aerosols as dynamical tracers in the lower stratosphere ozone versus aerosol correlation after the mount pinatubo eruption stratospheric in situ aerosol and ozone measurements aboard the nasa operated er 2 high altitude research aircraft from august 1991 to may 1993 provide an opportunity to document the temporal evolution of the correlation between the stratospheric aerosol and the ozone from shortly after the mount pinatubo eruption until almost two years later the observations show that at midlatitudes a linear relationship evolves between aerosol surface or number mixing ratios and ozone at altitudes ranging from slightly above the tropopause to 14 16 km this correlation is linear for values of ozone from 200 to 1300 parts per billion by volume and for potential temperatures between 310 k and 467 k the linear correlation persisted from late december 1991 until early march 1992 but degraded by october 1992

trace fossils biology and taphonomy 1990 special topics in palaeontology 3 280 pp e17 95 pbk e40 00 hbk unwin hyman london isbn 004445 6867 pbk 3035 hbk

high resolution sequence stratigraphy of lower paleozoic sheet sandstones in central north america the role of special conditions of cratonic interiors in development of stratal architecture well known difficulties in applying sequence stratigraphic concepts to deposits that accumulated across slowly subsiding cratonic interior regions have limited our ability to interpret the history of continental scale tectonism oceanographic dynamics of epeiric seas and eustasy we used a multi disciplinary approach to construct a high resolution stratigraphic framework for lower paleozoic strata in the cratonic interior of north america within this framework these strata proved readily amenable to modern sequence stratigraphic techniques that were formulated based on successions along passive margins and in foreland basins settings markedly different from the cratonic interior parasequences parasequence stacking patterns systems tracts maximum flooding intervals and sequence bounding unconformities can be confidently recognized in the cratonic interior using mostly standard criteria for identification the similarity of cratonic interior and foreland basin successions in size geometry constituent facies and local stacking patterns of nearshore parasequences is especially striking this similarity indicates that the fundamental processes that establish shoreface morphology and determine the stratal expression of retreat and progradation were likewise generally the same despite marked differences in tectonism physiography and bathymetry between the two settings our results do not support the widespread perception that paleozoic cratonic interior successions are so anomalous in stratal geometries and constitute such a poor record of time that they are poorly suited for modern sequence stratigraphic analyses the particular arrangement of stratal elements in the cratonic interior succession we studied is no more anomalous or enigmatic than the variability in architecture that sets all sedimentary successions apart from one another thus paleozoic strata of the cratonic interior are most appropriately considered as a package that belongs in a continuum of variable stratigraphic packages reflecting variable controls such as subsidence and shelf physiography special conditions of exceptionally slow subsidence rate shallow bathymetry and nearly flat regional shelf gradient are manifest mostly by the presence of individual systems tracts of relatively long duration that extend for much greater distances across depositional strike than those that characterize successions deposited in more dynamic tectonic and physiographic settings these results suggest that if other cratonic interior successions are as anomalous as reported a low sediment supply may have played a primary role in development of their apparently condensed stratal architecture the results also lead us to suggest that a nonvegetated lower paleozoic landscape played a relatively insignificant role in the development of what are commonly perceived to be enigmatic stratigraphic features of sheet sandstones particularly their widespread yet thin geometry and a scarcity of shale and siltstone

late quaternary terraced marine deposits as tools for wide scale correlation of unconformity bounded units in the volcanic aeolian archipelago southern italy abstract late quaternary raised terraced marine deposits are commonly interlayered with volcanic deposits along the coasts of the aeolian archipelago they mostly reflect the interplay between long term crustal vertical movements and glacio eustatic sea level changes during marine isotope stages mis 5 and 9 key discontinuity surfaces are represented by those bounding terraced marine deposits formed in correspondence of recurrent individual interglacial sea level peaks they are the basal ravinement surface formed during gradual sea level rise at the onset of a sea level peak and the upper surface of subaerial erosion developed during ensuing sea level fall and lowstand the discontinuity surfaces are classified according to their sequence stratigraphic significance field documentation and areal extent mis 5 marine deposits are bounded by the first order ui and uii unconformities the ui unconformity is the ravinement surface formed during mis 5e sea level rise age between 130 and 124 ka the uii unconformity is the surface of subaerial erosion and non deposition developed during sea level lowering after mis 5a age 70 ka unconformities ui and uii are correlated throughout the entire aeolian archipelago thus assuming a regional stratigraphic significance by linking to the global sea level curve they are assigned a relative age and assume a substantial chronostratigraphic significance and potential for dating of volcanic rocks further correlation on most of the aeolian archipelago is provided by the l3 unconformity that is the ravinement surface formed during sea level rise of mis 5c 100 ka moreover the f1 unconformity bounds at the base marine deposits older than the last interglacial i e mis 9 and is ascribed of an inter island stratigraphic outcome these allogenic unconformities driven by sea level fluctuations allow definition of a regional unconformity bounded framework for the aeolian archipelago into which local volcanic successions subdivided by autogenic unconformities of volcanic origin may be arranged

