the composition and its impact on the methane sorption of lacustrine shales from the upper triassic yanchang formation ordos basin china abstract the organic geochemistry mineralogy and methane sorption of lacustrine shales of the upper triassic yanchang formation collected from the south eastern ordos basin were investigated to characterize them and clarify the effects of shale composition on their sorbed gas capacity these yanchang shales have recently been selected as a target area for shale gas exploration in typical terrestrial strata in china the two main sections of these shales containing type ii organic matters chang 7 and chang 9 have relatively high total organic carbon content toc of 2 10 the two shales also have similar mineralogies mainly comprising quartz clay minerals and feldspars both the chang 7 and chang 9 shales are generally in the oil window chang 9 is slightly more mature than chang 7 higher methane sorption capacity was observed for chang 9 than for chang 7 shales determined on a dried basis at 50 c methane sorption measurements were further performed on three samples from which the residual bitumen had been extracted and their corresponding kerogen fractions to gain insight into the effects of shale composition on methane sorption this was significantly higher in solvent extracted samples than in raw samples indicating that residual bitumen largely restricts methane sorption on such shales a positive correlation between the amount of clay minerals and methane sorption capacity of bulk rocks was evident suggesting that clay mineral content is relevant to methane sorption this result was also supported by the much higher methane sorption capacity of solvent extracted shales compared to the extracted kerogen from those shales when measured sorption data was normalized to toc values the effects of both residual bitumen and clay mineral on the methane sorption of bulk rocks have complicated the evaluation of methane sorption on organic matter in these mature shales

organic matter rich shales of china abstract organic matter rich shales are the main target rocks for unconventional oil and gas exploration and development across the world in china shale gas geological resources are estimated as approximately 110 1012 m3 with recoverable gas reserves of ca 20 1012 m3 recoverable shale oil reserves are estimated as ca 5 109 t a total 35 important organic matter rich shale units have been recognized from mesoproterozoic to cenozoic strata across the entire china these shales are categorized according to their origin under marine marine nonmarine transitional and lacustrine conditions shales of marine origin with ca 9 1012 m3 recoverable resources dominate china s potential in terms of total volume of organic carbon currently the most favorable marine shales for oil and gas exploration are found in the sichuan basin within the lower cambrian qiongzhusi formation and in the wufeng longmaxi formations of uppermost ordovician through lower silurian a fortuitous combination of of sea level variations of paleo productivity of tectonic activity causing development and migration of partially closed deep basin depocenters and of sediment accumulation rates controlled the extensive deposition and distribution of organic matter rich shales in these wufeng and longmaxi formations organic matter rich shales in marine nonmarine transitional facies associated with coal measures occur in north china within the carboniferous and permian and in south china within the permian these carboniferous permian organic matter rich shales are important source rocks for the gas fields in the ordos and sichuan basins abundant organic rich shales are also widely distributed within coal bearing clastics and coal measure shales of fluvial lacustrine and swamp facies in upper triassic to middle jurassic successions of many basins lacustrine organic rich shales were deposited during the permian through neogene in various freshwater to saline lake settings lacustrine organic matter rich shales are the main oil source rocks in the songliao bohai bay ordos and junggar basins lacustrine algae contributed to the rain of organic matter and the preservation of organic matter and distribution of organic rich shale was controlled by lake currents water depth and oxygen poor conditions with enhanced preservation when buried by turbidity currents algal blooms were partly induced by trace nutrients from volcanic ash falls in all of these lacustrine basins seawater intrusion into the freshwater lake of the songliao basin promoted some episodes of black shales saline lacustrine basins such as middle permian junggar basin contain organic rich dolomite mudstone that mainly formed during hot climate conditions when the lakes had high salinity and stratified water columns that deprived the bottom waters of oxygen thereby preserving massive amounts of organic matter laminated calcite rich mudstone in the saline lacustrine settings formed in more brackish waters under stable warm conditions and weak biological activity the modeling of the factors controlling the distribution of organic matter rich shales within china s basins is important for the exploration and development of unconventional oil and gas resources

lenticular shale fabrics resulting from intermittent erosion of water rich muds interpreting the rock record in the light of recent flume experiments lenticular lamination is a fabric that is known from shales of all ages but its origin and paleoenvironmental significance is poorly understood we have successfully reproduced this fabric in flume experiments beds of water rich mud were eroded in a flume and yielded sub millimeter to centimeter size fragments that can be transported in bedload for distances of ten kilometers or more upon redeposition and compaction these deposits have the same textural qualities as lenticular laminated shales from the rock record although accumulation of fecal pellets or abundant burrow tubes in a shale may produce comparable fabrics upon compaction these can be distinguished from erosion produced lenticular lamination via petrographic criteria lenticular lamination in shales that is due to deposition of water rich mud fragments most likely records intermittent erosion and transport of surficial muds by currents

thermal and tectonic history of the ordos basin china evidence from apatite fission track analysis vitrinite reflectance and k ar dating apatite fission track analysis vitrinite reflectance data and k ar dating of permian carboniferous and mesozoic core samples have been successfully integrated to reconstruct the thermal and tectonic history of the ordos basin china apatite fission track ages of carboniferous jurassic sedimentary rocks range between 3 and 137 ma and are significantly younger than the stratigraphic ages confined fission track lengths demonstrate exclusively mixed length distribution indicating complex thermal history the data suggest that the samples must have all experienced higher paleotemperatures in the past mean vitrinite reflectance values r0 of the triassic rocks range from 0 61 to 1 06 giving a high coalification gradient of 0 36 km and suggesting a high paleothermal gradient of 57 c km permian carboniferous rocks have ro values on the order of 1 0 3 0 and locally up to 4 0 6 0 some high r0 values coincide with positive gravity and magnetic anomalies k ar dating on permian triassi samples reveals distinct illitization at 170 160 ma during which a thermal event occurred due to subsurface magmatic intrusion related to the early yanshanian movement the petroleum source rocks of the upper triassic experienced peak temperatures ranging from 90 to 160 c corresponding to the oil window and permian carboniferous source rocks were heated to more than 150 c passing through and out of the gas window due to rapid uplift and erosion in response to the rise of the qinghai tibet plateau associated with the asia india collision and the himalayan orogeny cooling has taken place at least since approximately 23 ma the difference in the rate and amount of uplift between the eastern and western parts of the basin resulted in differential uplift and the present day s ructural pattern of the basin

burial of organic carbon and pyrite sulfur in sediments over phanerozoic time a new theory in present day marine sediments almost all of which are deposited in normal oxygenated seawater rates of burial of organic carbon c and pyrite sulfur s correlate positively and bear a constant ratio to one another c s 3 on a weight basis by contrast calculations based on the isotopic model of garrels and lerman 1981 indicate that at various times during the phanerozoic the worldwide burial ratio must have been considerably different than the present day value this ratio change is caused by the requirement that increases in the worldwide mass of organic carbon must be accompanied by equivalent decreases in the mass of sedimentary pyrite sulfur in order to maintain a roughly constant level of o2 in the atmosphere such apparently contradictory behavior can be explained if the locus of major organic carbon burial has shifted over time from normal marine environments as at present to non marine freshwater or to euxinic environments in the geologic past a shift to predominantly freshwater burial can help explain predicted high c s ratios in permo carboniferous sediments and a shift to euxinic environments can help explain predicted low c s ratios during the early paleozoic it is demonstrated that the three environments today exhibit distinguishably different average c s ratios

gas aerosol ash interaction in volcanic plumes new insights from surface analyses of fine ash particles the reactions occurring between gases aerosols and silicate ash particles in volcanic eruption plumes remain poorly understood despite the fact that they are at the origin of a range of volcanic environmental atmospheric and health effects in this study we apply x ray photoelectron spectroscopy xps a surface sensitive technique to determine the chemical composition of the nearsurface region 2 10 nm of nine ash samples collected from eight volcanoes in addition atomic force microscopy afm is used to image the nanometer scale surface structure of individual ash particles isolated from three samples we demonstrate that rapid acid dissolution of ash occurs within eruption plumes this process is favoured by the presence of fluoride and is believed to supply the cations involved in the deposition of sulphate and halide salts onto ash afm imaging also has permitted the detection of extremely thin 10 nm coatings on the surface of ash this material is probably composed of soluble sulphate and halide salts mixed with sparingly soluble fluoride compounds the surface approach developed here offers promising aspects for better appraising the role of gas aerosol ash interaction in dictating the ability of ash to act as sinks for various volcanic and atmospheric chemical species as well as sources for others c 2007 elsevier b v all rights reserved

