the influence of fluid type on elastic wave velocity and attenuation in volcanic rocks abstract volcano seismic signatures are the convolution of source and path effects the source signature provides important information about the dynamic rock deformation and fluid resonance processes within the volcano but path effects are the result of the volcanic plumbing the edifice physical conditions and the complex geological structure complicating the inversion of seismic data further is the influence of fluid properties here we use ultrasonic experiments to understand the effect of variable fluid viscosity and bulk modulus on p wave attenuation and velocity for volcanic rocks from white island volcano whakaari new zealand our experimental conditions for high porosity ash tuff and low porosity lava resemble shallow and deep volcano facies respectively p wave velocity vp and quality factor qp increase with the viscosity and bulk modulus of the saturating fluid and decrease with porosity and fracture volume tuffs are highly sensitive to saturating fluid with variations in vp of up to 67 and qp of 383 vp and qp in fractured lavas are slightly less sensitive to fluids 24 and 296 respectively but vp can be used to identify lithology for these tuff vs lavas comparison of the experimental data with rock physics models suggests that squirt flow is the dominant attenuation mechanism for viscosities greater than that of water while scattering losses may be important in gas saturated rocks our results have significant implications for the interpretation of seismic tomography studies and for volcano hazard monitoring based on the characteristics of detected seismicity

the tindouf basin a marine refuge during the serpukhovian carboniferous mass extinction in the northwestern gondwana platform abstract several macrofaunas and microfossils of the carboniferous saharan basins have longer stratigraphic ranges than those of other basins in the western palaeotethys realm particularly in the tindouf basin morocco algeria foraminifers are particularly abundant and diverse in the serpukhovian and basal bashkirian compared to coeval basins and some taxa have longer ranges than in the neighbouring reggan and bechar basins although this effect is more marked compared to the western palaeotethyan assemblages in europe several rugose coral species are recorded from the early bashkirian that previously were considered to have disappeared in the serpukhovian the tindouf basin as one of the most western saharan basins in north africa shows the greatest stratigraphic ranges of taxa which diminish eastwards evidence for a mass extinction event during the serpukhovian in the tindouf basin has not been clearly recognized although a possible influence of glaciation is observed in the faunal diversity eustatic sea level changes were experienced in tindouf with the cyclic pattern of sedimentation but warm water ocean currents from the palaeoequator were able to maintain tropical conditions on the platform tectonics in the area led to emerging land masses and barriers and created a partly isolated basin in this sector of the western part of the sahara platform in northern gondwana the combination of those factors controlled the environmental conditions in the area allowing the persistence of the fauna for longer stratigraphic ranges than its equivalent counterparts in the western palaeotethys

fractal structure of spatial distribution of microfracturing in rock summary a constant stress fracture experiment of oshima granite was carried out at the confining pressure of 40mpa hypocentres of 2064 acoustic emissions were located during the experiment using the correlation integral we found that the spatial distribution of hypocentres of acoustic emission is a fractal and that the fractal dimension decreases with the evolution of rock fracturing the spatial distribution of earthquake s hypocentres reveals fractals ranging from regional to worldwide distribution if we extrapolate from laboratory measurements it is possible to predict the occurrence of large earthquakes by the decrease in the fractal dimension

astronomical metronome of geological consequence in pnas kent et al 1 describe a remarkable geochronologic correlation arising between the continental triassic jurassic newark basin strata of eastern north america and the time equivalent chinle formation of western north america that has far reaching consequences for geology and astronomy as follows in geology a reliable metronome in the geologic record with a sufficiently short repeat time would greatly enhance the resolving power of the geologic timescale astronomers recognized the potential importance of a dominant 405 ky cycle in earth s orbital eccentricity variation for supplying such a metronome 2 3 leading geologists to turn to the stratigraphic record of astronomically forced paleoclimate change to search for this cycle in fact one of the first geological studies to describe 405 ky scale stratigraphic cycling was on the triassic jurassic newark basin lacustrine strata 4 5 recovered in the national science foundation funded newark basin coring project in which each of the prominent 60 m thick mclaughlin cycles in the cored sequence was assigned a 412 885 ky periodicity based on a now legacy analytical astronomical solution bre74 ber78 6 7 since the 1990s there have been dozens of reports for strong 405 ky scale cycles in stratigraphic sequences from around the world that appear to bear out this astronomical calculation 8 however not one of these reports has presented incontrovertible support from independent geochronology that links specific 405 ky cycles identified by their order of appearance relative to the present day to those in the astronomical solution until now this has included the newark basin which besides the flood basalts at the top of the core series suffers from a lack of datable materials for example volcanic ashes that could help establish a numerical timescale for the core series in astronomy the 405 ky cycle in earth s orbital eccentricity variation is due to a periodic interaction between the orbital motions of venus planet 1 1email lhinnov at gmu edu 1 xref corresp 1 1

stratigraphy and sequence stratigraphy of the moscovian in the donets basin new results are presented on the stratigraphy based on fusulinids and palynomorphs and the sequence stratigraphy of the moscovian in the donets basin they have been developed by comparison of our observations on cross sections near artemovsk and the published coal mine logs of artemovsk geological survey the moscovian of the donets basin is equivalent to the uppermost westphalian b and the westphalian c and d of western europe in the donets basin the moscovian forms a second order sequence as in the moscow basin that can be subdivided into four third order sequences subdivided into fourth order sequences the upper bashkirian shows two fourth order sequences the vereian exhibits two fourth order sequences the kashirian shows four fourth order sequences the podolskian offers eight fourth order sequences the myatchkovian presents four fourth order sequences these sequences begin with an erosive base and show a succession of elementary sequences with fluvial sandstone coal seam limestone and deltaic facies the fluvial sandstone corresponds with an aggradation period the coal and the limestone with a transgressive period and the deltaic facies with a progradation period a decrease of the sandstone thickness and an increase of the marine deposits that are transgressive and regressive upwards are observed from the base to the top of sequences these fourth order sequences present a higher spatial amplitude than the third order sequence and obscure these sequences the second order sequence equivalent to the moscovian shows a lowstand system tract with more fluvial sandstone in the lower part of the vereian a transgressive system tract in the upper part of the vereian tsinskaya and kashirian a maximum flooding period during the podolskian and lower part of the myatchkovian with more marine facies and a highstand system tract in the upper part of the myatchkovian with more lagoonal and swampy palaeoenvironments the sequences are controlled by the regional tectonic subsidence in the graben and the uplift of the horsts and or by eustasy with either a plate tectonic or a glacial origin other investigations particularly radiometric dating will be useful for solving this problem

derivation of isotope ratios errors and error correlations for u pb geochronology using 205pb 235u 233u spiked isotope dilution thermal ionization mass spectrometric data a comprehensive treatment of the derivation of u pb isotope ratios and their corresponding uncertainties from isotope dilution thermal ionization mass spectrometric measurements is presented standard parametric statistical methods of error propagation are utilized to convolve uncertainties associated with instrumental mass fractionation tracer subtraction blank pb and u subtraction and initial common pb correction derivations include errors and error correlations for total sample u pb and pb isotope ratios including radiogenic and initial common pb for two and three dimensional isochron calculations radiogenic u pb and pb isotope ratios for concordia and radiogenic model age calculations and the propagation of model age errors from radiogenic isotope ratios

cyclothem digital correlation and biostratigraphy across the global moscovian kasimovian gzhelian stage boundary interval middle upper pennsylvanian in north america and eastern europe the long standing difficulty of correlating pennsylvanian strata among provincial faunal regions is resolved by effecting digital correlation of major glacial eustatic cyclothems that represent high stands when certain species achieved more global distribution than usual in the late moscovian early gzhelian late desmoinesian early virgilian succession in the midcontinent united states several major cyclothems are correlated by both conodont species in common and cyclothem scale with cyclothems in russia moscow basin and ukraine donets basin and the remaining cyclothems fit into the framework by position and scale in this way the suggested event marker for the global kasimovian gzhelian stage boundary first appearance of idiognathodus simulator is supported while possible event markers for the moscovian kasimovian boundary await further evaluation

pennsylvanian time scales and cycle periods geochronological results from central europe indicate that the duration of pennsylvanian time is only 19 m y compared to the harland et al and palmer estimates of 34 m y prior calculations of pennsylvanian cycle periods from the midcontinent of north america suggesting a fit with milankovitch orbital parameters may well be in errors as a consequence other mechanisms for possible eustatic sea level changes represented in those cycles are needed calculation of cycle periods of 100 ka or less lack precision in stratigraphic intervals representing ages characterized by error margins of millions of years thus cycle periods may be less reliable as an indicator of global process than previously considered particularly in rocks of paleozoic and early and middle mesozoic age

chronostratigraphy and paleoclimatology of the lodeve basin france evidence for a pan tropical aridification event across the carboniferous permian boundary abstract paleosols preserved within the carboniferous permian succession of the lodeve basin massif central france change stratigraphically from histosols to calcic vertisols and calcisols to gypsic vertisols and ultimately back to calcic vertisols and calcisols new high precision u pb zircon ages ca idtims for tuff beds within the lodeve and adjacent graissessac basins significantly revise the chronostratigraphy of these and correlated permian terrestrial basins of eastern euramerica under the newly revised chronostratigraphy presented here these stratigraphic changes in morphology indicate a substantial drying of paleoenvironments across the carboniferous permian boundary with a trend toward progressively more arid and seasonal climates through most of the early permian this newly realized chronology provides a paleoenvironmental and paleoclimatic timeline for eastern tropical pangea that is contemporaneous with similar records in western pangea and suggests pan tropical progressive climate change toward aridity and seasonality occurred from the late carboniferous through early permian

high precision zircon u pb geochronology of astronomically dated volcanic ash beds from the mediterranean miocene several orbitally tuned miocene sedimentary sequences around the mediterranean contain abundant intercalated volcanic ash beds these sequences provide the rare opportunity to directly compare radioisotopic dating methods with independent and accurate deposition ages derived from astrochronology we present a large data set n 16n 16 n 166n 166 of zircon u pb dates obtained by chemical abrasion isotope dilution thermal ionization mass spectrometry ca id tims techniques for ash beds from an almost continuous orbitally tuned messinian to langhian 6 2 15 4 ma sedimentary sequence exposed along the adriatic coast south of ancona italy we use this unique data set to evaluate 1 the accuracy of zircon u pb dates 2 the significance of initial intermediate daughter product disequilibria for zircon u pb geochronology of young rocks 3 the effect of prolonged pre eruption zircon crystallization and zircon recycling on u pb derived ash bed deposition ages and 4 discuss the implications for the intercalibration of radioisotope geochronometers and the calibration of the geologic time scale

coral reefs and growth dynamics of a low angle carboniferous platform records from tianlin southern china abstract metazoan reef building receded globally during the carboniferous after the late devonian extinction events shallow water bioconstructions were generally small and scarce and corals played a minor role in their construction however in southern china one large 50 m high and three small 6 16 m high coral reefs dating from the late visean serpukhovian have recently been discovered in two localities in guangxi to understand the occurrence of these coral reefs and to constrain the factors that controlled their growth three sections around langping guangxi were measured and selected samples were analysed using petrography biostratigraphy and chemostratigraphy the depositional environment of these exceptional mississippian reefs was interpreted as a low angle platform 1 2 5 recording oligotrophic conditions and normal salinity the three small reefs have grown around the fair weather wave base whereas the large coral reef has grown in a deeper environment between the fair weather and storm wave base during carboniferous the global temporal reef distribution can be partly ascribed to paleoclimate changes however in southern china the growth of extended mississippian coral reefs is restricted to a short time window the late visean serpukhovian which coincides with high amplitude and high frequency sea level fluctuations most likely related to glacial pulses recent studies revealed that several rugose coral species survived the mid carboniferous glaciation event thanks to the persistence of warm water ocean currents maintaining tropical conditions on the platform due to the scarcity of extended coral reefs elsewhere it cannot be excluded that tianlin provided an ecological refuge for corals related to oceanic currents another potential favorable factor could be the mid ramp depositional setting the deep water platform areas could potentially provide more stable conditions less affected by global stress events however the deep reef refugia hypothesis remains debatable as only very few studies have explored its validity at the community level even if the causes of the occurrence of an extended coral reef in southern china cannot be fully constrained the existence of this large coral framework in the late visean serpukhovian provides additional evidence that coral communities did build reefs after the late devonian extinction events

