the taphonomy and palaeoenvironmental implications of the small mammals from karain cave turkey the small mammal accumulations in the pleistocene deposits of karain cave are investigated to identify the predators and possible biases in the fossil assemblages seven small mammal assemblages are studied in chronological order from two chambers of the cave the main chamber e and the side chamber b the lowermost level within the whole sequence is proto charentien which corresponds to an early stage of the middle palaeolithic the main part of the material belongs to middle palaeolithic layers the most important aspect of the fossil record in the cave is the human occupation without any interruption through the pleistocene to holocene the small mammal fossil evidence in the cave denotes the presence of opportunistic predators throughout the sequence with one exception and these produce balanced samples of small mammal faunas in the habitat the lack of bias in the small mammal faunas allow the interpretation of local environments showing that partial steppe and arid conditions existed during deposition of the lowermost levels of the middle palaeolithic in karain cave and that these shifted into more temperate and wooded habitat in the upper levels evidence from the side chamber indicates some differences with a more open grassy environment in the mediterranean part of anatolia the temperate and moist conditions in the middle palaeolithic were superseded by more arid conditions in the upper palaeolithic followed by a decrease in steppe conditions during the epi palaeolithic period

p and t wave detection thresholds pn velocity estimate and detection of lower mantle and core p waves on ocean sound channel hydrophones at the mid atlantic ridge since 1999 six sound fixing and ranging sofar hydrophones have been moored along the mid atlantic ridge mar 15 35 n these hydrophones 8 bit data resolution are designed for long term monitoring of mar seismicity using the acoustic t waves of seafloor earthquakes the completeness level of the mar t wave earthquake catalog estimated from size frequency constraints is mb 3 0 a significant improvement in detection compared to the mb 4 6 completeness level estimated from national earthquake information center magnitude frequency data the hydrophones also detect the acoustic phase of converted upper mantle p arrivals from regional earthquakes at epicentral distances of 374 1771 km and from events as small as mb 3 6 these regional p waves are used to estimate a pn velocity of 8 0 0 1 km sec 1 along the east and west mar flanks an unexpected result was the identification of p arrivals from earthquakes outside the atlantic ocean basin the hydrophones detected p waves from global earthquakes with magnitudes of 5 8 8 3 at epicentral distances ranging from 29 6 to 167 2 examination of travel times suggests these teleseismic p waves constitute the suite of body wave arrivals from direct mantle p to outer and inner core reflected refracted phases the amplitudes of the teleseismic p waves also exhibit the typical solid earth wave field phenomena of a p shadow zone and caustic at d 144 these instruments offer a long term relatively low cost alternative to ocean bottom seismometers that allows for obser vation of pn velocities and mantle core phases arriving at normally inaccessible deep sea locations

empirical relationship of t wave energy and fault parameters of northeast pacific ocean earthquakes a total of 179 northeast pacific ocean earthquakes that occurred between 1992 1998 are used to investigate the relationship of t wave acoustic energy and earthquake fault parameters the moderate sized 3 7 mw 6 9 earthquakes were recorded by ocean hydrophones and had their source parameters estimated by land based seismic networks the acoustic energy release at the seafloor water interface of each earthquake was estimated by removing the signal attenuation along the propagation path and instrument gain from the hydrophone signal there appears to be a relationship where for a given magnitude earthquake t wave energy is lower for normal and reverse fault earthquakes than strike slip events a more detailed comparison indicates acoustic energy of the earthquake will often decrease as the component of dip slip motion increases these observations suggest fault parameter information is contained within the t wave signal packet

nondestructive continuous physical property measurements of core samples recovered from hole b taiwan chelungpu fault drilling project 1 the taiwan chelungpu fault drilling project was undertaken in 2002 to investigate the faulting mechanism of the 1999 mw 7 6 taiwan chi chi earthquake hole b penetrated the chelungpu fault and core samples were recovered from between 948 42 and 1352 60 m depth three major zones designated fzb1136 fault zone at 1136 m depth in hole b fzb1194 and fzb1243 were recognized in the core samples as active fault zones within the chelungpu fault nondestructive continuous physical property measurements conducted on all core samples revealed that the three major fault zones were characterized by low gamma ray attenuation gra densities and high magnetic susceptibilities extensive fracturing and cracks within the fault zones and or loss of atoms with high atomic number but not a measurement artifact might have caused the low gra densities whereas the high magnetic susceptibility values might have resulted from the formation of magnetic minerals from paramagnetic minerals by frictional heating minor fault zones were characterized by low gra densities and no change in magnetic susceptibility and the latter may indicate that these minor zones experienced relatively low frictional heating magnetic susceptibility in a fault zone may be key to the determination that frictional heating occurred during an earthquake on the fault

spatial and temporal distribution of seismicity along the northern mid atlantic ridge 15 35 n 1 a detailed investigation of the relationship between the spatial and temporal patterns of the seismic activity recorded by six autonomous hydrophones and the structure of the northern mid atlantic ridge between 15 and 35 n is presented two years of monitoring yielded a total of 3485 hydroacoustically detected events within the array recorded by four or more hydrophones the seismically active zone extends 20 km to either side of the ridge axis consistent with earlier results from studies of fault morphology along the axis hydrophone recorded activity shows important variations areas with intense and persistent seismic activity stripes stand in sharp contrast to areas that lack seismicity gaps the regions of persistent activity are a new observation at mid ocean ridges in general the patterns of seismically active inactive regions are also recognized in the 28 year teleseismic record implying that these patterns are maintained at timescales between a few years and a few decades we find no simple relationship between individual segment variables e g length or trend of the segment maximum offset of discontinuities or along axis change in mantle bouguer anomaly mba and water depths and number of hydrophone recorded events there does appear to be a correlation between axial thermal structure and seismicity regions of low and high numbers of events would thus correspond to thinner hotter and thicker colder lithosphere respectively seismicity may reflect thermal structure at short timescales decadal or longer while relief and inferred crustal thickness may integrate this structure over longer periods of time order of 1 myr