black shale deposition and faunal overturn in the devonian appalachian basin clastic starvation seasonal water column mixing and efficient biolimiting nutrient recycling integrated geochemical data suggest that black shale deposition in the devonian geneseo formation of western new york was initiated by the coincidence of siliciclastic starvation and the intensification of seasonal water column stratification and mixing once established however black shale deposition was maintained through efficient recycling of biolimiting nutrients which enhanced primary productivity recycling efficiency was achieved through a positive feedback loop of oscillating benthic redox conditions that enhanced n and p regeneration from sediments sustained high primary productivity by returning nutrients to the photic zone during mixing and ensured a downward flux of organic matter that drove or enhanced the episodic development of benthic anoxia during stratification this feedback was ultimately disrupted by rising siliciclastic influx which diluted organic matter and restored benthic redox stability the abrupt overturn of diverse long standing appalachian basin marine communities may have been the result of trophic resource destabilization during geneseo deposition

near surface scholte wave velocities at ekofisk from short noise recordings by seismic noise gradiometry we propose a new approach for imaging the subsurface using a stochastic wavefield of interface waves present in the ambient seismic field unlike seismic interferometry our technique does not rely on cross correlations to obtain the green s function between two seismic receivers rather it relies on the local measurements of phase velocity obtained directly from the ratio between second order temporal and spatial derivatives of the wavefield we process 10 min of ambient seismic noise recording made using a large and dense array installed over ekofisk we image a subsidence induced geomechanical imprint on the scholte wave phase velocities in the near surface this resulting phase velocity pattern is verified by comparison to results from a seismic noise cross correlation tomography

small aperture seismic array data processing using a representation of seismograms at zero crossing points abstract a new method for representing seismograms by using zero crossing points is described this method is based on decomposing a seismogram into a set of quasi harmonic components and subsequently on determining the precise zero crossing times of these components an analogous approach can be applied to determine extreme points that represent the zero crossings of the first time derivative of the quasi harmonics such zero crossing and or extreme point seismogram representation can be used successfully to reconstruct single station seismograms but the main application is to small aperture array data analysis to which standard methods cannot be applied the precise times of the zero crossing and or extreme points make it possible to determine precise time differences across the array used to retrieve the parameters of a plane wave propagating across the array namely its backazimuth and apparent phase velocity along the earth s surface the applicability of this method is demonstrated using two synthetic examples in the real data example from the p ibram haje array in central bohemia czech republic for the mw 6 4 crete earthquake of october 12 2013 this method is used to determine the phase velocity dispersion of both rayleigh and love waves the resulting phase velocities are compared with those obtained by employing the seismic plane wave rotation to translation relations in this approach the phase velocity is calculated by obtaining the amplitude ratios between the rotation and translation components seismic rotations are derived from the array data for which the small aperture is not only an advantage but also an applicability condition

small aperture array translational and rotational seismograms from distant sources an example of the jan mayen mw 6 8 of 30 august 2012 earthquake abstract we present the seismic rotation rate due to the earthquake of mw 6 7 at the jan mayen island obtained from broad band seismograms at a distance of about 2740 km the order of magnitude of the rotation rate amplitude is only 10 9 rad s in this case it is studied with a focus on rotation to translation relations a joint analysis of the rotational and translational data allowed us to determine the true backazimuth and phase velocity of s and rayleigh waves for the surface waves we studied the frequency dependence of both the backazimuth and phase velocity wave dispersion the results are independently confirmed by a method based on time delays between translational records within a small aperture array both methods revealed an unusual velocity drop in the dispersion curve between the periods of 18 and 22 s this feature may be an indication of a low velocity zone in the lower crust

continuous hydrocarbon accumulation over a large area as a distinguishing characteristic of unconventional petroleum the ordos basin north central china abstract global petroleum exploration is currently undergoing a strategic shift from conventional to unconventional hydrocarbon resources unconventional hydrocarbons in tight reservoirs show characteristics distinct from those of conventional hydrocarbon sources hosted in structural and stratigraphic traps the characteristic features include the following a hydrocarbon source and reservoir coexist porosity and permeability are ultra low nano pore throats are widely distributed hydrocarbon bearing reservoir bodies are continuously distributed there is no obvious trap boundary buoyancy and hydrodynamics have only a minor effect and darcy s law does not apply phase separation is poor there is no uniform oil gas water interface or pressure system and oil or gas saturation varies examples of unconventional hydrocarbon accumulations are the mesozoic tight sandstone oil province and the upper paleozoic tight sandstone gas province in the ordos basin north central china generally continuous hydrocarbon accumulation over a large area is a distinguishing characteristic of unconventional hydrocarbon sources because of the great potential of unconventional petroleum resources it is believed that research on such resources will be at the forefront of the future development of petroleum geology

enhanced productivity led to increased organic carbon burial in the euxinic north atlantic basin during the late cenomanian oceanic anoxic event 1 three cenomanian turonian c t 93 5 ma black shale sections along a northeast southwest transect in the southern part of the proto north atlantic ocean were correlated by stable carbon isotope stratigraphy using the characteristic excursion in 13c values of both bulk organic matter om and molecular fossils of algal chlorophyll and steroids all three sites show an increase in marine organic carbon oc accumulation rates during the c t oceanic anoxic event oae the occurrence of molecular fossils of anoxygenic photosynthetic green sulfur bacteria lack of bioturbation and high abundance of redox sensitive trace metals indicate sulfidic conditions periodically reaching up into the photic zone before as well as during the c t oae during the c t oae there was a significant rise of the chemocline as indicated by the increase in concentrations of molecular fossils of green sulfur bacteria and mo al ratios the presence of molecular fossils of the green strain of green sulfur bacteria indicates that euxinic conditions periodically even occurred at very shallow water depths of 15 m or less during the c t oae however bottom water conditions did not dramatically change as indicated by more or less constant v al and zn al ratios at site 367 this suggests that the increase in oc burial rates resulted from enhanced primary productivity rather than increased anoxia which is supported by stable carbon isotopic evidence and a large increase in ba al ratios during the c t oae the occurrence of the productivity event during a period of globally enhanced organic carbon burial rates i e the c t oae points to a common cause possibly related to the formation of a deep water connection between north and south atlantic basins

gradiometry for polarized seismic waves 1 wave gradiometry for a generic point source wave model in cylindrical coordinates is developed to utilize the horizontal components of seismic wavefields attributes of p sv and sh waves such as horizontal slowness and its change the change in geometrical spreading the change in radiation pattern azimuth of propagation and wave polarization can be determined by measuring the horizontal strains and rotations of the wavefield along with three components of displacement gradiometer cells composed of an array of three component seismographs can be used to provide estimates of the wave gradients alternatively a single three component seismograph collocated with an areal strainmeter for p sv waves or a rotation sensor for sh waves can be used to estimate wave polarization and the slowness amplitude behavior of one aspect of the wavefield wave gradients are computed for the 1 april 2007 solomon island earthquake using data from the anza seismic network in southern california and show excellent consistency among stations of the network azimuth and slowness of various long period teleseismic waves are recovered using gradiometry analysis the consistency of strains computed from the broadband array suggests that they may be used to calibrate plate boundary observatory tensor strainmeters in the region

late paleozoic depositional history of the tarim basin northwest china an integration of biostratigraphic and lithostratigraphic constraints this study provides the first detailed lithostratigraphic and biostratigraphic constraints for improving stratigraphic resolution for hydrocarbon prospecting and exploration in the tarim basin a total of 49 stratigraphic units 38 formations and 11 members ranging in age from the latest devonian to permian are reviewed or redefined in terms of nomenclatures lithology age constraints and lateral distributions based on the detailed field works or newly published data of these the piqiang formation new formation is proposed to include the reefal carbonates of asselian sakmarian age from the northern tarim the subsurface upper paleozoic stratigraphic framework of the desert areas of the basin is also established for the first time the high resolution basinwide stratigraphic correlations reveal that the sedimentation of the basin in the late paleozoic was extremely uneven of these the famennian to changhsingian successions are completely recorded in the southwestern margin areas of the basin here five eustatic sedimentary cycles are well recognizable suggesting the sedimentation was more eustatically controlled and little affected by local tectonism the late paleozoic successions of both kalpin and taklimakan regions are commonly interrupted by major hiatuses at various horizons suggesting that the sedimentation was apparently modified by local tectonism of these the northward movement of the tarim block and its subsequent collision with the yili microcontinent part of the kazakhstan plate may be principally accountable for the discrepancy in the sedimentation of the various regions in the basin in the late paleozoic