spectral analysis and modeling of microcyclostratigraphy in late paleozoic glaciogenic rhythmites parana basin brazil we investigate the depositional time scale of lithological couplets fine sandstone siltstone siltstone mudstone from two distinctive outcrops of permo carboniferous glacial rhythmites in the itarare group parana basin brazil resolving the fundamental issue of time scale for these rhythmites is important in light of recent evidence for paleosecular variation measured in these sequences spectral analysis and tuning of high resolution gray scale scans of sediment core microstratigraphy which comprises pervasive laminations reveal a comparable spectral content at both localities with a frequency suite interpreted as that of short term climate variability of recent and modern times this evidence for decadal to centennial scale deposition of these lithological couplets is discussed in light of the varvic character i e annual time scale that was previously assumed for the rhythmites

neoarchean and paleoproterozoic events in the minnesota river valley subprovince with implications for southern superior craton evolution and correlation abstract the lithologic diversity and protracted geologic history of the minnesota river valley mrv gneiss terrane at the southern margin of the archean superior province provide key perspectives on the growth and modification of this craton innovations in geochronology specifically the application of the chemical abrasion technique to remove pb loss domains in zircon and the tandem use of in situ geochemistry and precise isotope dilution age analysis for establishing the petrologic context of radioisotopic ages are yielding new insights into these old rocks first u pb geochronology on a variety of plutonic to mesoscale intrusive rocks from the morton and montevideo blocks of the mrv provide precise constraints on the neoarchean 2603 2584 ma sacred heart orogeny which sutured the mesoarchean gneisses of the mrv to the southern margin of the superior craton in an episode of contractional deformation high grade metamorphism and voluminous plutonism second we report the first radioisotopic age constraints on the st leo and taunton belts of greenstone and supracrustal rocks within the yellow medicine shear zone an inferred lithosphere scale structure juxtaposed between the morton and montevideo gneisses titanite from a metadiorite intrusion into the st leo belt yields igneous 2539 ma and metamorphic 2510 ma ages confirming the archean provenance of the host greenstones and revealing a latest neoarchean episode of magmatism and deformation focused along and within the shear zone third a new 1781 ma u pb zircon age for one of a number of small granitic plugs in the southern montevideo block confirms its correlation to the more voluminous east central minnesota batholith and its origin in the yavapai orogeny again later magmatism was focused along the yellow medicine shear zone suggesting the lithosphere scale significance of that structure this more resolved history for the neoarchean to proterozoic evolution of the southern superior craton provides new opportunities to test archean craton correlations and reconstructions including links to the wyoming and slave cratons

julia radar studies of equatorial spread f this paper presents coherent scatter radar observations of plasma irregularities in the equatorial f region ionosphere made with the julia jicamarca unattended long term studies of the ionosphere and atmosphere radar and discusses model equations and simulations pertinent to their interpretation the data set shows that bottom type and bottomside scattering layers are prevalent throughout solar minimum equinox bottom type layers are undifferentiated and relatively weak layers confined to a narrow range of altitudes falling within regions of the ionosphere driven by the e region dynamo these layers are often precursors to large scale radar plumes as well as to bottomside layers which are broader more structured and more intense layers than the bottom type variety bottomside layers are the source of intermediate scale plasma depletions that can ascend and penetrate through to the topside fluid simulations of the collisional interchange instability suggest that dynamo theory explains why one kind of layer emerges at a given time and altitude

u pb dates of paleosols constraints on late paleozoic cycle durations and boundary ages u pb ages of paleosol samples from cyclothemic sections in the sacramento mountains of new mexico and the permian basin of west texas bracket the pennsylvanian permian and carboniferous permian boundaries linear interpolation and extrapolation to boundaries are accomplished by using cyclothems as periodic subdivisions the carboniferous permian boundary is 301 2 ma 2 the pennsylvanian permian boundary is 302 2 4 2 and the missourian virgilian boundary is 307 3 ma 2 these ages are within the uncertainties of recent estimates for the boundaries but are significantly more precise the average cycle duration for this upper pennsylvanian and lower permian interval is 143 64 ka 2 within the uncertainty of the 100 k y cycle that dominated pleistocene sea level history this new estimate which is much shorter than those published previously suggests that the pennsylvanian and early permian cyclothems may have been driven in a manner similar to that which caused glacio eustatic cycles of the pleistocene

origin of the pennsylvanian coal bearing cyclothems of north america past controversy about the tectonic or eustatic origin of pennsylvanian cyclothems is resolved by regional basin subsidence analysis global paleoclimate paleogeography and plate tectonic evolution differences between marine carbonate kansas type cyclothems of the northern midcontinent and nonmarine clastic appalachian type cyclothems of the eastern united states are controlled by laterally changing flexural deformation during plate accretion into a supercontinent coupled with superposed glacial eustasy kansas type cyclothems accumulated on a relatively stable platform affected only moderately by collision tectonics of north american margins these cycles are eustatic characterized by a periodicity comparable to milankovitch orbital parameters appalachian type cyclothems accumulated in response to episodic thrust loading during plate collisions that developed a series of flexurally deformed wide and shallow resurgent foreland basins this resurgent foreland basin evolution during paleozoic time increased crustal rigidity in the appalachians thus yoking the appalachian and illinois basins during pennsylvanian time with each thrust load foreland basin deepening favored transgressive cyclothem facies which changed to a regressive facies because sediment yield increased as denudation rates increased off uplifted orogens illinois type cyclothems are intermediate between the two end member processes of flexural tectonics and glacial eustasy characterizing appalachian type and kansas type cyclothems respectively thus the pennsylvanian coal bearing cyclothems of north america owe their origin to the remarkable coincidence of supercontinent development concomitant glaciation and eustatic sea level change and associated episodic thrust loading and foreland basin subsidence of small magnitude on progressively more rigid crust

failure zone development in andesite as observed from acoustic emission locations and velocity changes three dimensional 3 d locations of acoustic emissions ae and p wave velocity anisotropy were investigated to analyse the failure zone development in two yugawara andesites the results were obtained during the deformation of rock under incremental loading and short duration creep regimes at a confining pressure of 40 mpa creep tests were carried out at a constant differential stress of about 90 95 of short term fracture strength of andesites for the single and two stage creep experiments in both the experiments the ae activity during loading was mostly confined to two region where ae hypocentres concentrated near the cylindrical surface of the rock prior to fault nucleation the localized zone of microcracks attained a spheroidal shape in one sample and planar shape in the other p wave velocity anisotropy increased to 44 as final failure approached in the rock the loading rate and the magnitude of creep stress were found to have a profound influence on the details of failure zone development and times of failure of the rocks studied

the donbas foldbelt its relationships with the uninverted donets segment of the dniepr donets basin ukraine abstract the donbas foldbelt df is a thrust faulted and folded inverted segment of the dniepr donets basin ddb it lies between the scythian and east european platforms north of the black sea and is conventionally thought to have formed in the early permian as part of the late palaeozoic hercynian uralian orogenic frame of cratonic europe the ddb itself formed as a result of late devonian intracratonic rifting and contains a thick up to 22 km late palaeozoic and mesozoic sedimentary succession the deformed strata preserved at the erosional surface of the df are mainly carboniferous the donets segment of the ddb displays mild inversion structures that are transitional to those in the df recently acquired regional seismic reflection data in the donets part of the ddb allow these structures to be imaged in the subsurface for the first time a widespread early permian unconformity occurring throughout the ddb is much more pronounced on its southern margin than on its northern one and appears to be related to profound uplift of the southern flank of the basin and the neighbouring ukrainian shield rather than to crustal shortening faults associated with the early permian unconformity are extensional in style gentle folds and other local structures in the southern flank and axis of the donets segment are mainly located in areas associated with early permian salt movements no significant development of compressional structures of early permian age can be seen in the seismic data where it is available in contrast there is ample evidence of latest cretaceous earliest tertiary compressional deformation in the ddb including the subsurface expression of structures along strike of the main folds of the df a review of geological evidence in the df also indicates that the main period of shortening that can be definitely constrained in time is latest cretaceous earliest tertiary the eastern part of the df records intense late triassic aged cimmerian deformation but none of clearly permian age it is tentatively concluded that the main phases of trans compressional tectonics forming the df were cimmerian and especially alpine rather than hercynian uralian

middle permian u pb zircon ages of the glacial deposits of the atkan formation ayan yuryakh anticlinorium magadan province ne russia their significance for global climatic interpretations abstract the atkan formation in the ayan yuryakh anticlinorium magadan province northeastern russia is of great interest because of the occurrence of deposits of apparent dropstones and ice rafted debris that have been previously interpreted as glacial two high precision u pb zircon ages one for an intercalated volcanic tuff 262 5 0 2 ma and the other for a boulder clast 269 8 0 1 ma within a diamictite of the atkan formation constrain the age of the atkan formation as guadalupian middle permian sedimentologic study of the atkan formation casts doubt on the glacial nature of the diamictites deposition of rocks of the atkan formation temporally correlates with the capitanian interglacial event in the southern hemisphere that recently was calibrated with high precision ca tims the previously proposed climate proxy record based upon warm water foraminifera which corresponds closely to global climate fluctuations is compared with the glacial record of eastern australia and indicates that the capitanian was a time of globally warm climate the sedimentology of atkan formation the record of diversification of both fusulinids and rugosa corals global sea water temperature and sea level fluctuations agree well with high latitude paleoclimate records in northeastern russia and eastern australia major components of the atkan formation the volcanic rocks are syngenetic with the sedimentation process the volcanic activity in the nearby regions during middle late permian was quite extensive

substorm triggering by new plasma intrusion incoherent scatter radar observations received 4 december 2009 revised 16 march 2010 accepted 30 march 2010 published 27 july 2010 1 in the companion paper we identified a repeatable sequence of events leading to substorm onset in themis all sky imager observations enhanced flows bring new plasma into the plasma sheet the new plasma then moves earthward as a flow channel bringing it to the near earth plasma sheet and where it produces onset instability new plasma entering the dusk dawn convection cell drifts equatorward and eastward and then around the harang reversal leading to pre midnight near and post midnight onset here we present evidence supporting this sequence using incoherent scatter radar isr ionospheric observations using the sondrestrom isr we find that enhanced flows of new plasma commonly enter the plasma sheet from the polar cap 8 min prior to onset these flows are related to poleward boundary intensification signatures consistent with the inferences from the imagers using the poker flat isr pfisr we find that shortly before onset enhanced westward flows reach the subauroral polarization streams saps region equatorward of the harang reversal dusk cell onsets or enhanced eastward flows enter the onset region from the poleward direction dawn cell onset pfisr proton precipitation signatures are consistent with the possibility that the enhanced flows consist of reduced entropy plasma sheet plasma and that onset occurs poleward of much of the enhanced saps flow dusk cell onsets or equatorward of the enhanced eastward flows dawn cell onsets consistency with reduced entropy plasma is seen only within the enhanced flows leading us to suggest that intrusion of low entropy plasma may alter the radial gradient of entropy toward onset instability

