the foreslope and toe of slope facies of the middle triassic latemar buildup dolomites northern italy abstract the latemar buildup was a circular carbonate buildup 4 km wide with a central platform core flat bedded interior platform and massive reef margin flanked on all sides by slope facies steeply dipping 30 35 foreslope breccias are present adjacent to the margin and flat lying graded grainstones at the toe of slope slope facies relate directly to depositional profile and slope angle the steeply dipping foreslopes consist of lobate breccia beds that are 25 m thick and a few tens of meters across and extend tens to hundreds of meters downslope some beds are conformably overlain by thinner 1 m thick beds of finer grained carbonate sediment the basal surfaces of the breccias are erosional and are anastamosing in both strike and dip views the breccia rains was derived principally from margin boundstones and deposited by rockfalls and avalanches planar clinoforms extend the entire height of the foreslope hundreds of meters and bracket depositional units clinothems tens of meters thick clinoforms appear to be shear surfaces formed during large slope failures avalanches graded grainstone beds less than 1 m thick are present at the nearly flat lying toe of slope these consist of redeposited shallow water platform interior and reef margin carbonate sands some with nodular limestone caps that are interpreted as proximal carbonate turbidites toe of slope breccias are the downdip extensions of foreslope breccias and pinch out abruptly basinward some slope depositional processes are related to high frequency fourth order and fifth order sea level changes toe of slope graded grainstones correspond to times of platform submergence in contrast foreslope breccia was deposited during both platform submergence and exposure the slope deposits do not record the high frequency cyclic rhythms identified in shallow water platform sections this is attributed to the nature of slope deposition downslope talus transport was episodic and localized graded grainstone beds reflect storm redeposition

the challenging retrieval of the displacement field from insar data for andesitic stratovolcanoes case study of popocatepetl and colima volcano mexico abstract despite the ability of synthetic aperture radar sar interferometry to measure ground motion with high resolution application of this remote sensing technique to monitor andesitic stratovolcanoes remains limited specific acquisition conditions characterizing andesitic stratovolcanoes mainly vegetated areas with large elevation ranges induce low signal coherence as well as strong tropospheric artefacts that result in small signal to noise ratio we propose here a way to mitigate these difficulties and improve the sar measurements we derive ground motions for two of the most active mexican stratovolcanoes popocatepetl and colima volcano from the time series of sar data acquired from december 2002 to august 2006 the sar data are processed using a method that combines both persistent scatterers and small baseline approaches stratified tropospheric delays are estimated for each interferogram using inputs from the global atmospheric model narr up to a maximum of 10 rad km these delays are validated using spectrometer data as well as the correlation between the wrapped phase and the elevation the tropospheric effect is removed from the wrapped phase in order to improve the unwrapping process on popocatepetl we observe no significant deformation the colima summit area exhibits a constant subsidence rate of more than 1 cm year centered on the summit but enhanced reaching more than 2 cm year around the 1998 lava flow we model this subsidence considering both a deflating magma source at depth and the effect of the eruptive deposits load

seismic energy releases from volcanoes seismic energy release during the precursory eruptive and declining stages of volcanic activities provides various information about the mechanisms of volcanic eruptions and the temporary developments of their activities hitherto the energy release patterns from precursory earthquake swarms were used to predict the eruption times especially of andesitic or dacitic volcanoes in this paper the discussion is expanded to quantify the total amount of seismic energy released at the threshold of volcanic eruptions with reference to the results observed at several volcanoes the results generally indicate that the cumulative seismic energy release from the precursory earthquake swarms exceed 1017 18ergs before eruptions at any andesitic or dacitic volvanoes this allows the seismic efficiency or the ratio of energy radiated seismically and the energy required for the volumetric expansion to be estimated by incorporating available deformation data with the seismic data the dependency of seismic efficiency on the type of volcanic activity i e non explosive outbreaks phreatic and magmatic eruptions dome formation etc was evaluated from observations at a few volcanoes that provided a variety of examples

the latemar a flat topped steep fronted platform dominated by microbialites and synsedimentary cements abstract facies analyses on the latemar isolated carbonate platform suggest a higher proportion of microbial carbonates compared to literature this is evident especially in the margin upper slope zone where microbial boundstone associated with tubiphytes calcareous sponges botryoidal aragonite and radiaxial fibrous cements extended down to 250 m water depth the latemar flat topped high relief platform has been subdivided into five different facies belts inner and outermost platform margin upper and lower slope each facies belt represents subtidal environments except for the inner platform which is characterized by a peritidal facies association point counting analysis was carried out on ca 90 thin sections to quantify the different platform components microbialite and cements are most abundant they represent respectively ca 40 and ca 34 of the whole platform volume these results suggest that carbonate production at latemar occurred in a m factory microbial carbonates as well as early marine cements are most abundant on the upper slope margin and outermost platform although microbialites are found in all facies belts the presence of supratidal sedimentary facies restricted only to the inner platform and of a completely subtidal outermost platform suggests a new depositional profile for the latemar the central portion is occupied by the flat platform interior cyclically subaerially exposed facies of the subtidal outermost platform surround the inner platform and display a progressive increase in depth toward the margin the margin is submerged and essentially constituted by microbial and cement boundstone the slope is characterized by steep clinoforms 35 dominated by in situ microbialites in the upper middle portion 0 250 m depth evidently precipitated by non light dependent microbially influenced processes the lower slope is mostly detrital poor in platform top derived sediments and dominated by margin and upper slope derived rudstone and grainstone all these observations are in agreement with the slope shedding model observed in the pennsylvanian microbial margin in asturias n spain and allow the interpretation of the latemar as a flat topped steep fronted platform dominated by microbialites and cement boundstones

large scale progradation demise and rebirth of a high relief carbonate platform triassic lombardy southern alps italy abstract the upper anisian to early carnian succession of the middle val brembana pegherolo massif central southern alps of italy records a complete depositional cycle from platform inception to growth demise and rebirth the depositional architecture of this system reflects different evolutionary stages an inception stage which postdates a previous drowning of an anisian carbonate platform with progradation of the carbonate platform from the nucleation areas an aggradational stage with increasing water depth in the basins a progradational stage where steep slopes composed of margin derived breccias develop and a final crisis corresponding to the subaerial exposure of the platform top followed by the deposition of shales in the basin before the rebirth of a different type of carbonate factory the record of this evolution reflects the effects of the change in accommodation space interplay of subsidence and eustacy which controls the type and storage sites of the sediments produced by the carbonate factory the effects of the changes in accommodation space are recorded in the shallow water platform as well as in the intraplatform basins where the sediments delivered at different rates from the platform top are stored as a consequence the aggradational stage corresponds to reduced sedimentation in the basins i e sediments are stored on the platform top whereas during progradation resedimented limestones are more common in the basin subaerial exposure rapidly halted the carbonate production on the platform top while a major input of shales probably reflecting a climate change and or lowering of the base level is recorded in the basin where shales onlap the slope of the previous carbonate system the rebirth of the carbonate factory after subaerial exposure of the platform top is characterized by a different composition of the carbonate factory probably reflecting changes of the environmental conditions the step by step recording of the evolution of the carbonate system represents a unique opportunity to record a seismic scale complete evolutionary cycle of a carbonate system in its different sub environments from the platform top to the basin

facies changes in the triassic jurassic boundary interval in an intraplatform basin succession at csővar transdanubian range hungary a continuous pelagic marine triassic jurassic boundary section is exposed in newly excavated trenches in the surroundings of cso var ne of budapest hungary in the late triassic this area was located close to the offshore margin of the dachstein carbonate platform system that was segmented by intraplatform basins based on detailed facies analysis of the rhaetian hettangian platform foreslope basin succession a long term second order and superimposed shorter term third and fourth order changes of the relative sea level could be revealed after a period of highstand platform progradation in the late norian large amounts of larger plant fragments and sporomorphs of continental plants mark a significant sea level drop in the early rhaetian presumably exposing large parts of the platform a renewed transgression led to the formation of smaller build ups fringing the higher parts of the previous foreslope crinoid meadows may have occupied the slopes a potential source area of the bioclastic carbonate turbidites rising relative sea level that followed the marked early rhaetian lowstand is also reflected in the general facies trend from lithoclastic debris flows and proximal to the very distal turbidites and radiolarian basin facies up to the earliest hettangian meter scale high frequency probably fourth order deepening upward cycles probably indicating sea level oscillation could also be recognized within this interval at the base of the last rhaetian cycle about 10 m below the assumed tr j boundary the amount of bioclasts including conodonts drastically decreases biotic decline in the radiolarian basin facies characterizing the topmost part of this cycle a significant negative shift in both the d 13 ccarb and d 13 corg and a marked decrease in the organic material toc was recognized that can be interpreted to reflect reduced productivity in connection with the triassic jurassic boundary event it is overlain by a lithoclastic horizon then by laminites where the last conodonts were found the next significant facies change in the early hettangian is marked by appearance of redeposited oncoid grapestone beds suggesting survival of shallow marine carbonate factories in the neighborhood of the basin and the end of the rhatian to earliest hettangian sequence third order the recurrence of basin facies above this interval indicates a new short term third order transgression and continuation of the long term second order deepening trend in the early hettangian d 2004 elsevier b v all rights reserved

origin dimensions and distribution of remobilized carbonate deposits in a tectonically active zone eocene thebes formation sinai egypt abstract determination of the distribution and mechanism for carbonate dominated mass transport sediments is often compromised by the scale and access to exposures consequently many studies lack the resolution to capture the heterogeneity and dimensions of mass transport deposits this study documents the size shape and stratal assemblage of remobilized carbonates in the eocene thebes formation in the hammam faraun fault block hffb of western sinai revealing the complexities of carbonate mass transport deposits at sub seismic scale present day pseudo three dimensional exposure of the thebes formation in a large fault block formed during the opening of the gulf of suez allowed for lateral and down dip measurement of slope and basinal facies in the field and from photos remobilized facies were digitized in the photos and evaluated using image analysis software a technique with a wide range of applications to outcrop studies of sedimentary architecture debris flow deposits in the lower section of the thebes formation comprises clasts with differing fossil assemblages a relative sea level rise at the start of upper thebes formation deposition resulted in basinal sediments comprising periodic incursions of high density turbidite grainstones encased within a background of planktonic foraminiferal wackestones foraminiferal assemblages of remobilized facies imply multiple sources on the carbonate platform demonstrating the effect of short lived tectonism on slope instability and deposition of mass transport deposits the results of the study confirm that tectonism associated with the syrian arc fold belt which altered the style of basin sedimentation between egypt and syria persisted into the eocene at least as far south as wadi araba in the western desert and hammam faraun in sinai in addition the shape size and extent of the two dominant remobilized facies debris flows and grainstone turbidites are influenced by their mud rich versus grainy compositions

environmental control on granular clinoforms of ancient carbonate shelves the purpose of this paper is to document the influence of depositional environments on shallow water low relief clinoforms from the description of five ancient carbonate platforms the neoproterozoic namibia middle jurassic france lower cretaceous france upper cretaceous oman and miocene turkey these examples have been investigated on the basis of field observations the clinoforms are described with reference to geometric and compositional attributes declivity shape height sedimentary structures sediment fabric and components the results show great variability in stratal geometry declivity and facies distribution 1 depositional profiles vary from exponential to sigmoidal to oblique 2 maximal slope angles range from 3 to 25 most of them being grouped between 10 and 18 3 facies differentiation identified from lateral facies successions along beds and vertical facies successions through beds is pronounced to subtle this study documents linkages between depositional environments and clinoform attributes proximal shallow clinoforms display round edged exponential profiles sediment deposition has resulted from unidirectional currents in the upper convex section and storm generated oscillatory currents in the lower concave part the sediment fabric changes gradually along this type of clinoform there is little vertical facies differentiation through these clinobeds which have formed from a continuous amalgamation of deposits by contrast distal clinoforms shelf break distally steepened ramp settings yield a much broader spectrum of profiles and are generally shorter and steeper sedimentary structures in gravel sized deposits of the upper slope indicate pure traction by unidirectional currents conversely marks of oscillatory flows undular wavy top bounding surfaces of clinobeds are common in the lower slope intercalation of massive fine grained deposits suggests offshore transport of carbonate mud by suspension each distal clinobed represents a single flow event accordingly facies differentiation is weak laterally but may be pronounced through the clinobeds our study suggests that low relief forms of proximal shallow environments which contain coarse grained and photo independently produced debris record hydrodynamic equilibrium profiles whereas the higher relief forms of this setting rather reflect a high differential production rate of carbonate sediment with water depth the carbonate sediment of the distal clinobeds mainly derives from skeletal production by oligophotic and photo independent biota of the middle shelf ramp and upper portion of the clinoforms the contribution by in situ skeletal biota only becomes significant on the lower slope indicating that the distal submerged slopes of carbonate platforms are not organically but hydrodynamically generated our compilation shows that the slope angles of shallow marine low relief clinoforms do not simply correlate to the sediment grain size and fabric in contrast to what has been documented for the high linear slope profiles this difference stems from the depositional settings namely the involved transport mechanisms low relief clinoform accretion seems to be dominantly influenced by wave induced sediment transport in contrast to linear flanks of high relief clinoforms that build to the angle of repose and for which gravity is the primary transport process