pyrite alteration and neoformed magnetic minerals in the fault zone of the chi chi earthquake mw7 6 1999 evidence for frictional heating and co seismic fluids 1 during an earthquake physical and chemical transformations lead to alteration and formation of minerals in the gouge layer altered and neoformed minerals can be used as tracers of some earthquake processes in this study we investigate pyrite and magnetic minerals within the host chinshui siltstone and the 16 cm thick gouge this gouge hosts the principal slip zone of chi chi earthquake mw7 6 1999 in the chinshui siltstone pyrite framboids of various sizes and euhedral pyrite are observed the magnetic mineral assemblage comprises stoichiometric magnetite greigite and fine grained pyrrhotite the pyrite content is generally reduced in the gouge compared to the wall rock the magnetic mineral assemblage in the gouge consists of goethite pyrrhotite and partially oxidized magnetite the pyrrhotite goethite and some magnetite are neoformed pyrrhotite likely formed from high temperature decomposition of pyrite 500 c generated during co seismic slip of repeated earthquakes goethite is inferred to have formed from hot aqueous co seismic fluid 350 c in association with the 1999 chi chi event elevated fluid temperatures can also explain the partial alteration of magnetite and the retrograde alteration of some pyrrhotite to pyrite we suggest that characterization of neoformed magnetic minerals can provide important information for studying earthquake slip zones in sediment derived fault gouge

rock magnetic proxies of climate change in the loess palaeosol sequences of the western loess plateau of china summary results of the first detailed study of the climate proxy record in the loess palaeosol sequence at xining one of the few palaeoclimate sites in the currently arid western loess plateau of china illustrate the importance of making many types of rockmagnetic measurements other than susceptibility a multiparameter approach yielded confirmation that here as elsewhere in the loess plateau the susceptibility enhancement in palaeosols was caused primarily by ultrafine magnetite and maghaemite nevertheless magnetic enhancement was caused not exclusively by changes in relative grain size but also by variations in concentration and mineralogy of the magnetic fraction the effects of concentration variations were removed through normalization of susceptibility and anhysteretic remanence with saturation magnetization and saturation remanence respectively the resulting signal was ascribed more confidently to variation in magnetic grain size which in turn was interpreted as a better proxy of pedogenesis than simple susceptibility variations in magnetic mineralogy were also determined to constrain interpretations further the data were then used to discuss climate history at xining finally results from xining were compared with other western sites and contrasted with eastern sites in summary 1 data is presented from a new loess plateau site which also appears to yield a global climate signal 2 a demonstration is made of a more rock magnetically robust way to separate concentration composition and grain size controls on susceptibility and other magnetic parameters and 3 models are provided for inter regional comparisons of palaeoclimate proxy records

grain size dependence of the magnetic behavior of pyrrhotite during its low temperature transition at 34 k the grain size dependent behavior of pyrrhotite during a magnetic lt transition at 34 k is suitable for granulometric purposes cycling down to liquid helium temperature suppresses soft md jrs more than hard sd jrs so that it may be effective in removing soft secondary nrm components the domain structure of large pyrrhotite grains changes from md at room temperature to sd or psd below the lt transition

coseismic fluid rock interactions at high temperatures in the chelungpu fault chemical and isotopic variations in crushed material along the chelungpu fault in taiwan are suggestive of interactions at high temperatures with coseismically generated aqueous fluids high fluid pressures along the fault zone during the magnitude 7 6 chi chi earthquake in 1999 could have reduced friction and fault strength aqueous fluids are thought to have an essential role in faulting and the dynamic propagation of earthquake rupture fluid overpressure can affect earthquake nucleation1 2 and in a process termed thermal pressurization pore fluid pressure produced by frictional heating can reduce the effective normal stress acting on the fault surface3 4 5 this may lead to a marked reduction in fault strength during slip however the coseismic presence of fluids within slip zones and the role of fluids in dynamic fault weakening is still a matter of debate here we present compositions of major and trace elements as well as isotope ratios of core samples representing relatively undamaged as well as very fine grained deformed material from three active zones of the chelungpu fault taiwan depth profiles across the most intensely sheared bands that range in thickness from 2 15 cm exhibit sharp compositional peaks of fluid mobile elements and of strontium isotopes we suggest that high temperature fluids 350 c derived from heating of sediment pore fluids during the earthquake interacted with material within the fault zone and mobilized the elements the coseismic presence of high temperature fluids under conditions of low hydraulic diffusivity6 within the fault zone is favourable for thermal pressurization this effect may have caused a dynamic decrease of friction along the chelungpu fault during the 1999 magnitude 7 6 chi chi earthquake