high resolution stratigraphy and zircon u pb geochronology of the middle triassic buchenstein formation dolomites northern italy precession forcing of hemipelagic carbonate sedimentation and calibration of the anisian ladinian boundary interval orbitally forced cyclic variations in sedimentary sequences provide evidence for short term fluctuations of earth climate and a tool for high resolution timescale calibration we here present stratigraphic and geochronological evidence for precession forcing in middle triassic hemipelagic limestones of the buchenstein formation dolomites northern italy high resolution stratigraphy of several correlative sections of the buchenstein formation documents a coherent cycle pattern isotope dilution thermal ionization mass spectrometry zircon u pb geochronology of tuffs bracketing the cyclic interval reveals an average cycle duration of 18 5 2 1 kyr consistent with a shorter climatic precession cycle in the middle triassic compared with today this suggests a predominantly precession controlled climate in this low latitude setting of the western tethys and allows high precision calibration of the anisian ladinian boundary interval from integrating cyclostratigraphic and u pb geochronological constraints our best estimate for the age of the anisian ladinian boundary is 241 464 0 064 0 097 0 28 ma we also provide precise estimates for lithostratigraphic boundaries biostratigraphic markers and magnetic reversals within the boundary interval stratigraphic intervals with elevated sedimentation rate record a sub milankovitch signal that may be equivalent to patterns in adjacent carbonate platforms such as the latemar platform the origin of this sub milankovitch signal remains unknown but highlights the potential to investigate shorter term climatic variations in mesozoic sedimentary sequences supplementary material isotope dilution thermal ionization mass spectrometry u pb and laser ablation inductively coupled plasma mass spectrometry trace element data tables as well as the results of the bayesian age modelling are available at https doi org 10 6084 m9 figshare c 3861817

sea level curve for pennsylvanian eustatic marine transgressive regressive depositional cycles along midcontinent outcrop belt north america at least 55 cycles of marine inundation and withdrawal are recognized in the mid desmoinesian to mid virgilian midcontinent outcrop sequence in north america they range from widespread major cycles classic cyclothems with deep water facies extending across the northern shelf through intermediate cycles persisting as marine horizons across the shelf to minor cycles developed on the lower shelf or as parts of major cycles biostratigraphic differentiation of the cycles should establish interbasinal correlation on a scale fine enough to allow evaluation of differential tectonics and sedimentation sequential groupings of cycles are more irregular than proposed megacyclothems or mesothems but they may be obscured by the distinctness of the major cyclothems estimates of cycle periods range from about 40 to 120 x 10 sup 3 yr for the minor cycles up to about 235 to 400 x 10 sup 3 yr for the major cyclothems the range for all cycles corresponds well to the range of periods of earth s orbital parameters that constitute the milankovitch insolation theory for the pleistocene ice ages and it further supports gondwanan glacial control for the pennsylvanian cycles even though the dominant period of the major pennsylvanian cyclothems is up to four times longer than the dominant 100 000 yr period inmore the pleistocene the shapes of both curves display rapid marine transgression rapid melting of ice caps and slow interrupted regression slow buildup of ice caps which suggest similar linkages between the climatic effects of the orbital parameters and ice cap formation and melting at the two different scales widely separated in time 28 references 3 figures less

concurrent observations at the magnetic equator of small scale irregularities and large scale depletions associated with equatorial spread f in 2014 an all sky imager asi and an advanced modular incoherent scatter radar consisting of 14 panels amisr 14 system were installed at the jicamarca radio observatory the asi measures airglow depletions associated with large scale equatorial spread f irregularities 10 500 km while amisr 14 detects small scale irregularities 0 34 m this study presents simultaneous observations of equatorial spread f esf irregularities at 50 200 km scale sizes using the all sky imager at 3 m scale sizes using the julia jicamarca unattended long term investigations of the ionosphere and atmosphere radar and at 0 34 m scales using the amisr 14 radar we compare data from the three instruments on the night of 20 21 august 2014 by locating the radar scattering volume in the optical images during this night no topside plumes were observed and we only compare with bottomside esf amisr 14 had five beams perpendicular to the magnetic field covering 200 km in the east west direction at 250 km altitude comparing the radar data with zenith asi measurements we found that most of the echoes occur on the western wall of the depletions with fewer echoes observed the eastern wall and center contrary to previous comparisons of topside plumes that showed most of the echoes in the center of depleted regions we attribute these differences to the occurrence of irregularities produced at submeter scales by the lower hybrid drift instability comparisons of the asi observations with julia images show similar results to those found in the amisr 14 and asi comparison

fracturing of volcanic systems experimental insights into pre eruptive conditions conditions for fracturing are a primary control on the behaviour of volcanic systems especially during the approach to eruption we here present the results of deformation experiments under simulated volcanic conditions on a porhyritic andesite from ancestral mount shasta andesite was chosen as a representative material because it is common at subduction zone volcanoes among both erupted products and country rock we deformed the lava in tension and triaxial compression tests at strain rates of 10 5 s 1 confining pressures from 0 to 50 mpa and temperatures up to 900 degrees c we also concurrently recorded acoustic emissions ae in order to monitor cracking activity the results show that deformation behaviour changes significantly in the temperature range 600 750 degrees c thus as temperatures increased across this interval the tensile fracture toughness increased from 2 5 0 5 mpa m 1 2 to 3 5 1 mpa m 1 2 the compressive strength decreased from 110 30 mpa to 55 35 mpa at 900 degrees c and the corresponding young s modulus decreased from 20 4 gpa to 6 4 gpa the changes occur when the deformation of the sample changes from elastic brittle to brittle ductile behaviour which we attribute to the blunting of crack tips due to melting of the glass phase and enhanced crystal plasticity at high temperature ae activity was observed in all experiments indicating that earthquakes can be generated not only in country rock but also in hot magma such as may be found in lava domes and at the margins of magma conduits in addition the trends in accelerating ae event rates before sample failure were comparable to those seen in earthquakes before some volcanic eruptions and a minimum in the seismic b value coincided with sample failure applied to volcanic systems the results suggest that 1 andesite strength and elasticity will not be affected by temperature or pressure beyond similar to 10 100 m from active magma 2 before eruptions fractures propagate preferentially through weaker horizons in a mechanically heterogeneous volcano and 3 volcanic rocks have characteristic seismic b values that are perturbed during the approach to bulk failure each of these conditions provides quantitative constraints on models for seismic precursors to eruption or intrusion c 2009 elsevier b v all rights reserved

positive feedback fracture process induced by nonuniform high pressure water flow in dilatant granite during forced water infiltration into a dry granite rock in the dilatant state migration of a water front and a clear positive feedback between acoustic activity and water flow into microcracks were revealed by means of ae hypocenter locations and velocity tomography water was injected into a cylindrical granite sample subjected to 40 mpa confining pressure and constant axial stress equal to about 70 of short term dry strength the injection water pressure was held constant at 17 mpa until failure occurred soon after water injection into the bottom end of the sample ae hypocenters began near the bottom end subsequently they moved up with a strong preference for the region where a weak concentration of ae events had been observed during a steady state creep stage before the water injection the p wave velocity structure was determined in the section parallel to the loading axis and crossing the cluster of ae hypocenters the velocity structure reconstructed by seismic tomography showed a nonsymmetric distribution of the velocity with regard to the loading axis during the injection the strong concentration of ae hypocenters suggests that water flow channels are preferentially formed in a very limited region in the dilatant rock the concentration of ae events and formation of these water channels marks a positive feedback process in which the local strength of the rock is reduced by the decrease of the effective confining pressure caused by increasing pore pressure which in turn triggers more microfracturing

climatic vs tectonic controls on peat accretion in non marine setting an example from the žacleř formation yeadonian bolsovian in the intra sudetic basin czech republic abstract the acle coalfield in the western part of the intra sudetic basin is an example of coal accumulation in an alluvial valley deposited under a long term 3 m y stable tectonic regime with climatic oscillations possibly operating on several time scales the resulting sedimentary record about 600 m thick encompasses about 60 coal bearing cycles formed in a relatively small and localized part of the valley whereas elsewhere a higher clastic input and or lower rate of subsidence resulted in deposition of strata with very little coal available data suggest that tectonics produced accommodation for sediments and via changes in topography and or size of the source area affected the volume and dispersal patterns of clastic material transported to the depocentre areas with long term tectonic stability were suitable places for recognition of climatic signals in the sedimentary record modified by the intensity of local clastic input climatic fluctuations generated coal bearing cycles probably through a variable intensity of precipitation which affected the density of vegetation cover across the landscape along with evaporation and groundwater table these factors influenced the intensity of chemical weathering and hence regulated the volume and composition of clastics delivered to the depocentre this in turn resulted in alternation of short periods of bedload dominated deposition during the seasonally dry part of the cycle with periods of dominantly suspended load and organic peat deposition during the more humid everwet part of the cycle estimated duration of the basic cycles 46 k y approximates the orbitally driven axial tilt cyclicity basic cycles are arranged into two larger scale cyclic patterns lasting for 270 k y and 1 5 m y respectively which broadly correspond with the timing of glacial maxima and minima inferred from high latitude glacial deposits of gondwanan basins all the coals of the acle coalfield display similar petrographic composition dominated by collotelinite and field observations as well as detailed petrographic study show that they formed in planar rheotrophic peat swamps where long lasting peat accretion was episodically interrupted only by major floods on a century to millennial scale

aulacogens and aulacogeosynclines regularities in setting and evolution abstract aulacogens and aulacogeosynclinal zones represent intra continental palaeorifts and inverted palaeorifts they were formed in the process of the break up of continents during the late proterozoic inversion of such basins occurred variably during the baikalian caledonian hercynian and alpine orogenic cycles in response to the build up of intraplate compressional stresses emanating from orogenic belts aulacogens were first recognized on the stable russian platform where they correspond to linear graben type depressions filled with proterozoic sediments often buried beneath a thick cover of palaeozoic and younger sediments some aulacogens have experienced a short period of reactivation during the palaeozoic aulacogeosynclines differ from the genetically related aulacogens by their greater dimensions and the amount of lithospheric extension that can go to the extent of opening of small ocean basins consequently they are characterized by a greater degree of destruction of the continental crust the depth of subsidence and the complexity of their post rift development which commonly terminates with their compressional deformation giving rise to the development of intracontinental linear folded and thrusted structures frequently associated with low grade metamorphism and small intrusions many ancient platforms are characterized by aulacogens metaplatforms are dissected by aulacogens and aulacogeosynclines whereas geosynclinal troughs are the precursors of geosynclinal mobil belts aulacogens aulacogeosynclines and geosynclinal troughs represent a group of negative linear structures which are characterized by an increasing degree of crustal destruction during rifting processes and increasing mobility during lithospheric contraction

nature and timing of late mississippian to mid pennsylvanian glacio eustatic sea level changes of the pennine basin uk the pennine basin of northern england contains a comparatively complete serpukhovian moscovian succession characterized by high resolution ammonoid zonation and cyclic paralic sedimentation two new isotope dilution thermal ionization mass spectrometry zircon ages from a bentonite deposited during the arnsbergian mid serpukhovian regional substage and tonstein of earliest bolsovian early moscovian regional substage have been determined the weighted mean 206 pb 238 u ages of 328 34 0 55 and 314 37 0 53 ma total uncertainty respectively require modification of the time scale for the western europe regional chronostratigraphy the areal extent of acme ammonoid facies is used as a proxy for the magnitude of 47 discrete flooding events incised valleys major sequence boundaries are used as a proxy for the magnitude of sea level falls the frequency of these events in the light of the new radiometric dating indicates the following 1 there is temporal coincidence between major glaciations in gondwana and phases of increased frequency of sequence boundaries in the pennine basin 2 high amplitude flooding surfaces have an average frequency of c 400 ka 3 average cycle durations during the pendleian early arnsbergian and chokierian bolsovian of c 111 and c 150 ka respectively reflect short duration eccentricities 4 multiple flooding surfaces with the same ammonoid assemblages may equate with sub 100 ka precession or obliquity frequencies supplementary material u pb method description and data procedure for the calculation of the areal extent of marine bands and tables showing a full listing of biostratigraphical data used in the study are available at www geolsoc org uk sup18505

