garnet and tourmaline as provenance indicators of terrigenous material in epicontinental carbonates middle triassic s poland abstract heavy mineral grains contained in epicontinental carbonates are very rarely used for provenance analysis this study deals with detrital heavy minerals separated from marly limestones and marlstones of the gogolin formation gf middle triassic s poland to determine their source rocks and alimentary areas the gf carbonates typically contain 1 wt of heavy minerals within the very fine sand fraction the heavy mineral assemblages consist predominantly of garnets 53 0 92 2 and tourmalines 3 8 30 4 epma analyses reveal four groups of garnets low grs almandines with 30 50 mol prp almandines with 20 35 mol prp and up to 35 mol grs almandines with up to 20 mol sps and rare pyrope grains 60 mol prp the composition of the garnets indicates that hp felsic granulites were their main source rocks but more mafic hp rocks eclogites retrograded eclogites and mafic granulites gneisses mica schists and garnet peridotites also contributed the detrital tourmalines are represented mainly by dravite and less frequently by schorl which were derived mostly from paragneisses and mica schists and in minor part from granitoids and pegmatites the e ne part of the bohemian massif is the most probable location of the source rocks the presumed source rocks presently outcrop in the moldanubian zone the kutna hora unit the svratka unit and the gory sowie massif nowadays the bodies formed by the hp rocks within these units are insufficiently large to act as sources for delivering detrital material in the determined proportions the high content of hp metamorphic grains thus indicates the past existence of extensively exposed and abundant high pressure metamorphic rocks eroded during and or after the middle triassic

an analysis of apparent polar wander path for southwest japan suggests no relative movement with respect to eurasia during the cretaceous abstract to test the hypothesis that southwest japan was involved in large scale tectonic movement with southward translation as far as 2000 km with respect to eurasia during the cretaceous we examined cretaceous paleomagnetic poles from southwest japan to compare with those from eurasia red and gray sandstone samples from the upper cretaceous onogawa group were collected from twelve sites in the onogawa basin in the western part of southwest japan for paleomagnetic analysis this group formed over the time span in which the proposed tectonic event is hypothesized to have occurred a characteristic remanent magnetization component was isolated from red sandstone at ten sites it is interpreted to be of primary late cretaceous origin the primary directions combined with previously reported data provide a mean direction d 76 8 i 44 6 95 11 1 n 15 and a paleomagnetic pole 24 4 n 202 6 e a95 11 0 for the onogawa area this pole is consistent with other late cretaceous poles from a wide area of southwest japan and a mean late cretaceous pole 28 4 n 202 5 e a95 7 5 n 6 is calculated and regarded as representative of this region the late cretaceous pole together with mid and early cretaceous poles constitutes an apparent polar wander path apwp for southwest japan during the cretaceous after restoration of post cretaceous tectonic rotation each cretaceous pole for southwest japan shows agreement with the coeval poles for eurasia therefore it is unlikely that the previously proposed tectonic model that includes southward translation of southwest japan occurred in the late cretaceous southwest japan is considered to have behaved as a stable part of the eurasian continental margin during the cretaceous

surface rupture of the 2005 kashmir pakistan earthquake and its active tectonic implications to provide a detailed record of a relatively rare thrust surface rupture and examine its active tectonic implications we have conducted field mapping of the surface rupture associated with the 2005 m w 7 6 kashmir earthquake despite the difficulty arising from massive earthquake induced landslides along the surface rupture we found that typical pressure ridges and warps extend northwestward for a distance of 70 km with a northeast side up vertical separation of up to 7 m neither the main frontal thrust nor the main boundary thrust is responsible for the earthquake but three active faults or fault segments within the sub himalaya collectively called the balakot bagh fault compose the causative fault although the fault exhibits substantial geomorphic expression of repeated similar surface ruptures only a part of it had been mapped as active before the earthquake the location of the hypocenter suggests that the rupture was initiated at a deep portion of the northern central segment boundary and propagated bilaterally to eventually break all three segments our obtained surface rupture traces and the along strike slip distribution are both in good agreement with results of prompt analyses of satellite images indicating that space geodesy can greatly aid in time consuming field mapping of surface ruptures assuming that the extensive fill terrace in the meizoseismal area was abandoned during 10 30 ka we tentatively estimate the earthquake recurrence interval and shortening rate on the balakot bagh fault to be 1000 3300 yr and 1 4 4 1 mm yr respectively these estimates indicate that the balakot bagh fault is not a main player of himalayan contraction accommodation graphic 1 selected field photographs and arcgis files of the mapped surface rupture traces and measured vertical separations are available in the electronic supplement to this article 1 embed inline graphic 1 gif

peridotite derived detrital pyropes versus high pressure felsic granulite derived pyrope almandine garnets from the lower triassic deposits of the ne foreland of the bohemian massif s poland central europe

formation and evolution of the tancheng lujiang wrench fault system a major shear system to the northwest of the pacific ocean abstract in the northwestern peri pacific tectonic belt on the continental margin of east asia there is a series of major faults trending ne nne i e the tancheng lujiang wrench fault system this fault system extends more than 5000 km with a width of 800 1000 km in the continent and a general strike of n30 e on the basis of the results of special research on the major faults and a lot of new information about the fault system the authors discuss early mesozoic triassic jurassic period sinistral transcurrent faulting in the different regions it is suggested that in the eastern continent of east asia the e w trending tectonic pattern of the paleozoic and beginning of the mesozoic appear in the nuclei of the sino korean continent massif and the yangtze continent massif these ancient continent massifs accreted both southwards and northwards which finally led to their collision and suturing to the angura continent massif later this tectonic framework was changed greatly by the tancheng lujiang wrench fault system along which left lateral horizontal displacement of 1000 1500 km took place since the mesozoic the dislocation and deformation of horizontal displacement of the tancheng lujiang fault system produced a series of structures trending ne nne in the continental margin which have greatly transformed the ancient structures of the preceding mesozoic this is an important diktyogenese in the continent of east asia during the horizontal displacement motion of these faults the folds nappes and decollement structures pull apart basins and subductions within the continent occurred in the continent at the same time some large sinistral ductile shear zones of horizontal displacement appeared the depth of the deformed horizon of ductile shear which belongs to simple shear was controlled by the tectonic element and distance away from the continental margin whilst the ductile shear deformation occurred the fault dynamo thermal metamorphism and the fault remelting took place and magma activity appeared within the continent in the mesozoic the fault zones used to be high energy zones and recently became the seismic belts within the continent formation of the tan lu fault system was due to the collision between the southern and northern blocks its large sinistral horizontal displacement in the mesozoic was closely related to the kula plate moving northwards therefore the continent disintegrated by shearing which produced some new terranes the shear edge belt was formed between the continent and ocean the change of relative motion between the continent and pacific ocean plate transformed the tan lu fault system into first extension and then compression clarifying the characteristics of the tan lu fault system is an important key in understanding the evolution of the east asia continent since the mesozoic

partitioning of convergence in northwest sub himalaya estimation of late quaternary uplift and convergence rates across the kangra reentrant north india the kangra reentrant constitutes a 80 km wide zone of fold thrust belt made of cenozoic strata of the foreland basin in nw sub himalaya earlier workers estimated the total long term shortening rate of 14 2 mm year by balanced cross section between the main boundary thrust and the himalayan frontal thrust geologically estimated rate is nearly consistent with the gps derived slip rate of 14 1 mm year there are active faults developed within 4 8 km depth of the sub himalayan fold thrust belt of the reentrant dating the strath surfaces of the abandoned fluvial terraces and fans above the thrust faults the uplift bedrock incision rates are computed the dips of thrust faults are measured in field and from available seismic depth profiles from the acquired data late quaternary shortening rates on the jawalamukhi thrust jt the soan thrust st and the himalayan frontal thrust hft are estimated the shortening rates on the jt are 3 5 4 2 mm year over a period 32 30 ka the st yields a shortening rate of 3 0 mm year for 29 ka the corresponding shortening and slip rates estimated on the hft are 6 0 and 6 9 mm year during a period 42 ka on the back thrust of janauri anticline the shortening and slip rates are 2 0 and 2 2 mm year respectively for the same period the results constrained the shortening to be distributed largely across a 50 km wide zone between the jt and the hft the emergence of surface rupture of a great and mega earthquakes recorded on the reactivated hft implies 100 km width of the rupture the ruptures of large earthquakes like the 1905 kangra and 2005 kashmir remained restricted to the hinterland the present study indicates that the high magnitude earthquakes can occur between the locking line and the active thrusts

great earthquake surface ruptures along backthrust of the janauri anticline nw himalaya abstract results of a paleoseismic trenching investigation on a backthrust in the northern margin of janauri hill at mehandpur 31 18 11 37 n 76 18 31 47 e sub himalayan range of the himachal himalaya are presented the active backthrust revealed the last event took place after 0 8 0 03 ka ago i e post ce 1200 the age of the last earthquake with a minimum fault slip 1 m along f1 fault and presence of single colluvium on the back thrust nearly matches with an earthquake event previously documented on the bhatpur forethrust of the himalayan frontal thrust system uplifted and truncated fluvial terraces due to displacement on the backthrust are preserved along several north flowing river valley sections in the northern limb of janauri anticline the long term vertical uplift rate calculated through dividing difference between current elevation and elevation of current river grade is 1 08 0 08 mm yr field evidence shows fore and backthrusts are active and they form simultaneously but displacements are episodic suggesting the backthrust develops either due to locking of forethrust or to accommodate a large amount of fault slip due to magnitude of earthquake event along the forethrust further the backthrust may be used as an indirect method of inferring the age of the last event that took place along the forethrust

an early jurassic oligohaline ostracod assemblage within the marine carbonate platform sequence of the venetian prealps ne italy boomer i whatley r bassi d fugagnoli a loriga c 2001 an early jurassic oligohaline ostracod assemblage within the marine carbonate platform sequence of the venetian prealps ne italy palaeogeography palaeoclimatology palaeocology 166 3 4 331 344

