a whiff of oxygen before the great oxidation event high resolution chemostratigraphy reveals an episode of enrichment of the redox sensitive transition metals molybdenum and rhenium in the late archean mount mcrae shale in western australia correlations with organic carbon indicate that these metals were derived from contemporaneous seawater rhenium osmium geochronology demonstrates that the enrichment is a primary sedimentary feature dating to 2501 8 million years ago ma molybdenum and rhenium were probably supplied to archean oceans by oxidative weathering of crustal sulfide minerals these findings point to the presence of small amounts of o 2 in the environment more than 50 million years before the start of the great oxidation event

distribution of high field strength elements y zr ree hf ta th u in adjacent magnetite and chert bands and in reference standards fer 3 and fer 4 from the temagami iron formation canada and the redox level of the neoarchean ocean abstract adjacent magnetite and chert bands and reference standards fer 3 and fer 4 from the neoarchean temagami iron formation if show shale normalized rare earth and yttrium rey patterns with low nd yb ratios and positive eu gd and y anomalies indicating that they formed as marine chemical sediments in contrast to previous claims none of the samples shows any ce anomaly indicating the absence of oxidative ce rey decoupling and arguing against oxic conditions in the wider vicinity of the neoarchean temagami seabasin the distribution of zr hf and ta yields zr hf and hf ta ratios that differ from those of chondrites average upper continental crust and local shales suggesting that the temagami if is the only case observed so far in which a significant fraction of these elements is non detrital but sourced from seawater if neoarchean seawater was characterized by zr hf and hf ta ratios similar to those of modern seawater these ratios point towards preferential scavenging of hf over zr and ta as is typical of the modern ocean similar to the 2 9 ga old mozaan if in the pongola supergroup south africa the temagami if shows low th u ratios that differ from those of the respective local shales and from that of average upper continental crust decoupling of u and th results from u4 oxidation in the earth s surface system and fractionated th u ratios in these marine chemical sediments are therefore at odds with the lack of ce anomalies this suggests a different redox sensitivity of the two paleo redox proxies th u and ce rey and demonstrates that the temagami if and the mozaan if warrant further study of other paleo redox proxies

impact of climate and humans on the range dynamics of the woolly mammoth mammuthus primigenius in europe during mis 2 the woolly mammoth mammuthus primigenius was widespread in almost all of europe during the late pleistocene however its distribution changed because of population fluctuations and range expansions and reductions during marine oxygen isotope stage 2 mis 2 these processes were highly dynamic our analyses of 318 radiocarbon dates from 162 localities obtained directly from mammoth material confirmed important changes in mammoth range between 28 6 and 14 1 ka the greenland stadial 3 interval 27 5 23 3 ka was the time of maximum expansion of the mammoth in europe during mis 2 the continuous range was soon fragmented and reduced resulting in the disappearance of mammuthus during the last glacial maximum from 21 4 to 19 2 ka in all parts of the north european plain it is not clear whether mammoths survived in the east european plain the mammoth returned to europe soon after 19 0 ka and for the next 3 4 millennia played an important role in the lifeways of epigravettian societies in eastern europe mammoths became extinct in most of europe by 14 0 ka except for core areas such as the far northeast of europe where they survived until the beginning of the holocene no significant correlation was found between the distribution of the mammoth in europe and human activity

geometry and mechanism of faulting of the 1980 el asnam algeria earthquake from inversion of teleseismic body waves and comparison with field observations the el asnam earthquake of october 10 1980 ms 7 3 provided a wealth of geological and seismological data and is an ideal event for comparing geologically and seismologically derived models the event produced extensive surface faulting in addition to the main tectonic deformation which is clearly a thrust widespread secondary normal faulting was observed at the surface in the southwest region the surface break of a thrust fault could be traced for 24 km in the northeast part of the fault zone normal faults with throws of several meters were observed although no clear thrust type surface breaks were observed in this region geodetic measurements and aftershocks indicate that thrusting was nonetheless the main tectonic mode of deformation in this paper the rupture process of the el asnam earthquake is investigated by inversion of teleseismic p and sh waves the effort is concentrated on the late part of the waveforms which carries information about the faulting in the least understood north eastern segment of the fault zone during the earthquake rupture initiated at the southern terminus of the southwestern fault segment and propagated northward as indicated by the epicentral location and the observable azimuthal directivity of the body wave shapes and amplitudes the seismogenic faulting in the southwestern segment has a thrust mechanism with the following average parameters seismic moment 3 9 1019 n m depth 6 km strike 220 dip 46 and rake 72 the duration of rupture on this fault segment was approximately 10 s which together with the observed fault length of 24 km indicates a rupture velocity of 2 4 km s unconstrained inversions suggest normal faulting in the northeast part of the source region that began immediately following the arrival of the rupture to the northeast region the normal faulting mechanism is in agreement with that observed for the large surface fault scarps in this region guided by the evidence from aftershocks and geodetic measurements a solution with a thrust type mechanism was also sought using a priori constraints based on the field observations the observed strike and slip angle we obtain the following thrust source mechanism for the northeast segment seismic moment 3 6 1019 n m depth 6 km strike 230 dip 20 and rake 91 this solution requires that the thrusting in the northeast be initiated 10 s after the arrival of the rupture from the southwest suggesting that some time is required to overcome the geometric barrier marked by the abrupt change in the dip and azimuth inversions are nonunique with respect to the seismic moment associated with normal faulting the ambiguity being caused by the limited bandwidth of the observed body waves the moment estimated from the surface waves at periods about 300 s however favors thrust faulting to be dominant in the northeast region

