novel retrieval of volcanic so2 abundance from ultraviolet spectra projects i firb miur simulazione dei flussi lavici con gli automi cellulari n rbau01rmz4 002 ii sviluppo di sistemi di monitoraggio funded by dipartimento di protezione civile della regione sicilia ingv istituto nazionale di geofisica e vulcanologia sezione di catania italy iii eu funded sixth framework programme project 18354 novac iv leverhulme trust fellowship

development of cleavage in limestones of a fold thrust belt in eastern new york abstract tectonic cleavage has developed in lower devonian limestones of the hudson valley fold thrust belt in new york state morphology and distribution of cleavage in these limestones is controlled by the amount of clay quartz matrix present and by strain only limestones with greater than 10 clay quartz matrix developed widespread cleavage x ray diffraction analyses indicate that the clay matrix was altered during deformation the width of the 001 illite peak in cleaved lime wackestone is less than that in uncleaved lime wackestone from the same stratigraphic level a minimum of 10 clay is necessary to provide interconnectivity between sites of dissolution and the free fluid system preliminary analyses of bulk chemistry indicate that calcite is removed from the local rock system during cleavage development supporting proposals that circulation of fluid through the rock plays a major role in the development of cleavage textural evidence suggests that both pressure solution and free face dissolution contribute to the removal of ions at grain boundaries cross cutting relations indicate that cleavage was initiated early during the development of the fold thrust belt but continued to develop during the late stages of folding

reconstructing the kinematic evolution of curved mountain belts internal strain patterns in the wyoming salient sevier thrust belt u s a analyses of mesoscopic structural and strain patterns in red beds of the triassic ankareh formation and limestones of the jurassic twin creek formation in concert with complementary paleomagnetic studies constrain the three dimensional kinematic evolution of curved fold and thrust systems in the wyoming salient of the sevier thrust belt spaced cleavage fracture and vein networks minor folds and minor faults in limestones and red beds accommodated early layer parallel shortening lps concentrated in front of the growing thrust wedge along with minor strike parallel extension and wrench shear related to the development of orogenic curvature strain estimated using mass balance relations for cleavage seams crinoid ossicles in bioclastic limestone and reduction spots in red beds displays systematic regional patterns principal shortening directions are subperpendicular to structural trend around the salient reflecting a combination of primary curvature and secondary rotation of early lps fabrics lps magnitudes vary from 5 in central parts of the frontal hogsback thrust system where cleavage is absent to 10 30 in the more interior crawford thrust system where cleavage intensity is moderate to strong strain also increases toward the salient ends internal strain is a significant component of total deformation and should be considered when restoring cross sections strain patterns are consistent with a kinematic model involving curved fault slip and differential shortening that produced progressive secondary curvature during thrusting

oroclines thick and thin an orocline is a thrust belt or orogen that is curved in map view due to it having been bent or buckled about a vertical axis of rotation two distinct types of oroclines are recognized progressive and secondary progressive oroclines are restricted to the scale of a thrust sheet to thrust belt are thin skinned and develop during thrust sheet emplacement secondary oroclines are larger occurring at the scale of an orogen and are plate scale features that affect crust and lithospheric mantle unlike progressive oroclines which develop during initial orogenesis and in response to the same orogen perpendicular stress responsible for thrust sheet emplacement secondary oroclines are extra orogenic developing after initial orogenesis and in response to an orogen parallel principal compressive stress that is oriented at a high angle to the stress responsible for orogen development we present case studies of the wyoming salient a progressive orocline that characterizes the sevier thrust belt of the western united states and the coupled cantabrian and central iberian oroclines which are linked secondary oroclines affecting the variscan orogen of iberia the vertical axis rotations involved in progressive and secondary orocline formation are most readily quantified through paleomagnetic analysis detailed three dimensional palinspastic restoration that incorporates translation rotation and strain can distinguish the role if any of primary curvature in progressive oroclines the use of tectonic vectors such as paleocurrent directions provides a means of recognizing and characterizing the initial geometry of secondary oroclines because secondary oroclines involve the entire lithosphere detailed studies of coeval metamorphism and magmatism provide a means of constraining the fate of the mantle lithosphere during oroclinal buckling

late stage tectonic evolution of the al hajar mountains oman new constraints from palaeogene sedimentary units and low temperature thermochronometry mountain building in the al hajar mountains ne oman occurred during two major shortening stages related to the convergence between africa arabia and eurasia separated by nearly 30 ma of tectonic quiescence most of the shortening was accommodated during the late cretaceous when northward subduction of the neo tethys ocean was followed by the ophiolites obduction on top of the former mesozoic margin this shortening event lasted until the latest santonian early campanian maastrichtian to eocene carbonates unconformably overlie the eroded nappes and seal the cretaceous foredeep these neo autochthonous post nappe sedimentary rocks were deformed along with the underlying cretaceous tectonic pile during the second shortening event itself including two main exhumation stages in this study we combine remotely sensed structural data seismic interpretation field based structural investigations and apatite u th he ahe cooling ages to obtain new insights into the cenozoic deformation stage seismic interpretation indicates the occurrence of a late eocene flexural basin later deformed by an oligocene thrusting event during which the post nappe succession and the underlying cretaceous nappes of the internal foredeep were uplifted this stage was followed by folding of the post nappe succession during the miocene ahe data from detrital siliciclastic deposits in the frontal area of the mountain chain provide cooling ages spanning from 17 3 to 42 ma consistent with available data for the structural culminations of oman our work points out how renewal of flexural subsidence in the foredeep and uplift of the mountain belt were coeval processes followed by layer parallel shortening preceding final fold amplification

cleavage fold relationships and their implications for transected folds an example from southwest virginia u s a abstract a non coaxial deformation involving pre folding initiation of cleavage perpendicular to bedding is proposed to explain non axial planar cleavage associated with mesoscopic folds in part of the appalachian foreland thrust belt of southwest virginia folds are gently plunging asymmetric upright to slightly inclined sinusoidal forms with non axial fanning cleavage they show extreme local variations in type and degree of transection and the consistency of transection direction these relations are further complicated by hinge migration cleavage fan angles bedding cleavage angles and transection values appear influenced by fold tightness and in part by fold flattening strain fold flattening increments are considered simultaneous with folding axial surface traces and not cleavage traces coincide with the principal extension direction in fold profiles geometric modelling of cleavage fanning and bedding cleavage angle variations for various theoretical folding modes suggest that folding in limestone and sandstone layers was by tangential longitudinal strain significant shape modification and change in bedding cleavage relations occurred after limb dips of 40 and 50 were attained in limestone and sandstone respectively mud rock class 1c folds with convergent cleavage fans show features transitional between buckling and flexural flow initiation of cleavage fabrics during layer parallel shortening prior to significant folding may be important for cleavage evolution in some deformed rocks

thrust sheet rotation and out of plane strains associated with oblique ramps an example from the wyoming salient u s a abstract movement over oblique thrust ramps results in local thrust sheet rotation and principal strains which deviate from the transport plane resulting folds faults and deformation fabrics are superposed on those associated with displacement on frontal ramps the south fork thrust a hangingwall imbricate of the absaroka thrust sheet sw wyoming has a steeply dipping 70 small displacement 300 m oblique ramp in the hangingwall and footwall which makes an angle of 25 to the regional transport direction two penetrative deformation events are recorded by folding stylolitic cleavage and calcite twinning strains in the deformed hangingwall and footwall the first is e to se directed layer parallel shortening prior to or during motion of the absaroka thrust sheet the second event indicates ne directed shortening unique to the oblique ramp at a high angle to ramp strike at the trailing frontal ramp oblique ramp intersection folds in the footwall and normal faults in the hangingwall reflect local strike parallel shortening and extension due to out of plane deflection of the wallrock during displacement the out of plane strains arc consistent with those predicted by kinematic and mechanical models in the hangingwall of the oblique ramp cross strike fractures and bedding are rotated 30 counterclockwise about a vertical axis with respect to structural domains to the north and south due to differential displacement on the south fork thrust stylolitic cleavage and caleite strains unique to the oblique ramp show a similar change in attitude indicating the rotation was the latest recorded stage of deformation in general if an oblique ramp is shallowly dipping the hangingwall may move from the lower flat up the ramp and onto the upper hat if an oblique ramp has a steep dip as in the case of the south fork thrust relatively greater sliding and bending resistance may impede displacement up the ramp and upper flat further transport of the thrust sheet is then accommodated by footwall deformation and hangingwall rotation

opposite vergence of a kink fold and pressure solution cleavage southeast spain a study of the relation between paleostress and fold kinematics abstract pressure solution cleavages define vergences that are opposite to those of asymmetric kink folds in limestones from the betic foreland southeast spain this cleavage fold relation is explained by an evaluation of paleostress and kinematics during kinking it is concluded that stress orientations deduced from stylolites match with models of kinking in non metamorphic rocks in this case opposite vergence of cleavage and folds is the logical consequence of the deformation mechanisms operating at different scales

microstructures deformation mechanisms and strain patterns in a vertical profile inner appalachian fold thrust belt alabama a core from the american anniston no 1 well drilled in the pell city thrust sheet calhoun county alabama provides an excellent scientific opportunity to study in a vertical profile the deformation mechanisms and strain patterns associated with large scale structures the core contains stratigraphic units from cambrian to mississippian in age and two major thrust faults a detailed structural analysis revealed two deformation episodes a pre orogenic deformation and alleghanian orogenic deformation in the pre orogenic deformation synsedimentary folds and growth faults are the characteristic early structures and normal faults formed in lithifield rocks later during alleghanian deformation earlier fractures are overprinted by later s1 penetrative structures in limestone shale and siltstone within thrust sheets s1 is solution cleavage dolomites in the thrust sheets were deformed by fracturing and no penetrative cleavages formed in major fault zones s1 mylonitic foliation formed in limestone shale and siltstone fault related dolomites were deformed cataclastically and no s surfaces formed strain magnitude increases towards major thrust faults in both the hanging walls and footwalls for the typical fault configuration in the core with limestone dolomite in the hanging wall and shale siltstone in the footwall strain is mainly caused by pressure solution and cataclasis in the hanging wall and by plastic deformation in the footwall