wave ravinement surfaces classification and key characteristics abstract the wave ravinement surface wrs is a surface of sequence stratigraphic significance that forms in shallow water settings during transgression it develops progressively landward during shoreface retreat due to wave action which erodes the substrate and leads to sediment bypass in the offshore direction the wrs may rework previously formed surfaces such as the maximum regressive surface also known as the transgressive surface and the subaerial unconformity becoming a systems tract and or sequence boundary due to the associated lithological contrast between underlying and overlying deposits and the presence of lags and or shell pavements the wrs has a very good appearance in both outcrop and cores and is often used as the boundary of shallow marine stratigraphic sequences the wrs therefore represents an important lithological and paleo environmental break and its recognition is significant for reconstructing stratigraphic architectures and the history of relative sea level change as well as for reservoir characterization several controlling factors govern the development of the wrs and of the associated deposits they include the accommodation to sedimentation a s ratio environmental energy topographic gradient roughness and lithology of the substrate relatively low rates of relative sea level rise and sediment supply high wave energy steep topographies and easily erodible substrates favor the development of the wrs these factors interact leading to a high variability in the amount of erosion shape length along depositional dip and deposits associated with these surfaces wrss may be classified based on either underlying or overlying deposits or a combination of both a classification based on the deposits that underlie the wrs helps to determine the location of the studied outcrop along depositional dip whereas a classification based on the deposits that overlie the wrs afford insights into the physical conditions that accompanied its formation however the best description of the wrs in terms of location of a considered outcrop physical conditions under which the wrs developed and their lateral variability type of substrate as well as its practical significance for reservoir modeling is achieved with a combination of the two criteria

sage ii measurements of early pinatubo aerosols sage ii satellite measurements of the mt pinatubo eruption cloud in the stratosphere during june july and early august 1991 show that aerosols in the tropics reached as high as 29 km altitude with most of the cloud between 20 and 25 km the most optically thick portions of the cloud covered latitudes from 10 s to 30 n during the early part of this period by late july high stratospheric optical depths were observed to at least 70 n with the high values north of about 30 n from layers below 20 km high pressure systems in both hemispheres were observed to be correlated with the movement of volcanic material at 21 km into the westerly jet stream at high southern latitudes and similarly to high northern latitudes at 16 km by august the entire southern hemisphere had experienced a 10 fold increase in optical depth relative to early july due to layers above 20 km initial mass calculations using sage ii data place the aerosol produced from this eruption at 20 to 30 megatonnes well above the 12 megatonnes produced by el chichon

eoalpine and mesoalpine tectonics in the southern alps according to structural and stratigraphic data eoalpine and mesoalpine tectonics can be clearly recognized in the southern alps and distinguished from the better known neoalpine deformation

