halokinetic sequence stratigraphy fluvial sedimentology and structural geometry of the eocene carroza formation along la popa salt weld la popa basin mexico

ferromanganese crusts as archives of deep water cd isotope compositions 1 the geochemistry of cd in seawater has attracted significant attention owing to the nutrient like properties of this element recent culturing studies have demonstrated that cd is a biologically important trace metal that plays a role in the sequestration of inorganic carbon this conclusion is supported by recent isotope data for cd dissolved in seawater and incorporated in cultured phytoplankton these results show that plankton features isotopically light cd while cd depleted surface waters typically exhibit complimentary heavy cd isotope compositions seawater samples from below 900 m depth display a uniform and intermediate isotope composition of e114 110cd 3 3 0 5 this study investigates whether ferromanganese fe mn crusts are robust archives of deep water cd isotope compositions to this end cd isotope data were obtained for the recent growth surfaces of 15 fe mn crusts from the atlantic pacific indian and southern oceans and two usgs fe mn reference nodules using double spike multiple collector inductively coupled plasma mass spectrometry the fe mn crusts yield a mean e114 110cd of 3 2 0 4 2 se n 14 data for all but one of the samples are identical within the analytical uncertainty of 1 1e114 110cd 2 sd to the mean deep water cd isotope value this indicates that fe mn crusts record seawater cd isotope compositions without significant isotope fractionation a single sample from the southern ocean exhibits a light cd isotope composition of e114 110cd 0 2 1 1 the origin of this signature is unclear but it may reflect variations in deep water cd isotope compositions related to differences in surface water cd utilization or long term changes in seawater e114 110cd the results suggest that time series analyses of fe mn crusts may be utilized to study changes in marine cd utilization

release of ni from birnessite during transformation of birnessite to todorokite implications for ni cycling in marine sediments abstract the phyllomanganate birnessite is the main mn bearing phase in oxic marine sediments where it exerts a primary control on the concentration of micronutrient trace metals in seawater however during sediment diagenesis and under mild hydrothermal conditions birnessite transforms into the tectomanganate todorokite we have recently shown that the transformation of birnessite to todorokite proceeds via a four stage nucleation and growth mechanism beginning with todorokite nucleation then crystal growth from solution to form todorokite primary particles followed by their self assembly and oriented growth via oriented attachment to form crystalline todorokite laths culminating in traditional crystal ripening atkins et al 2014 here we determine the fate and mobility of ni sorbed by birnessite during this transformation process specifically in our recent work we predict that the presence of ni within the phyllomanganate matrix will disrupt the formation of todorokite primary particles as such contrary to current understanding we suggest that ni sorbed by birnessite will slow the transformation of birnessite to todorokite and or be released to marine porewaters during sediment diagenesis here we transform a synthetic poorly crystalline ni sorbed 1 wt ni hexagonal birnessite analogous to marine birnessite into todorokite under a mild reflux procedure developed to mimic marine diagenesis and mild hydrothermal conditions we characterise our birnessite and reflux products as a time series including x ray diffraction xrd high resolution transmission electron microscopy hr tem and extended x ray absorption fine structure exafs spectroscopy in addition we determine ni speciation and mineral phase associations in a suite of natural marine ferromanganese precipitates containing intermixed phyllomanganate and todorokite our work shows for the first time that ni significantly slows the transformation of birnessite to todorokite and reduces the crystallinity of the neo formed todorokite phase but does not alter the mechanism and pathway of todorokite formation compared to a ni free system furthermore in systems tending towards todorokite as the final diagenetic product we see that up to 50 of the ni originally sequestered by birnessite is released to solution during the transformation our work indicates that the transformation of birnessite to todorokite in oxic marine sediments likely provides a significant source of ni to marine sedimentary porewaters and potentially a hitherto unrecognized benthic flux of ni to seawater

u th dating of striated fault planes direct dating of brittle fault activity is of fundamental importance to tectonic reconstructions and paleoseismic studies one way to address this issue is by constraining the timing of fault striations but this requires a better understanding of the striation formation mechanism and associated mineralization we present results from a microstructural geochemical and geochronological study of calcite precipitates associated with striated fault planes from the dead sea fault zone in northern israel we recognize four types of coexisting calcite precipitates including calcite cement in dilation breccia calcite in striated groove morphology calcite gouge associated with hydraulic fracturing and pressure solution and calcite coating of the fault surface carbon oxygen isotopes 87sr 86sr ratios and rare earth element and yttrium rey patterns indicate various precipitation mechanisms associated with formation of syntectonic calcite cement and striations coseismic calcite gouge and interseismic calcite coating precipitates in the fault zone using u th dating of samples from three adjacent fault planes we delineate four welldefined deformation ages in the period from 220 to 60 ka we conclude that these ages constrain the timing of activity along the dead sea fault zone in northern israel and argue that a similar methodological approach could potentially shed light on the timing of deformation in other brittle fault zones

palaeoseismology of the north anatolian fault near the marmara sea implications for fault segmentation and seismic hazard we conducted palaeoseismic studies along the north anatolian fault both east and west of the marmara sea to evaluate its recent surface rupture history in relation to the well documented historical record of earthquakes in the region and to assess the hazard of this major fault to the city of istanbul one of the largest cities in the middle east across the 1912 rupture of the ganos strand of the north anatolian fault west of the marmara sea we excavated 26 trenches to resolve slip and constrain the earthquake history on a channel fan complex that crosses the fault at a high angle a distinctive well sorted fine sand channel that served as a marker unit was exposed in 21 trenches totaling over 300 m in length isopach mapping shows that the sand is channelized north of the fault and flowed as an overflow fan complex across a broad fault scarp to the south realignment of the feeder channel thalweg to the fan apex required about 9 1 m of reconstruction study of the rupture history in several exposures demonstrates that this displacement occurred as two large events analysis of radiocarbon dates places the age of the sand channel as post ad 1655 so we attribute the two surface ruptures to the large regional earthquakes of 1766 and 1912 if each was similar in size then about 4 5 m of slip can be attributed to each event consistent with that reported for 1912 farther east we also found evidence for two additional surface ruptures after about ad 900 which probably correspond to the large regional earthquakes of 1063 and 1344 or 1354 these observations suggest fairly periodic occurrence of large earthquakes ri c 283 113 years for the past millennium and a rate of c 16 mm a if all events experienced similar slip we excavated six trenches at two sites along the 1999 izmit rupture to study the past earthquake history along that segment of the north anatolian fault one site located in the township of kosekoy east of izmit revealed evidence for three surface ruptures including 1999 during the past 400 years the other trench was sited in an ottoman canal that was excavated but never completed in 1591 there is evidence for three large surface rupturing events in the upper 2 m of alluvial fill within the canal at that site located only a few kilometres from the kosekoy site one of the past events is almost certainly the large earthquake of 1719 for which historical descriptions of damage are nearly identical to that of 1999 other earthquakes that could plausibly be attributed to the other recognized rupture of the izmit segment are the 1754 1878 or 1894 events all of which produced damage in the region and for which the source faults are poorly known our palaeoseismic observations suggest that the izmit segment of the north anatolia fault ruptures every one and a half centuries or so consistent with the historical record for the region although the time between ruptures may be as short as 35 years if 1754 broke the izmit segment release of about 4 m of seismic slip both west and east of the marmara sea this past century 1912 1999 support the contention that istanbul is at high risk from a pending large earthquake in that historical records suggest that the last large central marmara sea event occurred in 1766 there may be a similar 4 m of accumulated strain across the marmara basin segment of the north anatolian fault

nickel isotope fractionation during continental weathering abstract recent literature has documented systematic variations in the ni stable isotope compositions of several terrestrial and marine reservoirs of this bioessential trace metal for example dissolved ni in the world s major rivers has been shown to be more enriched in heavy isotopes than the continental rocks from which that ni was derived cameron and vance 2014 geochim cosmochim acta 128 195 211 this observation implies that one or more chemical reactions occurring during weathering of ni rich rock drives stable isotope fractionation that results in retention of lighter isotopes of ni associated with solid phases we present new ni isotope analyses of samples from various horizons of the webster addie laterite near democrat north carolina usa as well as results from two sets of experiments designed to constrain the fundamental mechanism s driving the isotopic variation observed in that weathering profile bedrock samples dunite and talc rich altered dunite have 60 58ni values of 0 06 to 0 20 in excellent agreement with previous research a sample of yellow laterite is enriched in lighter isotopes of ni with 60 58ni 0 21 mixed phase samples containing quartz and traces of serpentine goethite and smectite range from 0 13 to 0 35 experimental leaching of ni from olivine in dilute acid at ambient conditions results in no resolvable fractionation indicating that initial release of ni to solution from bedrock is not responsible for the isotope variation we observe in the natural samples sorption of ni onto montmorillonite a minor secondary weathering product present in laterites is associated with a very small fractionation of 0 11 0 09 with lighter isotopes sorbed on the smectitic clay such adsorption can thus account for some but not all of the isotope systematics observed in the weathering profile given previous evidence that sorption of ni to fe oxyhydroxides does drive a fractionation of appropriate sense and magnitude wasylenki et al 2015 chem geol 400 56 64 we infer that oxidation of fe2 released from bedrock and precipitation result in retention of a light pool of ni in solid weathering products thereby enriching dissolved ni in heavier isotopes because much of the continental crust s ni budget is hosted by mafic and ultramafic rocks which weather very rapidly at earth s surface and for which fe oxyhydroxides are extremely common weathering products this ni fractionation mechanism may be relevant for terrestrial weathering of ni bearing rocks in general even though the overall mineralogy and chemistry of weathering profiles varies with parent lithology and environmental conditions secondary hydrous ni rich mg silicates from veins in the saprolite zone are enriched in heavy isotopes with 60 58ni 0 29 to 0 86 similar ni rich mg silicate samples from several similar profiles around the world display a similar range from 0 36 to 0 90 suggesting that the processes responsible for isotopic fractionation at the north carolina locality are general phenomena characteristic of laterites worldwide we hypothesize that in laterites continual downward percolation of meteoric waters and progressive chromatographic exchange with goethite bound ni progressively shifts the ni contents of solids toward lighter and fluids toward heavier isotopic compositions when fluids reach the mg rich si rich saprolite zone isotopically heavy garnierite minerals precipitate in veins the phenomena we report and discuss here may long have been the dominant controls on the distribution of ni isotopes in earth s near surface terrestrial environment at least since oxygenation of the atmosphere due to lack of abundant oxygen in air and water earlier in earth history the biogeochemical cycle of ni isotopes was almost certainly rather different such that riverine dissolved ni was not necessarily enriched in heavy isotopes relative to continental crust and the oceans may not have been so highly enriched in heavy isotopes of ni as they are presently

hydrothermal manganese plumes in the mid atlantic ridge rift valley the concentration of dissolved manganese in sea water can be used as a chemical tracer of hydrothermal activity on the underlying sea floor here we present vertical profiles of seawater manganese concentrations above the rift valley of the mid atlantic ridge mar the values obtained indicate the presence of plumes that are presently active generated by hydrothermal vents in the rift valley these plumes are confined to the rift valley and do not spill over into the adjacent deep ocean basins differences between them suggest that there are at least five hydrothermal sources along this 1 700 km long section of mid ocean ridge

macronutrient and trace metal geochemistry of an in situ iron induced southern ocean bloom abstract we have investigated the effect of iron supply and increased phytoplankton growth on the cycling of the macronutrients phosphate nitrate and silicic acid as well as the micronutrients copper cu nickel ni zinc zn and cadmium cd nutrient levels were measured in situ in an iron induced phytoplankton bloom at 61 s 140 e in the southern ocean iron release experiment soiree nutrient ratios upon arrival at the study site indicate that much of the seasonal phytoplankton productivity was by iron limited diatoms growing at low mean light levels the addition of iron fe induced a bloom that led to a draw down in the macronutrients in ratios consistent with the growth of diatoms under iron replete conditions none of the bioutilised trace metals cu ni zn or cd showed any indication of co limitation with fe of phytoplankton growth zn concentrations did not decrease by algal uptake as expected cd was partitioned to the particulate phase indicating consumption by the algae cd was preferentially utilised with respect to p with a cd p 5 8 interpretation of the cd ca data from the sedimentary record using this higher induced cd p value would imply even higher southern ocean surface water p during the last glacial maximum

