the closing of tethys and the tectonics of the himalaya recent geological and geophysical data from southern tibet allow refinement of models for the closing of southern neo tethys and formation of the himalaya shelf sediments of the indian passive continental margin which pass northward into deep sea tethyan sediments of the indus tsangpo suture zone were deposited in the late cretaceous an andean type margin with a 2 500 km long trans himalayan kohistan ladakh gangdese granitoid batholith formed parallel to the southern margin of the lhasa block together with extensive andesites rhyolites and ignimbrites lingzizong formation the southern part of the lhasa block was uplifted deformed and eroded between the cenomanian and the eocene in the western himalaya the kohistan island arc became accreted to the northern plate at this time the northern part of the lhasa block was affected by jurassic metamorphism and plutonism associated with the mid jurassic closure of the bangong nujiang suture zone to the north the timing of collision between the two continental plates ca 50 40 ma marking the closing of tethys is shown by 1 the change from marine flysch like to continental molasse like sedimentation in the indus tsangpo suture zone 2 the end of gangdese i type granitoid injection 3 eocene s type anatectic granites and migmatites in the lhasa block and 4 the start of compressional tectonics in the tibetan tethys and indus tsangpo suture zone south facing folds south directed thrusts after the eocene closure of tethys deformation spread southward across the tibetan tethys zone to the high himalaya deep crustal thrusting barrovian metamorphism migmatization and generation of oligocene miocene leucogranites were accompanied by south verging recumbent nappes inverting metamorphic isograds and by south directed intracontinental shear zones associated with the main central thrust continued convergence in the late tertiary resulted in large scale north directed backthrusting along the indus tsangpo suture zone more than 500 km shortening is recorded in the foreland thrust zones of the indian plate south of the suture and 150 km shortening is recorded across the indian shelf zanskar range and the indus suture in ladakh there was also large scale shortening of the karakoram and tibetan microplates north of the suture as much as 1 000 km shortening occurred in tibet the more recent deformation however involved the spreading of this thickened crust and the lateral motion of the tibetan block along major approximately east west trending strike slip fault zones

duplex style and triangle zone formation insights from physical modeling duplexes are a common feature in thrust belts at many scales their geometries vary significantly from antiformal stacks with significant forethrusting in the cover e g southern pyrennes spain to triangle zones e g foreland canadian rockies to low displacement individually spaced ramp anticlines e g sub andean thrust belt bolivia we present a series of physical experiments demonstrating that the strength of the decollements relative to that of the intervening and overlying rock layers plays a significant role in controlling the duplex style the models comprise brittle layers made of dry quartz sand and decollements made of two types of viscous silicone polymers the strength of the decollements in the models is a function of the shortening rate applied to the model the relative strength of the decollements and surrounding rocks affects the development of active or passive roof duplexes triangle zones it also affects the amount of translation of individual thrust blocks and the spacing of thrust ramps which in turn determine if a duplex evolves into an antiformal stack or into individually spaced ramp anticlines model results indicate that specific associations of structural features form systematically under similar rheological and boundary conditions the presence of relatively strong decollements promotes local underthrusting of the cover individual ramp anticlines internal deformation of thrust sheets low early layer parallel shortening and sequential towards the foreland propagation of structures weak decollements promote forethrusting of the cover antiformal stacks coeval growth of structures and low internal strain with the exception of significant early layer parallel shortening no underthrusting at a regional scale occurred in any model

structure and evolution of the northern potwar deformed zone pakistan the northern potwar deformed zone npdz is part of the active foreland fold and thrust belt of the salt range and potwar plateau in northern pakistan about 500 km of seismic reflection profiles are integrated with surface geologic and drilling data to examine the deformation style and structure of the npdz with particular emphasis on history of deformation of the dhurnal oil field the seismic lines suggest that the overall structure of the eastern npdz is a duplex structure developed beneath a passive roof thrust the roof thrust is generated from a tipline in the miocene murree formation and the sole thrust is initiated from the same eocambrian evaporite zone that extends 80 km southward beneath the soan syncline and salt range the dhurnal oil field structure is a pop up at the southern margin of the npdz and developed beneath the passive roof thrust the passive roof thrust crops out just north of dhurnal on the steep northern limb of the soan syncline an overstep passive roof thrust sakhwal fault is interpreted west of dhurnal this fault developed due to