marine and nonmarine deposition in a long term low accommodation setting an example from the middle pleistocene qm2 unit eastern central italy abstract facies anatomy and large scale stratigraphic organization of mid pleistocene strata qm2 unit exposed near the town of ortona eastern central italy have been defined through an integrated outcrop and subsurface dataset and record sedimentation within a long term low accommodation setting the studied interval can be subdivided into nine facies associations reflecting a range of continental marginal marine nearshore and innermost shelf environments and contains a well preserved record of high frequency relative sea level changes in the form of a stack of three unconformity bounded sequences each of the three sequences designated qm23 qm22 and qm21 from oldest to youngest consists of a specific subset of the nine identified facies associations as a function of preserved depositional systems and systems tracts typically the following architectural elements occur in ascending stratigraphic order i a basal unconformity molded by fluvial incision and subaerial exposure during sea level fall and shoreface erosion during subsequent rise ii a maximum regressive surface which is coincident with the sequence boundary iii a transgressive systems tract including braided river conglomerates and floodplain fines within the confines of an incised valley palustrine carbonates and back barrier lagoon mudstones and a deepening and fining upward shoreface to offshore transition facies succession bounded at the base by a wave ravinement surface iv a sharp regressive surface of marine erosion produced by shoreface incision during relative sea level fall and v a prograding downstepping and offlapping sharp based lithofacies assemblage of either beach conglomerates or sandstones ascribed to the falling stage systems tract overlain by a rooted paleosol marking subaerial exposure sequences were deposited on the uplifting palaeo adriatic shelf in response to repeated high frequency and high amplitude eustatic changes in sea level that would promote the creation of accommodation space by subtracting space to deposition the contemporaneous regional uplift of the basin margin may be accounted for the shingled downstepping configuration of individual sequences to form a falling stage sequence set of a larger composite sequence in dip view the erosional contact at the base of the qm2 falling stage sequence set is a composite regressive surface resulting from the downdip convergence and amalgamation of multiple erosional surfaces produced by the progressive basinward translation of successive sequences results from this study have direct implications for the oil and gas field development and exploration when making predictions of reservoir and seal geometries within shallow marine marginal marine and nonmarine sediments emplaced in similar long term limited accommodation settings

a strand plain soil development sequence in northern michigan usa abstract a practical problem limiting the theoretical application of a soil chronosequence study lies in the difficulty of identifying an appropriate geomorphic age sequence with more than a few surfaces a sequence of approximately 75 strand plain beach ridges located along the northern shore of lake michigan usa overcomes this problem and was used to explore rates of soil development in the initial stages of podzolization well drained pedons were sampled on 24 of the ridges with an age range of 10 to 5200 years chronofunctions were developed using statistical regression techniques for most forms of extractable fe and al both linear and log linear functions adequately describe the changes in property with surface age dithionite citrate extractable fe content however shows little correlation with surface age high r 2 values 0 7 for chronofunctions representing most extractable sesquioxide forms suggest that b horizon sesquioxide content increases with surface age as expected for soils undergoing podzolization visual inspection of chronofunction data suggests that scatter increases on surfaces older than 3000 years possibly because soil spatial variability increases with surface age theory suggests that the log linear form of chronofunctions may be preferable to the linear form for these pedons in general equation slopes are steeper for chronofunctions representing only the initial 1650 years of soil development than for those representing the entire 5200 year sequence suggesting that initially rapid pedogenesis slows over time most chronofunctions for ph and weighted profile organic c are not statistically significant possibly because the temporal resolution of the chronosequence is too coarse to detect valid trends for properties that rapidly approach a steady state

stratigraphic condensed deposition and diagenetic evolution of green clay minerals in deep water sediments on the ivory coast ghana ridge abstract green grains concentrations were studied through the 22 m pleistocene sedimentary column recovered from ocean drilling project site 959 in 2100 m water depth located on a small plateau on the northern flank of the cote d ivoire ghana marginal ridge the green clay material usually fills the chambers of pelagic foraminifers taking into account the variance in color and mineralogic composition of the bulk green grains fraction observed in each level a methodological approach was especially performed mineralogical and chemical analyses were done successively on the bulk green material then on hand picked white pale green medium green and dark green grains and lastly surface and spot analysis of nanno structures were obtained using an energy dispersive microprobe coupled with a scanning electron microscope green grains concentrations are evidenced showing both rising up of green white ratio and increasing abundance of cracked dark green grains these irregular concentrations are not consistent directly with a general climatic forcing as evidenced by 18 o isotopic curve but are the result of recurrent bottom current activity thus winnowing process is the cause of the long lasting ionic exchange and mineralogical evolution at the water sediment interface clay infilling composed of smectite 35 40 kaolinite 45 50 traces of mica calcite and quartz was a precursor material along with dissolution of kaolinite crystallochemical modifications of smectites were observed both to the sequential concentration scale bulk samples and to the individual grain scale from white to dark green increment of fe content associated decrease of al and increase of layer charge and k content in the layers with the highest green grain concentrations and in agreement with crystallochemical formulae fe 3 rich montmorillonite displays octahedral charge tetrahedral charge appears only when fe content increased 1 2 fe per formulae with the maturation process the growing of the closed layers is observed mixed layer smectite glauconite 80 20 nearly similar evolution patterns were recorded at various levels 0 01 0 85 2 2 ma of the pliocene pleistocene accumulation however the nontronite way is evidenced in the lowest green grains concentrations and remind the previously described shelf processes independently of the morphologically induced winnowing in these marine tropical deposits the glauconitization process was especially favored by abundant iron supply and was not affected by low temperature 3 c it is suggested that in deep water environment bottom current controlled iron deposition and disponibility strongly influencing the mineralogic evolution a too lengthy dispersal of iron microparticles played an ultimate role in the development of the montmorillonite way rather than the nontronite way this would be the most commonly found in shallow water environment