recurrence of large paleo earthquakes in kashmir himalaya seismic gap riasi area india abstract in kashmir himalaya the medlicott wadia thrust is a main active fault responsible for the crustal accretionary prism building during the late quaternary because of the long seismic silence during the last five centuries it is a key structure to be studied in order to estimate the regional seismic hazard in the riasi area the analysis of two paleoseismological trenches allowed us identifying and measuring several seismic ruptures over the last 3500 years we determined that the oldest rupture occurred around 1600 1000 bc while the youngest occurred after 1470 ad the latest event is compatible with the great 1555 ad mw 7 5 kashmir earthquake whose evidence at the surface had not yet been recognized our results show that despite the long lasting seismic gap the medlicott wadia thrust is a main seismogenic structure in the region able to produce large earthquakes their recurrence interval ranges between 500 and 700 years implying that a main seismic event could occur in the next decades these seismic ruptures are localized over gently dipping fault branches associated with decameter scale scarps the morphologies observed are due to a significant non localized component of the deformation in quaternary sediments

ecostratigraphic trends of jurassic agglutinated foraminiferal assemblages as a response to sea level changes in shelf deposits of svalbard norway foraminiferal analysis proves to be a useful tool for the interpretation of major factors controlling the eco sedimentary environment changes in benthic foraminiferal features including morphogroups are mainly affected by variations in nutrient availability and oxygenation rate the integration of foraminiferal data with total organic carbon toc values together with differentiation of oxygen restricted biofacies orb based on sedimentological features and macroinvertebrate composition will improve the interpretations derived upper jurassic shelf deposits from svalbard norway are revealed to be particularly sensitive to the record of fluctuations in nutrients and oxygenation showing two extreme cases in toc content high toc concentrations are characterized by low values of the shannon weaver index h and diversity index in foraminifera pointing to a low diversity and dominance of r mode epifaunal foraminifera trochammina moreover differentiated orb can be characterized by parallel lamination in shales and an absence of macrobenthic invertebrates including trace fossils unfavourable benthic conditions are interpreted mainly related with a high consumption of oxygen by microbes in the sediment associated to the degradation of the organic matter low toc values are related to higher values of diversity h and diversity index and foraminiferal assemblages dominated by infaunal forms the differentiated orbs are characterized by coarse fabrics scarcity or absence of parallel lamination presence of trace fossils and abundance of macroinvertebrate shelly epifauna this is related to a better pore water circulation and higher oxygenation degree congruent with the comparatively more favourable conditions in the infaunal habitats ecostratigraphic trends along the studied section allow the differentiation of stratigraphic intervals reflecting variations in parameters related to the sea level dynamics transgressive phases reveal upward trends in palaeoenvironmental parameters characterized by decreasing grain size and increasing in both toc values and epifaunal foraminifera differentiated orb reveals diminution in abundance and diversity of trace fossils and benthic shelly macroinvertebrates upwards maximum flooding intervals show the maintenance or accentuation of the previously registered features the thinnest fabrics and the highest values in toc and in opportunistic epifaunal foraminifera with orb dominated by parallel lamination a regressive phase is characterized by coarsening upwards sediments decreasing toc values and increasing infaunal foraminifera orb reveals a diminution in parallel lamination together with an increase in trace fossil abundance and diversity as well as in benthic shelly macroinvertebrates

structure and shortening of the kangra and dehra dun reentrants sub himalaya india surface geology oil well seismic reflection and magnetostratigraphic data are integrated to evaluate the structural style and the shortening rate at the himalayan front sub himalaya of northwest india the sub himalaya between the main boundary thrust and the himalayan frontal fault is the primary surface expression of shortening between the himalaya and the indian plate at certain locations the himalayan frontal fault is a blind thrust beneath anticlines of siwalik tertiary molasse parallel to the himalayan orogen the main boundary thrust is sinuous so the width of the sub himalaya ranges from 30 to 80 km where the sub himalaya is narrow nahan salient tertiary rocks are exposed in imbricate thrust sheets where the sub himalaya is broad kangra and dehra dun reentrants alluvium fills wide synclinal valleys duns seismic reflection data reveal that surface anticlines form in association with south vergent thrusts that root in a decollement at the base of the tertiary section reflection profiles and well data also indicate that the basement lithology changes northward from precambrian crystalline rocks beneath the indo gangetic plains to precambrian and cambrian metasedimentary rocks beneath the sub himalaya the sub himalayan decollement dips 2 5 northward beneath the kangra reentrant but it is steeper 6 beneath the dehra dun reentrant the kangra and dehra dun reentrants display fault propagation folds having steep limbs in the north and fault propagation and fault bend folds that have gently north dipping limbs in the south a balanced cross section of the kangra reentrant shows that a minimum of 23 km shortening has occurred since 1 9 1 5 ma yielding a shortening rate of 14 2 mm yr shortening has occurred at a rate of 6 16 mm yr across the dehra dun reentrant these data are similar to other published shortening rates and indicate that approximately 25 of the total india eurasia convergence at this longitude is accommodated within the sub himalaya given continued convergence and the presence of overpressured wells in the kangra reentrant the region is likely at risk from moderate and or great earthquakes in the future

implications of mylonitic microstructures for the geotectonic evolution of the median tectonic line central japan the median tectonic line mtl the most prominent onshore fault in japan demarcates the cretaceous hiji quartz dioritic gneiss of the ryoke belt on the west from the high p t type sambagawa metamorphic rocks on the east in the takato area toward the mtl the hiji gneiss grades into strongly mylonitized rocks characterized by grain size reduction of quartz in the mylonitic rocks the development of fluxion banding sm is remarkably influenced by the existence of k feldspar forming a myrmekitic intergrowth brittle microstructures indicative of truly cataclastic deformation are observed only in mylonitic rocks close to the mtl early deep level ductile deformation apparently gave way to shallower brittle deformation at a later stage the attitude of stretching lineations lm and asymmetric microstructures observed in the mylonites suggest that sinistral strike slip shearing with a subordinate component of vertical slip took place during mylonitization in mid cretaceous time the mylonitic rocks and their protolith supposed to have constituted the eastern limb of the shear zone were probably eroded out and lost by upheaval of the sambagawa belt relative to the ryoke belt

distribution of the late quaternary deformation in northwestern himalaya abstract three main cenozoic thrusts at the front of northwestern himalaya have accommodated most of the india eurasia convergence across the belt over the last million years and produced the present relief their recent tectonic activity is poorly known because of the long period of inaccessibility of the jammu and kashmir state and because the latest and only large earthquake recorded in the region occurred in 1555 ad we show where the deformation is localized during the late quaternary and determine shortening rates across the structures by analyzing the geometry and chronology of geomorphic markers the main boundary thrust in this region ceased moving at least 30 ka ago on the contrary the more external medlicott wadia thrust and main frontal thrust both merging at depth on the sub flat detachment of the main himalayan thrust exhibit hectometric scale deformations accumulated during the last thousands of years the total shortening rate absorbed by these faults over the last 14 24 ka is between 13 2 and 27 2 mm yr 11 2 3 8 and 9 0 3 2 mm yr respectively part of this deformation may be associated to the geometry of the chenab reentrant which could generate an extra oblique component however the lower bound of our shortening rates is consistent with previously determined geodetic rates active deformation on these structures follows an in sequence out of sequence pattern with breaking of both ramps being possible for earthquakes triggered on the main detachment

carbon isotope anomalies and demise of carbonate platforms in the sinemurian early jurassic of the tethyan region evidence from the southern alps northern italy despite its global impact on ecosystems the triassic jurassic boundary event had only a modest effect on the carbonate depositional systems of the southern alps whereas a fundamental reorganization of the same palaeogeographic area took place during the sinemurian age this paper investigates whether or not the well documented demise of sinemurian carbonate platforms in the tethyan region was a response to a global event by examination of carbon isotope anomalies in successions of different facies that record this interval of time a chemostratigraphic transect from lake garda up to the eastern italian border is illustrated by four stratigraphic sections high resolution 20 cm over key intervals chemostratigraphic sampling allowed detection of a major negative 13 c anomaly of 1 5 preceded by a positive excursion both in shallow and deep water successions over the stratigraphical range of the ammonite genus arnioceras a comparison with sections from the uk suggests that the positive excursion belongs to the turneri zone and the succeeding negative excursion falls within the obtusum zone in the deep water belluno basin the negative anomaly occurs in a biogenic chert rich unit recording the onset of mesotrophic conditions in the basin in the platform carbonate successions this major negative carbon isotope excursion is developed within a calcarenitic unit corresponding to the lowest occurrence of the foraminifer paleomayncina termieri this evidence for deepening and transgression across the carbonate platform suggests pre conditioning for drowning hence rather than tectonic subsidence alone environmental factors may have aided the demise of tethyan carbonate platforms during the early jurassic sinemurian age

geomorphic evidence of unrecognized balapur fault segment in the southwest kashmir basin of northwest himalayas abstract the balapur fault bf is a high angle thrust fault reverse dipping 60 ne with an established length of 40 km striking nw se of the kashmir basin however geomorphic traces suggest that the strike of the bf propagates beyond what has been documented previously the present investigation aims to identify the unrecognized segment of the bf in the sw of the kashmir basin using hypsometric variability in longitudinal profiles knickpoints zones followed by validation through stream gradient index sl calculations of the rivers draining the area the longitudinal profiles of all the streams indicate prominent and consistent anomalies in the upper and mid reaches even on the coarse resolution data survey of india topographic maps 1 50 000 40 m dem srtm 90 m the profile anomalies in the upper reaches hard rock zone of the streams may be attributed to lithological contacts i e panjal trap agglomeratic slate shale limestone however the river profile convex segments and course deflection specifically in the mid reaches soft rock zone are most likely associated with recent tectonic activity geomorphic signatures suggest that these anomalies coincide with the strike of the recognized segment of the bf moreover the sl values of each stream express a clear agreement with the anomalies shown by the long profiles of the rivers hence we infer that the strike of the bf extends for a significant distance 95 km over the northeastern flank of the pir panjal range in the nw se direction