facies and origin of shales from the mid proterozoic newland formation belt basin montana usa shales constitute more than 60 of the world s sediments yet while facies models for sandstones and carbonates are at a high level of sophistication the study of shales has clearly lagged behind in the mid proterozoic newland formation six major shale facies types deposited in nearshore to basinal environments are distinguished on the basis of bedding characteristics textural features and the proportions of silt clay and carbonate textural features of these shale types are related to sedimentary environments as deduced from associated lithologies the shales are undisturbed by bioturbation and their textural and sedimentary characteristics reflect subaqueous growth of microbial mats erosion and deposition by storms deposition of flocculated vs dispersed clays continuous slow background sedimentation winnowing by waves or currents and subaerial exposure

seismic wave gradiometry using the wavelet transform application to the analysis of complex surface waves recorded at the glendora array sullivan indiana usa abstract this article describes a new development in seismic wave gradiometry the work follows previous work on time domain wave gradiometry but proposes applying a wavelet transform to the data prior to wave gradiometric analysis the result is a more complete picture of wave attributes which vary in time as well as frequency in this article the new data analysis approach is used to analyze two underwater shots that were recorded by a portion of the glendora array the glendora site is a former surface coal mine that has subsequently been filled by mine tailings and as such forms an artificial sedimentary basin in which the geometry is well known the array used for the analysis was located in a corner formed by the intersection of two vertically oriented boundaries between mine tailings and the surrounding bedrock the analysis of the data revealed the presence of typical body waves and surface waves in addition to several phases that are interpreted to be 1 reflections of surface waves off of the vertical tailings bedrock boundaries 2 surface waves generated by the interaction of direct arrival waterborne acoustic waves with the water tailing interface the lake shore and 3 the interaction of other waterborne acoustic waves in glendora lake with other water tailing interfaces the surface waves are highly time dependent and frequency dependent and highlight the extreme complexity of surface wave propagation in geologically complex areas

spatial gradient analysis for linear seismic arrays i incorporate the spatial gradient of the wave field recorded from one dimensional arrays into a processing method that yields the horizontal wave slowness and the change of geometrical spreading with distance in general the model for seismic wave propagation is enough to be appropriate for body and surface waves propagating from nearby seismic sources but can be simplified into a plane wave model although computation of the spatial gradient requires that array elements be closer than 10 of the horizontal wavelength seismic array apertures in the usual sense may extend over many horizontal wavelengths and illuminate changes within the wave field array images of horizontal slowness and the relative geometrical spreading changes of seismic waves are derived using filter theory and used to interpret observed array wave fields errors in computing finite difference spatial gradients from array nodes are explicitly considered to avoid spatial aliasing in the estimates i apply the method to interpret waves in strong ground motion and small scale refraction data sets use of the wave spatial gradient accentuates spatial differences in the wave field that can be theoretically exploited in fine scale tomographic studies of structure and is complementary to frequency wavenumber or beam forming array processing techniques

organic matter production and preservation and evolution of anoxia in the holocene black sea dating of sediments collected in gravity cores during leg 1 of the 1988 r v knorr expedition to the black sea suggests that the onset of water column anoxia at 7 5 ka was virtually synchronous across the basin over a depth range of 200 2250 m a finely laminated organic carbon oc rich sapropel unit ii was produced as a result of this anoxia the trigger for increased oc production and development of anoxia was the spillover of saline waters through the bosporus that probably began at 9 0 ka and peaked between 7 0 and 5 5 ka this spillover enhanced vertical mixing and nutrient cycling and caused a short term 2 3 kyr burst in surface water productivity during the early part of unit ii deposition continued incursion of saline waters enhanced vertical stability and inhibited mixing of nutrients into surface waters thus limiting primary production and decreasing the oc flux to sediments beginning 5 5 ka concentration accumulation rate and degree of preservation of organic matter all decreased in the upper part of unit ii as a result of decreasing productivity but anoxia persisted throughout most of the water column the end of unit ii sapropel deposition was synchronous across the black sea as the result of the first blooms of the coccolith emiliania huxleyi which presumably marked an increase in surface water salinity above 11 and the beginning of unit i deposition the high coccolith carbonate fluxes that occurred during deposition of unit i diluted the oc concentration in the sediments but oc accumulation rates are about the same as those in upper part of unit ii

wave gradiometry for usarray rayleigh waves 1 wave gradiometry wg is a new array data processing technique to extract phase velocity wave directionality geometrical spreading and radiation pattern from spatial gradients of waveforms a weighted inversion method and a reducing velocity method are introduced to compute spatial gradients accurately for irregular arrays numerical experiments are conducted to test techniques and to evaluate the parameters determined from the wg method we apply this method to usarray data for the western united states in this study rayleigh waves from nine earthquakes with varying azimuths are analyzed the stability of this method is shown by the similarity between the results from two nearly collocated earthquakes from the kurile islands the error check shows the wg results are stable for ambient noise level as high as 10 phase velocities determined by wg and two station ts methods are statistically consistent while these determined from beam forming method are systematically higher for wavelength larger than one quarter of the array diameter our results show that first the average phase velocities of rayleigh waves range from 3 8 to 4 1 km s for periods from 60 s to 150 s this is consistent with average earth models the prominent feature on the phase velocity map is that the basin and range province is dominated by velocity lows while the west coast of the united states and the north and northeastern snake river plain are dominated by velocity highs the snake river plain appears to be a primary tectonic boundary second azimuthal variations represent the accumulated wave directionality changes along the raypath a velocity contrast of 0 25 km s across the oceanic continental lithosphere boundary along the west coast of the united states is needed to explain the negative azimuth variations third geometrical spreading is slightly anticorrelated with phase velocity which may suggest that amplitude variations in radial directions are subject to surface wave focusing and defocusing fourth similar to the wave directionality radiation pattern variations also exhibit strong path dependence further theoretical and experimental studies will be conducted to understand the two amplitude parameters geometrical spreading and radiation pattern and their relations with the local geophysical properties

thin fine grained storm layers in a muddy shelf sequence an example from the lower jurassic in the stenlille 1 well denmark thin storm sand layers are a characteristic feature of many sandy shelf sequences while little evidence of storm layers is preserved in muddy shelf deposits where bioturbation is often total the present study shows that storm generated depositional processes governed sedimentation in a muddy shelf environment the studied sequence is dominated by blackish mudshale and silt streaked mudshale with thinner intervals of pale fine grained heterolithic sandstone it represents the lower jurassic fjerritslev formation in the eastern part of the danish basin and has been studied in four cores from the stenlille 1 well within the muddy outer shelf association four sedimentary facies and 14 types of laminae 0 5 10 mm thick may be distinguished most of the laminae share the characteristics of graded bedding erosive bases and occasional fading ripples with storm layers of sand grade the structures indicate that the mudshale laminae formed by settling of the suspension load carried by storm generated currents this kind of episodic deposition of fine grained storm layers may be common though rarely preserved in outer shelf environments

wave gradiometry and its link with helmholtz equation solutions applied to usarray in the eastern u s wave gradiometry is an array processing technique utilizing the shape of seismic wavefields captured by usarray ta stations to determine fundamental wave propagation characteristics we first explore a compatibility relation that links the displacement spatial gradients to seismogram displacements and velocities through two unknown coefficients a and b these coefficients are solved for through iterative damped least squares inversion to provide estimates of phase velocity back azimuth radiation pattern and geometrical spreading we show that the a coefficient corresponds to the gradient of logarithmic amplitude and the b coefficient corresponds approximately to the local wave slowness a and b vector fields are interpolated to explore a second compatibility relation through solutions to the helmholtz equation for most wavefields passing through the eastern u s we show that the a coefficients are generally orthogonal to the b coefficients where they are not completely orthogonal there is a strong positive correlation between b and changes in geometrical spreading which can be further linked with areas of strong energy focusing and defocusing we finally obtain isotropic rayleigh wave phase velocity maps for 15 periods between 20 and 150 s by stacking results from 37 earthquakes which show a velocity change along the approximate boundary of the early paleozoic continental margin we also observe two low velocity anomalies one centered over the central appalachians where eocene basaltic volcanism has occurred and the other within the northeastern u s possibly associated with the great meteor hotspot track