changes in remanence coercivity and domain state at low temperature in magnetite abstract submicron magnetite crystals with mean sizes of 0 037 0 10 and 0 22 m undergo major changes in hysteresis properties and domain states in crossing the verwey transition t v 120 k the 0 037 m crystals are single domain sd both in the cubic phase at room temperature t 0 and in the monoclinic phase below t v the 0 10 and 0 22 m crystals have a mixture of sd and two domain 2d states at room temperature t 0 but mainly sd structures below t v in agreement with micromagnetic calculations coercive force h c increases on cooling through t v by a factor 3 5 in the submicron magnetites and 40 in a 1 3 mm single crystal because of the high crystalline anisotropy and magnetostriction of monoclinic magnetite as a result domain walls and sd moments are so effectively pinned below t v that all remanence variations in warming or cooling are reversible however between 100 k and t 0 remanence behavior is variable saturation remanence sirm produced in monoclinic magnetite at 5 k drops by 70 100 in warming across t v with minor recovery in cooling back through t v ultimate levels at 5 k of 23 37 for the submicron crystals and 3 for the 1 3 mm crystal in contrast sirm produced in the cubic phase at 300 k decreases 5 35 submicron or 95 1 3 mm during cooling from 300 to 120 k due to continuous re equilibration of domain walls but there is little further change in cooling through t v itself however the submicron magnetites lose a further 5 15 of their remanence when reheated through t v these irreversible changes in cycling across t v and the amounts of the changes have potential value in determining submicron magnetite grain sizes the irreversibility is mainly caused by 2d sd transformations on cooling through t v which preserve or enhance remanence while sd 2d transformations on warming through t v cause remanence to demagnetize

an earthquake slip zone is a magnetic recorder during an earthquake the physical and the chemical transformations along a slip zone lead to an intense deformation within the gouge layer of a mature fault zone because the gouge contains ferromagnetic minerals it has the capacity to behave as a magnetic recorder during an earthquake this constitutes a conceivable way to identify earthquakes slip zones in this paper we investigate the magnetic record of the chelungpu fault gouge that hosts the principal slip zone of the chi chi earthquake mw 7 6 1999 taiwan using taiwan chelungpu fault drilling project core samples rock magnetic investigation pinpoints the location of the chi chi mm thick principal slip zone within the 16 cm thick gouge at 1 km depth a modern magnetic dipole of earth magnetic field is recovered throughout this gouge but not in the wall rocks nor in the two other adjacent fault zones this magnetic record resides essentially in two magnetic minerals magnetite in the principal slip zone and neoformed goethite elsewhere in the gouge we propose a model where magnetic record 1 is preserved during inter seismic time 2 is erased during co seismic time and 3 is imprinted during post seismic time when fluids cooled down we suggest that the identification of a stable magnetic record carried by neoformed goethite may be a signature of friction heating process in seismic slip zone

time clustering behavior of spreading center seismicity between 15 and 35 n on the mid atlantic ridge observations from hydroacoustic monitoring abstract an earthquake catalog derived from the detection of seismically generated t waves is used to study the time clustering behavior of moderate size 3 0 m earthquakes between 15 and 35 n along the mid atlantic ridge mar within this region the distribution of inter event times is consistent with a non periodic non random clustered process the highest degrees of clustering are associated temporally with large mainshock aftershock sequences however some swarm like activity also is evident temporal fluctuations characterized by a power spectral density p f that decays as 1 f are present within the time sequence with ranging from 0 12 to 0 55 for different regions of the spreading axis this behavior is negligible at time scales less than 5 103 s and earthquake occurrence becomes less clustered smaller as increasing size thresholds are applied to the catalog a power law size frequency scaling for mid atlantic ridge earthquakes also can be demonstrated using the distribution of acoustic magnitudes or source levels although fractal seismic behavior has been linked to the structure of the underlying fault population in other environments power law fault size distributions have not been observed widely in the mid ocean ridge setting

low temperature magnetic behaviour near 35 k in unmetamorphosed claystones summary there is growing evidence that the magnetic assemblage of claystones illustrated by low temperature magnetic transitions at 120 k and 35 k may be representative of the peak burial temperature in the so called oil window 60 150 c in previous studies it was proposed that this magnetic assemblage is characterized by fine grained pyrrhotite fe7s8 and magnetite fe3o4 however evidence of pyrrhotite was not so obvious and the magnetic transition near 35 k of fine grained pyrrhotite has similarities with those of siderite feco3 or rhodochrosite mnco3 here we propose some diagnostic tests to distinct 50 k behaviours by studying claystones from netherlands borehole and borneo prism that experienced different peak burial temperatures we perform magnetic susceptibility temperature dependency of sirm zfc rt sirm and field cooled hysteresis loops on cooling of rt sirm 300 k to 10 k we applied a magnetic field of 5 t to enhance neel type magnetic transition it is found that our samples can be classified in two categories based on the shape of the rt sirm curve one displaying an abrupt break in slope in the remanence at 30 k called n behaviour and the other one characterized by a progressive increase of the remanent magnetization by 80 k named p behaviour the first category contains essentially magnetite and fe mn carbonates the second one magnetite and probably iron sulphides

palynological analysis of the late early pleistocene sediments from queque cave in guangxi south china abstract palynomorphs extracted from the sediments in queque cave of the late early pleistocene in chongzuo guangxi zhuang autonomous region were investigated to reconstruct the paleoenvironment in the study area while the sediments are pollen poor they are sufficiently productive to carry out a paleoenvironmental analysis the source vegetation reflected by the palynomorphs from the unfossiliferous layer was temperate to warm temperate deciduous and evergreen broadleaved forest while it was warm temperate to subtropical deciduous and evergreen broadleaved forest from the mammalian horizons climatic parameters obtained using the coexistence approach indicate that the unfossiliferous layer mat 11 3 15 4 c map 601 1 1076 1 mm was cooler and drier than that from the mammal bearing layers mat 12 6 18 6 c map 784 7 1523 1 mm

