crossing the several scales of strain accomplishing mechanisms in the hinterland of the central andean fold thrust belt bolivia depictions of structures at outcrop regional and tectonic scales enforce horizontal shortening and vertical thickening as the predominant style of deformation at all scales within the hinterland of the central andean fold thrust belt outcrop scale structures document a progression of strain that created 1 flexural slip folds 2 fold flattening via axial planar cleavage 3 vertical stretching via boudinage and late stage faulting and finally 4 kink folding these examples of intraformational deformation are generally concentrated just beyond the tip lines of thrust faults where fault propagation folds and related structures are well developed fault propagation folding accommodated the accrual of strain indicated by outcrop scale structures while the structures themselves indicate how deformation developed within each individual fold fault propagation fold geometries at a regional scale emerge from the construction of regional balanced cross sections the sections were drawn with careful attention to 1 known map relationships 2 field inspection of key contacts 3 bedding orientation data 4 local seismic control and 5 principles of balance the pervasive ese wnw shortening and vertical elongation seen at the outcrop and regional scales developed during the formation of the central andean backthrust belt in the hinterland of the andes the central andean backthrust belt is a large scale west vergent thrust system along the western side of the eastern cordillera in the generally east vergent andean fold thrust belt of bolivia strain accrual within this west verging zone of deformation is proposed to be a taper building mechanism that allowed the fold thrust belt to continue propagating eastward

sources sinks and storage of river sediment in the atlantic drainage of the united states the history of sediment and its movement in the atlantic drainage demonstrate some of the difficulties of modeling sediment on a river basin scale soil erosion was accelerated by a factor of at least 10 when european settlers cleared forests and planted crops although increasing soil conservation practice and decreasing crop farming have since reduced the rates of erosion large quantities of eroded material are still stored on hillslopes and in stream valleys where they continue to augment the sediment loads of the rivers the sediment from this episode of erosion that is largely past can be expected to emerge from storage for many decades and perhaps even several centuries to come the reservoirs that have been built on many of the major rivers trap significant portions of the moving sediment which in some places may be remobilized by large floods essentially all the river sediment that reaches the atlantic coastal zone is trapped in estuaries and coastal marshlands probably less than 5 is deposi

development of extension faults on the oblique thrust ramp hanging wall example from the tethys himalaya abstract inhomogeneous strain at late stages of deformation of modelling clay models with frontal and oblique thrust ramp geometries results in formation of extension faults on the hanging wall the extension faults trend nearly parallel to the axis of maximum compression and orthogonal to the trend of the frontal ramp faults with similar geometries occur in the upper satluj river basin of the tethys himachal himalaya the experimental results help in understanding the present day normal faulting and related active tectonics of the area

geometric analysis of fold development in overthrust terranes abstract fault bend folding fault propagation folding and detachment or decollement folding are three distinct scenarios for fold thrust interaction in overthrust terranes simple kink hinge models are used to determine the geometric associations implicit in each scenario bedding maintains constant thickness in the models except in the forelimb of the fold the forelimb is allowed to thicken or thin without limit the models address individual folds and the calculated fold geometries are balanced structures each mode of fold thrust interaction has a distinct set of geometric relationships final fold geometry is adequate in itself to discern many fault bend folds this is not the case for fault propagation and detachment folds these two fold forms have very similar geometric relationships some knowledge of the nature of the underlying thrust or decollement zone is usually needed to distinguish between them the geometry of a fold is altered in a predictable fashion by transport through an upper ramp hinge and by fault parallel shearing of the structure the shearing results in a tighter fold whereas transport through the ramp hinge produces a broader fold the viability of the geometric analysis technique is demonstrated through its application to a pair of detachment folds from the canadian cordillera the geometric analysis is also used to evaluate cross sections through subsurface structures in an example from the turner valley oil field the analysis indicates how the interpretation should be altered so as to balance the cross section the analysis reveals hidden assumptions and specific inconsistencies in structural interpretations

sediment accumulation rate in the lakes of kumaun himalaya india using 210 pb and 226 ra the rate of sedimentation and the source of sediments in the lake basins of nainital region kumaun himalaya have been estimated employing210pb and210ra methods this has yielded a rate of sedimentation of 11 5 4 70 3 72 and 3 00 mm yr in nainital bhimtal naukuchiyatal and sattal lakes respectively the higher rate of sedimentation in nainital lake compared to other lakes is related to faster erosion in the catchment aided by greater anthropogenic activity while the slowest rate in sattal lake is due to less erosion and more input of soil derived material involving a slow rate of accumulation

contrasting styles of fault reactivation in curved orogenic belts examples from the central apennines italy the geometry of the apennine fold and thrust belt has been strongly influenced by the original architecture of the adria paleomargin in the central apennines pre thrusting normal faults pre orogenic permian triassic jurassic and synorogenic neogene were reactivated with compressional kinematics during the neogene quaternary orogenesis we present a study of the control of preexisting extensional faults on thrust tectonics in the central apennines we describe positive inversion geometries of some salient fold and thrust structures from the central apennines setteporte the sabini mountains the sibillini mountains montagna dei fiori the gran sasso range maiella mountain and casoli bomba by integrating surface geological data and seismic line interpretation in these structures different styles of fault reactivation depend on their orientation with respect to the subsequent compressional ne sw trending stress field the nw se and wnw ese trending pre thrusting normal faults in the backlimbs of the anticlines were displaced and passively translated in the hanging wall blocks of the thrust planes thus exhibiting a classical shortcut geometry shortcut anticlines differently pre orogenic normal faults in the n s trending anticlines were reactivated in a transpressive deformational context as documented by the mainly dip slip and strike slip kinematics along the thrusts and back thrusts respectively reactivation anticlines the cases studied document differences in geometry in fold and thrust structures related to the trend of preexisting extensional faults showing that different reactivation geometries linked to the same inversion event can coexist at regional scale in curved fold and thrust belts the proposed inversion tectonic model and the resulting geometry of the fold and thrust belt could possibly be applied to analogous orogenic belts

