carbonate platform crisis in the carnian late triassic of hanwang sichuan basin south china insights from conodonts and stable isotope data abstract during the carnian the hanwang area in the northwestern sichuan basin south china was characterized by shallow water carbonate sedimentation that underwent an abrupt demise associated to a sudden input of terrigenous sediments this major facies change was considered to be the expression of the onset of the carnian humid episode a most remarkable environmental crisis in late triassic that is well recognized in northwestern tethys margins and coincides with a major global perturbation of the carbon stable isotope record however the lack of detailed biostratigraphic constraints have so far prevented a precise dating of the carbonate platform demise in western sichuan basin in this work the qingyan gou hwq section cropping out in hanwang was investigated for its facies and microfacies carbonate carbon and oxygen isotopes on brachiopods microbial grains and bulk matrix facies analysis shows a marine transgression from inner ramp oolitic shoal to middle ramp siliceous sponge mound then overlain by shale and calcareous siltstone with interbedded silty mudstones refined biostratigraphic data from hwq and guanyin ya hwg sections imply that the demise of sponge mounds occur in the late tuvalian or later a negative carbon isotope perturbation was found in the bulk matrix immediately below the sponge mounds demise but it was not found on the isotope record from brachiopods this suggests that the negative shift in the bulk carbonate was probably related to diagenesis given the late tuvalian last substage of carnian age attributed to the demise of the sponge mounds and the absence of a carbon isotopic excursion we infer that the carbonate platform crisis and strong terrigenous input in hanwang cannot be related to the onset of the carnian humid episode these the demise of the carbonate platform and the facies deepening trend could be rather due to the interplay between accelerating subsidence rates environmental chants and enhanced siliciclastic input related to the formation of a foreland basin during indosinian orogenesis

carnian norian biomagnetostratigraphy at silicka brezova slovakia correlation to other tethyan sections and to the newark basin correlations of upper triassic magnetic stratigraphies from tethyan sections have been hampered by difficulties with conodont biostratigraphy and taxonomy and discontinuous sedimentation particularly in the hallstatt limestones of turkey and austria the magnetic stratigraphy and conodont biostratigraphy from the upper carnian to upper norian limestones exposed at silickabrezova slovakia can be correlated to other tethyan sections and to the continental succession in the newark basin the resulting correlations help to resolve some of the apparent discrepancies in existing conodont zonations and result in a revised correlation to north american terrestrial vertebrate and palynological zones the correlations imply that the norian rhaetian boundary lies within newark polarity zone e17r at v207 ma the carnian norian boundary lies close to the base of newark polarity zone e7r at v226 ma this implies durations for the norian and rhaetian stages of 19 myr and 7 myr respectively 2002 elsevier science b v all rights reserved

the schilfsandstein and its flora arguments for a humid mid carnian episode recently intensified research on the mid carnian episode stimulated discussions about the mid carnian climate and a supposed humid climate shift this basin scale study on the schilfsandstein the type example of the mid carnian episode applied sedimentological palynological and palaeobotanical proxies of the palaeoclimate to a large dataset of cored wells and outcrops the results demonstrate the primary control of circum tethyan eustatic cycles on the central european basin where transgressions contributed to basin scale facies shifts the palaeoclimate proxies point to a uniform arid to semi arid carnian climate with low chemical weathering and high evaporation consequently transgressions into the central european basin led to increased evaporation forcing the hydrological cycle the increased runoff from source areas resulted in high groundwater stages on lowlands characterized by hydromorphic palaeosols and intrazonal vegetation with hygrophytic elements during lowstands reduced evaporation and runoff led to increased drainage and desiccation of lowlands characterized by formation of vertisols calcisols and gypsisols and zonal vegetation with xerophytic elements the proposed model of sea level control on the hydrological cycle integrates coeval and subsequent occurrences of wet and dry lowlands hydromorphic and well drained palaeosols and intrazonal and zonal vegetations thus the schilfsandstein does not provide arguments for a humid mid carnian episode supplementary material datasets of palynomorph eco group peg and macroplant eco group meg analyses are available at https doi org 10 6084 m9 figshare c 4182593

mw 8 6 sumatran earthquake of 11 april 2012 rare seaward expression of oblique subduction the magnitude 8 6 and 8 2 earthquakes off northwestern sumatra on 11 april 2012 generated small tsunami waves that were recorded by stations around the indian ocean combining differential travel time modeling of tsunami waves with results from back projection of seismic data reveals a complex source with a significant trench parallel component the oblique plate convergence indicates that 20 50 m of trench parallel displacement could have accumulated since the last megathrust earthquake only part of which has been taken up by the great sumatran fault this suggests that the remaining trench parallel motion was released during the magnitude 8 6 earthquake on 11 april 2012 within the subducting plate the magnitude 8 6 earthquake is interpreted to be a result of oblique subduction as well as a reduction in normal stress due to the occurrence of the sumatra andaman earthquake in 2004

variations of b values preceding large earthquakes in the andaman sumatra subduction zone abstract fifteen largest earthquakes m w 7 occurring between 2000 and 2010 in the andaman sumatra region are studied the available usgs list of events used is complete for a threshold magnitude m c 4 5 and contains 6973 shocks spatial and temporal variation of b values in the gutenberg richter formula log n a bm was investigated in six selected epicentral regions the technique of moving spatial and time windows was applied deduced b values show large variations from 0 55 to 2 40 the 15 largest events all took place within regions of low b and were preceded by significant drops in b values observed correspondence between low b and the occurrence of large earthquakes suggests that b t has a potential which could be employed in a medium term months years earthquake prediction

new magnetobiostratigraphic results from the ladinian of the dolomites and implications for the triassic geomagnetic polarity timescale abstract we investigated for magnetostratigraphy the rio nigra and rio frommer stratigraphic sections from alpe di siusi seiser alm dolomites northern italy in order to improve the calibration of the triassic time scale both sections are characterized by ammonoid and conodont associations typical of longobardian late ladinian middle triassic age moreover the rio nigra section is constrained by a u pb zircon date of 237 77 0 05 ma building on the recently verified newark hartford astrochronological polarity timescale for the late carnian rhaetian plus the hettangian and through magnetostratigraphic correlations of an updated inventory of tethyan marine stratigraphic sections from the literature some of which are provided with u pb zircon age constraints we propose a revised geomagnetic polarity time scale for the entire triassic

crustal dilatation observed by grace after the 2004 sumatra andaman earthquake we report the detection of an earthquake by a space based measurement the gravity recovery and climate experiment grace satellites observed a 15 microgalileo gravity change induced by the great december 2004 sumatra andaman earthquake coseismic deformation produces sudden changes in the gravity field by vertical displacement of earth s layered density structure and by changing the densities of the crust and mantle grace s sensitivity to the long spatial wavelength of gravity changes resulted in roughly equal contributions of vertical displacement and dilatation effects in the gravity measurements the grace observations provide evidence of crustal dilatation resulting from an undersea earthquake

slip partitioning along major convergent plate boundaries along plate boundaries characterized by oblique convergence earthquake slip vectors are commonly rotated toward the normal of the trench with respect to predicted plate motion vectors consequently relative plate motion along such convergent margins must be partitioned between displacements along the thrust plate interface and deformation within the forearc and back arc regions the deformation behind the trench may take the form of strike slip motion back arc extension or some combination of both we observe from our analysis of the harvard moment tensor catalog that convergent arcs characterized by back arc spreading specifically the marianas and new hebrides are characterized by a large degree of slip partitioning however the observed rates directions and location of back arc spreading are not sufficient to account for degree of partitioning observed along the respective arcs implying that the oblique component of subduction is also accommodated in part by shearing of the overriding plate in the case of the sumatran arc where partitioning is accommodated by strike slip faulting in the overriding plate the degree of partitioning is similar to that observed along the marianas but the result is viewed with caution because it is based on a predicted plate motion vector that is based on locally derived earthquake slip vectors in the case of the alaskan aleutian arc where back arc spreading is also absent the degree of partitioning is less and rotation of slip vectors toward the trench normal appears to increase linearly as a function of the obliquity of convergence if partitioning in the alaskan aleutian arc is accommodated by strike slip faulting within the upper plate the positive relationship between obliquity of convergence and the rotation of earthquake slip vectors to the trench normal may reflect that either 1 the ratio of the depth extent of strike slip faults behind the trench z s to the subduction thrust z t increases westward along the arc 2 the dip of the subduction thrust increases westward along the arc or 3 the strength of the subduction thrust decreases westward along the arc