stratigraphic distribution of macerals and biomarkers in the donets basin implications for paleoecology paleoclimatology and eustacy abstract more than one hundred and thirty coal seams and coaly layers occur in the donets basin donbas twenty eight 52 samples of them ranging in age from serpukhovian late mississipian to gzhelian late pennsylvanian 33 clastics and three limestones were studied in terms of maceral composition sulphur contents and biomarker distribution diterpanes are used to estimate the contribution of different groups of plants and the height of the water table in the swamp hopanes are a measure of bacterial activity in the peat and steranes indicate the relative input of wood and algae stratigraphic trends in these parameters are discussed in relation to paleoenvironment climatic changes and eustacy a tropical climate prevailed in the donbas from serpukhovian to kasimovian times nevertheless periods with drier and wetter conditions can be distinguished based on maceral and biomarker data relatively dry conditions are observed during serpukhovian and vereian times whereas wetter climates with a maximum of coal deposition occurred during the late bashkirian most of the moscovian and the earliest kasimovian no economic coal seams are hosted in upper kasimovian and gzhelian deposits a result of a change to an arid climate our data also suggest climatic changes during sequences of different order for the second order third order and fourth order sequences relatively dry or wet conditions occurred during coal deposition in the lowstand systems tract an intermediate climate during the transgressive systems tract and the maximum flooding and a wet climate during the highstand systems tract the results for high frequency sequences support the cecil s paleoclimatic model an intermediate paleoclimate during lst sandstone and levee siltstone a wet climate during early tst coal and a dry climate during late tst limestone mfs claystone and hst deltaic siltstone coals deposited during maximum flooding periods are more enriched in c27 steranes derived from algae and contain lower proportions of c29 steranes derived from the wood of higher plants

structural features and evolution of the dniepr donets basin ukraine from regional seismic reflection profiles abstract a set of regional multichannel seismic reflection profiles crossing the dniepr donets dd basin in ukraine 100 200 km long and with a spacing of 10 15 km along strike illuminates the structure of the whole sedimentary cover the rift filled with pre and syn rift devonian sequences and overlain with post rift carboniferous permian mesozoic and palaeogene fill is clearly seen on all sections a basement layer previously identified as a riphean rift succession by refraction seismic studies constitutes in the main strata of the devonian and early carboniferous successions the structure of the rift is characterised by large scale rotational fault blocks and half grabens carried by basin parallel to normal marginal faults or by major horst blocks the total thickness of the devonian and younger succession is up to 19 km in the study area post rift carboniferous and mesozoic sediments cover the rift flanks and increase in thickness towards the rift axis and to the southeast the cumulative thickness of the carboniferous succession alone reaches 11 km with the maximum depth of their base at about 15 km major post rift tectonic events took place at the end of early visean in the middle of serpukhovian in permian times and between the mesozoic and cenozoic tectonic reactivations during carboniferous and early permian times were most pronounced in the southeastern part of the dd basin while they were least pronounced in the northwestern part of the basin merging with the pripyat trough where they are barely observed the most active development of salt structures and stocks corresponds with the periods of tectonic reactivation

hypocenter distribution and focal mechanism of ae events during two stress stage creep in yugawara andesite more than a thousand acoustic emission ae hypocenters were determined in a cylindrical andesite specimen under two stage uniaxial creep at stresses of 204 and 214 mpa strains were monitored for 6 peripheral points at the middle part of the cylindrical specimen s wall the strain data indicate gradual increase of nonuniform deformation during steady creep and strong intensification of the nonuniformity during acceleration creep and therefore biased stress distribution within the specimen the correlation between dilatant strain and ae hypocenters was investigated for whether or not tensile cracks emit ae the region with high ae activity shows only a small dilatant strain this negative correlation between ae and the dilatant region may eliminate tensile cracks as possible ae sources a composite focal mechanism solution of local ae events covering a wide solid angle of the focal hemisphere indicates that shear fractures emit ae waves the direction of the compressional axis in this solution shows a significant deviation from that inferred from the applied external force suggesting that the local stress field is governed by preexisting weak zones that are presumably produced by tensile cracks within the specimen ae hypocenters tended to form clusters during steady creep under the constant compressional stress during acceleration creep caused by a small step increase of the external stress the preceding clusters disappeared while a new cluster appeared in an incipient fault plane this suggests that changes in seismicity pattern such as migrations or quiescences of swarm important clues for earthquake predictions may be caused by an instantaneous change in the tectonic stress levels

from marine bands to hybrid flows sedimentology of a mississippian black shale this study was funded by the natural environment research council nerc grant no ne l002493 1 within the central england training alliance centa consortium the study received case funding from the british geological survey nick riley carboniferous limited is thanked for sharing his expertise and assistance charlotte watts is thanked for providing field assistance nick marsh tom knott cheryl haidon and annika burns are thanked for offering expertise and laboratory assistance pete sadler university of california is thanked for compilation and provision of the background sediment accumulation rate dataset we thank all reviewers editor peir pufahl and elaine richardson editorial office for their valuable comments and advice which have significantly improved this manuscript

optical observations of the growth and day to day variability of equatorial plasma bubbles 1 a new narrow field ionospheric imaging system the portable ionospheric camera and small scale observatory has been installed at the cerro tololo inter american observatory near la serena chile geographic 30 17 s 289 19 e geomagnetic 16 72 s 0 42 e we present observations of the naturally occurring nightglow emission at 630 0 nm on three consecutive nights demonstrating the day to day variability in the occurrence of equatorial plasma bubbles or depletions on two nights large scale undulations with a wavelength on the order of 300 600 km are observed in the emission regions magnetically connected to the bottomside of the equatorial f layer we demonstrate that at each crest of these large scale waves zero one or multiple depletions may grow thus the presence of a large scale wave on the bottomside alone is not sufficient for irregularity growth this variability is presumably due to the presence or lack of small scale seed waves or some other mechanism needed to increase the instability growth rate past the critical threshold

high precision u pb zircon ca id tims dates from western european late visean bentonites three new u pb zircon chemical abrasion isotope dilution thermal ionization mass spectrometry dates obtained from late visean belgian bentonites are reported and are used to estimate the periodicity of early warnantian shallowing upwards carbonate parasequences that are interbedded with the dated bentonites early warnantian parasequences exhibit mean cycle periodicity values that are consistent with the c 100 ka milankovitch cycle which is the dominant milankovitch frequency recognized from recent pleistocene glacial records and thus strengthen the arguments for 1 these sedimentary cycles being of glacio eustatic origin and 2 the initiation of the main phase of late palaeozoic glaciation before the start of or during earliest warnantian times the new dates also provide additional high precision age constraints for the improved calibration of the mississippian time scale using the new dates the stratigraphical age of the clyde plateau volcanic formation midland valley of scotland is revised from holkerian to early asbian supplementary material u pb zircon ca id tims data tables and the method of the mean cycle periodicity calculations are available at www geolsoc org uk sup18747

fracturing process of granite inferred from measurements of spatial and temporal variations in velocity during triaxial deformations fracturing in fine grained homogeneous granite during triaxial deformation was investigated by measuring the spatial and temporal variations of elastic wave velocities velocities along 20 ray paths were measured with 12 piezoelectric transducers attached to a sample under confining pressures up to 400 mpa systematic velocity differences observed among the 20 paths apparently indicate the formation of a dilatant region near the surface of a sample the damaged region formed near the surface due to asymmetric development of dilatancy seemed to play an important role in controlling ultimate failure no evidence of the formation of a crack concentration zone adjacent to the ultimate fracture plane could be found before failure insofar as could be estimated from the velocity variations of elastic waves propagating along its plane however a highly concentrated region of cracks in which the fracture nucleated was generated in the damaged region at stresses of more than 97 99 of the ultimate strength in all the specimens based on tomographic images computed using an algebraic reconstruction technique the elastic waves were strongly affected by the damaged region even under the high confining pressures at which cracks are considered to close

self consistent modeling of equatorial dawn density depletions with sami3 1 large scale dawn density depletions in the equatorial ionosphere have been observed by instruments on the stpsat1 and champ satellites the naval research laboratory nrl ionosphere model sami3 sami3 is also a model of the ionosphere is used to study this new phenomenon using a self consistent electric field two empirical horizontal wind models hwm are used in the simulation study hwm93 and hwm07 dawn density depletions are found using hwm07 but not with hwm93 the cause of the depletions is a post midnight enhancement of the eastward electric field that generates an upward plasma drift this drift lifts low density plasma to high altitudes i e 600 km we compare our model results to remote sensing data and to in situ satellite data

walchian conifers from the mid late pennsylvanian conemaugh group in the appalachian basin stratigraphic and depositional context and paleoclimatic significance abstract walchian conifers are indicators of seasonally dry habitats of the euramerican subtropics and tropics and are of considerable value in tracking both short term and long term pennsylvanian permian paleoclimatic changes in central pangea walchian conifer macrofossils first appeared in north america during the middle pennsylvanian but are rare in central pangean coal basins until the permian an abrupt climate change occurred near the desmoinesian missourian boundary that was characterized by global warming stronger seasonality and shorter wet phases this change coincided with the regional extinction of most tree lycopsids and the appearance of widespread high chroma calcic vertisols and aridisols only four occurrences of walchia have been reported from the pennsylvanian of the appalachian basin 1 7 11 mine of eastern ohio 2 rennersville in southwest pennsylvania and 3 charleston and 4 cedar run both in southern west virginia this paper uses recently acquired outcrop data to more fully document and reevaluate the depositional and stratigraphic context of the west virginia assemblages and their paleoclimatic and paleogeographic implications the cedar run walchia assemblage occurs in olive mudshale of an abandoned fluvial channel fill 15 8 16 9 m above the base of the ames limestone indicating an early virgilian age it consists of compressions and impressions of branches and branchlets of walchia lepidophylloides cordaites and rare neuropteroid pinnules the channel fill at this location is a component of the grafton sandstone incised valley fill previously described from the study area correlation of paleosol bounded marine cored cyclothems in the study area with their nonmarine cyclothem equivalents at charleston west virginia indicates the walchia previously reported at the mahoning coal horizon occurs between the brush creek and bakerstown coals and is therefore missourian not late desmoinesian and similar to the revised age for the 7 11 mine walchia reported from eastern ohio late pennsylvanian upland or dryland conifer communities were comprised of walchia cordaites and sigillaria which produced a forest with seed ferns as an understory the cedar run assemblage was probably transported into the valley from adjacent well drained coastal plain uplands formed during valley incision and deposited within the early transgressive systems tract it is also possible that walchia expanded into the valleys when drainage became ephemeral during more arid climatic phases the revised correlations of appalachian basin walchia horizons indicate their appearance closely followed rather than predated the abrupt climate change and extinctions at the desmoinesian missourian boundary

co2 forced climate and vegetation instability during late paleozoic deglaciation the late paleozoic deglaciation is the vegetated earth9s only recorded icehouse to greenhouse transition yet the climate dynamics remain enigmatic by using the stable isotopic compositions of soil formed minerals fossil plant matter and shallow water brachiopods we estimated atmospheric partial pressure of carbon dioxide pco2 and tropical marine surface temperatures during this climate transition comparison to southern gondwanan glacial records documents covariance between inferred shifts in pco2 temperature and ice volume consistent with greenhouse gas forcing of climate major restructuring of paleotropical flora in western euramerica occurred in step with climate and pco2 shifts illustrating the biotic impact associated with past co2 forced turnover to a permanent ice free world