phanerozoic organic carbon rich marine sediments overview and future research challenges one of the major obsessions of many early workers to the mid 1900s was the application of uniformitarian principles to deposi tional models for black shales arthur and sageman 1994 the purpose of this overview of organic carbon oc rich marinesediments is to provide a brief but current summary of the historicaldevelopments principle concepts and remaining challenges in inte grated sapropel and black shale research as such it provides asubstantive introduction to the special issue of palaeogeography palaeoclimatology palaeoecology on organic carbon rich sedimentsthrough the phanerozoic processes progress and perspectives giventhis focused scope the overview does not aim to be comprehensive orcomplete but to provide a solid setting for the fourteen individualresearch papers that constitute this special issue and two previousspecial issues meyers and negri 2003 negri et al 2006 thatcoverresearch aspects complementary to this one like the individualcontributions this introduction and overview is organized intocenozoic mesozoic and palaeozoic units the cenozoic and palaeozoicunitsaredeliberatelylargerthanthemesozoicunit acknowledgingthatmuch ground on mesozoic black shale is already covered in the twoprevious special issues because the late cenozoic sapropels of themediterraneanbasinhavebeenextensivelystudied understandinghowthese near modern analogs of ancient black shales were depositedprovidesagoodfoundationforunderstandinghowtheoldersequencesmayhaveevolved incontrast becausefarlessisgenerallyknownabouttheblackshalesofthepalaeozoicthancomparableoc richsequencesofeither the cenozoic or the mesozoic a more comprehensive summaryand comparison of the more ancient sequences is particularly appro priate to the theme of this special issue 1 introductionsediments rich in organic carbon are restricted to small areas alongcontinental margins in the modern ocean and have rarely accumulatedduringthecenozoic yetorganic rich sediments werewidely depositedduring multiple intervals of mesozoic palaeozoic time and even earlierduringtheproterozoic archean globalmarinedepositsdocumentthatepisodes of accumulation of oc rich sediments occurred in differentregions and at different times these episodes were linked to climaticandpalaeoceanographicperturbationsthat resulted inmassive uctua tions in hydrologic and nutrient cycles and in oceanchemistryand thatrecurred throughout geologic time however the paucity of survivingpalaeozoic and earlier black shale sections makes it dif cult toimpossible to recognize the internal structure of global events that arecommon inyounger oc rich sedimentary sequences asunderlinedbelow themarinesectionsinmanylocalitiesconsistof intercalated carbonates and shales that may grade into purecarbonate or black shale sedimentation often re ecting shallowing

an integrated assessment of a type euxinic deposit evidence for multiple controls on black shale deposition in the middle devonian oatka creek formation an integrated lithologic paleontologic and multi proxy geochemical study of the middle devonian oatka creek formation a black shale in the northern appalachian basin indicates that a number of different factors contributed to organic carbon rich black shale deposition conditions leading to this organic rich sedimentary deposit were ultimately controlled by a relative sealevel rise dominantly eustatic but with possible contributions from local tectonics which cut off the supply of carbonate to the basin geochemical proxy evidence such as mo ti fe ti corg spy and 34spy suggests that as sealevel continued to rise after the carbonate supply was cut off a threshold was crossed at which point conditions in the basin shifted from dominantly anoxic to dominantly euxinic anoxic sulfidic bottom waters concurrent with the shift to dominantly euxinic conditions the supply of siliciclastic sediments was cut off resulting in a condensed horizon as evidenced by the elemental ratios of si al and k fe mg and the relative concentration of eolian silt as determined petrographically and from scanning electron microscopy sediment starvation in the basin appears to have facilitated the biogeochemical re cycling of c n and p specifically the elemental ratios of c n and p and the stable carbon isotope composition of organic matter suggest that the preferential regeneration of p under anoxic conditions and of n during the oxic phase of oxic anoxic oscillation led to enhanced primary production in surface waters thereby maintaining euxinic conditions in the bottom waters through respiration of settling organic matter finally it is observed that though conditions in the basin seem to have remained consistently anoxic sulfidic for some time after the initial shift to euxinic conditions a progressive increase in siliciclastic sedimentation led to a corresponding decrease in the enrichment of various redox related elements illustrating the overriding control that sedimentation can have on geochemical proxy records

wave gradiometry in two dimensions the spatial displacement gradient of a seismic wave is related to dis placement and velocity through two spatial coefficients for any one dimension one coefficient gives the relative change of wave geometrical spreading with distance and the other gives the horizontal slowness and its change with distance the essential feature of spatial gradient analysis is a time domain relation between three seismo grams that yields information on the amplitude and phase behavior of a seismic wave filter theory is used to find these coefficients for data from 2d areal arrays of seismometers termed gradiometers a finite difference star is used to compute the displacement gradient for irregularly shaped gradiometers and a relation for the frequency dependent error in the displacement gradient is obtained and applied to ensure accurate estimates this kind of array analysis is useful for gradiometers at any distance from a source and yields a variety of time domain and frequency domain views of wave amplitude changes and horizontal phase velocity estimates across the gradiometer for example time dependent horizontal slowness and wave azimuth plots are natural results of the analysis these time domain maps may be used in conjunction with time distance and horizontal slowness distance models to locate seismic sources or may be used directly to study earth structure these methods are demonstrated by using data from a small aperture 40 m seismic gradiometer

palaeoceanographic controls on geochemical characteristics of organic rich exshaw mudrocks role of enhanced primary production organic rich source rocks have generally been attributed to enhanced preservation of organic matter under anoxic bottom waters here geochemical analysis of kerogen and whole rock samples of organic rich lithofacies b1 and organic lean lithofacies b2 laminated mudrocks of the devonian carboniferous exshaw formation alberta highlight the importance of primary production in governing the quantity and quality of organic matter lower si al k al ti al and quartz clay ratios in lithofacies b2 similar maceral types and the laminated fabric of the two lithofacies indicate that the quality and quantity of organic matter are not related to grain size redox or organic matter source changes high total organic carbon toc and hydrogen index hi low oxidation index ox i ratio of oxygen functional groups to aliphatic groups derived by ftir lighter 15ntot and heavier 13corg isotopes indicate that kerogen of lithofacies b1 accumulated during periods of high organic carbon production and delivery of relatively fresh labile well preserved organic matter to the sea floor in contrast low toc hi high ox i heavier 15ntot and lighter 13corg isotopes indicate low primary productivity and delivery high recycling and poor preservation of organic matter during accumulation of lithofacies b2

subduction zone volcanic ash can fertilize the surface ocean and stimulate phytoplankton growth evidence from biogeochemical experiments and satellite data volcanoes confront earth scientists with new fundamental questions can airborne volcanic ash release nutrients on contact with seawater thereby excite the marine primary productivity mpp and most notably can volcanoes through oceanic fertilization affect the global climate in a way that is so far poorly understood here we present results from biogeochemical experiments showing that 1 volcanic ash from subduction zone volcanoes rapidly release an array of nutrients co limiting algal growth in vast oceanic areas 2 at a speed much faster minute scale than hitherto known and that marine phytoplankton from low iron oceanic areas can swiftly within days utilize iron from volcanic sources we further present satellite data possibly indicating an increase of the mpp due to the seaward deposition of volcanic particulate matter our study supports the hypothesis that oceanic iron fertilization with volcanic ash may play a vital role for the development of the global climate

bulk sediment qp and qs in the mississippi embayment central united states we have estimated p wave ands wave anelastic attenuation coefficients for the thick unconsolidated sediments of the mississippi embayment central united states using the spectral distance decay of explosion p and rayleigh waves the sediment trapped p wave psed is observed to ranges of 80 km at 10 hz and 1 hz rayleigh waves are observed out to 130 km from a 5000 lb borehole explosion in the northern part of the embayment rayleigh waves of 4 hz are seen to distances of 3 km from a smaller 50 lb explosion analysis of the group velocity and amplitude distance decay of both waves yields an average qs of 100 and qp of 200 for embay ment sediments that are independent of frequency scatter in the q estimates comes from interference of multiple p wave reverberations and rayleigh wave modes the attenuation model is self consistent in that it is the same as obtained by the analysis of synthetic seismograms using the inferred q values inferred qp and qs values are more than three times higher than previous estimates and imply that unconsolidated sediments of the embayment do not significantly attenuate small strain earthquake ground motions these estimates represent a lower bound to q of the sediments since significant scattering is observed in the waveform data that contributes to the distance decay of wave amplitude higher q values also imply that the unconsolidated sedi ments of the embayment will form an efficient wave guide for surface waves radiated from shallow earthquakes or large earthquakes that rupture into the sediments pro ducing high amplitude long duration wave trains that should be considered in earth quake hazard assessments