assemblage data and bone and teeth modifications as an aid to paleoenvironmental interpretations of the open air pleistocene site of tighenif algeria abstract variations in the proportions of the various groups of rodentia collected from eight stratigraphic levels at tighenif had previously been interpreted as representing environmental climatic changes however the processes involved in the formation of assemblages are still not well understood examination of fragmentation crystallinity and chemical composition of fossil bones and teeth compared to recent samples shows that a possible explanation for the variations in frequencies is the differential preservation of skeletal remains thus the evaluation of postmortem effects is essential in determining the accuracy of the fossil record the abundance and composition of remains are governed by the complex interaction of many factors as indicated by actualistic studies direct deductions from fauna lists must be avoided as much as possible

quantitative modeling of the newly formed magnetic minerals in the fault gouge of 1999 chi chi earthquake mw 7 6 taiwan when an earthquake occurs magnetic minerals are formed in the gouge under the combined action of frictional heating and fluid generally the gouge is altered and a detailed analysis of neoformed minerals is difficult the taiwan chelungpu fault drilling project provided continuous records of the active chelungpu fault gouges by analyzing the magnetic parameters along the 16 cm thick gouge which houses the principal slip zone of the 1999 chi chi earthquake mw 7 6 we observed a 4 cm shift between the maximum of magnetic susceptibility and the maximum of remanence the maximum magnetic susceptibility is localized along the principal slip zone the main identified magnetic minerals are magnetite and goethite which have very different magnetic parameters we propose that the maximum of the concentration of magnetite and goethite corresponds to the maximum of magnetic susceptibility and remanence respectively by modeling the concentration of these two magnetic minerals we explain satisfactorily the profiles of magnetic susceptibility and remanence this quantitative modeling indicates that 200 ppmv of magnetite formed in the principal slip zone and its main contact area similarly 1 of goethite is formed in the center of the gouge where the fluids are more enriched in iron we propose that the magnetite and goethite are formed and altered during seismic cycles key points investigate the magnetic mineral assemblage in the chi chi fault gougeclarify the distribution of goethite and magnetite in the gougepropose a model for goethite and magnetite distributions within the gouge

taphonomy of micromammals from cave deposits at kabwe broken hill and twin rivers in central zambia samples of middle pleistocene micromammals from cave deposits at kabwe broken hill and twin rivers in zambia were analysed according to andrews s 1990 methods in addition behavioural and ecological data relating to possible predator species were examined for corrobation or contradiction of the mechanical evidence interpretation of the kabwe sample is complicated by its unknown history since recovery and the possibility that the paucity of cranial remains results from their selective post recovery removal from the sample however the combined evidence suggests that it was collected by barn owls whereas the twin rivers material perhaps accumulated at a spotted eagle owl nest site

monitoring pacific ocean seismicity from an autonomous hydrophone array since may 1996 an array of autonomous hydrophone moorings has been continuously deployed in the eastern equatorial pacific to provide long term monitoring of seismic activity including low level volcanic signals along the east pacific rise between 20 n and 20 s and the galapagos ridge the instruments and moorings were designed to continuously record low frequency acoustic energy in the sofar channel for extended periods and produce results comparable to those previously derived by using the u s navy sound surveillance system sosus in the northeast pacific the technology and methodology developed for this experiment including instrument design mooring configuration analysis software location algorithms with an analysis of errors and a predicted error field are described in detail volcanic activity is observed throughout the pacific along with seismicity along transform faults subduction zones and intraplate regions comparison data sets indicate detection thresholds and accuracy better than the land networks for open ocean areas and results comparable to or better than sosus volcanic seismicity along the fast spreading east pacific rise appears similar to documented examples in the northeast pacific but with much shorter durations one example from the intermediate spreading galapagos ridge is comparable to northeast pacific examples and several episodes of activity were observed in the wilkes transform fault zone a site of continuing off axis seismicity is located near 18 s and 116 w isolated intraplate earthquakes are observed throughout the study area earthquake information from this experiment and future observations will be provided through the world wide web and earthquake data centers

modal scattering a key to understanding oceanic t waves the excitation mechanism of oceanic t waves has been a puzzle for almost fifty years with refraction from a sloping seafloor and seafloor scattering as two of the most commonly invoked mechanisms by representing the earthquake source field as a normal mode sum it can be seen that both mechanisms are very closely related strict modal orthogonality prohibits the existence of t waves in a laterally homogeneous semi infinite half space or radially symmetric sphere as energy cannot be transferred from one mode to another in an homogeneous medium deterministic non planar bathymetry random boundary roughness upper crustal heterogeneity or a combination of these provides a physical mechanism to break the strict orthogonality we show that modal scattering from the rough seabottom in the epicentral region converts energy from the directly excited ocean crustal water column modes to the propagating acoustic modes comprising the oceanic t wave submarine earthquake fault orientation also appears to be reflected in the t wave excitation