integrated ichnology and ichthyology of the oligocene menilite formation skole and subsilesian nappes polish carpathians a proxy to oxygenation history the anoxic mostly black or brown fine grained sediments of the menilite formation oligocene early miocene in the skole and subsilesian nappes contain thin layers of bioturbated green or grey green mudstones some of which contain the trace fossils halimedides annulata multina isp palaeophycus tubularis planolites isp rhizocorallium isp trichichnus isp and zoophycos isp the trichichnus palaeophycus multina halimedides rhizocorallium suite indicates an increase in oxygenation of sediments the contribution of different ecological groups of fishes including epipelagic bathypelagic benthopelagic neritic and reef and demersal taxa changes significantly through the menilite formation the absence or reduction of bathypelagic fishes points to anoxia in the water column the combination of ichnological and ichthyological data and incorporation of data on benthic foraminifers allowed a reconstruction of oxygenation changes in the sediment and water column during deposition of the menilite formation total anoxia at the sea floor and in the water column attributed to a combination of thermo stratification and extremely high organic productivity occurred only during the period reflected by ichthyofaunal zone ipm2 middle part of the np23 zone anoxia restricted to the basin floor or upper slope related in part to upwelling occurred during sedimentation of the upper part of the menilite formation

sequence stratigraphic and sedimentologic significance of the trace fossil rhizocorallium in the upper triassic nayband formation tabas block central iran abstract this study analyzes in detail the beds bearing rhizocorallium in the upper triassic nayband formation tabas block central iran and shows their potential in interpreting depositional settings ecological features and sequence stratigraphy an integrated approach combining ichnological sedimentological and stratigraphic methods has significantly enhanced our understanding of the changes in the spatial distribution style and morphological differences among the same ichnospecies of rhizocorallium the upper triassic rhizocorallium assemblages from the nayband formation reveal significant spatial variations in the orientation and dimensions i e length width limb diameter the tiering pattern and the colonization style throughout systems tracts and at erosional discontinuities or omission surfaces based on the wide variety of forms and orientation numerous morphotypes of rhizocorallium are grouped into two main types i e those that are mostly facies controlled and those that appear abundantly in a confined stratigraphic interval and are facies independent in this respect three paleoichnocoenoses or habitats for the rhizocorallid producers could be differentiated according to the burrow morphology and the nature and consistency of the substrate 1 stable habitat represented by soft substrates including horizontal long straight or slightly sinuous spreite bearing u shaped protrusive burrows of rhizocorallium irregulare r commune var irregulare this habitat resulted from processes operating in settings that are characterized by soft substrates reduced sedimentation rates and abundant food supply typical of low to moderate energy fully marine conditions 2 unstable physically controlled habitat represented by a suite of shifting substrates with low to high energy settings including short u shaped protrusive spreiten burrows of r jenense type 1 in this habitat alternating and contrasting energy conditions did exist due to repeated storm events that were the main controlling factor in the distribution and preservation of rhizocorallium 3 substrate controlled habitat represented by a suite of stiff to firm substrates including oblique to vertical protrusive or retrusive spreiten u shaped burrows of r jenense type 2 the erosional discontinuities or omission surfaces related to this habitat include parasequence bounding transgressive surfaces of erosion tse and parasequence bounding flooding surfaces fs and are mainly associated with the rhizocorallium dominated glossifungites ichnofacies complementary ichnological information indicates that the shift in the orientation and the morphological features of rhizocorallid burrows point to broad changes of environmental parameters which are in turn controlled by the rate of sea level changes