dynamic stratigraphy of an evaporite to red bed sequence gipskeuper triassic southwest german basin abstract the dynamics of evaporite accumulation are studied in the gipskeuper triassic of the southwest german epicontinental basin based on a hierarchical three level stratigraphic analysis 1 among the various stratification types the following are most important a thin carbonate intervals with marine faunas b massive sulfates with selenite indicating very shallow subaqueous gypsum precipitation c thin bedded gypsarenites with a variety of sedimentary structures suggesting clastic evaporite accumulation during high energy events gypsum tempestites d laminated gypsum with spectacular tepee structures testifying inter to supratidal settings e green grey and reddish claystones with nodular gypsum indicating evaporitic playa mudflats 2 facies sequences occur in several varieties and commonly form 1 4 m thick transgressive regressive cycles with shallowing upwards trends the long recognized carbonate marker beds represent short term trans or ingressions into the almost flat keuper basin highly disturbed tepee horizons form widely correlatable regressive peaks these sequences form evaporite equivalents to the ubiquitous shallowing upward cycles known from carbonate systems 3 the basin fill consists of a small scale cycles being vertically stacked upon each other to form the basic building block of the layer cake architecture of the gipskeuper succession the stacking of small scale cycles is superimposed onto a larger scale regressive cycle which records a general shift from restricted marginal marine to hypersaline marine to the more continental red bed deposition of the overlying keuper this hierarchy of cycles probably reflects various orders of eustatic sealevel fluctuations the gipskeuper thus exemplifies dynamics of evaporite accumulation and allows us to understand some of the processes that produce a layer cake stratigraphy its cycle hierarchy is a common motif in the entire southwest german basin fill and appears typical for epicontinental basins

carnian late triassic magnetostratigraphy from the germanic basin allowing global correlation of the mid carnian episode abstract the stuttgart formation traditionally called the schilfsandstein in the germanic basin or central european basin is a sand rich episode representing the mid carnian episode within the gypsum rich clayey semi arid keuper facies that regional mid carnian episode is now recognized to be a manifestation of a significant global disruption of earth s climate ocean biological system during the early late triassic in order to provide an accurate time frame and means for high resolution correlations among continental and marine records we obtained a composite magnetostratigraphy spanning the entire carnian from three boreholes in the germanic basin this composite shows a good consistency with earlier published magnetostratigraphy results from south china and enables the construction of a complete carnian polarity time scale the upper carnian tuvalian substage portion implies that 1 the lower quarter of the tuvalian is dominated by a reversed polarity magnetozone 2 the termination of the yangtze platform is coeval with deposition of the stuttgart formation in the germanic basin 3 the radiolarian rich green colored clay horizon of the pignola 2 section in south italy that is below a volcanic ash bed dated as ca 231 ma correlates with the d pulse of siliciclastics in dibona section of north italy in the middle of the tuvalian 4 the upper three fourths of the tuvalian is a major normal polarity dominated magnetozone and this interval correlates with the basal e1 e6 portion of the newark magnetic polarity reference series according to the favored correlation option 5 the base of the arnstadt formation of the germanic basin which had been traditionally assigned as the carnian norian boundary instead begins within the lower portion of newark reversed polarity zone e8r of earliest norian according to the favored age model although pending future verification 6 the polarity patterns of portions of the upper carnian from the western tethys sections of lower trench at silicka brezova in austria and pizzo mondello in italy are verified this carnian composite is an enhanced polarity time scale for calibration of other global carnian successions and events such as the appearance of the earliest dinosaurs in fossiliferous beds of south america

the aftermath of the cpe and the carnian norian transition in northwestern sichuan basin south china the northwestern sichuan basin south china was a portion of eastern tethys where during the late triassic a sharp lithological transition from oolitic bioclastic limestones and sponge reef mounds to dark grey terrigenous clays siltstones and sandstones is visible in several localities the timing and significance of this major facies transition is still unclear here we report new biostratigraphic and carbon stable isotope data from hanwang and jushui northwestern sichuan basin sporomorphs ammonoids conodonts and halobiid bivalves show that the lithological change is late carnian to early norian in age this amended age determination facilitates recalibration of the magnetostratigraphy in the area allowing correlation between the late triassic of the sichuan basin and the astrochronostratigraphic polarity time scale a carbon stable isotopic perturbation across the carnian norian boundary cnb is missing in our sections or it is concealed because of the mixed organic matter sources our findings pinpoint the position of the cnb to a short stratigraphic interval of c 12 m thickness in the sichuan basin the studied sections greatly extend the palaeogeographical documentation of the cnb and provide novel information on biostratigraphy and chemostratigraphy that should be considered in defining the best position of the norian global stratotype section and point

tracking an upper limit of the carnian crisis and or carnian stage in the western carpathians slovakia the late triassic timescale especially the carnian norian boundary is poorly constrained mainly due to a paucity of high precision radio isotopic ages that can be related accurately to contradictions between the biostratigraphic and magnetostratigraphic correlations la icp ms dating of detrital zircons from five samples of the lunz formation the upper triassic siliciclastic sediments from the western carpathians slovakia provided a wide spectrum of ages that vary from late archaean ca 2582 ma to triassic ca 216 ma these marine delta sediments represent a typical product of the carnian crisis a major climate change and biotic turnover that occurred during the carnian stage in the tethys ocean within the carbonate shelf and intrashelf basins in the northern calcareous alps and the western carpathians the supply of clastic material in the studied lunz formation was derived from several sources especially i from the recycled variscan orogen ii from the remote east european platform and iii from the contemporaneous triassic volcanic sources syn sedimentary volcanic zircons with a concordia age of 221 2 1 6 ma calculated from 12 single analyses represent the maximum age of deposition of the lunz formation and demonstrate that the upper limit of the carnian crisis and or the carnian stage in the alpine carpathians realm is younger than the current age of the carnian norian boundary at ca 227 ma listed on the international chronostratigraphic chart international commission on stratigraphy 2016 12 edition

the strong diachronous muschelkalk keuper facies shift in the central european basin implications from the type section of the erfurt formation lower keuper triassic and basin wide correlations the transition from the shallow marine upper muschelkalk sea to the lower keuper fluvial plain represents the most diachronous facies shift of the entire germanic triassic the type section of the fluvial lower keuper erfurt formation is described in detail for the first time including biostratigraphic dating of the muschelkalk keuper boundary the type section is integrated into a nne ssw cross section through the central european basin and the muschelkalk keuper facies shift is constrained by high resolution conodont and ceratite biostratigraphy thus the fundamental changes in palaeogeography shifts of facies belts and stratal pattern architecture are visualised forced by a rapid transgression from tethyan waters the shallow marine upper muschelkalk sea attained its maximum flooding in the lower conodont zone 2 sequens pulcher to philippi robustus zones subsequent slow continuous regression to the south was accompanied by step by step progradation of coastal to fluvial plain environments of the lower keuper culminating in a fluvial plain extending to south germany based on stratal patterns an improved sequence stratigraphic interpretation for the upper muschelkalk lower keuper interval is suggested in combination with biostratigraphic arguments the new sequence stratigraphy points to a revised correlation of this interval within the tethyan triassic incorporating the positions of the anisian ladinian and fassanian longobardian boundaries

stress triggering of the great indian ocean strike slip earthquakes in a diffuse plate boundary zone 1 on april 11 2012 two great magnitude 8 earthquakes occurred within a two hour period off the west coast of northern sumatra indonesia in the broadly distributed india australia plate boundary zone the magnitude 8 6 mainshock holds the distinction of being both the largest instrumentally recorded strike slip earthquake and the largest earthquake away from a recognized plate boundary fault the mainshock involved sequential ruptures of multiple fault planes oriented nearly perpendicular to each other the adjacent 2004 megathrust earthquake statically loaded the northern wharton basin oceanic lithosphere on both of the 2012 mainshock fault plane orientations and greatly enhanced the rate of earthquake activity in the region for a year viscoelastic relaxation of the asthenosphere following the 2004 and 2005 megathrust earthquakes continued to positively stress the offshore region correlating with the locations of later strike slip earthquakes including two magnitude 7 and the 2012 magnitude 8 earthquakes

multiple negative carbon isotope excursions during the carnian pluvial episode late triassic abstract the carnian pluvial episode was a phase of global climatic change and biotic turnover that occurred during the early late triassic in marine sedimentary basins the arrival of huge amounts of siliciclastic sediments the establishment of anoxic conditions and a sudden change of the carbonate factory on platforms marked the carnian pluvial episode the sedimentary changes are closely associated with abrupt biological turnover among marine and terrestrial groups as for example an extinction among ammonoids and conodonts in the ocean and a turnover of the vertebrate fauna and the flora on land multiple negative carbon isotope excursions were recorded during the carnian pluvial episode in both organic matter and marine carbonates suggesting repeated injection of 13c depleted co2 into the ocean atmosphere system but their temporal and causal links with the sedimentological and palaeontological changes are poorly understood we here review the existing carbon isotope records and present new data on the carbon isotope composition of organic carbon in selected sections of the western tethys realm that record the entire carnian pluvial episode new ammonoid conodont and sporomorph biostratigraphic data were collected and coupled to an extensive review of the existing biostratigraphy to constrain the age of the sampled sections the results provide biostratigraphically constrained composite organic carbon isotope curves for the carnian which sheds light on the temporal and causal links between the main carbon isotope perturbations and the distinct environmental and biotic changes that mark the carnian pluvial episode the carbon isotope records suggest that a series of carbon cycle perturbations possibly recording multiple phases of volcanic activity during the emplacement of the wrangellia large igneous province disrupted carnian environments and ecosystems repeatedly over a remarkably long time interval of about 1 million years