dynamic strains at regional and teleseismic distances abstract we develop formulas for the size of dynamic strains caused by seismic waves from an earthquake of given magnitude and distance these formulas include peak strain peak dissipated power and total dissipated energy and they are applicable at regional and teleseismic distances the formulas are fits to data from 89 large 6 5 m w 9 0 shallow earthquakes with source distances between 500 and 16 000 km recorded between 1977 and 2013 by three long base laser strainmeters at pinon flat observatory in southern california these strainmeters provide uniquely well calibrated measurements of tensor strain the residuals to the fits suggest that strain values can usually be predicted to within a factor of 2 these data also show that the strain tensor can be substantially different from that expected for plane waves in particular the extension perpendicular to the back azimuth which should be zero is always 20 or more of the extension along that azimuth how much the strains resemble those for plane waves depends on their path perhaps because inhomogeneities along different paths produce different amounts of multipathing the observed strains are systematically 10 30 larger at nearby laser strainmeter sites in the salton trough suggesting local amplification from inhomogeneous crustal structure online material tables of earthquake catalogs and dynamic strain analysis and figures of earthquake magnitude distance distributions and time delays of maximum strain

the effects of measurement uncertainties in seismic wave gradiometry abstract in seismic wave gradiometry the spatial gradient and the time derivative of the measured wavefield are used to estimate the slowness vector and changes in the radiation pattern when using a seismic array to estimate the seismic spatial derivatives the array aperture cannot be greater than approximately 10 of the target wavelength to avoid spatial aliasing effects however there has been little research into the minimum practical array aperture in this article we investigate the effects of measurement uncertainties on the accuracy of gradiometrically estimated wave parameters as well as provide recommendations on design criteria for gradiometric arrays the design parameters are based on wavefield slowness frequency and measurement uncertainty

advances in 6c seismology applications of combined translational and rotational motion measurements in global and exploration seismology over the past few decades the potential of collocated measurements of 6c data 3c of translational and 3c of rotational motion has been demonstrated in global seismology using high sensitivity observatory based ring laser technology proposed applications of 6c seismology range from tomographic reconstruction of near receiver structure to the reduction of nonuniqueness in seismic source inverse problems applications to exploration problems have so far been hampered by the lack of appropriate sensors but several applications have been proposed and demonstrated with array derived rotational motion estimates with the recent availability of for example fiber optic based high sensitivity rotational motion sensors widespread applications of 6c techniques to exploration problems are in sight potential applications are based on for example the fact that the extended set of combined translational and rotational motion observations enables carrying out array type processing with single station recordings such as wavefield separation and surface wave suppression furthermore measuring the rotational component curl of the seismic wavefield enables direct isolation of the s wave constituents and could significantly improve s wave exploration rotational measurements provide estimates of the spatial wavefield gradient at the free surface that allow carrying out analyses such as local slowness estimation and wavefield reconstruction furthermore rotational motion measurements can help to resolve wavefield infidelity introduced by seismic instruments that are not well coupled to the ground

regional wave propagation in southern california and nevada observations from a three component seismic array we present results from a study conducted to characterize regional wave propagation in southern california and nevada the data are from events whose paths sample the southern coast ranges the southern sierra nevada mountains and the southern basin and range these regional earthquake data were recorded by a small aperture three component seismic array located at the pinon flat observatory southern california the data are analyzed using a statistical array processing algorithm that provides estimates of the propagation direction frequency wavenumber and particle motion polarization characteristics of the coherent arrivals observed at the array perhaps the most striking feature shared by these data is the extent to which the p s and lg wave trains are composed of coherent forward scattered multipathed energy the nature of the p s and lg wave trains suggests that spatially anisotropic scattering plays an important role in regional wave propagation in southern california and nevada and that scattering sources are located not on elliptical shells whose foci are the source and the receiver but instead in a limited volume subparallel to the path of the direct arrivals the high amplitude coherent nature of numerous of the pg and lg coda waves suggests that strong scattering in the source zone plays an important role in shaping the pg and lg wave trains while the p s and lg wave trains for these regional events share some general characteristics they also exhibit fairly significant differences these differences illustrate the important role regional and source zone structure play in shaping the wave field and the need to account for both complex scattering and three dimensional propagation effects in regional waveform modeling the coda for these regional data do not begin to exhibit a character consistent with the random scattering model for coda generation until the arrival of the surface waves the fact that much of the surface wave coda cannot be effectively modeled as plane waves suggests that it is not the product of scattering from distant heterogeneities

review progress in rotational ground motion observations from explosions and local earthquakes in taiwan rotational motions generated by large earthquakes in the far field have been successfully measured and observations agree well with the classical elasticity theory however recent rotational measurements in the near field of earthquakes in japan and in taiwan indicate that rotational ground motions are 10 to 100 times larger than expected from the classical elasticity theory the near field strong motion records of the 1999 mw 7 6 chi chi taiwan earthquake suggest that the ground motions along the 100 km rupture are complex some rather arbitrary baseline corrections are necessary in order to obtain reasonable displacement values from double integra tion of the acceleration data because rotational motions can contaminate acceleration observations due to the induced perturbation of the earth s gravitational field we started a modest program to observe rotational ground motions in taiwan three papers have reported the rotational observations in taiwan 1 at the hgsd station liu et al 2009 2 at the n3 site from two taiwan integrated geodynamics research taiger explosions lin et al 2009 and 3 at the taiwan campus of the national chung cheng university nccu wuet al 2009 in addition langston et al 2009 reported the results of analyzing the taiger explosion data as noted by several authors before we found a linear relationship between peak rotational rate prr in mrad sec and peak ground acceleration pga in m sec 2 from local earthquakes in taiwan prr 0 002 1 301 pga with a correlation coefficient of 0 988

organic matter accumulation of late ordovician sediments in north guizhou province china sulfur isotope and trace element evidences abstract the organic rich upper ordovician sediments wufeng and guanyinqiao formations on the yangtze platform are considered to be one of the main source rocks here we present geochemical proxies including redox indicator s c ratios and sulfur isotopes and productivity indices toc mo and ba contents from nanbazi section in north guizhou province south china in order to investigate the mechanism of organic matter accumulation the geochemical data suggest a stagnant and anoxic environment predominated the yangtze sea during the wufeng period whereas ventilated and oxygenated marine conditions pervaded the yangtze sea during the guanyinqiao period variations in the concentration of toc mo and ba indicate that higher organic carbon export in the wufeng intervals than those in the guanyinqiao intervals these variations in redox and productivity during the late ordovician were associated with different mechanisms and forcing processes the abrupt change from anoxic to oxygenated condition at the beginning of the guanyinqiao was concomitant with the global glacial period likely resulted from the glacio eustatic sea level fall and subsequent circulation of cold dense oxygenated waters upon the shelf seabed the productivity variations were related to the change of nutrient supply which is consistent with volcanic activities and runoff to the yangtze sea redox changes together with primary productivity fluctuations could have played a significant role on the variation of organic matter accumulation during the late ordovician in south china

multiwavelet seismic wave gradiometry abstract a new technique to determine uncertainty estimates for wave parameters obtained by seismic wave gradiometry is established using the multiwavelet transform wave gradiometry uses spatial gradients as measured by a small scale seismic array to estimate the wave parameters of propagation azimuth slowness geometrical spreading and radiation pattern the advantage of wave gradiometry is that the wave parameters are estimated on a point by point basis for the entire seismogram previous work on wave gradiometery employed the continuous wavelet transform to decompose the wave field into narrow band realizations prior to gradiometric analysis so that the wave parameters are resolved as functions of both time and frequency to build on this approach i incorporated the multiwavelet transform the multiwavelet transform decomposes the wave field into a series of mutually orthogonal wavelet coefficients which can then be analyzed by wave gradiometry each result can then be treated as a sample from a statistical population the method is tested on synthetic data with and without noise a relatively low degree of uncorrelated noise can have a significant impact on the quality of the results finally multiwavelet gradiometry is applied to a single earthquake recorded by a small subset of usarray stations and shows that the method accurately and robustly determines the wave parameters