nied seismic moment tensor catalogue for regional earthquakes around japan quality test and application abstract we have examined the quality of the national research institute for earth science and disaster prevention nied seismic moment tensor mt catalogue obtained using a regional broadband seismic network freesia first we examined using synthetic waveforms the robustness of the solutions with regard to data noise as well as to errors in the velocity structure and focal location then to estimate the reliability robustness and validity of the catalogue we compared it with the harvard centroid moment tensor cmt catalogue as well as the japan meteorological agency jma focal mechanism catalogue we found out that the nied catalogue is consistent with harvard and jma catalogues within the uncertainty of 0 1 in moment magnitude 10 km in depth and 15 in direction of the stress axes the nied mt catalogue succeeded in reducing to 3 5 the lower limit of moment magnitude above which the moment tensor could be reliably estimated finally we estimated the stress tensors in several different regions by using the nied mt catalogue this enables us to elucidate the stress deformation field in and around the japanese islands to understand the mode of deformation and applied stress moreover we identified a region of abnormal stress in a swarm area from stress tensor estimates

hafnium and neodymium isotopes in seawater and in ferromanganese crusts the element perspective abstract hafnium and nd isotopes are increasingly used as paleoceanographic proxies comparing the mantle crust array and the seawater array in plots of e hf vs e nd it has been observed that for a given e nd value the corresponding e hf value is higher for seawater than it is for terrestrial rocks while this difference had initially been explained by significant hydrothermal input of mantle hf into seawater the currently favoured explanation is incongruent weathering of continental rocks producing radiogenic riverine hf input we here address this topic from the perspective of the behaviour of these two elements in seawater and in ferromanganese fe mn crusts we distinguish between a truly dissolved and a dissolved hf and nd pool the latter being comprised of truly dissolved and colloid bound colloidal hf and nd while there exists a hydrothermal pathway for colloid bound dissolved mantle hf into the oceans there is in marked contrast to nd no important riverine pathway for colloidal or truly dissolved continental hf owing to their respective chemical speciation in seawater there exists truly dissolved nd in the ocean while the amount of truly dissolved hf is insignificant neodymium is in exchange equilibrium between local seawater and both the hydrous fe and mn oxides hydrogenetic fe mn crusts are composed of due to continuous ad and desorption there is continuous isotopic re equilibration and the isotopic composition of nd in a fe mn crust reflects that of truly dissolved nd in local ambient seawater in contrast hf is only associated with the hydrous fe oxides on which it forms surface precipitates that do not exchange with seawater due to this lack of isotopic re equilibration the isotopic composition of hf in a fe mn crust is the average of that of all the hf scavenged during the lifetime of the hydrous fe oxide particles since the hf bearing hydrous fe oxides in a fe mn crust do not form from local ambient seawater at the crust s growth site but are advected as colloids or fine particles their hf isotopic composition depends on the origin and migration pathway of these colloids hence while nd isotopes in fe mn crusts provide reliable information on truly dissolved nd in local ambient seawater hf isotopes rather indicate the origin and pathway of hydrous fe oxide colloids and might differ from truly dissolved hf in local ambient seawater this may explain the occasional decoupling of nd and hf isotopes in fe mn crusts and supports the notion of a significant hydrothermal mantle signal of hf in seawater

the europium anomalies in banded iron formations and the thermal history of the oceanic crust abstract the ree rare earth element patterns in banded iron formations bif s from various sites in north america two sites in finland and three drillcores of the hamersley basin in western australia have been investigated using icp ms inductively coupled plasma mass spectrometry and inaa instrumental neutron activation analysis the results of this study as well as existing data show trends in the eu anomalies bif s older than 2 5 ga exhibit positive eu anomalies while younger ones exhibit none in chemical sediments between 2 5 and 2 3 ga both trends can be found because of the worldwide distribution of bif s this feature can be considered as a global change in the conditions controlling ree mobilization consideration of the redox conditions of bif formation in comparison with the calculated and measured eu redox equilibria suggests that a eu anomaly points to a dominantly hydrothermal source of ree s with solution temperatures above 175 c we suggest that the disappearance of the eu anomaly towards the proterozoic marks a change from mainly high temperature hydrothermal to dominantly low temperature alteration

zooarchaeology of the layers from dorochivtsy iii ukraine palaeolithic archaeological sites of the western ukraine are clustered along the prut and dniester rivers different sites provided data enabling reconstruction of the paleoenvironment chronology and cultures of human group during the upper paleolithic notably molodova v during the second part of the pleniglacial between 23 000 and 20 000 years bp palaeoclimatic variations took place the intensification of cold and arid conditions is liable to force human groups to adapt to a changing environment little is known about this period with only a few assemblages ongoing excavations continue to provide new data the archaeological site of dorochivtsy iii has an important sequence stratigraphy with several archaeological layers among the seven upper palaeolithic layers layers 6 5 4 and 3 testify to activities of a human group during the upper pleniglacial we studied the faunal assemblages applying zooarchaeological methods identifying mammoth mammuthus primigenius reindeer rangifer tarandus horse equus sp and fox alopex lagopus vulpes vulpes the gravettian layers 3 4 5 have anthropogenic clues in connection with subsistence activities oriented on reindeer then horses and finally fox concerning mammoths we cannot define the modes of acquisition and use these occupations have been interpreted as recurrent hunting occupations linked to procurement of local flint and lithic production for butchering activities layer 6 dated to 22 330 100 bp is remarkable because of previously unseen practises the lithic assemblage combined with bone industry and engraved tusk is a novel set of cultural elements in this area called ancient epigravettian this layer testifies to the diversity of human activities during the upper pleniglacial and to the particular status of mammoth ivory as an artistic medium palynological data and taphonomic observations on bones indicate the persistence of relatively moist conditions during some periods which could favour the movement of human groups although little is known about the upper pleniglacial period dorochivtsy iii testifies to the continuity of a large exploitation of the territory of the dniester valley