analogue modeling of positive inversion tectonics along differently oriented pre thrusting normal faults an application to the central northern apennines of italy inversion tectonics represent a key process in many orogens worldwide the related mechanisms of fault reactivation and the effects of an articulated preshortening setting on thrust and fold development are still challenging questions modes and geometries of inversion have been the object of several analogue models in this work we analyzed the influence of an articulated high angle preexisting discontinuity in the development of thrusts using sandbox modeling the model geometry is based on the architecture of the major faults in the central northern apennines of italy where differently oriented mesozoic cenozoic inherited extensional structures are clearly detectable and display contrasting styles of positive inversion tectonics quartz sand is the analogue material adopted to model mesozoic cenozoic sedimentary successions and glass microbeads represent preexisting fault rocks the geometry of the segmented preexisting structure is composed of two segments with the same dip 60 one oblique and another orthogonal to the shortening direction our results show that different styles of positive inversion tectonics can coexist and that the obliquity angle between inherited structures and the shortening direction is a leading factor controlling the degree of inversion the oblique segment of the discontinuity exhibits a complete reactivation whereas along the orthogonal segment shortcut is the prevalent mechanism the oblique element moreover represents a cross strike discontinuity that guides the localization and curved geometry of the thrusts compartmentalizing the deformation our findings can be applied to fold and thrust belts characterized by the presence of cross strike discontinuities

erratic shortening from balanced cross sections of the western himalayan foreland basin causes and implications for basin evolution abstract balanced cross sections from the western himalayan foreland foothill belt reveal a variation in shortening amounts from 22 to 71 3 over a lateral distance of 85 km the large variation may be attributed to the fact that the method of cross section balancing considers the initial layering as horizontal which is an unlikely situation in foreland basins simple trigonometric relationships are used to minimize the error in shortening estimates however the suggested corrections could not be applied to the himalayan foreland basin because of unavailability of the required data on initial basin geometry the study also indicates that shortening rates for the area based on these shortening amounts cannot be used for earthquake prediction

surface lithologic heterogeneity of asteroid 4 vesta abstract high precision spectrophotometry of 4 vesta the third largest asteroid was used to establish the surface composition of this body and to investigate mineralogical variations across its surface the average surface of vesta is analogous to howardite and or polymict eucrite assemblages regolith derived members of the hed meteorite suite which consist of a eucrite matrix containing differing amounts of a diogenite component color and or spectral changes which exhibit a consistent relationship to rotational phasing are evident in 16 of 18 studies of vesta dating back to 1929 including the present work after elimination of possible sources of spurious spectral or color changes it is concluded that these variations arise from hemispheric variations in surface materials and hence provide a means of spatially resolving subhemispheric compositional units on the surface of vesta the background surface of vesta is a relatively dark howardite or polymict eucrite pyroxene plagioclase assemblage with several compositionally distinct bright regions clustered in one hemisphere viewed around the maximum in vesta s lightcurve these include what appears to be an olivine bearing unit suggested name leslie formation located near vesta s equator which probably represents an impact basin and or its associated ejecta that penetrated through the basaltic crust other high albedo compositional units including an apparently low calcium eucrite region and several diogenite pyroxenite regions at least one located near the southern pole may be smaller shallower impact basins by analogy to the eucrite meteorites which represent surface flows or shallow intrusions and which constitute the major component of the regolith derived howardites and polymict eucrites we conclude that the howardite polymict eucrite units represent a regolith gardened original surface of vesta it is probable that the low albedo of the background surface on vesta is due to an age related darkening effect similar to that inferred from the galileo images of gaspra and ida this mechanism is consistent with the correlation of absorption feature intensity with the lightcurve vesta appears to have an old eucritic surface darkened with age and represented among the meteorites by the regolith derived howardites and polymict eucrites on which several impacts on one hemisphere have exposed fresher brighter diogenite and olivine bearing material based on qualitative analysis of the mineralogical variations as a function of rotation a generalized lithologic map of vesta was produced there is reasonable control on the longitude of lithologic features but little control on their latitudes except where specifically noted in producing this map discrete circular features were used on the plausible assumption that impacts have been the most important geologic process on this surface for most of the age of the solar system the shape of the features has thus been assumed rather than derived and is subject to future revision as data improve

multidisciplinary approach to constrain kinematics of fault zones at shallow depths a case study from the cameros demanda thrust north spain thrusting at shallow depths often precludes analysis by means of structural indicators effective in other geological contexts e g mylonites sheath folds shear bands in this paper a combination of techniques including structural analysis magnetic methods as anisotropy of magnetic susceptibility and paleomagnetism and paleothermometry is used to define thrusting conditions deformation and transport directions in the cameros demanda thrust north spain three outcrops were analyzed along this intraplate large scale major structure having 150 km of outcropping length 30 km of maximum horizontal displacement and 5 km of vertical throw results obtained by means of the different techniques are compared with data derived from cross sections and stratigraphic analysis mixed layer illite smectite and vitrinite reflectance indicating deep diagenetic conditions and mature stage of hydrocarbon generation suggests shallow depths during deformation thus confirming that the protolith for most of the fault rocks is the footwall of the main thrust kinematic indicators foliation s c structures and slickenside striations indicate altogether a dominant nnw movement of the hanging wall in the western zone and ne in the eastern zone of the thrust thus implying strain partitioning between different branches of the main thrust the study of ams in fault rocks nearly 400 samples of fault gouge breccia and microbreccia indicates that the strike of magnetic foliation is oblique to the transport direction and that the magnetic lineation parallelizes the projection of the transport direction onto the k max k int plane in sites with strong shear deformation paleomagnetism applied to fault rocks indicates the existence of remagnetizations linked to thrusting in spite of the shallow depth for deformation and a strong deformation or scattering of the magnetic remanence vectors in the fault zone the application of the described techniques and consistency of results indicate that the proposed multidisciplinary approach is useful when dealing with thrusts at shallow crustal levels