high precision u pb zircon age calibration of the global carboniferous time scale and milankovitch band cyclicity in the donets basin eastern ukraine 1 high precision id tims u pb zircon ages for 12 interstratified tuffs and tonsteins are used to radiometrically calibrate the detailed lithostratigraphic cyclostratigraphic and biostratigraphic framework of the carboniferous donets basin of eastern europe chemical abrasion of zircons use of the internationally calibrated earthtime mixed u pb isotope dilution tracer and improved mass spectrometry guided by detailed error analysis have resulted in an age resolution of 0 05 or 100 ka for these carboniferous volcanics this precision allows the resolution of time in the milankovitch band and confirms the long standing hypothesis that individual high frequency pennsylvanian cyclothems and bundles of cyclothems into fourth order sequences are the eustatic response to orbital eccentricity 100 and 400 ka forcing tuning of the fourth order sequences in the donets basin to the long period eccentricity cycle results in a continuous age model for the middle to late pennsylvanian moscovian kasimovian ghzelian strata of the basin and their record of biological and climatic changes through the latter portion of the late paleozoic ice age detailed fusulinid and conodont zonations allow the export of this age model to sections throughout euramerica additional ages for mississippian strata provide among the first robust radiometric calibration points within this subperiod and result in variable lowering of the base ages of its constituent stages compared to recent global time scale compilations

loading rate impact on fracturing pattern lessons from hydrocarbon recovery lacq gas field france using scaling parameters of induced seismicity in size and space domains seismic b value and spatial correlation dimension d respectively we analyze the fracturing pattern of the gas reservoir of lacq in correlation with the production rate on the basis of previous observations and a previous model segall et al 1994 we assume that the cause of induced seismicity is a poroelastic stressing such that the production rate can be viewed as a stress rate for the rocks adjacent to the reservoir during the 20 year study period the production rate has decreased dramatically leading to a change of poroelastic stress rate from 4 5 10 3 to 1 5 10 3 mpa yr accordingly we observe a significant decrease in the size of activated fractures and a reduction of the spatial clustering of fracturing both arguing for a stress rate impact on the fracturing pattern in the gas field we interpret these changes in terms of a change in the deformation mode of stressed rocks from a more brittle to a more ductile behavior as the stress rate was decreased this hypothesis is supported by independent evidence from a number of experimental numerical and field studies the loading rate thus appears as a possible candidate to drive changes of b and d in time and space the apparent sensitivity of the earth s crust fracturing pattern to loading rate variations of much lower frequency than the tidal variations suggests that the earth s crust deformation mode itself be frequency dependent also our observations may have strong implications in contexts where the loading rate is induced by human intervention e g hydrocarbon recovery mines suggesting the possibility of adjusting the loading rate so as to shape the fracturing pattern locally according to human needs

geochronological constraints on post extinction recovery of the ammonoids and carbon cycle perturbations during the early jurassic abstract this paper presents the first quantitative study of the early jurassic recovery of ammonoids after the end triassic mass extinction based on detailed u pb id tims isotope dilution thermal ionization mass spectrometry geochronology from ash bed zircons placed within a clear phylogenetical and biochronological framework at the subzonal and species level this study was triggered by the discovery of a rich peruvian succession of ammonites deposited concomitantly with an unusually large number of ash beds two major phases of rediversification are observed during the psiloceras spelae and angulaticeras zones that correspond to positive peaks in the 13corg curve providing a possible link between biodiversity and the global carbon cycle in the case of the post extinction recovery the development of the earliest hettangian ammonites occurs within the genus psiloceras which begins with the occurrence of p spelae and then explodes into worldwide development of smooth psiloceratids of the psiloceras planorbis group s l this rapid biodiversification likely occurred less than 100 ka after the end triassic crisis the genus psiloceras occupied all the possible ecological niches worldwide from the pacific deep waters to the nw european shallow deposits and also in some rare tethyan occurrences like at germig in tibet this global dispersion allowed the differentiation of the group in several major phyla the schlotheimiidae discamphiceratinae arietitidae and lytocerataceae which were the roots of all other jurassic and cretaceous ammonites

age and timing of the permian mass extinctions u pb dating of closed system zircons the age and timing of the permian triassic mass extinction have been difficult to determine because zircon populations from the type sections are typically affected by pervasive lead loss and contamination by indistinguishable older xenocrysts zircons from nine ash beds within the shangsi and meishan sections china pretreated by annealing followed by partial attack with hydrofluoric acid result in suites of consistent and concordant uranium lead u pb ages eliminating the effects of lead loss the u pb age of the main pulse of the extinction is 252 6 0 2 million years synchronous with the siberian flood volcanism and it occurred within the quoted uncertainty

glacial eustatic sea level curve for early late pennsylvanian sequence in north central texas and biostratigraphic correlation with curve for midcontinent north america at least 30 transgressive regressive cycles of deposition are recognized from the upper desmoinesian east mountain shale to the mid virgilian wayland shale in north central texas maximum regressive deposits are typically paleosol mudstones and fluvial sand stones maximum transgressive deposits are typically widespread ammonoid bearing conodont rich dark phosphatic shales in more major cycles and persistent fossiliferous shales or limestones overlying terrestrial deposits in more minor cycles delta complexes dominate the regressive sequences of many cycles using biostratigraphic criteria of first last sole or acme occurrence of ammonoid conodont and fusulinid taxa we correlate 17 cycles in the texas sequence directly with 17 glacial eustatic cycles of similar magnitude in the northern midcontinent this correlation suggests that glacial eustacy was the basic control over the cyclic sequence in texas that tectonic masking of the eustatic signal by nearby orogenic movement in texas was negligible and that delta shifting though conspicuous was only a secondary control over the cyclicity there minor cycles recognized between the correlated cycles also match well enough between texas and the midcontinent to further discount potential tectonic or deltaic masking of glacial eustatic cyclicity this strengthens the likelihood of correlating glacial eustatic events across larger parts of north america and perhaps with other parts of the world

orbital control on cyclical primary productivity and benthic anoxia astronomical tuning of the telychian stage early silurian abstract the identification of milankovitch cycles and the establishment of a high resolution astronomical time scale for the palaeozoic represent a research frontier in cyclostratigraphy and astrochronology a continuous core drilled through the telychian stage llandovery silurian of the paslek formation in the baltic basin poland is characterized by repetitive centimetre scale alternations of homogeneous greenish grey mudstones and faintly laminated dark grey to black mudstones such lithological rhythmicity reflects a cyclical variation in redox conditions at the sediment water interface and therefore was used to construct a floating astronomical time scale ats for the telychian stage the cyclostratigraphic analysis was performed on a 5 mm resolution greyscale scan based upon photographs of the slabbed core with lower values associated with greenish grey mudstones and higher values related to dark grey to black mudstone facies spectral density estimation by means of the multitaper method mtm reveals significant peaks rising above the 95 red noise confidence level that we interpret as the 405 kyr long eccentricity short eccentricity obliquity and precession components the mtm evolutive power spectral analysis epsa shows a gradual increase in the velocity of sedimentation from 5 03 m myr in the lowermost interval to 5 48 m myr towards the uppermost part of the studied sequence we postulate that the observed cycles reflect orbitally driven climatic variations from stable wet conditions to monsoon like high seasonal contrasts that affected weathering intensity runoff and nutrient supply these cyclical variations led to rhythmic variations in organic matter fluxes and benthic anoxic conditions in the analysed record orbital precession influenced the deposition of the greenish grey mudstone and dark grey to black mudstone couplets occurring on average every 10 cm furthermore long eccentricity modulation of precession controlled the relative depositional predominance of one facies over the other observed periodicities resemble those of cenozoic and mesozoic orbitally controlled records thus suggesting that during the silurian the orbital eccentricity forcing on the carbon flux acted in the same way as in the cenozoic and mesozoic the orbital tuning of the studied interval calibrated by means of accurate acritarch biostratigraphy allowed for the estimation of an astronomically calibrated duration for the telychian stage of about 5 46 myr

new high precision u pb dates from western european carboniferous tuffs implications for time scale calibration the periodicity of late carboniferous cycles and stratigraphical correlation we present three new high precision u pb zircon chemical abrasion isotope dilution thermal ionization mass spectrometry ca id tims dates from western european carboniferous diagenetically altered volcanic ash layers bentonites and tonsteins that occur interbedded with cyclic siliciclastic sedimentary rocks the dates constrain the average periodicity of western european late carboniferous arnsbergian to early langsettian cyclic sedimentation to between 89 and 124 ka per cycle this is consistent with the 100 ka short eccentricity milankovitch cycle and supports previous suggestions that the cycles are the product of glacio eustasy cyclostratigraphic tuning of namurian cycles to the 100 ka eccentricity cycle revises the timing of the global mississippian pennsylvanian boundary to c 323 9 ma ca id tims dates also facilitate correlation between different facies belts where biostratigraphical correlations are difficult correlation between eastern and western european sequences confirms that the base of the moscovian stage is located within the duckmantian westphalian b western european regional substage supplementary materials zircon separation and concentration procedures u pb zircon ca id tims methods and data table average periodicity calculations for western and central european namurian and westphalian sedimentary cycles and procedures for recalibrating legacy 40 ar 39 ar dates are available at www geolsoc org uk sup18547

reply to the comment on sequence stratigraphy and onlap history of the donets basin ukraine insight into carboniferous icehouse dynamics abstract ruban this issue raises two concerns regarding the onlap offlap curve recently published by eros et al 2012 for the donets basin one issue questions the use of the carboniferous timescale presented in eros et al 2012 given that it differs from that of the geologic time scale 2004 davydov et al 2005 the second issue addresses three discrepancies between the donets curve and the available global eustatic curve of haq and schutter 2008 bringing into question the degree to which the donets onlap offlap history might record regional tectonism to continental scale mantle dynamics over glacioeustasy the carboniferous timescale davydov et al 2010 used by eros et al 2012 incorporates new high precision id tims u pb dates from tonsteins collected throughout the donets basin that are tied to stratigraphic sections and sequences referenced in eros et al 2012 this time scale forms the basis of the carboniferous interval in the latest edition of the geologic timescale 2012 davydov et al 2012 which we consider the most appropriate for use in carboniferous studies here we present a high resolution correlation between the onlap and sea level histories for the u s midcontinent ross and ross 1987 heckel 2008 the donets basin and the pennine basin waters and condon 2012 made possible by recently published chronostratigraphic constraints davydov et al 2010 schmitz and davydov 2012 this robust chronostratigraphically constrained comparison argues for a dominant eustatic driver on the observed hierarchy of stratigraphic cyclicity and inferred sea level variations on the 105 and 106 year scale in minimally the cross pangaean paleotropical regions existing discrepancies between these correlated records and the late paleozoic record of modal mean of change in sea level haq and schutter 2008 awaits future inter regional correlations of radiometrically and biostratigraphically well constrained carboniferous successions

sedimentology and stratigraphy of the amasra coalfield pennsylvanian nw turkey new insight from a 1 km thick section abstract we report on a sedimentological and biostratigraphic evaluation that was carried out on an approximately 1 km thick coal bearing pennsylvanian succession encountered in the boreholes hema 82 and 85 in the amasra coalfield of the zonguldak amasra coal basin turkey results of the study include a refined interpretation of sedimentary environments of the coal bearing strata and their cyclic patterns improved constraints on macrofloral biozones as well as of boundaries and thickness of lithostratigraphic units a paleosol based climatic trend is also proposed and the tectono sedimentary history of the amasra coalfield is compared with other coal basins in europe stratigraphically constrained macroflora confirms a recently suggested discontinuous sedimentary record that contrasts with the previously widely accepted opinion that deposition was continuous throughout the pennsylvanian hiatuses were identified between each adjacent formation an early asturian hiatus between the karadon and kizilli formations has its equivalent in other variscan basins of europe namely in the dobrudzha upper silesian intra sudetic and central and western bohemian basins it is in agreement with the former paleogeographic position of the zonguldak amasra basin and its basement in the southern margin of laurussia in the eastern continuation of these central european basins this conclusion is further supported by paleosol morphology based climatic trend to increasing aridity around the westphalian stephanian boundary observed in the studied boreholes and identical with a similar trend in the above mentioned central european basins