sulfur and carbon isotopes in archean banded iron formations implications for sulfur sources abstract sulfur isotope ratios of pyrite from two late archean banded iron formations were used to constrain possible sources of sulfur the iron formations studied were the temagami iron formation which hosts the sherman mine near temagami and the boston iron formation including the adams mine south of kirkland lake both in ontario in both cases algomantype oxide facies magnetite chert ores predominate the sulfur studies were supplemented by limited carbon isotopic data for the sherman mine iron formation in the sherman mine occurs on both limbs of a regional synformal structure each iron formation unit caps a thick calc alkaline andesite dominated volcanic sequence with one band hosted in sedimentary rocks of turbidite origin the adams mine includes four major iron formation bands interbedded with mafic and ultramafic volcanic rocks and greywacke of turbidite origin the sulfur isotope statistics for averages of pyrites from these three units are sherman mine volcanic hosted suite 34 s 1 7 4 6 n 14 sherman mine sediment hosted suite 34 s 1 4 1 6 n 43 and adams mine 34 s 1 8 2 9 n 17 these averages differ by from juvenile sulfur and together with their limited dispersions suggest a predominantly unfractionated source of sulfur it is argued that this sulfur has been derived from the associated volcanic piles most of the pyrite occurs as disseminated grains in oxide facies iron formation and interbedded clastic sediments a distinctive nodular pyrite in the sherman mine sediment hosted suite occurs in cherty graphitic sulfide facies iron formation while the sulfur isotopic properties of this subset 34 s 0 0 0 8 are not suggestive of biogenic sulfur the geological setting and carbon isotopic compositions of associated graphite 13 c 34 imply that anaerobic bacterial processes were active in this reducing environment the apparent lack of biogenic sulfide is rationalized by models suggesting that archean marine basins differed from phanerozoic analogues in various parameters which influence sulfur isotopic characteristics it is argued that biogenic sulfide is probably a significant component of the sulfur in sherman mine nodular pyrite

age and timing of igneous activity in the temagami greenstone belt ontario a preliminary report the southernmost remnants of archean supracrustal and intrusive rocks in eastern ontario are exposed through a window in the early proterozoic huronian supergroup near the town of temagami u pb zircon ages from this area indicate the presence of some of the oldest felsic magmatism so far discovered in this portion of the superior province the iceland lake pluton 2736 2 ma and a nearby rhyolite flow are contemporaneous which establishes that at least some of the intrusive rocks in the region are synvolcanic and coeval with the oldest volcanic cycle the youngest plutonic activity is the emplacement of a late rhyolite porphyry dike at 2687 2 ma an age that is bracketed by the 2675 2700 ma emplacement ages of late internal plutons found throughout the abitibi subprovince the 2736 ma dates however are older than the nearest portion of the exposed abitibi some 120 km to the north near kirkland lake

stress pattern in portugal mainland and the adjacent atlantic region west iberia the portuguese mainland territory is located close to the azores gibraltar plate boundary in a tectonic setting responsible for significant neotectonic and seismic activities however few data concerning the present regional lithospheric stress field were available as testified by recently published maps of stress indicators for the europe and mediterranean regions one of the authors already presented a synthesis on this subject cabral 1993 where geological and geophysical stress indicators were considered in this paper we introduce new information mainly a considerable amount of borehole breakout data the updated data set comprises 32 reliable stress indicators showing a mean azimuth of 145 standard deviation 21 for the maximum horizontal stress direction shmax on the average the geological data are rotated clockwise and the focal mechanism data deviated anticlockwise to that azimuth while the borehole elongation results are consistent with the mean shmax trend these differences in stress trend suggest a regional progressive rotation of the shmax direction from nnw sse to wnw ese since the upper pliocene to estimate stress trajectories new and published stress indicators in the adjacent atlantic area and northern africa were also investigated showing a very uniform nw se shmax trend in west iberia a high level of horizontal compressive stress acting oblique to the western portuguese continental margin is inferred and interpreted in view of a proposed regional geodynamical model of activation of this passive margin with the nucleation of a subduction zone in the atlantic sw of iberia at the gorringe submarine bank which is propagating northward along the base of the continental slope at the transition between thinned and normal continental crust

accuracy of modern global earthquake catalogs we compare several modem 1977 present worldwide earthquake catalogs to infer their completeness earthquake origin time and hypocenter location accuracy magnitude scalar seismic moment errors and difference between individual focal mechanism moment tensor solutions the harvard centroid moment tensor cmt us geological survey usgs mt usgs first motion fm focal mechanism pde and isc catalogs have been analyzed and compared the catalogs completeness and accuracy vary in time and depend on earthquake depth and tectonic environment we propose a new statistical method for evaluating catalog completeness and show the results for the cmt dataset a difference in frequency range of seismic waves used in earthquake processing leads to varying degrees of catalog completeness for foreshocks and aftershocks close in time earthquake origin time versus centroid time as well as hypocenter location versus centroid location can be explained well by earthquake scaling relations comparing moment magnitudes and regular earthquake magnitudes yields estimated magnitude uncertainties and shows that latter magnitudes poorly estimate earthquake size for large events moment errors reported in the cmt solutions are well correlated with the cmt gs mt magnitude difference and hence indicate magnitude uncertainty well a normalized seismic moment tensor has 4 d f and its accuracy can be represented as the non double couple non dc component value the 3 d angle phi of dc source rotation and a position of the rotation pole our results suggest that a routinely determined non dc component is in most cases only an artifact the distribution of the phi value varies over catalog time earthquake depth focal mechanism and magnitude the seismic moment errors and the value of the non dc component are indicative of the phi value for the best solutions the 3 d angle in the cmt catalog is on the order of 5 7degrees the cmt catalog is obviously the best dataset in completeness and accuracy of its detailed solutions our results specifying uncertainties and completeness of global earthquake catalogs can be used in studies of geodynamic processes tectonic deformation associated with earthquakes earthquake stress analysis and in many other applications of earthquake catalog data seismogram interpretation techniques can be reviewed and possibly revised in light of these results c 2002 elsevier science b v all rights reserved