marine transgressional events in the gigantic freshwater lake songliao paleontological and geochemical evidence abstract the fossil remains of euryhaline organisms in the mesozoic cenozoic non marine sedimentary records of eastern china may have resulted from either marine transgressions or inland hypersaline lacustrine environments paleontological and organic geochemical results of this study have provided new evidence for marine transgressional events in the gigantic freshwater lake songliao during the late cretaceous

redox sensitivity of p cycling during marine black shale formation dynamics of sulfidic and anoxic non sulfidic bottom waters abstract a high resolution geochemical record of a 120 cm black shale interval deposited during the coniacian santonian oceanic anoxic event 3 odp leg 207 site 1261 demerara rise has been constructed to provide detailed insight into rapid changes in deep ocean and sediment paleo redox conditions high contents of organic matter sulfur and redox sensitive trace metals cd mo v zn as well as continuous lamination point to deposition under consistently oxygen free and largely sulfidic bottom water conditions however rapid and cyclic changes in deep ocean redox are documented by short term 15 20 ka intervals with decreased total organic carbon toc s and redox sensitive trace metal contents and in particular pronounced phosphorus peaks up to 2 5 wt p associated with elevated fe oxide contents sequential iron and phosphate extractions confirm that p is dominantly bound to iron oxides and incorporated into authigenic apatite preservation of this fe p coupling in an otherwise sulfidic depositional environment as indicated by fe speciation and high amounts of sulfurized organic matter may be unexpected and provides evidence for temporarily non sulfidic bottom waters however there is no evidence for deposition under oxic conditions instead sulfidic conditions were punctuated by periods of anoxic non sulfidic bottom waters during these periods phosphate was effectively scavenged during precipitation of iron oxyhydr oxides in the upper water column and was subsequently deposited and largely preserved at the sea floor after 15 25 ka sulfidic bottom water conditions were re established leading to the initial precipitation of cds zns and pyrite subsequently increasing concentrations of h2s in the water column led to extensive formation of sulfurized organic matter which effectively scavenged particle reactive mo complexes thiomolybdates at site 1261 sulfidic bottom waters lasted for 90 100 ka followed by another period of anoxic non sulfidic conditions lasting for 15 20 ka the observed cyclicity at the lower end of the redox scale may have been triggered by repeated incursions of more oxygenated surface to mid waters from the south atlantic resulting in a lowering of the oxic anoxic chemocline in the water column alternatively sea water sulfate might have been stripped by long lasting high rates of sulfate reduction removing the ultimate source for hs production

facies patterns and geography of the yangtze region south china through the ordovician and silurian transition abstract lithofacies and biofacies changes through the ordovician and silurian transition on the yangtze platform are coincident with stepwise mass extinctions recovery events global sea level changes and regional palaeogeographic configurations facies patterns through three intervals the late mid ashgill hirnantian and early rhuddanian indicate that black shale occupied most of the yangtze platform region during the late mid ashgill and early rhuddanian while the hirnantian possesses more diverse facies types the black shale was replaced by carbonate facies during the hirnantian coincident with a global sea level low stand biofacies changes from the late mid ashgill graptolitic to the hirnantian shelly facies were apparently signalled by gradual and diachronous existence of a mixed facies the manosia facies in the yangtze region however the biofacies change was abrupt from the hirnantian to the early rhuddanian when graptolitic facies occupied most areas on the yangtze platform leaving only a very narrow limited belt of shelly facies along the southern margin of the platform in northern guizhou the early rhuddanian unified biofacies pattern is a result of a global sea level rise which may be synchronized with a recovery bioevent of graptolites after hirnantian mass extinction

sedimentation rate dilution preservation and total organic carbon some results of a modelling study abstract a modelling exercise was undertaken to evaluate the positive preservational and negative diluent effects of sedimentation rate sr on the total organic carbon toc content of marine sediments and to use multiple regression analysis of modern data to predict toc data presented show the predicted marine toc using the carbon burial efficiency be versus sr relationship of betts and holland betts j n holland h d 1991 the oxygen content of ocean bottom waters the burial efficiency of organic carbon and the regulation of atmospheric oxygen palaeogeography palaeoclimatology palaeoecology global and planetary change section 97 5 18 calculated for a range of sr water depths primary productivities and four fixed be values the results suggest that the preservation effect of sr only enhances toc at 5 cm ka in oxic regimes after which dilution occurs if carbon supply is held constant above 35 cm ka there is no appreciable difference in toc regardless of whether the sea floor is anoxic or not below 10 cm ka there is a strong divergence in oxic and anoxic toc values observed positive correlations of sr and toc at 5 cm ka are largely an artefact of including sites from shallower depths and or higher productivities multiple regression analysis mra of modern marine sediment data suggests that once re scaled to allow for their non linear effect dissolved oxygen values may be a significant additional variable in determining the toc predicting an approximately 2 5 4 0 times higher toc in anoxic facies compared with fully oxic ones 4 ml l dissolved oxygen all other things being equal the mra also indicates a generally negative partial correlation between carbon delivery flux and be in modern sediments producing a significant moderating effect on the predicted toc

vertical seismic wave gradiometry application at the san andreas fault observatory at depth abstractwe have developed vertical seismic wave gradiometry vswg to estimate velocity impedance and attenuation structure in the vicinity of boreholes using borehole array waveforms of check shot explosions near the borehole head we have extended wave gradiometry wg theory from a purely local relation of the wavefield and wavefield spatial gradient to one that incorporated the ray ansatz over the length of the borehole for a traveling wave in a vertically inhomogeneous medium we checked the ray assumption against acoustic full wave synthetic seismograms and it was found to yield robust measures of the medium velocity anelastic attenuation and impedance structure trade off but in cases of high anelastic attenuation realistic bounds can be placed on the seismic impedance that effectively constrains the average attenuation we have applied these methods to data collected at the san andreas fault observatory at depth borehole in central california in 2005 and we found that the wg velocity estimat

recurring patterns of total organic carbon and source rock quality within a sequence stratigraphic framework sequence stratigraphy has been combined with total organic carbon toc analysis from well logs core and cuttings to develop a model of toc accumulation in marine source rocks routine well profiling of toc in marine source rocks has revealed that recurrent patterns in the vertical distribution of toc occur that can be explained with sequence stratigraphic concepts the model assumes that the principle controls on organic carbon accumulation are 1 the presence of low oxygen conditions at the sediment water interface and 2 sedimentation rate under these circumstances toc will vary inversely with terrigenous clastic influx if accommodation is high clastic influx is low in distal locations and the resulting weight percent toc in basinal sediments is increased th maximum toc in a vertical profile through a single marine sequence probably correlates to the maximum flooding surface toc decreases above this surface due to increasing sediment dilution during highstand progradation and decreases below it with the higher sedimentation rate of the older transgressive systems tract commensurate with toc increase towards the maximum flooding surface the organic matter type becomes more marine and therefore increasingly oil prone several marine source rock examples are presented as well as a lacustrine example which also conforms to the marine model

marine productivity changes during the end permian crisis and early triassic recovery abstract the latest permian mass extinction lpme coincided with major changes in the composition of marine plankton communities yet little is known about concurrent changes in primary productivity earlier studies have inferred both decreased and increased productivity in marine ecosystems immediately following the end permian crisis here we assess secular and regional patterns of productivity variation during the crisis through an analysis of the burial fluxes of three elemental proxies total organic carbon toc phosphorus p and biogenic barium babio primary productivity rates appear to have increased from the pre crisis late permian through the early triassic in many parts of the world although the south china craton is unusual in exhibiting a pronounced decline at that time most of the 14 permian triassic study sections show concurrent increases in sediment bulk accumulation rates suggesting two possible influences linked to subaerial weathering rate changes 1 intensified chemical weathering resulting in an increased riverine flux of nutrients that stimulated marine productivity and 2 intensified physical weathering leading to higher fluxes of particulate detrital sediment to continental shelves thus enhancing the preservation of organic matter in marine sediments an additional factor especially in the south china region may have been the intensified recycling of bacterioplankton derived organic matter in the ocean surface layer reducing the export flux rather than primary productivity per se the ecosystem stresses imposed by elevated fluxes of nutrients and particulate sediment as well as by locally reduced export fluxes of organic matter may have been important factors in the 2 to 5 million year long delay in the recovery of early triassic marine ecosystems