development of slaty cleavage and degree of very low grade metamorphism a review illite crystallinity ic and other indicators of the grade of very low grade metamorphism associated with the appearance of various stages of slaty cleavage in phyllosilicate rich rocks have been compiled from a wide variety of terranes ic values have been converted to a kubler equivalent standard scale but the diverse characterizations of the cleavage fabrics in published descriptions do not always allow an unequivocal identification of equivalent stages of cleavage development nevertheless there exists a distinct relationship between grade and the appearance of various stages of cleavage development 1 indications of incipient slaty cleavage such as s0 s1 pencil structure appearance of primary s1 crenulation cleavage and of closely spaced cleavage without parallel fabric in the microlithons is associated with a wide range of mostly medium and high grade diagenetic ic values 2 the appearance of smooth cleavage with a strong parallel fabric in the microlithons and or quartz mica beards and the chlorite mica stacks shortened at a high angle to 001 and of irregular cleavage in sandy beds is associated with a much narrower range of predominantly low and medium grade anchimetamorphic grades rarely high grade diagenetic the first appearance of these stages of cleavage development with higher grades can often be related to post kinematic magmatic heating polymetamorphism pre cleavage metamorphism or static recrystallization without cleavage formation for example in low strain zones there exists a relationship between finite strain fabric and metamorphic grade in mudstones and slates in coarser clastic rocks the same finite strain fabric relationship occurs at appreciably higher grades a relationship between finite strain in carbonate rocks and ic in the nearby rocks has been reported from the helvetic zone of the swiss alps the earlier stages of cleavage formation are associated with little improvement in ic the narrow range of ic associated with smooth cleavage is concluded to represent recrystallization and grain growth concurrent with cleavage formation

a multidisciplinary approach to detect active pathways for magma migration and eruption at mt etna sicily italy before the 2001 and 2002 2003 eruptions two strong flank eruptions occurred in july august 2001 and from late october 2002 to late january 2003 at mt etna volcano the two eruptions mainly involved the upper southern flank of the volcano a particularly active area during the last 30 years damaging several tourist facilities and threatening some villages the composite eruptive activity on the upper southern flank of mt etna during 2001 2003 has confirmed a posteriori the results of a multidisciplinary study started well before its occurrence by combining geological seismic and geochemical data gathered in this part of the volcano we were able in fact to highlight fractured zones likely to be re activated in the near future in this area where the largest majority of eruptive fissures in the recent past opened along n120 to n180 ranging directions the spatial distribution of earthquake epicentres during the period june 30th 2000 june 30th 2001 showed the greatest frequency in a sector compatible with both the direction of the main fissures of the pre 2001 period and that of the 2001 and 2002 lateral eruptions soil co2 and soil temperature surveys carried out in the studied area during the last 3 years have revealed anomalous release of magmatic fluids mainly co2 and water vapour along some nnw sse trending volcano tectonic structures of the area even during inter eruptive periods indicating persistent convective hydrothermal systems at shallow depth connected with the main feeder conduits of etna the temporal changes in both seismic and geochemical data from june 30th 2000 to june 30th 2001 were compared with the evolution of volcanic activity the comparison allowed to recognize at least two sequences of anomalous signals august to december 2000 and april to june 2001 likely related to episodes of step like magma ascent towards the surface as indicated by the following eruptive episodes the n120 to n180 structural directions are in accord with one of the main structural lines affecting eastern sicily they would be important pathways for magma uprise to the surface that will keep on feeding the eruptive activity of etna in the near future this study also pointed out the high instability of the southern slope of etna a sector where the potential hazard by lava flow invasion will remain high also in the near future

dynamics of a lava fountain revealed by geophysical geochemical and thermal satellite measurements the case of the 10 april 2011 mt etna eruption 1 geophysical tilt seismic tremor and gravity signals geochemical crater so2flux and infrared satellite measurements are presented and discussed to track the temporal evolution of the lava fountain episode occurring at mt etna volcano on 10 april 2011 the multi disciplinary approach provides insight into a gas rich magma source trapped in a shallow storage zone inside the volcano edifice this generated the fast ascending gas magma dispersed flow feeding the lava fountain and causing the depressurization of a deeper magma storage satellite thermal data allowed estimation of the amount of erupted lava which summed to the tephra volume yielded a total volume of erupted products of about 1 106 m3 thanks to the daylight occurrence of this eruptive episode the so2 emission rate was also estimated showing a degassing cycle reaching a peak of 15 000 mg d 1 with a mean daily value of 5 700 mg d 1 the so2 data from the previous fountain episode on 17 18 february to 10 april 2011 yielded a cumulative degassed magma volume of about 10 5 106 m3 indicating a ratio of roughly 10 1 between degassed and erupted volumes this volumetric balance differently from those previously estimated during different styles of volcanic activities with long term years recharging periods and middle term weeks to months effusive eruptions points toward the predominant role played by the gas phase in generating and driving this lava fountain episode

diachronous folding and cleavage in an intraplate setting central high atlas morocco determined through the study of remagnetizations abstract remagnetizations are common in intraplate basins when remagnetizations occur at an intermediate stage between different tectonic processes they can be used for paleo geometrical reconstructions and relative dating of different structures this has a particular interest in geological frameworks where other geological time markers are absent in order to apply this methodology it is necessary to calculate the regional remagnetization direction and subsequently to use this reference direction to restore the attitude of the beds at the moment of remagnetization acquisition in this work we use this methodology for dating a pervasive cleavage whose time of formation is controversial and the associated structures in the central high atlas morocco paleomagnetic directions from 64 sites were used to calculate the remagnetization direction d 330 9 i 35 1 a n 6 107 which is coincident with the albian cenomanian ca 100 m a expected direction for nw africa this direction was used to restore the mesozoic paleo geometry of beds allowing us to analyze bedding orientation cleavage and folding relationships between the present day and the cretaceous geometry after restoration we conclude that the development of cleavage post dates remagnetization being in relation with cenozoic basin inversion however the paleo geometry shows incipient folds at cretaceous times which can be related to an intra mesozoic compressional event

thermal effects of thrust faulting abstract calculations based on simple models of overthrust sheets in crystalline basement rocks show that significant thermal effects may result from their movements if rates are sufficiently high e g plate tectonic rates the thrust sheets sufficiently thick 5 10 and 15 km are modelled here the distances moved sufficiently large and for reasonable values of the coefficient of friction along the thrust plane overthrusting can cause metamorphic mineral zonations and heat flow anomalies observable in the field regions where large scale overthrusting has occurred should be characterized by a decrease with depth of grade of metamorphic mineral assemblages and anomalously low heat flow the theoretical effects are presented as a series of maximum temperature vs depth and heat flow vs time plots

thermochronology of lower cretaceous source rocks in the idaho wyoming thrust belt lower cretaceous organic rich source rocks that are thermally mature to postmature crop out on the absaroka darby and prospect plates in linear belts that run parallel to the trace of the thrusts in the idaho wyoming portion of the idaho wyoming utah thrust belt although the common assumption is that burial by thrust plates and the synorogenic sediments derived from them have been responsible for thermal maturation of the organic rich strata commercial amounts of hydrocarbons have not been found in structural traps in this portion of the thrust belt in a companion paper burtner and nigrini demonstrated that gravity driven fluid flow in the idaho wyoming portion of the thrust belt was responsible for moving large amounts of heat from the depths of the early cretaceous foreland basin eastward toward the stable platform in this paper we demonstrate through the application of organic maturation indicators and a new refinement of the apatite fission track technique that this process heated lower cretaceous organic rich source rocks to temperatures sufficient to generate hydrocarbons hydrocarbon generation and migration occurred prior to the development of the thrusts that are often assumed to have played a major role in the generation and entrapment of hydrocarbons in this portion of the thrust belt

relationship of spaced cleavage to folds and thrusts in the idaho utah wyoming thrust belt the idaho utah wyoming thrust belt of the rocky mountain cordillera preserves structures that developed at very shallow levels of the crust t 200 c the geometry of major structures is well documented and synorogenic conglomerates record the timing of movement on major thrusts spaced cleavage and pencil fracturing are developed within micrites of the jurassic twin creek formation the cleavage developed dominantly by pressure solution early in the deformation history of each thrust sheet aided by elevated temperatures and pressures in areas where increased overburden resulted from emplacement of earlier overriding sheets cleavage within any sheet is well developed in the area covered by the pre erosional extent of the previous sheet forelandward from this area cleavage intensity decreases drastically thermal modelling of the sheets agrees well with temperature estimates from illite crystallinity studies on material from the cleavage planes cleavage is axial planar to small folds and formed concurrently with small scale buckle folds and contraction faults during the early history of movement on each thrust however cleavage strongly fans about large scale folds formed later during movement suggesting passive rotation of cleavage with bedding during the later stages of thrust history the rotated cleavage may also be folded and overprinted by a second weaker cleavage during a second ramping or during movement on a later lower thrust cross folding may also develop as a result of lateral ramping thus complex patterns of interfering folds multiple cleavages and associated fiber filled fractures may be produced during motion on a single thrust fault and so magnify the problem of correlating cleavages and deciphering multiple deformations

formation and inversion of transtensional basins in the western part of the lachlan fold belt australia with emphasis on the cobar basin abstract the palaeozoic history of the western part of the lachlan fold belt in new south wales was dominated by strike slip tectonics in the latest silurian to late early devonian an area of crust 25 000 km2 lying west of the gilmore suture underwent regional sinistral transtension leading to the development of intracratonic successor basins troughs and flanking shelves the volcaniclastic deep water mount hope trough and rast trough the siliciclastic cobar basin and the volcanic rich canbelego mineral hill belt of the kopyje shelf all were initiated around the siluro devonian boundary they all show clear evidence of having evolved by both active syn rift processes and passive later post rift sag phase processes active syn rift faulting is best documented for the cobar basin and mount hope trough in the former case the synchronous activity on several fault sets suggests that the basin formed by sinistral transtension in response to a direction of maximum extension oriented ne sw structures formed during inversion of the cobar basin and canbelego mineral hill belt indicate closure under a dextral transpressive strain regime with a far field direction of maximum shortening oriented ne sw in the cobar basin shortening was partitioned into two structural zones a high strain zone in the east was developed into a positive half flower structure by re activation of early faults and by formation of short cut thrusts some with strike slip movement above an inferred steep strike slip fault intense subvertical cleavage a steep extension lineation and variably plunging folds are also present a lower strain zone to the west developed by syn depositional faults being activated as thrusts soling into a gently dipping detachment a subvertical cleavage and steep extension lineation are locally present and variably plunging folds are common whereas siluro devonian basin opening appeared to be synchronous in the western part of the fold belt the different period of basin inversion in the cobar region late early devonian and carboniferous may reflect different movement histories on the master strike slip faults in this part of the fold belt the gilmore suture and kiewa fault