sandbox experiments of inverted listric and planar fault systems abstract the kinematic and geometric evolution of basement controlled inversion structures has been analyzed using a plane strain sandbox apparatus the results of two representative scaled analogue models comprising rigid listric and planar detachment faults that both have cut off angles of 60 to the horizontal are described in detail the hangingwall above these detachment geometries was constructed from alternate layers of sand and mica in order to simulate an anisotropic sedimentary sequence in both experiments initial shortening at the onset of inversion was accommodated by bulk strain this was followed by reactivation of the basal detachment together with the main basin controlling planar and listric faults which propagate upwards through the post rift sequence at approximately the same angle as the upper part of the detachment fault i e 60 reactivation of relatively steep intra basinal extensional faults within the cover was restricted to nucleation of reserve faults and thrusts in the region of the tips during approximately the first 10 to 15 contraction this resulted in gently dipping thrusts that propagated upwards through the post rift sequence to produce harpoon shaped structures later in the inversion phase after approximately 15 contraction backthrusts cut through and displaced the original antithetic extensional graben faults producing downward tapering wedge shaped structures at the margins of the basin although deformation in these experiments was limited to purely dip slip displacement the nature of the original extensional faults and their reactivated tip regions resulted in cross sectional geometries that have a marked resemblance to strike slip induced flower structures uplift was asymmetric and centred above the upper part of the main detachment above the listric fault but was more symmetrical and centred above the soling out point of the detachment in the case of the planar fault geometry the results of these experiments show distinct similarities to structures seen on seismic sections form the southern north sea and other inverted sedimentary basins

quaternary reactivation of flexural slip folds by diapiric activity example from the western ebro basin spain in the western sector of the ebro basin two types of structures deform the quaternary terraces and pediments developed by the ebro river and its tributaries 1 folds up to 10 km long in the lower levels of fluvial terraces and 2 normal listric faults that produce tilting and rollover anticlines of the quaternary deposits both types of structures are linked to the geometrical and lithological features of the tertiary beds that underlie the quaternary deposits quaternary folds whose axes are parallel to the strike of the tertiary beds are the result of reactivation of tertiary large scale 60 km long folds due to diapirism of their gypsum cores where the gypsum units reach a maximum thickness of 3 000 m this reactivation produced flexural slip in some beds on the limbs of the folds bringing about the folding of the overlying quaternary terraces the mechanism of quaternary folding involves layer parallel shear in alternating tertiary units and folding linked to detachments and reverse layer parallel faults normal listric faults are widespread throughout the studied area they are partly parallel to low dipping tertiary beds and are the result of a nne ssw tectonic extension compatible with minor structures and focal mechanisms of recent earthquakes the relationship between the two kinds of quaternary structures indicates that diapirism of the gypsum cores of the anticlines was activated by extensional tectonics

the role of fluid pressure in the formation of bedding parallel thrust hosted gold deposits sabie pilgrim s rest goldfield eastern transvaal abstract shallowly dipping thrust hosted gold veins occur within the paleoproterozoic transvaal supergroup rocks in the eastern transvaal of south africa internally the veins record episodic events of fluid infiltration and subsequent mineral deposition within discrete local scale thrust faults evidence also exists for subvertical dilation within the individual veins and textures which record open space filling are preserved the probable depth of formation suggests lithostatic pressures in excess of 2 2 kbar and the vein textures indicate numerous reactivation events associated with individual thrust faults occurring in a terrain characterised by low levels of preserved strain fault reactivation may have occurred under conditions of low differential stress in the presence of high pressure fluids with p fluid approaching or exceeding lithostatic levels

evolution of late holocene coastal dunes in the cauvery delta region of tamil nadu india widespread occurrences of coastal dunes are observed in the cauvery delta region of tamil nadu in vedaranniyam in the south east coast of india these dunes were studied to establish the chronology of their formation and to understand their evolution using optically stimulated luminescence osl dating in combination with sedimentological studies quartz grain surface morphology using scanning electron microscope grain size and heavy mineral analysis the study shows that on the south east coast of india widespread periodic dune formation reactivation has taken place during the late holocene to very recent times due to a variety of reasons such as climatic variation and land use changes the sand mobility index shows that the dunes in the area have been largely active during the past century in the southern part in nagapattinam region and many of the crests were active in the northern cauvery delta in cuddalore region the angularity and fresh appearance of sand in the inland dunes suggest a short distance of sand transport and a source proximal sand deposition was proposed for the dune formation the study demonstrates the sensitivity of sand dunes on the south east coast of india to varying climatic conditions and changes in regional land use

doppler weather radar as a meteorite recovery tool abstract we report the use of doppler weather radar as a tool for locating meteorites both at the time of a fall and from archived radar data this asset is especially useful for meteorite recovery as it can provide information on the whereabouts of falling meteorites in dark flight portion of their descent where information on their flight paths cannot be discerned from more traditional meteorite location techniques such as eyewitness accounts weather radar data can provide information from detection in three distinct regimes a direct detection of the rapidly moving optically bright fireball by distant radars b detection of falling debris to include hand sample sized rocks and c detection of dust produced by detonation events that can occur tens of minutes and many kilometers laterally removed from the actual fireball locality we present examples of each as well as comparisons against man made debris from a re entering soyuz rocket and the stardust sample return capsule the use of doppler weather radar as a supplement to traditional meteorite recovery methods holds the promise of improving both the speed and total number of meteorite recoveries thereby increasing the number of freshly fallen meteorites for scientific study