analysis of regional events recorded at noress abstract events recorded by noress are analyzed to determine the velocities and times of coherent crustal phases to be used in accurate locations and determination of crustal structure the events straddle two azimuthal directions and range in distance from 50 to 300 km thus sampling two cross sections of the crust and upper mantle one in the caledonides to the northwest of noress and the other to the south along the eastern rim of the oslo graben f k analysis is used to search for coherent phases in the data all vertical channels are then stacked with the appropriate time delays calculated from the phase velocities and azimuths obtained for the coherent arrivals finally a composite seismogram is made for each event by piecing together time sections from the stacks where each time piece represents a coherent arrival all detectable coherent phases are enhanced in the composite seismograms and on closer inspection it is possible to improve some of the locations from the noress bulletin this causes a number of events to group together to the same location travel time curves are constructed from plane layered homogeneous models to match travel times and phase velocities in the composite seismograms

introduction to the special issue on rotational seismology and engineering applications rotational seismology is an emerging field for studying all aspects of ro tational ground motions induced by earthquakes explosions and ambient vibrations it is of interest to a wide range of geophysical disciplines including strong motion seismology broadband seismology earthquake engineering earthquake physics seis mic instrumentation seismic hazards seismotectonics and geodesy as well as to physicists using earth based observatories for detecting gravitational waves generated by astronomical sources predicted by einstein in 1916 in this introduction to the bssa special issue on rotational seismology and engineering applications we will include 1 some background information 2 a summary of the recent events that led to this special issue and 3 an overview of its 51 papers 27 articles 11 short notes 4 reviews 6 tutorials and 3 supplementary articles our comments on these 51 papers are very brief and give just a hint of what the papers are about papers in this special issue demonstrate that earthquake monitoring cannot be limited to measuring only the three components of translational motion we also need to simultaneously measure the three components of rotational motion and the many components of strains a golden opportunity to improve our understanding of earth quakes lies in the near field of large earthquakes within about 25 km of the earthquake ruptures where nonlinear rock and soil response influences ground motions in a com plicated way

dynamic deformations of shallow sediments in the valley of mexico part i three dimensional strains and rotations recorded on a seismic array abstract we study the spatial variation in earthquake ground motions or equivalently the dynamic displacement gradient field using a novel analysis procedure borrowed from geodesy seismic data recorded in the valley of mexico by a microarray of three three component surface accelerographs and two three component accelerographs at depths of 30 m and 102 m constrain our estimates of the dynamic displacement gradient field from which strains and rotations derive for four moderate earthquakes at distances of 250 to 300 km our study focuses on the effects of low velocity surface materials on the deformation at the surface the gradients corresponding to deformation across vertical planes dominate and vertical axis rotations are of similar magnitudes as strains the greatest peak surface gradient we observed was 206 strain for the 14 september 1995 m w 7 5 earthquake at a distance of 300 km however much larger gradients occur across horizontal planes u z where u is a horizontal displacement and z is depth at some depth between 0 and 30 m these values are about a factor 10 greater than the corresponding gradient components at the surface u z for the 14 september earthquake equaled or exceeded 665 strain at depth the dynamic deformations experienced in mexico city undoubtedly have occurred before and will occur again in other densely populated areas however in many other regions the sediment response will not remain linear and elastic resulting instead in liquefaction and ground failure

organic matter and trace element rich sapropels and black shales a geochemical comparison a distinct pliocene eastern mediterranean sapropel i 282 recovered from three ocean drilling program odp leg 160 sites has been investigated for its organic and inorganic composition this sapropel is characterized by high organic carbon corg and trace element contents and the presence of isorenieratene derivatives the latter suggests that the base of the photic zone was sulphidic during formation of the sapropel combined with evidence of bottom water anoxia preservation of laminae high redox sensitive trace element contents and the abundance and isotopic composition of pyrite this leads to the tentative conclusion that almost the entire water column may have been anoxic this anoxia resulted from high productivity and not from stagnation because an approximation of the trace element budget during sapropel formation shows that water exchange with the western mediterranean is needed entire water column anoxia has been suggested earlier for several black shales with regard to the depositional environment and the corg content however only the cenomanian turonian boundary event ctbe black shales appear to be comparable to this sapropel the proposed trace element removal mechanism of scavenging and co precipitation in an anoxic water column is thought to be similar for both types of deposits the ultimate trace element source for the sapropel however is seawater whereas it is hydrothermal and fluvial input for ctbe black shales because they have a larger temporal and spatial distribution nonetheless the corg rich eastern mediterranean pliocene sapropel discussed here may be considered to be a younger analogue of ctbe black shales

seismic structure beneath the reykjanes peninsula southwest iceland inferred from array derived rayleigh wave dispersion abstract the aim is to obtain a site specific s wave structure beneath the reykjanes peninsula southwest iceland nine broadband stations of the reykjanet network are used to find rayleigh wave phase velocity dispersion in a relatively wide range of periods from 3 to 50 s the records analyzed were made in the years 2013 to 2015 and concern fourteen selected earthquakes whose epicentral distances range from tens of kilometers to almost ten thousand kilometers our approach to retrieving rayleigh phase velocity dispersion involves two partly independent methods allowing for array apertures larger than a wavelength 1 the zero crossing point method and 2 the phase plane method the two methods used here work with seismograms decomposed into quasi harmonic components and implicitly assume a single plane wave propagation the good match between the dispersion curves obtained by means of the two methods indicates that the assumption has been reasonably fulfilled the rayleigh wave phase velocity dispersion data are inverted into a horizontally layered isotropic s wave velocity model of the earth s crust and uppermost mantle by a modified method of the single parameter variation at shallow depths the derived model is rather similar to some previous models that were derived predominantly from the arrival times of body waves at depths exceeding about 20 km the dispersion data require low s wave velocities indicating a noticeable low velocity zone

organic matter accumulation and preservation controls in a deep sea modern environment an example from namibian slope sediments the luderitz upwelling cell is presently the most productive area of the benguela current system and abundant organic matter om accumulates on the adjacent slope sediments even at great water depth om from two cores taken on the slope and covering the last 280 kyear was analysed in terms of petroleum quality rock eval chemical features ftir eds and petrographic composition light microscopy and tem these data indicate that the om is more oxidized at 3606 m water depth than on the upper slope sediments 1029 m although the petroleum quality of the om throughout the deep water core remains surprisingly high for hemipelagic deep sea sediments hi 200 400 mg g the petroleum quality of om accumulated on the upper slope is consistently high hi averages 450 mg g two petrographic types of om are distinguishable from microscopic observation each ascribed to distinctive preservation mechanisms 1 granular amorphous om which dominates in the deep water core is formed by organo mineral aggregates aggregation appears to be the primary preservation mode at this depth although is quantitatively limited maximum toc value of 4 wt of bulk sediment obtained through this process the ultrastructure of the aggregates highlights an intimate association pattern between sedimentary om and clays 2 gel like nannoscopically amorphous om naom largely dominates at 1000 m water depth and contains sulfur thus early diagenetic sulfurization was probably involved in the preservation of this om but a contribution from the classical degradation recondensation pathway cannot be ruled out moreover selective preservation occurred at both sites but represents an insignificant part of the om organic fluxes mainly control the occurrence and extent of sulfurisation at both water depths by determining the redox conditions at the sea floor aggregate formation is limited by both organic and mineral fluxes at the lower slope whereas om supply is never limiting on the upper slope although consistently operating through time at both depths preservation by organo mineral association is limited by mineral availability and thus accounts for a relatively minor portion of the om accumulated on this organic rich slope in the case of large organic fluxes sulfurisation and or degradation recondensation is required to obtain toc contents above 4 wt of bulk sediment in the area

