calibrated ages our results provide the first database for the holocene r and delta r values of the scs for improved radiocarbon calibration of marine samples we interpret the two delta r plateaus as being related to two intervals with weakened el nino southern oscillation enso and intensified east asian summer monsoon easm this is because the c 14 content of the scs surface water is controlled by both the c 14 concentration of the pacific north equatorial current nec which is in turn influenced by enso induced upwelling along the pacific equator and vertical upwelling within the scs as a result of moisture transportation to midlatitude region to supply the easm rainfall

increasing australian indonesian monsoon rainfall linked to early holocene sea level rise the australian indonesian summer monsoon affects rainfall variability across the indo pacific region reconstructions of monsoon strength from stalagmites show that precipitation increased from 11 000 to 7 000 years ago as rising global sea level caused the flooding of the indonesian continental shelf the australian indonesian summer monsoon affects rainfall variability and hence terrestrial productivity in the densely populated tropical indo pacific region it has been proposed that the main control of summer monsoon precipitation on millennial timescales is local insolation1 2 3 but unravelling the mechanisms that have influenced monsoon variability and teleconnections has proven difficult owing to the lack of high resolution records of past monsoon behaviour here we present a precisely dated reconstruction of monsoon rainfall over the past 12 000 years based on oxygen isotope measurements from two stalagmites collected in southeast indonesia we show that the summer monsoon precipitation increased during the younger dryas cooling event when atlantic meridional overturning circulation was relatively weak4 monsoon precipitation intensified even more rapidly from 11 000 to 7 000 years ago when the indonesian continental shelf was flooded by global sea level rise5 6 7 we suggest that the intensification during the younger dryas cooling was caused by enhanced winter monsoon outflow from asia and a related southward migration of the intertropical convergence zone8 however the early holocene intensification of monsoon precipitation was driven by sea level rise which increased the supply of moisture to the indonesian archipelago

paleoseismicity of the north branch of the newport inglewood fault zone in huntington beach california from cone penetrometer test data abstract application of cone penetrometer testing cpt is a promising method for studying subsurface fault zones in stratified unconsolidated sediment where trenching is not feasible analysis of data from 72 cpts spaced 7 5 to 30 0 m apart and 9 borings indicates that the north branch fault the active strand of the newport inglewood fault zone nifz in huntington beach has generated at least three and most likely five recognizable surface ruptures in the past 11 7 0 7 ka additional smaller earthquakes similar to the m w 6 4 1933 long beach earthquake may also have occurred but would not be recognizable with this method the minimum right lateral holocene slip rate of the nifz in the study area is estimated to be 0 34 to 0 55 mm yr the actual slip rate may be significantly higher

evolution and variability of the asian monsoon system state of the art and outstanding issues the asian monsoon is comprised of the indian and east asian subsystems these two components are linked to one another in varying degrees by regions of strong sensible heating indo asian landmass and strong latent heat export the western pacific warm pool and the southern subtropical indian ocean variability within the indian and east asian subsystems interactions among them and the extent to which they interact with other climate phenomena e g enso are current topics of modern and paleoclimate research this work provides an overview of past and current paleomonsoon research on tectonic to interannual time scales with a primary focus on marine sediment records while past and current work has contributed greatly to our understanding of paleomonsoon variability at all time scales additional efforts are required to make further progress in two critical areas 1 additional efforts are needed in terms of proxy development and evaluation requiring concerted efforts at long term sediment trap deployments in key monsoon influenced regions as well as development of adequate and widely available core top databases these are necessary to assess the impact of modern oceanographic and seafloor processes on potential monsoon proxies 2 additional effort is also needed in acquiring a sufficient geographic distribution of downcore records to assess linkages among the subsystems and their role in the context of extratropical climate change these records should have high sedimentation rates including varved sections this requires substantial survey support to identify the most appropriate coring and drilling targets c 2004 elsevier ltd all rights reserved