seismic architecture of a lower cretaceous platform to slope system santa agueda and poza rica fields mexico two three dimensional seismic data sets over the albian western golden lane margin and time equivalent basinal deposits of poza rica field allowed us to investigate the linked architecture of a steep sided carbonate platform el abra formation and a thick accumulation of redeposited carbonate sediment at the toe of the slope and in the basinal area tamabra formation regional seismic cross sections show that the most aggrading albian platform has an eroded platform top a scalloped margin and a channelized slope that are equivalent to a 20 km 12 4 mi wide westward thinning thick toe of slope apron made of chaotic contorted mounded moderate to high amplitude reflections detailed reflection geometries in the albian toe of slope and basinal deposits consist of chaotic to short discontinuous low amplitude reflection at the toe of the slope of the golden lane platform laterally changing to a discontinuous mounded shingling reflection which ultimately turns into high amplitude parallel reflections we interpret this lateral change to reflect the seismic signature of the change from the block and debris flow dominated toe of slope area to debris flow and concentrated density flow deposits in the basin that ultimately grade laterally into pelagic deposits on a flattened seismic slice mounded reflections correspond to lobate to fan shaped seismic events several kilometers wide that are interpreted as a carbonate basin floor fan comparison between core and seismic data shows a dominance of debris flows in the lower two albian sequences albian 1 and albian 2 that grade vertically into more lobate concentrated density flows and turbidites in the upper two albian sequences albian 3 and albian 4 seismic data used in this study combined with core observations do not support the interpretation of the albian tamabra formation being of shallow water origin seismic features identified as basin floor fan channel and debris flow deposits have a shape and size that are similar to those of other redeposited basinal carbonate deposits elsewhere the seismic architecture shows that the poza rica field is a typical example of thick accumulation of grainy porous carbonate deposits in a basinal setting this example shows the potential of a large hydrocarbon accumulation in a tectonically modified stratigraphic trap around shallow water carbonate platforms

quantitative compositional analysis of a triassic carbonate platform southern alps italy abstract we have estimated abundance and distribution of automicrite marine cements and skeletal grains in the triassic sella massif an isolated platform flanked by steep 25 35 clinoforms 108 samples were taken at constant intervals from measured sections of the major zones of the platform edifice the platform top margin upper slope and lower slope in a first step carried out in the field and on hand specimen purely detrital deposits were separated from automicrite facies i e beds with automicrite cement filled primary vugs and admixtures of skeletal carbonate and lithoclasts in the second step samples with automicrite facies were thin sectioned and point counted the categories used for point counting were a automicrite b vugs and cement c microspar or neomorphic spar d skeletal grains and e internal sediments at the platform top 46 of samples are pure detrital deposits 27 consist of automicrite facies and 27 are too strongly altered by dolomitization to allow classification at the margin upper slope 68 of samples consist of automicrite facies 22 are pure detrital sediments and 10 are strongly altered at the lower slope 63 are detrital deposits 10 automicrite facies and 27 are extensively dolomitized the most important contributors to the automicrite facies are automicrite 41 on the platform top 29 on the margin upper slope 28 on the lower slope and early marine cement 35 on the platform top 48 on the margin upper slope 27 on the lower slope the amount of skeletal grains is less than 10 the automicrite facies stabilized the platform margin and upper slope automicrite abundant early marine cements and micro organisms such as tubiphytes formed a rigid framework thus substituting for the lack of a metazoan reef on the upper slopes the framework of automicrite facies stabilized the slope but intermittently the automicrite layers are frequently dissected by sediment filled fractures or are broken into clasts we assume that they slid on the layers of loose detritus bigger slides turned into rubbly debris flows that formed metre thick breccias at the lower slope and the proximal basin floor the planar shape and steep angle of the clinoforms indicate that the large scale geometry of the slope was not controlled by the automicrite but rather by non cohesive layers of sand and rubble piled up to the angle of repose the production mode of the sella is comparable of that of a mud mound factory this factory was highly productive in 1 ma the platform aggraded over 300 m and prograded over 2000 m in all directions

triassic latemar cycle tops subaerial exposure of platform carbonates under tropical arid climate the triassic latemar platform in the dolomites italy is the site of several ongoing controversies perhaps the most interesting debate focuses on apparent cyclic deposition within the latemar platform whose nature and duration are still open to debate further disagreement concerns the lack of meteoric diagenesis related isotope shifts at cycle tops that bear circumstantial petrographic evidence for subaerial emergence here an evaluation of the nature of latemar cycle tops is presented combining evidence from previous work and new field petrographic and geochemical data cycle tops are ranked according to increasing exposure duration and spatial extent type i surfaces lacking unequivocal evidence of prolonged supratidal conditions type ii dolomite caps formed in warm evaporitic intertidal lagoonal waters followed by exposure of perhaps intermediate duration type iii clastic rich red calcareous horizons with some showing platform wide extent representing prolonged supratidal conditions and type iv discontinuities in tepee belts genetically related to type ii and iii surfaces but likely representing shorter lived exposure stages petrographic and geochemical criteria indicate that most diagenesis occurred in the shallow marine and burial domain whilst an extensive meteoric overprint of cycle tops is lacking this is underlined by the scarcity of meteoric diagenetic fabrics such as gravitational cements that where present are here interpreted as marine vadose in origin the scarcity of carbon and oxygen isotope signatures commonly assigned to subaerial exposure stages is best explained in the context of mid triassic climate the low latitude tropical but arid setting of the latemar situated in the western extension of the tethys ocean its isolation from nearby continental areas and overall short term emergence episodes are in agreement with a limited degree of meteoric alteration of most cycle tops high amounts of aeolian clastic material beneath some cycle tops along with high fe and mn elemental abundances argue for intermittent subaerial conditions this study proposes an enhancement of the classical allan and matthews 1982 isotope model for subaerial exposure under strongly arid climates as the subaerial exposure nature of latemar cycle tops and therefore eustasy as the cause for cyclicity have been previously challenged due to the lack of meteoric induced isotopic signatures the outcome of this study is of significance for the ongoing latemar stratigraphic controversy

the 1975 1977 crisis of la soufriere de guadeloupe f w i a still born magmatic eruption on july 8 1976 eruptive activity broke out at la soufriere de guadeloupe f w i after about one year of increasing seismic activity seismic activity continued to increase until august 1976 reaching more than 1500 events a 200 fold increase over the preceding quiet period of a few years and an energy output of about 1017 ergs in a day a total of 26 major phreatic eruptions similar to the july 8 outburst took place during an eight months period the steam blasts that characterized the eruptions gave rise to particle and sometimes block charged plumes that deposited an estimated 106 m3 of solids the h2o rich gases emitted during the blasts presumably contained other gases h2s so2 co2 that were partly adsorbed on solid particles all material was erupted at temperatures of the order of 100 to 200 c the observation of vertical migration of earthquake foci in less than a few hours and over about 6 km depth and of abnormal variations of the geomagnetic field indicate a deep energy source for the phreatic eruptions a small proportion of the gases adsorbed on solid particles had a magmatic origin however most of the steam and the tephra seemed to originate from superficial levels of a hydrothermal system similar phreatic eruptions have occurred several times in recorded history in the case of la soufriere the origin of the phreatic eruptions is best described by an abnormal energy input versus steady state from a crustal magma chamber the occurrence of truly magmatic eruptions is presumably inhibited by an extensive hydrothermal system the abrupt release of more power from the magma chamber could have resulted in an explosive pyroclastic eruption substantial improvement of the guadeloupe volcano observatory has followed the 1975 1977 crisis permanent telemetered geophysical networks and regular geochemical observations have provided a five year data base of the volcano behavior in its noneruptive state which can be compared to crisis situations

spatial geochemistry of a carboniferous platform margin to basin transect balancing environmental and diagenetic factors abstract conventional one dimensional chemostratigraphy of marine carbonates assesses the chemical archive of individual stratigraphic sections and their correlation in space and time whereas this approach has shown to be of value when linking isobathymetric domains usually characterised by similar facies more caution is needed when correlations are extended across different physiographic settings and hence different facies belts here the spatial geochemical record of pennsylvanian platform margin to basin transects across a bathymetric range of about 800 m is documented and discussed in a process oriented context particularly the presence of layered palaeo water masses and their potential control on slope facies distribution and geochemical properties requires attention whereas carboniferous thermo and or chemo clines most likely affected depth related slope facies zonation it was facies change and hence variances in porosity permeability properties that controlled differential early burial diagenetic alteration specifically the lower slope related breccia facies is characterised by higher volumes of early burial carbonate cements this implies that these sediments entered the shallow burial domain with a considerable open pore space and gave way to an increased rock fluid ratio whereas the 13 c record is invariant with bathymetry the more diagenesis sensitive 18 o proxy records pronounced shifts observed across major facies boundaries from this it is concluded that although the primary controlling factor of slope facies distribution with depth is probably palaeoceanographic in nature it is differential rock fluid ratios that control the first order spatial shifts in 18 o composition these findings show that one dimensional chemostratigraphy will severely underestimate the complexity of three dimensional bathymetric data sets across platform margins this is of relevance for the interpretation of the geochemical archive of fossil carbonate platforms in general

chemical characteristics of the crater lakes of popocatetetl el chichon and nevado de toluca volcanoes mexico abstract three crater lakes from mexican volcanoes were sampled and analyzed at various dates to determine their chemical characteristics strong differences were observed in the chemistry among the three lakes nevado de toluca considered as dormant el chichon at a post eruptive stage and popocatepetl at a pre eruptive stage not surprisingly no influence of volcanic activity was found at the nevado de toluca volcano while the other volcanoes showed a correlation between the changing level of activity and the evolution of chemical trends low phs so 4 2 and f decreased irregularly at el chichon from 1983 until 1997 major cations concentrations also diminished at el chichon a 100 increase in the so 4 2 content was measured at popocatepetl between 1985 and 1994 an increase in the mg cl ratio between 1992 mg cl 0 085 and 1994 mg cl 0 177 was observed at popocatepetl before the disappearance of the crater lake in 1994 it is concluded that chemical analysis of crater lakes may provide a useful additional tool for active volcano monitoring

growth mode of middle triassic carbonate platforms in the western dolomites southern alps italy abstract the correlation of carbonate platform and slope sediments with biostratigraphically and radiometrically dated basinal successions in the western dolomites allows the reconstruction of the growth of a middle triassic carbonate platform schlern rosengarten over a time interval of approximately five ammonoid zones reitzi secedensis curionii gredleri archelaus zones the whole platform evolution had a total duration of