radar enabled recovery of the sutter s mill meteorite a carbonaceous chondrite regolith breccia doppler weather radar imaging enabled the rapid recovery of the sutter s mill meteorite after a rare 4 kiloton of tnt equivalent asteroid impact over the foothills of the sierra nevada in northern california the recovered meteorites survived a record high speed entry of 28 6 kilometers per second from an orbit close to that of jupiter family comets tisserand s parameter 2 8 0 3 sutter s mill is a regolith breccia composed of cm mighei type carbonaceous chondrite and highly reduced xenolithic materials it exhibits considerable diversity of mineralogy petrography and isotope and organic chemistry resulting from a complex formation history of the parent body surface that diversity is quickly masked by alteration once in the terrestrial environment but will need to be considered when samples returned by missions to c class asteroids are interpreted

earthquake slip estimation from the scarp geometry of himalayan frontal thrust western himalaya implications for seismic hazard assessment geometric and kinematic analyses of minor thrusts and folds which record earthquakes between 1200 ad and 1700 ad were performed for two trench sites rampur ghanda and ramnagar located across the himalayan frontal thrust hft in the western indian himalaya the present study aims to re evaluate the slip estimate of these two trench sites by establishing a link between scarp geometry displacements observed very close to the surface and slip at deeper levels as geometry of the active thrust beneath the scarp is unknown we develop a parametric study to understand the origin of the scarp surface and to estimate the influence of ramp dip the shortening estimates of rampur ghanda trench by line length budget and distance displacement d d method show values of 23 and 10 15 respectively the estimate inferred from the later method is less than the line length budget suggesting a small internal deformation ramnagar trench shows 12 shortening by line length budget and 10 25 by the d d method suggesting a large internal deformation a parametric study at the trenched fault zone of rampur ghanda shows a slip of 16 m beneath the trailing edge of the scarp and it is sufficient to raise a 8 m high scarp this implies that the rampur ghanda scarp is balanced with a single event with 7 8 m coseismic slip in the trenched fault zone at the toe of the scarp 8 15 mean deformation within the scarp and 16 m slip at depth along a 30 ramp for a pre 1400 earthquake event a 16 m slip is the most robust estimate of the maximum slip for a single event reported previously by trench studies along the hft in the western indian himalaya that occurred between 1200 ad and 1700 ad however the ramnagar trenched fault zone shows a slip of 23 m which is larger than both line length and d d methods it implies that a 13 m high scarp and 23 m slip beneath the rigid block may be ascribed to multiple events it is for the first time we report that in the south eastern extent of the western indian himalaya ramnagar scarp consists of minimum two events i pre 1400 ad and ii unknown old events of different lateral extents with overlapping ruptures if the more optimistic two seismic events scenario is followed the rupture length would be at least 260 km and would lead to an earthquake greater than mw 8 5

formation of decollement upwarps during thrusting geometric and kinematic models reveal that rotation of layers during thrusting or development of drag folds produced by movement along listric thrust faults results in the formation of dilation space at the junction of the thrust ramp with the basal decollement this is accompanied by upwarping of the basement to occupy the available space thereby producing an antiformal structure which restricts the thrust displacement the structure is termed a decollement upwarp and examples are cited from the foothill belt of the himalaya

evidence for mesoarchean 3 2ga rifting of the pilbara craton the missing link in an early precambrian wilson cycle abstract a sequence of c 3 2 ga low grade sedimentary rocks bimodal volcanic rocks and subvolcanic layered mafic ultramafic sills and dykes occur in greenstone belts that flank the margins of the 3 51 3 24 ga east pilbara terrane of the pilbara craton western australia u pb shrimp zircon data and sm nd model age data suggest that these rocks represent juvenile addition of material to the margins of the craton during a period of major extension accompanied by the local emplacement of granitic rocks this extensional event is also represented in adjacent terranes by thick basalt flows with c 3 2 ga zircon and sm nd model ages and by granitic rocks based on the available age data geochemistry of basaltic rocks and the distribution of this event in space and time within the craton we interpret the c 3 2 ga rocks to reflect widespread rifting of the protocraton and associated thinning of the lithosphere this event resulted in separation of the flanking kurrana and karratha terranes from their parent east pilbara terrane which represents the ancient nucleus of the craton these terranes were then reassembled during subsequent accretion at 3 07 2 905 ga combined the data suggest the preservation of a mesoarchean wilson cycle in the pilbara craton

variation in geometries and displacement along thrust faults a quantitative analysis from sandbox models the present work combines theoretical analysis laboratory experiments and field examples together with quantitative analysis to understand displacement variation along fault surfaces with varying dip angle two sandbox experiments are described to quantitatively analyze the interactions between shortening and sedimentation during late stages of deformation the two models consisted of sand layers with single and two microbeads layer s within the sandpack sieved over horizontal frictional detachment the models demonstrate that the overlying sediment load bears a major role on kinematic of developing structures fault displacement varied along imbricate thrusts due to variation in fault dip angle in the listric geometry maximum displacement occurred in the up dip direction up section or near fault tip along the faults where fault dip angles were shallower and favourable for thrust displacement in contrast the displacement was limited in the down dip direction down section or near basal detachment where fault dip angles were steeper the variation in fault displacement with fault dip along the fault surfaces made it possible to establish an inverse relationship between the fault dip and related displacement values i e lower is the dip angle greater the displacement and vice versa despite the inherent limitations and assumptions of laboratory experiments application of results to natural examples sheds new light on the mechanics and geometry of thrust faults from the deep to shallow structural levels as well as structural patterns that could appear as anomalous at a first sight

infrared imaging spectroscopy with micron resolution of sutter s mill meteorite grains synchrotron based fourier transform infrared spectroscopy and raman spectroscopy are applied with submicrometer spatial resolution to multiple grains of sutter s mill meteorite a regolith breccia with cm1 and cm2 lithologies the raman and infrared active functional groups reveal the nature and distribution of organic and mineral components and confirm that sm12 reached higher metamorphism temperatures than sm2 the spatial distributions of carbonates and organic matter are negatively correlated the spatial distributions of aliphatic organic matter and oh relative to the distributions of silicates in sm2 differ from those in sm12 supporting a hypothesis that the parent body of sutter s mill is a combination of multiple bodies with different origins the high aliphatic ch2 ch3 ratios determined from band intensities for sm2 and sm12 grains are similar to those of idps and less altered carbonaceous chondrites and they are significantly higher than those in other cm chondrites and diffuse ism objects