behavior of illite and chlorite during pressure solution of shaly limestone of the kalkberg formation catskill new york textural and chemical changes occurring in illite and chlorite concomitant with pressure solution of limestone were studied in samples from the kalkberg formation of catskill new york using xrd and tem aem samples on one limb of an anticline are massive shaly limestones but those on the other have undergone extensive pressure solution and well developed cleavage is present illite and chlorite from the uncleaved shaly limestone are found in small individual packets 100 800 thick dispersed throughout the carbonate matrix with crystal morphologies characteristic of burial diagenesis phyllosilicates from the limb more affected by pressure solution occur in larger units 1 urn thick as stacks of subparallel packets 150 500 a thick such stacks are inferred to represent coalescence of smaller packets these data imply that the phyllosilicates are largely passive during pressure solution of limestone however localized solution recrystal lization is required by the coherent to semi coherent packet boundaries and the crystal morphologies present in the pressure solution sample the largely passive role is in contrast with the more active role of phyllosilicates in many shales and slates xrd data for illite show an increase in crystallinity in the pressure solution sample under isothermal conditions differences in illite crystallinity are adequately explained in large part by differences in crystal size with some contribution due to strain the data demonstrate that illite crystallinity cannot be unambiguously used in determining absolute or even relative temperatures

failed eruptions revealed by pattern classification analysis of gas emission and volcanic tremor data at mt etna italy during the spring of 2007 paroxysmal activity occurred at the southeast crater of mt etna always associated with sharp rises in the amplitude of the volcanic tremor activity ranged from strong strombolian explosions to lava fountains coupled with copious emission of lava flows and tephra during inter eruptive periods recurrent seismic unrest episodes were observed in the form of temporary enhancements of the volcanic tremor amplitude but they did not culminate in eruptive activity here we present the results of an analysis of these inter eruptive periods by integrating seismic volcanic tremor in soil radon plume so2 flux and thermal data so2 flux and thermal radiation are envisaged as the smoking gun and certifying that changes in seismic or radon data can be considered as volcanogenic short term changes were investigated by pattern classification based on kohonen maps and fuzzy clustering on volcanic tremor radon and ambient parameters pressure and temperature our results unveil failed eruptions between february and april 2007 that are explained as ascending magma batches which triggered repeated episodes of gas pulses and rock fracturing but that failed to reach the surface

time and temperature in petroleum formation application of lopatin s method to petroleum exploration n v lopatin in the soviet union has developed a method for taking both time and temperature into account as factors in thermal maturation of kerogen lopatin s time temperature index of maturity tti values correlate with the thermal regimes corresponding to generation and preservation of hydrocarbons because such information is potentially of great interest for oil exploration a calibration and evaluation have been made of lopatin s method within the limitations of the data presently available the following statements can be made 1 the rate of the chemical reactions involved in thermal maturation of organic material appears to double with every 10 c 18 f rise in temperature 2 threshold values of lopatin s time temperature index of maturity tti are 15 onset of oil generation 75 peak oil generation 160 end oil generation 500 40 oil preservation deadline 1 000 50 oil preservation deadline 1 500 wet gas preservation deadline 65 000 dry gas preservation deadline 3 tti values calculated from lopatin reconstructions consistently agree with other maturation parameters commonly used by petroleum geochemists potential applications of lopatin s method for oil exploration include timing of oil generation calculation of volume of hydrocarbons generated within a basin and determination of economic deadlines

continuous soil radon monitoring during the july 2006 etna eruption 1 continuous soil radon monitoring was carried out near the southeast crater sec of mt etna during the 10 day july 2006 strombolian effusive eruption this signal was compared with simultaneously acquired volcanic tremor and thermal radiance data the onset of explosive activity and a lava fountaining episode were preceded by some hours with increases in radon soil emission by 4 5 orders of magnitude which we interpret as precursors minor changes in eruptive behavior did not produce significant variations in the monitored parameters the remarkably high radon concentrations we observed are unprecedented in the literature we interpret peaks in radon activity as due primarily to microfracturing of uranium bearing rock these observations suggest that radon measurements in the summit area of etna are strongly controlled by the state of stress within the volcano and demonstrate the usefulness of radon data acquisition before and during eruptions citation neri m b behncke m burton g galli s giammanco e pecora e privitera and d reitano 2006 continuous soil radon monitoring during the july 2006 etna eruption geophys res lett 33 l24316 doi 10 1029 2006gl028394

graphic approach to determination of hydrocarbon maturation in overthrust terrains with the current exploration efforts in areas of overthrust tectonics it is important to evaluate efficiently and effectively the effects of thrust related thermal perturbations on hydrocarbon maturation a simple graphic technique which combines lopatin diagrams with theoretical models of temperatures in overthrust regimes allows one to develop relatively detailed models for the timing of hydrocarbon maturation in overthrust terrains these models provide the critical combination between rigorous consideration of thermal perturbations and simplification necessary for routine application the approach described here is applicable not only in cases of simple overthrusting at the surface but can also be modified to include the effects of multiple thrusting events she ts thrust in the subsurface and post thrusting erosion all of these models provide critical constraints on the timing of maturation and migration as well as information on the maturity of potential source rocks

thin skinned thrusting in the northern new england orogen central queensland australia regional cross sections of the northern new england orogen and eastern bowen basin in eastern queensland indicate that the climactic permian triassic deformation involved thin skinned tectonics with the development of a mountain front represented by a syncline formed by crustal delamination with wedging of a thrust sheet from the east the thrust sheet is exposed in the folded zone of the bowen basin and is characterized by upright nnw trending folds in late permian sediments the folds have a chevron to flattened chevron style and formed mainly by flexural slip at about 60 shortening with detachment from an underlying basement of paleozoic rocks farther east the basement is overlain by pervasively cleaved rocks of the gogango overfolded zone in which structures show a consistent westerly vergence these rocks overlie an inferred passive roof duplex in the underlying basement together the folded zone of the bowen basin and the gogango overfolded zone constitute a foreland fold thrust zone with a shortening of 50 90 km this implies that the new england orogen has been thrust west along a major east dipping detachment

partitioned tectonic shortening with emphasis on outcrop scale folding and flattening pindos fold and thrust belt peloponnese greece shortening estimates for fold thrust belts seldom take into consideration outcrop scale folding especially folding related to prethrusting layer parallel shortening lps and flattening the pindo

porphyroblast inclusion trails the key to orogenesis detailed microstructural analysis of inclusion trails in hundreds of garnet porphyroblasts from rocks where spiral shaped inclusion trails are common indicates that spiral shaped trails did not form by rotation of the growing porphyroblasts relative to geographic coordinates they formed instead by progressive growth by porphyroblasts over several sets of near orthogonal foliations that successively overprint one another the orientations of these near orthogonal foliations are alternately near vertical and near horizontal in all porphyroblasts examined this provides very strong evidence for lack of porphyroblast rotation the deformation path recorded by these porphyroblasts indicates that the process of orogenesis involves a multiply repeated two stage cycle of 1 crustal shortening and thickening with the development of a near vertical foliation with a steep stretching lineation followed by 2 gravitational instability and collapse of this uplifted pile with the development of a near horizontal foliation gravitational spreading near coaxial vertical shortening and consequent thrusting on the orogen margins correlation of inclusion trail overprinting relationships and asymmetry in porphyroblasts with foliation overprinting relationships observed in the field allows determination of where the rocks studied lie and have moved within an orogen this information combined with information about chemical zoning in porphyroblasts provides details about the structural metamorphic p t t paths the rocks have followed the ductile deformation environment in which a porphyroblast can rotate relative to geographic coordinates during orogenesis is spatially restricted in continental crust to vertical ductile tear transcurrent faults across which there is no component of bulk shortening or transpression

strain fabric associated with the meade thrust sheet implications for cross section balancing abstract emplacement of the meade thrust sheet southeastern idaho u s a was accompanied by the development of a strain fabric and significant footwall deformation characteristics of the strain fabric are based on strain estimates using pressure solution cleavage and deformed fossils within the jurassic twin creek formation the strain fabric formed during early layer parallel shortening at the thrust front and accommodates from 10 to 35 shortening within the incipient thrust sheet footwall strata were later folded above a detachment at the base of the twin creek formation and the early strain fabric was passively rotated the structural development of this area consisting of 1 strain fabric development 2 folding of the footwall and 3 the truncation of footwall structures by imbricates of the meade thrust are placed in a relative time frame to aid in section reconstruction the passive reorientation of the strain fabric and the truncation and incorporation of footwall structures into the thrust sheet are used as kinematic and geometric constraints for cross section balancing we present a sequential retrodeformation of the meade thrust sheet in which strain is removed from the cross section at the appropriate geometric stages in the deformation these sections illustrate some methods by which strain data can be incorporated into cross sections and also indicate the difficulty involved in balancing cross sections of internally deformed thrust sheets interpretation of these sections suggests that a significant amount of footwall deformation accompanied the emplacement of the meade thrust sheet and that footwall deformation is strongly controlled by the local stratigraphic package the sections also illustrate that the earliest deformation within a thrust sheet may be unrelated to motion on the underlying incipient thrust and that the trace of a thrust fault which cuts previously deformed strata will not restore to a typical ramp and flat geometry

strike slip fault propagation cleavage in carbonate rocks the mattinata fault zone southern apennines italy disjunctive spaced solution cleavage in carbonate rocks is genetically associated with the propagation of the left lateral strike slip mattinata fault in the gargano promontory italy typical cleavage development is restricted within the 200 300 mwide fault zone which is bounded by virtually unfractured wall rocks the cleavage consists of sub parallel solution surfaces which are often reactivated as sheared solution planes geometrical and kinematic relationships exist between the fault and the associated cleavage planes thus 1 cleavage fault intersection lines lie parallel to the fault and the sheared cleavage rotational axes and 2 the cleavage fault angle is almost constantly equal to 408 a model for the development of the mattinata fault is proposed in which the cleavage surfaces are interpreted as fault propagation deformations cleavage nucleates as solution planes at the front of the advancing fault as the result of stress concentration in this region two distinct time sequential processes are shown to operate during the fault propagation 1 typical millimetre to centimetre spaced solution surfaces form in the distal tip zone of the advancing fault plane 2 as the tip advances the fault plane breaks through the cleavage as minor shear displacements reactivate some of these nascent surfaces these observations may prove useful in understanding mechanisms for fault controlled enhanced reduced permeability and fluid pathways 1999 elsevier science ltd all rights reserved

timing of deformation in overthrust belt and foreland of idaho wyoming and utah a review of the timing and displacement evidence of the major structures of the western wyoming overthrust belt and foreland shows there is a progression in thrust displacement apparent duration of motion and palinspastic position of thrust traces from west to east those toward the west moved farther for an apparently longer period of time and are more widely spaced in their restored positions than those toward the east however average thrust velocities are all on the order of 0 5 0 5 cm yr 0 2 in yr foreland events are in part synchronous with thrust belt events and had an effect on them although dating precision varies widely on major normal faults present evidence does not contradict the generally held view that all normal faults postdate the youngest thrusting