ichnofabrics of a pleistocene slope succession new jersey margin relations to climate and sea level dynamics abstract trace fossil and sedimentologic data were collected at 10 cm intervals throughout a virtually continuous 520 m thick upper pleistocene siliciclastic succession recovered at odp site 1073 new jersey margin these data were examined in the context of isotopic seismic and palynologic proxies to document depositional and ichnologic responses to quaternary climate and sea level dynamics in an upper slope setting two broad texturally defined sedimentary facies assemblages are recognized the clay rich assemblage reflects relatively rapid deposition in part from turbidity currents and suspended plumes and appears to be linked to cooler sea level fall and lowstand phases the sand rich assemblage reflects overall slower sedimentation by offshelf spillover and periodic winnowing and erosion under the influence of contour and other bottom currents during warmer transgressive highstand phases facies of the sand rich assemblage muds sandy muds muddy sands and sands are completely bioturbated and are characterized by high densities of biogenic structures including distinct burrow forms in contrast the clay rich assemblage includes facies that exhibit limited biogenic disruption laminated clay silty clay and graded silt or fine sand to clay couplets and on the whole is characterized by lower densities of biogenic structures most of which are diffuse burrow mottles these ichnofabric trends reflect changes in ecological and taphonomic parameters e g substrate stability and consistency residence time of sediments in the benthic boundary layer and degree of inter and intrabed textural variability many of which were governed by variations in sedimentation rate as mediated by glacio eustacy recurring identifiable ichnofossils are most common in facies of the sand rich assemblage in the upper half of the pleistocene succession finer grained components of this assemblage e g muds and sandy muds representing quieter phases of highstand deposition are characterized by a low diversity distal cruziana ichnofacies assemblage dominated by schaubcylindrichnus and phycosiphon anconichnus both of which represent the work of deposit feeding worms narrow facies transitions that correspond to phases of rapid transgression are marked by occurrences of thalassinoides these crustacean burrow systems were excavated in coarser grained higher energy facies sands and muddy sands and in closely associated firmground substrates produced by exhumation of consolidated muds by bottom currents and or mass wasting processes the association of firmground ichnofabrics with marine flooding events in an upper slope setting demonstrates that the sequence stratigraphic utility of the glossifungites ichnofacies extends beyond shelf depositional sequences to deeper water deposits the distribution of texturally defined facies and general ichnofabric parameters e g degree of bioturbation appears to respond to glacio eustatic cycles through the entire pleistocene record however the schaubcylindrichnus phycosiphon assemblage and thalassinoides are rare or absent altogether in the lower half of the succession indicating that biological responses to and the ichnologic record of climate and sea level dynamics may be strongly dependent on margin physiographic and bathymetric evolution

fracture networks on the belluno syncline a fault propagation fold in the footwall of the belluno thrust venetian alps ne italy

components facies and ramps redefining upper oligocene shallow water carbonates using coralline red algae and larger foraminifera venetian area northeast italy abstract chattian mixed carbonate siliciclastic deposits from two palaeogeographic units of southern alps the lessini shelf and venetian foreland basin of northeast italy are studied with respect to facies distributions and controlling ecological factors on dominant biogenic components these ramp depositional systems are located in the western southern alps on the lessini shelf and in the eastern southern alps in the venetian foreland basin the successions show an extensive geographic distribution of at least 150 km 40 km at the southern margin of the southern alps palaeoenvironments are inferred following microfacies characteristics and floral and faunal indicators especially those of coralline red algae and larger foraminifera an inner to middle homoclinal ramp morphology is reconstructed based on facies distributions and taxonomic and coralline algal growth form proxy data the distribution along depositional strike shows variation from thinner carbonate dominated sequence in the west monti berici and monti lessini to a more variable mixed carbonate siliciclastic dominated environment to the east vittorio veneto alpago facies character and occurrence are controlled by local hydrodynamic conditions and varying water turbidity of the studied ramp depositional system the general facies succession shows a transgressive sequence from the proximal inner to proximal middle ramp a shoal belt of trough cross bedded sandstones occurs in a proximal inner ramp position in all of the studied areas in a gentle dipping homoclinal ramp most benthic organisms inhabited the relatively quite environments off these shoals in a distal inner ramp setting basinward environments proximal middle ramp constitute areas of maximal carbonate production and consist primarily of larger foraminiferal facies and rhodolith pavements larger foraminifera represented by two larger foraminiferal assemblages are most diversified in the shallower settings near the fair weather wave base distal inner proximal middle ramp whereas coralline algae predominate in deeper areas proximal middle ramp constructing extensive rhodolith pavements rhodolith pavements are distinguished with respect to rhodolith shape size growth forms and coralline algal taxonomic composition larger foraminifera are interpreted with respect to shell structures shell architectures and comparable recent counterparts the analysed benthic communities thrived in a mesotrophic regime within trophic gradients constrained by fluvial influence coralline algal dominance and a moderately diverse larger foraminiferal assemblage suggest a tropical warm temperate transition the considerable stability imposed on sediments by the rhodolith pavement must also have significantly contributed to the maintenance of a middle ramp profile bulge this study will contribute to a better understanding of oligocene carbonates which have received less attention than their eocene or miocene counterparts