seismic b value anomalies in the sumatran region seismotectonic implications abstract the spatial variations in the seismic b value seismic moment bouguer gravity change and fault plane solution are estimated in the sumatran region based on homogeneous seismicity data from june 2005 to march 2012 to investigate the seismotectonic characteristics and tectonic activity between the 2004 sumatran earthquake and the 2012 east indian ocean earthquakes based on changes in the seismicity rate this time period is divided into five intervals with different earthquake distributions and faulting styles the seismic b values faulting mechanisms and seismic moment release values are mapped throughout the sumatran region and the gravity change every two years between the 2004 event and the 2012 events are determined from satellite grace gravity data the b values vary from 0 45 to 1 59 and an inverse correlation is observed between the b values and convergence rates low b values are located at depths between 20 km and 40 km in the subduction zone and between 20 km and 35 km in the oceanic plate the lowest b values are located at a depth of approximately 28 km in both regions which indicates a homogeneous fault system between them the areas with low b values are associated with megathrust and strike slip mechanisms while the area with the lowest b values is dominated by a megathrust mechanism seismically active regions have low b values associated with a high stress accumulation and high seismic moment release low b value areas are located mainly along the andaman sunda trench and andaman nicobar sumatra forearc temporal variations in the seismicity distribution and faulting style are recognized with temporal variations in the b values in each period relationships exist between the epicenter of the 2004 event and the location of the maximum bouguer gravity change in 2012 and between the epicenters of the 2012 events and the location of the maximum bouguer gravity change in 2004 furthermore a zone of continuous 2 year positive gravity change is located near the nicobar islands the 2004 event boost the 2012 events and intraplate seismicity via stress transfer the seismicity distributions in individual periods within the studied timeframe highlight the active and locked portions of the fault systems

sequence stratigraphy after the demise of a high relief carbonate platform carnian of the dolomites sea level and climate disentangled abstract sedimentary facies analysis aided by quantitative 3d georeferenced field data is applied to constrain the sequence stratigraphy of a complex stratigraphic interval in the late triassic of the dolomites this multidisciplinary approach was the key to disentangle the timing of climatic change vs sea level fluctuation and their effects on shallow water carbonate depositional systems the carnian pluvial event a global episode of climate change worldwide documented at low latitudes involved increased rainfall and possibly global warming this climatic event begins before a drop of sea level and caused the demise of microbial dominated high relief carbonate platforms that dominated the dolomites region and was followed by a period of coexistence of small microbial carbonate mounds and arenaceous skeletal oolitic grainstones a subsequent sea level fall brought to the definitive disappearance of microbialites and shallow water carbonates switched to ramps dominated by oolitic bioclastic grainstones the crisis of early carnian shallow water carbonate systems of the dolomites generated a geological surface similar to a drowning unconformity although no transgression occurred as the high relief microbial carbonate systems characterized by steep slopes switched to gently inclined oolitic skeletal siliciclastic ramps basins were rapidly filled the change of carbonate depositional systems was associated with an increase in siliciclastic input in turn triggered by the onset of a humid climatic event and only later to a sea level drop this evolution of carbonate systems cannot be interpreted in the light of sea level changes only climate change and consequent ecological changes in the main carbonate producing biotas induced significant modifications in depositional geometries this case study may serve as a conceptual model for the sedimentary evolution of carbonate systems subject to ecological crisis that do not evolve in platform drowning because despite a drop in shallow water carbonate production a combination of low subsidence and or sea level drop maintains the platform top at shallow depth

quaternary geology of the middle son valley north central india implications for prehistoric archaeology abstract the late quaternary alluvial history of the son is very similar to that of the nile the amazon and the murray murrumbridgee during the terminal pleistocene cros bedded sands were laid down as bedload by a highly seasonal low sinuosity stream early holocene deposition of horizontally stratified silts and clays is the suspended load of regular overbank flooding by a less seasonal more sinuous stream the upward fining sequence of the late quaternary son coincides with a global change in climate in the intertropical zone from cold and dry in the terminal pleistocene 25 000 b p to warm and wet in the early holocene two earlier alluvial formations are present in the middle son valley one directly overlying eroded bedrock comprises fanglomerates and clays of a mantled pediment sequence developed when river level was low and the climate dry lower palaeolithic artifacts of upper acheulian aspect are common near the fanglomerate clay contact the clay may be reworked aeolian dust the other younger formation is fluviatile it represents an influx of allocthonous gravels under high flow regime during the late pleistocene 75 000 b p middle palaeolithic implements fashioned from the exotic gravels are found in situ in this formation produced by a return to wetter conditions earlier two dimensional models which equate the north central indian lower middle and upper palaeolithic respectively with gravels i ii and iii of the belan valley sequence now require amendment the three dimensional model proposed here to account for the quaternary alluvial formations in the middle son valley also has important implications for archaeological prospecting primary context microlithic sites are generally confined to the outer margin of the early holocene floodplain along the piedmont zone of the kaimur hills derived middle palaeolithic flakes and tools are scattered throughout the terminal pleistocene cross bedded sands of the son relatively undisturbed middle palaeolithic assemblages are stratified within the preceding alluvial formation

the middle carnian wet intermezzo of the stuttgart formation schilfsandstein germanic basin abstract the middle carnian wet intermezzo mcwi of the stuttgart formation schilfsandstein and age equivalent strata of the northwestern tethys occurred entirely within equivalents of the upper subzone of the austrotrachyceras austriacum ammonoid zone of the late julian its duration is estimated to be only about 0 7 0 8 myr in both the germanic basin and the northwestern tethys the warm climate during the mcwi was characterized by a rate of precipitation that exceeded somewhat the evaporation but was not so great as to be pluvial the mcwi was related to the atmospheric circulation of a megamonsoonal system that was characterized by strong moisture laden northwesterly flowing trade winds that rose as they reached the estimated 2000 3000 m high eastern shoulder uplift of a huge rift causing them to drop an extraordinary amount of rain this eastern shoulder uplift lay within the caledonides of modern day western scandinavia this region only between 30 and 50 n palaeolatitude had a truly pluvial climate and the huge amounts of fresh water dropped there transported large amounts of siliciclastics from this rift shoulder uplift southward into the germanic basin before deposition of the siliciclastics an early julian eustatic sea level fall caused widespread erosion in the germanic basin in the later part of late julian a transgression from the eastern gates with the concurrent strong fresh water influx from the north flooded the centre of the northern germanic basin with a shallow brackish sea in which the osterhagen horizon basisschichten of the lower stuttgart formation was deposited in the upper osterhagen horizon the salinity rapidly decreased from mesohaline through mio and oligohaline to fresh water levels in southern germany the basisschichten formed entirely within fresh water or very low salinity brackish environments later a slight subsidence of the southwestern germanic basin shifted the main outflow of fresh water toward the southwestern end of the basin creating local brackish conditions in the northern marginal part of the northwestern tethys e g in the lunz beds during this time interval tidal influence also can be found in the stuttgart formation deposited in palaeoestuaries of the southwestern germanic basin adjacent to the tethys the very strong fresh water influx from the north however prevented these estuaries from developing a strongly elevated salt content so that only fresh water to oligohaline brackish faunas are found there such as the eberstadt bivalve conchostracan fauna at the base of the tuvalian the megamonsoonal system either disintegrated or else the trade winds shifted their principal flow direction this caused the climate within the germanic basin and in the nearby northwestern tethys sea to become arid again as it had been before the deposition of the stuttgart formation these changes in the atmospheric circulation patterns also terminated the pluvial climatic regime to the north along the scandinavian eastern rift shoulder uplift this in turn ended the transport of huge amounts of siliciclastics from this region southward into the germanic basin and ended the deposition of the schilfsandstein after this the hypersaline sabkha and playa sedimentation of the weser formation began which was accompanied by some minor marine ingressions in the southwestern germanic basin

palynological correlation of carnian humid pulses throughout western tethys abstract the carnian pluvial event is an upper triassic swing toward increased rainfall best documented in the tethys tropical belt and mainly recognized on its effects on sedimentary systems as the demise of carbonate platforms and the enhanced siliciclastic supply in some portions of western tethys and particularly in the raibler schichten of the northern calcareous alps and in the dolomites the carnian pluvial event is recorded by four discrete siliciclastic pulses in the raibler schichten three siliciclastic intervals are documented and take the name of first second and third shale in order to correlate these pulses at the basinal scale the study of the palynological assemblages in a section of the raibler schichten near rubland austria and of the classical succession of the lunz nappe have been carried out more than eighty palynomorph species are recorded most of them correspond to typical carnian morphospecies of the carnian pluvial event in europe on the base of their stratigraphic distribution three different palynomorph assemblages are described aulisporites astigmosus assemblage lagenella martinii assemblage and granuloperculatipollis rudis assemblage a fourth older assemblage is also informally defined a palynostratigraphic correlation between the nca the germanic basin and the dolomites has been obtained the four siliciclastic pulses recognized in the raibler schichten and lunz are also found in the dolomites and yield the same palynological associations the base of the schilfsandstein that record the carnian pluvial event in the germanic basin is correlated to the second or third siliciclastic pulse first or second shale of the raibler schichten siliciclastic pulses are thus correlated throughout western tethys and can thus be interpreted as short lived humid climate wiggles within the carnian pluvial event a quantitative analysis of the carnian successions of the nca highlights a shift toward hygrophytic elements in the uppermost julian and an abrupt return to xerophytic associations in the lower tuvalian the palynological hygrophytic associations that characterize the aulisporites astigmosus and lagenella martinii assemblages are present in many other parts of europe and middle east suggesting that the carnian pluvial event determined a humid climate perturbation in a wide area of the northern hemisphere spanning from tropical to high latitudes