estuarine distributions of zr hf and ag in the hudson river and the implications for their continental and anthropogenic sources to seawater 1 zirconium and hf in seawater are derived from continental weathering and are transported to the oceans by rivers but the modification of this flux with estuaries is largely unknown furthermore there is no information as to whether there is a pollutant source of these metals that might affect their budget calculations in the modern ocean to address the riverine flux and potential anthropogenic sources the distributions of dissolved zr and hf have been measured in surface and bottom water through the hudson river estuary the distribution of ag is included because it is sensitive to urban sources and has partial similarities in its distribution to those of zr and hf there is about 50 removal of zr and hf in surface water relative to their freshwater end member concentrations of 243 and 3 1 pmol kg as salinity starts to increase but an urban source of these metals midestuary may obscure greater removal silver concentrations in surface water are below the detection limit until salinity of 3 5 is reached the concentrations of zr and hf 0 5 m above the bottom are 1 5 to 3 times higher than their surface water concentrations throughout the estuary and may result from input of groundwater diffusion from pore fluids or inclusion of colloidal phases in our analyses downstream of the turbidity maximum bottom water ag concentrations are high due to release from particles that originally formed within the estuary and were moved inland following the spring freshet this process may also affect zr and hf the increase in the freshwater atomic zr hf ratio from 70 to 80 characteristic of terrestrial rocks to the elevated zr hf 110 ratio of seawater takes place at middle to high salinity due to enhanced release of zr from resuspended particles and slower removal rates compared to hf a main implication of this study is that estuaries are a sink for zr and hf the reduction of the predicted export of continental zr and hf to the oceans increases their previously calculated seawater residence by as much as 2 to 4 times assuming rivers dominate the supply of zr and hf to seawater

centroid moment tensor solutions for 113 large earthquakes in 1977 1980 abstract the centroid moment tensor technique is applied to 113 large earthquakes of the period 1977 1980 including all the shallow events with magnitude mb ms or ml 6 5 we use digital data recorded by the global digital seismograph network gdsn and international deployment of accelerometers ida networks solutions are determined for three sequences of events close in time by inverting mantle wave data simultaneously for multiple sources

control of rupture by fault geometry during the 1980 el asnam algeria earthquake summary the el asnam earthquake of 1980 october 10 ms 7 3 occurred on a segmented reverse fault in the atlas mountains of algeria this report re examines the teleseismic data for the main shock and major aftershocks in the light of detailed studies of the surface breaks geodetic changes and aftershock distribution the observed thrust fault is split into southern central and northern segments by distinct offsets and changes in trend the southern and central segments are each about 12 km long but the northern segment showed only 3 4 km of surface thrust breaks however widespread tensional faulting on ridges in the north east area together with focal mechanisms of locally recorded aftershocks indicates that a series of imbricate listric thrusts exists to the north of the northern fault segment using isc arrival time lists a relative relocation scheme is applied to the main shock and major aftershocks to improve their locations with respect to the mapped faults the main shock epicentre was at the south west end of the fault system in a zone where the thrust has a zig zag surface trace by contrast most of the major aftershocks were located further north east and were associated with the northern thrust segment and the imbricate thrusts to the north the largest aftershock mb 6 1 which occurred about 3 hr after the main shock was located to the east of the main thrust fault beneath the chelif alluvial basin first motion fault plane solutions are presented for the main shock and largest aftershock the main shock solution indicates a fault plane dipping 54 nw with strike 040 the aftershock solution however has a more e w trend 080 in agreement with the trends of the basin edges near its location the rupture history of the main shock is investigated by forward modelling of the long period p waves four subevents are clearly distinguishable the first three subevents occurred in rapid succession and contributed to the first cycle of the p wave radiation these three subevents represent the successive rupturing of the southern central and northern fault segments in order to match the observed waveforms these three ruptures must have different mechanisms and moments the fault segments have successively shallower dipts from south to north 54 45 and 40 respectively and the central segment had the largest moment release in agreement with the geodetic data of ruegg et al the delay times between the three sources suggest a rupture velocity of about 3 5 km s 1 and their nucleation depths were 7 km the junctions between the fault segments acted as geometric barriers to the rupture propagation but were broken by its passage the fourth subevent of the main shock produced the second cycle of the p wave radiation it began about 18 s after the first i e several seconds after the end of the third rupture nabelek demonstrates that the fourth subevent occurred on a shallow angle 20 thrust plane examination of the locally recorded aftershocks suggests that this plane is a decollement surface underlying the imbricate thrusts of the north east area the total seismic moment found from the body wave modelling is 7 7 1026 dyne cm in good agreement with geodetic and surface wave studies