seismotectonics of the kangra region northwest himalaya abstract the occurrence of major and moderate earthquakes having thrust and strike slip mechanism along the longitudinal and transverse feature within the same seismogenic zone requires us to study the area in detail to infer the seismotectonics the epicentral distribution of earthquakes 4 0 mb between chamba and sundernagar region shows the high rate of activity either north of chamba i e north of the main central thrust mct or north of dharamsala in between the panjal thrust pt and mct in the dhauladhar range it is however surprising that all the moderate earthquakes that have triggered in the kangra region have either been in the frontal belt along the transverse features or have followed the arcuate belt close to the main boundary thrust mbt the spatio temporal variation of the seismicity from 1973 to 2000 4 0 mb reveals a migration trend between chamba and sundernagar during the seventies and early eighties the seismicity was concentrated in the chamba region and in the late eighties and early nineties the seismicity shifted around dharamsala and later further north in this arcuate tectonic belt of the chamba sundernagar region the foreland region has a characteristic tectonic setting all the fault and fold structures in the oligocene miocene and neogene pliestocene sediments in the foreland region show relative movement in the area of transverse tectonics the surface structures i e thinning and thickening of the sediments are controlled by the basement cofiguration controlled by the subduction process the mbt and the pt are closely spaced and meet each other just northwest of dharamsala the width of the lesser himalaya in the chamba sundernagar region is also much narrower as compared to the region in the east in garhwal kumaun and western nepal this suggests that the convergence is taken up largely by underthrusting of the lesser himalayan formations along the pt the occurrence of a moderate earthquake of magnitude 6 5 in 1978 and the 1986 dharamsala earthquake along the se dipping and sw dipping nodal planes within the ne dipping thrust regime and displacement of the mbt and pt from 4 to 12 km reflects the active involvement of the ne sw trending fault system in controlling the seismic behavior of the kangra region the microearthquake migration in time and space in the chamba sundernagar region also reflects the time differential segmental collision behavior of the basement

surface deformation in the region of the 1905 kangra mw 7 8 earthquake in the period 1846 2001 1 one century after the mw 7 8 kangra earthquake of 4 april 1905 we report weak constraints on its rupture parameters based on the remeasurement of historic triangulation points in the epicentral region the western corner of the 1905 rupture is constrained to within 20 km and its sw edge strikes n135 15w the down dip width of the rupture is inferred from the location of the interseismic locking line to have been less than 55 km scaling laws and revised msk intensities suggest an along arc rupture length of 100 km with uniform slip of 4 m because the earthquake ruptured 60 of the width of the plate boundary and released a fraction of the inferred slip deficit complacency about its re rupture in the distant future is unwarranted the kangra rupture could fail again today in a mw 7 5 earthquake 1 4 m of slip or as part of a much larger earthquake mw 8 6

co seismic secondary surface fractures on southeastward extension of the rupture zone of the 2005 kashmir earthquake abstract after the 2005 kashmir earthquake we mapped surface ground fractures in tangdhar uri rajouri and punch sectors and liquefaction features in jammu area lying close to the eastern side of the line of control loc in kashmir india the nw trending ground fractures occurred largely in the hanging wall zone of the southeastern extension of the causative fault in tangdhar and uri sectors the principal compressive stress deduced from the earthquake induced ground fractures is oriented at n10 whereas the causative balakot bagh fault strikes 330 the fault plane solution indicates primarily sw thrusting of the causative fault with a component of strike slip motion the ground fractures reflect pronounced strike slip together with some tensile component the tangdhar area showing left lateral strike slip motion lies on the hanging wall and the uri region showing right lateral strike slip movement is located towards the southeastern extension of the causative fault zone the shear fractures are related to static stress that was responsible for the failure of causative fault the tensile fractures with offsets are attributed to combination of both static and dynamic stresses and the fractures and openings without offsets owe their origin due to dynamic stress in punch rajouri and jammu area which lies on the footwall the fractures and liquefactions were generated by dynamic stress the occurrence of liquefaction features in the out board part of the himalayan range front near jammu is suggestive of stress transfer 230 km southeast of the epicenter the balakot bagh fault bbf the muzaffarabad anticline the rupture zone of causative fault and the zone of aftershocks all are aligned in a 25 km wide belt along the nw se trending regional himalayan strike of kashmir region and lying between the mbt and the riasi thrust murree thrust suggesting a seismogenic zone that may propagate towards the southeast to trigger an earthquake in the eastern part of the kashmir region

tethyan carbonate platform transformations during the early jurassic sinemurian pliensbachian southern alps comparison with the late triassic carnian pluvial episode

a new approach to provenance studies electron microprobe analysis of detrital garnets from middle jurassic sandstones of the northern north sea reading provenance from heavy mineral suites is hampered by the depletion of diagnostic but unstable heavy minerals through intrastratal solution a common phenomenon in deep sedimentary basins such as the north sea this paper demonstrates the potential of electron microprobe analysis in overcoming this problem by concentrating on the compositional variations shown by detrital garnets which are relatively resistant to intrastratal solution studies of the garnets from the brent group middle jurassic of the murchison and tern oilfields in the northern north sea reveal that three distinct areas supplied detritus association 1 which characterizes the broom formation in both areas and recurs higher in the sequence in the tern field is ascribed to an orkney shetland source the location of the areas supplying the garnets of association 2 best represented in murchison and association 3 common to both fields is less clear their ultimate sources clearly include high grade metamorphics and therefore probably lie on the norwegian landmass the orkney shetland platform or conceivably the scottish landmass but the possibility of recycling makes it difficult to judge their immediate provenances nevertheless the presence of three garnet associations indicates that the most widely accepted model of brent sedimentation with sands derived from a domal uplift in the outer moray firth and channelled northward along the viking graben is untenable

benthic foraminiferal assemblages record major environmental perturbations during the late pliensbachian early toarcian interval in the peniche gssp portugal abstract this is the first ecostratigraphic and palaeoecological analysis of the benthic foraminiferal assemblages defined as morphogroups in the pliensbachian toarcian transition and the toarcian oceanic anoxic event t oae of the peniche section the toarcian global boundary stratotype section and point foraminiferal assemblages from the uppermost pliensbachian emaciatum zone reveal the presence of a stable benthic environment with good oxygen and availability of trophic resources as evidenced by the high diversity of specialists the pliensbachian toarcian transition reveals high foraminifera abundance mainly specialists although it is considered a slightly condensed interval the base of the levisoni zone shows dramatic changes in life style of foraminifera increase of epifauna and potentially deep infauna an increase in opportunistic forms and a decrease in diversity these changes suggest unfavourable conditions related to food availability diminution and depleted oxygenation corresponding to the beginning of the 13c negative excursion palaeoenvironmental conditions become severe in the lower to middle levisoni zone where there is a barren interval for foraminifera coincident with the highest values of total organic carbon after this interval foraminiferal assemblages experienced a recovery with increasing diversity and occurrence of specialists consistent with a well oxygenated environment and good food availability these changes observed in benthic foraminiferal fauna from the peniche section through the uppermost pliensbachian lower toarcian are comparable to what was reported previously on ostracods brachiopods and calcareous nannofossils foraminiferal assemblages from peniche section are comparable to other tethyan spain italy north africa and nw european sections england from the same stratigraphic interval with the suborder lagenina dominating the assemblages

redefining medlicott wadia s main boundary fault from jhelum to yamuna an active fault strand of the main boundary thrust in northwest himalaya abstract the mbt demarcates a tectonic boundary between the tertiary sub himalaya and the pre tertiary lesser himalaya south of the mbt another tectonically important fault extends from muzaffarabad and riasi in jammu kashmir to bilaspur and nahan in himachal medlicott and wadia had designated this fault the main boundary fault mbf in simla hills and jammu region respectively in between these two areas later workers gave local area names to the mbf as the riasi thrust in jammu palampur thrust in kangra bilaspur thrust in simla hills and nahan thrust in sirmur we have reviewed and established the tectonostratigraphic framework and physical continuity of the lower tertiary belt and the mbf the lower tertiary belt lying south of the mbt has characteristic tectonostratigraphic setting with discontinuous bodies of stromatolite bearing proterozoic limestone overlain with depositional contact by the paleocene lower part middle eocene marine subathu patala formation which in turn overlain by the upper oligocene lower miocene non marine dharamsala murree formation to avoid confusion with the mbt we designate collectively the mbf and related faults as the medlicott wadia thrust mwt the mwt extends east of hazara kashmir syntaxis to river yamuna covering a distance of 700 km further east of yamuna the lower tertiary belt pinches out and the mwt merges with the sensuo stricto mbt the proterozoic limestone represents the basement over which the lower tertiary sediments were deposited the limestone basement with its cover was detached by the mwt exhuming to the surface and thrusting over largely the siwalik group the reactivated balakot bagh fault causative fault for the 2005 kashmir earthquake extends southeast with right step to the riasi thrust the riasi thrust shows evidence of reactivation and active tectonic activity in jammu region it extends further east to the palampur thrust in kangra reentrant which lies within the 1905 kangra earthquake rupture zone the bilaspur thrust continuation of the palampur thrust shows active faulting south of simla hills between sataun and yamuna river these observations indicate that the mwt represents a southern strand of the sensuo stricto mbt and shows active faulting in some segments