instantaneous global plate motion model from 12 years of continuous gps observations 1 we estimate a global plate motion model for 17 major and minor tectonic plates solely on the basis of analysis of data from 106 globally distributed continuous gps stations spanning the period from january 1991 to july 2003 site positions estimated from 24 hour segments of data are aligned day by day to the international gps service igs realization of the itrf2000 reference frame using a similarity transformation thereby ensuring that the itrf2000 no net rotation condition is preserved linear velocities of a carefully selected set of stations are estimated from the position time series along with annual and semiannual fluctuations and position offsets due to gps instrument changes a white noise plus flicker noise model is applied to estimate realistic uncertainties for the site velocities which are then propagated into the derived plate motion model parameters we also examine the vertical velocities in the site selection process at the scripps orbit and permanent array center we have implemented a procedure whereby the plate motion model is updated on a regular monthly basis to improve its precision and reliability as new data become available and as a baseline against which anomalous motions can be detected

latest permian to middle triassic cyclo magnetostratigraphy from the central european basin germany implications for the geomagnetic polarity timescale in central germany the about 1 km thick mainly clastic germanic lower triassic buntsandstein consists of about 60 sedimentary cycles which are considered to reflect variability in precipitation within the epicontinental central european basin most probably due to solar induced short eccentricity cycles they provide a high resolution cyclostratigraphic framework that constitutes the base for creating a composite geomagnetic polarity record in which this paper presents a middle buntsandstein to lowermost muschelkalk magnetostratigraphy obtained from 6 outcrops and 2 wells where a total of 471 samples was collected combined with recently established records a well documented magnetostratigraphy for the upper zechstein to lowermost muschelkalk latest permian to middle triassic of central germany has been constructed encompassing an overall stratigraphic thickness of about 1 3 km and 22 magnetozones derived from about 2050 paleomagnetic samples along with available biostratigraphy this multi disciplinary study facilitates detailed links to the marine realm in order to directly refer biostratigraphically calibrated triassic stage boundaries as well as radioisotopic ages to the buntsandstein cyclostratigraphy and conversely to contribute to calibrating the geologic timescale 2007 elsevier b v all rights reserved

the carnian humid episode of the late triassic a review from 1989 to 1994 a series of papers outlined evidence for a brief episode of climate change from arid to humid and then back to arid during the carnian stage of the late triassic epoch this time of climate change was compared to marine and terrestrial biotic changes mainly extinction and then radiation of flora and fauna subsequently termed albeit incorrectly the carnian pluvial event cpe by successive authors interest in this episode of climatic change has increased steadily with new evidence being published as well as several challenges to the theory the exact nature of this humid episode whether reflecting widespread precipitation or more local effects as well as its ultimate cause remains equivocal bed by bed sampling of the carnian in the southern alps dolomites shows the episode began with a negative carbon isotope excursion that lasted for only part of one ammonoid zone a austriacum however that the carnian humid episode represents a significantly longer period both environmentally and biotically is irrefutable the evidence is strongest in the european middle eastern himalayan north american and japanese successions but not always so clear in south america antarctica and australia the eruption of the wrangellia large igneous province and global warming causing increased evaporation in the tethyan and panthalassic oceans are suggested as causes for the humid episode

synchroneity of climatic change and extinctions in the late triassic although the late triassic was a time of widespread aridity evidence exists for a significant increase in rainfall during the middle to late carnian upper triassic playa lake sediments were interrupted by late carnian fluviatile sandstones with erosive bases and high kao linite illite ratios there was also an increase in the clastic component of marine sequences during this interval middle and upper carnian marine carbonates show an extreme depletion in 13 c values consistent with increased fresh water influx large scale karstic phenomena in limestone areas subaerially exposed during the late triassic are a further indication of increased rainfall important faunal and floral changes occurred during the carnian norian interval marine invertebrate turnover was greatest at the lower middle carnian boundary and terrestrial extinctions were concentrated at the carnian norian boundary the cause of this carnian pluvial episode may have been related to the rifting of pangea through disruption of atmospheric and oceanic circulation patterns eustatic changes or the effects of volcanism associated with rifting a change in surface ocean temperature salinity or ph or habitat loss may have caused the decline of many shallow marine invertebrates at the start of the middle carnian a return to arid conditions at the carnian norian boundary would account for the turnover among terrestrial vertebrates and plants

climate warming euxinia and carbon isotope perturbations during the carnian triassic crisis in south china abstract the carnian humid episode che also known as the carnian pluvial event and associated biotic changes are major enigmas of the mesozoic record in western tethys we show that the che also occurred in eastern tethys south china suggestive of a much more widespread and probably global climate perturbation oxygen isotope records from conodont apatite indicate a double pulse warming event the che coincided with an initial warming of 4 c this was followed by a transient cooling period and then a prolonged 7 c warming in the later carnian tuvalian 2 carbon isotope perturbations associated with the che of western tethys occurred contemporaneously in south china and mark the start of a prolonged period of carbon cycle instability that persisted until the late carnian the dry wet transition during the che coincides with the negative carbon isotope excursion and the temperature rise pointing to an intensification of hydrologic cycle activities due to climatic warming while carbonate platform shutdown in western tethys is associated with an influx of siliciclastic sediment the eastern tethyan carbonate platforms are overlain by deep water anoxic facies the transition from oxygenated to euxinic facies was via a condensed manganiferous carbonate mno content up to 15 1 wt that records an intense mn shuttle operating in the basin significant siliciclastic influx in south china only occurred after the che climatic changes and was probably due to foreland basin development at the onset of the indosinian orogeny the mid carnian biotic crisis thus coincided with several phenomena associated with major extinction events a carbonate production crisis climate warming 13 c oscillations marine anoxia biotic turnover and flood basalt eruptions of the wrangellia large igneous province

cycle calibrated magnetostratigraphy of middle carnian from south china implications for late triassic time scale and termination of the yangtze platform abstract thick successions from the margins of the triassic yangtze platform of the south china block record a transition from carbonate rich facies zhuganpo formation and equivalents to clastic rich facies xiaowa formation and equivalents during the carnian early late triassic that mark the final phase of termination of this long lived platform cyclostratigraphy derived from spectral gamma ray sgr intensity curves was combined with magnetostratigraphy of two sections in guizhou province wayao transect and its upward extension into the geopark wayao in guanling county and the laishike section in zhenfeng county and one location in sichuan province hanwang section the cyclostratigraphy from all the guizhou sections indicates a persistent suite of ca 34 m 9 m and 1 8 m cycles which are consistent with the ratios of orbital climate oscillations caused by long eccentricity 405 kyr short eccentricity 100 kyr and precession 20 kyr the magnetostratigraphy of all sections is consistent with the cyclicity and characteristic sgr features thereby enabling a cycle tuned magnetic polarity scale spanning 2 4 myr the main feature is a 1 3 myr interval of reversed polarity containing brief normal polarity subchrons and this reversed polarity chron appears to correspond to the significant reversed polarity dominated interval spanning the upper half of the trachyceras aonoides through the lower half of the austrotrachyceras austriacum ammonoid zones of the upper julian the lower substage of carnian this magnetostratigraphic correlation implies that the termination of the yangtze platform is coeval with the beginning of the mid carnian episode of climatic disruption in europe which is locally called the carnian pluvial event or wet intermezzo and with the temporary cessation of the platform carbonates in the dolomites the cycle scaled magnetic polarity time scale supports the short tuvalian long norian age model of the late triassic in which the base of the cycle tuned polarity pattern from the newark group of eastern north america is younger than the end of the julian substage

postseismic grace and gps observations indicate a rheology contrast above and below the sumatra slab more than 7 years of observations of postseismic relaxation after the 2004 sumatra andaman earthquake provide an improving view on the deformation in the wide vicinity of the 2004 rupture we include both gravity recovery and climate experiment grace gravity field data that show a large postseismic signal over the rupture area and gps observations in the back arc region with increasing time gps and grace show contrasting relaxation styles that were not easily discernible on shorter time series we investigate whether mantle creep can simultaneously explain the far field surface displacements and the long wavelength gravity changes we interpret contrasts in the temporal behavior of the gps grace observations in terms of lateral variations in rheological properties of the asthenosphere below and above the slab based on 1 d viscoelastic models our results support an almost order of magnitude contrast between oceanic lithosphere viscosity and continental viscosity which likely means that the low viscosities frequently found from postseismic deformation after subduction earthquakes are valid only for the mantle wedge next to mantle creep we also consider afterslip as an alternative mechanism for postseismic deformation we investigate how the combination of grace and gps data can better discriminate between different mechanisms of postseismic relaxation distributed deformation mantle creep versus localized deformation afterslip we conclude that the grace observed gravity changes rule out afterslip as the dominant mechanism explaining long wavelength deformation even over the first year after the event