a gigantic bezymianny type event at the beginning of modern volcan popocatepetl the history of volcan popocatepetl can be divided into two main periods the formation of a large primitive volcano approximatively 30 km wide on which is superimposed a modern cone 6 8 km in diameter and 1700m high a major event of bezymianny type marks the transition between these two dissimilar periods the activity of the primitive volcano was essentially effusive and lasted several hundred thousands of years the total volume of products ejected by the volcano is of the order of 500 600 km3 its last differentiated magmas are dacitic a gigantic debris flow d f spread on the southern side is related to the bezymianny type event which destroyed the summit area of the ancient edifice an elliptical caldera 6 5 11 km wide was formed by the landslide its deposits with a typical hummocky surface cover 300 km2 for a volume of 28 30 km3 numerous outcrops belonging to this debris flow show slabs of more or less fractured and dislocated rocks that come from the primitive volcano these deposits are compared to two studied debris flows of similar extent and volume the mount shasta and colima s d f this eruption takes a major place in the volcanologic and magmatic history of popocatepetl pyroclastic products of surge type with laminites and crude layers ashflows and pumiceous airfall layers are directly related to this event and begin the history of the modern volcano probably less than 50 000 years ago in addition a second andesitic and dacitic phase rose both from the central vent forming the basis of modern popo and from lateral vents the terminal cone is characterized by long periods of construction by lava flows alternating with phases of destruction the duration of these episodes being 1000 to 2000 years the cone is composed of two edifices the first volcan el fraile began with effusive activity and was partly destroyed by three periods of intense explosive activity the first period occurred prior to 10 000 years b p the second from 10 000 to 8000 years b p and the third from 5000 to 3800 years b p each period of destruction shows cycles producing collapsing pyroclastic flows or nuees of the st vincent type related to the opening of large craters plinian air fall deposits and minor lava flows the second edifice the summit popo produced lava flows until 1200 years b p and since that time entered into an explosive period two cataclysmic episodes each including major pyroclastic eruptions occurred 1200 and 900 1000 years ago during the pre hispanic and historic times effusive activity was restricted entirely to the summit area alternating with plinian eruptions nevertheless despite the quiet appearance of the volcano the last period of pyroclastic activity which started 1200 years ago may not have ended and can be very dangerous for the nearby populations

forward modelling of carbonate platforms sedimentological and diagenetic constraints from an application to a flat topped greenhouse platform triassic southern alps italy abstract quantitative analysis of depositional systems using numerical models can provide insights into the interaction of sedimentological and diagenetic processes difficult to interpret from observation of the geological products alone numerical models can highlight the interactions between controlling parameters and generate best estimate simulations of case studies from the geological record different data sources e g outcrop data uniformitarian constraints paleogeography need to be considered in the process of defining the parameters required to produce models that honour individual case studies we present a best estimate forward model of a high relief triassic carbonate platform southern alps italy generated using carb3d a 3d process based forward modelling package able to simulate sedimentary facies geometries and early diagenesis of isolated carbonate platforms the parameters used for the presented forward model have been deduced by the study of architectural sedimentological and diagenetic features of the platform and by data from modern and ancient analogues sensitivity analysis is used to tune values of the parameters within ranges defined from field laboratory and uniformitarian constraints critical evaluation of the model allowed 1 verification of the validity of the used parameters 2 evaluation of the interaction between controlling parameters 3 development of a numerical model that can be used for quantitative elaborations furthermore the process of generating the numerical model required a detailed interpretation of field and laboratory data crucial to define the required input parameters modelling the studied carbonate platform also enabled evaluation of the effects of the interaction between productivity environmental energy and creation of accommodation space promoting the understanding of their role on the architecture of carbonate systems forward modelling also allows the integration of data from conventional data sets with data from present day observations and seismic geometries promoting a transition from a qualitative to a semi quantitative quantitative sedimentological approach forward models can further be used to parameterise petrophysical properties of complex geobodies with potential application for the management of georesources

quantification of input and compositional variations of calciturbidites in a middle triassic basinal succession seceda dolomites southern alps triassic calciturbidites were studied in a 100 m long core and nearby outcrops of the basinal buchenstein formation to determine composition and thickness variations the quantity of recognized turbidite sediment relative to background sediment changes from 15 by volume in the lower part to 60 in the upper part reflecting the steady progradation of nearby platforms the composition of the sand fraction of 214 turbidites was point counted in thin sections micrite peloids average 23 and lithoclasts 16 are by far the most dominant constituents they are interpreted as two different varieties of in situ precipitated micrite automicrite which probably formed under the influence of microbes and constitute the principal building material of the adjacent platforms platform derived skeletal grains amount to only 0 5 variations in turbidite composition were quantified using spearman s rank correlation and cluster analysis the most significant compositional variations seem to be related to hydrodynamic sorting in the turbidity currents and to the gradual shift from distal to more proximal turbidites in the core as the platforms prograded basinward cluster analysis of the 214 samples shows a major subdivision into micrite and sparite dominated turbidites clusters associated with micrite dominated turbidites are enriched in radiolaria and thin shelled bivalves whereas the clusters related to sparite dominated turbidites show an abundance of lithoclasts this subdivision seems strongly related to sorting effects in a turbidity current point counting of turbidites in nearby outcrops revealed a lateral variation in composition proximal turbidites are sparite dominated and enriched in lithoclasts distal portions are chiefly micrite with an open ocean biota thin shelled bivalves radiolaria this differentiation resembles the vertical change in composition of thick turbidite beds and is attributed to different settling rates of the various grains in the turbidity current there is no indication that turbidite composition fluctuated significantly under the influence of sea level fluctuations this is not surprising because the dominant automicrite facies of the platforms only migrates laterally but does not change much during sea level cycles

facies geometry and growth phases of the valdorria carbonate platform pennsylvanian northern spain the 14 km wide valdorria outcrop pennsylvanian northern spain is one of the few examples of entirely exposed flat topped and high relief carbonate platforms reported in the fossil rock record laterally and vertically traceable stratal patterns expose three phases of growth phase i is a 430 m thick platform to slope succession that prograded over 6 km and is dated as early bashkirian akavasian askynbashian phase ii aggraded and prograded exhibiting 180 m thickness of cyclical platform top deposits dated as late bashkirian asatauian phase iii is a mound shape structure that developed over the platform top of phase ii as a new phase of platform nucleation it is 535 m thick and 2 km wide and dated as late bashkirian asatauian transition interval the observed changes of growth styles during platform evolution from a prograding to an aggrading prograding system and a rapid aggradational phase are inferred to be controlled by flexural subsidence in the active cantabrian foreland basin at the variscan orogenic front the metre scale shallowing upward cycles of the platform top are most probably due to glacioeustasy as evidenced by well recorded subaerial exposure surfaces superimposed on subtidal deposits and by a stratal pattern recurrent in a short interval of about 160 kyr observations of outcropping bashkirian cyclothems in an isolated carbonate system devoid of siliciclastic input are relevant for a better understanding of the impact of high frequency sea level fluctuations on the carbonate factory moreover progradation of the platform margin during phase i reaches a rate of 2500 m myr and 1810 m myr during phase ii rates that are high when compared to other pennsylvanian examples the aggradation rate of 447 m myr calculated for late bashkirian transition interval phases i and ii uncorrected for compaction missing beats and erosion is uncommonly high in comparison to coeval pennsylvanian examples the platform exhibits a self nourishing prograding microbial boundstone dominated slope thus the slope shedding model applies well to valdorria however phase ii recorded eustatic variations able to inhibit the slope microbial boundstone factory during low sea level stands this is marked by common slope red stained breccias synchronous to platform top subaerial exposure phases contrarily periods of relative high sea level and rapid subsidence in phase iii registered a greater development of cemented microbial boundstone these observed partly opposing relationships of sea level stands shedding modes and slope architecture provide an improvement of the currently used slope shedding model the overall architecture of the valdorria outcrop compares well with that of other contemporaneous platforms such as sierra del cuera and bolshoi karatau valdorria shares the high relief and flat topped steep slopes cyclothemic patterns and occurrence of karst features with the pricaspian basin platforms tengiz karachaganak and kashagan with minor variations in facies distribution of the internal platform furthermore the continuous seismic scale outcrop of valdorria together with its isolated setting and asymmetrical growth makes it an additional good candidate for potential subsurface analogues of hydrocarbon bearing systems

thermal parameters of the oceanic lithosphere estimated from geoid height data geoid height anomalies derived from seasat altimeter data have been analyzed across fracture zones and over ocean ridges in two limited regions of the south pacific eltanin fracture zone system east pacific rise and southeast indian ocean observed geoid height age and geoid height derivative with respect to age age relationships have been established comparison with theoretical relationships computed for the plate model of lithospheric cooling permits an estimation of the thermal parameters entering into the model two quantities can be derived the product tm thermal diffusivity volume coefficient of thermal expansion tm bottom boundary temperature and the thickness h of the plate the best fitting values for the south pacific and the southeast indian ocean are tm 0 52 10 3 cm2 s 1 and h in the range 50 70 km for ages less than 30 m y whereas for larger ages 30 m y geoid observations are better explained by a larger h value in the range 70 90 km the depth age relationship observed in the south pacific region is consistent with these parameters on the other hand data for the northeast pacific argue rather for a lithospheric thickness larger than 100 km this suggests that local and regional variations exist in the thermal properties of the oceanic lithosphere

forecasting large explosions at bezymianny volcano using thermal satellite data large volcanic explosions pose a severe risk to life and cargo by injecting ash into local and international air traffic routes prior to exploding bezymianny kamchatka commonly shows an increase in lava extrusion rate which can be detected by satellites as an increase in thermal radiance here we present the first method of forecasting explosive eruptions based solely on satellite data a pattern recognition algorithm using advanced very high resolution radiometer avhrr data has been developed based on known precursory trends of increasing radiance prior to 19 explosions at bezymianny volcano in 1993 2008 the algorithm retrospectively forecasts 89 of the explosions 100 of the explosions that show precursory increases in thermal radiance with 71 of alerts issued in the 30 days beforehand the method also provides the probability of an explosion occurring within a given number of days after an alert is triggered by the algorithm when applied to independent data the algorithm correctly provided alerts before the 16 december 2009 31 may 2010 and 13 april 2011 explosions

analysis of temporal and spatial heterogeneity of magnitude frequency distribution inferred from earthquake catalogues summary statistical models are introduced for the simultaneous estimation of the changes of the b value and detection rate of earthquakes in a catalogue which develops in time or varies in space the three characteristic parameters including b for the magnitude frequency distribution of detected earthquakes are represented by respective three b spline functions of time or location in a space an objective bayesian method is adopted for the optimal estimate of such functions with many unknown coefficients the present procedure is applied to earthquake catalogues for japanese seismic activity

temporal and three dimensional spatial analyses of the frequency magnitude distribution near long valley caldera california summary the 3 d distribution of the b value of the frequency magnitude distribution is analysed in the seismically active parts of the crust near long valley caldera california the seismicity is sampled in spherical volumes containing n 150 earthquakes and centred at nodes of a grid separated by 0 3 km significant variations in the b value are detected with b ranging from b 0 6 to b 2 0 high b value volumes are located near the resurgent dome and at depths below 5 km at mammoth mountain b values are found to be much lower south of the long valley caldera we interpret this to indicate that an active magma body has advanced from depths below 8 km to depths of 4 to 5 km beneath mammoth mountain in 1989 and that anomalous crust either highly fractured or containing unusually high pore pressure such as is the case in the vicinity of active magma bodies exists north of the seismically active area beneath the resurgent dome at all depths we also investigate the spatial distribution of temporal variations of the frequency magnitude distribution by introducing diverential b value maps b values increased from b 0 8 to b 1 5 underneath mammoth mountain at the onset of the 1989 earthquake swarm and remained high thereafter this suggests that an intrusion permanently altered the average distribution of cracks at 5 10 km depth or that the pore pressure permanently increased we propose that high b values are a necessary but not suycient condition near a magmatic body and therefore spatial b value mapping can be used to aid in the identification of active magma bodies

variations in the frequency magnitude distribution with depth in two volcanic areas mount st helens washington and mt spurr alaska the frequency magnitude distribution of earthquakes characterized using the b value is examined as a function of space beneath mount st helens 1988 1996 and mt spurr 1991 1995 at mount st helens two volumes of anomalously high b b 1 3 can be observed at depths of 2 6 3 6 km below the crater floor and below 6 4 km these anomalies coincide with 1 the depth of vesiculation of ascending magma and 2 the suggested location of a magma chamber at mount st helens study of mt spurr reveals an area of high b value b 1 3 at a depth of about 2 3 4 5 km below the crater floor of the active vent crater peak we propose that the higher material heterogeneity in the vicinity of a magma chamber or conduit due to vesiculation of the ascending magma is the main cause of the increased b value at shallow depths alternatively interaction of magma with groundwater may have increased pore pressure and lowered the effective stress the deeper anomaly at mount st helens is likely caused by high thermal stress gradients in the vicinity of the magma chamber our results indicate that detailed mapping of the frequency magnitude distribution can be used as a tool to trace vesiculation and locate active magma chambers