nickel isotopic variation in black shales from bohemia china canada and finland a reconnaissance study we present 60ni values for black shales determined by double spike mc icp ms the samples comprise paleoproterozoic talvivaara ni zn co cu black shales from finland neoproterozoic black shales from the tepla barrandian unit czech republic early cambrian ni mo rich black shales from the yangtze craton and devonian ni zn pge black shales from yukon canada in addition the sample set includes a black smoker sample from the logatchev hydrothermal field mid atlantic ridge the 60ni values vary from 0 84 0 09 to 0 62 0 04 2sd with a median of 0 10 n 28 ni isotopic compositions were predominantly lighter than those of abiotic terrestrial and extraterrestrial samples 0 15 and 0 27 mantle 0 23 gall et al 2017 present day seawater 1 44 cameron and vance 2014 dissolved ni from riverine input 0 84 cameron and vance 2014 ferromanganese crusts 0 9 2 5 gall et al 2013 devonian mississippian organic rich marine sediments lower jurassic organic rich marine sediments 0 2 2 5 average 0 92 n 18 porter et al 2014 and euxinic sediments of the black sea 0 14 0 51 vance et al 2016 however the range of 60ni values in our black shale samples was close to that of the weathering products of mafic ultramafic rocks ore and soil samples ranging from 0 60 to 0 30 ratie et al 2015 spivak birndorf et al 2018 ni sulfide ores hosted by archean komatiites from australia and canada 0 10 to 1 03 average 0 70 n 8 gueguen et al 2013 and archean ni rich magmatic sulfides from zimbabwe 0 28 to 0 47 n 6 hoffman et al 2014 based on our observations and considering the extremely low contribution of direct biological uptake of ni and a dominant ni residence in early fe ni sulfides we suggest that our mostly light ni isotopic compositions in metal rich black shales result from sulfidization of organic matter and ni removal into sulfides

ni isotope fractionation during sorption to ferrihydrite implications for ni in banded iron formations abstract a major decline in marine methanogen populations during the late archaean eon has been proposed as a driver for the great oxidation event goe at 2 4 ga konhauser et al 2009 nature 458 750 753 recently hypothesized that a dramatic decrease between 2 7 and 2 4 ga in the concentration of dissolved ni an essential nutrient for methanogens may have been responsible for the decline to test that hypothesis ni stable isotopes a novel proxy for methanogen ni limitation will be applied to the late archaean paleoproterozoic rock record in the future possibly through analysis of banded iron formations bifs in order to facilitate interpretation of those data we investigated the fractionation of ni stable isotopes during sorption to synthetic ferrihydrite which was likely the primary precipitating phase during bif deposition via bench top experiments the observed fractionations for adsorption and coprecipitation experiments were indistinguishable and averaged 60 58nidissolved sorbed 0 35 0 10 1 sd light ni sorbed parallel linear trends in isotope compositions of dissolved and sorbed ni as a function of fraction of ni sorbed indicate an equilibrium isotope effect with rapid and continuous exchange between dissolved and sorbed ni additionally we observed fractionation of 60 58nidissolved sorbed 0 23 0 07 1 sd in experiments in which ferrihydrite had been aged for up to 30 days and had partially transformed to goethite and hematite thus the fractionations in all of our experiments are the same within uncertainties although our simple system differs from archaean seawater our results suggest that ferrihydrite precipitating to form bifs may always have been offset by a constant fractionation from coexisting dissolved ni in seawater

faulting associated with historical and recent earthquakes in the eastern mediterranean region summary this paper summarizes evidence for surface faulting in historical and recent earthquakes in the eastern mediterranean region and in the middle east such information is particularly important for studies of active tectonics and for palaeoseismology we have found 78 cases of faulting pre 1900 and 72 post 1900 some of which show that faults that have apparently been inactive this century had already ruptured before 1900 for some cases faulting could not have been predicted from 20th century activity and in others it could have been expected but has not been observed during the instrumental period the data are suycient to allow the derivation of relationships between magnitude and rupture length

uptake of elements from seawater by ferromanganese crusts solid phase associations and seawater speciation marine fe mn oxyhydroxide crusts form by precipitation of dissolved components from seawater three hydrogenetic crust samples one phosphatized and two hydrothermal mn oxide samples were subjected to a sequential leaching procedure in order to determine the host phases of 40 elements those host phase associations are discussed with respect to element speciation in seawater the partitioning of elements between the two major phases mn oxide and fe oxyhydroxide can in a first order approximation be explained by a simple sorption model related to the inorganic speciation of the elements in seawater as has been proposed in earlier models free and weakly complexed cations such as alkali and alkaline earth metals mn co ni zn tl i and partly y are sorbed preferentially on the negatively charged surface of the mno2 in hydrogenetic crusts the driving force is a strong coulombic interaction all neutral or negatively charged chloro cd hg tl carbonate cu y pb and u and hydroxide be sc ti fe zr nb in sn sb te hf ta bi th and tl iii complexes and oxyanions v cr as se mo and w bind to the slightly positively charged surface of the amorphous feooh phase while coulombic interaction can explain the sorption of the negatively charged species the binding of neutral species is based on specific chemical interaction organic complexation of elements in deep ocean water seems to be at most of minor importance surface oxidation can explain some strong metal associations e g of co and tl with the mno2 and te with the feooh sorption reactions initially driven by coulombic forces are often followed by the formation of specific bonds between the adsorbate and the atoms of the oxide surface differences in the associations of some metals between the non phosphatized and phosphatized hydrogenetic crusts and between the hydrogenetic and the hydrothermal samples reflect the different physico chemical environments of formation and speciations in oxic seawater vs less oxic fluids especially for the redox sensitive metals such as mo and v these environmental related differences indicate that the methodology of chemical speciation used here in combination with spectroscopic methods may allow for the detection of changes in paleoceanographic conditions recorded during the several tens of millions of years of crust growth

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

crystal chemistry of ni in marine ferromanganese crusts and nodules marine ferromanganese crusts and nodules are highly enriched in transition metals such as ni and co yet the crystal chemistry and mode of incorporation of these metals is poorly known we characterized the crystal chemistry of ni in two hydrogenetic pacific ocean ferromanganese crust samples and a hydrogenetic nodule from the madeira abyssal plain energy dispersive spectrometry shows that ni is associated with the manganese oxide phases in agreement with previous work x ray diffraction patterns show that the dominant mn3 4 oxide is a phyllomanganate similar to hexagonal birnessite or mno2 extended x ray absorption fine structure spectroscopy shows that the coordination environment of ni results from structural incorporation into the phyllomanganate phase by replacement of mn3 4 in contrast ni initially sorbs to freshly prepared synthetic birnessite by surface complexation over vacancy sites in the mno2 layer we propose that the transformation of ni sorption from surface complexation to structural incorporation provides a potentially irreversible sink for ni in seawater

morphology displacement and slip rates along the north anatolian fault turkey 1 geological and geomorphological offsets at different scales are used to constrain the localization of deformation total displacement and slip rates over various timescales along the central and eastern north anatolian fault naf in turkey the naf total displacement is reevaluated using large rivers valleys 80 15 km and structural markers pontide suture 85 25 km tosya vezirkopru basins 80 10 km these suggest a neogene slip rate of 6 5 mm yr over 13 myr the river network morphology shows offsets at a range of scales 20 m to 14 km across the main fault trace and is also used to estimate the degree to which deformation is localized at a smaller scale the morphology associated with small rivers is offset by 200 m along the naf the age of these features can be correlated with the holocene deglaciation and a slip rate of 18 3 5 mm yr is determined this is consistent with a rate of 18 5 mm yr deduced independently from the 14c dating of stream terrace offsets over the short term gps data gives a similar rate of 22 3 mm yr all our results tend to show that most of the deformation between the anatolian and eurasian lithospheric plates has been accommodated along or very close to the active trace of the naf the difference between the neogene and the holocene slip rate may be due to the recent establishment of the current plate geometry after the creation of the naf

stratigraphic controls on eformation patterns in fault related folds a detachment fold example from the sierra madre oriental northeast mexico abstract deformation patterns are described by the style intensity and distribution of structures throughout a volume of rock in fault related folds presently observed deformation patterns are controlled by structural factors like kinematic history environmental factors like burial history and stratigraphic factors like layer thickness and competence to demonstrate the role of stratigraphy in controlling fold related deformation patterns we document the stratigraphic variability of mesostructures at one structural position on a map scale detachment fold unique assemblages of faults fractures and cleavages in certain stratigraphic intervals define a mechanical stratigraphy comprised of several units each exhibiting a characteristic deformation response to the folding process the varying response of each mechanical unit suggests that folding mechanisms such as orthogonal flexure flexural slip or flexural flow were sequentially or coevally operative in each of the units using the simple theoretical strain distributions associated with each folding mechanism and the fact that each mechanical unit accommodates fold related strain by developing a characteristic set of mesostructures we are able to predict general deformation patterns elsewhere in the fold the significance of this approach is that it recognizes that even in a single structure fold kinematics and deformation response may be dramatically different in various parts of a stratigraphic section because of this the quality and character of reservoir rocks in anticlinal traps may change markedly over short stratigraphic distances predictions of fold related deformation based solely on fold kinematics are unlikely to resolve these variations

a first look at the distribution of the stable isotopes of silicon in natural waters the first data on the distribution of the stable isotopes of silicon in marine and freshwater systems are reported both marine and riverine 30si are more positive than 30si of igneous rocks suggesting isotopic fractionation during weathering and clay formation and or biomineralization the 30si value for dissolved silicic acid from several ocean basins is 1 1 0 3 n 69 more positive values are found in surface waters due to discrimination against 30si during biogenic opal formation by diatoms the deep pacific ocean is depleted in 30si relative to the deep atlantic by roughly 0 4 30si of riverine dissolved silicon averages 0 8 0 3 n 8 the biologic fractionation of silicon isotopes coupled with effects associated with thermohaline circulation appears to play a significant role in controlling the distribution of silicon isotopes in the sea the average 30si value of inputs of silicon to the ocean most likely falls between 0 3 and 0 9 and that of the outputs falls between 0 9 to 1 9 probably in the neighborhood of 1 0

the mineralogy and geochemistry of the cerro matoso s a ni laterite deposit montelibano colombia the cerro matoso s a ni laterite deposit in northwest colombia is an important producer of ferronickel expanded production of ferronickel is planned to be 55 000 mt by mid 2004 the deposit is developed over a peridotitic protolith that is exposed in the form of an elongated hill the deposit s weathering profile is variable both vertically and laterally and 10 distinct lithostratigraphic units have been characterized two typical sections through the weathering profile were sampled from an area of the mine with high pit 1 and lower pit 2 ni grades bench mapping has shown that pits 1 and 2 have distinctly different weathering profiles from bottom to top the profile in pit 1 is weakly serpentinized peridotitic protolith saprolitized peridotite green saprolite main ore horizon tachylite used by mine geologists to describe an enigmatic fe oxide horizon black saprolite yellow laterite red laterite the sequence is then capped by a magnetic to nonmagnetic ferricrete known locally as canga the succession in pit 2 is from serpentinized peridotite saprolitized peridotite brown saprolite yellow laterite red laterite and lacks the green saprolite ore horizon all the units in pit 2 have currently uneconomic ni grades the thickness of the units is highly variable but most of the major horizons have maximum thicknesses of the order of tens of meters both pits contain abundant fault and joint related silicate veins sometimes in stockworks in the lower part of the sequence these veins contain the distinctive green mineral known as garnierite actually pimelite a form of nickeliferous talc as well as quartz and chalcedony and they can have a ni content of up to 30 to 40 wt percent the bulk geochemistry in most units of both profiles shows a fairly typical ni laterite pattern in which mgo and sio2 are depleted toward the top of the sequence whereas feo increases mineralogic studies confirm that the protolith in both pits is a partly up to 50 serpentinized harzburgite and that in pit 1 the main ni bearing phases in the weathering profile are ni sepiolite ni serpentines and other hydrous silicates the garnierites in cerro matoso have been identified as pimelite in which various amounts of ni have substituted for mg the upper part of the sequence is dominated by amorphous and crystalline fe oxide phases the magnetic canga is composed mainly of maghemite that may have been produced by oxidation of magnetite rich units the mineral content of pit 2 is dominated by poorly structured fe oxides or goethite and by subordinate clay minerals and quartz the geochemistry and mineral content of the deposit suggest that as in many other ni laterite deposits ore genesis is strongly controlled by local climate topography and drainage mass balance calculations indicate that the profiles in pits 1 and 2 had different weathering histories because the degree of profile collapse and residual enrichment in pit 1 is far more extreme than that in pit 2 this difference may be the result of different degrees of serpentinization of the protolith in the two pits and potential dilution of the ore in pit 2 by input from an exotic unit ni in the deposit has also undergone supergene enrichment resulting from the leaching of ni from the upper part of the lateritic profile and its transport to the green saprolite unit where the ni was fixed in silicate minerals