stress changes along the sunda trench following the 26 december 2004 sumatra andaman and 28 march 2005 nias earthquakes 1 the 26 december 2004 mw 9 2 and 28 march 2005 mw 8 7 earthquakes on the sumatra megathrust altered the state of stress over a large region surrounding the earthquakes we evaluate the stress changes associated with coseismic and postseismic deformation following these two large events focusing on postseismic deformation that is driven by viscoelastic relaxation of a low viscosity asthenosphere under coulomb failure stress cfs theory the december 2004 event increased cfs on the future hypocentral zone of the march 2005 event by about 0 25 bar with little or no contribution from viscous relaxation coseismic stresses around the rupture zones of the 1797 and 1833 sunda trench events are negligible but postseismic stress perturbations since december 2004 are predicted to result in cfs increases of 0 1 to 0 2 bar around these rupture zones between 2 and 8 years after the december 2004 event these are considerable stress perturbations given that the 1797 and 1833 rupture zones are likely approaching the end of a complete seismic cycle

astronomical tuning of the end permian extinction and the early triassic epoch of south china and germany abstract the timing of the end permian mass extinction and subsequent prolonged recovery during the early triassic epoch can be established from astronomically controlled climate cycles recorded in continuous marine sedimentary sections astronomical cycle tuning of spectral gamma ray logs from biostratigraphically constrained cyclic stratigraphy through marine sections at meishan chaohu daxiakou and guandao in south china yields an integrated time scale for the early triassic which is consistent with scaling of magnetostratigraphy from climatic cycles in continental deposits of the germanic basin the main marine mass extinction interval at meishan is constrained to less than 40 of a 100 kyr kilo year cycle i e c 13 is estimated to have lasted c 13 from 2 to 4 across the smithian spathian boundary at chaohu was completed in 50 kyr the earliest marine reptiles in the mesozoic at chaohu that are considered to represent a significant recovery of marine ecosystems did not appear until 4 7 myr million years after the end permian extinction the durations of the griesbachian dienerian smithian and spathian substages including the uncertainty in placement of widely used conodont biostratigraphic datums for their boundaries are 1 4 0 1 0 6 0 1 1 7 0 1 and 1 4 0 1 myr implying a total span for the early triassic of 5 1 0 1 myr therefore relative to an assigned 251 902 0 024 ma for the permian triassic boundary from the meishan gssp the ages for these substage boundaries are 250 5 0 1 ma for base dienerian 249 9 0 1 ma for base smithian base of olenekian stage 248 2 0 1 ma for base spathian and 246 8 0 1 ma for the base of the anisian stage this astronomical calibrated timescale provides rates for the recurrent carbon isotope excursions and for trends in sedimentation accumulation through the early triassic of studied sections in south china

the 11 april 2012 east indian ocean earthquake triggered large aftershocks worldwide although strong remote aftershocks are exceedingly rare their rate increased fivefold during the six days following the 2012 east indian ocean earthquake perhaps as a result of the strike slip nature of the 2012 event or a build up of close to failure nucleation sites

tectonics and history of the andaman sea region abstract the andaman sea is an active backarc basin lying above and behind the sunda subduction zone where convergence between the overriding southeast asian plate and the subducting australian plate is highly oblique the effect of the oblique convergence has been formation of a sliver plate between the subduction zone and a complex right lateral fault system the late paleocene collision of greater india and asia with approximately normal convergence started clockwise rotation and bending of the northern and western sunda arc the initial sliver fault which probably started in the eocene extended through the outer arc ridge offshore from sumatra through the present region of the andaman sea into the sagaing fault with more oblique convergence due to the rotation the rate of strike slip motion increased and a series of extensional basins opened obliquely by the combination of backarc extension and the strike slip motion these basins in sequence are the mergui basin starting at 32 ma the conjoined alcock and sewell rises starting at 23 ma east basin separating the rises from the foot of the continental slope starting at 15 ma and finally at 4 ma the present plate edge was formed alcock and sewell rises were separated by formation of the central andaman basin and the faulting moved onshore from the mentawai fault to the sumatra fault system bisecting sumatra

spatial and temporal b value anomalies preceding the devastating off coast of nw sumatra earthquake of december 26 2004 1 spatial and temporal variations of b values are studied by means of 624 earthquakes in the andaman nicobar islands region during a five year period preceding the giant shock on december 26 2004 sliding time and space windows containing 50 events are used temporal variations reveal two significant drops in b value which coincide with the occurrence of two large shocks ms 7 0 towards the end of 2002 and with the mw 9 0 event in 2004 the spatial distribution shows accumulation of stresses low b around the epicentres of the 2002 and 2004 events and an event in north andaman the area of high stress around the 2004 epicenter extends in nnw sse direction over an area about 450 km long

sequence stratigraphic framework of the german triassic abstract the sequence stratigraphic methodology can be readily applied to the cratonic basin fill of the classic german triassic consisting of shallow marine to terrestrial mixed carbonate siliclastic rocks the whole triassic succession represents a second order transgression regression cycle built by third order depositional sequences systems tracts and parasequences many bounding surfaces represent widely used marker beds long used in classical lithostratigraphy using a synthesis of outcrop well log and literature data on stratal geometry facies cycle stacking patterns and paleogeography a regional chart of coastal onlap was constructed within the limitations of the presently available biostratigraphic data the observed cycles appear to correlate fairly well with those in other areas but include a number of additional sequences not included in the haq et al 1988 chart comparative analysis of regional onlap curves from different globally spread triassic basins together with an improved biostratigraphy will be necessary to relate the accommodation changes to eustatic versus tectonic and climatic controls and to produce a refined eustatic chart the german basin could provide a favourable reference point for such an analysis

the biostratigraphic importance of conchostracans in the continental triassic of the northern hemisphere conchostracans or clam shrimp order conchostraca sars are arthropods with a carapace consisting of two chitinous lateral valves triassic conchostracans range in size from 2 to 12 5 mm long and are common in deposits that formed in fresh water lakes isolated ponds and brackish areas their dessication and freeze resistant eggs can be dispersed by wind over long distances therefore many conchostracan species are distributed throughout the entire north ern hemisphere in the late permian to middle triassic interval several of these forms are also found in gondwana many wide ranging conchostracan species have short stratigraphic ranges making them excellent guide forms for subdivision of triassic time and for long range correlations the stratigraphic resolution that can be achieved with conchostracan zones is often as high as for ammonoid and conodont zones found in pelagic marine deposits this makes con chostracans the most useful group available for biostratigraphic subdivision and correlation in continental lake deposits upper triassic gondwanan conchostracan faunas are different from conchostracan faunas of the northern hemisphere in the norian some slight provincialism can be observed even within the northern hemisphere for example the sevatian redondestheria seems to be restricted to north america and acadiestheriella n gen so far has been found only in the sevatian deposits from the fundy basin of southeastern canada here we establish a con chostracan zonation for the changhsingian late permian to hettangian early jurassic of the northernhemispherethat forthemostpart isverywellcorrelatedwiththemarinescale thiszona tion is especially robust for the changhsingian to early anisian late ladinian to cordevolian and rhaetian to hettangian intervals for most of the middle and upper triassic this zonation is still preliminary five new genera six new species and a new subspecies of conchostracans are described that are stratigraphically important half of the eight stage boundaries of the triassic have been defined by a bio event within a marine global stratotype and point gssp locality and these definitions have been accepted by both the international subcommission on triassic stratigra phy and the international commission on stratigra phy the remaining four stage boundaries are nearing final definition in the lower triassic both the base of the induan priority brahmanian stage base of triassic and the base of the next younger olenekian stage have been firmly defined in the middle triassic there is wide agree ment that the defining species for the base of the anisian stage should be chiosella timorensis in the gssp candidate site at desli caira romania but there has not yet been a formal vote on this the base of the overlying ladinian stage however has been firmly defined in the upper triassic the base of the carnian has been firmly likewise defined but there is not yet a final defi nition for the boundaries of the overlying norian and rhaetian stages a consensus has not been reached on a defining species for the base of the norian or its gssp locality but all of the different proposals under consideration do at least fall within a rather narrow stratigraphic interval for the base of the rhaetian misikella posthernsteini kozur mock has been chosen as the defining species by the international working group on the rhaetian stage and the gssp candidate locality at steinbergkogel austria has been studied in detail by a group under the leadership of l krystyn vienna and presented to the participants of the international conference on upper triassic sub divisions zonations and events in bad goisern in the autumn of 2008 the base of the overlying hettangian stage base of the jurassic has been defined so far only by a working group as the fad first appearance datum of psiloceras spelae guex taylor rakus bucher the final definition of the triassic stages within marine gssp sections will be completed in the near future but more than 50 of known triassic rocks are of continental origin therefore the main task of triassic stratigraphers in thefuture will besubdivid ing and correlating terrestrial strata both between

palaomagnetische untersuchungen im schilfsandstein trias km2 westeuropas von insgesamt 46 beprobten profilen aus dem schilfsandstein trias km2 westeuropas wurden bislang 41 profile mit 343 einheiten und 870 handstucken mit 1897 einzelkernen auf ihren palaomagnetischen inhalt untersucht