array observations of microseismic noise and the nature of h v in the mississippi embayment abstract ambient ground motion data were collected using phased seismic arrays in fall 2002 and spring 2007 within the mississippi embayment and at a single station external to the embayment these data allowed us to determine the wave field composition of ambient noise for understanding wave propagation mechanisms giving rise to spectral peaks using nakamura s h v technique ambient ground motions in the frequency band of 0 1 0 33 hz 10 3 sec period were dominated by spatially localized rayleigh and love wave microseisms generated by high ocean waves along the north american seaboard in the time periods of analysis seismic waves important in forming the h v peak near 4 sec period are composed of relatively high phase velocity rayleigh and love waves that convert to propagating homogeneous shear waves in the thick unconsolidated sediments of the embayment the h v resonant period is controlled by both constructive and destructive interference of these shear waves a simple relationship for the h v peak is given using a propagator matrix formulation that predicts the resonance frequency of a layered medium for surface wave motion at the base of the system the amplitude of the observed h v peak however does not give an accurate estimate of shear wave amplification because it depends on the slowness of the incident wave the inconsistency in estimated average shear wave velocities using the h v method and differential travel times of local earthquake sp phases in the mississippi embayment may be explained by misidentification of sp wave conversion points from deeper interfaces

predominance of stratified anoxic yangtze sea interrupted by short term oxygenation during the ordo silurian transition abstract the ordo silurian transition was a critical interval in geological history during which profound biotic climatic and oceanic changes occurred in order to explore the oceanic palaeoredox changes multiple geochemical proxies including ratios of s c fehr fet fep fehr and dop values are presented here from three sections wangjiawan western hubei sanjiaguan northern hunan and nanbazi northern guizhou across the ordo silurian boundary on the yangtze platform these palaeoredox data indicate a predominance of stratified anoxic ferruginous ocean on the yangtze block during this transition which was interrupted by a brief episode of oceanic oxygenation in the early hirnantian this oxygenation temporally coinciding with the end ordovician glaciation and global glacio eustatic sea level fall likely resulted from enhanced circulation of polar cold dense oxygen rich water onto the low latitude shelf the prior and subsequent longer term episodes of anoxic ocean particularly the later one which started in the late hirnantian occurred in parallel with the rapid climatic warming and sea level rise which could have slowed down oceanic circulation thereby enhancing oceanic stratification anoxia and organic preservation oceanic redox changes together with rapid climatic and sea level fluctuations were likely responsible for the stepwise massive demise of the ordo silurian biotic crisis

influence of water column anoxia on the burial and preservation of carbon and phosphorus in marine shales abstract organic p and organic c concentrations were measured in several well characterized phanerozoic marine shale sequences with the primary focus being the camp run member of the devonian mississippian new albany shale sequences were selected with close spatial association of bioturbated and laminated sediments which reflect deposition from oxic and anoxic waters respectively average organic c p mole ratios calculated from the data are 150 for bioturbated shales and 3900 for the laminated shales of the new albany differences in the extent and mechanisms of early diagenesis related to the oxygenation of waters at the sediment water interface can account for the c p ratios of buried organic matter low c p ratios of bioturbated sediments are attributed to 1 1 the increased ability of bacteria to store p in well oxygenated environments which leads to the production of low c p ratio bacterial biomass and 2 2 the extensive oxidation of sedimentary organic matter resulting in the formation of residual organic phases with low c p ratios high organic c p ratios of laminated sediments are explained by a combination of 1 1 the limited ability of bacteria to store p under anoxic conditions 2 2 extensive p regeneration from sedimentary organic matter 3 3 enhanced c preservation relative to the bioturbated shales it is also shown that relative to organic c laminated shales are not as effective a p sink as are bioturbated shales this provides a mechanism in anoxic environments for burying large quantities of organic matter without simultaneously sequestering the p needed to sustain further productivity

near real time near surface 3d seismic velocity and uncertainty models by wavefield gradiometry and neural network inversion of ambient seismic noisegradiometric wave equation inversion

marine incursion events in the late cretaceous songliao basin constraints from sulfur geochemistry records abstract songliao basin in ne china developed the most productive oilfield in the world sourced from terrestrial rocks the main source rock of the basin includes member 1 of the qingshankou k2qn1 and members 1 and 2 of the nenjiang formation k2nj1 2 however the exact reasons for the formation of the source rock especially the k2qn1 are still controversial former paleontological and organic geochemical research suggested that organic matter was deposited during marine incursion events of k2qn1 but further geochemical evidence is needed this paper explores the distinct sulfate levels that distinguish marine from fresh waters of the songliao paleo lake we undertook a systematic investigation the sulfur geochemistry of the sediments from top of member 4 of the quantou formation k1q4 to top of member 1 of the qingshankou k2qn1 the ratio of organic carbon to the pyrite sulfur toc pys proved the previously suggested saline conditions during the deposition of k2qn1 and the pyrite sulfur isotope indicated that marine incursion may not only have occurred for k2qn1 but also for top of k1q4 the exact time for the beginning of marine incursion is to be determined the marine incursion within k2qn1 is not strong and partially controlled by the fluctuation of paleo lake level the present study will be helpful for understanding the contribution of marine incursion events to the burial of organic carbon in the songliao paleo lake although further studies are still needed

reverse engineering mother nature shale sedimentology from an experimental perspective abstract experimental study of the sedimentology of shales can take a variety of forms at its simplest one can experiment with suspensions in a glass jar and try to understand their settling behavior or one can manipulate mud in a tank or bucket to gain insights into its rheology this approach was championed over a century ago by sorby and the insights gained can be quite profound more recently tank and settling tube experiments of animal sediment interactions compaction behavior and sediment unmixing via re suspension have proven to be highly informative in spite of their simplicity flumes can be used to obtain quantitative information about depositional and erosional parameters and to generate fundamental bedforms in flume experiments however it is of critical importance that the flume be designed in a way that flocculated materials move under shear stress conditions that would be reasonable in natural environments although much flume work on muds has been conducted by hydraulic engineers the transfer of that knowledge to sedimentology is hampered by the fact that engineers and sedimentologists are interested in different though not mutually exclusive products from such experiments engineers and hydrologists are commonly concerned with quantifying fluid flow properties whereas sedimentogists are particularly interested in the sedimentary products that result from a variety of flow conditions recent sedimentologically oriented flume studies have shown that muds can form deposits at flow velocities and shear stresses that would suffice to transport and deposit medium grained sand mud suspensions are prone to flocculation and the resulting floccules travel in bedload and form ripples that accrete into beds the latter finding suggests that many laminated shales were deposited from currents rather than by settling from slow moving or still water there are many other sedimentary features in shales that can potentially be reproduced in flume studies and in the future serve to provide a quantitative basis for shale sedimentology

wave enhanced sediment gravity flows and mud dispersal across continental shelves reappraising sediment transport processes operating in ancient mudstone successions recent studies of marine shelf sediment dispersal show that wave enhanced sediment gravity flows are widespread phenomena and can transport large volumes of fluid mud rapidly across low gradient shelves flow evolution is controlled by sediment supply seabed gradient and spatial distribution of wave energy at the seabed using existing flow models we predict that such flows in mud dominated sediments will develop a three part microstratigraphy produced by changing flow conditions beginning with wave induced turbulent resuspension then development of a wave enhanced sediment gravity flow prior to lutocline collapse and suspension settling petrographic examination of modern flow deposits collected from the eel shelf reveals that resultant beds possess a microstratigraphy consistent with our hypothesis a silt rich basal subunit with curved ripple laminae abruptly overlain by a subunit composed of continuous intercalated silt clay laminae and an upper clay rich drape analyses of beds from ancient mud rich outer shelf and basinal successions cleveland ironstone jurassic uk and mowry shale cretaceous united states show that they too contain beds with this three part organization suggesting that such flows were active in these ancient settings too recognition of these microstructures in these ancient mud dominated successions demonstrates that sediment in these settings was commonly reworked and transported advectively downslope by high energy events contrasting with previous interpretations of these units that deposition was dominated by quiescent suspension settling identification of these recognition criteria now allows the products of this newly recognized sediment dispersal mechanism to be identified in other shale dominated successions

the shallow elastic structure of the lunar crust new insights from seismic wavefield gradient analysis enigmatic lunar seismograms recorded during the apollo 17 mission in 1972 have so far precluded the identification of shear wave arrivals and hence the construction of a comprehensive elastic model of the shallow lunar subsurface here for the first time we extract shear wave information from the apollo active seismic data using a novel waveform analysis technique based on spatial seismic wavefield gradients the star like recording geometry of the active seismic experiment lends itself surprisingly well to compute spatial wavefield gradients and rotational ground motion as a function of time these observables which are new to seismic exploration in general allowed us to identify shear waves in the complex lunar seismograms and to derive a new model of seismic compressional and shear wave velocities in the shallow lunar crust critical to understand its lithology and constitution and its impact on other geophysical investigations of the moon s deep interior