a whiff of oxygen before the great oxidation event high resolution chemostratigraphy reveals an episode of enrichment of the redox sensitive transition metals molybdenum and rhenium in the late archean mount mcrae shale in western australia correlations with organic carbon indicate that these metals were derived from contemporaneous seawater rhenium osmium geochronology demonstrates that the enrichment is a primary sedimentary feature dating to 2501 8 million years ago ma molybdenum and rhenium were probably supplied to archean oceans by oxidative weathering of crustal sulfide minerals these findings point to the presence of small amounts of o 2 in the environment more than 50 million years before the start of the great oxidation event

geochemical and anthropogenic enrichments of mo in sediments from perennially oxic and seasonally anoxic lakes in eastern canada abstract we measured the vertical distributions of mo fe mn sulfide sulfate organic carbon major ions and ph in sediment porewater from one perennially oxic and three seasonally anoxic lacustrine basins in eastern canada as well as those of mo acid volatile sulfide fe mn al organic c 210pb and 137cs in sediment cores from the same sites the only input of anthropogenic mo to these lakes comes from atmospheric deposition the relatively monotonous distribution of mo in the porewater of three seasonally anoxic basins suggests that mo is not redistributed in the sedimentary column during periods of anoxia in contrast porewater mo profiles obtained at three sampling dates in a perennially oxic basin display sharp mo peaks below the sediment water interface indicating redistribution subsequent to deposition modeling of these latter porewater mo profiles with a diagenetic reaction transport equation coupled to comparisons among the various porewater and solid phase profiles reveal that mo is released at 1 2 cm depth as a consequence of the reductive dissolution of fe oxyhydroxides and scavenged both at the vicinity of the sediment water interface by re adsorption onto authigenic fe oxyhydroxides and deeper in the sediments where dissolved sulfide concentrations are higher the estimated rate constant for the adsorption of mo onto fe oxyhydroxides is 36 45 cm3 mol 1 s 1 diagenetic modeling indicates that authigenic mo in sediments of the perennially oxic basin represents about one third of the total solid phase mo in the first cm below the sediment water interface and only one tenth below this horizon if we assume that no authigenic mo is accumulated in the seasonally anoxic lake sediments we conclude that the sediment mo concentrations which are up to 3 16 times higher than the average lithogenic composition depending on the lake are mainly due to atmospheric deposition of anthropogenic mo and not to the formation of authigenic mo phases reconstructed historical records of the atmospheric mo deposition indicate maximum values in the 1970s and 1980s and significant decreases since then emissions to the atmosphere associated with the smelting of non ferrous ores and coal combustion appear to be the most important sources of anthropogenic mo

timing of structural events in the himalayan foothills of northwestern pakistan the attock cherat range forms the southern boundary of the peshawar basin and includes rocks transitional between metasediments of the lesser himalaya and foreland basin strata to the south the attock cherat range comprises three fault bounded structural blocks which are from north to south 1 precambrian metaclastic strata overlain by unfossiliferous limestone which is itself apparently overlain by paleozoic strata with the contact not exposed 2 unfossiliferous flysch of precambrian age overlain by cretaceous and paleogene marine strata and murree red beds at least in part of early miocene age and 3 unfossiliferous limestone argillite and quartzite correlated in part to paleozoic strata in the peshawar basin overlain by a tertiary sequence generally similar to that in block 2 farther south in the kala chitta range strata of triassic to eocene age occur in south verging folds and thin thrust sheets the similarity of the tertiary sequences in the kala chitta range and in blocks 2 and 3 demonstrates that the pre tertiary sequences were juxtaposed by faults prior to deposition of the paleocene lockhart limestone this may coincide with initial contact of the west northwest facing passive margin of india with eurasia or nearby microplates major late tertiary imbricate thrusting and folding took place prior to uplift of the attock cherat range and to deposition of peshawar intermontane basin fill of pliocene pleistocene age the peshawar basin formed as the kala chitta range was faulted south on the main boundary thrust mbt forcing siwalik foreland basins still farther south late quaternary deformation in the southern peshawar basin occurred along a seismically active zone of en echelon stepped left faulted pressure ridges that may reflect a subsurface ramp on the older mbt