tethyan magnetostratigraphy from pizzo mondello sicily and correlation to the late triassic newark astrochronological polarity time scale we present the magnetostratigraphy and stable isotope stratigraphy from an expanded 430 m thick upper triassic marine limestone section at pizzo mondello sicily and review published biostratigraphic information that can be used to defi ne the location of the conodont carnian norian and norianrhaetian boundaries in this section pizzo mondello offers good potential for magnetostratigraphic correlation of marine biostratigraphic and chemostratigraphic data with the continental newark astrochronological polarity time scale apts for development of an integrated late triassic time scale the relatively stable average values of 18 o centered on 0 are a strong indication that the cherty limestone at pizzo mondello suffered very little diagenetic overprinting the conodont carnian norian boundary is located 12 5 m above a positive shift of 13 c a statistical approach was applied to evaluate various pizzo mondello to newark magnetostratigraphic correlations two correlation options have the highest correlation coeffi cients in option 1 the base of pizzo mondello correlates with the middle part of the newark apts whereas in option 2 the base of pizzo mondello starts toward the early part of the newark apts we prefer option 2 in which the carnian norian boundary based on conodonts as well as its closely associated positive 13 c shift correspond to newark magnetozone e7 at ca 228 227 ma adopting newark astrochronology implying a long norian with a duration of 20 m y and a rhaetian of 6 m y duration these ages are in fact not inconsistent with the few high quality radiometric dates that are available for late triassic time scale calibration based on its good exposure accessibility stratigraphic thickness and continuity and multiple chronostratigraphic correlation possibilities we propose pizzo mondello as global stratigraphic section and point for the base of the norian

stress change and effective friction coefficient along the sumatra andaman sagaing fault system after the 26 december 2004 m w 9 2 and the 28 march 2005 m w 8 7 earthquakes the 2004 aceh and 2005 nias events are the two greatest earthquakes of the past 40 years with a total rupture of 1700 km long and a coseismic slip reaching up to 25 m these two earthquakes have caused large stress perturbations which significantly altered seismic activity in the sumatra andaman region using both detailed mapping of failure planes and various slip distributions we calculate this stress change along the sumatra andaman sagaing fault system from central sumatra to southern myanmar the static coulomb stress change delta cff and the observed seismic activity are in very good agreement with a coulomb index similar to 20 greater than the one obtained for random events compared to previous studies this high coulomb index confirms two important issues on the use of static stress change criterion unsuited to study near field aftershocks and only relevant for aftershocks analysis on large and mature faults at a time scale of several months the calculated delta cff distribution suggests that the 2004 and 2005 earthquakes inhibit failure on the north andaman rift and on the sagaing fault while failure is encouraged along the transform andaman zone the central andaman rift the west andaman fault the sumatra fault system and the offshore thrust faults west of sumatra island the maximum value of similar to 15 20 bar 1 5 2 mpa for delta cff is reached in the northern part of the sumatra fault system this high value together with the lack of major earthquake in the last 170 years result in a high seismic hazard for this region our results are also consistent with temporal evolution of both earthquakes location and focal mechanism prior to and after the events in particular we explain the occurrence and the mechanism of seismic swarms observed in the central andaman rift and along the west andaman fault finally our calculations reveal that the seismicity in the andaman rift zone can only be explained if mu 0 5 this result leads to two end member models one with a constant and high fault friction and one with spatial variations for which friction may depend on either the nature of the lithosphere oceanic versus continental or the fault type

april 2012 intra oceanic seismicity off sumatra boosted by the banda aceh megathrust the two earthquakes of respective magnitudes 8 6 and 8 2 that occurred off the coast of the sumatra subduction zone on 11 april 2012 are shown to be part of a continuing boost of the intraplate deformation between india and australia that followed the aceh 2004 and nias 2005 megathrust earthquakes on 11 april 2012 two of the largest strike slip earthquakes ever recorded at magnitudes of 8 7 and 8 2 occurred in the northeastern indian ocean a few hundred kilometres off the coast of sumatra three groups now report the analysis of seismic data from the days and months before and after these events as well as the events themselves matthias delescluse and co authors show that these earthquakes are part of the ongoing boost of intraplate deformation between india and australia that followed the aceh 2004 and nias 2005 megathrust earthquakes they conclude that the australian plate driven by slab pull forces at the sunda trench is gradually detaching from the indian plate han yue and colleagues show that the 11 april event involved a complex four fault rupture lasting several minutes followed two hours later by a magnitude 8 2 aftershock these great ruptures on a lattice of strike slip faults that extends through the crust and into the upper mantle represent large lithospheric deformation that may eventually create a localized boundary between the indian and australian plates fred pollitz and colleagues show that in the six days following 11 april the global rate of remote earthquakes with magnitudes greater than 5 5 increased nearly fivefold and events up to magnitude 7 seem to have been triggered the unprecedented delayed triggering power of this earthquake may arise from its strike slip source geometry or because it struck at a time of an unusually low global earthquake rate and increased the number of nucleation sites that were very close to failure large earthquakes nucleate at tectonic plate boundaries and their occurrence within a plate s interior remains rare and poorly documented especially offshore the two large earthquakes that struck the northeastern indian ocean on 11 april 2012 are an exception they are the largest strike slip events reported in historical times1 2 and triggered large aftershocks worldwide3 yet they occurred within an intra oceanic setting along the fossil fabric of the extinct wharton basin rather than on a discrete plate boundary4 5 6 7 8 here we show that the 11 april 2012 twin earthquakes are part of a continuing boost of the intraplate deformation between india and australia that followed the aceh 2004 and nias 2005 megathrust earthquakes subsequent to a stress transfer process recognized at other subduction zones9 10 using coulomb stress change calculations we show that the coseismic slips of the aceh and nias earthquakes can promote oceanic left lateral strike slip earthquakes on pre existing meridian aligned fault planes we further show that persistent viscous relaxation in the asthenospheric mantle several years after the aceh megathrust explains the time lag between the 2004 megathrust and the 2012 intraplate events on a short timescale the 2012 events provide new evidence for the interplay between megathrusts at the subduction interface and intraplate deformation offshore on a longer geological timescale the australian plate driven by slab pull forces at the sunda trench is detaching from the indian plate which is subjected to resisting forces at the himalayan front6 8 11

recent seismicity of italy active tectonics of the central mediterranean region and seismicity rate changes after the mw 6 3 l aquila earthquake abstract in this paper we present a new image of the instrumental seismicity of italy obtained by refining hypocentral determinations for about 100 000 earthquakes that occurred in the period 2005 2012 the improved locations yield new constraints on active tectonics of the central mediterranean area where prolonged interaction between nested plates and continental slivers led to the development of the alpine and apennines systems intermediate depth and deep earthquakes define a lateral heterogeneous process of delamination and sinking of the continental lithosphere active beneath the mountain belts shallow seismicity prevalently occurs beneath elevated topography and correlates with low velocity mantle anomalies suggesting a superposition of gravity related forces to the eurasia africa plate convergence the delamination process drives a paired system of compression and extension that stretches the mountain range while shortening the external side of the belts the updated seismic catalog permits us to resolve a sharp variation of seismic rates that occurred in recent years timely after the 2009 mw 6 3 l aquila earthquake the increase of seismic rates is reasonably due to regional scale perturbation of the stress field induced by fluid flow and pore pressure variations within the crust probably related to deep dehydration processes active beneath the mountain belt

the motion and boundary between the capricorn and australian plates the motions between the somalian antarctic and australian plates the three plates believed to meet at the rodrigues triple junction in the indian ocean are inconsistent with the assumption that all three plates are rigid the discrepancy is best explained if the australian plate contains two component plates thus the traditionally defined indo australian plate consists of three component plates and multiple diffuse plate boundaries the pattern of present deformation indicates that the boundaries between the three component plates are two unconnected zones accommodating divergence and a larger zone which we interpret as three diffuse convergent plate boundaries and a diffuse triple junction

the 2012 mw 8 6 sumatra earthquake evidence of westward sequential seismic ruptures associated to the reactivation of a n s ocean fabric 1 the 11 april 2012 mw 8 6 earthquake offshore sumatra is the largest of the rare great intraplate earthquakes of the instrumental era this major strike slip event occurred in the diffuse zone of deformation that accommodates differential rotation between indian and australian plates we perform a back projection analysis calibrated with well located aftershocks of short period teleseismic p waves recorded by the european array to image the rupture process during the mainshock in complement a love wave analysis is conducted for tracking azimuthal change in the apparent global source duration due to the source spatio temporal extent the combined analysis reveals a complex rupture pattern characterized by three main episodes of energy release the latest being located 370 km west of the epicenter on the ninety east ridge with a delay of 120 s we interpret the 11 april 2012 mw 8 6 offshore sumatra earthquake as a complex westward propagating sequence of dynamically triggered strike slip fault ruptures associated to the reactivation of the inherited nne striking sea floor fabric the dynamic triggering mechanism could result from the interaction between transient surface wave stress perturbations and fluids