rare earth element systematics of the chemically precipitated component in early precambrian iron formations and the evolution of the terrestrial atmosphere hydrosphere lithosphere system irrespective of provenance age and metamorphic grade the chemically precipitated component in early precambrian 2 3 ga iron formations ifs displays smyb cn 1 which reflects the corresponding ratios of contemporaneous seawater in conjunction with end if end shale jacobsen and pimentel klose 1988a b this rare earth element ree signature reveals that the ree distribution in early precambrian ifs must be explained by mixing between a marine bottom and a surface water component and that the rees and by analogy the fe cannot be derived from weathering of a continental source eusm n ratios of detritus free ifs are controlled by the marine bottom water component where eusm cn 1 results from ree input from high temperature high t hydrothermal fluids which received their ree signature during high t alteration of oceanic crust at spreading centres decreasing eusm cn of ifs with decreasing depositional age reflect the vaning importance of high t compared to low t 200 c hydrothermal fluids hence oceanic crust alteration for the ree budget of marine bottom waters and are related to decreasing upper mantle temperatures smyb n ratios of detritus free ifs are controlled by the marine surface water component whose ree distribution is affected by the same processes which operate today in the entire ocean mixing calculations reveal that smyb cn in early precambrian marine surface waters was significantly lower than it is today to explain this difference two mechanisms are discussed on the basis of higher pco2 and lower po2 levels of the precambrian atmosphere 1 1 higher co32 in precambrian river and coastal waters and 2 2 redox cycling of the rees at an oceanwide chemocline which separated anoxic and oxic water masses however these processes are synergetic and could have operated in unison the ree distribution in precambrian ifs is described as a result of mixing in a multicomponent system where high t and low t hydrothermal fluids contributed to the marine bottom water and ree input from the dissolved ree pool in river waters after some modification in estuaries dominated the ree distribution in marine surface waters after mixing of bottom and surface waters their combined ree load was quantitatively scavenged onto precipitating iron oxihydroxides or iron carbonates and deposited with the chemically precipitated component after addition of variable amounts of clastic detritus this eventually resulted in the ree distribution observed in precambrian ifs

stress analysis in the intraplate area of gazli uzbekistan from different sets of earthquake focal mechanisms occurrence of intraplate earthquakes have been related either to reactivation of preexisting zones of weakness in a uniformly oriented regional stress field or to local stress changes more recently buildup of pore pressure anomalies has been proposed to explain both the low recurrence rate and some misorientation of rupture planes in the prevailing regional stress field in this study we analyze local stress field orientation in the area of the three ms 7 0 gazli western uzbekistan earthquakes by using different sets of earthquakes focal mechanisms we show that stress tensor inversions from both seven 4 2 ms 7 0 forty five 0 1 ml 3 2 and twenty five 1 0 ml 3 2 earthquake focal mechanisms give constant maximum horizontal stress direction in agreement with the one deduced from the india asia collision the best model for the local stress tensor exhibits a significant 25 discrepancy from vertical for one of the principal stresses we note moreover that the common assumption that one principal stress axis is oriented vertically is not strictly supported by stress states derived from earthquake focal mechanisms available in the world stress database by evaluating each hypothesis of stress inversion methods from earthquake focal mechanisms it is shown that especially in intraplate settings the first motion focal solution should be the most appropriate one for a formal inversion and that the magnitude of the considered event may not be the only criterion to assess the quality of a stress inversion this is particularly timely because more and more focal mechanisms are moment tensor solutions instead of first motion solutions concerning the gazli sequence the slip conditions pore pressure and frictional coefficient are evaluated for each of the three mainshocks in terms of an independently determined local stress field because variations in orientations between local and regional stress field are not detected and because the three mainshock fault planes seem to be relatively well oriented for a frictional activation in the local stress field it is concluded that this seismic sequence is localized on preexisting weakness zones and is not due to local stress orientation anomalies

collagen stable isotopes provide insights into the end of the mammoth steppe in the central east european plains during the epigravettian higher 15 n values in bone collagen of mammoth mammuthus primigenius compared with coeval large herbivores is a classic trait of the mammoth steppe an exception applies to the epigravettian site of mezhyrich ca 18 17 4 ka cal bp in the central east european plains where mammoth bones have 15 n values equivalent to or in a lower range than those of horse specimens equus sp we expanded our preliminary dataset to a larger sampling size of mammoth other large herbivores and carnivores from contemporaneous and nearby sites of buzhanka 2 eliseevichi and yudinovo the unusual low mammoth 15 n values were confirmed at buzhanka 2 and for some specimens from eliseevichi while most individuals from yudinovo displayed the expected high 15 n values meaning similar to those of the large canids the possibility of a contrast in migration pattern is not supported since the 34 s values a marker of mobility do not correlate with the 15 n values of mammoth bone collagen no clear chronological tendency could be revealed at least not at the scale of radiocarbon dating the low range in 15 n values is likely to reflect a change in the specific niche of the mammoth in the southern part of its distribution