a 2500 yr long paleoseismologic record of large infrequent earthquakes on the north anatolian fault at cukurcimen turkey paleoseismologic trenches excavated across the north anatolian fault near the village of cukurcimen in north central turkey yield a complete record of surface ruptures for the past 2500 yr the trenches provide mutually consistent evidence for the timing of the five most recent surface ruptures at the site as well as at least two older events these are interpreted as 1 the historic 1939 m w 7 9 earthquake 2 the historic 1254 a d earthquake 3 the historic 1045 a d earthquake 4 an earthquake that probably occurred late in the interval between 250 and 540 a d possibly the historic 499 a d earthquake and 5 an earthquake that occurred sometime between 770 and 50 b c and probably between 230 and 50 b c one additional earthquake occurred sometime between 1450 and 800 b c and at least one other surface rupture occurred between 2880 and 200 b c but the stratigraphic section at the site was not completely exposed for sediments older than 2500 yr as a result it is unclear whether the oldest event horizons represent a single earthquake or multiple events our findings when coupled with other published results and the historical record enable us to construct a space time history of earthquakes along the north anatolian fault the most striking aspects of this analysis are 1 the rarity of earthquakes at any given place along the fault suggesting that the fault typically ruptures in large infrequent events 2 earthquake occurrence is relatively temporally regular with inter event times that range from 200 to 900 yr and vary by a factor of only 3 4 and 3 almost the entire length of the north anatolian fault ruptured in short lived clusters of activity in the seventeenth to eighteenth centuries and in the tenth to twelfth centuries similar to the twentieth century sequence the magnitude and sequence of the individual ruptures however have varied considerably between clusters moreover the paleoseismologic and historical data indicate that the north anatolian fault does not always rupture in sequences similar to the twentieth century cluster these results suggest that the relatively regular recurrence of rare large magnitude earthquakes may be the expected mode of earthquake occurrence on mature strike slip faults in settings where such faults are structurally isolated from other major seismic sources

the influence of organic complexation on ni isotopic fractionation and ni recycling in the upper soil layers abstract the quantification of ni isotopic fractionation induced by ni binding to organic acids is a preliminary step to better constrain the mechanisms determining ni isotopic fingerprint observed in surface soils waters and plants as well as the contribution of metal recycling during plant litter degradation in this study ni isotopic fraction induced by reaction with small organic acids e g citric and oxalic acids and with soil purified humic acids pha was investigated at different ni l ratio and ph conditions the donnan membrane technique was used to separate ni bound to organic ligands from the free metal obtained results highlighted that ni binding with carboxylic groups produces in the adopted experimental conditions a 60nibond free

nickel exchange between aqueous ni ii and deep sea ferromanganese nodules and crusts abstract deep sea ferromanganese fe mn nodules and crusts are rich in traditional and non traditional metals with both current and emerging economic value mn iii iv oxides e g phyllomanganates are important host phases for these metals e g ni which are structurally incorporated during nodule and fe mn crust formation recrystallization of phyllomanganates can be catalyzed by aqueous mn ii mn ii aq during bio geochemical mn redox cycling the fate of structurally incorporated metals during such recrystallization of mn iii iv oxides remains however poorly constrained here we use a 62ni isotope tracer to determine the exchangeability of dissolved ni with structurally incorporated ni in two deep sea fe mn nodules and one fe mn crust ni exchange between solid and solution was investigated during reactions in 1 mm mn ii aq and in mn ii free solutions under variable ph conditions ph 5 5 and 7 5 over time sample characterization shows that all samples are of hydrogenetic or mixed hydrogenetic diagenetic origin and ni is preferentially associated with the phyllomanganates our ni exchange experiments reveal that in some samples up to 25 of incorporated ni is exchangeable with the fluid after 14 days the prevalent reaction pathways exhibit ph dependent behavior during phyllomanganate recrystallization and differ between sample types with mn ii aq enhancing ni exchange in the fe mn crust fluid system and ni exchange being independent of mn ii aq concentrations in the fe mn nodule fluid systems the exchangeability of structurally incorporated ni in fe mn nodules and crusts indicates a labile behavior that potentially makes it available for biogeochemical processes in the marine environment

initiation and growth of gypsum piercement structures in the zechstein basin abstract the importance of tectonic processes in initiating halite diapirs has become much better understood in recent years less well understood is the development of diapiric structures involving rocks composed predominantly of gypsum below about 1000 m gypsum dehydrates to anhydrite which often obscures primary sedimentary textures if the strain associated with diapiric rise in the rock induces the transition to anhydrite obliteration of primary features in the gypsum can be expected in our study we infer that the diapiric movement in the werra anhydrite member of cycle 1 of the zechstein formation of europe occurred before the initial transition of gypsum to anhydrite based on the presence of pseudomorphs of bedded primary gypsum crystals the overburden lithologies and depositional environment and the mechanical properties of gypsum anhydrite and carbonate rocks faulting and differential loading of a shallow overburden were the key components in initiating the gypsum diapirism the transition to anhydrite occurred after burial and after cessation of diapirism in comparison the diapirism of calcium sulfate of the leine anhydrite into the leine halite members of cycle 3 of the zechstein formation probably occurred much later after burial and appears to have been triggered by halite diapirism which in turn triggered the dehydration reaction causing the calcium sulfate to become the incompetent phase relative to the halite

towards balancing the oceanic ni budget abstract nickel isotopes are a novel and promising tracer of the chemistry of past ocean environments but realisation of this tracer s potential requires a comprehensive understanding of the controls on ni burial in the marine sedimentary archive an outstanding puzzle in the marine budget of ni first recognised in the 1970s is a major imbalance in the known inputs and outputs to and from the ocean the sedimentary outputs of ni are much larger than the inputs rivers dust much more recently it has also been recognised that the outputs are also considerably isotopically heavier than the inputs in this study we find light ni isotope compositions 60 ninist srm986 0 2 to 0 8 for mn rich sediments from the eastern pacific compared to fe mn crusts at about 1 6 these data suggest that diagenetic remobilisation of isotopically heavy ni leads to a significant benthic ni flux estimated at 0 6 2 3 10 8 mol yr similar in magnitude to the riverine flux to the ocean diagenetic remobilisation of ni may occur either via cycles of mn oxide dissolution and precipitation with associated ni sorption and release or during mineralogical transformation of birnessite to todorokite a minor role for retention of isotopically light ni by fe oxides or fe rich authigenic clays is also proposed overall a benthic flux of isotopically heavy ni at about 3 can balance the marine ni budget pinpointing diagenesis as a key missing piece of the ni puzzle

hydrothermal co2 degassing in seismically active zones during the late quaternary natural co2 discharges are abundant in turkey as evident from ongoing deposition of recent terrace mound travertines and emplacement of significant travertine vein and breccia deposits in fractured damage zones of active fault systems we report high precision u series age data for the vein carbonates combined with important field observations and geochemical data to evaluate the travertine veining and co2 degassing history in seismically active areas field evidence suggests that travertine filled veins and associated breccias represent hydrothermal eruption products which probably formed by hydraulic fracturing in response to overpressure of co2 rich fluids stable isotope and ree data support the field observations and indicate that travertine veins formed as thermogene deposits from rapidly ascending co2 rich fluids travertine veins from the kirsehir geothermal field give u series ages in a range from 10 6 0 3 ka to 86 16 1 24 ka with a majority of ages failing between 10 6 0 3 and 11 3 0 2 ka vein samples from the pamukkale geothermal field yield u series ages between 21 1 0 1 ka and 73 6 0 6 ka two major age groups are evident in pamukkale that cluster coherently around 21 ka and 25 ka a large number of travertine veins we dated by high precision u series technique coincide with times of cold dry climate events this is different from surface sinter deposits in geothermal fields which more frequently form during warm and wet periods we propose that a significant reduction in surface discharge of co2 by spring or geothermal waters during dry climate periods may promote oversaturation of co2 in deep reservoirs host rock fracturing in response to seismic shaking and fluid overpressure results in rapid exsolution and expansion of the dissolved gas and may lead to hydrothermal eruptions crown copyright c 2009 published by elsevier b v all rights reserved

u th age evidence from carbonate veins for episodic crustal deformation of central anatolian volcanic province abstract central anatolia represents one of the most outstanding examples of intraplate deformation related to both continental collision and back arc extension generating non uniformly distributed stress fields in this study we provide direct field evidence of various stress directions and investigate carbonate filled fracture systems in the central anatolian volcanic province using u th geochronology and isotope geochemistry for evaluating the episodes of latest volcanic activity under regional stress field data reveal two independent fracture systems in the region successive fracture development has been controlled by two different volcanic eruption centers hasandag composite volcano and acigol caldera trace element and stable c and o and radiogenic sr isotope compositions of carbonate veins indicate different fluid migration pathways for two different fracture systems the u th age data for carbonate veins of two independent fracture systems indicate that the crustal deformation intensified during 7 episodic periods in the last 150 ka the nne trending first fracture system was formed as a result of strain cycles in a period from 149 2 5 through 91 1 5 to 83 2 5 ka bp subsequent deformation events represented by the ene trending second fracture zone have been triggered during the period of 53 3 5 44 0 6 and 34 1 ka bp before the first fracture zone resumed the activity at about 4 7 0 15 ka bp although further studies are needed to evaluate statistical significance of age correlations the periods of carbonate precipitation inferred from u th age distributions in this study are comparable with the previous dating results of surrounding volcanic eruption events

seismic hazard in the marmara sea region following the 17 august 1999 izmit earthquake on 17 august 1999 a destructive magnitude 7 4 earthquake occurred 100 km east of istanbul near the city of izmit on the north anatolian fault this 1 600 km long plate boundary 1 2 slips at an average rate of 2 3 cm yr 1 refs 3 5 and historically has been the site of many devastating earthquakes 6 7 this century alone it has ruptured over 900 km of its length 6 models of earthquake induced stress change 8 combined with active fault maps 9 had been used to forecast that the epicentral area of the 1999 izmit event was indeed a likely location for the occurrence of a large earthquake 9 10 here we show that the 1999 event itself significantly modifies the stress distribution resulting from previous fault interactions 9 10 our new stress models take into account all events in the region with magnitudes greater than 6 having occurred since 1700 ref 7 as well as secular interseismic stress change constrained by gps data 11 these models provide a consistent picture of the long term spatio temporal behaviour of the north anatolian fault and indicate that two events of magnitude equal to or greater than the izmit earthquake are likely to occur within the next decades beneath the marmara sea south of istanbul

slip distribution along the north anatolian fault associated with the large earthquakes of the period 1939 to 1967 abstract between 1939 and 1967 six large fault ruptures formed a westward migrating sequence of events along a 900 km long nearly continuous portion of the north anatolian fault for these events the 1939 erzincan 1942 niksar erbaa 1943 tosya 1944 bolu gerede 1957 abant and 1967 mudurnu valley earthquakes i have compiled a record of dextral slip which contains nearly 100 points these data indicate that the amount of slip is irregularly distributed along the 1939 to 1967 rupture zone the maximum slip 7 5 m occurred during the 1939 earthquake in the eastern 150 km of the 900 km long rupture zone dextral offsets diminish very abruptly eastward but very gradually westward the rate of westward decrease in the 1939 to 1967 offsets is only slightly greater than the rate of westward decrease of post miocene displacement along the north anatolian fault this suggests that westward decrease in slip can be expected to be a general characteristic of earthquake ruptures along the north anatolian fault in the future nevertheless within the 1939 to 1967 slip distribution there are three regions that had less slip than the neighboring regions these i interpret as possible sites of large future earthquakes one of these seismic gaps has already experienced another earthquake in 1951 and subsequent creep

evaporite diapirs in the la popa basin nuevo leon mexico reconnaissance mapping and stratigraphic work in the la popa basin of nuevo leon northern mexico has revealed two large structural features with cores of gypsum and anhydrite at the surface these features are interpreted to be the surface expression of evaporite diapirs they are exposed in folded sedimentary rocks belonging to the potrerillos formation of the difunta group of maastrichtian age late cretaceous sandstone units within the potrerillos formation pinch out toward the piercement features carbonate lentils composed of rudistid reefs and associated carbonate clastics flank the features and pinch out away from the features into marine shale members of the potrerillos formation most carbonate lentils occur in the immediate vicinity of the evaporite features and are interpreted to be genetically related to the diapirs syndiapiric sedimentary facies patterns can be documented over 4 000 vertical feet 1 200 m of section within the potrerillos formation the large vertical extent of facies peculiarities near the piercement features indicates that the features were active for an extended period corresponding to at least two regressive transgressive cycles during maastrichtian time a radial drainage pattern away from the northern feature indicates that the features are probably active today a limestone inclusion from within one of the features has been dated as kimmeridgian in age zuloaga or smackover equivalent and suggests that the evaporites are probably derived from the jurassic minas viejas formation it is not known at present whether salt underlies the surface crust of gypsum and anhydrite at the time that the first syndiapiric sediments of the potrerillos formation were deposited the minas viejas formation was buried at an estimated depth of 17 000 ft 5 200 m the thick pre laramide cover the pre laramide age of at least some of the syndiapiric sedimentary features and the location of stocks away from major anticlines indicate that the emplacement of the diapirs is not related to laramide compression geostatic loading is considered to be the most important mechanism for emplacement of the domes