solution cleavage and its relationship to major structures in the idaho utah wyoming thrust belt micrites of the jurassic twin creek formation in the idaho utah wyoming thrust belt show spaced cleavage developed during folding and thrusting cleavage in each thrust sheet forms mainly by pressure solution aided by elevated temperatures and pressures caused by increased overburden as a result of emplacement of earlier overriding thrust sheets within each thrust sheet cleavage develops early and is contemporaneous with microscopic to mesoscopic buckle folds and faults large scale ramp folds formed during major motion on the thrust postdate the cleavage and passively rotate it into major fans

double edge fault propagation folding geometry and kinematics abstract fault propagation folding is a common folding mechanism in thrust and fold belts and accretionary prisms several geometrical models relating the fold shape to the ramp shape have been proposed in all these models ramps always emanate from a basal fault and propagate upwards we have developed a new kinematic and geometric model of fault propagation folding named double edge fault propagation folding the model simulates folding at thrust ramps as a function of their nucleation site and propagation history within the folded multilayer the fold shape depends on the initial length and location of the ramp its dip and the s p ratio i e incremental ramp slip versus propagation of both the upper and lower ramp tips this solution increases the geometrical flexibility of fault propagation folding reducing for example the direct dependence between the backlimb dip and the ramp dip as double edge fault propagation folding is characterised by a backlimb panel not necessary parallel to the ramp non parallelism between the ramp and the backlimb is commonly observed in thrust related anticlines within fold and thrust belts and accretionary prisms the excess layer parallel shear imposed by the development of double edge fault propagation folding can be easily accommodated by discrete faulting and or penetrative deformation the dependence of the fold shape on the fault behaviour provides a tool for including the role of mechanical stratigraphy and environmental conditions of deformation into kinematic models natural examples of anticlines that could be modelled by double edge fault propagation are presented

sequences of mesostructures related to the development of alpine thrusts in the eastern pyrenees abstract the mesostructures formed during the development of an antiformal stack in the eastern pyrenees are studied the following structural evolution is proposed a pressure solution cleavage develops by layer parallel shortening at initial stages of the thrusting the cleavage is present in all units but mainly in the marls and marly limestones in the siliceous layers a weak cleavage and small scale thrust structures develop the cleavage and the bedding are deformed during the thrusting different structures form in various places of the antiformal stack where the bedding is flat lying southward directed layer parallel shears predominate in the hangingwall ramps kink bands disjunctive stylolitic cleavage and layer parallel shear opposite to the sense of thrust movement develop the described structures constitute a kinematical model for mesostructures developed during the evolution and ramping of thrusts

early orogenic deformation in the ionian zone of the hellenides effects of slab retreat and arching on syn orogenic stress evolution abstract in this work we report on early orogenic fracture patterns affecting a cretaceous to eocene sedimentary succession exposed in western greece these rocks belong to the cenozoic external hellenides which form the western portion of the aegean orocline the analysis of fracture type orientation and crosscutting relationships provides constraints on the stress and strain patterns during the early stages of orocline formation the fracture patterns in the study area includes early orogenic extensional fractures arranged into two mutually orthogonal sets these developed during progressive burial in the forebulge foredeep system ahead of the advancing compressive front tectonic solution seams at a high angle to bedding postdate these extensional structures solution seams are arranged in different sets oblique to each other and developed in the early stages of thrusting and folding extensional structures and solution seams are oblique to each other their orientation and crosscutting relationships provide evidence for clockwise vertical axis rotation of stress directions with time this is consistent with the progressive arching of the forebulge thrust belt system during progressive slab retreat

strain variations and three dimensional strain factorization at the transition from the southern to the central appalachians abstract the transition between the southern and the central appalachian foreland thrust system is a region subjected to at least two non coaxial deformations where typical two dimensional analyses such as cross section balancing or plane strain retro deformation cannot be applied three dimensional factorization can simulate the non coaxial strain history simulation results for compaction and layer parallel shortening lps were compared to finite strains of 16 quartz arenite samples from the tuscarora sandstone successful simulations indicate in the southern appalachians 30 35 total compaction by volume loss including a 4 5 9 e w horizontal shortening during lithification and 5 lps along 150 330 by plane strain or axial symmetric flattening in the central appalachians 30 35 total compaction by volume loss including a 3 7 n s horizontal shortening during lithification and 10 lps along 120 300 by plane strain or axial symmetric flattening in the transition zone 30 compaction by volume loss including a 3 e w horizontal shortening during lithification 5 southern lps along 150 330 by axial symmetric flattening and 5 10 central shortening along 130 or 140 by plane strain or axial symmetric flattening at 10 to the normal central trend from the simulations horizontal shortening in the southern appalachians during lithification in the mississippian was greater than the later alleghanian deformation this shortening probably represents a very early lps developed in unlithified sand that required less deviatoric stress to deform than did the cemented quartz arenites during later tectonic deformation also the oblique and weaker central tectonic lps in the transition zone probably represents behavior at the limits of central appalachian deformation finally the lps simulations indicate that axial symmetric flattening oblate strain is more successful than plane strain as the representative behavior so caution is recommended in assuming plane strain as the dominant strain behavior in orogenic forelands

competitive macroscopic deformation processes abstract macroscopic deformation mechanisms such as folding fracturing faulting and formation of rock fabrics compete with one another in a fashion similar to the competition among crystalline deformation mechanisms such as cataclasis grain boundary sliding dislocation creep and diffusive mass transfer many authors seek to develop a unique structural chronology for a given field area based on what are considered exclusive overprinting relationships between structures in contrast the approach taken here suggests that relative changes in external or internal variables within a rock mass can cause significantly different dominant types of macroscopic deformation to be developed in hand specimen and or outcrop at the same time rather than representing distinct structural facies observed dominant macroscopic features are waypoints in continuum processes

regional structural synthesis wyoming salient of western overthrust belt surface geologic mapping regional and high density reflection seismic data and information from approximately 370 wells have been combined to describe geometrically that area of the western overthrust belt between the snake river plain and the uinta uplift particular care has been taken to verify two dimensional interpretations of multiple thrust sheets by linear restoration by establishing equivalence of pre thrust lengths of affected beds one can gain confidence in interpreted structural geometries as well as generate data in regard to internal shortening and deformation intensity because of irresoluable geometric problems within sections 47 cross sections were developed at roughly 6 mi 10 km spacing to help verify changes in displacement or placement of key st uctural elements displacements of 0 to 32 mi 0 to 51 km have been demonstrated jurassic to paleocene sevier thrusts were active across a previously deformed cratonic shelf terrane and interacted with active structural elements such as the uinta uplift gros ventre range and moxa arch thrusts are progressively younger to the east except for the darby prospect pair in which the darby system is younger

brittle to ductile transition due to large strains along the white rock thrust wind river mountains wyoming abstract the deformed foreland of the rocky mountain cordilleras is characterized by major reverse faults that bring precambrian basement rocks to the surface the white rock thrust in the wind river mountains of wyoming is one such fault that developed at fairly shallow levels in the crust detailed study of grain size variations and textures within the fault zone provide a framework for discussion of the mechanics of movement along the fault textural criteria are suggested for distinguishing between dominantly brittle and dominantly ductile deformation a transition from brittle fracturing to ductile deformation is seen with increasing strain and resultant decrease in grain size along the fault zone diffusional creep in the final stages of deformation leads to strain softening and may allow large strains to take place along narrow zones at low deviatoric stresses this may be one way of obtaining large displacements along major faults at shallow levels in the crust

synfolding magnetization in the jurassic preuss sandstone wyoming idaho utah thrust belt the jurassic preuss sandstone exposed in five thrust plates of the wyoming idaho utah thrust belt carries directions of remanent magnetization that group most tightly after only partial unfolding field petrographic and rock magnetic evidence indicates that the carrier of this magnetization is detrital low ti titanomagnetite the detrital titanomagnetite was remagnetized at low temperatures 75 150 c probably completely during folding anisotropy of magnetic susceptibility and petrographic observations indicate that the detrital titanomagnetite has been affected by tectonic strain we suggest that low temperature remagnetization of the detrital titanomagnetite was either a viscous partial thermoremanent magnetization the acquisition of which was enhanced by stress or a piezoremanent magnetization that involved stress induced movement of domain walls during intracrystalline strain or was a combination of the two mechanisms stress may promote remagnetization at temperatures much lower than predicted by current theoretical models other mechanisms such as acquisition of chemical remanent magnetization during folding deflection of a prefolding magnetization by internal strain or combination of components of magnetization with different direction cannot account for the geometry of magnetization in the preuss the locus of acquisition of synfolding magnetization in the preuss migrated in conjunction with deformation in the thrust belt a model is presented in which synfolding magnetization was acquired during cooling and folding as strata moved up thrust ramps a lack of reverse polarity directions remains a puzzling feature of the remanence the remanent direction is tentatively interpreted to reflect the predominant polarity state during its acquisition over an extended rather than a discrete time period during folding in late cretaceous and early tertiary periods of predominantly normal polarity

deformation partitioning foliation successions and their significance for orogenesis hiding lengthy deformation histories in mylonites although orogenesis commonly lasts 100 million years a maximum of three foliations are usually preserved within any outcrop they record little of the total history due to the effects of preferential partitioning of progressive shearing along s0 such reactivation eventually destroys or rotates multiple successive foliations into parallelism with any layering that is present plate motion subjects a collisional orogen to spatially partitioned episodic but non stop deformation the bulk forces operating are horizontal and intermittently vertical associated with gravitational load due to crustal thickening forming sub vertical and sub horizontal foliations these orientations are preserved in the strain shadows of anything competent that hinders reactivation of the compositional layering deformation partitioning results in portions of rock remaining unaffected for many events gravitational collapse of over thickened orogen cores leads to significant extrusion in orogen rims and a dominance of sub horizontal foliations in the latter and episodically continues throughout orogenesis reactivation causes decrenulation and or rotation of foliations into parallelism with s0 destroying evidence that multiple sub vertical and sub horizontal foliations have developed except where preserved as inclusion trails in porphyroblasts and multiply truncated foliations in mylonites however the same processes operate in both the cores of orogens and ductile portions of their margins

three dimensional 3 d finite strain at the central andean orocline and implications for grain scale shortening in orogens three dimensional 3 d finite strain analyses from across the central andes are used to document the contribution of grain scale strain in quartzites and sandstones to the total shortening budget the results are compared to thermal stratigraphic and strain data from other fold and thrust belts to determine the influence of lithologic strength and deformation temperature on strain accommodation during orogenic evolution in the central andes 3 d best fit ellipsoids are inconsistently oriented relative to structural trends have short axes at high angles to bedding z mean plunge 78 21 and have bedding parallel long axes x mean plunge 6 24 ellipsoid shapes are dominantly oblate x y z indicate low natural octahedral shear strains e s 0 03 0 19 and have axial ratios that range from 1 02 1 0 81 e s 0 19 to 1 02 1 0 97 e s 0 03 highly variable r f data r f 1 0 5 0 fluctuations exceeding 100 indicate detrital grain shapes may overwhelm any measurable tectonic strain fabric recorded by grain geometry the best fit ellipsoids may reflect either weak compaction strain or they may be related to a depositional fabric at a minimum granular strain was insufficient to reset the detrital grain fabric and therefore grain scale strain in quartzites and sandstones is not a significant factor in deformation we suggest that the nonstrained nature of these stiffer lithologies indicates a lack of regional penetrative strain in the central andes like that quantified in similar lithologies in other orogens the regional lack of strain may be due to deformation temperatures