ichnology of an eocene shallow marine passive margin condensed section eastern gulf coastal plain alabama u s a abstract exposures of the eocene tallahatta formation in southern alabama u s a provided the opportunity to document the ichnologic character of a highly condensed passive margin transgressive systems tract and its two component parasequences the studied succession is dominated by variably glauconitic fossiliferous muddy sands deposited in shallow marine shelf settings thorough bioturbation and abundance of mud indicate quiet background conditions whereas admixed sand and localized scour features indicate periodic influence by bottom currents parasequences delineated based on vertical trends in glauconite abundance are bounded at their bases by flooding surfaces marked by thalassinoides dominated firmground ichnofabrics but internally host moderately diverse cruziana ichnofacies assemblages recurring softground ichnofossils include asterosoma chondrites diopatrichnus ophiomorpha planolites rosselia teichichnus thalassinoides and enigmatic composite structures the distributions and abundances of which vary within and between parasequences increasing prominence of diopatrichnus and rosselia towards parasequence tops reflects organismal responses to environmental changes associated with shallowing and or enhanced preservation potential of shallow tier structures in response to increased sedimentation rates maximum sediment starvation during deposition of the uppermost parasequence is reflected by peaks in burrow density softground ichnofossil diversity and concentrations of entobia bored shells and teredolites bored logs enigmatic composite burrows and common thalassinoides with linings and or meniscate backfills are ubiquitous and may be diagnostic of sediment starvation and prolonged habitation of slowly accreting substrates

observations of pinatubo ejecta over boulder colorado by lidars of three different wavelengths noaa lidars at wavelengths of 0 574 0 694 and 10 591 m have observed ejecta from the eruption of mt pinatubo both in the troposphere and stratosphere over boulder colorado since july 27 1991 multilayered clouds have been highly variable on time scales of minutes to days measurements at multiple wavelengths provide valuable information on size distribution and the wavelength dependence of backscatter and optical depth

trypanites ichnofacies palaeoenvironmental and tectonic implications a case study from the miocene disconformity at foz da fonte lower tagus basin portugal abstract a well preserved bioeroded surface occurs at the unconformity separating cretaceous limestones and lower miocene sediments outcropping on the western coast of the peninsula of setubal central west portugal the ichnoassemblage present in this bioeroded surface is herein assigned to the trypanites ichnofacies the preservation characteristics of the borings reflect several episodes of encrustation boring and physical erosion the erosional truncation of bioerosive structures and the predominant preservation of the largest borings gastrochaenolites isp in the ichnocoenoses are herein related with repeated phases of bioerosion and physical abrasion occurred during an early miocene transgressive pulse the recognition of this bioeroded transgressive surface also allowed confirming the presence at that time of an emergent topographic relief related to salt domes formed earlier probably already during palaeogene times

trace fossils and ichnofabrics on the lower muschelkalk carbonate ramp triassic of germany tool for high resolution sequence stratigraphy in the german triassic of thuringia the lower muschelkalk sequence can be subdivided by application of ichnological methods three ichnofacies with five ichnofabrics are described in accordance with the lithological features trace fossils are found to defining parasequences on the basis of a regular change of bioturbation furthermore it is possible to establish deepening upward cycles the reconstruction of parasequences allows the establishment of a high resolution sequence stratigraphy the position of the maximum flooding surface can be identified in the terebratula member and is developed in a condensed interval the most significant of the additional major marine flooding surfaces is found at the top of the upper oolith bed characterized by lithostratigraphy ichnology biostratigraphy and parasequence thickness trends