sequential leaching of marine ferromanganese precipitates genetic implications abstract sequential leaching experiments were carried out on twenty one hydrogenetic crust samples from different locations in the central pacific and the results are compared with four crust and nodule samples of different genetic origin fe vernadite mno2 is the most important minor and trace metal bearing mineral phase and shows high concentrations of co ni cd ti ba zn and cu which are present in seawater mainly as hydrated and labile complexed cations elements forming carbonate and hydroxide complexes and oxyanions in seawater like pb mo v and minor proportions of cu and zn are bound in the fe00h fraction the ca carbonate phase and the residual fraction which consists of aluminosilicates and crystalline oxides show only minor heavy metal associations e g cu and zn only a small part of the high ti concentrations in hydrogenetic crusts is of detrital origin ti mainly forms a hydrogenetic phase probably consisting of ti02 2h20 intergrown with the amorphous fe00h phase analyses of different sample types and crust layers show that aging and diagenetic effects can change the phase associations of some elements the most notable change was observed for pb which during phosphatization of crusts is transferred from the mn fe oxide fraction to the apatite fraction a colloid chemical model for the hydrogenetic precipitation of ferromanganese crusts on seamounts is proposed in the first stage mn2 rich water from the oxygen minimum zone is mixed with oxygen rich deep water and oxidized mn iv and other metals like fe ti al and si form oxide and hydroxide colloids these form mixed colloidal phases and scavenge trace metals by sorptive processes which are dominated by coulombic and chemical interactions between colloid surfaces and dissolved metal species in stage two the colloidal phases precipitate on the substrate rocks of the seamounts as ferromanganese oxide encrustations incorporating the sorbed heavy metals into the mineral phases

salt diapir influenced shallow marine sediment dispersal patterns insights from outcrop analogs unique outcrop exposures of two salt diapirs a secondary salt weld and associated syndiapiric strata in northeast mexico offer an important perspective on salt influenced petroleum reservoirs by allowing recognition and description of salt related sandstone depocenters spectacular progressive unconformities and halokinetic sequences coupled with laterally continuous exposures permit accurate correlation and interpretation of syndiapiric units analysis of the syndiapiric upper cretaceous delgado sandstone member potrerillos formation delineates regional shoreline sediment dispersal locally impacted by diapiric relief and the distribution and internal character of salt diapir proximal sandstone depocenters sequence stratigraphic correlation defines striking relationships between highstand hst and transgressive systems tracts tst stratal thinning trends and salt diapir relief transgressive systems tract and highstand systems tract strata show thinning and lithofacies shoaling trends toward diapirs however the latter is more pronounced in the hst and occurs at a greater distance from salt diapirs within 1 2 km 0 6 1 2 mi sandstone depocenters roughly 0 5 1 0 km 0 3 0 6 mi wide and 0 5 0 2 km 0 3 0 1 mi thick are present in both tst and hst strata and consist of sandier shallower water facies however depocenters are better developed in tst strata as thicker stratigraphic sections on updip diapir margins we propose that sandstone depocenters formed by preferential sediment reworking and shelf ridge development on landward diapir margins during marine transgression elevated diapir relief and higher subsidence rates adjacent to salt diapirs likely enhanced this process additionally depocenters adjacent to el papalote diapir are smaller and contain deeper water facies than the age equivalent depocenters adjacent to el gordo diapir suggesting that it had higher broader sea floor relief

the north anatolian fault a new look dedicated to the memory of three pioneers ihsan ketin sirri erinc and melih tokay and a recent student aykut barka who burnt himself out in pursuit of the mysteries of the north anatolian fault abstract the north anatolian fault naf is a 1200 km long dextral strike slip fault zone that formed by progressive strain localization in a generally westerly widening right lateral keirogen in northern turkey mostly along an interface juxtaposing subduction accretion material to its south and older and stiffer continental basements to its north the naf formed approximately 13 to 11 ma ago in the east and propagated westward it reached the sea of marmara no earlier than 200 ka ago although shear related deformation in a broad zone there had already commenced in the late miocene the fault zone has a very distinct morphological expression and is seismically active since the seventeenth century it has shown cyclical seismic behavior with century long cycles beginning in the east and progressing westwa

seismic cycles recorded in late quaternary calcite veins geochronological geochemical and microstructural evidence southwest turkey is seismically active as a result of the hellenic subduction process in the eastern mediterranean we conducted high resolution micro sampling high precision u series dating and microchemical analysis on an extensional vein system in a tectonically active but non hydrothermal area u th age data and microscopic observations provide evidence of repeated fracturing of a previously sealed crack system followed by a new increment of veining repeated injection of veinlets suggests that the vein system was formed by the crack seal mechanism four major u th age groups for the emplacement of the vein system fall between 23 9 0 2 ka and 23 2 0 4 ka 21 7 0 4 ka and 19 2 0 2 ka 17 3 0 1 ka and 16 2 0 3 ka and at 11 8 0 2 ka stable and sr isotope geochemistry of the calcite vein samples indicates that surface water interacting with the soil cover was the major component of the groundwater system from which the extensional veins precipitated trace element and 0 isotope data of the vein system are interpreted to reflect carbonate precipitation associated with seismic cycles involving fluids with different trace element compositions and co2 contents initial carbonate precipitation during a single seismic cycle occurred from co2 dominated fluids that were degassed from the original co2 water mixture this was followed consecutively by carbonate precipitation from the remaining water which was relatively impure with higher trace element contents millimetre to submillimetre scale u series dating in conjunction with geochemistry of carbonate veins related to active tectonism offers an innovative means of constraining the absolute timing of late quaternary seismic and inter seismic events c 2010 elsevier b v all rights reserved

sorption of ni by birnessite equilibrium controls on ni in seawater abstract synthetic hexagonal birnessite hx birnessite is a close analogue to natural poorly crystalline phyllomanganate phases found in soils and marine ferromanganese deposits these phases are often highly enriched in trace metals such as ni and co we measured the sorption of ni ii onto synthetic hexagonal birnessite hx birnessite from ph 1 to 7 exafs spectra show that at ph 3 7 ni is adsorbed to the hx birnessite surface above vacancy sites on 001 as a tridentate corner sharing complex we developed a surface complexation model for ni adsorption based on the equilibria 3 mn 2 o 2 3 ni 2 mn 2 o 3 ni 0 3 mn 2 o 2 3 ni 2 h 2 o mn 2 o 3 ni oh h using this surface complexation model we predict the concentration of ni in seawater in equilibrium with ni bearing birnessite found in hydrogenetic femn crusts and nodules our predicted results are in good agreement with observed ni concentrations in seawater and suggest that the concentration of dissolved ni in seawater is buffered by sorption to birnessite or a related mno 2 phase however in addition to the surface complex ni also sorbs by structural incorporation into the vacancy site in our synthetic samples at ph 7 exafs shows 10 of ni is structurally incorporated into hx birnessite in natural birnessites found in marine ferromanganese crusts and nodules exafs shows that all of the sorbed ni is structurally incorporated structural incorporation suggests that ni sorption may be irreversible

halokinetic sequences and diapiric structural kinematics in the field two day excursion to la popa basin northeastern mexico exposures of salt diapirs and flanking strata in la popa basin in the mexican states of nuevo leon and coahuila contain world class examples of salt sediment interaction that provided the basis for the concept of halokinetic sequences the basin also contains one of the first secondary salt welds described in outcrop the two day field trip described here provides an easily accessible overview of salt sediment relations within a short distance of monterrey the capital city of nuevo leon the first day constitutes an introduction to basin stratigraphy a traverse through halokinetic sequences at el papalote diapir and visits to the cretaceous paleogene boundary bed and a salt cored detachment fold near the town of hidalgo north of monterrey the second day is a visit to la popa salt weld where stops at several parts of the weld permit comparison of different structural styles developed along the weld the trip begins and ends at the marriott courtyard hotel near the monterrey airport

a surprising asymmetric paleothermal anomaly around el gordo diapir la popa basin mexico thirty seven mudstone samples were collected from the uppermost lower mudstone member of the potrerillos formation in el gordo minibasin within la popa basin mexico the unit is exposed in a circular pattern at the earth s surface and is intersected by el gordo diapir in the northeast part of the minibasin vitrinite reflectance ro results show that samples along the eastern side of the minibasin i e south of the diapir are mostly thermally immature to low maturity ro ranges from 0 53 to 0 64 vitrinite values along the southern western and northwestern part of the minibasin range between 0 67 and 0 85 values of ro immediately northwest of the diapir are the highest reaching a maximum of 1 44 the results are consistent with two different possibilities 1 that the diapir plunges to the northwest or 2 that a focused high temperature heat flow existed along just the northwest margin of the diapir if the plunging diapir interpretation is correct then the thermally immature area south of the diapir was in a subsalt position and the high maturity area northwest of the diapir was in a suprasalt position prior to tertiary uplift and erosion if a presumed salt source at depth to the northwest of el gordo also fed el papalote diapir which is located just to the north of el gordo diapir then the tabular halokinetic sequences that are found only along the east side of el papalote may be subsalt features however if the diapir is subvertical and the high maturity values northwest of the diapir are caused by prolonged high temperature fluid flow along just the northwestern margin of the diapir then both of these scenarios are in disagreement with previously published numerical models this disagreement arises because the models predict that thermal anomalies will extend outward from a diapir a distance roughly 1 5 times the radius of the diapir but the results reported here show that the anomalous values on one side of the diapir are about two times the radius whereas they are as much as five times the radius on the other side of the diapir the results indicate that strata adjacent to salt margins may experience significantly different heat histories adjacent to different margins of diapirs that result in strikingly different diagenetic histories even at the same depth

geometry and kinematics of compressional growth structures and diapirs in the la popa basin of northeast mexico insights from sequential restoration of a regional cross section and three dimensional analysis 1 diapirism in the la popa basin ne mexico was triggered and sustained by compressional decollement tectonics coeval development of contractional structures and diapirs was recorded by growth strata of late cretaceous tertiary age a palinspastic reconstruction of a regional cross section based on the restoration of growth strata related to both diapirs and detachment folds was carried out on the basis of this reconstruction and field data a three dimensional geometrical study was done to quantify the movement of evaporites within the detachment horizon and two diapirs the latter allowed determining the tectonodiapiric potential of a structure or set of structures i e the amount of ductile rocks forced to flow in association with the growth of a tectonic structure which is not accommodated by thickening of the ductile horizon nor by the tectonic structure itself and is capable of producing diapiric phenomena this study demonstrates that there is a direct coupling between tectonodiapiric potential and diapiric activity geometrical results show that the main factors that controlled the amount of ductile material moved as a consequence of compressional tectonics were shortening the depth to detachment the folding style and the style of deformation process i e pure shear simple shear in response to folding the overburden experienced a downward movement that was the major cause of diapiric phenomena in addition to field and geometrical data mechanical data indicate that forceful intrusion was the prevailing emplacement mechanism temperatures 150 197 c and strain rates in the order of 10 16 10 17 s 1 calculated for top of the evaporite layer were adequate for the flow of these rocks from the initiation of compression onward however an inferred overpressure in the ductile layer should be considered the key factor for the emplacement mechanism

poseidon s horses plate tectonics and earthquake storms in the late bronze age aegean and eastern mediterranean abstract in light of the accumulated evidence now published the oft denigrated suggestion that major earthquakes took place in the aegean and eastern mediterranean areas during the late 13th and early 12th centuries bc must be reconsidered a new study of earthquakes occurring in the aegean and eastern mediterranean region during the 20th century utilizing data recorded since the invention of seismic tracking devices shows that this area is criss crossed with major fault lines and that numerous temblors of magnitude 6 5 enough to destroy modern buildings let alone those of antiquity occur frequently it can be demonstrated that such major earthquakes often occur in groups known as sequences or storms in which one large quake is followed days months or even years later by others elsewhere on the now weakened fault line when a map of the areas in the aegean and eastern mediterranean region affected i e shaken by 20th centuryad earthquakes of magnitude 6 5 and greater and with an intensity of vii or greater is overlaid on robert drews map of sites destroyed in these same regions during the so called catastrophe near the end of the late bronze age it is readily apparent that virtually all of these lba sites lie within the affected high shaking areas while the evidence is not conclusive based on these new data we would suggest that an earthquake storm may have occurred in the late bronze age aegean and eastern mediterranean during the years 1225 1175bc this storm may have interacted with the other forces at work in these areas c 1200bc and merits consideration by archaeologists and prehistorians