deformation and eruptions at mt etna italy a lesson from 15 years of observations this work was partly funded by ingv and the italian dpc and was supported by asi the preview project and crdc amra dpc ingv flank project providing the funds for the publication fees

thrust fault mechanics and dynamics during a developmental stage of a foreland belt abstract studies of continental seismogenic zones indicate that deformation during an orogenic stage is episodic and spasmodic down to mid crustal depths and that seismic as well as aseismic modes of deformation need to be incorporated in quantitative theories of foreland belts such a theory is developed here it includes a method to help decipher the development of structures such as imbricate fans frontal ramps and ramp anticlines as illustrated for the hogsback frontal ramp and its ramp anticline in the kemmerer region of the wyoming salient the structure of the hogsback ramp is consistent with a shear fracture origin limit equilibrium mechanics indicate that shear failure would have proceeded incrementally possibly in response to recurring fault slip on the basal decollement contrasts in elastic constants and rock strength are critical e g current data indicate that shear failure development of the ramp would have begun 1 fourth fifth s distance down the ramp in competent madison carbonates if they compared in strength with the marianna limestone or 2 higher in the section if the madison compared in strength with the hasmark or blair dolostones whether the initial development of the ramp anticline involved seismic modes is not clear yet but elastic stiffness data indicate that subsequent imbrication of the anticline did involve seismic as well as aseismic modes of deformation

insights into fluid circulation across the pernicana fault mt etna italy and implications for flank instability article i nfo we conducted geophysical geochemical measurements on a 2k m n s profile cutting across the pernicana fault one of the most active tectonic features on the ne flank of mt etna the profile passes from the unstable e flank of the volcano to the south to the stable n flank and significant fluctuations in electrical resistivity self potential and soil gas emissions co2 rn and th are found the detailed multidisciplinary analysis reveals a complex interplay between the structural setting uprising hydrothermal fluids meteoric fluids percolating downwards ground permeability and surface topography in particular the recovered fluid circulation model highlights that the southern sector is heavily fractured and faulted allowing the formation of convective hydrothermal cells although the existence of a hydrothermal system in a volcanic area does not surprise these results have great implications in terms of flank dynamics at mt etna indeed the hydrothermal activity interacting with the pernicana fault activity could enhance the flank instability our approach should be further extended along the full extent of the boundary between the stable and unstable sectors of etna for a better evaluation of the geohazard in this active tectonic area

geometry and kinematics of the darjeeling sikkim himalaya india implications for the evolution of the himalayan fold thrust belt abstract the darjeeling sikkim himalaya lies in a zone where the convergence vector between the indian and eurasian plates is almost perpendicular to the himalayan deformation front current outcrop pattern preserves high grade hanging wall rocks of the main central thrust mct and the pelling thrust pt within 5 km of the mountain front u pb shrimp analysis on zircon grains from mct sheet record two 206pb 238u age groups of ca 2575 and ca 943 ma and from the pt 1835 13 ma the lesser himalayan duplex in the footwall of the mct is composed of two duplex systems a structurally higher hinterland dipping duplex and a lower duplex system that varies from hinterland dipping in the north to an antiformal stack in the middle and foreland dipping duplex in the south the foreland dipping horses and reactivation of the roof thrust resulted in large translation of the overlying mct and pelling thrust sheets the duplex also resulted in a plunge culmination forming a broad n s trending anticline a transport parallel restorable balanced cross section reveals a minimum shortening of 450 km 81 south of the south tibetan detachment system and an average long term shortening rate 20 mm yr although the study area lies in a zone of high convergence angle with the deformation front the surface structures do not record the greatest shortening of the orogen the shillong plateau and a tranverse zone lying southeast of the study area have accommodated a part of the convergence related shortening thereby under representing the shortening in the sikkim himalayan fold thrust belt lateral variations in the original width of the lesser himalayan basin may have played a role in partitioning the shortening in the fold thrust belt

the use of finite strain data in constructing a retrodeformable cross section of the meade thrust sheet southeastern idaho u s a abstract a method for drawing a balanced cross section is presented which uses the constraint of both the interpretation of the geometry and the analysis of the internal deformation within the meade thrust sheet southeastern idaho u s a earliest deformation associated with the meade thrust sheet is layer parallel shortening which is indicated by a spaced solution cleavage and deformed fossils in the jurassic twin creek formation this early layer parallel shortening fabric is rotated by folding in front of the main meade thrust sheet these folds are then truncated by the meade thrust locally finite strain markers indicate fault parallel shear

the relationship between degassing and ground deformation at soufriere hills volcano montserrat we examine the correlations between so2 emission rate seismicity and ground deformation in the month prior to the 25 june 1997 dome collapse of the soufriere hills volcano montserrat during this period the volcano exhibited a pattern of cyclic inflation and deflation with an 8 14 h period we find that so 2 emission rates measured by cospec correlate with the amplitude of these tilt cycles and that higher rates of so 2 emission were associated with stronger ground deformation and enhanced hybrid seismicity within tilt cycles degassing peaks coincide with maximum deformation gradients increases in the amount of gas in the magma conduit feeding the dome probably due to increases in volatile content of ascending magma volume can account for the observed increases in tilt amplitude hybrid seismicity and so2 emission rate q 2000 elsevier science b v all rights reserved

solution slip and separations on strike slip fault zones theory and application to the mattinata fault italy we present a set of relationships to determine the component of slip and separations generated by the cleavage controlled volume contraction in strike slip fault zones the fault walls can translate toward each other along the cleavage normal axis of maximum shortening as rock is dissolved by pressure solution along patterned cleavage surfaces within strike slip fault zones the fault zone shortening produces an apparent slip and possible separations of reference stratigraphic surfaces across the fault zone solution related slip and separations can differ in magnitude and have either the same or the opposite sense these discrepancies depend upon the amount of fault zone shortening and upon the angles between the fault and the shortening axis and between the fault and the reference stratigraphic surface separations can be considerable at any scales even for very low amounts of fault zone thinning apparent slip can be appreciable for large amounts of fault zone thinning and or high fault to cleavage incidence angles with the proper geometrical conversions the relationships here presented can apply to any fault type the application of this technique to the left lateral mattinata fault italy demonstrated that both left and right lateral strike separations can occur along the fault even for low amounts of fault zone contraction by rock dissolution q 2002 elsevier science ltd all rights reserved

near real time forecasting of lava flow hazards during the 12 13 january 2011 etna eruption we are grateful to eumetsat for seviri data to nasa for modis data and tonoaafor avhrr data the authors thank one anonymous reviewer and v acocella for their helpful and constructive comments this study was performed with the financial support from the v3 lava project ingv dpc 2007 2009 contract

stratigraphic uncertainty and errors in shortening from balanced sections in the north american cordillera shortening from balanced cross sections is typically cited as a minimum estimate because of the uncertainty in the position of eroded hanging wall cutoffs we show here using area balancing that the single most significant source of error is that associated with the shape and thickness of the initial stratigraphic wedge involved in the deformation new methods and software are introduced that in combination with freely available scans of virtually all geologic maps published by the u s geological survey usgs and geological survey of canada gsc allow one to make hundreds of map thickness measurements in just a few hours these methods are applied to geologic maps and cross sections from the western north american cordillera to determine the uncertainty of shortening in iconic cross sections by r a price and p r fermor and by f royse one sigma stratigraphic thickness uncertainty measured in homoclinal dip packages of prominent paleozoic units within single thrust plates and single quadrangles ranges from 20 to 30 of average thickness in the costigan and sulfur mountain plates in southern canada and can be as high as 37 in the darby and absaroka plates of the idaho wyoming united states thrust belt assuming that all individual paleozoic units in the cross sections have similar errors the entire paleozoic section used in the area balancing would have 8 11 uncertainty assuming a normal or gaussian distribution because the stratigraphic wedges in southern canada and idaho wyoming do not have a uniform original taper our basic area balance underestimates shortening by balancing the non uniform taper back to a uniform taper we can account for this discrepancy total shortening determined in this way is 104 17 km which is identical to that obtained by price and fermor the idaho wyoming section of royse with maps by the usgs yields similarly large errors in shortening magnitude 56 10 km for the three frontal thrust faults of those errors uncertainty in the shape and thickness of the initial stratigraphic wedge accounts for 56 and 70 of the total in southern canada and western wyoming respectively eroded hanging wall cutoffs account for just 15 in both areas with the remainder coming from uncertainty in the subsurface geometry including the position of the decollement

strain variation in thrust sheets across the sevier fold and thrust belt idaho utah wyoming implications for section restoration and wedge taper evolution abstract although strain in fold and thrust belts is typically inhomogeneous on the largest scale strain within thrust sheets shows regular patterns the strain which is a quantitative measure of the deformation of any thrust sheet is independent of the translation of the sheet the internal deformation can be represented by a deformation profile the change in shape during thrusting of a fault perpendicular line which can then be used to unstrain the sheet during restoration in cross section balancing deformation profiles in well studied thrust sheets show regular geometric patterns and compatibility constraints can be used to minimize the data needed to define the profiles in other sheets from the geometry of deformation profiles and direct field observations the most important component of internal deformation of thrust sheets in many fold and thrust belts is early layer parallel shortening lps this can be removed in a straightforward manner during restoration and significantly affects the geometry i e taper of the restored section original basin wedge taper may have important implications for the mechanical evolution of fold and thrust belts thus changes in original basin taper resulting from strain removal may affect significantly the way in which we interpret the evolution of a fold and thrust belt in an area

detecting imminent eruptive activity at mt etna italy in 2007 2008 through pattern classification of volcanic tremor data abstract volcano monitoring aims at the recognition of changes in instrumentally observable parameters before hazardous activity in order to alert governmental authorities among these parameters seismic data in general and volcanic tremor in particular play a key role recent major explosive eruptions such as okmok aleutians and chaiten chile in 2008 and numerous smaller events at mt etna italy have shown that the period of premonitory seismic activity can be short only a few hours which entails the necessity of effective automatic data processing near on line here we present a synoptic pattern classification analysis based on self organizing maps and fuzzy cluster analysis which is applied to volcanic tremor data recorded during a series of paroxysmal eruptive episodes and a flank eruption at etna in 2007 2008 in total eight episodes were analyzed in six of these significant changes in the dynamic regime of the volcano were detected up to 9 h prior to the onset of eruptive activity and long before changes in volcanic tremor amplitude and spectral content became evident in classical analysis in two cases the state transition was