ichnological analysis in high resolution sequence stratigraphy the glossifungites ichnofacies in triassic successions from the betic cordillera southern spain this study integrates ichnological and sedimentological data in order to refine sequence stratigraphy and interpretations of sea level dynamics for the ladinian middle triassic muschelkalk succession siles formation in the betic cordillera southern spain facies analysis was integrated with a detailed ichnological study focused on the middle part of the lower member of the muschelkalk succession transgressive systems tract which is characterized by an abundant and conspicuous trace fossil assemblage seven lithofacies were recognized recording sediment accumulation in tidal flat and inner to outer marine carbonate ramp depositional environments thin bedded marly limestones with bioclastic shelly beds facies e middle ramp with storm influence are characterized by diplocraterion and rhizocorallium diplocraterion is protrusive usually eroded on top and mainly recorded in the marly limestone intervals rhizocorallium preserves well defined scratch marks and is commonly emplaced in bioclastic shelly beds the assemblage represents the glossifungites ichnofacies sedimentological and ichnological data are interpreted to record a complex transgressive context associated with high frequency sea level dynamics that allowed formation of transgressive surfaces of erosion tse i e ravinement surfaces of different orders major tse associated with continuous bioclastic shelly beds delimit parasequences the absence of the glossifungites suite reveals that there was little time between erosion and deposition intermediate tse associated with discontinuous shell beds are related to comparatively less significant sea level rises and occur within parasequences the glossifungites suite reveals colonization of firmgrounds during relatively prolonged times between erosion and deposition related to intermediate tse minor order tse recorded between the intermediate tse are related to punctuated highest frequency sea level changes phases of colonization by the diplocraterion tracemaker and protrusive capped structures reveal more or less stillstand phases tse stillstand phases and minor order erosional phases

substrate control on formation and maturation of glauconites in the middle eocene harudi formation western kutch india formation and maturation of glauconites within the early middle eocene harudi formation built up in a lagoon to shelf transition in western kutch india is addressed taking recourse to a combined sedimentological micropalaeontological and mineralogical investigation the glauconite is authigenic and its occurrence coincides with maximum flooding the glauconite is more matured within the fecal pellets and is less matured within the intra particle pores of bioclasts namely foraminifera ostracoda gastropoda and bryozoa sem eds xrd and geochemical studies clearly document that the infilling within the intra particle pores of bioclasts belong to nascent to slightly evolved glauconite 5 wt k2o while the pellet belongs to slightly evolved to evolved glauconite 5 7 wt k2o based on chemical characteristics and sem investigations the glauconitization process can be best explained by the verdissement theory the glauconite possibly formed as initial authigenic glauconitic smectite precipitates while the pellet matured subsequently by addition of k the process was hindered in case of infillings the maturation process also involved addition of si and release of al with or without release of mg the glauconite maturation was facilitated in case of fecal pellets because of higher porosity inter granular nature of pores and availability of necessary elements in semi confined micro environments in contrast the maturation was aborted at an early stage in case of infillings because of the minute closed nature of the pores and prevalent alkaline conditions not allowing dissolution of calcitic tests a low negative cerium anomaly suggests glauconite formation in sub oxic micro environments created by decay of organic matters within the fecal pellets and bioclasts a clear case of substratum control on glauconitization becomes apparent

early lidar observations of the june 1991 pinatubo eruption plume at mauna loa observatory hawaii the june 1991 eruption of the philippine volcano pinatubo introduced a massive plume of volcanic ash and other aerosol material into a stratosphere containing only near background concentrations of aerosol material at mauna loa observatory hawaii the pinatubo plume was first observed by lidar on 1 july 1991 during july and august the observable effects from this plume increased in intensity in terms of aerosol optical properties plume height and broad band solar radiation preliminary data analysis shows that the plume over hawaii arrived in three generalized pulses or waves on approximately 3 july 24 july and 9 august there was a decrease of about 13 in a broad band atmospheric transmission factor over hawaii between june 1991 and pinatubo affected conditions on 31 august 1991 at the end of august 1991 the pinatubo plume over hawaii exhibited characteristics similar in magnitude to what was observed at mauna loa after the el chichon eruption in 1982 however the early pinatubo maximum plume heights were lower than were observed in the early months of the el chichon plume dispersion the pinatubo plume was continuing to increase in magnitude and height at mlo at the end of august