a chronology of paleozoic sea level changes sea levels have been determined for most of the paleozoic era 542 to 251 million years ago but an integrated history of sea levels has remained unrealized we reconstructed a history of sea level fluctuations for the entire paleozoic by using stratigraphic sections from pericratonic and cratonic basins evaluation of the timing and amplitude of individual sea level events reveals that the magnitude of change is the most problematic to estimate accurately the long term sea level shows a gradual rise through the cambrian reaching a zenith in the late ordovician then a short lived but prominent withdrawal in response to hirnantian glaciation subsequent but decreasingly substantial eustatic highs occurred in the mid silurian near the middle late devonian boundary and in the latest carboniferous eustatic lows are recorded in the early devonian near the mississippian pennsylvanian boundary and in the late permian one hundred and seventy two eustatic events are documented for the paleozoic varying in magnitude from a few tens of meters to 125 meters

periodicity of mesoscale phanerozoic sedimentary cycles and the role of milankovitch orbital modulation data on more than 200 mesoscale sedimentary cycles indicate that phanerozoic cycle periods are randomly distributed with respect to the four major milankovitch orbital parameters except late mississippian through late pennsylvanian cycles which show positive clustering about the 413 000 yr eccentricity period cycle periods calculated from average thicknesses and accumulation rates are strongly dependent on the former correlation coefficient 0 802 but relatively independent of the latter correlation coefficient 0 360 hence calculated period is largely a function of average cycle thickness and milankovitch range periods will be preferentially calculated for cycles with average thicknesses between 1 m and 20 m regardless of actual causes of cyclicity for individual cyclic sequences arguments for milankovitch control based solely on average period are unfounded comparison of short term holocene sedimentation rates and long term phanerozoic accumulation rates for cyclic peritidal and delta

sequence stratigraphy and correlation of late carboniferous and permian in the cis europe tethyan area north africa arabia china gondwanaland and the usa abstract sequence stratigraphy was used to correlate the depositional chronology during permo carboniferous time in various sedimentary basins of gondwanaland western europe eastern europe tethyan area north africa arabia china and north america during late carboniferous and permian eleven second order sequences sos were recognised throughout the whole area the sequence si is serpukhovian pp namurian a pp and chesterian the sequence sii is serpukhovian pp bashkirian pp namurian a pp b c westphalian a b pp and morrowan the sequence siii is late bashkirian moscovian westphalian b pp c d and atokan desmoinesian the sequence siv is kasimovian early stephanian and missourian the sequence sv is gzhelian orenburgian late stephanian and virgilian the sequence svi is asselian autunian and nealian the sequences svii ix are saxonian sakmarian artinskian kungurian and leonardian hessian cathedralian the sequences sx xi are guadalupian and lopingian depending on the regional setting different relationships exist between marine transgression and the respective effects of tectonics and of sea level changes in western europe effects of the glacial processes in gondwanaland are partly balanced by the late compression in the hercynian belt during moscovian eastern europe tethyan area north africa china and north america show a good correlation between glacial ice melting processes in gondwanaland and the intensity of the transgression which is increased by the westward progradation of the orogeny in urals and appalachians in arabia tunisia and tethyan area the impact of the neotethys opening is obvious from the artinskian and mainly during the late permian

triaxial compression experiments on intact veined andesite abstract a comprehensive experimental program was instigated to test intact veined andesite from the el teniente mine chile under triaxial compression with confining pressure ranging from 2 to 60 mpa the experimental program established that the veins acted as weak mechanical components in the specimens promoting rock fracture under stress the experimental results indicated that the stress thresholds identifying the onset of dilatancy and the transition from the stable to unstable fracturing were higher in intact veined rock than in intact rock the observed behaviour illustrated a significant departure from intact rock where the onset of acoustic emissions ae correlates with the onset of specimen dilatancy the experimental results from intact veined rock indicated that the onset of ae correlated with the crack damage stress the departure from the behaviour of intact rock is attributed to the presence of veins

amisr 14 observations of equatorial spread f a new 14 panel advanced modular incoherent scatter radar amisr 14 system was recently deployed at the jicamarca radio observatory we present results of the first coherent backscatter radar observations of equatorial spread f esf irregularities made with the system colocation with the 50 mhz jicamarca unattended long term studies of the ionosphere and atmosphere julia radar allowed unique simultaneous observations of meter and submeter irregularities observations from both systems produced similar range time intensity maps during bottom type and bottomside esf events we were also able to use the electronic beam steering capability of amisr 14 to image scattering structures in the magnetic equatorial plane and track their appearance evolution and decay with a much larger field of view than previously possible at jicamarca the results suggest zonal variations in the instability conditions leading to irregularities and demonstrate the dynamic behavior of f region scattering structures as they evolve and drift across the radar beams

correlation of microseismic and chemical properties of brittle deformation in locharbriggs sandstone constant stress rate loading the exit pore fluid was analyzed after the tests for the concentration of dissolved ions and acoustic emission was monitored in real time throughout the tests the exit pore fluid silica concentration and microcrack damage derived from the acoustic emission ae data both exhibited an exponential increase during the strain hardening phase of deformation damage parameters inferred from the ae data predict the stress strain curves adequately or at least up to the point of strong microcrack coalescence the damage parameters and silica signal were strongly correlated by a power law relationship the observed environment and strain rate dependence of mechanical properties can hence be attributed uniquely to time dependent crack growth by the stress corrosion mechanism index terms 1045 geochemistry low temperature geochemistry 5102 physical properties of rocks acoustic properties 5104 physical properties of rocks fracture and flow keywords stress corrosion acoustic emission silica dissolution subcritical crack growth deformation rate brittle fracture citation ojala i o b t ngwenya i g main and s c elphick correlation of microseismic and chemical properties of brittle deformation in locharbriggs sandstone j geophys res 108 b5 2268 doi 10 1029 2002jb002277 2003

generic types of stratigraphic cycles controlled by eustasy thought experiments imply that stratigraphic cycles controlled directly by eustasy include keep up catch up catch down foreshortened or truncated and give up variants different patterns of thick ness and facies being governed by the interplay of sedimentation rate and accommodation space most examples of these types are in addition base cutout cycles wherever lowstands of sea level dropped below the top of the underlying cycle overall thicknesses of multiple cycles at any locale are controlled ultimately by net subsidence rate accordingly even keep up and catch up cycles can faithfully record full accommodation only where tectonic subsidence during cycle formation paced eustatic fluctuation paradoxically however only condensed cycles that fortuitously compensate for syncycle tectonic subsidence can accurately record the eustatic amplitude as adjusted for water loading

a model based evaluation of tropical climate in pangaea during the late palaeozoic icehouse abstract the late palaeozoic ice age lpia is the earth s penultimate icehouse climate geological proxies for tropical pangaean climate during the lpia are significantly modulated on 100 400 kyr and sub 100 kyr scales in addition some geological proxies suggest that equatorial continental areas may have been colder and more arid during lpia glacial intervals than during late cenozoic glacial intervals furthermore the relationship between polar and tropical climate variability remains controversial the climate dynamics underlying these phenomena are only partly understood nevertheless past modeling of lpia climate has suggested that precipitation near the equator was modulated by monsoonal circulation that itself was modulated by orbital variability here the earth s climate during asselian sakmarian time 299 284 ma was simulated with the community climate system model version 3 ccsm3 these simulations address model climate sensitivity to direct and indirect effects of glaciation as well as variability in the earth s orbit the results of these simulations suggest that sea level and orbitally forced monsoon variability were the primary controls on tropical precipitation when ice sheets were confined to polar latitudes any impact of orbital forcing on glaciation therefore could have led to aliasing between glacial and monsoonal effects in particular regions perhaps explaining contrasting geologically based interpretations of how tropical climate responded to glaciation glaciation of the central pangaean mountains would have led to widespread cold and aridity in equatorial pangaea but forming these glaciers would have required an unknown additional climate forcing with an unknown impact on tropical precipitation

global time scale and regional stratigraphic reference scales of central and west europe east europe tethys south china and north america as used in the devonian carboniferous permian correlation chart 2003 dcp 2003 the boundaries of the devonian carboniferous and permian stages of the global stratigraphic reference scale abbreviated to global stratigraphic scale gss are described in relation to the biostratigraphic and or lithostratigraphic units of the regional stratigraphic reference scales abbreviated to regional stratigraphic scales rss of central and west europe east europe tethys south china eastern tethys and north america in their type regions the boundaries of gss units rarely coincide with those of homonymous rss units moreover the definitions of some rss units have changed several times over the last decades and subsequent misunderstanding of the stratigraphical significance of these changes has often introduced errors into proposed global correlation charts the stratigraphic framework proposed in our global devonian carboniferous permian correlation chart 2003 dcp 2003 devonian carboniferous permian correlation chart 2003 menning m schneider j w alekseev a s amon e o becker g von bitter p h boardman d r bogoslovskaya m braun a brocke r chernykh v chuvashov b i clayton g dusar m davydov v i dybova jachowicz s forke h c gibling m gilmour e h goretzki j grunt t a hance l heckel p h izokh n g jansen u jin y g jones p kading k ch kerp h kiersnowski h klets a klug ch korn d kossovaya o kotlyar g v kozur h w laveine j p martens th nemyrovska t l nigmadganov a l paech h j peryt t m rohn r roscher m rubidge b schiappa t a schindler e skompski s ueno k utting j vdovenko m v villa e voigt s wahlman g p wardlaw b r warrington g weddige k werneburg r weyer d wilde v winkler prins c f work d m 2004 abschlusskolloquium dfg schwerpunktprogramm 1054 evolution des systems erde wahrend des jungeren palaozoikums im spiegel der sedimentgeochemie abstracts univ erlangen germany 2004 p 43 herein abbreviated to dcp 2003 and cited as dcp 2003 in references is an attempt to reduce these errors the dcp 2003 is the stratigraphic base for project 1054 of the deutsche forschungsgemeinschaft dfg the evolution of the late palaeozoic in the light of sedimentary geochemistry this composite time scale has been carefully balanced as far as data allows to remove unnecessary artificial compression and expansion of time intervals biozonations and depositional events the ages selected in dcp 2003 are markedly different to those in the geologic time scale 1989 gts 1989 harland w b armstrong r l cox a v craig l e smith a g smith d g 1990 a geologic time scale 1989 cambridge univ press cambridge harland w b armstrong r l cox a v craig l e smith a g smith d g 1990 a geologic time scale 1989 cambridge univ press cambridge pp 1 263 and in gradstein and ogg gradstein f m ogg j 1996 a phanerozoic time scale episodes 19 1 2 3 4 insert whereas they are closer to those of the geologic time scale 2004 gts 2004 gradstein f m ogg j g smith a g 2004 a geologic time scale 2004 cambridge univ press cambridge pp 1 589 mostly the ages are rounded to the nearest 0 5 ma in order to avoid estimates of questionable accuracy whereas ages of 0 1 ma in the gts 2004 and their error bars of 0 4 ma to 2 8 ma for the devonian to permian stage boundaries suggest an improved accuracy in contrast in the dcp 2003 questionable ages and positions of stratigraphic boundaries are marked by arrows c 2006 elsevier b v all rights reserved

first observations of the spatial structure of f region 3 m scale field aligned irregularities with the equatorial atmosphere radar in indonesia 1 this paper presents first results of spatial structure associated with 47 mhz coherent backscatter from the low latitude f region in the indonesian thai longitude sector the measurements were made with the equatorial atmosphere radar ear located on the geographic equator in west sumatra indonesia 0 20 s 100 32 e dip latitude 10 36 s the active phased array of the ear was used to perform rapid scans over a wide azimuth sector with a temporal resolution that has heretofore been unachievable application of this unique capability is demonstrated herein to be effective in investigations of spatial structure of plasma bubbles and associated backscatter plumes most notably tiny plumes are shown to grow rapidly while traversing from west to east across the scanned azimuth sector within an initial 20 min period backscatter intensity increased by more than 40 db and the area of the plume increased by a factor of about 20 occasionally plumes reached altitudes as high as 800 to 860 km in the scanned sector these backscatter regions were traced along the magnetic field line to altitudes of 1200 to 1300 km over the geomagnetic equator however these tall structures are not so common over the ear the ear observes fairly conspicuous patchy backscatter from the bottomside of a backscatter plume the backscatter generated at the bottom of the plume appears to descend and eventually merge into the e region backscatter the ear has also observed a downward moving plume that continues for more than 4 hours beginning at an altitude well into the topside of the ionosphere and descending below 300 km the backscatter sometimes observed with the ear at dip latitude of 10 36 s resembles that observed with the mu radar at mid latitudes investigation of these properties with the fast beam steerability of the ear is expected to provide further insight into the nature of the source mechanism for plasma bubbles and plumes