provenance of tertiary sandstone in the northern qaidam basin northeastern tibetan plateau integration of framework petrography heavy mineral analysis and mineral chemistry abstract an exceptionally thick cenozoic sedimentary succession has developed in the qaidam basin of the northeastern tibetan plateau the provenance remains enigmatic thus more precise investigations are needed an integrated study of sandstone framework petrography heavy mineral analysis and mineral chemistry was adopted to perform provenance analysis of the tertiary sandstones in the northern qaidam basin no individual method exists that can provide comprehensive provenance interpretations on spatial and temporal variations based on three types of data three depositional areas can be distinguished sandstones of area a exhibit relatively high abundances of quartz garnet and zircon as well as relatively high textural maturity implying long distance sources multi composition garnets and tourmalines reveal derivations of metasedimentary rocks and intermediate acidic igneous rocks sandstones of area b are rich in metamorphic lithic fragments epidote and garnet a dominance of fe rich garnets with low mg low mn and variable ca contents and dravites demonstrates predominant derivation of metasedimentary rocks therefore the north qaidam and south qilian terranes are potential source areas for these two depositional areas additionally high metamorphic heavy mineral abundances in the upper formations imply increasing contributions of these two metamorphic belts during the tertiary tectonic uplift however sandstones of area c are characterized by relatively high abundances of feldspar igneous heavy minerals and high fe mn garnet which suggest a main source of igneous rocks the altun and qilian mountains are potential source regions furthermore increasing amounts of feldspar and igneous heavy minerals in the upper formations indicate a significant presence of igneous parent rocks which are most likely a response to the multi stage uplift events in the altun mountains since the early eocene

carbonate platform evidence of ocean acidification at the onset of the early toarcian oceanic anoxic event abstract the early toarcian oceanic anoxic event early jurassic 183 myr ago is associated with one of the largest negative carbon isotope excursion cie in the whole phanerozoic 3 7 estimates of the magnitude and rate of co 2 injection in the ocean atmosphere system are compatible with a scenario of ocean acidification many carbonate platforms drowned in the pliensbachian well before the early toarcian event in this paper we test the hypothesis of surface water ocean acidification by presenting data from a resilient carbonate platform the apennine carbonate platform of southern italy the studied sections document a dramatic shift of the carbonate factory from massive biocalcification to chemical precipitation lithiotis bivalves and calcareous algae palaeodasycladus mediterraneus which were the most prolific carbonate producers of pliensbachian carbonate platforms disappear during the first phase of the early toarcian cie before the most depleted values are reached we discuss the local versus supraregional significance of this shift and propose a scenario involving abrupt decline of carbonate saturation forced by co 2 release at the beginning of the early toarcian cie followed by a calcification overshoot driven by the recovery of ocean alkalinity attribution of the demise of carbonate platform hypercalcifiers to ocean acidification is supported by palaeophysiology and reinforced by experimental data on the detrimental effects of ocean acidification on recent shellfishes and calcareous algae

the role of nutrient availability in bioerosion consequences to carbonate buildups abstract zooxanthellate organisms which are among the major carbonate producers on coral reefs are highly adapted to nutrient deficient conditions and tend to be outcompeted by filamentous or fleshy algae if nutrients are abundant reef dwelling bioeroding organisms on the other hand seem to increase in abundance with increasing availability of nutrient and food resources maximum rates of calcium carbonate production in a reef system are comparable in magnitude to maximum rates of bioerosion the dynamic interplay between accretion destruction of coral reefs is therefore likely to be strongly influenced by nutrient availability nutrient availability may also influence development of carbonate facies in reef systems that develop in oligotrophic waters skeletal sands and framework should dominate carbonate buildups in systems that develop in mesotrophic waters enhanced bioerosion should reduce much of the skeletal material to carbonate muds increasing the prevalence of mud rich facies eutrophic conditions should result in bioeroded hardgrounds and carbonate depositional hiatuses when carbonate accumulation rates fail to equal or exceed rates of local relative sea level rise reefs drown bored and lithified pavements with crusts of ferromanganese oxides phosphates or glauconite often separate shallow reef from overlying deeper water deposits nondeposition bioerosion and evidence for low redox potentials at the sediment water interface all implicate excess nutrient availability as a factor in reef drowning some carbonate depositional hiatuses and bioerosional surfaces are local phenomena evidence of responses to local increases in nutrient availability resulting from submergence of soils runoff or topographic upwelling others appear to reflect regional or worldwide events because many carbonate producing organisms have life history strategies specialized to nutrient deficient conditions they are unable to compete when nutrients become plentiful events that triggered ocean turnover or sharp increases in the rate of deep ocean circulation would have increased sea surface nutrient availability worldwide such eutrophication could have caused widespread extinctions in reef communities because eutrophication promotes bioerosion details of the fossil records of those events are probably lost in bioerosional hiatuses

late quaternary out of sequence deformation in the innermost kangra reentrant nw himalaya of india seismic potential appraisal from 10 be dated fluvial terraces abstract the kangra reentrant is a convex to the northeast u shaped structure in the nw himalaya where the sub himalayan fold and thrust belt is 90 km wide this region has not been struck by large earthquakes since the 1905 mw 7 8 kangra earthquake out of sequence deformation has been reported at the millennial timescale along intracrustal thrusts within this reentrant such as the jawalamukhi thrust up to now the occurrence of out of sequence deformation along inner thrusts within the kangra reentrant during the late quaternary has not yet been addressed in this study the results of a neotectonic survey undertaken in this reentrant are presented the studied zone is located between the beas and the neogad rivers and encompasses from the jawalamukhi thrust to the main boundary thrust two terraces that are deformed by branches of the medlicott wadia thrust locally named the palampur thrust are identified this is evidenced in the field by metric scale fault scarps by using 10be dating the ages of these terraces were constrained to ca 7 5 and ca 6 2 ka this is clear evidence of the late quaternary out of sequence deformation in the innermost part of this reentrant implying that strain is distributed along all the arc orthogonal extent of the local fold and thrust belt over this timespan a cumulative slip rate of ca 1 mm yr along the studied thrusts which represents 10 of the bulk strain accommodated by the whole reentrant for this timespan is calculated in spite of the marginal appearance of this figure this deformation rate is attributed to 7

tectono geomorphic indices of the erin basin ne kashmir valley india abstract the present study aims to assess the tectonic activity in the erin basin ne kashmir on the basis of several relevant geomorphic indices and field observations we use digital elevation model srtm and survey of india soi topographic maps in gis environment to compute the geomorphic indices the indices i e convex hypsometric curve high hypsometric integral value h i 0 5 low basin elongation ratio eb 0 17 low mountain front sinuosity values s mf 1 08 average low valley floor width ratios vf 4 suggest that the area is tectonically active moreover prominent irregularities knickpoints knickzones along longitudinal profile of the erin river even in homogenous resistant lithology panjal trap and anomalous stream gradient index sl values reflect that the erin basin is dissected by two faults ef 1 and ef 2 with nnw sse and ssw nne trends respectively the results of this preliminary study further substantiate the recent gps studies which argue that the maximum strain is accumulating in the ne part of the kashmir himalaya

gravity anomalies flexure of the indian plate and the structure support and evolution of the himalaya and ganga basin bouguer gravity anomalies along four profiles across the western himalaya and ganga basin show large deviations from local isostatic equilibrium a deficit of mass characterizes the ganga basin and an excess underlies the lesser himalaya both can be understood if the indian plate is flexed down by the distributed load of part of the mountains the cross sectional shape of the ganga basin seems to be controlled by the deflection of the indian plate which we compute assuming the indian plate to overlie an inviscid fluid from the shapes of both bouguer anomaly profiles and the basement topography we place bounds on the flexural rigidity of such a plate if the ganga basin is a steady state feature then the age of the basal sediments in a given locality should be proportional to the distance of that locality from the southern edge of the basin if the rate of convergence of india and the himalaya were constant that rate should equal the distance divided by the corresponding age we find a rate of 10 to 15 mm a for the last 15 to 20 ma which is consistent with a large part of the 50 mm a rate of convergence between india and eurasia being absorbed by the eastward extrusion of parts of tibet profiles of bouguer gravity anomalies show only a small peak or plateau over the southern edge of the lesser himalaya implying that the boundary between the light sediments of the ganga basin and the heavier crustal rocks of the lesser himalaya is not sharp and that there exists some light material beneath the range we infer that some sediment deposited in the ganga basin has been underthrust beneath the lesser himalaya but the quantity is small most of this sediment probably is scraped off the indian plate to make the foothills of the range we find that the load of the high himalaya is too large to be supported solely by elastic stress in the indian plate if the flexural rigidity of the plate is constant and if no other external forces act on the plate the observed gradient in bouguer gravity anomalies increases from an average of about 1 mgal km over the ganga basin and lesser himalaya to about 2 mgal km over the high himalaya this increase in the gravity gradient implies that the moho dips more steeply 10 15 beneath the high himalaya than beneath the lesser himalaya 2 3 we interpret this steepening of the moho to be due to a weakening of the plate which allows it to bend more sharply beneath the high himalaya than farther south with the inclusion of a weak segment of indian plate beneath the high himalaya calculated anomalies show a somewhat increased gradient beneath the high himalaya but when the weight of the entire himalaya is used as a load on the plate calculated anomalies are more negative than observed therefore an external force system is needed to support much of the weight of the high himalaya as well as to bend the plate sufficiently beneath the high himalaya the magnitudes of the bending moment and the force per unit length that must be applied to the end of the plate are compatible with their sources being gravity acting on a part of india s mantle lithosphere stripped of its crust and underthrust beneath southern tibet