controls on facies architecture of a large triassic carbonate platform the great bank of guizhou nanpanjiang basin south china abstract the great bank of guizhou gbg is an exceptionally well exposed isolated triassic platform in the nanpanjiang basin of south china the platform is exhumed with its depositional profile preserved and is dissected by a faulted syncline that exposes a complete and uncomplicated cross section providing a unique opportunity to evaluate mechanisms involved in its birth evolution and demise the gbg formed near the southern margin of the yangtze platform during a deepening event that expanded the nanpanjiang basin and drowned the region surrounding the gbg in the latest permian initial accumulation of the gbg began in the latest permian with small reef mounds and open marine skeletal packstones following the end permian extinction cyanobacterial boundstones grew over the bank top during the early triassic the gbg developed a low relief bank profile with mobile oolite shoals at the margin shallow subtidal and peritidal deposits in the interior and gentle slopes dominated by pelagics debris flow deposits and turbidites at the basin margin in the middle triassic anisian the gbg developed a progressively steepening profile rimmed with massive tubiphytes reefs the platform was flat topped with tidal flat deposits across the interior basin margin deposition was dominated by turbidites and debris flow deposits but eventually shifted to avalanche and rock fall deposits as the slopes steepened to the angle of repose in the middle triassic ladinian an erosional escarpment up to 1700 m high developed at the margin platform margin strata are bedded packstones similar to interior strata whereas breccias at the basin margin contain coral boundstone clasts suggesting erosion of reefs from the escarpment a restricted subtidal lagoon formed in the interior producing an atoll like morphology later a flat topped profile was restored as tidal flats spread across the interior in the beginning of the late triassic deepening contributed to termination of the gbg before siliciclastic turbidites and shales were deposited over the platform in contrast with the well known platforms of the dolomites of northern italy the gbg contains abundant muddy carbonates and a progressively steepening bank to reef rimmed and escarpment architecture the italian platforms contain little mud and have angle of repose pinnacle geometries the gbg s larger size increased mud production and protected it from extensive winnowing of mud which in turn resulted in off bank shedding of muddy sediments that were stable on relatively gentle basin margin slopes which progressively steepened and ultimately led to avalanche deposits and a high relief erosional escarpment in contrast the lesser mud content of the dolomites platforms forced avalanche and talus deposition to dominate throughout deposition of basin margins which in turn produced their angle of repose geometries

compositional variations during phases of progradation and retrogradation of a triassic carbonate platform picco di vallandro durrenstein dolomites italy in this paper data are presented on the composition of sediments deposited at the toe of slope during progradation or retreat of triassic carbonate platforms in the dolomites italy for this purpose a succession was studied from the toe of slope of a triassic carnian carbonate platform picco di vallendro durrenstein dolomites italy the microfacies analysis of selected calciturbidites sequences revealed a reduced input of oncolites and ooids during progradation and an increase in clasts the main input however was derived from the reefs on the platform retrogradation of the platform showed an increase of filaments and radiolarians open ocean biota as well as carbonate mud and a reduced input of grains that originated within the reefs on the platform both during progradation and retrogradation parts of the platform were flooded and could produce excess sediment that could be exported to the surrounding basins however the absence of platform interior biota documents that progradation occurred from sediments of the reefal belt probably during relative sea level lowstands carbonate composition varies systematically with toe of slope progradation retrogradation and thus argues for carbonate production as the main driver of the geometries observed at the toe of slope

a pennsylvanian microbial boundstone dominated carbonate shelf in a distal foreland margin picos de europa province nw spain abstract a pennsylvanian bashkirian moscovian high rising microbial boundstone dominated carbonate platform 12 000 km2 developed in the external margin of a variscan foreland basin intensely studied in the northern domain cuera area the stratigraphy and sedimentology of the southern domain the picos de europa province is here revisited distribution of the bashkirian facies valdeteja formation defines a ramp low angle platform with an internal zone central and eastern sectors of the picos de europa province consisting of huge amounts of massive cement rich microbial boundstones surrounded by an external zone comprising lower slope boundstone derived breccias and basinal lime mudstones from the bashkirian moscovian transition to the early kasimovian picos de europa formation the carbonate platform moderately aggraded acquiring a high rising and flat topped geometry and then prograded rapidly into the external zone where platform derived carbonate sediment and clay sourced from the orogen were deposited seismic scale exposures of the western margin of the shelf show angular bedding relationship between basin toe of slope slope and platform top stratal domains with slope inclination up to 32 and a topographic relief of 550 m the platform evolution above described for the picos de europa province significantly differs with respect to the cuera area where platform mostly prograded during the bashkirian and subsequently aggraded during early moscovian the evolutionary differences between these two carbonate domains which are geographically close are interpreted as changes in tectonic subsidence distribution acting as the major factor controlling the large scale platform geometries in the active foreland basin context finally the tectonic overload due to the emplacement of the cuera thrust sheets during the moscovian kasimovian transition changed the platform growth style from progradational to aggradational and consequently the stacking pattern of the platform top cycles in the picos de europa province

facies architecture of an early jurassic carbonate platform slope jbel bou dahar high atlas morocco the plateau of jbel bou dahar high atlas morocco represents an outstanding example of a well preserved early mesozoic carbonate platform field observations of the large scale sedimentary structures and the arrangement of lithofacies associations within the mid and lower slope were combined with detailed microfacies analyses and gamma ray measurements the investigations were carried out in order to 1 resolve the sequence stratigraphic architecture of the slope and 2 reconstruct the sediment export patterns and depositional processes related to high frequency sea level variations the slope strata are arranged into two different types of lithofacies associations that are bounded by characteristic discontinuities and show a specific occurrence along the investigated slope section the steep 8 18 mid slope is dominated by thick to medium bedded limestone successions that were able to maintain a high angle of repose due to their detrital composition the sediment packages are bounded by basal low angle unconformities and wedge out within the lower slope or thin into the adjacent basin as single carbonate layers the sediments are characterized by coarse grained and poorly sorted floatstones to rudstones which show low gamma ray values and contain components derived mainly from the platform edge the facies associations were interpreted as debris flow deposits that were exported during sea level lowstands when the flattened platform top and extended parts of the margin were exposed and sediment production was restricted mainly to the outer margin and upper slope section in contrast the gently dipping lower slope 4 18 is characterized by rhythmic limestone marl alternations that show increasing thicknesses with increasing distance from the platform from the lower part of the mid slope down the successions onlap the debris flow deposits forming a characteristic interfingering pattern of different lithofacies associations the medium to thin bedded carbonates of the limestone marl alternations comprise two different microfacies types 1 mudstones to wackestones with high gamma ray values and a mixed shallow marine to deep marine microfacies overlain by 2 well sorted arenitic packstones to grainstones with low gamma ray values and a shallow marine component composition the latter points to the platform interior and margin as primary source areas the shallow marine material was exported during sea level highstands when the carbonate factory included the entire platform margin and the flooded lagoons of the platform top during these periods the exported fine grained sediments could maintain only low angles of repose thus they bypassed the steep upper and mid slope sections developed into turbidites during downslope transport and were finally redeposited on the gently dipping lower slope and in the adjacent basin the architecture of the investigated slope area shows a characteristic interfingering of different facies associations that can be interpreted as genetic highstand and lowstand stratigraphic sequences the arrangement of these sequences along the slope as well as their composition were controlled by high frequency sea level fluctuations affecting the primary sediment production source area export patterns and sedimentary processes resulting in a shift of the depositional centers during different sea level stands

a process based model of pre eruption seismicity patterns and its use for eruption forecasting at dormant stratovolcanoes abstract using long term data sets the eruptive size timing and style can typically be successfully forecast for dormant volcanoes using current monitoring data and knowledge of precursory eruptive patterns the usaid usgs volcano disaster assistance program vdap utilizes seismic data over multiple eruption cycles and across volcano types to successfully forecast eruption size style and onset times as well as changes within ongoing eruptions from millions of seismic event observations we show that seismic data a proxy for rate dependent strain changes in the magmatic system combined with a process based conceptual geologic model enables eruption forecasting especially for stratovolcanoes dormant 20 years we show that this model often works for some open systems ones that sufficiently reseal to plug the conduit and also where a deep intrusion occurs after phreatic or phreatomagmatic explosions have begun this model is divided into four seismicity and geologic stages we describe each of the four stages of seismicity in detail and how they relate to the ongoing geologic process of that stage stage 1 deep intrusion and seismicity occurring at 10 to 40 km depth below the volcanic edifice stage 2 distal vt seismicity induced at distances from 2 to 30 km laterally from the summit by magma intruding into and inflating the upper crustal magma storage region stage 3 vent clearing seismicity associated with the initial vent creation and clearing phase of eruptive activity stage 4 repetitive event seismicity associated with the final ascent of magma from 2 km to the surface we present 36 examples of this seismic progression from 26 volcanoes we believe that this progression generally correlates with the magma flux and the eventual explosivity and is invaluable for forecasting eruptions

the ongoing dome emplacement and destruction cyclic process at popocatepetl volcano central mexico the ongoing eruptive activity of popocatepetl volcano has been characterized by emplacement and subsequent destruction of a succession of lava domes between the onset of the current eruption in 1994 and the time of this submission 38 episodes of lava dome formation and removal have been identified each dome has showed particular features related to the magma extrusion process among other manifestations dome emplacement events have been usually accompanied by relatively low intensity protracted explosions referred to as exhalations after variable times of residence emplacements have ended in partial or total destruction of the domes by strong vulcanian explosions that produced sizeable ash plumes with most of them also ejecting incandescent debris onto the volcano flanks here we present a detailed account for the observed activity related to the domes growth and destruction related seismic monitoring signals and morphological features of the domes based on 19 years of visual observations and image analysis we then discuss a model for the process of dome growth and destruction and its hazard implications

mapping active magma chambers by b values beneath the off ito volcano japan the b value of the frequency magnitude relation and thus the mean magnitude in the off ito volcanic area is not uniform based on detailed b value tomography using about 10 000 events in an area of 10 km radius and in the upper 15 km of the crust a high b value anomaly b 15 below 7 km depth and with a radius of about 2 km located below the coast southeast of ito contrasts with lower values of typically b 0 7 north of it and at shallower depths on the basis of surface deformations a tensile crack dislocation source was located above 7 km depth thus we surmise that the magma chamber in the off ito area was located below 7 km depth the correlation of a high b value anomaly with this model supports our hypothesis that active magma chambers may be mapped by high b value anomalies the magma body may be described as consisting of two parts a lower well established chamber below 11 km depth and a shallower part 11 7 km depth the b value in the volume surrounding the magma chamber increased from 0 7 during the 1980s to 1 5 during the earthquake swarms of the 1990s this may reflect a trend of increasing crack density due to the intrusion activity

minimum magnitude of completeness in earthquake catalogs examples from alaska the western united states and japan we mapped the minimum magnitude of complete reporting m c for alaska the western united states and for the junec earthquake catalog of japan mc was estimated based on its departure from the linear frequency magnitude relation of the 250 closest earthquakes to grid nodes spaced 10 km apart in all catalogs studied mc was strongly heterogeneous in offshore areas the mc was typically one unit of magnitude higher than onshore on land also mc can vary by one order of magnitude over distance less than 50 km we recommend that seismicity studies that depend on complete sets of small earthquakes should be limited to areas with similar mc or the minimum magnitude for the analysis has to be raised to the highest com mon value of mc we believe that the data quality as reflected by the mc level should be used to define the spatial extent of seismicity studies where mc plays a role the method we use calculates the goodness of fit between a power law fit to the data and the observed frequency magnitude distribution as a function of a lower cutoff of the magnitude data mc is defined as the magnitude at which 90 of the data can be modeled by a power law fit mc in the 1990s is approximately 1 2 0 4 in most parts of california 1 8 0 4 in most of alaska aleutians and panhandle excluded and at a higher level in the junec catalog for japan various sources such as ex plosions and earthquake families beneath volcanoes can lead to distributions that cannot be fit well by power laws for the hokkaido region we demonstrate how neglecting the spatial variability of m c can lead to erroneous assumptions about deviations from self similarity of earthquake scaling