middle late miocene 10 ma formation of the main boundary thrust in the western himalaya three independent data sets from northwestern india and pakistan suggest initial displacement along 1000 km of the main boundary thrust prior to 10 ma at least 5 m y earlier than previously reported regionally extensive changes in the depositional characteristics and rates of the foreland basinfill between 11 and 9 5 ma are interpreted to reflect new hinterland loading due to the formation of the main boundary thrust sediment accumulation rates sandstone siltstone ratios and thickness and amalgamation of individual sandstone bodies all substantially increase after 11 ma in well dated stratigraphic sections from pakistan to nepal across the indo gangetic foreland basin in the himachal pradesh reentrant of northwestern india a newly discovered 8 7 ma conglomerate derived from the hanging wall of the main boundary thrust indicates that source area uplift and denudation must have occurred prior to 9 ma and probably prior to 10 ma assuming a gravelprogradationrateof3cm yr threeapatitefission trackages fromstructuresattheleadingedgeofthemainboundarythrustin the kohat region of northwest pakistan indicate that rapid cooling below 105 c1 2 m y earlier these data indicate that the main boundary thrust in the western himalaya formed synchronously along strike in the middle late miocene has a displacement rate of 10 mm yr and has a displacement history that is coeval with late displacement on the main central thrust

structural variation within the himalayan fold and thrust belt a case study from the kohat potwar fold thrust belt of pakistan abstract the kohat and potwar fold thrust belts kp ftb in pakistan exhibit structural variations over 250 km along strike within the himalayan fold and thrust system our 3d deformation model shows that kohat surface structures evolved above an active roof thrust in eocene evaporites the ramp forming duplexes in the kohat were stacked and passively transported toward the foreland above new ramps resulting in up to 5 km of thickening between the two decollements ramps from the kohat extend into the potwar as thrust tips of fault propagation folds the basement slope changes from flat 1 below the southern part corresponding to the change in structural style and complexity of the kp ftb the kalabagh fault zone linking the two belts is interpreted as a zone of complex dextral strike slip rotational faulting salt expulsed from the hanging walls of normal faults and under synclines in the kalabagh fault zone moved toward the footwall of normal faults accumulated in the cores of anticlines and formed lobe structures at the deformation front the fundamental reasons for the variable structural styles are changes in decollement strength basement slope preexisting normal faulting presence of a secondary decollement and spatially variable salt mobility and accumulation

mechanics of fold and thrust belts and accretionary wedges cohesive coulomb theory a critically tapered fold and thrust belt or submarine accretionary wedge is one that is on the verge of coulomb failure everywhere including its base where frictional sliding along a decollement is assumed to be occurring cohesion within a wedge can add significantly to the overall strength near the toe the effect of this is to decrease the near toe taper leading to a critical topographic profile that is concave upward if the decollement is planar we obtain an approximate self consistent solution for the state of stress within a thin skinned cohesive critical coulomb wedge and determine the relationship between the wedge taper and its strength and basal friction the theory is then applied to the presently deforming fold and thrust belt of western taiwan fitting of theoretical critical wedge shapes to topographic profiles and measurements of the step up angles of thrust faults from the basal decollement are used to constrain the taiwan wedge strength parameters an attractive assertion fully consistent with all the observations is that the mechanics of fold and thrust belts and accretionary wedges is governed by normal frictional and fracture strengths of rocks measured in the laboratory in particular if byerlee s law b 0 85 is adopted as the coefficient of sliding friction on the base we find a coefficient of internal friction 0 9 1 0 in the wedge and a wedge cohesion so 5 20 mpa other solutions having strengths and ambient stresses up to 4 times lower than this can also however satisfy the data