post mortem onshore transportation of epiphytic foraminifera recent example from the tunisian coastline abstract the barrier island system that connects jerba island to the tunisian coastline is composed mainly of carbonate bioclastic sands well preserved tests of dead epiphytic foraminifera are abundant on the foreshore and backshore but they are scattered and poorly preserved on the shoreface where very fine sand size eolian quartz peloids and broken bioclasts are the main components the reason for this paradoxical pattern is that most epiphytic foraminifera are very easily removed as suspended load by storm generated currents and concentrated on beaches washover fans and small eolian dunes kilometers away from their original life environment similar bioaccumulations are common in the fossil record and have often been interpreted incorrectly as prolific biocoenoses

trophic control of benthic foraminiferal abundance and microhabitat in the bathyal gulf of lions western mediterranean sea surface sediment was sampled at two bathyal sites in the southwestern gulf of lions in the western mediterranean sea in february and august 1997 to study the distribution and microhabitat of living rose bengal stained deep sea benthic foraminifera both standing stock and diversity of the faunas and the microhabitat of distinct species mirror the trophic situation and the depth of the oxidised layer at the different sites our results suggest that the faunas do not comprise highly opportunistic species and are adapted to rather stable environments in the axial channel of the lacaze duthiers canyon organic matter fluxes are enhanced due to advective transport of organic matter resulting in elevated oxygen consumption rates in the surface sediment and a rather thin oxidised layer the corresponding benthic foraminiferal fauna is characterised by rather high standing stock and diversity and a well developed deep infauna in addition to freshly deposited phytodetritus more degraded organic matter seems to be an important food source in contrast at the open slope organic matter fluxes and oxygen consumption rates in the surface sediment are lower and the oxidised layer is much thicker than inside the canyon the corresponding benthic foraminiferal fauna comprises mainly epifaunal and shallow infaunal species with much lower standing stocks and clear differences between february and august in august standing stocks are higher and the average living depths of most species shift towards the sediment surface these differences can be attributed to patchiness or represent a seasonal trophic signal

distinguishing core and flank facies based on shell fabrics in lower jurassic lithiotid shell beds abstract lower jurassic larger bivalves mostly represented by the monospecific lithiotid genera lithiotis cochlearites and lithioperna formed large shell accumulations in the shallow water carbonate tethyan and panthalassa margins a quantitative analysis of lithiotid accumulations from the trento platform northern italy was carried out in order to distinguish the distribution of autochthonous parautochthonous and allochthonous lithiotids in the accumulation core and flanks various representative accumulations are characterized with respect to systematic content shell cover shell density disarticulation shell fragmentation and orientation of individual shells lithioperna shows a high shell cover within the accumulation core while that of cochlearites is variable and lithiotis is rare all three lithiotids occur in high densities in the accumulation flanks as expected autochthonous individuals of all three genera are frequent in the accumulation cores where they are preserved in life position in the flanks most bivalves are parautochthonous except for lithioperna which can grow in life position all bivalves in allochthonous shell beds are highly fragmented and disarticulated the studied traits are potentially useful as proxies for distinguishing core or flank facies when the accumulation does not crop out as a whole

ecostratigraphy of benthic foraminifera for interpreting arctic record of early toarcian biotic crisis northern siberia russia abstract the present contribution focusses on ecostratigraphic fluctuations of foraminiferal assemblages occurring during the benthic biotic crisis corresponding to the early toarcian anoxic event we aim at understanding the response of benthic biota to the environmental changes that occurred during the crisis in a high latitude setting and compare with previous data from total organic carbon toc and 13c from previous works the kelimyar river section exposes a lower jurassic marine succession made up of siltstones sandy siltstones uppermost pliensbachian and black shales lower toarcian deposited close to the early jurassic north pole in a relatively deep continental shelf the pliensbachian sediments are represented by a foraminiferal assemblage dominated by epifauna mainly trochammina but showing a progressive diminution in diversity this suggests an unfavourable microhabitat for infaunal forms probably involving salinity fluctuations although the opportunist trochammina tolerated salinity fluctuations the decreasing proportions of aragonitic and calcitic hyaline foraminifera indicate the progressive deterioration of the benthic environment a context of relative sea level fall in the arctic palaeobasin during the margaritatus zone and the beginning of the viligaensis ammonite zone related to an abrupt climatic cooling would explain these environmental changes including salinity fluctuations that lead to decreased diversity and even the disappearance of calcitic and aragonitic forms the debut of the falciferum zone lower toarcian is characterised by laminated black shales high total organic carbon a negative carbon isotopic excursion and an abrupt decrease in the foraminiferal abundance and diversity these features indicate oxygen restricted conditions in the sea bottom only opportunist trochammina shows a rapid increase in abundance after the debut of the black shales congruent with the relation of this genus with high toc and a poorly oxygenated sediment water interface trochammina was able to colonise the sea bottom after the development of hypoxic conditions in the kelimyar river section these adverse conditions occurred just after the negative carbon isotopic excursion and maximum values of toc and correlate with the climatic warming that occurred in the arctic palaeobasins referred to by previous authors detailed analysis of the sea bottom recolonisation points to a foraminiferal replacement in which distinct foraminiferal morphogroups reach their optimum values finally despite certain differences the benthic foraminiferal assemblages from kelimyar river section are comparable with those from the north african palaeomargin in the ratnek el kahla section algeria thus illustrating an equivalent response of benthic foraminiferal assemblages to the early toarcian biotic crisis in both cases the composition of assemblages diversity and abundance of foraminifera were sensitive to restricted oxygen conditions and opportunist species did colonize the sea bottom after this biotic crisis

changes in garnet chemistry show a progressive denudation of the source areas for permian jurassic sandstones southern kitakami terrane japan abstract garnet is a widespread detrital mineral in permian jurassic sandstones of the southern kitakami terrane electron probe microanalyses of these garnets show a gradual change of chemistry with the age of the sandstones the dominant garnet suites in permian triassic sandstones are grandite with some spessartine almandine in upper triassic sandstones however in lower jurassic sandstones pyrope almandine and spessartine almandine garnets are common whereas grandite garnets are absent garnet suites in middle to upper jurassic sandstones are dominated by pyrope almandine garnet the grandite dominant suites are associated with hornblende epidote and titanite whereas the pyrope almandine dominant suites are associated with biotite these grandite garnets are rich in andradite and have very low spessartine almandine and pyrope contents some of the grandite garnets are anisotropic with oscillatory zoning and sector twinning typical of calcic skarn deposits spessartine almandine garnets are common in low grade metamorphic rocks the diverse suites of pyrope almandine garnets up to 42 mol pyrope from the jurassic sandstones are typical of epidote amphibolite to granulite facies metamorphic rocks the chemistry and optical properties of garnets and the heavy mineral data show that low grade or contact metamorphic rocks such as skarns and hornfelses were widely exposed in the source areas of the permian triassic sandstones high grade metamorphic rocks including granulites and intrusive rocks appeared in early jurassic time and were widespread during the middle jurassic the critical change in the source areas for the southern kitakami terrane occurred during late triassic to early jurassic time and may correspond to the indosinian movements associated with the collision between the north china and south china blocks

margin parallel translation in the western pacific paleomagnetic evidence from an allochthonous terrane in japan abstract a new paleomagnetic study illustrates latitudinal translation of ribbon shaped continental fragments along the western margin of the pacific ocean though tectonic translations have long been recognized as prominent features in the eastern pacific margin i e north american cordillera we present new quantitative evidence for similar margin parallel motion through large scale strike slip faulting in the western pacific margin the kurosegawa terrane in southwest japan is an attenuated tectonic sliver and considered to be allochthonous with respect to the main part of southwest japan late triassic and early cretaceous sedimentary rocks from the terrane yielded paleolatitudes of 4 n and 18 n respectively based on paleomagnetic data of the kurosegawa terrane and plate reconstructions of east asia we suggest that the terrane was the easternmost element of the south china block at least from the late triassic to the early cretaceous the terrane was then translated 1500 km northward from the continental margin to its present position associated with sinistral strike slip movement along the east asian continental margin in mid to late cretaceous times the average displacement rate is calculated to be 7 cm yr and is comparable to rates reported for the eastern pacific margin

subsidence and sedimentation on jurassic passive continental margin southern alps italy the southern alps of italy preserve a tectonically intact array of jurassic facies that record the evolution of a part of the margin of the apulian plate from its ancestral beginnings in a complex of permian and triassic rifted continental basins through the initial stages of breakup and stepwise foundering of a carbonate platform breakup was accompanied first by the rapid accumulation of thick prisms of carbonate turbidites in newly formed fault troughs then as the new ligurian oceanic basin began to open farther west and as subsidence gradually slowed accumulation of a succession of slowly deposited biogenous pelagic sediments recorded not only the increasing depths of the seafloor but also fluctuations in oceanographic conditions of fertility carbonate dissolutio levels and the strength of bottom currents estimates of the history of seafloor depths based on a simple subsidence law of the form subsidence k age 12 provide a basis for the construction of a set of curves showing the changing depths of significant carbonate dissolution surfaces during the jurassic in this region the rapid 1 km deepening of the compensation depth for calcite during the late jurassic may be due to a change in regional oceanic vertical circulation patterns from upwelling fertile silica rich carbonate dissolving to downwelling less fertile silica poor carbonate preserving

chronology of sanbagawa metamorphism by collating age data based on the fossil age of the protoliths radiometric dating of the metamorphic minerals and sedimentary records of erosion at the earth s surface the history of the sanbagawa metamorphism can be summarized as follows 1 the pre metamorphic sedimentary rocks carboniferous jurassic early cretaceous became mixed and formed a thickened packet in the vicinity of an ancient trench through a variety of subduction related tectono sedimentary processes probably in early cretaceous time c 130 120 ma 2 the subducted protoliths underwent progressive metamorphism reaching a maximum depth of c 30 km in late early cretaceous time c 116 10 ma 3 the high p t metamorphic rocks began to rise toward the surface during the interval 110 50 ma with minimum estimates for the average cooling rate around 9 12 c ma and an average uplift rate around 0 4 0 5 mm year 4 finally at some stage after reaching the erosional surface the high p t metamorphic rocks were covered unconformably by the middle eocene c 50 42 ma kuma group on the basis of the present chronological summary of the sanbagawa metamorphism the areal extent of the sanbagawa metamorphism is also discussed with respect to the weakly metamorphosed subduction accretion complex of the next tectonic belt to the south the northern chichibu belt