nonlinear frequency magnitude relationships for the hokkaido corner japan abstract frequency magnitude relationships are determined for a source region defined by a circular epicentral area of 50 km radius centered on the carnegie broadband seismograph at kmu in the southeast corner of hokkaido island japan within this region bounded by a maximum depth of 125 km more than 11 100 earthquakes were detected and cataloged by the hokkaido university network during the period july 1976 through january 1987 the seismicity is divided into two effectively decoupled suites crustal eurasian plate and subduction pacific plate the frequency magnitude recurrence distributions exhibit departures from linearity which are statistically significant below m d 2 5 for the crustal data suite and m d 3 5 for the subduction data suite three independent tests show the nonlinearity is not caused by incompleteness the catalog is complete down to magnitude 2 0 or less for both data suites these observations are therefore inconsistent with the linear gutenberg richter relationship which is assumed to be valid over any magnitude range for which the data are complete there are relatively more large events and fewer small events in the subduction suite the logarithm of the ratio of the number of crustal events to the number of subduction events versus magnitude is monotonically decreasing and remarkably linear over the magnitude range 1 0 to 5 0 this suggests that the observed nonlinearity of these two frequency magnitude relationships has a common origin

precursory seismicity of the 1994 eruption of popocatepetl volcano central mexico popocatepetl volcano is located in the central mexican volcanic belt within a densely populated region inhabited by over 20 million people the eruptive history of this volcano indicates that it is capable of producing a wide range of eruptions including plinian events after nearly 70 years of quiescence popocatepetl reawakened in december 21 1994 the eruptive activity has continued up until the date of this submission and has been characterized by a succession of lava dome growth and destruction episodes similar to events that have apparently been typical for popocatepetl since the fourteenth century in this regime the episodes of effusive and moderately explosive activity alternate with long periods of almost total quiescence in this paper we analyze five years of volcano tectonic seismicity preceding the initial eruption of the current episode the evolution of the v t seismicity shows four distinct stages which we interpret in terms of the internal processes which precede an eruption after a long period of quiescence the thermal effects of a magma intrusion at depth the fracturing related to the slow development of magma related fluid pathways the concentration of stress causing a protracted acceleration of this process and a final relaxation or redistribution of the stress shortly before the initial eruption are reflected in the rates of v t seismic energy release a hindsight analysis of this activity shows that the acceleration of the seismicity in the third stage asymptotically forecast the time of the eruption the total seismic energy release needed to produce an eruption after a long period of quiescence is related to the volume of rock that must be fractured so imposing a characteristic threshold limit for polygenetic volcanoes limit that was reached by popocatepetl before the eruption

applications of a simplified equation of state for the density of silicate hydrous magmas the volcan de colima mexico buoyancy driven dome growth process similarities and differences with the popocatepetl volcano domes abstract colima and popocatepetl volcanoes began erupting during the second half of the twentieth century after periods or relatively long quiescence both eruptive episodes show similarities persistent dome growth and destruction episodes over periods of decades and differences higher rates of magma and gas production at popocatepetl with similar magmas popocatepetl s slightly more acidic we use a simplified equation of state eos for calculating the density of the hydrous andesitic magmas of volcan de colima in a realistic range of pressures temperatures and dissolved water content to model the density contrast with the host rock causing buoyancy of the magmatic column we use this model to explain some aspects of the dome forming effusive activity of colima and compare the results with a similar study made in a previous work on popocatepetl this dome height isostatic model explains well the observed mean heights around 50 m of the colima lava domes with the buoyant force resulting from a 2 5 wt h 2 o content in the melt a value consistent with recently published measurements of rock inclusions the slightly higher h 2 o contents required for the observed dome heights at popocatepetl is explained in terms of the different depths of the isostatic compensation levels the compositional differences between the magmas and the structural differences between the volcanic edifices

the latemar a middle triassic polygonal fault block platform controlled by synsedimentary tectonics abstract detailed field mapping of a middle triassic carbonate buildup the latemar in the western dolomites northern italy has been carried out the latemar is an isolated carbonate buildup that nucleates on a fault bounded structural high horst cut into the underlying late anisian carbonate bank of the contrin fm this study demonstrates that extensional synsedimentary tectonics is the main factor controlling its geometry and provides an age for this tectonic phase in an early phase slopes were mostly composed of well bedded clinostratified grainstones and rudstones in a later stage the deposition of grainstones was accompanied by the emplacement of clinostratified megabreccias the upper portion of slopes is a microbial boundstone with abundant tubiphytes and patches or lenses of grainstone boundstones may occasionally expand into the platform interior and downward to the base of the slope the depositional profile was that of a mounded platform the buildup is dissected by a dense framework of high angle fractures and faults and by magmatic and sedimentary dikes exhibiting two principal directions trending nnw sse and ene wsw faults trending wnw ese were also observed magmatic dikes are related to the emplacement of the nearby predazzo intrusion and are thus upper ladinian kinematic indicators of strike slip activity were observed on fault planes trending nne ssw and nnw sse that can be attributed to cenozoic alpine tectonics faults magmatic dikes and sedimentary dikes show systematic cross cutting relationships with strike slip faults cutting magmatic dikes and magmatic dikes cutting sedimentary neptunian dikes ene wsw and wnw ese faults are cut by all other structures and record the oldest tectonic activity in the region structural analysis attributes this tectonic phase to an extensional stress field with a direction of maximum extension oriented ca n s several lines of evidence including sealed faults and growth wedge geometries allow us to recognize this old tectonic phase as syndepositional and to date it to the latest anisian avisianum and crassus ammonoid biochronozones the horse shoe shape of the platform and its margins rectilinear for long tracts are explained by the existence of a network of extensional faults whose activity lasted for part of the growth of the platform the latemar is thus a polygonal fault block platform controlled by synsedimentary tectonics the resulting sedimentary architecture is that of a growth wedge deposited probably on the uplifted side of a submerged half graben continuous reactivation of faults at platform margins locally determined anomalous facies transitions with well layered platform interior directly in contact with the clinostratified slopes

volcano tectonic earthquakes a new tool for estimating intrusive volumes and forecasting eruptions abstract we present data on 136 high frequency earthquakes and swarms termed volcano tectonic vt seismicity which preceded 111 eruptions at 83 volcanoes plus data on vt swarms that preceded intrusions at 21 other volcanoes we find that vt seismicity is usually the earliest reported seismic precursor for eruptions at volcanoes that have been dormant for decades or more and precedes eruptions of all magma types from basaltic to rhyolitic and all explosivities from vei 0 to ultraplinian vei 6 at such previously long dormant volcanoes because large eruptions occur most commonly during resumption of activity at long dormant volcanoes vt seismicity is an important precursor for the earth s most dangerous eruptions vt seismicity precedes all explosive eruptions of vei 5 and most if not all vei 4 eruptions in our data set surprisingly we find that the vt seismicity originates at distal locations on tectonic fault structures at distances of one or two to tens of kilometers laterally from the site of the eventual eruption and rarely if ever starts beneath the eruption site itself the distal vt swarms generally occur at depths almost equal to the horizontal distance of the swarm from the summit out to about 15 km distance beyond which hypocenter depths level out we summarize several important characteristics of this distal vt seismicity including swarm like nature onset days to years prior to the beginning of magmatic eruptions peaking of activity at the time of the initial eruption whether phreatic or magmatic and large non double couple component to focal mechanisms most importantly we show that the intruded magma volume can be simply estimated from the cumulative seismic moment of the vt seismicity from log10 v 0 77 log moment 5 32 with volume v in cubic meters and seismic moment in newton meters because the cumulative seismic moment can be approximated from the size of just the few largest events and is quite insensitive to precise locations the intruded magma volume can be quickly and easily estimated with few short period seismic stations notable cases in which distal vt events preceded eruptions at long dormant volcanoes include nevado del ruiz 1984 1985 pinatubo 1991 unzen 1989 1995 soufriere hills 1995 shishaldin 1989 1999 tacana 1985 1986 pacaya 1980 1984 rabaul 1994 and cotopaxi 2001 additional cases are recognized at frequently active volcanoes including popocateptl 2001 2003 and mauna loa 1984 we present four case studies pinatubo soufriere hills unzen and tacana in which we demonstrate the above mentioned vt characteristics prior to eruptions using regional data recorded by neic we recognized in near real time that a huge distal vt swarm was occurring deduced that a proportionately huge magmatic intrusion was taking place beneath the long dormant sulu range new britain island papua new guinea that it was likely to lead to eruptive activity and warned rabaul volcano observatory days before a phreatic eruption occurred this confirms the value of this technique for eruption forecasting we also present a counter example where we deduced that a vt swarm at volcan cosiguina nicaragua indicated a small intrusion insufficient to reach the surface and erupt finally we discuss limitations of the method and propose a mechanism by which this distal vt seismicity is triggered by magmatic intrusion

accommodation sedimentation development and massive early marine cementation latemar vs concarena middle upper triassic southern alps abstract massive early marine cementation mec is a major diagenetic feature of some carbonate platforms the comparison of two triassic buildups of similar size and preservation but contrasting degree of mec latemar dolomites and concarena lombardic alps allows for the investigation of differential cementation on carbonate platforms the assessment of the response of platform cementation to changes in accommodation sedimentation led to the identification of fundamental boundary conditions for mec 1 the time interval available i e a low rate of creation in accommodation space and 2 low carbonate production other important factors are 3 margin topography e g walled reefs and 4 effective fluid flow e g wave energy open and connected cavities provided by rigid frameworks the latemar mainly aggrading and locally retrograding lacks mec due to a high a s ratio i e creation destruction of accommodation in time a d a d t vs changes in sediment supply in time s d s d t and a low relief of the reefal margin in contrast the concarena in the beginning slowly and later rapidly prograding indicates mec owing to a low a s ratio and a distinct topography of the reef particular features of the concarena are cement arrangements of lenticular shape and considerable size in the back reef domain up to 3 m in diameter and 2 m in height these arrangements consist of botryoids and isopachous crusts of radiaxial fibrous calcite cements they represent one of the main components of the platform margin at concarena cathodoluminescence analyses of cements from both platforms quantifies the influence of shallow and deep burial diagenesis and shows that the majority 60 90 of all cements are of early marine origin

growth and demise of late carboniferous carbonate platforms in the eastern cantabrian zone asturias northwestern spain abstract geometric relationships of seismic scale stratal patterns observed on aerial photographs of late carboniferous carbonate platforms in the cuera region in asturias northwestern spain allow the identification of two discrete stages of platform development with different styles of deposition the first phase represented by the bashkirian valdeteja formation is characterized by progradation of more than 10 km with steep clinoforms of up to 35 and slope heights up to 650 m during the second phase corresponding to the moscovian picos de europa formation the platform aggraded mainly vertically nearly 850 m both phases of platform growth were terminated by major relative sea level lowstands in conjunction with local filling of the adjacent basins by shales and mudstones that onlap the platform flanks calibration with outcrops suggests a subdivision into the following lithofacies directly related to the depositional profile 1 platform interior parallel well to thick bedded skeletal pack to grainstones 2 margin algal and sponge dominated bioherms with little internal structure 3 slope clinothems of medium to thick bedded margin derived breccia beds 4 toe of slope alternating grain and packstones with spiculites and 5 basin marly shales shales sandstones and calcareous mudstones relative sea level changes caused by regional tectonic movements are suggested to be responsible for the generation of the two platform phases sea level highstands triggered the nucleation and growth of the platforms whereas major sea level lowstands in combination with terrigenous infill of the basins terminated the platform growth in addition it is proposed that the termination of late carboniferous carbonate platforms is caused by the combined effect of a sea level fall subaerial exposure and erosion and finally a rapid transgression that drowned and polluted the platform with shales and mudstones local variations in the infilling of the basins controlled the variations in the style of progradation the subsidence rates for the vertically aggrading phase picos de europa formation were approximately twice that for the progradational phase valdeteja formation and may explain the aggradational versus progradational character

high broadband seismoacoustic signature of vulcanian explosions at popocatepetl volcano mexico author s matoza robin samuel arciniega ceballos a sanderson r w mendo perez g rosado fuentes a chouet b a