influence of subsidence on the anatomy of marine siliciclastic sequences and on the distribution of shell and bone beds skeletal concentrations are common foci for palaeontological collecting yet vary widely in their expected levels of taphonomic bias depending on whether they are comparatively simple event concentrations more complex accretionary accumulations of either normal or condensed thickness or residual lags that mark horizons of significant erosional corrosional truncation of the record table 1 these different types and their intermediates also have different potential for use in basin analysis for example as marker beds bathymetric indicators and clues to hiatuses the stratigraphy and taphonomy of marine siliciclastic sequences from a spectrum of basin types have been examined to determine the extent to which shell and bone beds are linked to physical stratigraphic features such as discontinuity surfaces and transgressive regressive cycles at various scales and thus the extent to which physical processes might influence palaeontological data this series of basin scale studies has also provided an opportunity to assess the practical utility of skeletal concentrations in reconstructing basin history and to investigate subsidence related variation both in skeletal accumulation and in the anatomy of siliciclastic sequences field studies have been restricted to post palaeozoic primarily neogene sections in warm temperate to subtropical palaeolatitudes and have focused on marine facies tracts developed in shelf and shallower water depths during phases of coastal onlap sequence stratigraphic terms are used here to describe physical aspects of the record and do not imply any particular chronostratigraphic value or genetic i e eustatic origin the results of this work indicate that a skeletal concentrations are distributed fairly systematically within marine sequences both in

penetration of mt pinatubo aerosols into the north polar vortex observations of the mount pinatubo cloud as it moved northward and into the winter polar vortex were made with a balloon borne two wavelength backscattersonde some volcanic debris had arrived at far northerly latitudes below 20 km by october and was apparently incorporated into the initial vortex subsequent measurements did not show a significant increase in the central vortex aerosol until after a mid january disturbance at which time the backscatter profiles began to increase above 20 km and near the center of the vortex there was no significant increase in aerosol through mid march the column stratospheric aerosol mass loading as calculated from individual soundings at the wall of the vortex during march 1992 ranged from 18 to 24 megatonnes per unit area where the unit of area is that of the earth this indicates that a significant amount of material was transported northward by the end of the winter

shell beds as tools in basin analysis the jurassic of kachchh western india skeletal concentrations are ubiquitous in bathonian oxfordian shallow water sediments of the pericratonic basins of kachchh and rajasthan western india by analysing the biofabric of the concentrations and the taphonomic signatures of individual components it is possible to distinguish between the final concentration process recorded by the biofabric and events taking place prior to final deposition recorded by taphonomic signatures the skeletal concentrations are grouped in nine genetic types ranging from fair weather wave concentrations to storm concentrations and condensed concentrations they mainly reflect biological and hydraulic processes and in some instances permit estimates of their duration and show a rough zonation along a bathymetric gradient plotted against the stratigraphic sections the skeletal concentrations show in accordance with other sedimentological data three orders of bathymetric trends the first two orders are shallowing deepening cycles which possibly correspond to eustatic changes in sea level the third order represents parasequences with a strongly asymmetric sedimentary record skeletal concentrations are a useful additional tool in basin analysis but are best used in combination with other data

use of trace fossils in delineating sequence stratigraphic surfaces tertiary venetian basin northeastern italy abstract the lowermost third order sequence of the venetian molasse basin upper chattian lower aquitanian in the belluno syncline is composed of a transgressive systems tract comprising a basal condensed glauconitic sand sheet deepening upwards into finer grained offshore deposits and a highstand systems tract mainly consisting of prograding offshore mudstones capped by very fine sandstones representing offshore transition deposits an integrated sedimentological ichnological and micropaleontological approach has allowed the recognition of the internal organization of the sequence the subdivision into parasequences in absence of an obvious physical expression and the characterization of significant discontinuity surfaces at both sequence and parasequence scales the transgressive surface shows a complex geometry of bored and encrusted cavities produced by erosional undercutting and a system of neptunian dykes and sills with hiatal shell concentrations as infill component parasequences in the texturally homogeneous transgressive sand sheet can be identified on the basis of the preservational state of trace fossil assemblages softground versus firmground conditions and subtle changes in grain size and glauconite content omission surfaces bounding the parasequences are marked by increased glauconite content and densely crowded predominantly vertical or oblique relatively large very distinct thin walled or unwalled and uncompacted burrows the condensed section coincides with highest values in relative abundance of planktic foraminifers and in diversity of benthic foraminifers parasequence bounding flooding surfaces in the muddy offshore portion of the highstand systems tract are recognized as firmground surfaces mantled by thin shell concentrations in a matrix of silty highly burrowed glauconitic sand