early pliensbachian early jurassic c isotope perturbation and the diffusion of the lithiotis fauna insights from the western tethys abstract high resolution carbonate carbon isotope stratigraphy of lower jurassic marine shallow water limestones are compared with the distribution of the lithiotis fauna on the trento platform southern alps italy the lithiotis fauna is the first example of globally distributed mound building bivalves in the geological record and experienced global diffusion in the early jurassic a set of carbonate carbon isotope excursions of 2 3 illustrating three distinct negative shifts followed by positive rebounds are recorded in the isotope stratigraphy and can be correlated with the global negative 13 c shift of the sinemurian pliensbachian boundary event s p event and to the subsequent phase of c isotope perturbation that characterized the lower pliensbachian in the studied stratigraphic sections the s p event likely triggered eutrophic conditions illustrated by the presence of organic rich facies and by fossil associations characteristic of poorly oxygenated waters after the eutrophic phase the amelioration of environmental conditions was marked by a positive 3 rebound of the 13 c carb values and by the occurrence of marine stenotypic faunas on the trento platform the stabilization of the 13 c carb values coincided with the appearance of the lithiotis fauna that subsequently became widely distributed in the entire range of platform environments and thrived in the late pliensbachian when metric scale bivalve mounds were generated during the same time the maximum proliferation of the lithiotis fauna is recorded both in the tethyan and panthalassa regions hence the reported relationships between the 13 c carb data and the distribution and ecological characteristics of the genera contained in the lithiotis fauna suggest that the s p event and its aftermath possibly coupled with the undergoing coeval continent reorganization that led to the opening of the hispanic corridor could have set the stage for the rapid diffusion of these unusual bivalves across many parts of the globe

high frequency cycles and sequence stratigraphy of the lower jurassic marrat formation central saudi arabia abstract well exposed stratigraphic sections of the toarcian siliciclastic carbonate deposits of the marrat formation exposed at the khashm adh dhibi area southwest of riyadh city saudi arabia were studied for their facies associations and controls on sequence development seven facies associations from tide dominated deltaic to inner carbonate ramp were recognized inferences based on facies relationships characteristics of the sequence boundary and other characteristics suggest deposition of the marrat formation during three 3rd order sequences these can be further classified into seventeen 4th order shallowing upward small cycle sets correlation of the recorded sequences boundaries within the arabian african plates europe and global schemes reflect a strong eustatic control during the early jurassic age with recognizable tectonic signature of the gondwanland rift effects that caused a long period of regional uplift and non deposition across the triassic jurassic and early middle jurassic unconformities

a multivariate discrimination scheme of detrital garnet chemistry for use in sedimentary provenance analysis abstract garnet chemistry provides a well established tool in the discrimination and interpretation of sediment provenance current discrimination approaches however i suffer from using less variables than available ii subjective determination of discrimination fields with strict boundaries suggesting clear separations where in fact probabilities are converging and iii significant overlap of compositional fields of garnet from different host rock groups the new multivariate discrimination scheme is based on a large database a hierarchical discrimination approach involving three steps linear discriminant analysis at each step and the five major host rock groups to be discriminated eclogite a amphibolite b and granulite c facies metamorphic rocks as well as ultramafic d and igneous rocks e the successful application of statistical discrimination approaches requires consideration of the a priori knowledge of the respective geologic setting this is accounted for by the use of prior probabilities three sets of prior probabilities priors are introduced and their advantages and disadvantages are discussed the user is free to choose among these priors which can be further modified according to the specific geologic problem and the level of a priori knowledge the discrimination results are provided as integrated probabilities of belonging to the five major host rock groups for performing calculations and results a supplementary excel spreadsheet is provided the discrimination scheme has been tested for a large variety of examples of crystalline rocks covering all of the five major groups and several subgroups from various geologic settings in most cases garnets are assigned correctly to the respective group exceptions typically reflect the peculiarities of the regional geologic situation evaluation of detrital garnets from modern and ancient sedimentary settings of the western gneiss region norway eastern alps austria and albertine rift uganda demonstrates the power to reflect the respective geologic situations and corroborates previous results as most garnet is derived from metamorphic rocks and many provenance studies aim at reconstructing the tectonic and geodynamic evolution in the source area the approach and the examples emphasize discrimination of metamorphic facies i e temperature pressure conditions rather than protolith composition

taphonomy and evolution of lower jurassic lithiotid bivalve accumulations in the apennine carbonate platform southern italy abstract lower jurassic tethyan and panthalassan marine shallow water successions are characterized by aberrant lithiotid bivalves belonging to the lithiotis fauna their widespread occurrence often in rock forming abundance represents a global biofacies mostly restricted to the pliensbachian early toarcian despite their wide occurrence and their prominent role as carbonate producers in shallow water platforms the biogeographic and stratigraphic distribution of this group of bivalves and their evolutionary history are obscure mostly because they commonly have not been identified at the generic or specific level in particular their evolution and demise in relation to important global palaeoenvironmental perturbations such as the pliensbachian toarcian boundary event and the early toarcian oceanic anoxic event are not yet known in detail in the apennine carbonate platform of southern italy the lithiotis member in the upper part of the lower jurassic palaeodasycladus limestones formation is characterized by the abundant occurrence of lithiotid bivalves they disappear abruptly in the lowermost beds of the overlying oolitic oncolitic limestones formation at the onset of the early toarcian oceanic anoxic event more than 60 lithiotid bivalve concentrations occur in a nearly 120 m thick succession spectacularly exposed on freshly cut walls in a quarry west of mercato san severino salerno field observations on the taxonomic composition and fabric of the shell beds packing maximum shell size degree of shell articulation and fragmentation allowed to distinguish four taphofacies a d taphofacies a records the appearance and spreading of the lithiotids with accumulations characterized mainly by small sized and loosely packed shells taphofacies b records the acme of lithiotid bivalves with densely packed accumulations of large shells these two taphofacies yield prevailing articulated individuals commonly in life position taphofacies c records a decrease of the shell packing and frequency of articulated shells however it is not clear whether this represents the beginning of a prolonged crisis or just the local response to less favourable environmental conditions around a sequence boundary taphofacies d consists of three shell beds one in the uppermost part of the lithiotis member and two within the lowermost part of the oolitic oncolitic limestones formation in the stratigraphic interval characterized by the negative carbon isotope excursion of the early toarcian oae the bivalve shells of these two beds consist exclusively of disarticulated and fragmented shells possibly reworked from underlying levels the demise of the lithiotids carbonate factory in the apennine carbonate platform and the extinction of the largest aberrant bivalves of the lithiotis fauna at the onset of the early toarcian anoxic event were probably due to the physiological stress imposed by ocean acidification and increased nutrient input

foraminiferal morphogroups as a tool to approach the toarcian anoxic event in the western saharan atlas algeria abstract the present contribution constitutes the first morphogroup analysis of foraminiferal assemblages applied to the toarcian oceanic anoxic event t oae in the maghreb region which represented the northern palaeomargin of gondwana the ecostratigraphic and palaeoecologic analysis of the foraminiferal assemblages has allowed interpretation of the evolution of the biotic crisis associated with the t oae in the saharan atlas deposits and the recovery of foraminiferal assemblages in the sea bottom after the event the foraminiferal assemblages of the uppermost pliensbachian emaciatum zone represent optimum ecological conditions good oxygen and nutrient availability in the infaunal microhabitats as evidenced by the high diversity of k strategists and the low diversity of r strategists representing a minor proportion in the assemblages the beginning of the toarcian polymorphum zone shows an initial phase of unstabilization of the benthic environment affecting some particular species while opportunistic forms proliferate epistomina and lenticulina variations in the oxygenation degree affecting the infaunal microhabitat favoured stress tolerant species with extensive niche such as lenticulina and eoguttulina later a benthic azoic interval includes the lower part of the levisoni zone in this interval a slight increase of total organic carbon toc values recorded can be related to dysoxic or anoxic conditions in low oxygen bottom water beyond the ecological tolerance of opportunist forms after the benthic mass extinction interval a slow colonisation is registered upper part of the levisoni zone with a dominance of r type strategists lenticulina reinholdella and eoguttulina

morphotectonic analysis of aripal basin in the north western himalayas india an evaluation of tectonics derived from geomorphic indices abstract himalayan river basins are exposed to continuous erosion and deformational processes the main goal of this paper is to characterize the tectonic activity as it acts as a controlling factor in the development of landforms in the tectonically active terrains research was carried out in the aripal basin which lies to the south east of kashmir valley one of the right bank tributary of river jhelum the geomorphic indices and morphometric parameters are determined using advanced spaceborne thermal reflection and emission radiometer aster 30 m digital elevation model the low mountain front sinuosity smf 1 3 s type hypsometric curve with high hypsometric integral hi 0 35 low valley floor width to valley height ratios vf

seismic slip deficit in the kashmir himalaya from gps observations 1 gps measurements in kashmir himalaya reveal range normal convergence of 11 1 mm yr with dextral shear of 5 1 mm yr the transition from a fully locked 170 km wide decollement to the unrestrained descending indian plate occurs at 25 km depth over an 23 km wide transition zone the convergence rate is consistent with the lower bounds of geological estimates for the main frontal thrust riasi and balapora fault systems on which no surface slip has been reported in the past millennium of the 14 damaging kashmir earthquakes since 1123 none may have exceeded mw 7 6 therefore either a seismic moment deficit equivalent to a mw 8 7 earthquake exists or the historical earthquake magnitudes have been underestimated alternatively these earthquakes have occurred on reverse faults in the kashmir valley and the decollement has been recently inactive although this can reconcile the inferred and theoretical moment release it is quantitatively inconsistent with observed fault slip in kashmir