field and teleseismic observations of the 1981 golbaf sirch earthquakes in se iran summary in 1981 june and july two large earthquakes occurred on the gowk fault system in south east iran both earthquakes were associated with surface faulting showing a combination of reverse and right lateral strike slip motion on parallel adjacent faults striking north south and dipping both east and west such motion can be seen to have occurred in the recent past and is responsible for the formation of elongated alluvium filled depressions in the footwall region common to both the east and west dipping faults the earthquake of june 11 involved motion along about 15 km of the gowk fault system with a moment of about 1 0 1026 dyne cm the earthquake of july 28 was larger and occurred farther north with movement along at least 65km of the gowk fault system and a moment of about 7 1026 dyne cm surface faulting in both earthquakes was complex and spread over several kilometres width on en echelon fault segments as well as on faults dipping both east and west the long period wwssn seismograms of these two mainshocks are unusually complicated and clearly made up of several individual subevents sensible interpretation of these waveforms without guidance from the surface faulting and the long period sro moment tensor inversion of dziewonski woodhouse would be impossible however a combination of these three data sources allows a geologically plausible interpretation of the rupture processes in these earthquakes to be made although the faulting in both mainshocks was on the same large scale feature the gowk fault the rupture zones of the two earthquakes did not apparently overlap and were separated by a gap of 5 km along strike in which both coseismic and recent geological displacements are very small rupture in both mainshocks appears to have nucleated near this gap and to have propagated away from it other such gaps are visible along the irregular displacement of the northern fault break and may have been the nucleation positions for individual subevents of the july 28 earthquake recognition of such nucleation sites is of obvious importance to earthquake prediction efforts

neodymium isotopes in archean seawater and implications for the marine nd cycle in earth s early oceans abstract published neodymium nd isotopic data for archean iron formations if suggest that overall seawater throughout the archean typically displayed 143nd 144nd close to bulk earth values with nd t between 1 5 and 2 5 neodymium isotopic ratios in seawater during deposition of the 3 8 isua greenland if likely displayed positive nd 3 8 ga of 2 5 as suggested by if g an isua reference if that is considered the best archive for early archean seawater seawater 143nd 144nd ratios dominated by radiogenic nd positive nd t seem to have persisted for much of the archean as if from the pietersburg greenstone belt south africa suggest seawater nd 2 95 ga 1 however similarly aged 2 9 ga ifs from south africa indicate that significant variations in seawater 143nd 144nd occurred and clearly show influences from isotopically distinct crustal sources these variations are apparently related to depositional environment with cratonic margin shallow water ifs possessing a continental nd t of 3 while ifs associated with sub aqueous mafic volcanics display more radiogenic positive nd t values such variation in seawater 143nd 144nd is not possible in an isotopically well mixed ocean and similar to today it appears that marine nd cycling in the archean produced water masses with distinct nd isotopic ratios since the presence of banded iron formations requires a reducing archean ocean capable of transporting fe metal oxide precipitation and scavenging processes near deep sea hydrothermal vent systems would not have scavenged mantle nd i e nd sourced from alteration of oceanic crust we propose that bulk anoxic seawater prior to 2 7 ga possessed relatively constant positive nd t of 1 to 2 whereas local shallow water masses associated with exposed evolved crust could possess distinctly different lower nd t

the effect of assumed source structure on inversion of earthquake source parameters the eastern hispaniola earthquake of 14 september 1981 abstract teleseismic body waves from the 14 september 1981 eastern hispaniola earthquake were inverted using different source structure models comparison of the inversion results showed that the non double couple clvd component of the moment tensor may be interpreted as a measure of deficiencies in the inversion procedure increasing the complexity of the source structure model to improve the fit of the green9s functions to the observed seismograms improving the data set9s azimuthal coverage and leaving the time function free to compensate partially for the deficiencies of the green9s functions all can decrease the size of the clvd component for an earthquake in which the direct arrival is clearly separated from the crustal phases an inversion of the direct p and sh waves only assuming a half space source structure model is adequate to determine the source double couple orientation and time function the moment tensor for the hispaniola earthquake indicates thrust faulting on an east west striking fault plane dipping 30 to 35 to the south the pressure axis is oriented north south the intermediate axis east west and the tension axis is nearly vertical the source time function is a simple 3 sec long triangular pulse the slip vector is consistent with the slip vectors for nearby earthquakes as determined in other studies and indicates that the slab is moving down dip to the south

dissolved zirconium and hafnium distributions across a shelf break in the northeastern atlantic ocean abstract dissolved zr and hf distributions have been determined for five stations located across the shelf break in the northeastern atlantic ocean on the celtic approaches for stations in deep water the range in zr concentrations has been found to be 70 180 pmol kg and the range in hafnium concentrations 0 4 1 1 pmol kg the distributions with depth are indicative of a nutrient like scavenging regeneration behavior in seawater although the dissimilarity with silicate and nitrate for samples below the nutricline suggest that other mechanisms are also important in defining the oceanic distribution of these elements in contrast the concentrations of zr and hf at the station located closest to land are highest in surface waters and decrease with depth although salinity does not indicate dilution of seawater with freshwater with high zr and hf concentrations the ratio of dissolved zr to hf in seawater is higher and more variable than is found for the majority of terrestrial rocks or predicted from thermodynamic considerations fractionation due to small differences in their interactions with particulate material is implicated

lithology and stratigraphy of loess soil series and cultural layers of late paleolithic campsites in eastern europe comparative analysis of the late paleolithic cultural layer occurrence in different regions of the east european plain provided new materials on the late pleistocene chronostratigraphy a majority of known sites are located within the areas of late pleistocene loess of eolian origin it is not uncommon that loess forms only the upper member of the enclosing deposits overlying the cultural layer numerous radiocarbon dates available at present not only allow definition of the age of the sites themselves but also elucidation of the sequence of changes in climate and environments reflected in horizons of paleosols and cryogenic formations the sedimentary series enclosing the late paleolithic cultural layers differ from the surrounding area in completeness of stratigraphic record and in sequence of cycles of sedimentogenesis the ground surface at the campsites was stable at the time when eolian sedimentation on the surrounding areas was gaining in intensity it is not inconceivable that the sites were chosen for human dwelling due to this specific feature