experimental models of hangingwall deformation in ramp flat listric extensional fault systems abstract the results of three experimental models of ramp flat extensional fault systems are presented the experiments were constructed from sand and mica layers to form an anisotropic sequence that would respond to the imposed deformation by both faulting and folding the geometry of the underlying detachment controls the deformation in the hangingwall sequence ramp flat detachment geometries produce an upper roll over with a crestal collapse graben system a ramp syncline and fold reverse fault zone and a lower roll over with a crestal collapse graben system short ramp geometries produce only minor perturbations in a larger roll over structure as extension progresses the crestal collapse systems migrate and superimpose earlier systems the models of ramp flat extensional structures produce templates for the interpretation of natural ramp flat listric fault systems

younger hanging wall rocks along the vaikrita thrust of the high himalaya a model based on inversion tectonics abstract in sharp contrast to the common observed characteristic of areas of thrust tectonics where older rocks are thrust over younger along the vaikrita thrust in the high himalaya younger hanging wall rocks i e vaikrita group late mesoproterozoic to early neoproterozoic lie above the older footwall rocks i e munsiari formation paleoproterozoic the phenomenon is explained by an inversion tectonics based model where normal faulting and metamorphism were followed by thrusting in which the thrust displacement was less than the displacement during the earlier normal faulting the present day hanging wall tilt towards north may have been caused by a later thrust initiated as a piggy back sequence accompanied by folding and himalayan metamorphism

thermochronology of the needle falls shear zone a post collisional high strain zone of the trans hudson orogen the needle falls shear zone is a major paleoproterozoic discontinuity separating an archean craton from accreted paleoproterozoic terranes in the western trans hudson orogen it is a 1 km wide subvertical mylonite zone forming the southwestern sector of a northeast trending shear system extending for more than 400 km kinematic data indicate oblique east side up dextral strike slip displacement throughout its evolution from ductile through late brittle deformation for most of its exposed length it marks the northwestern margin of the wathaman batholith the oldest pb evaporation ages of zircons from mylonite average 1857 ma consistent with published zircon ages of the wathaman batholith confirming the batholith is protolith for much of the shear zone the synkinematic metamorphic assemblage of amphibole biotite quartz feldspar signifies deformation under amphibolite facies conditions 500 630 c oxygen isotope fractionations between quartz hornblende and quartz biotite pairs in textural equilibrium

kinematics of experimental forced folds and their relevance to cross section balancing abstract we report the results of a series of laboratory experiments in which packages of layers consisting of rock and lead are deformed under 50 mpa confining pressure into forced folds by the uplift and rotation of pre machined steel forcing blocks the models are not fully scaled but the geometries resulting form the deformation are remarkably similar to many natural forced folds observed in the u s rocky mountains foreland during the folding detachment and quantifiable layer parallel translation occur between the layered sequence and the forcing assembly confirming limited observations from earlier model studies away from the fold there is a pattern of movement in which the layered sequence first moves away from the uplift but with greater structural relief those motions reverse their sense to become layer parallel translations towards the uplift the very ductile lead unit at the base of the layered sequence flows laterally especially across the crest of the uplift to the downthrown block in response to pressure gradients which are inherent to asymmetric uplifts the flow of this ductile unit causes layer parallel translation of the rock layers thereby transporting material into the fold if the models were to be treated as proposed cross sections and if they were subjected to the usual techniques of cross section balancing incorrect interpretations would result this is because there are no suitable sites for either pin lines or no flow boundaries

role of inversion tectonics in structural development of the himalaya abstract analysis of surface and subsurface structures variation of shortening amounts obtained by restoration of deformed cross sections and occurrence of younger hangingwall rocks over the older footwall rocks across the vaikrita thrust in the higher himalaya suggests reactivation of early normal faults as thrusts based on this an inversion tectonics model is proposed for structural development of the himalaya the model explains the geometrical shape of the himalaya as primary arcuation and helps in resolving superimposed deformation in the region

response discussion of morphotectonic records of neotectonic activity in the vicinity of north almora thrust zone central kumaun himalaya by kothyari et al 2017 geomorphology 285 272 286 abstract rana and sharma 2017 dispute our tectonic interpretation mainly on the basis of what they believe climate however we welcome their comments as this gives us a chance to highlight the ambiguity inherent in discriminating the climate tectonic imprints in morphotectonic records that are prevalent in current research we should note that the paper published by kothyari et al 2017 was reviewed by national international reviewers we would like to emphasize the fact that the paper does not rule out the role of climate however most importantly it presents significant features and observations that collection assemblage points toward the dominant role of tectonics in their shaping and not solely climate as postulated by rana and sharma 2017 the objective of this paper is to identify tectonic signatures geomorphology in a monsoon dominated tectonically active terrain like the north almora thrust nat these faults are marked by previous workers based on field evidence such as folding and faulting of lithological units presence of slickensides parallel to the fault offset of nat owing to a transverse fault and offset of drainage drainage basin analysis strath terraces fluviolacustrine terraces development of scarp narrow river course and deeply incised valleys however we disagree with the comments raised by rana and sharma 2017 because they are highly skewed toward the climate school of thought and did not perceive the setting as a collection of landforms instead they attempted to view them in isolation because these comments are important we will try to further our research incorporating issues related to isolation of climate and tectonics imprints in the immediate future we would like to thank rana and sharma 2017 for raising some basic questions on our work as this gave us an excellent opportunity to summarize and present the dominance of various processes and related landforms as earlier reported by kothyari et al 2017 a point by point detailed rebuttal explanation of their queries is provided below