facies architecture of an isolated carbonate platform tracing the cycles of the latemar middle triassic northern italy the 720 m thick succession of the middle triassic latemar massif dolomites italy was used to reconstruct the lagoonal facies architecture of a small atoll like carbonate platform facies analysis of the lagoonal sediments yields a bathymetric interpretation of the lateral facies variations which reflect a syndepositional palaeorelief based on tracing of lagoonal flooding surfaces the metre scale shallowing upward cycles are interpreted to be of allocyclic origin short term sea level changes led to subaerial exposure of wide parts of the marginal zone resulting in the development of a tepee belt of varying width occasional emergence of the entire lagoon produced lagoon wide decimetre thick red exposure horizons the supratidal tepee belt in the backreef area represented the zone of maximum elevation which circumscribed the sub to peritidal lagoonal interior during most of the platform s development this tepee rim the subtidal reef and a sub to peritidal transition zone in between stabilized the platform margin the asymmetric width of facies belts within individual metre scale cycles was caused by redistribution processes that reflect palaeowinds and storm paths from the present day south and west the overall succession shows stratigraphic changes on a scale of tens of metres from a basal subtidal unit overlain by three tepee rich intervals separated by tepee poor units composed of subtidal to peritidal facies this stacking pattern reflects two third order sequences during the late anisian to early middle ladinian

generation of vulcanian activity and long period seismicity at volcan de colima mexico abstract during the current episode which commenced in 1998 activity at volcan de colima has been characterised by daily vulcanian events several effusive phases and a number of larger dome destroying explosions the upper edifice comprises of an intricate array of fractures and within this system variations in the magma ascent rate rheology and volatile contents complete a complexity which controls the style of activity subtle variations in one or more of these factors can trigger a transition a model is presented of the vulcanian explosion mechanism which is reflected in the associated seismicity first the breaching of an impermeable cap and the initial gas loss after the rupture low frequency signal followed by fragmentation high frequency signal in 2005 a series of larger vulcanian explosions associated with ascending magma represent the period of activity with the highest production rate in recent years pyroclastic flows were produced by column collapse with the absence of vesicularity amongst the products pointing to a deep source of gas driving the eruption the appearance of swarms of long period lp events associated with the explosions provided a great opportunity for analysis and an insight into the processes within the fracture system which control the eruptive style cross correlation of the lp waveforms produced a series of ten families which reappeared in subsequent swarms suggesting a consistent source brittle fracture associated with the enhanced stain rate found along the conduit margins is suggested as the source of this seismicity this is supported by a linear relationship between log event rate and relative amplitude of the events within each swarm an analysis of the temporal distribution of lp events revealed a variation in conditions between swarms for some swarms the conditions within the fracture system meant that a conflict between the processes associated with magma ascent was revealed whilst for others it was a situation of failure and backup which can be interpreted as the failing and activation of different fractures within the upper edifice

lithofacies and depositional processes on a high steep margined carboniferous bashkirian moscovian carbonate platform slope sierra del cuera nw spain the depositional slope of the sierra del cuera a carboniferous bashkirian moscovian high steep margined carbonate platform provides excellent cross sections of lithofacies zonations and associated stratal geometries the steep 30 40 and nearly planar upper slope is dominated by massive sheet like layers of microbial cement rich boundstone which alternate with intercalations of red stained bryozoan cementstone with crinoids and brachiopods the slightly gentler 20 26 and concave upward lower slope is characterized by clast supported resedimented deposits the upper slope extended from platform break to ca 300 m water depth whereas lower slope sediments were deposited in water depths up to 600 700 m at which level the slope beds flatten to a few degrees toe of slope and interfinger with spiculitic and argillaceous basinal sediments between 250 and 450 m water depth boundstones and breccias alternated in a transitional zone the lower slope sediments include clast supported breccias with radiaxial fibrous cement in interparticle space mud to clast supported breccias with red stained carbonate mud matrix and packstone to grainstone and rudstone beds most of the clasts comprise boundstone reworked from an upper slope setting and smaller grains are platform and slope derived a pervasive submarine cementation occurs along the upper two thirds of the flank and this stabilized the slope slope deposition is interpreted as follows during active boundstone accretion microbial boundstone layers slid off and formed breccia tongues extending from the lower upper slope down to the toe of slope rock falls and avalanches were generated whenever the shear strength of the substrate of loose or partly lithified sediment was exceeded upper slope boundstone accretion and shedding independent of the depth of light penetration controlled most of the depositional processes on the slope cement dominated intervals are considered to be related to early highstand and or flooding phases relative sea level fluctuations and or associated changes in the water conditions are believed to be responsible for intervals of low boundstone production or cement precipitation whether the in situ boundstone and breccia are preferentially related to lowstand or highstand periods is as yet unclear

the role of lithospheric phase transitions on seafloor flattening at old ages abstract uplift of old ocean seafloor relative to the familiar t 1 2 curve is generally presumed to be a consequence of an additional heat source at the base of the oceanic lithosphere several geodynamical mechanisms have been invoked to explain this behavior we have taken a petrological rather than geodynamical approach and considered whether the causes of the flattening can be found within the conductive portion of the lithosphere where viscous creep is insignificant accordingly self consistent calculations of the phase assemblages of several candidate mantle compositions have been performed subject to the constraint of experimentally determined calorimetric measurements we have found that in general for temperatures below around 800 c and pressures greater than 10 kbar the phase change from spinel peridotite to garnet peridotite has a significantly negative clapeyron slope which could cause some amount of uplift of old seafloor the transition for representative thermal profiles should be depressed from about 35 km at 40 ma to 45 km at 160 ma since spinel peridotite is of lower density the net effect is to raise the seafloor topography the extent of the uplift which depends primarily on the al 2 o 3 content of the peridotite and on the effective thermal diffusivity of the lithosphere should be on the order of 140 220 m

diversity and factors controlling widespread occurrence of syn rift ladinian microbialites in the western tethys triassic catalan basin ne spain abstract the fault block carbonate ramps of the ladinian middle triassic catalan basin hosted a wide variety of microbial deposits which formed during a syn rift stage stratigraphical and sedimentological analyses of these microbialites allow us to reconstruct two depositional models for such microbial deposits moreover new insights into the interplay between the intrinsic and extrinsic factors that controlled the widespread development of these microbialites are provided stromatolites ooidal muddy microbial laminites and thrombolites were analyzed on the basis of their geometry lamination and textural attributes these microbialites are distributed over two transgressive regressive sequences and coexisted during the fassanian early ladinian regressive stage later stromatolites and ooidal muddy microbial laminites developed during the longobardian late ladinian transgressive stage three types of lamina couplets reflect distinct accretion processes linked to water chemistry sediment supply and hydrodynamic conditions thrombolite textures were produced by accretionary binding and encrusting processes microbially mediated and pervasive cementation the widespread occurrence of microbial deposits is explained as a consequence of a biogeochemical cascade of events e g anoxic dysoxic seawater conditions volcanic activity upwelling of alkaline waters nutrient concentrations and microbial blooms which promoted favorable conditions for microbial growth in the tethys during the ladinian furthermore in the catalan basin syn rift fault induced subsidence and local water energy gradients exerted an essential role in the distribution of the three types of microbialites through space and time thrombolites were prone to grow in the hanging wall block of a half graben subtidal conditions whereas stromatolites and ooidal muddy microbial laminites flourished preferably in a foot wall block setting intertidal shallow subtidal conditions however the fact that thrombolites exhibit abundant botryoidal and isopachous fibrous marine cements corrosion and significant microbial evidence allow us to hypothesize about the relationship between thrombolite occurrence and hydrothermal fault controlled fluid circulation during the triassic rifting the two depositional models here proposed constitute a step forward the understanding of the platform to basin microbialite heterogeneity during the ladinian furthermore this work sheds new light on the mechanisms that likely promoted microbialite development during a period of major ecological restructuration and complex oceanographic conditions

the changing climate framework and depositional dynamics of triassic carbonate platforms from the dolomites abstract the triassic of the dolomites offers a valuable opportunity to investigate the relationships between climate fluctuations and the changing depositional dynamics of carbonate platforms the reconstruction of the large palaeoclimatic modification is based on the synthesis of multiple sedimentological palaeobotanical pedological and geochemical proxies the triassic climate fluctuations were generally fast in nature and were probably associated with a latitudinal shift of the monsoon belts during the triassic the dolomites were placed at an intertropical northern latitude of about 16 18 and were generally dominated by dry climate and elevated temperature at least five pulses toward moister climate are however documented dated to early olenekian middle anisian late ladinian middle carnian and late norian times within this variable climatic scenario the carbonate systems record a global evolutionary trend from late permian early triassic regional shelves rich in loose micrites and bio calcarenites to anisian ladinian synsedimentary cemented steep sided 35 40 high relief platforms and back to carnian low angle ramps moist transgressive episodes were surprisingly prone to the spreading of corals and other colonial reef organisms probably because of the reduced space competition by syndepositional cementation structures the permo triassic boundary extinction dramatically impacted on the calcified organism communities but the carbonate depositional architecture nevertheless stayed almost unaffected through the boundary the early triassic and earliest anisian were commonly associated with hyperhaline sometimes evaporitic conditions intervals of moister climate and efficient river discharge are however documented by earliest induan and early olenekian sediments the latter terrigenous deposits matched a crisis in the carbonate production after a return to arid conditions during the anisian a fluctuation toward moister climate developed associated to a massive continental vegetation cover the anisian tectonic activation of the region fragmented the previous carbonate shelf triggering the development of three generations of fast prograding but globally backstepping isolated platforms recording an increasing role of the synsedimentary cementation a dry climate dominated the late anisian and early ladinian interval at the time a fast subsidence pulse was associated with platform drowning and basinal anoxia only a few aggrading pinnacles were able to survive providing the nuclei for larger prograding platforms during a dry climate interval massive syndepositional cementation generated a major source of carbonate carbonate production stayed active through the ladinian magmatic phase but the onset of volcanism was associated with a large modification in the platform carbonate facies which became dominated by automicrites moist climate phases are well documented again during the late ladinian followed by a return to dry conditions the late ladinian early carnian platforms prograded toward the eastern dolomites depocentre eventually infilling almost the whole of the accommodation space the middle portion of the carnian recorded renewed sharply moist phases associated with the demise of the rimmed platforms and with the return to loose sediment ramps at least four separated humid fluctuations can be identified in this carnian interval alone climate then returned to persistent aridity until the late norian moist phase

the origin of volcano tectonic earthquake swarms volcano tectonic vt seismicity is commonly recorded prior to and during eruptions vt seismicity may reflect stresses induced by dike propagation as indicated by propagating hypocenters and fault plane solutions fps reflecting regional stresses or stresses induced by dike inflation indicated by randomly distributed hypocenters and fps with pressure axes rotated 90 to regional maximum compression although numerical models of dike induced stresses indicate that both regimes should occur during dike emplacement this has not yet been observed according to published seismic data instead 90 rotated fps are observed in some cases while propagating hypocenters mark dike formation in other cases we suggest that differences in the seismic expression of upper crustal magma migration may result from differences in the regional tectonic setting and in the nature of magma wall rock interactions ultimately it may be possible to use information contained in vt seismicity to forecast changes in a volcano s behavior by establishing the characteristic stress field response for a given volcano or through a deeper understanding of the complex relationships between vt seismicity local crustal stresses and the physical mechanisms of magma migration

differences of precursory seismic energy release for the 2007 effusive dome forming and 2014 plinian eruptions at kelud volcano indonesia abstract early warnings of the timing style and size of volcanic eruptions made on the basis of seismic monitoring are important for mitigation of the hazards associated with volcanic eruptions we calculated the rates of seismic energy release at kelud volcano indonesia preceding both the 2007 effusive lava dome eruption and the 2014 plinian eruption for the 2007 eruption there was first a step wise increase in the rate of release of seismic energy followed by a gradual decrease until the eruption for the 2014 eruption the rate of energy release was almost constant until 10 days before the eruption then gradually increased until there was a dramatic acceleration during the last day before the eruption the total seismic energy released by the 2007 and 2014 eruptions were 3 10 8 j and 2 2 10 9 j respectively the relative difference between the ejected volumes of the 2007 and 2014 eruptions is roughly equivalent to that of the total seismic energy released preceding the eruptions we conducted several trials of the material failure forecast method ffm applying it to the square root of the rate of seismic energy released to assess its usefulness for predicting the timing of eruptions the predicted onset of the 2007 eruption was one day earlier than the actual eruption and the seismic energy release preceding the actual eruption did not increase dramatically as suggested by the ffm model several trials of ffm for the 2014 eruption predicted the onset of the eruption to be three days to two weeks later than the actual eruption even as the end time of the ffm time window approaches several hours to 10 min before the actual eruption onset the predicted eruption onset is still 3 h later than the actual onset thus the results of our ffm modeling did not show the method to be useful for predicting eruption times for kelud volcano the differences of the ffm modeling results for the 2007 and 2014 eruptions likely reflect the differences in the rate of energy release immediately before the two eruptions a deceleration before the 2007 eruption and an acceleration before the 2014 eruption these differences may reflect differences in precursory processes for effusive lava dome and plinian eruptions