integration of palaeomagnetic data basement cover relationships and theoretical calculations to characterize the obliquity of the altomira loranca structures central spain this work was funded by the project kinesal cgl2010 21968 c02 02 of the spanish ministry of economy and competitiveness and a phd igme grant for the first author it is a contribution of the geomodels research institute and the grup de recerca de geodinamica i analisi de conques 2014sgr467 supported by the agencia de gestio d ajuts universitaris i de recerca and the secretaria d universitats i recerca del departament d economia i coneixement de la generalitat de catalunya

quantifying vertical axis rotation in curved orogens correlating multiple data sets with a refined weighted least squares strike test 1 map scale curvature is a fundamental feature of most contractional orogenic belts and is central to understanding the kinematic and dynamic evolution of mountain systems paleomagnetic analysis combined with detailed structural studies is the most robust means of quantifying vertical axis rotations that produce curvature over a range of temporal and spatial scales this paper explores how vertical axis rotations can best be evaluated for multiple data sets by applying a weighted least squares method to the classic strike test this refined method provides measures of best fit slope confidence interval and goodness of fit between map scale structural trend paleomagnetic rotations and deformation fabric orientations structural trend is estimated by averaging fold axial trace formation contact and bed strike data over kilometer scale areas paleomagnetic and deformation fabric site mean orientations and measurement uncertainties are estimated using vector and bootstrap statistics weighting factors are estimated from combined measurement uncertainty structural noise related to small scale block rotation and stress strain refraction and variations in restoration paths the number of sites needed to obtain a significant confidence interval in strike test slope is a function of combined uncertainty in paleomagnetic or deformation fabric directions and the total range in structural trend around a curved orogen improved estimates of strike test slope and rotation thus require systematic sampling with a wide distribution of sites evaluation of appropriate weighting factors and statistical analysis a case study is presented that highlights application of this refined method to paleomagnetic and deformation fabric data sets from the wyoming salient of the sevier thrust belt paleomagnetic data yield a strike test slope of 0 76 0 11 indicating that the wyoming salient is a progressive arc with 3 4 secondary curvature related to vertical axis rotation synchronous with large scale thrusting and 1 4 initial curvature finite strain anisotropy of magnetic susceptibility and mesoscopic structural orientations which are related to early layer parallel shortening all yield strike test slopes of 0 9 0 1 comparing these slopes with paleomagnetic results indicates that deformation fabrics had initial curvature and thus cannot be used alone to accurately estimate rotations by integrating systematic paleomagnetic and structural data using statistical analysis curvature models for the wyoming salient are closely constrained

thrust loads and foreland basin evolution cretaceous western united states two dimensional modeling of loading during the formation of the idaho wyoming thrust belt shows that regional isostatic compensation by flexure of an elastic lithosphere is sufficient to control the formation of a foreland basin the flexural rigidity of the lithosphere is inferred to have been approximately 1023 nm 1030 dyne cm on the basis of palinspastic comparison of predicted downwarping due to the thrust plate loads to the shape of the sedimentary wedge on the west side of the cretaceous western interior seaway erosion of part of the uplifted thrust plates redistributed the load depositing it farther to the east thereby causing subsidence over a much wider area than could have been accomplished only by the loading by thrust plates paleotopography after major cretaceous thrust events was calculated the resulting mountainous terrain gentle alluvial plain and flat sea floor correspond well with the topography of the modern foreland thrust belt and basin system in the andes of south america and to paleogeographic reconstructions in the western united states thrust belt topography is controlled by the subsurface geometry of the thrust faults particularly the positions of ramp zones and by isostatic subsidence

a review of deformation pattern templates in foreland basin systems and fold and thrust belts implications for the state of stress in the frontal regions of thrust wedges aesthetically appealing thrust systems and related large scale anticlines in both active and fossil foreland fold and thrust belts and the economic potential associated with the m have captured the interest of structural geologists for many decades as a consequence a large amount of data on sub seismic deformation patterns from thrust related an ticlines is available in the literature we provide a review of deformation pattern templates from fi eld data in foreland fold and thrust belts and show that the most frequent tre nds of sub seismic syn orogenic deformation structures hosted in km scale thrust related folds frequently and pa radoxically indicate a syn th rusting strike slip stress fi eld con fi guration with a near vertical 2 and a sub horizontal 3 rather than a contractional one where the latter is expected to be the vertical principal axis of the stress ellipsoid this a pparent inconsistency between sub seismic syn orogenic deformation structures and stress fi eld orientation is here named the 2 paradox field data support a possible expla nation of the paradox provided by the major role played by i nherited early orogenic extensional deformation struc tures on thrust fault nucleation nucleation of major thru sts and their propagation is facilitated and driven by the positive inversion and linkage of the early orogenic sub s eismic extensional inheritance developed in the foreland basin this process eventually leads to the development of l argereversefaultzonesandcanoccurbothincontractional and strike slip stress fi eld con fi gurations

three years of so2 flux measurements of mt etna using an automated uv scanner array comparison with conventional traverses and uncertainties in flux retrieval 1 sviluppo di sistemi di monitoraggio dipartimento di protezione civile della regione sicilia 2 ingv istituto nazionale di geofisica e vulcanologia sezione di catania italy 3 novac network for observation of volcanic and atmospheric change eu funded sixth framework programme project 18354 4 uk nerc national centre for earth observation via the dynamic earth and geo hazards

polykinematic foreland basins initiated during orthogonal convergence and terminated by orogen oblique strike slip faulting an example from the northeastern variscan belt abstract an extensive early carboniferous foreland basin the moravosilesian culm basin mscb delineates the northeastern margin of the bohemian massif variscan orogenic belt the basin overlays a complex suture between the outer brunovistulia microplate forming a promontory previously accreted to laurussia and inner gondwana derived units that form the remainder of the bohemian massif our structural paleomagnetic and magnetic anisotropy data from the eastern portion of the mscb indicate that its depositional architecture internal fabric and deformation by folding and faulting record a major switch from orthogonal convergence to orogen oblique strike slip shearing first the brunovistulia microcontinent was subducted frontally towards w during 346 335 ma followed by a shift of the subduction vector towards ssw at around 335 330 ma from 330 ma onwards the underthrusting had ceased and the wnw ese dextral elbe shear zone related to the westward movement of gondwana with respect to laurussia controlled deformation of this region displacement of the northerly eastern sudetes block towards ese produced regional wnw ese pure shear shortening against the brunovistulia indentor and resulted in an overall doubly vergent structure of the mscb simultaneously the southerly moldanubian unit was translated towards wnw away from the brunovistulian microplate and likely contributed to an extensional regime related to orogenic collapse progressing outward from the internal domains of the bohemian massif on a larger scale we suggest that the mscb is an illustrative example of a polykinematic foreland basin where deposition syn to post sedimentary deformation and thus geodynamic processes changed significantly during basin evolution starting off with microplate impingement into a continental margin reentrant and terminated by strike slip shearing our data also do not support previous models for the tectonic development of the northeastern termination of the variscan belt which suggested either a large magnitude vertical axis oroclinal rotation of the foreland or its translation along an orogen perpendicular strike slip fault

kinematics around a large scale oblique ramp southern pyrenees spain the gavarnie thrust sheet of the southern pyrenees is bound to the east and west by 40 km long transverse zones producing a rectilinear thrust sheet within the boltana region the northwest corner of the gavarnie thrust sheet is well exposed the locale is used to characterize the strain and kinematic patterns and detailed geometry of an oblique ramp over a variety of scales the hanging wall of the gavarnie thrust fault in the area was transported toward 200 and contains two regional scale north south trending anticlines in the vicinity of the oblique ramp the strike of the gavarnie thrust fault and the trend of hanging wall fold axes are 0 180 the magnitude of shortening accommodated by regional scale fold and fault development is constant at 25 along the length of the ramp the orientation of instantaneous and finite shortening axes on meso and grain scales was inferred from the attitudes of cleavage mesoscale folds and faults carbonate mechanical twins and the geometry of finite strain finite and instantaneous shortening axes are subhorizontal and remain perpendicular to the gavarnie thrust ramp within a 10 km wide zone in the footwall and a 20 km wide zone in the hanging wall outside of the halo of footwall and hanging wall ramp deformation the principal shortening directions consistently trend 200 parallel to thrust transport directions throughout the south pyrenean thrust belt the parallelism of instantaneous and finite principal strain axes suggests that grain scale deformation was rionrotational total shortening measured within the footwall of the gavarnie thrust fault decreases from 60 adjacent to the thrust ramp to 10 approximately 10 km away from the ramp while principal shortening directions determined over scales ranging from millimeters to kilometers show a consistent pattern in the boltana region they differ by as much as 90 from tectonic convergence directions between iberia and eurasia during the alpine orogeny 80 18 ma determined from magnetic anomaly patterns in the central atlantic and bay of biscay divergence between plate convergence directions and alpine south pyrenean shortening directions suggests that 200 km of nw se convergence was apparently partitioned into the north and south pyrenean thrust zones which were shortened 167 km the iberian range which accomodated 30 km of shortening 10 km of shortening accomodated in the catalan coastal range and 100 km of right lateral strike slip accomodated within the internides

porphyroblast microstructures a review of current and future trends many recent papers show how porphyroblast microstructures play an important role in a wide range of structural and metamorphic studies this paper reviews ten current applications of these microstructures 1 porphyroblast growth timing criteria 2 tracking progressive foliation development relative to changing metamorphic conditions 3 timing of pluton emplacement relative to deformation and metamorphism 4 finite longitudinal strain determinations 5 kinematics and porphyroblast rotation 6 use of linear fabrics preserved in porphyroblasts 7 porphyroblasts and folding mechanisms 8 inclusion trail orientations and orogenic processes 9 inferring shear strain rates from porphyroblast growth rates and 10 in situ age determinations although there is still no concensus on the interpretation of some porphyroblast microstructures a bright future lies ahead as traditional and newly developed techniques of microstructural analysis are combined with modern chemical and microprobe techniques to provide an increased understanding of the relationships between deformation and metamorphism in a wide range of metamorphic settings