a reevaluation of the position of the baie verte brompton line in the quebec appalachians the influence of middle devonian strike slip faulting in gaspe peninsula the baie verte brompton line bbl the surface expression of the taconian suture in the canadian appalachian orogen extends from southern quebec to the northeast end of newfoundland in the que

contemporary tectonics of the himalayan frontal fault system folds blind thrusts and the 1905 kangra earthquake the sub himalayan fold thrust belt consists of deformed late cenozoic and older deposits south of the main boundary thrust mbt in pakistan east of the indus river the sub himalaya comprises the potwar plateau and the salt range which is thrust southward over the jhelum river floodplain along the salt range thrust although an estimated 9 14 mm a 1 shortening has been taken up on the salt range thrust during the last 2 ma the range front scarp does not show signs of recent faulting shortening may be shifting southward to the lilla overpressured anticline which rises from the jhelum floodplain as a fault propagation fold farther east shortening is partitioned among several anticlines underlain by foreland and hinterland dipping blind thrusts southeast of the main deformation zone the pabbi hills overpressured anticline is best explained as a fault propagation fold throughout the potwar plateau and salt range thrusts and folds rise from a basal decollement horizon in eocambrian evaporites the pakistani part of the decollement horizon could generate large earthquakes only if these evaporites die out northward at seismogenic depths in india and nepal the sub himalaya is narrower reflecting the absence of evaporites and a steeper slope of the basement towards the hinterland the southern boundary of the sub himalaya is the himalayan front fault discontinuous because part of the shortening is expressed at the surface by folding broad alluvial synclinal valleys dun valleys are bounded on the south by rising barrier anticlines of siwalik molasse the 1905 kangra earthquake m8 produced uplift on the mohand anticline and the dehra dun valley suggesting that this earthquake occurred on a decollement horizon above basement downdip from the fold if so the kangra event is the largest known earthquake on a blind thrust expressed at the surface as a fold

book review the techniques of modern structural geology volume 2 folds and fractures john g ramsay and martin i huber academic press london 1987 xi 309 398 pp price stg17 50 us 34 50 paperback

sediment and heavy metal accumulation in the cauvery basin eleven cores were collected from the cauvery basin radiometric dates were used to determine modern sediment accumulation rates sediment accumulation rates ranged from 0 4 to 4 mm yr heavy metal concentration decreases with the increase of depth the heavy metal concentrations at certain depths are attributed to the irregular input of metals and their remobilization heavy metal accumulations have been computed using sediment accumulation rates and accumulation rates show an additional anthropogenic input of metals and sediments in the recent past factor analysis and correlation analysis show the diverse source and accumulation mechanism influencing the metal distribution in the basin

late holocene mangrove dynamics and coastal environmental changes in the northeastern cauvery river delta india abstract a palaeoclimate and palaeoecological study was carried out using sedimentological palynological and thecamoebian evidence in a 5 m deep sediment core deposited since 3630 cal bp from tspettai mangrove wetland northeastern part of cauvery river delta textural analysis shows the overall predominance of fine clay with intermittent phases of sand the palynological climatic period inferred in phase i 3630 3170 cal bp shows a stabilized estuarine ecosystem conducive for mangroves along with a good percentage of hinterland forest indicating a warm and humid climate with strengthened monsoon phase iia 3170 2600 cal bp shows abundance of salt tolerant mangroves along with a mixed forest suggesting climatic amelioration from warm and humid to dry and arid phase iib 2600 1300 cal bp shows the dominance of salt tolerant species indicating enhanced dry and arid climate coupled with weakened monsoon phase iii since 1300 cal bp is characterized by rejuvenation of true mangroves and high percentages of salinity tolerant mangroves with a low percentage of thecamoebians thereby indicating increased salinity induced by weakened monsoon and enhanced anthropogenic activity it is inferred that during the past 3 millennia climate changed from warm and humid to cool and arid conditions with an evolution of vegetation from moist to dry deciduous forest the qualitative and quantitative study shows a decline in the true mangroves and an increase in the salt tolerant vegetation which is attributed to the increased salinity in the wetland due to high salt accumulation in the root zone which is vulnerable for mangroves

the fall of the grimsby meteorite i fireball dynamics and orbit from radar video and infrasound records abstract the grimsby meteorite h4 6 fell on september 25 2009 as of mid 2010 13 fragments totaling 215 g have been recovered records of the accompanying fireball from the southern ontario meteor network including six all sky video cameras a large format ccd infrasound and radar records have been used to characterize the trajectory speed orbit and initial mass of the meteoroid from the four highest quality all sky video records the initial entry velocity was 20 91 0 19 km s 1 while the derived radiant has a local azimuth of 309 40 0 19 and entry angle of 55 20 0 13 three major fragmentation episodes are identified at 39 33 and 30 km height with corresponding uncertainties of approximately 2 km evidence for early fragmentation at heights of approximately 70 km is found in radar data dynamic pressure of this earliest fragmentation is near 0 1 mpa while the main flare at 39 km occurred under ram pressures of 1 5 mpa the fireball was luminous to at least 19 7 km altitude and the dynamic mass estimate of the largest remaining fragment at this height is approximately several kilograms the initial mass is constrained to be 100 kg from infrasound data and ablation modeling with a most probable mass of 20 50 kg the preatmospheric orbit is typical of an apollo asteroid with a likely immediate origin in either the 3 1 or 6 resonances

hangingwall bed rotation and the development of contractional and extensional structures around a thrust fault geometric and experimental models abstract tectonic inversion of normal faults and development of extensional and contractional structures in the vicinity of thrust faults were studied using two models i a geometric or rigid model and ii an experimental or brittle ductile model the first model is based on simple trigonometric relationships between shortening rotation of layers along a thrust and dip of the thrust the model may be used to understand the structures at upper levels of the earth s crust in a predominant brittle regime the second model is based on a series of experiments performed with clay analogues it simulated the structures forming at a deeper level in a brittle ductile regime and incorporates folding as an essential feature the results of the study reveal that structures near a thrust fault depend on the thrust geometry and dip amount the initial orientation of hangingwall layers and their rheological properties in the absence of frictional effects along a thrust surface the rotation of layers and consequent displacement is directly proportional to the thrust dip since the listric faults are characterized by a decrease of dip with depth the variation in the rotation of layers in a profile section may result in formation of dilation spaces that may serve as potential sites for secondary mineral deposits or oil traps a large rotation of hangingwall layers results in a reverse fault drag and a small rotation caused by frictional effects along the fault produces normal fault drag