geophysical characteristics of dacite volcanism the 1977 1978 eruption of usu volcano abstract the 1977 1978 eruption of usu volcano is discussed from the geophysical standpoint as a classic example of dacite volcanism the activities of dacitic volcanoes are characterized by persistent earthquake swarms and remarkable crustal deformations due to the high viscosity of the magmas the former include shocks felt near the volcanoes and the latter accompany formation of lava domes or cryptodomes the hypocenters of the earthquakes occurring beneath usu volcano have been located precisely their distribution defines an earthquake free zone which underlies the area of doming within the summit crater this zone is regarded as occupied by viscous magma the domings within the summit crater forming the cryptodomes have amounted to about 160 m in addition to uplift they showed thrusting towards the northeast as a result the northeastern foot of the volcano has contracted by about 150 m the relation between crustal deformation and earthquake occurrence is examined and it is found that the abrupt domings are accompanied by the larger earthquakes m 3 4 3 both the seismic activity and the ground deformation are shown to have a unique and common energy source the energy of activities of usu volcano consists of the explosive type the deformation type and the seismic type the second and the third are in parallel with each other in discharges and both energies are complementary to the explosive energy the explosive energy and the seismic energy have been calculated for an explosion sequence and it is concluded that the deformation energy is about 10 times greater than the seismic energy the discharge rate of the seismic energy and the upheaval rates of the cryptodomes have continued to decrease since the outburst of the eruption except for a small increase at the end of january 1978 eruptions are governed not only by the supply of the energies but also by the depth of the magma which has gradually approached the surface the last eruption occurred in october 1978 however the crustal deformations and the earthquake swarms are still proceeding as of january 1980 albeit at a lower rate of activity

meso cenozoic basin and carbonate platform development in the sw dolomites unraveled by basin modelling and apatite ft analysis rosengarten and latemar northern italy abstract the rosengarten and latemar middle triassic carbonate platforms indicate similar subsidence patterns during equivalent times of platform evolution as calculated by numerical basin reverse modelling in the case of rosengarten and latemar thermo tectonic subsidence is the most significant among all three subsidence components thermo tectonic s flexural s compaction induced s hence the influence of differential tectonics as recorded in the formation of structural highs and lows in the dolomites during the lower to middle anisian almost ceases in late anisian times basin modelling of rosengarten and latemar requires the correlation and integration of two sets of chronostratigraphic data from buchenstein fm basin and schlern dolomite fm 1 platform subsidence modelling argues for a microcycle i e a single shallowing upward cycle duration of less than 1 97 ka in the cyclic succession at latemar however previous time series analyses identify milankovitch cyclicities in larger order cycle stacking patterns and thus indicate a microcycle duration of 4 2 ka according to each model total subsidence reaches values of 650 700 m ma 4 2 ka model or 780 850 m ma 1 97 ka model during the first stage of platform evolution as both platforms successfully keep up with this subsidence peak it is evident that the carbonate factory despite its low diversity must have recovered from the p t faunal crisis after this regionally observed peak subsidence drops and triggers fast progradation at rosengarten subsidence in the study area is controlled by active strike slip tectonics and the subsequent formation of a magmatic chamber predazzo monzoni above the deep reaching truden stava line the area close to this tectonic line and to the volcanic centre of predazzo monzoni undergoes a higher heat flow pulse during the late ladinian and is possibly buried at shallower levels than the rosengarten area as shown by fission tracks in apatites the heat flow pulse almost disappears laterally underlining the localised thermal influence of the late ladinian volcano thermal event of predazzo monzoni

thermal cooling of the oceanic lithosphere new constraints from geoid height data abstract up to now tests of thermal models of the oceanic lithosphere as it cools and moves away from the ridge crest have been based mainly on topography and heat flow data however large areas of the ocean floor deviate from the normal subsidence due to thermal contraction and heat flow data are not very sensitive to the form of the model cooling of the lithosphere causes a short wavelength step in the geoid across fracture zones that can also be used to constrain thermal models we have analyzed geoid data at fracture zones from the seasat altimeter measurements in the entire pacific ocean and redetermined parameters of the cooling models we find that the data reveal two distinct regimes of cooling one for seafloor ages in the range 0 30 ma the other beyond 30 ma this does not appear to be correlated with particular fracture zones but rather it is representative of the whole area studied i e the entire south pacific and northeast pacific ocean these two trends may be interpreted in terms of two different asymptotic thermal thicknesses of the plate model the smaller thermal thickness 65 km found for ages from the results obtained in this study we conclude that the half space cooling model is unable to explain the data that beyond 30 ma a simple plate model gives a satisfactory fit to the data but in the younger plate portion ages

reconstructing 800 years of historical eruptive activity at popocatepetl volcano mexico pictorial and written documents spanning 800 years were analyzed for information about historical eruptions at popocatepetl volcano these documents were prepared by several indigenous groups as well as by the spanish conquistadors and missionaries during their military campaigns and long term evangelization and colonization and later on by indian nobles and spanish historians pre columbian drawings show flames coming out of popocatepetl s crater while later descriptions from the spanish colonial period in mexico 1521 to 1821 refer to ash emission and ballistics lahars and some pumice falls similar to what were depicted in the thirteenth to sixteenth century drawings graphic information from the pre columbian codices colonial maps and paintings referring to the eruptions were correlated with historical accounts and religious chronicles thereby leading to the reconstruction of a more detailed sequence of eruptive events from such information it was possible for us to prepare ash distribution maps for the 1540 1592 and 1664 eruptions most of the known historical eruptions seem to be similar to those that have been occurring at popocatepetl since 1994 indicating the importance of ash emission and crater dome formation throughout its recent eruptive history the strongest eruptions occurred in 1510 1519 1540 1580 1664 and 2001 these produced widespread ash falls that affected both populated and rural areas duration of eruptive episodes during the past 800 years were estimated to have ranged from less than a year to more than 30 years separated by repose periods ranging between 7 and over 100 years

seismic precursors to the mount st helens eruptions in 1981 and 1982 six categories of seismic events are recognized on the seismograms from stations in the vicinity of mount st helens two types of high frequency earthquakes occur near the volcano and under the volcano at depths of more than 4 kilometers medium and low frequency earthquakes occur at shallow depths less than 3 kilometers within the volcano and increase in number and size before eruptions temporal changes in the energy release of the low frequency earthquakes have been used in predicting all the eruptions since october 1980 during and after eruptions two types of low frequency emergent surface events occur including rockfalls and steam or gas bursts from the lava dome

heterozoan carbonate deposition on a steep basement escarpment late miocene almeria south east spain heterozoan temperate water carbonates mixed with varying amounts of terrigenous grains and muddy matrix azagador limestone accumulated on and at the toe of an inherited escarpment during the late tortonian early messinian late miocene at the western margin of the almeria nijar basin in south east spain the escarpment was the eastern end of an uplifting antiform created by compressive folding of triassic rocks of the betic basement channelized coralline algal bryozoan rudstone to coarse grained packstone together with matrix supported conglomerate are the dominant lithofacies in the higher outcrops comprising the deposits on the slope these sediments mainly fill small canyon shaped half graben depressions formed by normal faults active before during and after carbonate sedimentation roughly bedded and roughly laminated coralline algal bryozoan rudstone to coarse grained packstone are the main lithofacies forming an apron of four small kilometre scale lobes at the toe of the south eastern side of the escarpment almeria area channelized and roughly bedded coralline algal bryozoan rudstone to coarse grained packstone conglomerates packstone and sandy silt accumulated in a small channel lobe system at the toe of the north eastern side of the escarpment las balsas area carbonate particles and terrigenous grains were sourced from shallow water settings and displaced downslope by sediment density flows that preferentially followed the canyon shaped depressions roughly laminated rudstone to packstone formed by grain flows on the initially very steep slope whereas the rest of the carbonate lithofacies were deposited by high density turbidite currents the steep escarpment and related break in slope at the toe favoured hydraulic jumps and the subsequent deposition of coarse grained low transport efficiency skeletal dominated sediment in the apron lobes accelerated uplift of the basement caused a relative sea level fall resulting in the formation of outer ramp carbonates on the apron lobes which were in turn overlain by lower messinian coral reefs this is the first known example of a base of slope apron within temperate water carbonate systems this article is protected by copyright all rights reserved

sub milankovitch and milankovitch forcing on a model mesozoic carbonate platform the latemar middle triassic italy basic shallowing upward cycles shu cycles and five bundled megacycles in the latemar platform have been widely regarded as a model example for precessional and eccentricity forcing in the mesozoic based on bio chronostratigraphic data recent studies questioned this particular type of milankovitch forcing on the latemar cyclic series we present an integrated model that incorporates i new cyclostratigraphic data ii new and existing bio chronostratigraphic data and iii new spectral analyses the basic shu cycles in the latemar reflect sub milankovitch control cycle bundles of 1 4 5 megacycles shu cycles indicate precessional forcing they do not reflect eccentricity superimposed on precessional forcing spectral analyses reveal highly significant ratios in the large scale cycle bundlings stacking patterns of 1 9 9 and 1 24 0 shu cycles represent obliquity and short eccentricity forcing both sub milankovitch and milankovitch forcing potentially controlled shallow subtidal carbonate deposition in mesozoic greenhouse times cyclostratigraphic models require an integrated approach including bio and chronostratigraphic data

characterization of open and closed volcanic systems in indonesia and mexico using insar time series 1 we use 2007 2011 advanced land observing satellite alos data to perform an arc wide interferometric synthetic aperture radar insar time series survey of the trans mexican volcanic belt tmvb and to study time dependent ground deformation of four indonesian volcanoes selected following the 2007 2009 study of chaussard and amelung 2012 our objectives are to examine whether arc volcanoes exhibit long term edifice wide cyclic deformation patterns that can be used to characterize open and closed volcanic systems and to better constrain in which cases precursory inflation is expected we reveal deformation cycles at both regularly active and previously inactive indonesian volcanoes but we do not detect deformation in the tmvb reflecting a lower activity level we identify three types of relationships between deformation and activity inflation prior to eruption and associated with or followed by deflation kerinci and sinabung inflation without eruption and followed by slow deflation agung and eruption without precursory deformation merapi colima and popocatepetl at merapi no significant deformation is detected even during eruption the first two cases correspond to closed volcanic systems and suggest that the traditional model of magmatic systems and eruptive cycles do apply to andesitic volcanoes i e inflation and deflation episodes associated with magma accumulation or volatile exsolution in a crustal reservoir followed by eruptions or in situ cooling in contrast the last case corresponds to open volcanic systems where no significant pressurization of the magmatic reservoirs is taking place prior to eruptions and thus no long term edifice wide ground deformation can be detected we discuss these results in terms of insar s potential for forecasting volcanic unrest

mapping the frequency magnitude distribution in asperities an improved technique to calculate recurrence times we hypothesize that highly stressed asperities may be defined by mapping anomalously low b values along the san andreas fault near parkfield the asperity under middle mountain with its b 0 46 can be distinguished from all other parts of the fault surface likewise along the calaveras fault the northern asperity of the morgan hill 1984 m6 2 rupture can be identified by its low b of 0 5 as a high stress patch along the fault we add further evidence to the observations that the b value of the frequency magnitude relationship of earthquakes is inversely proportional to stress by showing that it decreases with depth in the parkfield segment of the san andreas and along the calaveras fault in both of these areas b values above and below 5 km depth are 1 2 and 0 8 respectively we propose that probabilistic recurrence times tr based on the seismicity parameters a and b should be calculated from their values within asperities only instead of from the values of the entire rupture area of the maximum expected earthquake the strong patches on faults control the time of rupture because they are capable of accumulating larger stresses than the rest of the fault zone which slips along passively when an asperity breaks therefore no information on tr is contained in the passive fault segments only in the asperities at parkfield the probabilistic estimates of tr derived from the data in the whole rupture and in the asperity only are 72 18 24 and 23 12 18 years respectively compared to the historically observed repeat time of 22 years at morgan hill the tr estimates are 122 46 76 and 78 47 110 years respectively compared to the observed repeat time of 72 years