a new oil window indicator the magnetic assemblage of claystones from the baffin bay volcanic margin greenland identifying independent parameters to bracket the oil window in sedimentary basins is of first importance for petroleum exploration we investigate the magnetic assemblage of cretaceous claystones collected from the western volcanic margin of greenland these claystones experienced low grade burial 300 k properties of isothermal remanent magnetization the magnetic assemblage of immature claystones lower ro resides in goethite greigite and some magnetite the magnetic assemblage of immature to early mature claystones higher ro resides in stoichiometric magnetite and fine grained pyrrhotite by comparing these results with those from claystones from the paris basin france and the jura mountains switzerland we suggest the existence of similar mechanisms for the formation of magnetic minerals during burial if confirmed by further studies the magnetic assemblage of claystones may be diagnostic of oil windows

low temperature magnetic properties of siderite and magnetite in marine sediments low temperature magnetic techniques provide useful tools to detect the presence of magnetite and pyrrhotite in sediments through identification of their low temperature transitions to determine the amount of ultrafine grained superparamagnetic material in sediments and can potentially detect the presence of certain types of magnetotactic bacteria application of these types of experiments to nannofossil chalks from beneath the barbados accretionary prism led to some unusual results which are attributed to the presence of siderite thermal demagnetization of low temperature remanence after cooling in zero field and in a 2 5 t field both displayed large remanence losses from 20 k to 40 k below 40 k the magnetization of the chalks was much higher in the field cooled experiments than in the zero field cooled experiments low temperature hysteresis experiments made after cooling in a 2 5 t field displayed offsets in magnetization parallel to the direction of the initial applied field when measured below 40 k the offset loops can be due to either an exchange anisotropy between siderite and magnetite phases in the sediments a defect moment in the siderites or a canted moment in the siderites apparent similarity between the low temperature thermal demagnetization results from these siderite bearing sediments pure siderite and pure rhodochrosite samples and the well known 34 k transition in pyrrhotite should lead to caution in identification of pyrrhotite in marine sediments based on low temperature remanence studies alone

diagenetic alterations of micromammal fossil bones from olduvai bed i of the lower pleistocene sequence at olduvai gorge tanzania abstract analyses of the organic and inorganic components of various small mammal fossil bones from nine stratigraphic levels of bed i olduvai gorge tanzania spanning 100 000 years show some differences that relate to environmental factors but not to chronological sequence all fossil bones are compositionally altered relative to modern counterparts with the organic components both extensively lost and chemically modified and all display large crystallinity changes each of the stratigraphic levels has distinctive subtle features but with greatest differences recorded from the flkzinj and flkn5 6 levels from observations of post mortem features including modified bone morphology and taphonomic alterations to bone surfaces together with the compositional and structural differences it is concluded that localized differences in burial diagenesis existed and that predation was a contributory factor to the overall diagenetic process these results illustrate the importance and future potential of a combined taphonomic and diagenetic approach to understanding the processes involved in bone diagenesis

toward a new 250 c pyrrhotite magnetite geothermometer for claystones abstract we investigate the effects of burial and moderate experimental heating on claystones from three regions with different degrees of maturation immature burial temperature 40 c of bure callovo oxfordian claystones in the basin of paris france early mature burial temperature 85 c of opalinus lower dogger claystones from the mont terri anticline in front of the jura fold belt switzerland and mature to overmature burial temperature 7 s 8 the p transition is also detected in early mature to mature opalinus and chartreuse claystones we conduct additional experimental heating of natural opalinus claystones one set of experiments is referred to as short term heating 1 h from 100 c to 200 c it is dedicated to an investigation of the effect of short lived heating processes in geology a second set of heating experiments is designed to approach burial conditions using a gold capsule in burial like experiments we heated opalinus claystones from 150 c to 250 c for several weeks under a pressure of 100 mpa in both experiments we observe a correlative diminution of the pyrrhotite signature at 35 k with increasing temperature we interpret this trend as the appearance of magnetite we derive a parameter pm from the warming curve of a saturated isothermal remanent magnetization acquired at 10 k zfc we report on a consistent evolution of pm with temperature in the range of 40 c to 250 c including natural samples heated samples at 95 c and burial like heated samples pm first increases between 40 c up to 85 c implying that pyrrhotite gradually dominates the magnetic assemblage at low temperature for temperatures above 85 c pm decreases up to 250 c implying that the formation of magnetite gradually overshadows the magnetic input of pyrrhotite pm values obtained from mature to overmature claystones from the chartreuse are lower than the pm values obtained from the burial like heated opalinus claystones suggesting that the formation of magnetite is driven by kinetics the continuous trend of the pm parameter suggests that the magnetic properties of pyrrhotite magnetite claystones can be used to infer paleo temperatures and we propose to name this geothermometer mageval

magnetic transition at 30 34 kelvin in pyrrhotite insight into a widespread occurrence of this mineral in rocks abstract a characteristic magnetic transition at 30 34 k is shown to provide a powerful tool for the identification of pyrrhotite with concentration down to 10 ppm through the same low temperature techniques as applied to magnetite and hematite extended down to liquid helium temperature a review of rock magnetic and petrological data on pyrrhotite suggests that this mineral should be considered as a major carrier of paleomatnetic signals unblocking temperature up to 350 c and extreme resistance against af may be encountered in fine grained pyrrhotite