relationship of e type apollo asteroid 3103 1982 bb to the enstatite achondrite meteorites and the hungaria asteroids visible and near infrared observations confirm that apollo asteroid 3103 1982 bb has a reflectance spectrum consistent with its previous assignment to taxonomic type e it has been generally believed that the e type asteroids are analogous and perhaps even genetically related to the enstatite achondrite meteorites aubrites correlated variations of previously published visible and thermal infrared lightcurves and the lack of rotational color variations in the present data indicate that this is an elongated object with no substantial surface albedo variations apollo asteroid 3103 1982 bb is presently in an orbital resonance 3 5 with earth and appears to be a relatively long lived member of the earthapproaching population its orbit is consistent with both the fall dates and long cosmic ray exposure ages of the aubrites combined with the rarity of e type asteroids in the near earth asteroid population this indicates that 3103 1982 bb is probably either a major or the primary immediate source body of the aubrites the aphelion location and the mineralogy of 3103 1982 bb indicate that it was most probably derived from the hungaria region at the innermost edge 1 9 au of the asteroid belt although the exact dynamical mechanism for producing its present orbit is not clear these results represent the first plausible direct link of a set of meteorites aubrites or enstatite achondrites back to a particular source region in the asteroid belt this link allows the composition of the solar nebula to be constrained at that heliocentric distance during the time interval when the parent assemblage of the aubrites was isolated from contact with the nebular gas by accretion into its parent planetesimal 1992 academic press inc

from carbonate sulphate interbeds to carbonate breccias the role of tectonic deformation and diagenetic processes cameros basin lower cretaceous n spain interpreting the origin of carbonate breccias requires a detailed analysis because they may be the result of a wide variety of processes that produce similar features this is the case of the lower cretaceous carbonate breccias of the cameros basin previously interpreted as slump or collapse breccias whose origin is interpreted after performing a detailed sedimentary petrographic and tectonic study the studied carbonate breccias consist of angular carbonate mudstone fragments floating in a matrix of calcite and quartz crystals the breccias are interbedded with and laterally associated to alternating layers of carbonate mudstone and calcite and quartz pseudomorphs after gypsum which show strong similirities to the breccia fragments and matrix respectively suggesting that the brecciated beds were originally composed of identical alternating carbonate mudstone and gypsum layers as the unbrecciated layers the breccias are associated with frequently polyharmonic deformation structures which are similarly oriented as the regional tectonic structures indicating that they are related with the alpine contractional deformation of this area of the cameros basin all these features suggest that the carbonate breccias were formed by tectonic deformation of alternating layers of carbonate mudstone and calcium sulphate which have very different rheological behaviours as a result during tectonic deformation sulphate flowed and carbonate layers were broken and displaced producing a breccia of carbonate fragments within a sulphate groundmass afterwards the sulphate groundmass was replaced by quartz and calcite and the breccia acquired its final composition

growth of the central andean plateau by tectonic segmentation is controlled by the gradient in crustal shortening abstract crustal deformation orocline formation and growth of the central andean plateau as well as the mutual relations of these processes with climate are a matter of international debate earthquake focal mechanism fault kinematic paleomagnetic and cross section balancing data are paramount for understanding the morphotectonic evolution of this noncollisional orogen but collectively await an explanation in terms of a comprehensive kinematic model we offer such a model that approximates simple shear in plan view and that predicts the kinematics of first order fault zones in the southern central andes the model indicates that segmentation of the upper crust into rhomb shaped domains confined by transpressive ranges resulted from the decrease in crustal shortening with distance to the central bend of the andes an anastomosing network of kinematically coupled reactivated orogen parallel and newly formed ne trending deformation zones encompassing components of sinistral and dextral strike slip res

large magnitude continental extension an example from the central mojave metamorphic core complex the central mojave metamorphic core complex is defined by a belt of miocene brittle ductile extension and coeval magmatism the brittle ductile fault zone defines a basin and dome geometry that results from the interference of two orthogonal fold sets that we infer to have formed by mechanically independent processes one fold set contains axes that lie parallel to the extension direction of the shear zone and has a maximum characteristic wavelength of about 10 km the axial surfaces of these folds can be traced from the footwall mylonites through the brittle detachment and into hanging wall strata however folds of mylonitic layering have smaller interlimb angles than those of the brittle detachment suggesting that the folds began to form during ductile shearing and continued to amplify in the brittle regime possibly after movement across the fault zone ceased mesoscopic fabrics related to the transport parallel fold set indicate that the folds record true crustal shortening perpendicular to the extension direction we interpret these folds to form in response to elevated horizontal compressive stress perpendicular to the extension direction and suggest that this stress regime may be a natural consequence of large magnitude extension the other fold set has axes perpendicular to the extension direction and a characteristic maximum wavelength of about 50 km mesoscopic fabrics related to these folds include northwest striking joints kink bands and en echelon tension gash arrays these fabrics formed after mylonitization and record both layer parallel extension and northeast side up subvertical shear the postmylonitic fabrics are kinematically compatible with rolling hinge style isostatic rebound of the footwall following tectonic denudation the relative timing of extension related magma intrusion and ductile deformation varies through the central mojave metamorphic core complex on the scale of the small mountain ranges that make up the central mojave metamorphic core complex no correlation was observed between either shear zone thickness or intensity of ductile deformation and either the proximity or relative volume of extension related igneous rocks this suggests that models that invoke a single upper crustal genetic relationship such as magmatism triggering extension or vice versa do not apply to the central mojave metamorphic core complex systematic variation in the relative timing of dike emplacement and mylonitization suggests that at the time of dike emplacement rocks in the mitchel range were below the brittle ductile transition while those in the hinkley hills were above it the hinkley hills and mitchel range are separated by 2 km in the dip direction of the fault zone which suggests that the vertical thickness of the brittle ductile transition probably was between 100 and 950 m