reconstructing the kinematic evolution of curved mountain belts a paleomagnetic study of triassic red beds from the wyoming salient sevier thrust belt u s a determining the kinematic history and mechanics of curved fold and thrust belts is fundamental to understanding the tectonic evolution of mountain systems to better understand the development of a classic curved fold and thrust belt we completed an integrated paleomagnetic and strain study of the wyoming salient paleomagnetic data are reported here from 154 sites collected from red beds of the triassic ankareh formation in the salient and nine sites collected from the relatively stable foreland red beds display three components with distinctly different magnetic behaviors 1 a near primary triassic magnetization carried by hematite that is stable up to 680 c tr component 91 sites 2 a cretaceous chemical remagnetization carried partly by magnetite k component 32 sites and 3 a recent viscous magnetization that is mostly removed by 350 c site mean vectors for the tr and k components show a high degree of scatter from expected triassic and cretaceous reference directions suggesting significant tilt and rotation subsequent to magnetization acquisition restoration of tilt and folding for individual site means results in well clustered shallow and moderate inclinations for the tr and k components respectively and in variable declinations related to systematic vertical axis rotations statistical analysis of declinations for both components indicates that 75 of present day salient curvature resulted from secondary rotation and 25 of primary curvature was likely related to sedimentary basin architecture analysis of individual thrust systems indicates a slightly greater component of rotation in more internal sheets 80 compared to the frontal thrust sheets 65 suggesting that rotations were concentrated near the leading edge of the propagating fold and thrust wedge with only minor additional rotation of internal sheets transfer zones oblique ramps and more deformed overturned fold limbs display locally more complex patterns which can be understood through careful structural analysis when combined with internal strain data and regional structural relations paleomagnetic data support a kinematic model of a progressive arc with curved thrust slip paths and differential shortening that rotated early layer parallel shortening fabrics and produced minor strike parallel extension this kinematic history likely reflects a combination of processes including greater initial stratigraphic thickness and subsequent shortening and wedge propagation in the central part of the salient presence of a weak basal detachment and fault zone weakening that favored lower taper and buttressing by laramide foreland uplifts that formed along basement promontories at the north and south ends of the salient

near orthogonal foliation development in orogens meaningless complexity or reflection of fundamental dynamic processes abstract orogenic belts are geometrically complex owing to repeated deformation within this complexity there is evidence that may suggest a common pattern of sequential steeply dipping and gently dipping foliations seven possible explanations are presented for the sequential development of these foliations which can probably be reduced to four of general importance 1 the passage of thrust sheets over flats and ramps 2 switching of the maximum and minimum compressive stress orientations during orogenesis 3 reversal of structural development owing to strong rheological anisotropy and 4 back rotation of crenulation hinges during crenulation cleavage development it is suggested that all four of these reflect fundamental dynamic processes at work to build an orogen and therefore that sequentially overprinted steeply and gently dipping foliations also reflect such fundamental processes this illustrates that detailed geometrical analysis at the meso and microscales can provide valuable input to dynamic models of orogenesis

ramifications of four dimensional progressive deformation in contractional mountain belts abstract studies of progressive deformation aim to identify and establish temporal sequences of structural stages each characterized by a suite of structures which form under specific rock and environmental conditions because of the natural spatial variation in rock type and environmental parameters in an orogen several structural stages may operate concurrently in different parts of an orogenic wedge at any given instant in time rocks experiencing different stages of deformation are bounded by deformation fronts as intrinsic and extrinsic conditions of deformation vary through time spatial migration of deformation fronts causes rocks to record temporal overprinting of structural stages in convergent orogens deformation fronts as mapped in their finite state are typically forelandward dipping due to the regional orogenic wedge geometry and thermal structure depending on the competing deformation processes deformation rate changes on either side of the front may cause deformation fronts to change orientation relief and surface area with time differences in migration rates of different deformation fronts could cause rearrangement of the sequence of structural stages with depth and laterally across the same mountain belt

predicting pore pressure in active fold thrust systems an empirical model for the deepwater sabah foldbelt abstract measurements related to mudrock shale and siltstone porosity such as acoustic velocity density or electrical resistivity have traditionally been used to predict pore pressures in extensional stress settings the underlying assumption is that burial and vertical effective stress ves which is the overburden minus the pore pressure controls the compaction of these rocks through porosity loss the dataset presented here compares ves and acoustic velocity of similar composition mudrocks in both an extensional and a compressional stress setting in the extensional stress environment the mudrocks follow a typical compaction trend with a porosity loss and increase in acoustic velocity that can be related to ves in an active fold thrust belt the compressive stresses further reduce the porosity and increase the acoustic velocity of the mudrocks first a layer parallel shortening compacts sediments beyond what is observed for the ves this additional compaction is further enhanced near thrust faults and in anticlinal forelimbs presumably due to additional shear stress in these areas the mudrocks located in folds that are buried by additional sedimentation do not compact again until the tectonic compaction is overridden by enough new burial after that the mudrocks follow the observed extensional setting compaction trend in the fold thrust belt the observed reduction in porosity by stresses other than burial leads to an under prediction of pore pressure using traditional methods to account for this we present a correction that can be applied to the acoustic velocity or porosity using two parameters a proximity to thrust faults and anticlinal forelimbs and b the amount of burial after fold formation with these corrections the extensional velocity ves compaction trend can be used to accurately predict pore pressure within the active fold thrust belt the correction is calibrated with well data and is empirical none the less it is a first step toward understanding the magnitudes of the compressive lateral stresses involved in generating the observed porosity loss within the fold thrust belt

a model of foreshock occurrence summary we have constructed a model for the occurrence of foreshocks and foreshock sequences the foreshocks as well as the main shock are assumed to occur because of the abrupt coalescence of pre existing cracks coalescence occurs if the stress intensity factors at the crack tips exceed a certain critical value in the sub critical state each crack undergoes accelerated extension quasi statically due to stress corrosion until it reaches the critical state at which point growth becomes catastrophic the rate of foreshock occurrence increases as the time of the main shock approaches and is described by a power law function of time the exponent in the power law is independent of the distributions of crack sizes spacings and fracture strengths this universality implies that foreshock patterns should be useful identifiers for the prediction of the occurrence times of large earthquakes however we find that there is considerable diversity in the patterns of energy release nevertheless there is some hope that the magnitudes of large earthquakes can be predicted from the magnitudes of the events in the foreshock sequences if one has a priori information describing the distributions of barrier strengths and geometries

shallow magma pathway geometry at mt etna volcano 1 a fundamental goal of volcano seismology is to understand the dynamics of active magmatic systems in order to assess eruptive behavior and the associated hazard imaging of magma conduits quantification of magma transport and investigation of long period seismic sources together with their temporal variations are crucial for the comprehension of eruption triggering mechanisms at mt etna volcano several intense episodes of tremor activity were recorded during 2007 in association with strombolian activity and or intense fire fountaining episodes occurring from the south east crater sec the locations of the tremor sources and of the long period seismic events are used here to constrain both the area and the depth range of magma degassing highlighting the geometry of the shallow conduits feeding sec the imaged conduits consist of two connected resonating dike like bodies nnw sse and nw se oriented extending from sea level to the surface in addition we show how tremor long period lp and very long period vlp event locations and signatures reflect pressure fluctuations in the plumbing system associated with the ascent discharge of gas rich magma linked to the lava fountains the evidence here reported also corroborated by ground deformation variations can help develop a better prediction and early warning system for those eruptions effusive or explosive that apparently manifest no clear precursors

roof sequence response to emplacement of the wills mountain duplex the roles of forethrusting and scales of deformation abstract this paper focuses on the behavior of a roof sequence in the appalachian plateau of west virginia u s a and emplacement of the wills mountain duplex with 17 5 km of displacement unlike the plateau along strike in pennsylvania and new york where forethrusting was previously documented this roof sequence lacks an underlying salt dominated roof decollement kinematic analyses reveal that the roof sequence in the west virginian plateau accommodated about two thirds of the 17 5 km of shortening by the adjacent wills mountain duplex as a forethrusting kinematic response the remaining shortening imbalance of about 5 km between the duplexes and younger roof sequence rocks is accommodated by additional forethrusting further into the foreland and local compensation this kinematic response matches that along strike in the central appalachians despite the loss of the salt decollement we interpret that an ordovician shale dominated formation was sufficiently weak to substitute for the salt horizon thus a weak mechanical unit rather than specifically a salt decollement is a necessary prerequisite for forethrusting a contributing factor to forethrusting may be the subvertical front of the wills mountain duplex which inhibited other responses by the roof sequence mesoscale and smaller processes including grain to grain pressure solution twinning and cleavage formation account for over 75 of the shortening in the roof sequence and if ignored would result in an erroneous interpretation of backthrusting or local compensation this result suggests that failure to consider all deformation scales could lead to incorrect kinematic conclusions in other tectonic systems

kinematic history of the meade thrust based on provenance of the bechler conglomerate at red mountain idaho sevier thrust belt with up to 45 km of slip the meade thrust fault in southeastern idaho is one of the major thrusts in the sevier thrust belt yet its age of displacement has remained enigmatic because of the lack of a derivative synorogenic deposit we propose that the synorogenic conglomerate produced by initial meade thrusting crops out on red mountain in southeastern idaho 1 5 km east of the present trace of the meade thrust this conglomerate historically has been considered part of the ephraim formation of the lower cretaceous gannett group but we suggest that it is a conglomeratic facies of the bechler formation localized to the area of red mountain regional stratigraphic considerations and paleontological dates from underlying and overlying strata indicate that the bechler conglomerate facies bcf is aptian in age the bcf is 850 m thick and consists of pebble to boulder conglomerate sandstone and mudrock deposited by fluvial and mass flow processes on medial to distal parts of an alluvial fan paleocurrent data indicate an eastward fan shaped dispersal pattern the bcf contains clasts of micritic limestone chert pebble conglomerate and cherty litharenite that were derived from the ephraim formation in addition the conglomerate contains abundant clasts of ordovician carboniferous and lower mesozoic rocks that crop out on both the meade thrust sheet and the paris thrust sheet 25 30 km to the west the base of the bcf is marked by a local 27 angular unconformity on top of the ephraim formation the bcf contains intraformational progressively rotated angular unconformities internal growth folds and minor dip discontinuities that were produced by simultaneous folding and sediment accumulation on the proximal footwall of the meade thrust provenance modeling indicates that the bcf was derived from mesozoic strata that were exposed along the frontal part of the meade thrust sheet and from paleozoic strata that were coevally exposed in the hindward located paris thrust sheet topography on the paris sheet was rejuvenated as it was carried passively over a major ramp in the meade thrust provenance and structural data are combined to produce an incremental bulk rock retrodeformation of initial meade displacement clasts of jurassic twin creek limestone with pressure solution cleavage in the lower part of the bcf indicate that an episode of layer parallel shortening occurred in the meade hanging wall prior to meade displacement this may have been related to emplacement of the paris thrust sheet the bcf recorded 6 km of initial meade related shortening by thrust slip and fault propagation folding during aptian time illite crystallinity systematic fracture sets in the ephraim formation and bcf finite strain in meade footwall and hanging wall rocks and thermal models by previous workers indicate that the meade thrust sheet ultimately overrode the bcf and other footwall rocks probably during albian cenomanian time the bcf and the meade thrust were folded during slip on thrust faults related to the northern crawford thrust during coniacian time a revised interpretation of gannett group provenance throughout the thrust belt suggests that the ephraim formation was derived from both the paris thrust sheet and an older hindward located thrust sheet the bechler was derived from the meade and paris sheets