experimental constraints on reconstruction of archean seawater ni isotopic composition from banded iron formations abstract the ni isotopic systematics in banded iron formations bifs potentially recorded the ni isotopic composition of ancient seawater over precambrian geological history however the utility of bifs as proxies requires quantitative knowledge of how ni isotopes fractionated as dissolved ni was initially incorporated into iron rich sediments and how diagenesis may have affected the ni isotopic systematics here we report results of synthesis experiments to investigate the behavior of ni isotopes during ni coprecipitation with ferrihydrite and then transformation of ferrihydrite to hematite ferrihydrite coprecipitation experiments at neutral ph demonstrated that the dissolved ni was variably heavier than coprecipitated ni likely a mixture of surface adsorbed and structurally incorporated ni with the isotope fractionation becoming larger as the fraction of ni associated with solid increased 60 58nisolution solid 0 08 to 0 50 further experiments at lower ph 3 7 6 7 in which structurally incorporated ni likely dominated in solids documented a decrease in 60 58nisolution solid from 0 44 to 0 18 as the ph decreased the negative value for 60 58nisolution solid at low ph indicates the enrichment of heavier isotopes in incorporated ni relative to dissolved and adsorbed ni possibly as a result of the presence of a small amount of tetrahedral ni2 in addition to octahedral ni2 in the ferrihydrite structure the results of the ferrihydrite experiments thus reflect equilibrium isotope fractionation between three pools of ni with 60 58ni values in the order of incorporated dissolved adsorbed hematite was synthesized by transformation of ni bearing ferrihydrite in aqueous solution at 100 c a significant amount of ni up to 60 was released desorbed from solids into solutions as ph dropped from 7 to 4 5 5 5 upon phase transformation rinsing of the synthesized hematite in 2 m acetic acid released only very small amounts of ni o octahedra in the hematite structure with weaker ni o bond strengths on average hence the more variable 60 58nisolution solid values 0 04 to 0 77 observed in hematite experiments most likely reflect thermodynamically driven rayleigh fractionation with incorporated ni unavailable to exchange with dissolved ni due to continuous reduction in size of the highly reactive surface pool of ni through which all solid solution exchange must occur overall the synthesized hematite was isotopically lighter than the ferrihydrite by 0 08 in 60 58ni which is however within the current analytical uncertainties 0 09 this implies that earliest diagenesis of bifs results in very limited change in the isotopic composition of solid associated ni our experimental results although conducted in a very simple system that differs from archean seawater represent an important step toward reconstruction of the ni isotopic composition of ancient seawater from ni isotopic signatures in bifs

internal kinematics of salt diapirs the internal structure of intrusive and extrusive salt bodies elucidates their external shape and the mechanism and history of diapiric emplacement information relevant to petroleum exploration trace amounts of brine can act like heat to weaken salt and promote geologic creep by solution transfer mechanisms we compare natural strain markers in salt with the artificial markers used by fluid dynamicists stream lines are the smooth flow paths followed by fluid particles stream surfaces separate flow laminae and contain the stream lines grain shape fabrics in salt anneal readily and have strain memories so short that lineations map the stream lines and foliations map the stream surfaces of the last stages of deformation by contrast larger structures like folded beddi g have much longer strain memories as a result multiple generations of tonguelike recumbent flow folds formed by unsteady flow in the mother source layer rotate to upright sheath folds or spines in the stems of diapirs here they are constricted and refolded into steep curtain folds to form crescentic and other interference patterns visible in the roofs of salt mines mature diapirs can form crestal bulbs which may be balloon or mushroom shaped and which potentially form larger petroleum traps than previously supposed screens of country rock may be entrained between the stem and peripheral overhanging lobes caused by episodic sedimentation

nickel and its isotopes in organic rich sediments implications for oceanic budgets and a potential record of ancient seawater abstract nickel ni is a biologically active element that displays a nutrient like depth distribution in the modern oceans recent studies of ni isotopes have highlighted the fact that in common with many other transition metals the ni stable isotope composition expressed as 60 ni of the dissolved phase is heavier than the inputs at 1 3 to 1 7 the sedimentary outputs that control the high 60 ni of the ocean coupled with records for past seawater could potentially yield new information on the past earth system but these are currently not well understood here we present the first ni abundance and isotope data for a key output that associated with ni uptake into organic matter at productive upwelling regions and elsewhere we investigate the distribution of ni and its isotopes in two fractions separated from the bulk sediment an hf digestible fraction extracted with hf hcl and an organic sulphide rich fraction the organic sulphide fractions exhibit a range in 60 ni from 0 86 to 1 83 systematic relationships between ni concentrations total organic carbon and ni isotopes suggest that the organic sulphide fraction originates in the photic zone and is delivered to the sediment as a closed system despite the possibility of transfer of ni to sulphide within it authigenic ni in the bulk sediment is dominated by the hf digestible fraction which in ni enriched sediments where the detrital correction is small is very close to the modern deep ocean at 60 ni 1 2 these data suggest that organic rich sediments beneath upwelling zones while they are an important output flux of ni from the oceans do not solve the isotope balance problem because their 60 ni is almost identical to modern seawater on the other hand the approach adopted here involving the analysis of the two fractions both traces the fractionation imparted by biological uptake as well as recording the 60 ni of contemporary seawater suggesting potential for understanding the past oceans

recent behavior of the north anatolian fault insights from an integrated paleoseismological data set 1 the north anatolian fault naf is a right lateral plate boundary fault that arcs across northern turkey for 1500 km almost the entire fault progressively ruptured in the 20th century its cascading style indicating that stress from one fault rupture triggers fault rupture of adjacent segments using published paleoseismic investigations this study integrates all of the existing information about the timing of paleoearthquakes on the naf paleoseismic investigation data are compiled into a database and for each site a bayesian ordering constrained age model is constructed in a consistent framework spatial variability of recurrence intervals suggests a spatial pattern in the behavior of earthquakes on the naf that may correspond to the tectonic provinces within the anatolian plate in the west the shear stress associated with the escaping anatolian plate interplays with the tensile stress associated with the aegean extensional province along this western transtensional section we recognize short recurrence intervals and switching between the furcated fault strands the central section of the naf is translational with little influence of fault normal stresses from other tectonic sources this section tends to rupture in unison or close succession the eastern section of the naf is transpressional due to the compressional fault normal stress associated with the indenting arabian plate along this section the recurrence intervals are bimodal which we attribute to variable normal stress although there are other possible causes

60 myr records of major elements and pb nd isotopes from hydrogenous ferromanganese crusts reconstruction of seawater paleochemistry we compare the time series of major element geochemical and pb and nd isotopic composition obtained for seven hydrogenous ferromanganese crusts from the atlantic indian and pacific oceans which cover the last 60 myr average crust growth rates and age depth relationships were determined directly for the last about 10 myr using be 10 be 9 profiles in the absence of other information these were extrapolated to the base of the crusts assuming constant growth rates and constant initial be 10 be 9 ratios due to the lack of additional information co contents have also been used previously to estimate growth rates in co rich pacific and atlantic seamount crusts puteanus and halbach 1988 a comparison of be 10 be 9 and co based dating of three co rich crusts supports the validity of this approach and confirms the earlier chronologies derived from extrapolated be 10 be 9 based growth rates back to 60 ma our data show that the flux of co into co poor crusts has been considerably lower the relationship between growth rate and co content for the co poor crusts developed from these data is in good agreement with a previous study of a wider range of marine deposits manheim 1986 the results suggest that the co content provides detailed information on the growth history of ferromanganese crusts particularly prior to 10 12 ma where the be 10 based method is not applicable the distributions of pb and nd isotopes in the deep oceans over the last 60 myr are expected to be controlled by two main factors a variations of oceanic mixing patterns and flow paths of water masses with distinct isotopic signatures related to major paleogeographic changes and b variability of supply rates or provenance of detrital material delivered to the ocean linked to climate change glaciations or major tectonic uplift the major element profiles of crusts in this study show neither systematic features which are common to crusts with similar isotope records nor do they generally show coherent relationships to the isotope records within a single crust consequently any interpretation of time series of major element concentrations of a single crust in terms of paleoceanograghic variations must be considered with caution this is because local processes appear to have dominated over more basin wide paleoceanographic effects in this study co is the only element which shows a relationship to pb and nd isotopes in pacific crusts a possible link to changes of pacific deep water properties associated with an enhanced northward advection of antarctic bottom water from about 14 ma is consistent with the pb but not with the nd isotopic results the self consistent profiles of the pb and nd isotopes suggest that postdepositional diagenetic processes in hydrogenous crusts including phosphatization events have been insignificant for particle reactive elements such as pb be and nd isotope time series of pb and nd show no systematic relationships with major element contents of the crusts which supports their use as tracers of paleo seawater isotopic composition

late holocene slip rate for the north anatolian fault turkey from cosmogenic 36cl geochronology implications for the constancy of fault loading and strain release rates geomorphologic mapping and cosmogenic radionuclide 36cl dating of an offset fluvial terrace yield a preferred late holocene slip rate of 20 5 5 5 mm yr for the central part of the north anatolian fault turkey an independent slip rate constrained by 14c ages is 20 5 8 5 mm yr these rates are generally similar to but possibly slightly slower than the short term rate of elastic strain storage of 25 1 measured geodetically across this major strike slip fault reilinger et al 2006 1 suggesting that loading and strain release on this part of the north anatolian fault have been relatively constant when averaged over the past 2 2 5 k y we attribute this consistency to the relatively simple structure of the anatolia eurasia plate boundary in north central turkey where almost all plate boundary strain is accommodated along the north anatolian fault the absence of other moderate to high slip rate faults and the earthquakes they produce leads to a relatively simple stress evolution for the fault dominated by steady tectonic loading 1 ref 10

paleoseismic evidence of characteristic slip on the western segment of the north anatolian fault turkey we have conducted a paleoseismic investigation of serial fault rupture at one site along the 110 km rupture of the north anatolian fault that produced the mw 7 4 earthquake of 17 august 1999 the benefit of using a recent rupture to compare serial ruptures lies in the fact that the location magnitude and slip vector of the most recent event are all very well documented we wished to determine whether or not the previous few ruptures of the fault were similar to the recent one we chose a site at a step over between two major strike slip traces where the principal fault is a normal fault our two excavations across the 1999 rupture reveal fluvial sands and gravels with two colluvial wedges related to previous earthquakes each wedge is about 0 8 m thick considering the processes of collapse and subsequent diffusion that are responsible for the formation of a colluvial wedge we suggest that the two paleoscarps were similar in height to the 1999 scarp this similarity supports the concept of characteristic slip at least for this location along the fault accelerator mass spectrometry ams radiocarbon dates of 16 charcoal samples are consistent with the interpretation that these two paleoscarps formed during large historical events in 1509 and 1719 if this is correct the most recent three ruptures at the site have occurred at 210 and 280 year intervals

growth of a pleistocene giant carbonate vein and nearby thermogene travertine deposits at semproniano southern tuscany italy estimate of co2 leakage abstract a giant carbonate vein 50 m thick fissure ridge travertines and nearby travertine plateaus in the semproniano area mt amiata geothermal field southern tuscany italy are investigated through a multidisciplinary approach including field and laboratory geochemical analyses u th geochronology c nd o and sr isotope systematics ree abundances and fluid inclusion microthermometry the main aim of this work is to understand 1 modes and rates for the growth of the giant vein and nearby travertine deposits within a quaternary volcano tectonic domain 2 implications in terms of the co 2 leakage and 3 possible relationships with quaternary paleoclimate and hydrological oscillations results show that the giant vein was the inner portion of a large fissure ridge travertine and grew asymmetrically and ataxially through repeated shallow fluid injections between 650 and 85 ka with growth rates in the 10 2 10 3 mm a order the giant vein developed mainly during warm humid interglacial periods partially overlapping with the growth of nearby travertine plateaus estimated values of co 2 leakage connected with the vein precipitation are between about 5 10 6 and 3 10 7 mol a 1 km 2 approximately representing one millionth of the present global co 2 leakage from volcanic areas temperature estimates obtained from o isotopes and fluid inclusion microthermometry indicate epithermal conditions 90 50 c for the circulating fluid during the giant vein growth with only slight evidence of cooling with time geochemical and isotope data document that the travertine deposits formed mainly during pleistocene warm humid periods within a tectonically controlled convective fluid circuit fed by meteoric infiltration and maintained by the regional geothermal anomaly hosted by the carbonate reservoir of the mt amiata field

hafnium isotope stratigraphy of ferromanganese crusts a cenozoic record of hafnium isotopic compositions of central pacific deep water has been obtained from two ferromanganese crusts the crusts are separated by more than 3000 kilometers but display similar secular variations significant fluctuations in hafnium isotopic composition occurred in the eocene and oligocene possibly related to direct advection from the indian and atlantic oceans hafnium isotopic compositions have remained approximately uniform for the past 20 million years probably reflecting increased isolation of the central pacific the mechanisms responsible for the increase in87sr 86sr in seawater through the cenozoic apparently had no effect on central pacific deep water hafnium

determination of molybdenum isotope fractionation by double spike multicollector inductively coupled plasma mass spectrometry 1 molybdenum isotopic compositions are precisely determined by mc icp ms measurements using a mo double spike the double spike is added prior to chemical purification so that laboratory and instrumental mass fractionations are separated from natural mass dependent fractionation fractionation is determined on four mo mass ratios providing an internal consistency check the external standard reproducibility is at 0 06 per mil on the 98mo 95mo ratio 2 standard deviation using a normal microconcentric nebuliser with a cyclonic spray chamber the minimum quantity of mo is 1 g for high precision results a hydrothermal molybdenite shows fractionation of 0 3 per mil on the 98mo 95mo ratio relative to our standard johnson matthey 1000 g ml 0 3 icp standard solution lot 602332b fine grained sediments show fractionation of 0 1 and 0 3 per mil on the 98mo 95mo ratio the observed mo isotope fractionation is small but resolvable with the presented high resolution technique