experience in the short term eruption forecasting at volcan de colima mexico and public response to forecasts the persistent eruptive activity of volcan de colima during the last 10 years and the availability of continuous seismic data from a monitoring system have permitted in some cases short term recognition of eruption precursors on the time scale of days before eruptions the sought precursory pattern is an accelerated rate of seismic energy release several cases of seismicity preceding eruptions are analyzed and three types of situations are briefly discussed a no precursory patterns can be recognized b precursory patterns are difficult to recognize or appear over time scales too short to allow response and c clear precursory patterns can be recognized the case of forecasting the november 20 1998 eruption of volcan de colima which influenced the public response is briefly discussed

the giant popocatepetl stirs in about 800 ad the mexican volcano popocatepetl exploded sending up several cubic kilometres of ash and pumice and burying the surrounding area since then it has been relatively quiet but every few decades it threatens to explode again which could this time be catastrophic as the area is now one of the most densely populated in mexico seismic activity and eruptions are now increasing with ash falls even 70 km away in mexico city

a model to describe precursory material failure phenomena applications to short term forecasting at colima volcano mexico some volcanoes exhibit at times accelerating strain and seismicity before eruptions different authors have used this behavior to predict eruptions and to develop materials science models here a linear kelvin voigt viscoelastic model is proposed to describe the observed behavior this model also has applications to other failure phenomena such as landslides the strain rate of a variety of materials under constant stress after an instantaneous elastic response is found to be well described by a general relaxation law dot varepsilon left t right b over 1 st where b and s are parameters depending on the material and its creep state whether the creep regime is primary or tertiary depends upon the sign of s s 0 corresponds to pseudoviscous flow the creep behavior of the viscoelastic body is analyzed for different load histories it is found that the body has an exponential distribution of retardation frequencies that may or may not converge depending on the sign of s according to the model tertiary creep implies material degradation and a critical weakening of the medium leading to a runaway growth of the strain and seismic energy release rates if tertiary creep is detected time of failure predictions may be done from field data through determination of two model parameters for varying loads the model response compare well with reported examples of pre eruptive volcano behavior and with reported results of landslide experiments the model is tested with the july 1994 in hindsight and november 1998 in foresight colima volcano eruptions although this method provides some guidance in estimating the time over which accelerating volcanic precursors may end in an eruption it is emphasized that eruptions may fail to occur at the estimated time or may not occur at all on the other hand eruptions may not be preceded by such a behavior

sedimentation in shallow to deep water carbonate environments across a sequence boundary effects of a fall in sea level on the evolution of a carbonate system ladinian carnian eastern lombardy italy in the concarena pizzo camino massif lombardy basin southern alps italy the lateral transition from ladinian carnian carbonate platforms to coeval intraplatform basins is preserved the succession records the sedimentological evidence of a sea level fall on a flat topped platform with a narrow marginal reef rim and its effects in the adjacent deeper water basin repeated high frequency exposures of the platform top are recorded by a peritidal supratidal succession that overlies subtidal inner platform facies of the former highstand system tract hst on the slope and in the basin the sea level fall is recorded by a few metre thick succession of bioclastic packstones these facies directly lie on coarse clinostratified breccia bodies slope facies of the former hst or on resedimented well bedded dark laminated limestones basinal facies of the hst this facies distribution indicates that during the sea level fall carbonate production on the platform top decreased rapidly and that sedimentation in the basin was mainly represented by condensed facies microfacies record an enrichment during low stand in pelagic biota packstones with radiolarians and spiculae whereas the occurrence of platform derived shallow water materials is limited to thin lenses of reworked and micritized fe rich oolites and bioclasts mainly pelecypods and echinoderms the facies association in the concarena pizzo camino massif demonstrates that a highly productive carbonate factory was almost completely turned off during the emergence of the platform top at a sequence boundary leading to low stand starvation in the basin the reconstruction of the stratigraphic evolution of the concarena pizzo camino carbonate platform therefore represents a significant case history for the study of the behaviour of ancient carbonate systems during a fall in sea level independent of its origin eustatic or tectonic

earthquake classification location and error analysis in a volcanic environment implications for the magmatic system of the 1989 1990 eruptions at redoubt volcano alaska abstract determination of the precise locations of seismic events associated with the 1989 1990 eruptions of redoubt volcano posed a number of problems including poorly known crustal velocities a sparse station distribution and an abundance of events with emergent phase onsets in addition the high relief of the volcano could not be incorporated into the hypoellipse earthquake location algorithm this algorithm was modified to allow hypocenters to be located above the elevation of the seismic stations the velocity model was calibrated on the basis of a posteruptive seismic survey in which four chemical explosions were recorded by eight stations of the permanent network supplemented with 20 temporary seismographs deployed on and around the volcanic edifice the model consists of a stack of homogeneous horizontal layers setting the top of the model at the summit allows events to be located anywhere within the volcanic edifice detailed analysis of hypocentral errors shows that the long period lp events constituting the vigorous 23 hour swarm that preceded the initial eruption on december 14 could have originated from a point 1 4 km below the crater floor a similar analysis of lp events in the swarm preceding the major eruption on january 2 shows they also could have originated from a point the location of which is shifted 0 8 km northwest and 0 7 km deeper than the source of the initial swarm we suggest this shift in lp activity reflects a northward jump in the pathway for magmatic gases caused by the sealing of the initial pathway by magma extrusion during the last half of december volcano tectonic vt earthquakes did not occur until after the initial 23 hour long swarm they began slowly just below the lp source and their rate of occurrence increased after the eruption of 01 52 ast on december 15 when they shifted to depths of 6 to 10 km after january 2 the vt activity migrated gradually northward this migration suggests northward propagating withdrawal of magma from a plexus of dikes and or sills located in the 6 to 10 km depth range precise relocations of selected events prior to january 2 clearly resolve a narrow steeply dipping pencil shaped concentration of activity in the depth range of 1 7 km which illuminates the conduit along which magma was transported to the surface a third event type named hybrid which blends the characteristics of both vt and lp events originates just below the lp source and may reflect brittle failure along a zone intersecting a fluid filled crack the distribution of hybrid events is elongated 0 2 0 4 km in an east west direction this distribution may offer constraints on the orientation and size of the fluid filled crack inferred to be the source of the lp events

high resolution magnetostratigraphic and lithostratigraphic correlations in middle triassic pelagic carbonates from the dolomites northern italy new magnetostratigraphic and lithostratigraphic data are reported from the pedraces and belvedere limestone sections from the dolomites region of northern italy these sections are comprised of the buchenstein beds of late anisian to ladinian middle triassic age the results from pedraces and belvedere are compared with data from the biostratigraphically and isotopically constrained frotschbach and seceda sections from the literature a satisfactory magnetostratigraphic correlation is obtained on laterally traceable limestone and volcaniclastic intervals these marker beds are then used to extend lithostratigraphic correlations to additional key sections from a palaeogeographically coherent area of around 500 km2 the aim of this study is to unravel the spatial and temporal evolution of the buchenstein basin and the surrounding carbonate platforms platforms in the northwestern dolomites show an early stage of aggradation followed by progradation whereas in the central dolomites the cernera platform after fast initial aggradation drowned and became a pelagic seamount in the intervening buchenstein basin the diverential subsidence between the northwestern and central dolomites is manifested by the lateral increase of thickness of lower pietra verde volcaniclastic sediments accumulation of volcaniclastic material reworked from adjacent carbonate platform slopes characterised the more subsiding and unstable central dolomites in the pelagic carbonate intervals the persistence over tens of kilometres of bedding patterns suggests that carbonate material presumably washed out from the surrounding still active carbonate platforms was volumetrically small and homogeneously distributed throughout the uniformly subsiding buchenstein basin a milankovitch precessional origin for the platform interior cycles at latemar as suggested elsewhere implies a net accumulation rate of 2 m ma or less for the correlative interval of pelagic buchenstein beds this value divers significantly from the average value of around 10 m ma as calculated using high resolution isotopic age data for the buchenstein beds 2000 elsevier science b v all rights reserved

distributed fracturing affecting isolated carbonate platforms the latemar platform natural laboratory dolomites north italy abstract isolated carbonate platforms are highly heterogeneous bodies and are typically composed of laterally juxtaposed first order domains with different sedimentological composition and organization i e a well stratified platform interior a massive margin and a slope with steeply dipping and poorly organized layers once subjected to overburden and tectonics forces directions and magnitudes of principal stresses inside such heterogeneous bodies are expected to deviate significantly from the regional trends potentially resulting in non obvious fracture patterns in addition characteristics such as fracture height and spacing distances are likely to change moving from one domain to the other as well as through time the middle triassic latemar platform dolomites n italy is affected by ubiquitous fractures typically joints orientation and height of more than 1500 fractures from 33 outcrops have been measured and their spatial characteristics were assessed with dedicated software fractures are organized in two directional sets nnw sse and ene wsw the orientation of each set is constant throughout the platform showing that the trajectories of causative stresses were not influenced by the platform architecture fracture spacings and heights of each set change moving from one domain to the other in the well bedded platform interior fractures are generally there are also significant differences in the characteristics of fractures of the two sets in all platform domains fractures of nnw sse set are less tall and more narrowly spaced than those of the ene wsw set in the platform interior fractures of the first set have a higher tendency to be confined to fracture units than those of the second set these differences are associated with diagenesis driven changes in bulk mechanical properties of the platform during its subsidence to maximum burial depth

villarrica volcano chile characteristics of the volcanic tremor and forecasting of small explosions by means of a material failure method villarrica volcano chile 39 42 s 71 93 w is one of the most active volcanoes in the andes it shows persistent strombolian activity in a small lava lake situated at the bottom of the summit crater from september to december 2000 the volcano exhibited anomalous behaviour after a regional tectonic seismic event on 22 september the eruption of a small volume of lava apparently plugged the conduit this situation then lasted for ten days on 5 and 8 october a series of explosions reopened the system this eruption behaviour has allowed us to study the evolution of the characteristic tremor in the open and closed states of the conduit a shift in the peak frequency from 1 hz open to 2 hz closed the explosions related to the opening of the conduit were forecasted by means of a material failure method

global and regional variations in tropical marine environments of gondwana as revealed by a multi stable isotope study middle triassic anisian israel levant basin abstract the world during the early middle triassic anisian was characterized by a distinct recovery of the carbonate factory after the permian triassic crisis this recovery seems to have passed over the anisian environment on the tropical northern margin of gondwana israel levant basin and to have resulted in the low diversity of barren horizons of carbonate secreting organisms four anisian successions the ramon 1 hameishar 1 nafha 1 and david 1 boreholes were studied to decode the factors preventing regional recovery a multi proxy analysis was performed on these boreholes including the carbonate siliciclastic ratio total organic carbon toc carbon nitrogen c n ratio and inorganic carbon 13ccarb oxygen 18ocarb and nitrogen 15n isotopic compositions the aim of assessing the combination of these proxies was to characterize the geochemical conditions in the regional basins these successions record two c cycle perturbation events characterized by negative shifts in 13ccarb values and recognized in most successions indicating the land marine teleconnection effect on the c cycle perturbation the 18ocarb excursions revealed similar oscillation trends with global warming evidenced by increasing circumtropical precipitation and terrestrial influxes whereas global cooling was reflected by increased carbonate factory production the low 15n values in all of the studied successions indicated the presence and flourishing of n fixers the absence or scarcity of carbonate secreting organisms suggests that these n fixers were the source of the carbonate fraction in the sediments episodic events with high 15n values suggest an accumulation of terrestrial organic matter om or oxygenation events allowing short term colonization by benthic fauna at the marine sites