development of the himalayan frontal thrust zone salt range pakistan the salt range is the active frontal thrust zone of the himalaya in pakistan seismic reflection data show that a 1 km offset of the basement acted as a buttress that caused the central salt range potwar plateau thrust sheet to ramp to the surface exposing mesozoic and paleozoic strata the frontal part of the thrust sheet was folded passively as it overrode the subthrust surface on a ductile layer of eocambrian salt lack of internal deformation of the rear part of the thrust sheet is due to decoupling of sediments from the basement along this salt layer early to middle pliocene 4 5 ma conglomerate deposition in the southern potwar plateau previously interpreted in terms of compressional deformation may instead document uplift related to basement normal faulting stratigraphic evidence paleomagnetic dating of unconformities and sediment accumulation rates suggest that the thrust sheet began to override the basement offset from 2 1 to 1 6 ma cross section balancing demonstrates at least 20 to 23 km of shortening across the ramp the rate of himalayan convergence that can be attributed to underthrusting of indian basement beneath sediments in the pakistan foreland is therefore at least 9 14 mm yr about 20 35 of the total plate convergence rate

lateral structural variation along the kalabagh fault zone nw himalayan foreland fold and thrust belt pakistan abstract the nw himalayan fold and thrust belt in pakistan is of gentler regional slope and wider extent than the other parts of the convergent plate boundary between india and the rest of asia large scale structural re entrants typify the main frontal thrust mft of the nw himalayan fold and thrust belt in pakistan understanding dynamics of the formation of these structural variations has been hampered by the lack of information about the lateral structures bounding the re entrants our mapping of the kalabagh fault zone a lateral ramp linking the salt and the surghar ranges advanced spaceborne thermal emission and reflection radiometer aster data field investigations and the interpreted reprocessed 2d seismic data this integration of surface and subsurface geology provides new insights on the geometry and evolution of the kalabagh fault zone by showing that it forms an oblique ramp to the main frontal thrust and at north a lateral ramp with right lateral strike slip movement our results indicate that the presence and areal extent of the evaporates is the dominant factor controlling lateral structural variation in the nw himalayan fold and thrust belt of pakistan the kalabagh fault zone acts as a zone that accommodates differential shortening and structural variation along the orogenic trend

a karst connection model for grand canyon arizona usa abstract a new model for the connection of the eastern and western grand canyon is proposed that involves westward flow of redwall karst aquifer water under the kaibab arch along the steepest hydraulic gradient to discharge at a structural low in a headward eroding protowestern grand canyon a karst aquifer hydrological connection was first established between the eastern and western grand canyon then collapse incision and headward erosion of the canyon followed this subterranean route this proposed model is based on what is happening today on the northern marble platform where the redwall muav aquifer is still intact the three sinkhole caves ah hol sah indian pit and black abyss provide vertical flow routes down to the redwall karst aquifer joining water discharging from the kaiparowits hydrologic basin to the colorado river along the fence springs system projecting this process back in time and spatially southward we propose that at around 6 ma a sinkhole or sinkholes existed at the confluence of the colorado river with the little colorado river little colorado river water then flowing northward to an interior lake basin glen lake in southern utah became pirated down this sinkhole s thus causing a reversal of drainage barbed tributaries in marble canyon headward erosion then proceeded up marble and little colorado canyons from the collapsing sinkhole with marble canyon incision breaching glen lake at around 5 5 ma this effected the final connection and total integration of the colorado river from colorado to the gulf of california

age and evolution of the grand canyon revealed by u pb dating of water table type speleothems the age and evolution of the grand canyon have been subjects of great interest and debate since its discovery we found that cave mammillaries water table indicator speleothems from nine sites in the grand canyon showed uranium lead dating evidence for an old western grand canyon on the assumption that groundwater table decline rates are equivalent to incision rates samples in the western grand canyon yielded apparent water table decline rates of 55 to 123 meters per million years over the past 17 million years in contrast to eastern grand canyon samples that yielded much faster rates 166 to 411 meters per million years chronology and inferred incision data indicate that the grand canyon evolved via headward erosion from west to east together with late stage 3 7 million years ago accelerated incision in the eastern block