provenance of upper cretaceous paleogene sandstones in the foreland basin system of the sierra madre oriental northeastern mexico and its bearing on fluvial dispersal systems of the mexican laramide province sandstone petrography and detrital zircon u pb analysis of upper cretaceous paleogene sandstones in the foreland basin of the sierra madre oriental in northeastern mexico indicate long distance sediment transport from arc basement and thrust belt sources lying to the west northwest and south the basin fill termed the difunta group consists of sublitharenites litharenites feldspathic litharenites and lithic arkoses derived from mixed sources that included sedimentary rocks magmatic arc rocks and subordinate basement rocks six age populations comprise the detrital zircon content of the sandstones proterozoic 1900 900 ma early paleozoic 500 400 ma late paleozoic early triassic 288 235 ma jurassic 180 151 ma early cretaceous 150 111 ma and late cretaceous paleogene 110 54 ma these grains were derived from several arc terranes ranging in age from permian to paleogene in western mexico and the southwestern united states from sedimentary rocks and possibly interbedded tuffs of the sierra madre oriental orogen and from basement sources or their derivative sandstones of the southwestern united states the petrographic and geochronologic provenance data corroborate existing models for derivation of much foreland detritus from arc sources to the west identify the sierra madre orogen itself as an important source for sediment and these data modify the late cretaceous paleogene paleogeography of mexico to include a long orogen parallel fluvial system with headwaters in the southwestern united states the difference in average ages of the youngest grains in the sandstones and their inferred depositional ages is 10 5 m y indicating that the initial coarse fill of the foreland basin was derived from early laramide uplift and eastward arc migration in northwestern mexico and the southwestern united states

nickel isotopic compositions of ferromanganese crusts and the constancy of deep ocean inputs and continental weathering effects over the cenozoic the global variability in nickel ni isotope compositions in ferromanganese crusts is investigated by analysing surface samples of 24 crusts from various ocean basins by mc icpms using a double spike for mass bias correction ferromanganese crusts have view the mathml source isotopic compositions that are significantly heavier than any other samples thus far reported 0 1 to 0 3 with surface scrapings ranging between 0 9 and 2 5 relative to nist srm986 there is no well resolved difference between ocean basins although the data indicate somewhat lighter values in the atlantic than in the pacific nor is there any evidence that the variations are related to biological fractionation presence of different water masses or bottom water redox conditions preliminary data for laterite samples demonstrate that weathering is accompanied by isotopic fractionation of ni which should lead to rivers and seawater being isotopically heavy this is consistent with the slightly heavier than average isotopic compositions recorded in crusts that are sampled close to continental regions furthermore the isotopic compositions of crusts growing close to a hydrothermal source are clustered around 1 5 suggesting that hydrothermal fluids entering the ocean may have a ni isotopic composition similar to this value based on these data the heavy ni isotopic compositions of ferromanganese crusts are likely due to input of isotopically heavy ni to the ocean from continental weathering and possibly also from hydrothermal fluids a depth profile through one crust cd29 2 from the north central pacific ocean displays large variations in ni isotope composition 1 1 2 3 through the last 76 myr although there may have been some redistribution of ni associated with phosphatisation there is no systematic difference in ni isotopic composition between deeper older parts and shallower younger parts of the crust which may suggest that oceanic sources and sinks of ni have largely remained in steady state over the cenozoic additionally the isotope profile is in agreement with a profile of mn concentration through the same crust this implies a link between the ni isotopic composition recorded in ferromanganese crusts and the release of ni into the ocean through hydrothermal activity this supports the conclusions drawn from surface data that ni isotope ratios in ferromanganese crusts are largely controlled by the isotopic compositions of the ni oceanic input sources

nickel isotope fractionation during tropical weathering of ultramafic rocks abstract although ni isotopes have been shown to be significantly fractionated in terrestrial samples their use in continental environmental studies has not yet been evaluated the present study focuses on an ultramafic um massif barro alto goias brazil because such areas are naturally rich in ni we present developed lateritic weathering profiles the goal of the study is to evaluate the potential of using ni isotopes in environmental continental studies by combining its isotopic signature with mineralogy in order to better understand the geochemical cycling of ni in um settings during weathering as such ni isotope values were measured in samples from the barro alto um complex in the main stages of the lateritic weathering profile of um rocks including bedrock ores saprolitic and lateritic samples and soil the mineralogical composition of the samples with a focus on the different ni bearing minerals was also determined to decipher the potential links between isotopic fractionation and weathering dynamics isotopic signatures 60 ni from the natural ni geochemical cycle include bedrock samples 60 ni 0 28 0 08 ore samples saprolitic and lateritic 60 ni from 0 60 to 0 30 and soil samples 60 ni from 0 19 to 0 02 an overall trend of heavier isotope depletion was observed in the solid phase during weathering 60 ni soil bedrock 0 47 the mineralogical results were consistent with the literature and showed that the mineralogy of the lateritic part and soil was dominated by fe oxides whereas clay minerals were the primary ni phase scavengers in the saprolitic part of the profile thus the formation of ni bearing clay minerals and fe oxides appeared to lead to depletion in heavier isotopes which indicates preferential export of heavy isotopes in the dissolved phase this result is consistent with isotopic signatures measured in the exchangeable pool of the solid phase 60 ni exch total up to 0 47 and ni isotopes appear to be a promising tracer to better understand the biogeochemical ni cycling on the earth s surface

lithium and its isotopes in major world rivers implications for weathering and the oceanic budget abstract the outstanding problem in the lithium geochemical cycle is the lack of an isotopic mass balance in the ocean the 6li compositions of fresh basalts 4 the hydrothermal fluids derived from them average 9 and seawater significantly heavier at 32 are well understood but only very sparse river input data are available for li mass balance calculations in an attempt to rectify the situation we have measured the lithium concentrations and isotopic compositions of major world rivers draining representative geological terrains this helps both to constrain the river endmember and to understand the behavior of lithium isotopes in the continental weathering environment fluvial isotopic compositions display a very large range 6 0 to 32 2 there is no definitive relationship between 6li and lithology but in general rivers draining marine evaporites are 20 to 22 carbonates 26 to 32 black shales 26 shields 6 6 to 19 and mixed siliceous terrains 6 to 28 the flow weighted mean concentration of the measured rivers is 215 nm at 23 this updated riverine 6li value responsible for 30 of the global riverine discharge does not solve the isotopic imbalance if the measured li concentrations and isotopic compositions are representative of all rivers the presence of a yet unidentified sink with a higher fractionation factor 1 023 than determined for low temperature basalt alteration 1 019 is required for an isotopic steady state of li in the ocean authigenic clays are a possible candidate as clays are known to be enriched in both lithium and in the light isotope preferentially alternatively the hydrothermal flux must be much less than half of that estimated by the 3he inventory and the oceanic budgets for 87sr 86sr and mg the relationship of 6li to the major ions and 87sr 86sr suggests that the important processes affecting river dissolved lithium isotopic compositions are fractionation between solution and secondary minerals and thus the intensity of weathering

black smokers massive sulphides and vent biota at the mid atlantic ridge the discovery of black smokers massive sulphides and vent biota in the rift valley of the mid atlantic ridge demonstrates that this assemblage of hydrothermal phenomena is not limited to intermediate to fast spreading oceanic ridges hydrothermal exchange processes may thus be important at the ridges which extend through the atlantic ocean and western indian ocean comprising more than half of the 55 000 km global length of seafloor spreading centres

weathering and vegetation controls on nickel isotope fractionation in surface ultramafic environments albania abstract the dissolved nickel ni isotopic composition of rivers and oceans presents an apparent paradox even though rivers represent a major source of ni in the oceans seawater is more enriched in the heavier isotopes than river water additional sources or processes must therefore be invoked to account for the isotopic budget of dissolved ni in seawater weathering of continental rocks is thought to play a major role in determining the magnitude and sign of isotopic fractionation of metals between a rock and the dissolved product we present a study of ni isotopes in the rock soil plant systems of several ultramafic environments the results reveal key insights into the magnitude and the control of isotopic fractionation during the weathering of continental ultramafic rocks this study introduces new constraints on the influence of vegetation during the weathering process which should be taken into account in interpretations of the variability of ni isotopes in rivers the study area is located in a temperate climate zone within the ophiolitic belt area of albania the serpentinized peridotites sampled present a narrow range of heavy ni isotopic compositions ni 60 0 25 0 16 2sd n 2 at two locations horizons within two soil profiles affected by different degrees of weathering all presented light isotopic compositions compared to the parent rock 60nisoil rock up to 0 63 this suggests that the soil pool takes up the light isotopes while the heavier isotopes remain in the dissolved phase by combining elemental and mineralogical analyses with the isotope compositions determined for the soils the extent of fractionation was found to be controlled by the secondary minerals formed in the soil the types of vegetation growing on ultramafic derived soils are highly adapted and include both ni hyperaccumulating species which can accumulate several percent per weight of ni and non accumulating species whole plant isotopic compositions were found to be isotopically heavier than the soil 60niwhole plant soil up to 0 40 fractions of ni extracted by dtpa diethylenetriaminepentaacetic acid presented isotopically heavy compositions compared to the soil 60nidtpa soil up to 0 89 supporting the hypothesis that the dissolved ni fraction controlled by weathering has a heavy isotope signature the non hyperaccumulators n 2 were inclined to take up and translocate light ni isotopes with a large degree of fractionation 60nileaves roots up to 0 60 for ni hyperaccumulators n 7 significant isotopic fractionation was observed in the plants in their early growth stages while no fractionation occurred during later growth stages when plants are fully loaded with ni this suggests that i the high efficiency translocation process involved in hyperaccumulators does not fractionate ni isotopes and ii the root uptake process mainly controls the isotopic composition of the plant in ultramafic contexts vegetation composed of hyperaccumulators can significantly influence isotopic compositions through its remobilization in the upper soil horizon thereby influencing the isotopic balance of ni exported to rivers

evolution of nd and pb isotopes in central pacific seawater from ferromanganese crusts abstract hydrogenetic ferromanganese crusts incorporate elements from ambient seawater during their growth on seamounts by analysing nd pb and be isotope profiles within crusts it is possible to reconstruct seawater tracer histories depth profiles of 10be 9be ratios in three pacific ferromanganese crusts have been used to obtain growth rates which are between 1 4 and 3 8 mm ma nd and pb isotopes provide intact records of isotopic variations in pacific seawater over the last 20 ma or more there were only small changes in pb isotope composition in the last 20 ma this indicates a constant pb composition for the erosional sources and suggests further that erosional nd inputs may have been uniform too end values vary considerably with time and most probably reflect changes in ocean circulation the end values of the crusts not only vary as a function of age but also as a function of water depth from 25 to 0 ma crust va13 2 from 4 8 km water depth has a similar pattern of end variation to the two shallower crusts from 1 8 and 2 3 km but about 1 0 to 1 5 units more negative this suggests that end stratification in pacific seawater as demonstrated for the present day has been maintained for at least 20 ma each crust shows a decrease in end from 3 5 ma to the present which is interpreted in terms of an increase in the nadw component present in the pacific from 10 to 3 5 ma ago the crusts show an increase in end this suggests a decreasing role for a deep water source with end less than circum pacific sources in this regard the panamanian gateway restriction from 10 ma with final closure at 3 5 ma may have played an important role in reducing access of atlantic derived nd to the pacific

geometry and kinematics of the nuncios detachment fold complex implications for lithotectonics in northeastern mexico 1 using recent geologic mapping combined with digital elevation data aerial photo interpretation and cross section balancing we describe the three dimensional 3 d geometry and kinematics of the nuncios fold complex in the monterrey salient of northeastern mexico this map scale evaporite cored detachment fold structure involves upper jurassic through cretaceous rocks deformed during the laramide orogeny and comprises two westward plunging anticlines and an intervening eastward plunging syncline seven balanced cross sections and a 3 d model of this north vergent structure document substantial along strike variations in both fold geometry and detachment depth suggesting that 3 d flow of the detachment layer may have occurred during folding comparison of folds in the monterrey salient with those in the neighboring parras basin suggests that the latter south vergent folds root to a shallower detachment we suggest that northward transport of the monterrey salient folds on the lower evaporite detachment may have been inhibited by a thick sequence of foreland basin rocks in the northeastern parras and southern la popa basins and that the smaller south verging folds formed where the lower detachment was abandoned and slip was transferred to the shallower detachment forming a triangle zone at the front of the sierra madre orogenic wedge