detection and rapid recovery of the sutter s mill meteorite fall as a model for future recoveries worldwide the sutter s mill c type meteorite fall occurred on 22 april 2012 in and around the town of coloma california the exact location of the meteorite fall was determined within hours of the event using a combination of eyewitness reports weather radar imagery and seismometry data recovery of the first meteorites occurred within 2 days and continued for months afterward the recovery effort included local citizens scientists and meteorite hunters and featured coordination efforts by local scientific institutions scientific analysis of the collected meteorites revealed characteristics that were available for study only because the rapid collection of samples had minimized terrestrial contamination alteration this combination of factors rapid and accurate location of the event participation in the meteorite search by the public and coordinated scientific investigation of recovered samples is a model that was widely beneficial and should be emulated in future meteorite falls the tools necessary to recreate the sutter s mill recovery are available but are currently underutilized in much of the world weather radar networks scientific institutions with interest in meteoritics and the interested public are available globally therefore it is possible to repeat the sutter s mill recovery model for future meteorite falls around the world each for relatively little cost with a dedicated researcher doing so will significantly increase the number of fresh meteorite falls available for study provide meteorite material that can serve as the nuclei of new meteorite collections and will improve the public visibility of meteoritics research

kinematic evolution of thrusts wedge and erratic line length balancing insights from deformed sandbox models kinematic evolution of fold thrust structures has been investigated by analogue models that include syntectonic sedimentation different decollement dips and basement thicknesses produced different wedge geometries and propagating characteristics a model with one decollement level was characterized by a closely spaced thrust system during early stages of shortening as compared to the late stages the frequency of fault nucleation was rapid during the early stages of deformation conversely the frequency of fault nucleation was low and thrust spacing was significantly wider in a model with two decollement levels individual faults became locked at steep dips and deformation stepped forward as a new fault nucleated in sequence in front of the older locked structure once the thrust system was established up to 27 overall shortening an overlying bed was introduced to simulate syntectonic deformation model sand wedge did not grow self similarly but rather its length and height increased episodically with deformation restoration of deformed models show that layer parallel shortening accommodated for approximately half of the total model shortening across the multilayers calculated error in apparent layer shortening from the restored layers revealed a direct relation with depth of the layers in the models the experimental results are comparable to a natural example from the northern apennines fold and thrust belts

dike propagation and magma flow in a glassy rhyolite dike a structural and kinematic analysis exhumed magma conduits provide important evidence of the development and evolution of subvolcanic plumbing systems we use a 5 14 m thick flow banded rhyolite dike in arran scotland to present the first reconstruction of the directions and styles of initial propagation and subsequent magma flow based on mesoscale kinematic indicators the dike has concave inward dike margin segments with plumose like structures that record vertical and horizontal propagation of lobes which inflated and linked to form a through going sheet devitrified rhyolite zones at the dike margins show gentle to open folds in contrast glassy central parts of the dike are flow laminated and preserve folded and refolded isoclinal curvilinear folds and sheath folds that record sustained progressive deformation the inner interface between the glassy and devitrified facies is abrupt and marked by elongation lineations and mullions in the dike center fold axes plunge 27 ne along the dike and parallel to elongation lineations combined with shear sense indicators and objects sheared vesicles and asymmetric folds these features indicate that magma flow was obliquely upward to the southwest and locally 60 to the propagation direction of the dike the distribution of structures within the rhyolite indicates local accretion of the now devitrified material to the margins with localization of flow into the center of the dike we find that the initial magma flow direction was controlled by fracture propagation and interaction with the subsequent flow record controlled by accretion and flow localization in the conduit this study demonstrates that analysis of mesoscopic structural and kinematic features several of which have not previously been reported from dikes is a powerful tool that can be used to reconstruct the complex evolution of conduit initiation and magma flow processes

asteroid 6 hebe the probable parent body of the h type ordinary chondrites and the iie iron meteorites the s iv type asteroid 6 hebe is identified as the probable parent body of the h type ordinary chondrites and of the iie iron meteorites the ordinary chondrites are the most common type of meteorites falling to earth but prior to the present study no large mainbelt source bodies have been confirmed hebe is located adjacent to both the v6 and 3 1 resonances and has been previously suggested as a major potential source of the terrestrial meteorite flux hebe exhibits subtle rotational spectral variations indicating the presence of some compositional variations across its surface the silicate portion of the surface assemblage of hebe is consistent both in overall average and in its range of variation with the silicate components in the suite of h type chondrites the high albedo of hebe rules out a lunar style space weathering process to produce the weakened absorption features and reddish spectral slope in the s type spectrum of hebe linear unmixing models show that a typical ni fe metal spectrum is consistent with the component that modifies an h chondrite spectrum to produce the s type spectrum of hebe on the basis of the association between the h chondrites and the he iron meteorites our model suggests that large impacts onto the relatively metal rich h chondrite target produced melt bodies sheets or pods that differentiated to form thin laterally extensive near surface layers of ni fe metal fragments of the upper silicate portions of these melt bodies are apparently represented by some of the igneous inclusions in h chondrite breccias alternately masses of metal could have been deposited on the surface of hebe by the impact of a core or core fragment from a differentiated parent body of h chondrite composition subsequent impacts preferentially eroded and depleted the overlying silicate and regolith components exposing and maintaining large masses of metal at the optical surface of hebe in this interpretation the nonmagmatic iie iron meteorites are samples of the ni fe metal masses on the surface of hebe whereas the h chondrites are samples from between and or beneath the metal masses