mainshock and aftershock analysis of the june 17 1996 deep flores sea earthquake sequence implications for the mechanism of deep earthquakes and the tectonics of the banda sea one of the largest mw 7 8 deep earthquakes 595 km in recorded history occurred beneath the flores sea on june 17 1996 we analyze broadband body waveforms to determine the seismic source characteristics of this important earthquake the source time function has a small initial subevent 5 s duration followed by three major subevents with a total source duration of 29 s directivity analysis indicates an unilateral rupture to the east southeast with a subhorizontal rupture length of 75 km a time independent moment tensor timt inversion gives a total seismic moment of 5 4 1020 n m mw 7 8 a time dependent moment tensor tdmt inversion indicates rupture on a near vertical fault strike of 130 dip of 80 sw rake of 166 during the first 5 s releasing 8 of the seismic moment the major part of the moment was released along a shallower dipping plane strike of 100 dip of 55 rake of 45 this change of faulting geometry may imply that the rupture initiated at a structural thermal or phase boundary of high stress concentration and then triggered the major moment release along a regional weak zone the mainshock produced at least 23 mb 2 9 aftershocks within the first 3 days seventeen of the largest aftershocks were located using the joint hypocenter determination algorithm the aftershocks define a plane dipping antithetically to the dip of the subducting slab with lateral and depth dimensions of 145 km and 76 km respectively the aftershock locations correlate with the southeast striking nodal plane of the moment tensor mechanism

initial rupture and the main fault of earthquakes a comparison of the body wave first arrivals and cmt data for the kamchatka commander region abstract centroid moment tensor cmt data by dziewonski and coworkers and body wave first arrival earthquake parameters obtained from local networks were simultaneously investigated for 55 earthquakes in the kamchatka commander region which occurred from 1977 to 1986 the magnitude range considered was 4 5 7 5 the focal depths were 0 190 km the following parameters were studied origin time hypocenter coordinates focal mechanism and seismic moment the first arrival data were referred to the initial rupture in the earthquake focus and cmt estimates to the main earthquake fault the principal results obtained are as follows shifts of the centroid location with respect to initial hypocenters and the change or stability of the type of faulting from the initial rupture to the main fault depend on the tectonic position of the hypocentral area the character of the source time function depends on the sign of the main fault propagation i e downwards upwards horizontally

an experiment in systematic study of global seismicity centroid moment tensor solutions for 201 moderate and large earthquakes of 1981 data from the global digital seismograph network were used to obtain centroid moment tensor solutions using the method of dziewonski et al 1981 results were obtained for 201 earthquakes ranging in seismic moment from 7 1023 to 3 1027 dyne cm the wide dynamic range of the sro asro stations allows us to investigate using the same algorithm series of events among which the smallest and the largest may differ in moment by a factor as large as 1000 among the events studied is a particularly interesting series in january 1981 off the island of honshu the main shock was preceded by three foreshocks and followed by four aftershocks all falling within the range of our analysis there is an indication that the source mechanism changes with the size of the event statistical analysis of the results for all earthquakes reveals that the half duration of shallow and intermediate events is approximated by 1 6 10 8 m01 3 the shifts in origin time for deep focus earthquakes are indicative of the general complexity of these events which depends only weakly on the seismic moment the extreme departures from a double couple mechanism seem to depend both on the moment and on the focal depth while for shallow earthquakes these departures decrease from a maximum at about 1025 dyne cm with increasing moment the reverse appears to be true with respect to deep focus earthquakes shallow earthquakes north of new guinea and along the solomon islands show systematic and substantial departures from the double couple mechanism

comparison of centroid moment tensor and first motion solutions for western mediterranean earthquakes abstract comparison of centroid moment tensor and first motion solutions shows that the two different methods give compatible solutions for moderate sized earthquakes in the western mediterranean while the centroid moment tensor solution provides a good indication of the general style of deformation occurring in an area careful consideration of the first motion solution is still necessary for detailed study of source mechanics there is no obvious character of the centroid moment tensor solution such as small values of moment or large non double couple contribution that can be used as diagnostic of a significantly different first motion solution

the regional intraplate stress field in south america a compilation of lithospheric stress directions for continental south america and the inferred major patterns of the regional intraplate stress field are presented stress orientations are based primarily on earthquake focal mechanisms and quaternary fault slip inversion published in the literature four new focal mechanisms based on short period p wave modeling and selected centroid moment tensor solutions published by u s geological survey consistent with p wave first motions at south american and other world wide standard seismograph network stations are also included in the data base the observed patterns of intraplate stresses may be useful in constraining numerical models of the plate driving forces in the south american plate in the andean plateau altitudes greater than 3000 m n s extensional stresses predominate e w compressional stresses are observed in the sub andean and platform regions extending up to about 1000 km east of the andes the maximum horizontal stress shmax is uniformly oriented in the e w direction throughout western south america averages of the shmax direction at grid points spaced 2 5 o were taken as representing the regional field the e w direction of this regional field is not affected by the change of strike of the andean chain nor by the contact of a flat subducted slab underneath the regional shmax direction is oriented 15 o more clockwise than the direction of the nazca plate convergence the difference between the regional shmax orientations and the absolute plate motion may be only about 6 o this may indicate that contact forces with the nazca plate may not be the only major contributor to the intraplate stresses in western south america the eastern limit of this andean stress province seems to coincide with aseismic regions in the upper amazon basin and in the paraml basin in the central amazonian region seismicity and stress data suggest a seismic province with n s compressional stresses the origin of these stresses is not yet clearly understood but could possibly be related to lower crustal loading along the middle amazon basin in northeastern brazil seismicity is characterized by upper crustal strike slip earthquakes bordering the potiguar marginal basin a model is proposed for this region in which the stress field is the result of a superposition of regional e w compressional stresses and local extensional stresses oriented perpendicular to the continental margin possibly related to density contrasts and sediment loading in the continental shelf