a method for intercalibration of u th pb and 40ar 39ar ages in the phanerozoic the increasing analytical precision of 40ar 39ar geochronological data and its use in studies that combine u pb and 40ar 39ar data has necessitated derivation of a means to intercalibrate ages between the two isotopic systems the primary determinants inhibiting accurate cross calibration are uncertainty in decay constant values and uncertainty in 40ar 40k usually presented as apparent age for 40ar 39ar standards notably those derived from the fish canyon tuff by utilizing a monazite and biotite bearing oligocene ash flow tuff mac 83 as the primary standard material precise u th pb and 40ar 39ar ages can be derived because both isotopic systems should reflect closure during the instantaneous eruption event the 24 21 0 10 ma 207pb 235u age should match the age resulting from 40ar 39ar biotite analysis this forced equivalence will partly offset the effects of decay constant uncertainty furthermore by co irradiating fish canyon tuff sanidine with mac 83 biotite the apparent age for fish canyon tuff sanidine is back calculated to 27 98 0 15 ma relative to the mac 83 207pb 235u age hence intercalibration between the two isotopic systems in a relative sense can be accomplished allowing for a direct and valid comparison of ages it is also shown that forcing equivalence of the two isotopic systems minimizes the effect of decay constant uncertainty for samples of phanerozoic age

a constitutive law for low temperature creep of water saturated sandstones an accurate predictive model for the long term strength of the continental lithosphere is important in a range of geophysical and geodynamic problems while laboratory experiments are consistent with mohr coulomb brittle faulting in the cold upper continental crust there is increasing evidence that time dependent processes may also be important in these rocks even at low temperature however there is some ambiguity as to the exact form of the constitutive law for describing time dependent behavior of upper crustal rocks here we present results of room temperature creep experiments on a suite of water saturated sandstones spanning a range of petrophysical and rheological properties and underlying deformation mechanisms on physical and microstructural grounds our analysis suggests that a modified power law creep of the form a d f where d is the differential stress and f is the long term failure fundamental strength provides a more complete description of the experimental data in particular the parameters can be used to differentiate between sandstone types with a f and varying systematically with cementation state rock rheology and confining pressure the fundamental strength f for time dependent deformation varies much more than the other parameters of the distribution making it a potentially sensitive indicator of underlying creep mechanisms further tests would be needed to prove the constitutive law on a wider range of rock types and to prove that the three parameter model is statistically better in the general case

zircon petrochronology and 40ar 39ar sanidine dates for the mesa falls tuff crystal scale records of magmatic evolution and the short lifespan of a large yellowstone magma chamber

geologic framework for the coal bearing rocks of the central appalachian basin abstract coal production has been an important economic factor in the central appalachian basin however regional stratigraphic and structural relationships of the coal bearing rocks of the basin have been poorly understood due to numerous separate nomenclatural schemes employed by various states in order to estimate coal resources and understand mechanisms controlling the distribution of coal within the basin a reliable geologic framework is necessary seven detailed cross sections across the central appalachian basin were constructed in order to examine the stratigraphic and structural framework of the coal bearing rocks in the basin the cross sections were based on more than 1000 oil and gas well logs measured sections and borehole information from kentucky ohio tennessee virginia and west virginia the cross sections revealed three main points discussed here southeast thickening of the pennsylvanian strata uncomfortable northwestward onlapping relationship of lower pennsylvanian strata over underlying lower pennsylvanian and mississippian strata and regional continuity of beds the cross sections geologic mapping coal resource studies extensive new highway exposures and the occurrence of tonstein beds indicate that many coal beds and marine strata are laterally extensive albeit locally variable across the basin certain quartzose sandstone bodies are also extensive over large areas of the basin existing stratigraphic nomenclature schemes obscured the geologic framework of the basin so a new unified nomenclature scheme was devised to better describe stratigraphic features of the basin the new stratigraphic nomenclature now only formalized for kentucky was based on key stratigraphic units that proved to be extensive across the basin lower and middle pennsylvanian rocks are now recognized as the breathitt group the breathitt formation was elevated to group rank the breathitt group was subdivided into eight coal bearing formations by relatively thick marine strata and in the lower part of the breathitt group by quartzose sandstone formations the new coal bearing units are formally ranked as formations and in ascending order are the pocahontas bottom creek alvy creek grundy pikeville hyden four corners and princess formations the quartzose sandstone units are also formally ranked as formations and are in ascending order the warren point sewanee bee rock and corbin sandstones the sandstone formations were previously recognized units in some states but have been extended formally in kentucky across the basin the key stratigraphic marine units are formally ranked as members and are in ascending order the betsie shale member the kendrick shale member magoffin member and stoney fork member

high precision 40ar 39ar spectrum dating on sanidine from the donets basin ukraine evidence for correlation problems in the upper carboniferous two 40 ar 39 ar spectrum measurements on well preserved volcanic feldspar sanidine from the coal tonstein horizon 1 3 1 from the lower kashirsky group middle moscovian stage of the donets basin upper carboniferous ukraine yielded well defined plateaus with an average age of 305 5 1 5 ma the age is to be interpreted as sedimentation age of the coal tonstein and thus defines a chronostratigraphic time mark in the east european carboniferous taking the correlation of the 1 3 1 horizon and the recently published time scales for the upper carboniferous as a basis for comparison the age of 305 5 ma is about 6 ma too young this age discrepancy obviously points to inaccurate or even erroneous correlation and we therefore are compelled to suggest a reconsideration of the validity of the current biostratigraphic correlation between the carboniferous of western and east europe

amplitudes of late pennsylvanian glacioeustasy the late paleozoic is well documented as a time of significant continental glaciation but the extents of the glaciation and attendant glacioeustasy are not well constrained because precise amplitudes of eustasy are difficult to extract from the stratigraphic record in this paper we use preserved relief on ancient subaerial exposure surfaces of large algal bioherms to demonstrate directly that late pennsylvanian glacioeustasy reached minimum amplitudes of 80 m and probably exceeded 100 m upper paleozoic algal bioherms accreted predominantly during sea level falls but also during sea level rises and highstands and were capable of remarkably rapid growth rates eustatic amplitudes in excess of 100 m approach amounts documented for the pleistocene and place constraints on models for gondwanan ice volume climate dynamics and potential character and magnitude of glacioclimatic fluctuations

callipterid peltasperms of the dunkard group central appalachian basin abstract the dunkard group is the youngest late paleozoic rock unit in the central appalachian basin its age however remains controversial in its southern and western two thirds the dunkard is comprised largely of red beds sandstone and siltstone channel deposits and paleosols in its thickest most northerly exposures in southwestern pennsylvania northern west virginia and east central ohio much of the lower part of the unit is composed of coals non marine limestones and gray often calcareous paleosols age dating is confounded by the non marine nature of the deposit and by the lack of dateable volcanic ash beds dunkard fossils include plants vertebrates and both aquatic and terrestrial invertebrates most of the fossil groups point to an age very close to if not including the pennsylvanian permian boundary though the exact position of that boundary is uncertain callipterids make their first appearance in the dunkard flora in the middle of the washington formation and continue into the greene formation but in different beds from those containing wetland floral elements publication of these plants in the permian flora of fontaine and white 1880 created an immediate controversy about the age of the unit because callipteris conferta now autunia conferta was at the time considered to be an index fossil for the base of the permian subsequent collecting has revealed these callipterds to comprise four species a conferta autunia naumannii lodevia oxydata and rhachiphyllum schenkii callipterids and the conifers with which they are sometimes associated are typically found in seasonally dry equatorial environments and most likely constitute an environmentally controlled biofacies this biofacies is not well known resulting in limited biostratigraphic utility

climatology of f region zonal plasma drifts over jicamarca 1 we use extensive incoherent scatter radar observations made at the jicamarca radio observatory between 1970 and 2003 to study and model empirically the equatorial zonal plasma drifts near the f region peak using bernstein polynomials as base functions our quiet time model results confirm that the daytime drifts are westward and are nearly season and solar cycle independent the nighttime drifts are eastward have larger magnitudes and increase strongly with solar flux particularly near equinox and december solstice enhanced geomagnetic activity drives small eastward perturbation drifts during the day and much larger westward disturbance drifts at night the nighttime drift perturbations are largest near midnight and increase strongly with solar flux near equinox and december solstice but are essentially absent near june solstice the jicamarca zonal disturbance drifts can be largely accounted for by disturbance dynamo electric fields with a dominant time delay of about 3 15 hours following enhanced geomagnetic activity in the postmidnight sector there are also smaller westward disturbance drifts associated with time delays of about 15 24 hours and perhaps even longer our results strongly suggest that the longitudinal dependence of both the quiet and disturbed equatorial nighttime zonal drifts varies with season

radioisotopic calibration of the guadalupian middle permian series review and updates abstract four high precision u pb ca idtims dates for the roadian lower guadalupian of 274 0 0 12 and 273 1 0 1 ma and for the wuchiapingian lower lopingian of 260 16 0 39 and 258 14 0 20 ma were obtained from permian tuff beds in the periphery of the okhotsk massif n e russia the beds are well constrained within the local lithostratigraphic and regional biostratigraphic framework besides regional bivalves and brachiopod faunas the ammonoid sverdrupites harkeri occurs close to the recovered roadian tuffs this ammonoid provides direct correlation of the tuffs with the kazanian stage on the russian platform and the roadian stage in the canadian arctic where the conodont index species of the roadian stage jinogondolella nankingensis gracilis and sverdrupites harkeri and other roadian ammonoids are documented from the assistant formation our review of the kungurian roadian wordian successions in the main well studied regions suggests that the base of the roadian stage should be extended down to approximately 277 ma and the roadian wordian boundary should be placed at approximately 271 ma the new calibration of the roadian stage reduces the duration of the enormously long kungurian stage from about 10 myr approximately to 6 0 6 5 myr if the proposed calibration is correct the duration of guadalupian series would be almost twice as great as in the previous estimates our results also suggest a possible correlation of the p3 alpine glacial event in the eastern australia with the wordian and possible uppermost roadian stages this p3 event corresponds with the disappearance of ammonoids and conodonts in the upper roadian and wordian in high latitudes regions i e n e russia russian and canadian arctic and australia perhaps due to extreme cooling of these areas the new radioisotopic ages in the okhotsk massif and surrounding regions improve the numerical calibration of the palynological zonation in the eastern australia and provide a direct correlation of the regional biostratigraphic brachiopod and bivalve zonation of n e russia with the international geologic time scale this zonation becomes a solid and reliable regional correlation tool within the vast territory from taymyr and east siberia to entire n e russia and transbaikalia