travitonics using travertines in active fault studies abstract late quaternary travertines deposited from hot springs can reveal much about the neotectonic attributes and histories of structures on the basis of field studies in the aegean region turkey and greece the northern apennines italy and the basin and range province usa we conclude that the following relationships are of predictive value i travertine deposits are preferentially located along fracture traces either immediately above extensional fissures or in the hanging walls of normal faults ii the locations of many travertine fissure ridge deposits coincide with step over zones relay ramps between fault segments networks of intersecting tensional fissures reflecting the complex strains experienced in such settings are probably responsible for enhancing hydrothermal flow iii the morphology of travertine deposits overlying extensional fissures is controlled by the rheology of the underlying materials tufa cones towers pinnacles form on former and present lake floors where fissures underlie unconsolidated sediments whereas fissure ridges develop where fissures cut bedrocks at the surface iv fissure ridges comprise outwardly dipping bedded travertine flanking a central tensional fissure filled by vertically banded travertines fissures can be used to infer local stretching directions v where there are travertines datable by the u series method it is possible to calculate time averaged dilation and lateral propagation rates for individual fissures vi most fissures cutting fissure ridges comprise self similar angular segments with fractal dimensions in the range 1 00 1 12 the properties of bedded travertine combined with stress perturbations at fissure tips probably being responsible for such similar fractal dimensions being inferred from such a wide range of locations fissures gradually increasing in width with depth are products of continuous fracture dilation in contrast to those that form during episodic dilation which display stepped increases of width with depth vii travertine deposited from springs along fault zones accumulate in terraced mounds sited down slope of the spring line viii many post depositional fractures cutting travertine deposits are locally oriented at right angles to deposit margins and ix systematic joints in travertines are restricted to those parts of eroded sheet deposits that have been exhumed

fracture controlled paleohydrology in a map scale detachment fold insights from the analysis of fluid inclusions in calcite and quartz veins abstract this study uses fluid inclusions in quartz and calcite veins to characterize the fracture controlled paleohydrology of a map scale evaporite cored detachment fold in the sierra madre oriental of northeastern mexico field observations indicate that the veins are tectonic in origin and that they formed in a general sequence that corresponds to four broad stages of progressive folding we collected samples from each vein stage in various structural and stratigraphic positions across the fold after determining the mineral paragenesis and origin of inclusions in each sample we used standard microthermometric techniques to measure the homogenization temperatures t h salinities and eutectic temperatures of the available two and three phase aqueous inclusions neither t h salinity nor eutectic temperature varied systematically with inclusion origin or mineral type the data are also not significantly correlated with structural position or vein type but are strongly partitioned by stratigraphy suggesting that the area was a vertically stratified hydrologic system consisting of three regional paleohydrostratigraphic units an upper unit comprised the indidura formation through difunta group and is characterized by t h near 150 c and salinity t h near 150 c and salinities near 12 or 22 wt nacl equivalent the lower unit comprised the zuloaga and la casita formations and is characterized by an average t h near 225 c and salinities in three groups near 12 22 or 36 wt nacl equivalent the preservation of multiple distinct fluid types in many veins suggests that fracture development during folding and uplift created a second paleohydrologic system that overprinted the vertically stratified system fracture controlled fluid migration in this second system occurred in periodic repeated and spatially variable pulses

characterising the nickel isotopic composition of organic rich marine sediments new ni stable isotope data 60ni determined by double spike mc icp ms for two geologically distinct suites of organic rich marine sediments from the sinemurian pliensbachian s p global stratotype section and point gssp robin hood s bay uk and the devonian mississippian exshaw formation west canada sedimentary basin is presented herein these sediments yield 60ni values of between 0 2 and 2 5 and predominantly have ni isotopic compositions that are heavier than those of abiotic terrestrial and extraterrestrial samples 0 15 and 0 27 and in some cases present day seawater 1 44 and dissolved ni from riverine input 0 80 in addition the observed degree of isotopic fractionation in the marine sediments is far greater than that of these other sample matrices however a strong similarity is exhibited between the 60ni values of the organic rich sediments studied here and those of ferromanganese crusts 0 9 2 5 suggesting that factors ubiquitous to the marine environment are likely to play a key role in the heightened level of isotopic fractionation in these sample matrices a lack of correlation between the ni stable isotope compositions of the organic rich sediments and ni abundance suggests that isotopic fractionation in these sediments is not controlled by incorporation or enrichment of ni during sediment accumulation further no relationship is observed between 60ni and toc concentrations or bottom water redox conditions indicating that the organic carbon reservoir and levels of oxygenation at the sediment water interface do not exert a primary control on ni isotope fractionation in marine sediments following examination of these relationships it is therefore more likely that the heavy ni isotope compositions of marine sediments are controlled by the weathering environment and the dominant sources of dissolved ni into the global ocean reservoir

cenozoic marine geochemistry of thallium deduced from isotopic studies of ferromanganese crusts and pelagic sediments cenozoic records of tl isotope compositions recorded by ferromanganese fe mn crusts have been obtained such records are of interest because recent growth surfaces of fe mn crusts display a nearly constant tl isotope fractionation relative to seawater the time series data are complemented by results for bulk samples and leachates of various marine sediments oxic pelagic sediments and anoxic marine deposits can be distinguished by their tl isotope compositions both pelagic clays and biogenic oozes are typically characterized by 205tl greater than 2 5 whereas anoxic sediments have 205tl of less than 1 5 205tl is the deviation of the 205tl 203tl isotope ratio of a sample from nist srm 997 tl in parts per 104 leaching experiments indicate that the high 205tl values of oxic sediments probably reflect authigenic fe mn oxyhydroxides time resolved tl isotope compositions were obtained from six fe mn crusts from the atlantic indian and pacific oceans and a number of observations indicate that these records were not biased by diagenetic alteration over the last 25 myr the data do not show isotopic variations that significantly exceed the range of tl isotope compositions observed for surface layers of fe mn crusts distributed globally 205tl 12 8 1 2 this indicates that variations in deep ocean temperature were not recorded by tl isotopes the results most likely reflect a constant tl isotope composition for seawater the growth layers of three fe mn crusts that are older than 25 ma show a systematic increase of 205tl with decreasing age from about 6 at 60 50 ma to about 12 at 25 ma these trends are thought to be due to variations in the tl isotope composition of seawater which requires that the oceans of the early cenozoic either had smaller output fluxes or received larger input fluxes of tl with low 205tl larger inputs of isotopically light tl may have been supplied by benthic fluxes from reducing sediments rivers and or volcanic emanations alternatively the tl isotope trends may reflect the increasing importance of tl fluxes to altered ocean crust through time

nickel isotope fractionation during laterite ni ore smelting and refining implications for tracing the sources of ni in smelter affected soils abstract nickel isotope ratios were measured in ores fly ash slags and feni samples from two metallurgical plants located in the goias state brazil barro alto niquel ndia this allowed investigating the mass dependent fractionation of ni isotopes during the ni laterite ore smelting and refining feeding material exhibits a large range of 60 ni values from 0 02 0 10 to 0 20 0 05 n 7 explained by the diversity of ni bearing phases and the average of 60 ni feeding materials was found equal to 0 08 0 08 2sd n 7 both 60 ni values of fly ash 60 ni 0 07 0 07 n 10 and final feni produced 0 05 0 02 n 2 were not significantly different from the feeding materials ones these values are consistent with the very high production yield of the factories however smelting slags present the heaviest 60 ni values of all the smelter samples with 60 ni ranging from 0 11 0 05 to 0 27 0 05 n 8 soils were also collected near and far from the niquel ndia metallurgical plant to evaluate the potential of ni isotopes for tracing the natural vs anthropogenic ni in soils the ni isotopic composition of the non impacted topsoils developed on ultramafic rocks ranges from 0 26 0 09 to 0 04 0 05 n 20 on the contrary the ni isotopic composition of the non ultramafic topsoils collected close to the plant exhibit a large variation of 60 ni ranging from 0 19 0 13 up to 0 10 0 05 n 4 this slight but significant enrichment in heavy isotopes highlights the potential impact of smelting activity in the surrounding area as well as the potential of ni isotopes for discerning anthropogenic samples heavier 60 ni values from natural ones lighter 60 ni values however given the global range of published 60 ni values from 1 03 to 2 5 and more particularly those associated to natural weathering of ultramafic rocks from 0 61 to 0 32 the use of ni isotopes for tracing environmental contamination from smelters will remain challenging

comparative geochemistry of four ferromanganese crusts from the pacific ocean and significance for the use of ni isotopes as paleoceanographic tracers abstract ferromanganese fe mn crusts are potential archive of the ni isotope composition of seawater through time in this study we aim at 1 understanding ni isotope fractionation mechanisms and metal enrichment processes in fe mn deposits 2 addressing global vs local control of ni isotope composition of these deposits two fe mn crusts from the north pacific ocean apuupuu seamount hawaii and two fe mn crusts from the south pacific ocean near rurutu island austral archipelago of french polynesia were characterized for their elemental geochemistry and ni isotope composition geochemical analyses were performed at millimeter intervals in order to provide time resolved record of ni isotopes chronology and growth rates were determined using cosmogenic 10be isotope abundances the results show that despite different growth rates textures and geochemical patterns fe mn crusts from both north and south pacific oceans have fairly homogenous ni isotope compositions over the last 17 ma yielding average 60 58ni values of 1 79 0 21 2sd n 31 and 1 73 0 21 2sd n 21 respectively in one crust sample however layers directly in contact with the altered substrate show anomalously light 60 58ni values down to 0 25 0 05 2se together with rejuvenated 10be 9be ratios correlating with elevated ni mn ratios such patterns are best explained by protracted fluid rock interactions leading to alteration of mn phases after crust formation isotopically light ni would be the result of ni isotope fractionation during adsorption rather than the contribution of external ni sources e g hydrothermal sources having light ni isotope compositions the combination of our results with previously published data on fe mn crusts indicates that the average ni isotope composition in deep waters has not changed through the cenozoic 70 ma we propose that ni isotope variations in fe mn crusts may not only record variations of ni sources to the oceans but also post depositional processes depending on the growth history and geological settings of fe mn crusts

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

cadmium isotope fractionation in seawater a signature of biological activity investigations of cadmium isotope variations in the oceans may provide new insights into the factors that control the marine distribution and cycling of this element here we present the results of cd isotope and concentration analyses for 22 seawater samples from the atlantic southern pacific and arctic oceans the results reveal for the first time large and well resolved cd isotope fractionations in the marine environment the majority of the seawater samples display an inverse relationship between dissolved cd contents and isotope compositions which range from e114 110cd 3 0 5 for cd rich waters 0 8 1 0 nmol kg to e114 110cd 38 6 for surface water with a cd concentration of only 0 003 nmol kg all e114 110cd data are reported relative to the jmc cd munster standard this suggests that the cd isotope variations reflect kinetic isotope effects that are generated during closed system uptake of dissolved seawater cd by phytoplankton a few samples do not follow this trend as they exhibit extremely low cd contents 0 008 nmol kg and nearly un fractionated cd isotope compositions such complexities which are not revealed by concentration data alone require that the cd distribution at the respective sites was affected by additional processes such as water mass mixing atmospheric inputs of cd and or adsorption uniform isotope compositions of e114 110cd 3 3 0 5 1 s d were determined for seawater from 900 m depth despite of cd concentrations that display the expected increase along the global deep water pathway from the atlantic 0 3 nmol kg to the pacific ocean 0 9 nmol kg this indicates that the biomass which is remineralized in the deeper ocean is also characterized by a very constant cd isotope composition this observation is in accord with the interpretation that the cd distribution in surface waters is primarily governed by rayleigh fractionation during near quantitative uptake of dissolved seawater cd

tectonic evolution of the niksar and tasova erbaa pull apart basins north anatolian fault zone their significance for the motion of the anatolian block abstract the tasova erbaa and niksar basins are two adjacent pull apart basins along the north anatolian fault zone nafz within the tasova erbaa basin sedimentary lithofacies of the upper pontus formation plio pleistocene are asymmetrically distributed with laterally derived alluvial fans coarse braid plain deposits and axial braided stream deposits dominating the northern and western parts of the basin the basin has gently dipping sediments locally affected by pervasive extensional t faulting isolated compressional structures are associated with master faults deformation zone width 500 m pervasive extensional faults t and r and late stage pdz parallel compressional faults are also present an additional set of extensional faults trends perpendicular to the pdz accommodating secondary pull apart stretching within the basin the distribution of sedimentary facies and structural styles is consistent with that predicted by models for pull apart basins the adjacent niksar basin is an active pull apart basin possibly as young as 0 5 1 ma its modern drainage and sedimentary facies are symmetrically arranged adding the lengths of the tasova erbaa and niksar basin suggests 80 km total displacement along the north anatolian fault which is consistent with seymen itu ph d thesis 1975 sengor j geol soc 136 1979 269 282 and armijo et al tectonophysics 243 1999 135 154 who observed about 85 5 km total displacement along the north anatolian fault the change in course of the north anatolian fault marked by the formation of the niksar ezinepazari segment and this new geometry suggest that the anatolian block is rotating anticlockwise by having two separate poles one located near damascus and the other occurring north of the sinai peninsula this change may also mark the transfer of the anatolian triple junction from erzincan to karliova about 1 ma ago furthermore it appears that while the fault shortcuts the older basin a new generation of pull apart basins is formed due to changes of boundary conditions along the fault zone