new evidences about human activities during the first part of the upper pleniglacial in ukraine from zooarchaeological studies abstract the upper pleniglacial between 23 000 20 000 bp is characterized by the intensification of cold climate and is followed by the maximum extent of ice sheets there is a little bit information about the human activities during this period new archaeological excavations in ukraine permit to evidence data about behavioural human adaptations these open air sites are on the one hand pushkari 1 excavation vii pogon excavation vii and obollonia in the desna valley and on the other hand dorochivtsy iii in the dniester valley these sites are characterised by atypical lithic industries made on local flint relied to the gravettian but containing epigravettian or aurignacoid elements in order to better understand the subsistence strategy we carried out zooarchaeological and taphonomical studies which allow us to reveal the strategy of fauna exploitation by the human groups we highlighted that all these sites are characterized by a restricted faunal spectrum with the presence of mammoth reindeer horse and carnivores mainly fox vulpes vulpes and alopex lagopus and wolf in the dniester valley the reindeer was the most exploited whereas the mammoth is the most exploited in the desna valley indeed it was probably hunt in pushkari 1 maybe in pogon and obollonia it was exploited as combustible food resources and bones as raw material in dorochivtsy iii 6 ivory was used to make tools and as artistic support indeed this site and obollonia present grooved ivory points this is the oldest occurrence of this kind of artefacts in the both regions moreover two engraved tusks presenting more or less figurative pictures were found in dorochivtsy iii l 6 and obollonia the other large herbivores were also consumed and carnivores were exploited for their pelts in all these sites the settlements are recurrent camps with little development occupied during varied seasons oriented to hunting and butchering activities linked with exploitation of local flint these sites demonstrate the continuity of human occupations within the eastern european plain with the persistence of hunting methods and the relative diversity of animal exploitation during the upper pleniglacial these sites are really important for the understanding of cultural processes in the eastern european upper palaeolithic and particularly for the understanding of epigravettian origin

landscape climate and mammoth food resources in the east european plain during the late paleolithic epoch abstract typical mammoth inhabited the east european plain during the second half of the late pleistocene glaciation under conditions of extremely arid climate periglacial mostly open landscapes formed a vast hyperzone cryohyperzone that occupied the place of the modern tundra forest and steppe zones to assess the available foodstuffs for mammoth provision data concerning productivity and nutritive value of modern herb and grass vegetation that may be considered as more or less close analogues of periglacial communities can be used the central part of the late pleistocene periglacial hyperzone was most favorable for mammoths those regions were well endowed with water in large rivers as well as snow and ice and presented the richest fodder base because trees and bushes persisted in valleys while higher watersheds were occupied by periglacial steppe climate warming and consequent degradation of permafrost resulted in instability of the land surface thermokarst and expansion of wetlands the snow thickness increased due to more abundant snowfall in winter and made grazing difficult for mammoths the first interstadial warming affected the less hardy early mammoths while the progressive warming towards the holocene appeared fatal to the typical mammoth

continentally derived solutes in shallow archean seawater rare earth element and nd isotope evidence in iron formation from the 2 9 ga pongola supergroup south africa abstract the chemical composition of surface water in the photic zone of the precambrian ocean is almost exclusively known from studies of stromatolitic carbonates while banded iron formations ifs have provided information on the composition of deeper waters here we discuss the trace element and nd isotope geochemistry of very shallow water if from the pongola supergroup south africa to gain a better understanding of solute sources to mesoarchean shallow coastal seawater the pongola supergroup formed on the stable margin of the kaapvaal craton 2 9 ga ago and contains banded iron formations ifs that represent the oldest documented superior type iron formations the ifs are near shore pure chemical sediments and shale normalized rare earth and yttrium distributions reysn exhibit positive lasn gdsn and ysn anomalies which are typical features of marine waters throughout the archean and proterozoic the marine origin of these samples is further supported by super chondritic y ho ratios average y ho 42 relative to older isua ifs 3 7 ga from greenland and younger kuruman ifs 2 5 ga also from south africa the pongola ifs are depleted in heavy rare earth elements hree and appear to record variations in solute fluxes related to sea level rise and fall sm nd isotopes were used to identify potential sediment and solute sources within pongola shales and ifs the nd t for pongola shales ranges from 2 7 to 4 2 and nd t values for the coeval iron formation samples range 1 9 to 4 3 are generally indistinguishable from those of the shales although two if samples display nd t as low as 8 1 and 10 9 the similarity in nd isotope signatures between the shale and iron formation suggests that mantle derived rey were not a significant nd source within the pongola depositional environment though the presence of positive eu anomalies in the if samples indicates that high t hydrothermal input did contribute to their rey signature isotopic mass balance calculations indicate that most 72 of the nd in these seawater precipitates was derived from continental sources if previous models of fe nd distributions in archean ifs are applied then the pongola ifs suggest that continental fluxes of fe to archean seawater were significantly greater than are generally considered

freshwater forcing of abrupt climate change during the last glaciation large millennial scale fluctuations of the southern margin of the north american laurentide ice sheet occurred during the last deglaciation when the margin was located between about 43 and 49 n fluctuations of the ice margin triggered episodic increases in the flux of freshwater to the north atlantic by rerouting continental runoff from the mississippi river drainage to the hudson or st lawrence rivers we found that periods of increased freshwater flow to the north atlantic occurred at the same time as reductions in the formation of north atlantic deep water thus providing a mechanism for observed climate variability that may be generally characteristic of times of intermediate global ice volume