source of anomalous magnetization in area of hydrocarbon potential petrologic evidence from jurassic preuss sandstone wyoming idaho thrust belt the jurassic preuss sandstone which crops out in the central part of the wyoming idaho thrust belt on trend with a hydrocarbon producing region to the south has been previously identified as the source of anomalous magnetization in the area elsewhere anomalous magnetization in sedimentary rocks near hydrocarbon accumulations has been attributed to hydrocarbon engendered magnetic minerals but magnetization of the preuss is controlled by detrital magnetite evidence of a detrital origin for magnetite includes 1 concentration of magnetite grains along laminations containing other heavy minerals 2 the presence of exsolved ilmenite hematite and spinel in the magnetite grains and 3 titanium contents typical of igneous derived magnetite that detrital magnetite is responsible for the anomalous magnetization in the preuss is further indicated by the systematic eastward decrease in magnetite abundance corresponding to a similar eastward decrease in magnetic susceptibility and remanent magnetization of the unit petrologic and vitrinite reflectance studies indicate a complex low temperature 150 c or 302 f diagenetic history for the preuss nevertheless preservation of detrital magnetite the presence of diagenetically early ferric oxide minerals and the absence of sulfide minerals all indicate that the preuss has not experienced sulfidic reducing conditions common in areas of hydrocarbon seepage the marine carbon isotopic composition of calcite that cements most preuss sandstones dgr13c values ranging from 2 47 to 1 48 pmil is evidence that carbonate diagenesis also was not influenced by hydrocarbons the results of this multidisciplinary study of the preuss underscore the importance of similar studies when evaluating the sources of aeromagnetic anomalies in areas of hydrocarbon potential

measuring volcanic degassing of so2 in the lower troposphere with aster band ratios we present a new method for measuring so2 with the data from the aster advanced spaceborne thermal emission and reflectance radiometer orbital sensor the method consists of adjusting the so2 column amount until the ratios of radiance simulated on several aster bands match the observations we present a sensitivity analysis for this method and two case studies the sensitivity analysis shows that the selected band ratios depend much less on atmospheric humidity sulfate aerosols surface altitude and emissivity than the raw radiances measurements with 25 relative precision are achieved but only when the thermal contrast between the plume and the underlying surface is higher than 10 k for the case studies we focused on miyakejima and etna two volcanoes where so2 is measured regularly by cospec or scanning doas the so2 fluxes computed from a series of ten images of miyakejima over the period 2000 2002 is in agreement with the long term trend of measurement for this volcano on etna we compared so2 column amounts measured by aster with those acquired simultaneously by ground based automated scanning doas the column amounts compare quite well providing a more rigorous validation of the method the so2 maps retrieved with aster can provide quantitative insights into the 2d structure of non eruptive volcanic plumes their dispersion and their progressive depletion in so2

patterns in the recent 2007 2008 activity of mount etna volcano investigated by integrated geophysical and geochemical observations 1 seismic deformation and volcanic gas observations offer independent and complementary information on the activity state and dynamics of quiescent and eruptive volcanoes and thus all contribute to volcanic risk assessment in spite of their wide use there have been only a few efforts to systematically integrate and compare the results of these different monitoring techniques here we combine seismic volcanic tremor and long period seismicity deformation gps and geochemical volcanic gas plume co2 so2 ratios measurements in an attempt to interpret trends in the recent 2007 2008 activity of etna volcano we show that each eruptive episode occurring at the southeast crater sec was preceded by a cyclic phase of increase decrease of plume co2 so2 ratios and by inflation of the volcano s summit captured by the gps network these observations are interpreted as reflecting the persistent supply of co2 rich gas bubbles and eventually more primitive magmas to a shallow depth of 1 2 8 km asl magma storage zone below the volcano s central craters ccs overpressuring of the resident magma stored in the upper ccs conduit triggers further magma ascent and finally eruption at sec a process which we capture as an abrupt increase in tremor amplitude an upward 2800 m asl and eastward migration of the source location of seismic tremor and a rapid contraction of the volcano s summit resumption of volcanic activity at sec was also systematically anticipated by declining plume co2 so2 ratios consistent with magma degassing being diverted from the central conduit area toward sec

early foreland deformation of the fuegian andes argentina constraints from the strain analysis of upper cretaceous danian sedimentary rocks abstract this contribution addresses new structural data from upper cretaceous danian sedimentary rocks of the fuegian andes orogenic front in argentina the structures studied called d were formed during the early foreland deformation of the orogen in the late cretaceous danian in times when south america and antarctica were still connected the strain analysis of these structures indicates that deformation occurred at upper crustal depths and was characterized by flexural folding accompanied by formation of pressure solution tectonic foliations in zones of higher strain deformation intensities increase toward the hinterland and with depth the history of deformation involved progression from layer parallel shortening to folding above a detachment and further formation of a forward propagating thrust wedge layer parallel shortening and incipient folding recorded in maastrichtian danian rocks indicate the leading edge of d deformation non coaxial finite strain orientations were involved during formation of d structures along the fuegian andes front these finite strain orientations cannot be explained with the sw ne regional contraction usually assumed to have driven andean deformation in this region alternatively we consider that n s contraction combined with buttressing against the cratonic foreland comprise a more suitable interpretation for d and younger deformation

layer parallel shortening across the sevier fold thrust belt and laramide foreland of wyoming spatial and temporal evolution of a complex geodynamic system abstract varying patterns of layer parallel shortening lps and vertical axis rotations from the thin skin sevier fold thrust belt to the thick skin laramide foreland of wyoming are quantified from integrated structural anisotropy of magnetic susceptibility ams and paleomagnetic analyses within the sevier belt widespread early lps was accommodated by spaced cleavage fracture sets minor folds and minor faults lps directions are subperpendicular to structural trends of systematically curved thrust sheets of the wyoming salient reflecting a combination of primary dispersion and secondary rotation during thrusting within the laramide foreland limited lps was accommodated mostly by minor faults with conjugate wedge and strike slip geometries lps directions in gentler fold limbs vary from perpendicular to acute with structural trends of variably oriented anastomosing basement cored arches steep forelimbs display more complex relations including younger fault sets that developed during evolving stress states and localized vertical axis rotations although internal strain is limited weak ams lineations defined by kinked and rotated phyllosilicates are widely developed and consistently oriented perpendicular to measured lps directions palinspastically restored lps directions corrected for paleomagnetically determined vertical axis rotations vary on average from w e in the sevier belt to wsw ene in the laramide foreland in detail lps directions display deflections related to primary sedimentary wedge geometry and basement fabrics lps in the sevier belt is interpreted to partly reflect stress transmitted from the hinterland through the growing orogenic wedge and topographic stress along the front of the wedge lps in the laramide foreland is interpreted to partly reflect basal traction during flat slab subduction beneath thick cratonic lithosphere with spatial temporal variations in stress trajectories related to basement heterogeneities and evolving fault systems evidence for significant late n s laramide shortening as proposed by multi stage shortening models is not observed

insights into magma and fluid transfer at mount etna by a multiparametric approach a model of the events leading to the 2011 eruptive cycle 1 since the second half of the 1990s the eruptive activity of mount etna has provided evidence that both explosive and effusive eruptions display periodic variations in discharge and eruption style in this work a multiparametric approach consisting of comparing volcanological geophysical and geochemical data was applied to explore the volcano s dynamics during 2009 2011 in particular temporal and or spatial variations of seismicity volcano tectonic earthquakes volcanic tremor and long period and very long period events ground deformation gps and tiltmeter data and geochemistry so2 flux co2 flux co2 so2 ratio were studied to understand the volcanic activity as well as to investigate magma movement in both deep and shallow portions of the plumbing system feeding the 2011 eruptive period after the volcano deflation accompanying the onset of the 2008 2009 eruption a new recharging phase began in august 2008 this new volcanic cycle evolved from an initial recharge phase of the intermediate shallower plumbing system and inflation followed by i accelerated displacement in the volcano s eastern flank since april 2009 and ii renewal of summit volcanic activity during the second half of 2010 culminating in 2011 in a cyclic eruptive behavior with 18 lava fountains from new southeast crater nsec furthermore supported by the geochemical data the inversion of ground deformation gps data and the locations of the tremor sources are used here to constrain both the area and the depth range of magma degassing allowing reconstructing the intermediate and shallow storage zones feeding the 2011 cyclic fountaining nsec activity

high spatial resolution radon measurements reveal hidden active faults on mt etna radon emissions are frequently monitored in volcanically and tectonically active areas in order to reveal changes in soil degassing as radon acts a tracer for the more abundant co2 degassing commonly observed in such areas between july 2002 and may 2003 a series of discrete measurements of radon concentrations in soil were made with high spatial resolution similar to5 100 m in the santa venerina area on mt etna these measurements revealed well defined linear anomalies that we interpret as being caused by active faults whose higher porosity than surrounding soils allows an increased co2 flux carrying radon from beneath these faults were not visible at the surface and were therefore revealed at high spatial resolution by our radon survey our hypothesis that the positive anomalies are attributable to active faults was strengthened by the observation of concentrated damage along this geometry during the earthquakes that struck this area in late october 2003

a comparison of the effectiveness of clast based finite strain analysis techniques to ams in sandstones from the sevier thrust belt wyoming abstract geological strain analysis of sedimentary rocks is commonly carried out using clast based techniques which rely on assumptions regarding clast shapes and orientations as well as distances between clast centres to evaluate the accuracy of these methods in low strain regimes we have compared strain analysis estimates to the anisotropy of magnetic susceptibility ams in sandstone samples from the wyoming salient the cordilleran mountain belt of north america is one of the world s classic foreland fold and thrust belts the sevier belt represents the thin skinned front of this orogenic event characterized by thrust faults and folds that shortened and translated sequences of devonian to cretaceous strata eastward deformation increases westward providing an ideal laboratory and geological setting to explore the potential correlation of anisotropy of magnetic susceptibility ams to clast based strain analyses studies attempting to define the relationship between ams and finite strain have been in vogue since the link between layer parallel shortening and ams was first established this relationship despite proven strong correlations between the ams tensors and tectonic directions is generally complicated by competing sub fabrics as well as the various magnetic anisotropy properties of the minerals contributing to the ams fabric even with these complications we conclude that ams is much more sensitive to incipient tectonic fabrics than clast based methods