are u th dates correlated with historical records of earthquakes constraints from coseismic carbonate veins within the north anatolian fault zone u th dating of carbonate veins in connection with active tectonics has recently been used as an attractive tool for constraining the absolute timing of late quaternary crustal deformations in this study for the first time we correlate u th ages of travertine deposits in coseismic fissures along the north anatolian fault zone with records of paleoseismological studies supported by historical earthquake catalogued data u th ages are assessed in relation to the recurrence interval and the size and epicenter distance of major holocene earthquakes our statistical evaluations on age correlations indicate that the carbonate vein precipitation is concentrated in eight different periods along the north anatolian fault zone the periods are well correlated with historical earthquake records and with previous dating results of the nearby trench studies at least six of the periods correspond to the earthquakes reported in the historical catalogues the age correlations of carbonate precipitation intervals for the last millennium show a recurrence along the eastern north anatolian fault zone with a mode at 130 330 years that is consistent with a previously proposed paleoseismic recurrence interval of the fault recorded events in carbonate veins indicate a close epicenter d vi paleoearthquakes our results suggest that coseismic carbonate veins could be used to determine paleoseismic records as a supplementary tool to augment paleoseismological techniques this tool has advantages over traditional paleoseismological methods for the understanding of long term earthquake behavior particularly for prehistoric late pleistocene events which cannot be dated easily by traditional paleoseismological methods

global positioning system constraints on plate kinematics and dynamics in the eastern mediterranean and caucasus we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1997 at 189 sites extending east west from the caucasus mountains to the adriatic sea and north south from the southern edge of the eurasian plate to the northern edge of the african plate sites on the northern arabian platform move 18 2 mm yr at n25 5 w relative to eurasia less than the nuvel 1a circuit closure rate 25 1 mm yr at n21 7 w preliminary motion estimates 1994 1997 for stations located in egypt on the northeastern part of africa show northward motion at 5 6 2 mm yr also slower than nuvel ia estimates 10 1 mm yr at n2 4 e eastern turkey is characterized by distributed deformation while central turkey is characterized by coherent plate motion internal deformation of 2 mm yr involving westward displacement and counterclockwise rotation of the anatolian plate the anatolian plate is de coupled from eurasia along the right lateral strike slip north anatolian fault naf we derive a best fitting euler vector for anatolia eurasia motion of 30 7 0 8 n 32 6 0 4 e 1 2 0 1 myr the euler vector gives an upper bound for naf slip rate of 24 1 mm yr we determine a preliminary gps arabia anatolia euler vector of 32 9 1 2 n 40 3 1 1 e 0 8 0 2 myr and an upper bound on left lateral slip on the east anatolian fault eaf of 9 1 mm yr the central and southern aegean is characterized by coherent motion internal deformation of 2 mm yr toward the sw at 30 1 mm yr relative to eurasia stations in the se aegean deviate significantly from the overall motion of the southern aegean showing increasing velocities toward the trench and reaching 10 1 mm yr relative to the southern aegean as a whole

the oceanic biogeochemistry of nickel and its isotopes new data from the south atlantic and the southern ocean biogeochemical divide abstract nickel ni is important for a number of enzymes in oceanic phytoplankton it has received less attention than some other bioactive metals because it is not reduced to extremely low dissolved concentrations in the photic zone however there are strong indications in previous studies that this residual pool is not bio available oceanic ni isotope data are still scarce but have great potential for understanding this issue as well as for understanding the ni mass balance of the oceans now and in the past here we present new concentration and isotope data for the uk geotraces section at 40 s in the atlantic ga10 nickel concentration data show typical nutrient like profiles slightly modified by variable pre formed concentrations in sub surface water masses e g north atlantic deep water nickel isotopes in common with findings in previous studies are homogeneous beneath 500 m at about 1 3 in 60 ni in samples with ni concentrations above 3 3 5 nm the surface south atlantic however has concentrations below 3 nm and shows significantly higher 60 ni up to 1 74 that are closely anti correlated with ni concentrations the data for the deep south atlantic dissolved pool with a 60 ni 1 31 0 12 average and 2sd confirm the homogeneity of the global deep ocean which previous data demonstrate extends all the way to the surface in the upwelling zone of the southern ocean south of the polar front this ni isotope composition is significantly heavier than known inputs to the oceanic dissolved pool this mass balance requires an isotopically light sink that may be represented by sedimentary mn oxide associated ni the magnitude of the isotope fractionation implied by the upper ocean data is not consistent with plausible potential abiotic removal processes rather these data are best explained by biological uptake however consideration of the detailed relationships between ni concentrations and isotope compositions requires that a substantial portion of the oceanic dissolved ni pool is not bio available the data are consistent either with a small preference for the light isotope during uptake about 0 1 or two distinct pools of dissolved ni one bio available and one strongly bound in organic complexes with limited isotopic exchange between them patterns of co variation in ni concentrations and isotopes with the major nutrients point to strong contrasts across the polar front of the southern ocean contrasts that exhibit both similarities and differences with those for the major nutrients and other trace metal micronutrients south of the polar front ni is taken up in modest amounts by diatoms without isotope fractionation north of the polar front the data are most consistent with cyanobacteria as the dominant control on ni uptake leading to significant coupled abundance and isotope variation

uranium isotope systematics of ferromanganese crusts in the pacific ocean implications for the marine 238u 235u isotope system abstract variations of 238u 235u ratio 238u in sedimentary rocks have been proposed as a possible proxy for the paleo oceanic redox conditions although the marine 238u system is not fully understood here we investigate the spatial variation of 238u in modern ferromanganese fe mn crusts by analyzing u isotopes in the surface 0 3 mm depth layer of 19 fe mn crusts collected from 6 seamounts in the pacific ocean 238u values in the surface layers show little variation and range from 0 59 to 0 69 the uniformity of 238u values is consistent with the long residence time of u in modern seawater although the 238u values are lighter than that of present day seawater by 0 24 the light 238u values are consistent with the isotope offset observed in previously reported adsorption experiment of u to mn oxide these results indicate that removal of u from seawater to mn oxide is responsible for the second largest u isotope fractionation in the modern marine system and could contribute to isotopically heavy u to seawater depth profiles of u isotopes 234u and 238u in two fe mn crusts mr12 03 d06 r01 and mc10 cb07 b dated by os isotope stratigraphy were investigated to reconstruct the evolution of the oceanic redox state during the cenozoic the 238u depth profiles show very limited ranges 0 57 to 0 67 for mr12 03 d06 r01 and 0 56 to 0 69 for mc10 cb07 b and have values that are similar to those of the surface layers of fe mn crusts the absence of any resolvable variation in the 238u depth profiles may suggest that the relative amounts of oxic and reducing u sinks have not varied significantly over the past 45 myr however the 234u depth profiles of the same samples show evidence for the possible redistribution of 234u after deposition therefore the depth profile of 238u in fe mn crusts may have been also overprinted by later chemical exchange with pore water or seawater and may not reflect the paleo oceanic environmental changes to assess the potential role of u removal by mn oxides on seawater 238u we calculated seawater 238u with different u sink fluxes into mn oxides using a simple mass balance model the results of these calculations suggest that seawater 238u could have varied significantly throughout earth s history due to changes in the accumulation rate of mn oxides

thermal ionization mass spectrometry u series dating of a hominid site near nanjing china mass spectrometric u series dating of speleothems from tangshan cave combined with ecological and paleoclimatic evidence indicates that nanjing man a typical homo erectus morphologically correlated with peking man at zhoukoudian should be at least 580 k y old or more likely lived during the glacial oxygen isotope stage 16 similar to 620 ka such an age estimate which is similar to 270 ka older than previous electron spin resonance and alpha counting u series dates has significant implications for the evolution of asian h erectus dentine and enamel samples from the coexisting fossil layer yield significantly younger apparent ages that of the enamel sample being only less than one fourth of the minimum age of nanjing man this suggests that u uptake history is far more complex than existing models can handle as a result great care must be taken in the interpretation of electron spin resonance and u series dates of fossil teeth

reading a 400 000 year record of earthquake frequency for an intraplate fault our understanding of the frequency of large earthquakes at timescales longer than instrumental and historical records is based mostly on paleoseismic studies of fast moving plate boundary faults similar study of intraplate faults has been limited until now because intraplate earthquake recurrence intervals are generally long 10s to 100s of thousands of years relative to conventional paleoseismic records determined by trenching long term variations in the earthquake recurrence intervals of intraplate faults therefore are poorly understood longer paleoseismic records for intraplate faults are required both to better quantify their earthquake recurrence intervals and to test competing models of earthquake frequency e g time dependent time independent and clustered we present the results of u th dating of calcite veins in the loma blanca normal fault zone rio grande rift new mexico united states that constrain earthquake recurrence intervals over much of the past 550 ka the longest direct record of seismic frequency documented for any fault to date the 13 distinct seismic events delineated by this effort demonstrate that for 400 ka the loma blanca fault produced periodic large earthquakes consistent with a time dependent model of earthquake recurrence however this time dependent series was interrupted by a cluster of earthquakes at 430 ka the carbon isotope composition of calcite formed during this seismic cluster records rapid degassing of co2 suggesting an interval of anomalous fluid source in concert with u th dates recording decreased recurrence intervals we infer seismicity during this interval records fault valve behavior these data provide insight into the long term seismic behavior of the loma blanca fault and by inference other intraplate faults

deducing paleoearthquake timing and recurrence from paleoseismic data part i evaluation of new bayesian markov chain monte carlo simulation methods applied to excavations with continuous peat growth determining the timing of paleoearthquakes is a central goal of paleoseismology and serves as an important input to seismic hazard evaluations herein we develop a bayesian statistical method for refining the ages of strata and earthquakes and calculating the recurrence of earthquakes based on data from paleoseismic excavations our work extends previous paleoseismic bayesian modeling by simultaneously calculating the joint posterior probability density of recurrence intervals earthquake ages and layer ages to estimate this joint posterior density we employed the metropolis hastings markov chain monte carlo mcmc sampling method we used the wrightwood paleoseismic excavation site as a test bed for our method by comparing the results derived from our simulation to those of previous studies we found that for stratigraphic order constraints our results agreed well with previously used methods however when peat growth was used to constrain the minimum time that separates layers from one another a systematic aging of strata in the lower portion of the stratigraphic column resulted inspection of our results indicated that rather than representing a minimum time that separates layers peat growth instead determined the strata s ages exactly when a constant peat growth rate was prescribed using this information we developed a new method of improving layer age earthquake age and recurrence interval estimates at sites where peat bearing layers are present this method generally produces layer age estimates with less variance than previous methods and requires that both proximal stratigraphic constraints and trench wide constraints be obeyed the benchmarking of the mcmc simulation results shows that simulation provides an effective and efficient way of improving estimates of layer ages earthquake ages and recurrence intervals

heavy nickel isotope compositions in rivers and the oceans abstract nickel is a biologically active trace metal whose dissolved concentration depth profiles in the ocean show nutrient like behaviour if the pronounced removal of nickel from the dissolved phase in the surface ocean and its return in the deep is associated with an isotopic fractionation nickel isotopes may be able to yield constraints on the precise biogeochemical processes involved here we present the first nickel isotope data for seawater along with data for the dissolved phase of rivers one of the principal sources of nickel to the oceans the dissolved phase of rivers exhibits substantial variability in both ni concentration and 60 ni from 2 2 to 35 nmol kg 1 and 0 29 to 1 34 respectively the most striking result from the nickel isotope analyses of rivers is that they are substantially heavier by up to 1 for 60 ni than the range for silicate rocks on the continents a finding that is analogous to that for other transition metal isotope systems if the data presented here are close to representative of the global riverine flux they suggest an annual input of ni to the oceans of 3 6 10 8 moles and a discharge and concentration weighted 60 ni average of 0 80 the relationship between ni isotopes and concentrations shows similarities with those for other transition metal isotope systems where the main control has been suggested to be isotopic partitioning between the dissolved phase and particulates either in the weathering environment or during transport in stark contrast to the rivers the dataset for seawater is very homogeneous with 2sd of the entire dataset being only twice the analytical reproducibility the second main feature is that seawater is distinctly heavier in ni isotopes than rivers the average 60 ni is 1 44 0 15 2sd and only 2 of the 29 seawater analyses have a ni isotopic composition that is lighter than the heaviest river the lack of an isotopic shift associated with the drawdown of nickel concentrations in the surface ocean suggests that the cycling of nickel between the surface and deep ocean is not associated with a pronounced isotopic fractionation the isotopic data also present a mass balance problem the main output of nickel from the oceans sorption to fe mn oxides appears to be similar in isotopic composition to the dissolved phase yet the riverine input is lighter than the dissolved pool this observation either requires other inputs that are isotopically heavy or an output that is isotopically light further large inputs over and above the dissolved riverine source appear to be required by what we know of the elemental budget but the isotopic mass balance suggests that such an input needs to be isotopically much heavier than both the riverine dissolved load and the lithogenic isotopic composition of nickel

earthquake impact on fissure ridge type travertine deposition the role of travertine fissure ridges in reconstructing tectonics and related earthquakes is a challenging issue of recent debate directed at delineating historical prehistorical seismic records indeed direct measurements on a travertine fissure ridge immediately after a seismic event have never been previously performed we describe the co and post seismic effects of a m 3 6 earthquake on fluid flow and travertine deposition in a geothermal area of tuscany italy direct observation allows us to demonstrate that thermal spring re activation is directly influenced by transient seismic waves therefore providing a basis for reconstructing seismic events in the past