age and depositional environment of the xiaheyan insect fauna embedded in marine black shales early pennsylvanian china abstract the early pennsylvanian xiaheyan entomofauna ningxia china is among the earliest assemblages of winged insects known so far and therefore provides an essential input on deciphering the early diversification of this group despite its evolutionary significance both the age and depositional environment remained poorly constrained here we present high resolution documentation of litho and biofacies biostratigraphy and geochronology of the up to 100 m thick type section accordingly the insect bearing strata are of latest bashkirian latest duckmantian to middle moscovian bolsovian age the sediments lithostratigraphically assigned to the yanghugou fm represent a regressional marine sequence formed at the southern margin of the qilian inland sea intercalations of crevasse channels and splays that laterally interlock with marine black shales and bioclastic limestones point to deposition in an interdelta bay ground touching waves provoked the erosion of muds at shallow depths leading to mass mortalities among mollusc communities due to rising anoxia turbidity and water turbulence in addition bottom currents transported mud intraclasts towards the basin where sinking insects that reached the bay via winds and surface currents were buried sub contemporaneously with bivalves below the storm wave base observed differences in insect preservation and assemblage composition across the sequence are found to correlate with lithology and are best explained by distance from land and the action of events inducing insect carcasses to sink such as storms the proposed taphonomic model represents a new fossilization pathway from land to sea and provides new directions for prospecting paleozoic deposits in the search for insects

temporal variations in seismicity during quasi static and dynamic rock failure abstract a comprehensive model is presented which can explain temporal fluctuations in seismic b values in the period leading to mechanical failure in terms of the underlying physical processes of time varying applied stress and stress corrosion enhanced crack growth under conditions of constant strain rate the form of the b value anomaly in the period leading to failure depends on the form of the stress time relationship for the case where dynamic failure occurs at peak stress after a period of strain hardening the model predicts a single cusp like b value anomaly reaching a critically low value of 0 5 at failure for the physically most realistic case where dynamic failure is preceded by a period of precursory strain energy release during strain softening the model predicts two minima in the b value separated by a temporary maximum or inflection point these fluctuations in the b value are consistent with reported intermediate term and short term earthquake precursors separated by a period of seismic quiescence for the case of quasi static cataclastic flow the b value mirrors the stress and never falls to the critical value because there is no critical rupture new results from a series of controlled laboratory experiments are presented in which microseismic event rates and b value were monitored contemporaneously with stress time data for all variants of the stress time relationship recent field observations of temporal changes in seismicity rates and b value preceding major earthquakes are also reported both data sets exhibit b value anomalies which are consistent with the model predictions

climatically driven cyclicity and peat formation in fluvial setting of the moscovian early kasimovian cracow sandstone series upper silesia poland abstract the approximately 1200 m thick cracow sandstone series middle early late pennsylvanian in the polish part of the upper silesian coal basin consists of 25 70 m thick fining up and laterally widespread fluvial cycles the cycles are marked by alternating sheet like sandstone bodies overlain by much thinner intervals dominated by mudstone and coal these two member cycles record the alternation of a sand dominated fluvial braidplain and floodplain dominated fluvial system with channels confined to narrow belts the lateral persistence internal architecture and isochronous alternations suggest an allogenic origin for the cycles possibly related to climate this interpretation is supported by a three stage evolution of pedogenic processes operating on floodplain deposits beginning with the formation of vertisols followed later by gleying and finally termination by a histosol peat formation such a succession of paleosols indicates a climatic shift from highly seasonal vertisol to humid climate coal with the most seasonal part of the cycle likely represented by the sheet like sandbody the mechanistic link between climate and the cyclic pattern of strata is explained as climatically driven variations in clastic supply which was highest during periods of prominent seasonality short term climatic oscillations generating cyclic patterns in the cracow sandstone series are superimposed on a long term climatic shift towards increased seasonality near the middle late pennsylvanian boundary this is evidenced by the termination of peat formation in the upper silesian basin as well as in some other coeval basins of the equatorial pangea and is interpreted to represent a potentially regional climatic event

evidence of dilatant and non dilatant damage processes in oolitic iron ore p wave velocity and acoustic emission analyses uniaxial and triaxial compression experiments were performed on oolitic iron ores to investigate damage processes most of these experiments included four indirect measurements of damage evolution that is p wave velocity and maximum amplitude received during pulse transmission experiments elastic properties apparent young s modulus and apparent poisson s ratio and acoustic emission ae monitoring the mechanical behaviour deduced from strain measurements is dilatant for some samples and non dilatant for the other samples however variations in elastic properties indicate damage processes for all samples ae source mechanism analysis shows two different microscopic damage processes 1 for dilatant rock the development of axial extensive microcracks as well as their interaction and coalescence lead to the formation of shear macroscopic discontinuities 2 for non dilatant oolitic iron ore both compressive and shear micromechanisms take place and interact with macroscopic fractures a particular consistency between the four types of measurements employed was observed

upper devonian and mississippian foraminiferal and rugose coral zonations of belgium and northern france a tool for eurasian correlations the radiation of early carboniferous foraminifers and rugose corals following the devonian carboniferous crisis offers the best tool for high resolution correlations in the mississippian together with the conodonts in the tournaisian notably in the namur dinant basin however some of the guides are facies controlled and an integrated approach combining biostratigraphy sedimentology and sequence stratigraphy is critical to identify delayed entries potential stratigraphic gaps and to avoid diachronous correlations the main difficulty is in correlating shallow and deeper water facies at any given time in existing zonations the visean part of the scheme is always more detailed reflecting the widespread development of shallow water platforms in the early visean which created conditions more suitable for foraminifers and rugose corals over large areas in contrast the tournaisian zones less well documented reflect unfavourable environmental conditions in the lower ramp dinant sedimentation area and pervasive dolomitization of the inner ramp condroz and namur sedimentation areas recent progress in understanding the belgian early carboniferous sequence stratigraphy and lithostratigraphy and revision of the biostratigraphy of the key sections strongly modify former biostratigraphic interpretations improvements mainly concern the latest devonian the late tournaisian and the early visean the late devonian and the tournaisian are equated with foraminifer zones dfz1 to dfz8 and mfz1 to mfz8 respectively the visean correlates with zones mfz9 to mfz14 zone mfz15 straddles the visean namurian boundary and zone mfz16 is the youngest mississippian zone the rugose corals allow the recognition of ten zones rc0 to rc9 covering the strunian late famennian to serpukhovian interval discrepancies with former zonations are discussed the moliniacian stage is emended to restore the coincidence between its base and that of the visean

late paleozoic tropical climate response to gondwanan deglaciation coupled climate biome model simulations of the late paleozoic were developed to determine the response of pangean tropical climate to gondwanan deglaciation the model simulations predict substantial changes over equatorial pangea including continental drying a reversal of equatorial winds warming heavier 18 o values of meteoric precipitation and the expansion of deserts and the contraction of forests the magnitude of these tropical responses is sensi tive to the extent of gondwana continental ice and the deglacial rise in atmospheric pco 2 boundary conditions that are not well known for the late paleozoic nonetheless the model predictions are consistent with climatic and environmental trends determined from terrestrial proxy data implying that the deglaciation of gondwana was a transformational climate event in tropical pangea

the brazil guara equatorial spread f campaign results of the large scale measurements the guara campaign equatorial spread f rocket was launched from alc ntara brazil on 14 october 1994 at 1955 lt 2255 ut into an active topside spread f event spread f plasma irregularities observed up to 822 km altitude correlate well with plumes observed simultaneously with a coherent backscatter radar matching 1 10 km features in the rocket and radar data over the altitude range 300 800 km implies an eastward drift speed of 110 m s versus 95 m s at 400 500 km based on radar interferometry combining these two measurements implies an average upward drift of 30 m s for the highest altitude structures the amplitude difference between low and high altitude 10 km density structures if attributed to temporal effects implies an effective diffusion coefficient decay time constant of 500 1000 m s 2 4 10 4 s 1 which agrees with previous estimates from other techniques and supports the idea that the decay of spread f turbulence occurs in a scale independent manner

microcracks in rocks a review abstract in the past decade the number of studies about microcracks in rocks has rapidly increased this review of recent work concentrates on microcracks in rock as separate entities emphasizing microcrack morphogenesis kinematics dynamics population statistics and observational techniques cracks are produced when the local stress exceeds the local strength the local stress may be augmented by twin lamellae interactions kink bands and deformation lamellae stress concentrations at grain boundary contacts and around intracrystalline cavities local strength may be reduced along cleavage planes along grain boundaries and along any internal surface as a result of corrosion by chemically active fluids dislocations appear not to be a significant factor for crack nucleation below about 500 c in silicates spatial and temporal changes in temperature can also induce microcracking as a result of differential thermal expansion between grains with different thermoelastic moduli and thermal conductivities the amount of quartz in the rock has a significant effect on thermally induced microcracks because of its large and variable thermal expansivity the application of hydrostatic pressure between 100 and 200 mpa effectively closes most cracks but the closure may not be uniform if crack wall asperities exist hydrostatic pressure appears to stabilize cracks and make crack growth more difficult the number and average size of mechanically induced microcracks is greater in rock deformed at higher pressures the application of a deviatoric stress field on the boundaries of a rock mass results on a microscopic scale in a very complex stress system which greatly affects nucleation and propagation paths the relative amount of intragranular and intergranular cracking appears to depend upon mineralogy rock type and stress state the vast majority of stress induced microcracks in rocks appear to be extensional statistically they are predominantly oriented within 30 of the macroscopic maximum stress direction crack densities increase as macroscopic deviatoric stress increases above a threshold level crack size distributions may be either lognormal or exponential fracture in rock under compressive boundary loads is a result of the coalescence of many microcracks not the growth of a single crack some crack configurations are more favorable for coalescence than others as deviatoric stress increases and rock failure is approached the microcrack population changes spatially from random to locally intense zones of cracking away from the fault the crack density dies off rapidly to the background level a few grains away under lesser deviatoric stresses slow subcritical microcrack growth can occur as a result of stress aided corrosion at the crack tip the rate governing mechanism may be either the chemical reaction rate or the rate at which water can get to the crack tip important details still remain to be worked out

the stratigraphic and geochemical imprints of late ordovician glaciation on far field neritic carbonates anticosti island eastern canada abstract the storm dominated open marine neritic carbonate facies continuously exposed in coastal cliffs and wide rocky tidal flat exposures at the western end of anticosti island form a 315 m thick expanded section spanning the ordovician silurian boundary these carbonate facies display deepening shallowing trends of different orders resulting in a hierarchical stacking of sedimentary cycles the carbonate facies within these multi order cycles represent sediments that were deposited from shoreline to deeper outer carbonate ramp 80 m in water depth and exhibit sea level changes of several tens of metres in magnitude field petrographic and geochemical evidence support a well preserved primary 18o signal in close equilibrium with the original paleoenvironmental conditions the 18o intracycle variations up to 1 0 in magnitude reveal repeated decreasing and increasing values during the transgressive and regressive portions of decametre tr cycles respectively although temperature salinity and ice volume influenced the recorded primary 18o signal orbital scale glacioeustasy ultimately controlled facies and cycle development and 18o signal during the katian immediately before the latest ordovician hirnantian glaciation the 3 5 myr long 18o signal recorded by our entire succession supports a protracted period of cooling leading into the main phase of latest ordovician hirnantian glaciation spectral analysis of the 18o record also reveals decametre variations which are associated with decametre scale transgressive regressive tr cycles possibly reflecting eccentricity orbital signals our study shows the importance of a thick expanded stratigraphic succession sampled at the highest resolution possible to decipher potential linkages between facies changes multi order stratigraphic cycles 18o signal and the earth s orbital parameters

oxygen and strontium isotopes from fossil shark teeth environmental and ecological implications for late palaeozoic european basins article i nfo fossil shark remains occur in both marine and nonmarine late palaeozoic deposits therefore their palaeo ecology is controversial the oxygen and strontium isotopic composition of biogenic fluorapatite in 179 teeth scales and spines predominantly of hybodontid lissodus and xenacanthiform orthacanthus xenacanthus bohemiacanthus triodus sharks from various late carboniferous moscovian to early permian artinskian basins of europe are used as ecological tracers to decipher diadromous or obligate freshwater lifestyle of the investigated taxa the 18 op values of the different shark teeth range from 11 7 to 20 2 within the different basins with mean values of 16 9 0 5 for the bohemian massif 16 2 0 8 for eastern germany 18 2 1 0 for southwestern germany 18 5 0 7 for southern central spain 17 6 0 4 for