high magnetic susceptibility of fault gouge within taiwan chelungpu fault nondestructive continuous measurements of physical and chemical properties in fault rocks recovered from hole b tcdp 1 the taiwan chelungpu fault drilling project tcdp was undertaken in 2002 to investigate the faulting mechanism of the 1999 taiwan chi chi earthquake hole b penetrated the chelungpu fault and recovered core samples from between 948 42 m and 1352 60 m depth three zones marked 1136mfz 1194mfz and 1243mfz were recognized in the core samples as active fault zones within the chelungpu fault multi sensor core logger measurements revealed lower densities and higher magnetic susceptibilities within the black gouge zones in all three fault zones even though the fault zone that slipped during the 1999 earthquake has not been identified higher magnetic susceptibilities indicate that frictional heating has taken place in the chelungpu fault

the environment in the caucasus in the upper paleolithic late pleistocene evidence from the small mammals from dzudzuana cave georgia abstract the mis 3 2 transition denekamp interstadial and beginning of the lgm is a crucial point in time for understanding adaptation of modern humans to climate the southern caucasus is a unique place to study human ecology within this time period because it served as a refugium during the last glacial maximum lgm and thus allows us to study how human populations responded to the climatic shifts during the last glacial this study presents the results of the paleoecological analysis of dzudzuana cave during the mis 3 2 transition using small mammal community structure as a proxy for paleoenvironment of the four units in dzudzuana units a through d unit c divided into subunits c5 to c1 has been dated to 27 24 ka cal bp and the mis 3 2 transition thus unit c allows for a diachronic analysis throughout this important time period small mammals were found primarily in subunit c2 and c1 analysis of the small mammal assemblages of dzudzuana subunits c2 and c1 confirm the paleoecological reconstruction obtained from macrobotanical remains and suggest a refugium habitat during the last phase of mis 3 and the onset of the lgm comparison with a contemporaneous site in the region satsurblia suggests a high spatial temporal mosaic habitat in the region small refugium areas within the rioni river valley and its tributaries that enjoyed ameliorated climatic conditions and proximity to water resources may have promoted local human habitation furthermore results suggest that the small mammal assemblages of dzudzuana are non analogue communities typical of european denekamp assemblages and provide a new datum point for the faunal remains during this time period

aftershock sequences in the mid ocean ridge environment an analysis using hydroacoustic data abstract hydroacoustic data from autonomous arrays and the u s navy s sound surveillance system sosus provide an opportunity to examine the temporal and spatial properties of seismicity along portions of the slow spreading mid atlantic ridge mar intermediate spreading juan de fuca ridge jdfr and fast spreading east pacific rise epr aftershock and foreshock events are selected from the hydroacoustic earthquake catalog using single link cluster slc analysis with a combined space time metric in the regions examined hydroacoustic data improve the completeness level of the earthquake catalog by 1 5 2 0 orders of magnitude allowing the decay constant p of the modified omori law mol to be determined for individual sequences a non parametric goodness of fit test indicates six of the seven sequences examined are described well by a mol model the p values obtained for individual ridge and transform sequences using hydroacoustic data are larger than that previously estimated from the analysis of a stacked sequence generated from teleseismic data for three sequences along the siqueiros discovery and western blanco transforms p values are estimated to be 0 94 1 29 the spatial distribution of aftershocks suggests that the mainshock rupture is constrained by intra transform spreading centers at these locations an aftershock sequence following a 7 1 m s thrust event near the northern edge of the easter microplate exhibits p 1 02 0 11 within the sequence aftershocks are located to the north of a large topographic ridge which may represent the surface expression of the shallow dipping fault that ruptured during the mainshock two aftershock sequences near 24 25 n and 16 35 n on the mar exhibit higher p values 1 74 0 23 and 2 37 1 65 although the latter estimate is not well constrained because of the small number of aftershocks larger p values along the ridge crest might reflect a hotter thermal regime in this setting additional monitoring however will be needed to determine if p value differences between the ridge and transform sequences are robust a 1999 sequence on the endeavour segment of the jdfr which has been correlated with changes in the hydrothermal system is described poorly by the mol model the failure of the mol model the anomalously large number of earthquakes within the sequence and absence of a clearly dominant mainshock are inconsistent with aftershock activity and the simple tectonic origin that has been proposed previously for this sequence

strain indicators and magnetic fabric in intraplate fault zones case study of daroca thrust iberian chain spain abstract anisotropy of magnetic susceptibility ams has been applied to the study of shallow fault zones although interpretation of the results requires establishing clear relationships between petrofabric and magnetic features magnetic behaviour of fault rocks and an extensive knowledge of p t conditions in this work we demonstrate that magnetic methods can be applied to the study of heterogeneous fault zones provided that a series of requisites are met a major fault zone within the iberian plate daroca thrust showing transpressional movements during cenozoic time was chosen for this purpose because of the exceptional outcrops of fault gouge and microbreccia and its relevance within the context of the northeastern iberian plate magnetic fabrics were analysed and the results were compared with foliation and s c structures measured within the fault zone clay mineral assemblages suggest maximum burial depths shallower than 2 km

energy taken up by co seismic chemical reactions during a large earthquake an example from the 1999 taiwan chi chi earthquake 1 frictional heat in a fault zone during earthquake slip transiently induces chemical reactions that may use energy released during the earthquake we estimated the energy used by such reactions ec by a numerical analysis incorporating frictional heat thermal diffusion chemical kinetics and energy conservation and found that ec has an auto feedback effect that inhibits temperature rise in fault zone during the 1999 taiwan chi chi earthquake estimated ec was 0 43 mj m2 corresponding to 0 79 of the frictional heat generated this low percentage probably reflects the low initial concentrations of reactive materials however in the case of a fault with abundant reactive materials ec could reach 50 of the frictional heat and the auto feedback effect could be large at this case ec is a nonnegligible component on earthquake energy budget and can affect fault mechanics