enhanced magnetization of the marlboro clay as a product of soil pyrogenesis at the paleocene eocene boundary abstract the kaolinite rich marlboro clay was deposited on the inner shelf in the salisbury embayment of the u s atlantic margin at the onset of the carbon isotope excursion marking the 56 ma paleocene eocene boundary and is characterized by an anomalously high concentration of magnetic nanoparticles of enigmatic origin that give rise to notably intense bulk magnetization recent studies point to a magnetic assemblage that is dominated by single domain magnetite particles that tend to be isolated rather than arranged in chains the most distinguishing feature of magnetotactic bacteria fossils on the other hand it is very unlikely that the nanoparticles can be condensates of an impact plume given the meter scale thickness of the marlboro clay we obtained new data from a landward proximal site at wilson lake on the new jersey coastal plain and find that the abrupt increase in magnetite nanoparticles is virtually coincident stratigraphically with the recently reported impact spherule layer at the base of the marlboro clay in the same core yet the high field magnetic susceptibility a measure of total iron concentration and strontium isotope values on bulk sediment an indicator of sediment weathering provenance are not different in the marlboro clay from the immediately underlying vincentown formation we suggest that the distinctive magnetic properties of the marlboro clay originated from pyromagnetic soil enhancement by widespread wildfires on the adjoining drainage area the pyrogenetic products were soon washed from the denuded landscape and rapidly deposited as mud waves across the shelf becoming the marlboro clay a few percent of incinerated biomass ends up as calcite known as wood ash stone and can inherit its light carbon isotope composition disseminated wood ash stone entrained in the marlboro clay could contribute to the landward increase in amplitude of the carbon isotope excursion in bulk carbonate data a plausible trigger for the initial conflagration is a fireball from the impact of a sizable extraterrestrial object at moderate range

regional gravity decrease after the 2010 maule chile earthquake indicates large scale mass redistribution 1 we report small but detectable changes in the grace satellites relative trajectory after the m8 8 maule chile earthquake on 27 february 2010 that can be used to delineate the shift in the gravity field a gravity anomaly of 5 gal with a spatial scale of 500 km was found east of the epicenter after the earthquake based on coseismic models the long wavelength negative gravity change is primarily the result of crustal dilatation as well as surface subsidence in the onland region the offshore positive gravity anomaly predicted from finite fault coseismic models is considerably smaller because the gravity changes due to surface uplift and interior deformation are opposite in polarity our study suggests a role for large scale gravity observations in deciphering changes of the earth s interior during great earthquakes by filling in the seldom observed long wavelength spectrum of earthquake deformations as a complement to surface geodetic measurements and seismic data

upper anisian to lower carnian magnetostratigraphy from the northern calcareous alps austria we present a magnetostratigraphic study of three pelagic limestone sections gamsstein mendlingbach and mayerling from the eastern part of the northern calcareous alps together these sections which contain a rich conodont fauna yield a sedimentary record encompassing the uppermost anisian the ladinian and the lower carnian thermal demagnetization and isothermal remanent magnetization experiments indicate that the magnetization is essentially carried by a mineral of the magnetite family the high unblocking temperature components isolated from the three sections provide clear magnetic polarity zonations correlations between these results based on the biostratigraphic data and tephrochronology allow the construction of a composite magnetic polarity sequence from the illyrian substage upper anisian to the julian 2 zone lower carnian this sequence contains 17 well defined polarity reversals and eight more poorly defined intervals correlations can be suggested between the new data and other magnetostratigraphic results previously obtained from marine sections we estimate that the magnetic reversal frequency was 2 5 to 3 6 reversals per million years during the ladinian

global carbon cycle perturbations triggered by volatile volcanism and ecosystem responses during the carnian pluvial episode late triassic abstract the carnian pluvial episode cpe was a dramatic climatic event during the early late triassic the cpe has been recognized worldwide and is marked by the termination of carbonate platform successions and by pronounced negative 13c excursions denoted as the cpe excursion the onset of the cpe has been proposed to be linked with the volatile eruption of the wrangellia large igneous province w lip however this extreme climatic event remains disputed in terms of its precise global correlation timing of onset duration and global magnitude we compiled a database of 13 conodont biozone controlled stable isotope reference sections throughout the tethyan region after a reexamination of previously published conodont taxonomy from each section the statistics on the conodont assemblages zones yield a global set of 17 high resolution conodont unitary association zones uazs spanning the entire carnian successions a set of age tie points placed an age model on this global uaz scale we added paired 13ccarb and 13corg data from two sections in south china to other records in this global database and then normalized all carbon isotope datasets a pronounced negative 13ccarb excursion with a magnitude of 2 0 5 from an average of 3 to 1 is evident in these normalized trends and is recognized around the entire tethys realm the cpe excursion coincides with conodont uaz 4 234 ma through uaz 8 within the mazzaella carnica and paragondolella praelindae zones julian2 and has a duration of ca 1 5 myr we note that an apparent delayed onset of the cpe excursion in south china relative to elsewhere in the tethys as suggested by previous studies may have been an artifact caused by incomplete conodont stratigraphic records and or irregularities in taxonomic identification a carbon and phosphorus cycle model highlight the strong relationship between the eruption of the w lip and cpe excursion however the estimated amount of co2volatiles released by the w lip would directly account for only 25 of the total amount of light carbon required to explain the combined magnitude and duration of the global cpe excursion

demise of late triassic sponge mounds along the northwestern margin of the yangtze block south china related to the carnian pluvial phase upper triassic carnian marine successions in the northwestern margin of upper yangtze region sichuan basin china show a lithological change from grey oolitic into a sponge mound limestone units 1 and 2 of the lower member of the ma antang formation then overlain by greyish black to dark grey sandy shale and siltstone units 3 and 4 of the upper member of the ma antang formation siliceous sponge mounds were built by hexactinellida and this succession was examined in three localities jushui section in anxian js and guanyinya hwg and qingyangou sections hwq in hanwang mianzhu the conodont quadralella polygnathiformis confirms a carnian age for the biolithite and oolitic limestone of the lower ma antang formation abundant ammonoids identified as belonging to the discotropitid and juvavitid families suggest a tuvalian 1 early late carnian age for the lowermost part of the greyish black sandy shale that overlies the sponge mound at the jushui section field investigations and microfacies analysis suggest that sponge mounds had two stages of growth in relatively deeper water with low energy the first sponge growth mound stage ended in a regional karstified omission surface and was followed by a sudden increase of siliciclastic input greyish black shales containing plant fossils cover a second upper carnian sponge mound stage which is mainly recorded in hwg the onset of these shales may be related to the carnian pluvial phase cpp documented in the western tethys region e g in italy austria and hungary the demise of the sponge mounds at all three sections may have been triggered by the joint effect of climatic changes associated with the fresh water input caused by cpp and with a relative sea level change caused by local tectonic movements in the course of the indosinian orogeny

fore arc basin deformation in the andaman nicobar segment of the sumatra andaman subduction zone insight from high resolution seismic reflection data the andaman nicobar region is the northernmost segment of the sumatra andaman subduction zone and marks the western boundary of the andaman sea which is a complex active back arc extensional basin we present the interpretation of a new set of deep seismic reflection data acquired across the andaman nicobar fore arc basin from 8 n to 11 n in order to better understand its structure and evolution focusing on 1 how obliquity of convergence affects deformation in the fore arc 2 the nature and role of the diligent fault df and 3 the eastern margin fault emf despite the obliquity of convergence back thrusting and compression seem to dominate the andaman nicobar fore arc basin deformation the df is primarily a back thrust and corresponds to the mentawai and west andaman fault systems farther in the south along sumatra the df is expressed in the fore arc basin as a series of mostly landward verging folds and faults deforming the early to late miocene sediments the df seems to root from the boundary between the accretionary complex and the continental backstop where it meets the emf the emf marks the western boundary of the fore arc basin it is associated with subsidence and is expressed as a deep piggyback basin containing recent pliocene to pleistocene sediments the eastern edge of the fore arc basin is the invisible bank ib which is thought to be tilted and uplifted continental crust subsidence along the emf and uplift and tilting of the ib seem to be related to different opening phases in the andaman sea

the june 2010 nicobar earthquake fault reactivation on the subducting oceanic plate the similar to 1300 km long rupture zone of the 2004 andaman sumatra megathrust earthquake continues to generate a mix of thrust normal and strike slip faulting events the 12 june 2010 m w 7 5 event on the subducting plate is the most recent large earthquake on the nicobar segment the left lateral faulting mechanism of this event is unusual for the outer rise region considering the stress transfer processes that follow great underthrusting earthquakes another earthquake m w 7 2 with a similar mechanism occurred very close to this event on 24 july 2005 these earthquakes and most of their aftershocks on the subducting plate were generated by left lateral strike slip faulting on north northeast south southwest oriented near vertical faults in response to north northwest south southeast directed compression pre 2004 earthquake faulting mechanisms on the subducting oceanic plate are consistent with this pattern post 2004 left lateral faulting on the subducting oceanic plate clusters between 5 degrees n and 9 degrees n where the 90 degrees e ridge impinges the trench axis our study observes that the subducting plate off the sumatra and nicobar segments behaves similarly to a chip of the india australia plate deforming in response to a generally northwest southeast oriented compression an aspect that must be factored into the plate deformation models