restoration of exotic terranes along the median tectonic line japanese islands overview abstract this paper reviews recent progress on the geotectonic evolution of exotic paleozoic terranes in southwest japan namely the paleo ryoke and kurosegawa terranes the paleo ryoke terrane is composed mainly of permian granitic rocks with hornfels mid cretaceous high grade metamorphic rocks associated with granitic rocks and upper cretaceous sedimentary cover they form nappe structures on the sambagawa metamorphic rocks the permian granitic rocks are correlative with granitic clasts in permian conglomerates in the south kitakami terrane whereas the mid cretaceous rocks are correlative with those in the abukuma terrane this correlation suggests that the elements of northeast japan to the northeast of the tanakura tectonic line were connected in between the paired metamorphic belt along the median tectonic line southwest japan the kurosegawa terrane is composed of various paleozoic rocks with serpentinite and occurs as disrupted bodies bounded by faults in the middle part of the jurassic chichibu terrane accretionary complex it is correlated with the south kitakami terrane in northeast japan the constituents of both terranes are considered to have been originally distributed more closely and overlay the jurassic accretionary terrane as nappes the current sporadic occurrence of these terranes can possibly be attributed to the difference in erosion level and later stage depression or transtension along strike slip faults the constituents of both exotic terranes especially the ordovician granite in the kurosegawa south kitakami terrane and the permian granite in the paleo ryoke terrane provide a significant key to reconstructing these exotic terranes by correlating them with paleozoic granitoids in the eastern asia continent

sapphirine bearing granulites and related high temperature metamorphic rocks from the higo metamorphic terrane west central kyushu japan the higo metamorphic unit in west central kyushu island southwest japan is an imbricated crustal section in which a sequence of units with increasing metamorphic grade from high northern part to low southern part structural levels is exposed the basal part of the metamorphic sequence representing an original depth of 23 24 km consists mainly of garnet cordierite biotite gneiss garnet orthopyroxene gneiss orthopyroxene bearing amphibolite and orthopyroxene bearing s type tonalite these metamorphic rocks underwent high amphibolite facies up to granulite facies metamorphism with peak p t conditions of 720 mpa 870 c in addition sapphirine bearing granulites and related high temperature metamorphic rocks also occur as tectonic blocks in a metamorphosed peridotite intrusion the sapphirine bearing granulites and their related high temperature metamorphic rocks can be subdivided into five types of mineral assemblages reflecting their bulk chemical compositions as follows 1 sapphirine corundum spinel cordierite 2 corundum spinel cordierite 3 garnet corundum spinel cordierite 4 garnet spinel gedrite corundum and 5 orthopyroxene spinel gedrite these metamorphic rocks are characterized by unusually high al2o3 and low sio2 contents which could represent a restitic nature remaining after partial melting of pelitic granulite under the ultra high temperature contact metamorphism at the peak metamorphic event of the higo metamorphic unit the metamorphic conditions are estimated to be about 800 mpa and above 950 c which took place at about 250 ma as a result of the thermal effect of the regional gabbroic rock intrusions

reply to comments by ahmad et al on shah a a 2013 earthquake geology of kashmir basin and its implications for future large earthquakes international journal of earth sciences doi 10 1007 s00531 013 0874 8 and on shah a a 2015 kashmir basin fault and its tectonic significance in nw himalaya jammu and kashmir india international journal of earth sciences doi 10 1007 s00531 015 1183 1 shah int j earth sci 102 1957 1966 2013 mapped major unknown faults and fault segments in kashmir basin using geomorphological techniques the major trace of out of sequence thrust fault was named as kashmir basin fault kbf because it runs through the middle of kashmir basin and the active movement on it has backtilted and uplifted most of the basin ahmad et al int j earth sci 2015 have disputed the existence of kbf and maintained that faults identified by shah int j earth sci 102 1957 1966 2013 were already mapped as inferred faults by earlier workers the early works however show a major normal fault or a minor out of sequence reverse fault and none have shown a major thrust fault

surface ruptures of large himalayan earthquakes in western nepal evidence along a reactivated strand of the main boundary thrust the chronology of the seismic ruptures along the active faults of western nepal remains almost unconstrained despite their high seismogenic potential we present here a slip history of one of these structures a 120 km long reactivated segment of the main boundary thrust named the surkhet gorahi fault this slip history is based on geomorphologic and neotectonic mapping of active faults deduced from the analysis of a high resolution total station digital elevation model and 15 detrital charcoals radiocarbon ages constraining the age of deposition or abandonment of 4 alluvial terraces of the bheri river in botechaur our results show that the last two earthquakes occurred on this fault after 1860 and 640 bp respectively and accommodated slip greater than 8 m each a value corresponding to the incremental vertical offset of the terraces such events released a significant part of the slip deficit accumulated on the main himalayan thrust fault however given the geometry of this fault system as well as the date of occurrence of the last events the ruptures could be associated with major earthquakes also rupturing the main frontal thrust such as the great 1505 earthquake

trophic regimes of benthic foraminiferal assemblages in lower jurassic shallow water carbonates from northeastern italy calcari grigi trento platform venetian prealps abstract benthic foraminiferal distribution patterns in the lower jurassic rotzo member trento platform northeastern italy are analysed in terms of trophic gradients to provide a better understanding of the benthic communities during the time of the initial diversification of lower jurassic large foraminifera in the southern alps the rotzo member deposited on the trento platform records a complex mosaic of distinct shallow water ecosystems the changes in the foraminiferal assemblages of the rotzo member are considered to be primarily a reflection of gradients in trophic resources and oxygen levels the comparative analysis of benthic foraminiferal assemblages characteristic taxa number of species test size reproduction strategy the associated sediments lithofacies and the macrofossil and microfossil content allow three trophic regimes to be identified during the time of deposition of the rotzo member a eutrophic b mesotrophic and c oligotrophic a the eutrophic regime marked by episodically dysaerobic bottom conditions and high organic matter supply occurs stratigraphically below and within the orbitopsella spp assemblage sinemurian pro parte carixian gradual change in the benthic foraminiferal assemblage may have been caused by a combination of reduced nutrient supply and increased bottom water circulation which led to a mesotrophic regime b the latter which has been recognised in the basal and middle part of the rotzo member alternating with the eutrophic assemblage is characterised by a foraminiferal assemblage dominated by orbitopsella sp a major foraminiferal faunal turnover across the carixian domerian boundary corresponding to the disappearance of orbitopsella spp indicates a significant environmental change an oligotrophic regime c became established towards the upper part of the rotzo member new taxa appeared and diversity of the foraminiferal faunas was higher than in the previous ecosystems this part of the member characterised by the maximum lateral and vertical development of large lithiotis bivalve mounds reflects low and more stable nutrient supply which provided optimal conditions for the more specialised benthic communities evolution of these benthic foraminiferal faunas from the late pliensbachian onwards was obliterated by events that led to the drowning of the trento platform which is marked by a regional unconformity

spatiotemporal landslide detection for the 2005 kashmir earthquake region abstract various scientists forecasted long term major slope failures after the 8 october 2005 7 6 mw earthquake in the northern parts of pakistan along the balakot bagh fault line the earthquake destabilized numerous slopes by creating a large number of tension cracks which may lead together with the monsoonal climatic conditions to increased landslide activity to test these forecasts an area of 36 km2 was selected in which changes in landslide activity area and types were quantified after each monsoon season for the following consecutive three years on screen stereo interpretations of high spatial resolution satellite imagery were carried out together with field investigations to identify landslide types and to quantify their changes in the area the landslide inventory showed that 158 landslides were triggered along the balakot bagh fault line the most abundant type of active landslide was translational which was mainly concentrated along the fault line in the muzaffarabad formation landslide activity was very high for a period of two years at maximum after which the majority of the slopes gained a state of stability in contrast to the predictions of long term extensive landslide activity slopes started re vegetating and landslide activity decreased within two years after the earthquake

bivalve pavements from shallow water black shales in the early jurassic of northern italy a record of salinity and oxygen depleted environmental dynamics abstract thin shelled bivalve pavements which constitute the eomiodon horizon occur in a distinctive black shale unit in the lowermost part of a lower jurassic carbonate platform sedimentary system of the southern alps italy the eomiodon horizon is characterised by laminated mudstone and fissile dark grey and black organic rich marlstone and claystone yielding abundant bivalve pavements with monotypic to paucispecific assemblages dominated by eomiodon an opportunistic brackish shallow infaunal veneroid bivalve litho and biofacies indicate environmental conditions ranging from nearshore euhaline waters to oxygen depleted brackish lagoon with a high input of terrestrial organic matter culminating in marsh and terrestrial conditions these pavements were analysed using a microstratigraphic approach while considering their taxonomic composition the geometry of the beds their biofabric criteria size sorting abundance fragmentation orientation and disarticulation origin and time averaging these characteristics led to reconstruction of the following palaeoenvironmental dynamics 1 the event concentrations represented by mass mortality of stunted and juvenile individuals caused by anoxia are indicative of deeper and predominantly stagnant parts of the lagoon 2 an increase in shell sizes higher growth rate and a decrease in size sorting and winnowing illustrate higher and more continuous bottom oxygenation and enhanced life in oxygen fluctuated environmental conditions 3 poorly sorted highly fragmented and bioturbated bivalve accumulations indicate the eomiodon habitat here large sized eomiodon specimens record a decrease in water depth and sedimentation rate and almost constantly oxygenated bottom conditions 4 the appearance of byssally attached bivalves lithioperna marks the transition from the muddy soupy substrate of the eomiodon habitat to firm hard bottom conditions this new substrate allowed the settlement of lithioperna a byssate isognomonid which records a shallower and landward marsh setting the eomiodon horizon testifies to a short term warm humid climatic phase and yielded lithioperna the first genus of the lower jurassic lithiotis fauna to appear in southern alps this fauna is composed of large and aberrant bivalves which are spread throughout the lower jurassic tethyan and tropical panthalassian carbonate platforms as a result the eomiodon horizon and its salinity and oxygen depleted environmental setting represent a possible progenitor incubator for the lithiotis fauna