spectral characteristics of high frequency pn sn phases in the western pacific pn and sn phases from 25 selected earthquakes recorded since july of 1979 on ocean bottom hydrophones near wake island are used to complement and extend prior investigations of high frequency pn sn spectra in the western pacific at a distance of about 18 sup 0 approx 2000 km frequencies for pn and sn are as high as 30 and 35 hz respectively at a distance of about 30 sup 0 approx 3300 km as high as 15 and 20 hz respectively pn phases lose their high frequency energy more rapidly than sn phases do yet pn wavetrains are much longer than sn wavetrains pn wavetrains of longer duration more energy and higher frequencies are found for travel paths primarily in the northwestern pacific basin than for travel paths across the transition zone from the shallow ontong java plateau to the deep northwestern pacific basin sn phases are extremely weak or absent for travel paths crossing this transition zone from the shallower ontong java plateau to the deeper northwestern pacific basin whereas sn phases are well recorded for travel paths crossing the transition zone in the opposite direction although normal mantle refracted p phases are well recorded beyond about 21 sup 0 approx 2300 km available data indicatemore that detectable normal mantle refracted p phases may not exist at distances from about 17 sup 0 to 21 sup 0 less

crustal structure of the mid atlantic ridge at 23 n from seismic refraction studies an explosive seismic refraction experiment using four ocean bottom hydrophone receivers was carried out along a 120 km long section of the mid atlantic ridge mar median valley at latitude 23 n immediately south of its intersection with the kane fracture zone the data are interpreted in terms of laterally homogeneous horizontally layered structures using travel time inversion and synthetic seismogram modeling techniques these solutions are combined using two dimensional ray tracing to produce a single model defining the major along axis structural changes occurring beneath this section of the median valley with the exception of slightly low layer 3 velocities the crust beneath several tens of kilometers of the mar median valley has all the characteristics of simple mature ocean crust including a well defined moho transition zone 8 km s upper mantle velocities and a total crustal thickness of 6 7 km no evidence is found for the presence of a steady state axial magma chamber in the crust or upper mantle and the excellent propagation characteristics and orderly amplitude versus range relationships imply the existence of a considerable degree of lateral homogeneity beneath the median valley over distances of several tens of kilometers along axis we infer from these observations that the basic seismic characteristics of the ocean crust are frozen in in a time period less than that separating the major volcanic injection events 10 000 50 000 years by hydrothermal circulation penetrating to the base of the crust along the 100 km long ridge segment studied here two major along axis structural changes occur the first is a 10 to 15 km wide along axis zone of lowered velocities in the lower crust centered beneath a major along axis topographic high this is interpreted to be the remnants of the most recent phase of injection that has temporarily left behind it a region of elevated temperatures and pervasive cracking and thus reduced velocities the second occurs abruptly at latitude 23 15 n and is accompanied by both a major change in rift valley and crestal mountain morphology and the apparent noncoincidence of the median valley and central magnetic anomaly north of this boundary the 30 km long ridge segment that abuts the kane fracture zone has a crustal thickness of 4 5 km and no distinctive layering to produce the characteristic amplitude patterns that typify mature oceanic crust interpretation of the cause of this structural change is uncertain but may be related to local tectonic events perhaps a recent 10 to 20 km ridge jump to the east

p wave detection thresholds pn velocity estimates and t wave location uncertainty from oceanic hydrophones p wave arrivals recorded by the u s navy s sound surveillance system sosus hydrophone arrays were used to estimate earthquake detection thresholds and pn velocities in the northeast pacific ocean the navy hydrophones have been used successfully to detect and locate oceanic earthquakes using their waterborne acoustic tertiary t waves however use of these hydrophones for seismic body wave detection allows regional seismic analyses to be extended to the oceanic environment the p wave detection threshold of the sosus hydrophones was quantified using the epicentral distance and magnitude of 250 northeast pacific ocean earthquakes earthquakes with body wave magnitudes as low as 2 have detectable p wave arrivals at epicentral distances of 500 km earthquakes with mb between 3 5 and 5 were detected 50 of the time at distances of 100 1500 km while events with mb 5 were all detected even out to distances of 1000 1500 km both p and t wave hydrophone arrival times were used to estimate the epicenters of 100 earthquakes the peak amplitude of the t wave coda and the onset of the p wave were used as the earthquake arrival times to estimate event locations t wave arrival time residuals have a gaussian distribution with zero mean which implies that using t wave peak amplitude is consistent with using the p wave onset as the arrival time there are typically 6 stations used to derive a t wave based location hence location error ellipses are not well constrained a monte carlo technique was employed to estimate t wave event location uncertainty t wave locations have error bars of 1 km in latitude and longitude when 3 hydrophones are used for a location estimate the detected p wave arrivals and earthquake locations were used to measure pn velocities pn velocity values of 7 9 0 1 and 8 0 0 1 km s were found for the pacific and juan de fuca plates respectively a pn velocity of 7 5 0 1 km s was measured for rays traveling northward from the mendocino triple junction along the cascadia subduction zone a pn velocity of 7 7 0 3 km s was estimated for ray paths originating onshore western north america and traveling to the offshore hydrophones