sedimentology clay mineralogy and palaeosols of the mid carnian pluvial episode in eastern spain insights into humidity and sea level variations this study examines rainfall variations of the mid carnian pluvial episode cpe based on the continental fluvial sedimentology palaeosol and clay mineralogy records of the stable meseta e spain in the formation examined manuel fm or k2 fm the cpe is represented by three regressive transgressive sequences r t or subunits k2 1 k2 2 and k2 3 from base to top each subunit broadly consists of a genetic stratigraphic sequence bearing well developed highstand lowstand and transgressive system tracts hst lst and tst hydromorphic features in the palaeosols suggest changes in the activity of both ground and surface waters the clay mineral assemblage is dominated by illite with a minor presence of kaolinite and traces of smectite in some samples after ruling out tectonism in the study area climate and eustatism emerge as the main allogenic controls in the sedimentary record differentiated sedimentary facies and architectural elements in the k2 2 subunit were likely controlled by both a more humid climate and source area while k2 1 and k2 3 were more related to base level changes and eustatic control the presence of more waterlogged pedotypes and of kaolinite and traces of smectite in the clay mineral assemblage of k2 2 also indicates increased humidity notwithstanding our data do not point to intense rainfall periods for the cpe in e spain

a tethys wide mid carnian upper triassic carbonate productivity crisis evidence for the alpine reingraben event from spiti indian himalaya abstract a significant mid carnian lithological change from carbonatic to siliciclastic sedimentation is described from the spiti himalaya n india the recorded sudden increase of terrigenous influx occurs at the boundary from the chomule to the rama formation it is dated within the late lower carnian uppermost aonoides zone and isochronous all over the tethys himalaya bio and chemostratigraphic data point to a synchrony with changes in carbonate productivity known from on area of wide extent along the nw tethys the reingraben event of the northern calcareous alps austria defines a regional decline in carbonate productivity related to both a platform demise and enhanced siliciclastic input laminated shales found in a distal part of the spiti basin document the onset of anoxic conditions within the deeper shelf synchronous to the reingraben event in austria high resolution biostratigraphy and identical 13ccarb curves are therefore in support of a direct link between the change in spiti and the reingraben event our data combined with a comprehensive review of previously postulated scenarios regarding the reingraben event suggest linking of climatic change with siliciclastic input and a carbonate productivity crisis initiated by onset of a relatively humid megamonsoonal late lower carnian atmospheric system that affected both the southern and northwestern tethys and point to a supra regional trigger of the alpine reingraben event

indian ocean actively deforms according to plate tectonics plates are rigid and deform only at narrow boundaries but studies have shown that intraplate deformation can occur in continental plates in her perspective deplus discusses recent evidence for active deformation in the indian ocean offering a rare opportunity to study intraplate deformation of oceanic lithosphere

aftershock investigation in the andaman nicobar islands of india and its seismotectonic implications six three component short period digital seismograph four reftek and two kinemetrics stations were established in different parts of the andaman nicobar islands following the 26 december 2004 devastating sumatra andaman mainshock m w 9 3 here we analyze about 18 000 aftershocks m 3 0 recorded from 6 january to 16 march 2005 to better understand the seismotectonics of the region a sudden burst of aftershock activity with irregular trend in the month of january 2005 was observed at almost all seismograph stations the estimate of p value 0 9532 from aftershocks m 4 5 is near to normal value of 1 0 which suggests a slow decay sequence of aftershock with complex and nonuniform stress change in a fault system creep effects and history dependent stress changes the frequency magnitude relation of the aftershocks followed the power law with average b value of 0 7723 and it varies from 0 49 to 1 03 indicating the compressive stress state of the region and its heterogeneous structure with possible variations in frictional conditions along the fault the distribution of the located aftershocks by a multistation method shows a north south trending aftershock cluster in an area of about 800 300 km 2 which reflects an approximate rupture dimension of the mainshock beneath the andaman nicobar islands most of aftershocks occurred in a depth range of 5 65 km the determination of composite fault plane solutions of the best located aftershock clusters at three different depth ranges 0 15 16 30 and 31 km in the ten blocks of the region suggests that the mainshock rupture propagated through normal reverse and strike slip earthquakes the areas in the vicinity of barren and narcondum volcanic zones show a dominantly normal fault mechanism due to predominant tensional forces suggesting the facilitation of brittle failure in the weakened crust by the process of underheating the zone near baratang mud volcano is associated predominantly with thrust fault at depth of 0 30 km suggesting a high compressive force beneath the baratang that ejected a huge amount of mud and slurry materials to the surface after the 26 december 2004 sumatra andaman earthquake m w 9 3 here we propose that the relocation of our large aftershock dataset using converted sp depth phase technique for precise depth control is needed and its sharing with global earthquake data can render more information on the subduction dynamics and geodynamical processes of the region

implications of postseismic gravity change following the great 2004 sumatra andaman earthquake from the regional harmonic analysis of grace intersatellite tracking data 1 we report gravity recovery and climate experiment grace satellite observations of coseismic displacements and postseismic transients from the great sumatra andaman islands thrust event mw 9 2 earthquake in december 2004 instead of using global spherical harmonic solutions of monthly gravity fields we estimated the gravity changes directly using intersatellite range rate data with regionally concentrated spherical slepian basis functions every 15 day interval we found significant step like coseismic and exponential like postseismic behavior in the time series of estimated coefficients from may 2003 to april 2007 for the spherical slepian functions after deriving coseismic slip estimates from seismic and geodetic data that spanned different time intervals we estimated and evaluated postseismic relaxation mechanisms with alternate asthenosphere viscosity models the large spatial coverage and uniform accuracy of our grace solution enabled us to clearly delineate a postseismic transient signal in the first 2 years of postearthquake grace data our preferred interpretation of the long wavelength components of the postseismic gravity change is biviscous viscoelastic flow we estimated a transient viscosity of 5 1017 pa s and a steady state viscosity of 5 1018 1019 pa s additional years of the grace observations should provide improved steady state viscosity estimates in contrast to our interpretation of coseismic gravity change the prominent postearthquake positive gravity change around the nicobar islands is accounted for by seafloor uplift with less postseismic perturbation in intrinsic density in the region surrounding the earthquake

on the mechanism of tectonic transport in zones of oblique subduction abstract many cases of oblique subduction are known throughout the world today and many more must have existed in the past in at least one modern case sumatra the over riding plate has responded to oblique subduction by forming a strike slip fault that traverses the magmatic arc and displaces its leading edge in the direction of the transverse component of oblique convergence conditions favoring this sort of tectonic response are shown to be 1 1 a high angle of oblique convergence 2 2 a low angle of subduction and 3 3 relative thermal softening of the magmatic arc this mechanism may have been responsible in part for northward transport of western cordilleran magmatic arc and subduction zone rocks in the late cretaceous and earliest tertiary it also may help to explain evidence of southward transport and left lateral shear in northern mexico and the caribbean region in pre jurassic time

a diffuse plate boundary model for indian ocean tectonics it is suggested that motion along the virtually aseismic owen fracture zone is negligible so that arabia and india are contained within a single indo arabian plate divided from the australian plate by a diffuse boundary the boundary is a zone of concentrated seismicity and deformation commonly characterized as intraplate the rotation vector of australia relative to indo arabia is consistent with the seismologically observed 2 cm yr of left lateral strike slip along the ninetyeast ridge north south compression in the central indian ocean and the north south extension near chagos

the april 2012 indian ocean earthquakes seismotectonic context and implications for their mechanisms the 11 april 2012 earthquakes m w 8 6 and m w 8 2 were sourced within the northern wharton basin in the northeastern part of the indo australian diffuse plate boundary this unusually active oceanic intraplate region has generated many large earthquakes in the past most of which are believed to have occurred by strike slip motion triggered by the nw se oriented compressional stresses acting across the indian and australian plates in the aftermath of the 2004 megathrust earthquake along the nearby sunda trench increased seismicity in the northern wharton basin is attributed to the stress transfer from the sumatra andaman plate boundary models proposed for the april 2012 earthquakes differ somewhat in details but partly attribute their complex rupture to the reactivation of pre existing structures these structures include previously mapped n s trending fracture zones within the northern wharton basin and e w lineations across the ninetyeast ridge in this paper we review the regional tectonics and past seismicity on the indo australian plate in order to understand the seismotectonic setting of the april 2012 indian ocean earthquakes c 2014 elsevier b v all rights reserved

perturbations in the carbon cycle during the carnian humid episode carbonate carbon isotope records from southwestern china and northern oman the carnian humid episode is an interval of prominent climatic changes in the late triassic we studied the carbon isotope 13c geochemistry of carbonates from sections in southwestern china and northern oman 13c records from the yongyue section western guizhou south china show a progressive positive shift from 1 4 to 2 8 in the early to middle julian 1 substage this positive trend is followed by a swift negative shift of c 4 2 from 2 8 to 1 4 in the julian 2 substage 13c from the wadi mayhah section northern oman shows a positive shift from 2 2 to 2 8 in the julian 1 substage followed by a negative shift of c 3 2 from 2 8 to 0 3 in the julian 2 substage the 13c records from the two study sections generally correlate well with each other as well as with published records pointing to a considerable input of isotopically light carbon starting in the late julian 1 substage such a large amount of light carbon probably derived from direct degassing and the sediment sill contact metamorphism of the panthalassan wrangellia large igneous province and contemporary tethyan volcanism the voluminous volcanogenic greenhouse gases probably contributed to the warming pulse in the middle carnian thus the dry wet climatic transition during the carnian humid episode is best interpreted as a warm climate driven intensification of the activities of the atmospheric circulation and hydrological cycle