no major active backthrust bounds the pir panjal range near kashmir basin nw himalaya abstract this research disputes the geomorphic data presented in dar et al 2014 and demonstrates that their data strongly conflicts with their own field evidence and also with the previous geological observations the authors have proposed a major sw dipping frontal fault that bounds the pir panjal range near kashmir basin of nw himalaya however field photographs show a very steep 86 dipping normal fault this therefore contradicts with all the morphometric indices interpretations and discussion presented because those are based on a major se dipping thrust fault that bounds pir panjal range in kashmir basin the proposed fault is a major sw dipping backthrust which primarily conflicts with the previous geological observations in kashmir basin because mostly ne dipping major thrusts are mapped in this region and presently only three major ne dipping faults the main frontal thrust mft the raisi fault rf and the kashmir basin fault kbf are tectonically active the new proposed major active thrust as suggested by the triangular facets mapped by dar et al 2014 was mapped on the basis of geomorphic evidence as a sw dipping thrust fault and field evidence shows a normal fault which utterly questions the nature and significance of the new research work

changes in detrital garnet assemblages related to transpressive uplifting associated with strike slip faulting an example from the cretaceous system in kii peninsula southwest japan abstract the chemical characteristics of detrital garnet have served as relatively reliable and definitive indicators of the major tectonic settings of sedimentary units in many parts of the world in southwest japan a multidisciplinary approach combining sandstone modal heavy mineral and garnet compositional analyses of the cretaceous upper continental slope to trench deposits of the kurosegawa and shimanto belts combined with a comparison of the detrital garnet features in and around kii peninsula revealed the following characteristics the garnet assemblages show significant changes with age the lower cretaceous yuasa formation is characterized by pyrope rich almandine garnets derived from granulite facies metamorphic rocks these are associated with garnet grains that have pyrope almandine compositions and high grossular contents suggesting an eclogite origin garnet assemblages of the lower upper cretaceous yukawa formation are dominated by grains with chemical characteristics indicating an origin as low p t type metamorphic rocks there are also spessartine almandine garnets derived from acidic igneous rocks some with a high p t type metamorphic origin and others with a grandite composition garnet assemblages of the upper upper cretaceous miyama formation are similar to those of the yukawa formation with the exception that grandite garnets are absent the above compositional changes of garnets in the deposits allow us to characterize the corresponding provenances and by combining these results with stratigraphic ages temporal changes of these provenances can also be determined the source area for the granulite facies metamorphic rocks that continuously supplied detritus throughout the cretaceous might be precambrian continental basement in east asia in early late cretaceous time the detritus was derived from terranes distributed along the median tectonic line a major strike slip fault stretching throughout southwest japan the garnet compositions suggest the source area included eclogite in the kurosegawa belt that forms the basement to the cretaceous strata and the low p t type metamorphic rocks and granitic rocks in the paleo ryoke belt including the higo belt studies of the miyama formation show that at this time widespread acidic volcanism began and this was the source for much of the volcanic sediment in the formation the provenance change between the lower and lower upper cretaceous formations is likely to have been caused by uplifting and unroofing associated with cretaceous transpression expressed by the strike slip movement along the median tectonic line and other lateral faults in the chichibu belt

environmental control and dynamics of lower jurassic bivalve build ups in the trento platform southern alps italy abstract bivalve molluscs show a short and peculiar early jurassic evolutionary phase characterized by the lithiotis sensu lato fauna mainly represented by the three monospecific genera lithiotis cochlearites and lithioperna these bivalves with stick like or flattened large shells are mostly restricted to the pliensbachian they have a wide geographical distribution occurring both in tethyan and panthalassian carbonate platforms where considerable biogenic accumulations formed they were common on the trento platform southern alps where they occur in the rotzo formation calcari grigi group this formation was deposited in a tropical lagoon which was closed seawards by oolitic shoals and bars and bordered landwards by marshes the lithiotis s l fauna of the trento platform seems to be restricted to the upper pliensbachian it appeared after a eutrophic phase with recurrent low oxygen and brackish conditions and flourished in meso to oligotrophic waters the stratigraphic and geographic distributions of each genus are compared to the environmental development of the rotzo formation in order to highlight limiting environmental factors and ecological requirements lithioperna occurs throughout the whole formation it is the most eurytopic genus well adapted to dysaerobic habitats and with higher ecomorphic plasticity than the other two genera it frequently occurs in the life position giving rise to densely packed fan like or book like aggregates lithiotis required aerobic and euhaline marine conditions and is common in the middle part of the formation where mesotrophic conditions prevailed this genus is rarely preserved in the theoretical vertical life position probably due to lower shell stability and a less effective attachment modality cochlearites is the most common genus of the rotzo formation this genus inhabited euhaline to slightly hypersaline marine environments occurring in the upper part of the formation prevailing in oligotrophic conditions lithiotis s l fauna gave rise to biogenic accumulations with an elevation of a few decimeters to several meters above the sea bottom and with a lateral extension ranging from ten to several hundred meters therefore these accumulations represent biological build ups which document four developmental phases colonization aggradation progradation and demise the colonization phase is represented by pioneering individuals which were cemented or byssally attached to a bioclastic coarse grained storm layer which constituted the hard substrate for larval attachment the aggradation phase produced the core of the build up and its elevation above the sea bottom the core is mostly represented by individuals which acted as bafflers commonly with an apparently chaotic fabric the lithiotis s s and cochlearites cores are generally mud supported and contain loosely packed to dispersed specimens occasionally preserved in life position the lithiotis s s and cochlearites build ups can be defined as bivalve mounds the cores of the lithioperna build ups are skeletal supported with shells mostly preserved in life position which characterize the bivalve reefs the prograding phase produced lateral additions to the build up flanks of oblique and imbricated articulated individuals the flanks grew centrifugally from the core and represent the most conspicuous part of the build ups ranging from 10 to 20 times the size of the core and occasionally extending over several hundred meters

dolomite characteristics and diagenetic model of the calcari grigi group asiago plateau southern alps italy an example of multiphase dolomitization a multidisciplinary study conducted over the carbonate platform deposits of the liassic calcari grigi group southern alps highlighted how the use of outcrop analogues can contribute to better define the distribution of dolomitic bodies related to fault networks to characterize the petrophysical properties of the dolomitic sequence and unravel a complex diagenetic history this study was carried out in the asiago plateau southernmost part of the eastern southern alps northern italy which provides excellent outcrops of the jurassic calcari grigi group the dolomitization of the jurassic sequence is variable in terms of stratigraphic extension and geographic distribution in the studied localities the dolomitization is generally limited to the mount zugna formation and is characterized by an undulatory front with sub vertical dolomitic chimneys along the major faults within this unit and often associated with faults stacked high porosity and permeability bed parallel dolomitic bodies are developed that show excellent petrophysical properties the dolomitic intervals are characterized by pervasive unimodal and patchy polymodal dolomite crystals thin section cathodoluminescence isotopic and fluid inclusion analyses were used to constrain the paragenetic evolution of the sequence which is similar in all the studied localities the first dolomitization stage is marked by zoned dolomite crystals with a dull luminescent core the porosity is thought to have increased after this stage with dark blue luminescent dolomite accompanied by the corrosion of older crystals the appearance of saddle dolomite marks the onset of the porosity reduction stage ending with the infilling of vugs and the remaining open pores with calcite cement the diagenetic evolution locally stopped at the saddle dolomite stage with the complete occlusion of the remaining pores paragenetic and fluid inclusion data suggest an evolutionary trend of increasing temperatures and decreasing salinity toward brackish fluids responsible for dolomite and calcite precipitation the integration of the available data seem to indicate that the diagenetic evolution of the study area is related to i the interplay between evolving fluids from marine to brackish ii the burial of the sequence increasing temperature and iii the evolution of the hydrogeological system fault and fracture network fluid mixing this complex paragenetic evolution is strongly linked to the evolution of the porosity framework that evolved from a good widespread network in the early stages of the burial history to a confined system in the later stages due to reduction of porosity by the deposition of late calcite and dolomite cements

constraints on the exhumation and erosion of the high himalayan slab nw india from foreland basin deposits petrography sr nd isotope compositions and single grain laser 40ar 39ar ages of detrital white mica from early middle miocene molasse of the dharamsala and lower siwalik formations of northern india dated by magnetostratigraphy determine the sediment sources their metamorphic grade and exhumation rates in the himalayan palaeo hinterland deposition of the lower dharamsala member 21 17 ma occurred during the period of rapid isothermal decompression and crustal anatexis 24 18 ma of the metamorphic core this episode of decompression is thought to be coeval with thrusting on the main central thrust and normal faulting on the south tibetan detachment system the sediment composition and detrital mica ages indicate erosion from the rapidly exhumed metamorphic slab of the high himalayan crystalline series deposition of the upper dharamsala member 17 13 ma and basal siwalik group 13 12 5 ma spanned the period in which thrusting transferred south from the main central thrust the sediment composition and detrital mica ages contrast strongly with those of the lower dharamsala indicating erosion from sedimentary and low grade rocks the isotopic composition indicates that these rocks were part of the high himalayan series unaffected by tertiary metamorphism i e from upper structural levels of the high himalayan slab this suggests that a major reorganisation of the orogenic wedge occurred at 17 ma involving forward propagation of the mct and cessation of rapid exhumation of the metamorphic slab