small mammal taphonomy of gran dolina atapuerca burgos spain abstract the middle pleistocene sequence at the atapuerca burgos complex of caves is most completely represented at gran dolina eleven stratigraphic units are distinguished seven of which contain abundant small mammal fossils these seven units are analysed in order to determine the taphonomic processes present during the accumulation of their faunal remains the fossil bones are extensively broken both before and after burial fossils from six of the units show evidence of localized pre depositional acid corrosion which occurred both before and after breakage in the upper levels there is also evidence of post depositional corrosion both from alkaline and from acid environments of deposition and in the top level some fossil bones also show evidence of weathering and root marks images of these modifications by means of the scanning electron microscope and their comparison with a large comparative data base of recent modifications from known causal agents permits the identification of the agents responsible for many of the modifications and consequently the reconstruction of the sequence of events leading to the accumulation and preservation of the fossil assemblages predators are implicated for some of the breakage and all of the pre depositional corrosion which is the result of digestion in the predators stomachs in all cases the category of predator can be identified and at three stratigraphic levels the actual species can be identified with moderate degrees of reliability post depositional corrosion is linked with observations on local acidity alkalinity of different levels and the incidence of weathering is linked with evidence for roof collapse over parts of the cave taking account of the effects of these processes particularly the selectivity resulting from predator hunting methods allows estimates to be made of the degree of bias in the faunal composition and the palaeoecology thereby indicated

a taphonomic investigation of small vertebrate accumulations produced by the snowy owl bubo scandiacus and its implications for fossil studies abstract the action of predators such as diurnal raptors owls mammals or humans influence the nature of small vertebrate fossil assemblages but currently their taphonomic features are still poorly understood in this study we investigate the taphonomic signature of the snowy owl bubo scandiacus based on an analysis of pellets collected at breeding sites located in greenland and the canadian arctic this taxon is widely distributed through the north hemisphere and was an important predator in pleistocene times taphonomic parameters suggest that contrary to previous assumptions b scandiacus produces on average moderate digestion of incisors molars and post cranial elements and should be classed as a category 3 or category 3 4 predator according to the terminology established by andrews significant inter site variability was observed for some of the damage considered in particular digestion on incisors and a key finding is that variability and the associated statistical confidence intervals are crucial notions that should be taken into account when assessing taphonomical features in order to reliably identify the potential predator s responsible for small vertebrate fossil accumulations

evidence for fault lubrication during the 1999 chi chi taiwan earthquake mw7 6 the ground motion data of the 1999 chi chi taiwan earthquake exhibit a striking difference in frequency content between the north and south portions of the rupture zone in the north the ground motion is dominated by large low frequency displacements with relatively small high frequency accelerations the pattern is opposite in the south with smaller displacements and larger accelerations we analyze the fault dynamics in light of a fault lubrication mechanism using near field seismograms and a detailed rupture model the fault zone contains viscous material e g gouge in which pressure increases following the reynolds lubrication equation when the displacement exceeds a threshold lubrication pressure becomes high enough to widen the gap thereby reducing the area of asperity contact with less asperity contact the fault slips more smoothly suppressing high frequency radiation

holocene environmental change in the eastern snake river plain of idaho usa as inferred from stable isotope analyses of small mammals abstract previous research on the small mammal population recovered from archeological excavations at the wasden site in southeastern idaho suggests that changing frequency distributions through time represent a shift in climate during the early holocene from a cooler wetter regime to a warmer drier one this conclusion was re evaluated using stable carbon and nitrogen isotope analyses of bone collagen from the three species of small mammals examined in the earlier studies pocket gophers thomomys talpoides pygmy rabbits brachylagus idahoensis and ground squirrels spermophilus townsendii resulting carbon and nitrogen isotopic values are consistent with known differences in feeding ecology suggesting high fidelity as proxies for past vegetation and thus climate regimes patterns of 15 n enrichment and increased representation of c 4 cam vegetation observed in the pocket gophers and to a lesser extent ground squirrels suggests increasing warmth and or aridity from the early holocene until 7000 cal yr bp thus supporting previous hypotheses of climate change on the eastern snake river plain the results highlight the potential contribution of such studies for archeological research by providing additional proxies for environmental conditions that bear on paleoecological adaptations to climatic change including past human use and occupation of the region

amphibian taphonomy and its application to the fossil record of dolina middle pleistocene atapuerca spain abstract the middle pleistocene site of atapuerca spain has many archaeological palaeontological and human remains in stratigraphic position amphibian remains are abundant and easily identifiable in many levels of the site we have investigated the taphonomy of the amphibian remains with the question to be answered being their source did the amphibians live and die inside the cave as occurs naturally nowadays or were their remains brought into the cave by predator activity or by other agents such as sedimentary motion water transport etc there is no reference source of taphonomic alterations on amphibian remains and we provide some basic background for this using two approaches one consisted of analyzing a collection of scats and pellets of known predators and based on the alterations and breakage present in the bones digested by each we produce a set of categories that will be an analytical tool to be applied to the fossil record secondly we have carried out several laboratory experiments to measure the effects of weathering and water transport on amphibian remains we subsequently analyzed the fossil amphibian remains from the middle pleistocene site of dolina atapuerca spain the results showed that the taphonomic processes observed in the atapuerca sequence of td4 td5 are the same and the amphibian remains at these levels entered the cave deposits in the scats of a mammalian predator this has been identified as a mustelid which is an opportunistic predator which would feed on amphibians from the surrounding environment