deformation patterns and structural vergence in brittle ductile thrust wedges an additional analogue modelling perspective abstract scaled physical models of brittle ductile thrust wedges investigated the causes leading to the development of the various structural styles observed in fold and thrust belts and accretionary prisms this study focused on some potential controlling factors such as 1 relative strength between the brittle overburden and the viscous decollement layer brittle ductile coupling 2 the effect of very low basal friction and 3 pre shortening rheological stratigraphy including decollement strength type 1 models had a single basal decollement whereas in type 2 models the decollement was embedded in brittle material simulating an upper roof sequence and a lower floor sequence other models investigated the effects produced by an horizon of mechanical weakness at the base of the viscous decollement type 1a and the role of decollement offset type 3 the experiments suggest the occurrence of a genetic relationship between the absolute values of shear stresses and the development of dominating hinterland or foreland verging thrust faults or dually verging thrusts by controlling the orientation of the 1 axis basal friction and decollement offset is found to effectively influence the deformation pattern and structural vergence and could explain the development of dominating backthrusts in cascadian type margins the decoupling of a frontal monocline via the upper decollement type 2 models produced passive roof duplex structures termed composite roof duplex when the frontal monocline coexists with outward fold propagation

evolution of the lithosphere in pakistan abstract the geological setting of pakistan in the framework of the modern concept of plate tectonics is unique in the sense that within an area of about 800 000 km 2 critical tectonic junctions of different interacting plates and microplates are present in an environment where field exposures are excellent here we discuss the dynamics of these various plate boundaries two types of active plate boundaries are conspicuous 1 convergent boundaries characterized by continent continent collision obduction and thrusting in the northern region of the himalaya and by oceanic crust subduction with a volcanic arc and a wide accretionary wedge in the southern region of chagai and makran 2 a transform boundary the chaman transform zone characterized by very large strike slip and lesser thrusting the chaman transform zone connects the makran convergence zone where oceanic lithosphere is being subducted beneath the lut and afghan microplates with the himalayan convergence zone where the indo pakistan lithosphere is underthrusting eurasia the chaman zone is at present an intracontinental plate boundary with oblique motion characterized by north south strike slip faults and eastward thrusting and folding in the kirthar sulaiman mountain belt this mountain belt the northwestern margin of the indo pak subcontinent was an atlantic type margin from the late paleozoic until the cretaceous in the cretaceous the continental margin became a plate boundary a thrust belt was formed in the paleocene and fragments of the oceanic crust were obducted either as thrust sheets muslimbagh or as an ophiolitic melange bela and waziristan

displacement transfer from fault bend to fault propagation fold geometry an example from the himalayan thrust front abstract the leading edge of the ene trending himalayan thrust front in pakistan exhibits along strike changes in deformational style ranging from fault bend to fault propagation folds although the structural geometry is very gently deformed throughout the salt range it becomes progressively more complex to the east as the leading edge of the emergent salt range thrust becomes blind surface geology seismic reflection petroleum well and chronostratigraphic data are synthesized to produce a 3 d kinematic model that reconciles the contrasting structural geometries along this part of the himalayan thrust front we propose a model whereby displacement was transferred across a newly identified lateral ramp from a fault bend fold in the west to fault propagation folds in the east and comparable shortening was synchronously accommodated by two fundamentally different mechanisms translation vs telescoping however substantially different shortening distribution patterns within these structurally contrasting segments require a tear fault which later is reactivated as a thrust fault the present geometry of this s shaped displacement transfer zone is a combined result of the nw se compression of the lateral culmination wall and associated tear fault and their subsequent modification due to mobilization of underlying ductile salt

wrench faulting in the northern pakistan foreland the acquisition processing and interpretation of reflection seismic gravity and magnetic data in conjunction with detailed geological mapping throughout the kohat plateau have resulted in a reinterpretation of the structural style of this portion of the northern pakistan foreland our interpretation of the recently acquired geologic and geophysical data as well as a critical reevaluation of previously acquired data and regional geology indicates that the kohat plateau has undergone major episodes of strike slip faulting basement involved reverse faulting and minor thrust faulting consistent with transpressional tectonics our interpretation contrasts with previous models that invoked only southward directed thrust faulting the principal key to the reinterpretation of seismic data was depth migration before stack mbs seismic processing which was performed on five seismic lines to resolve the structural geology mbs processed seismic data show complex deformation and steep dips more accurately than other methods and allowed us to identify the high amplitude structures in the kohat plateau surface geological mapping in the kohat plateau and adjacent areas indicates tight anticlines consistent steep dips horizontal motion fabrics and a conspicuous lack of low angle thrust faults aeromagnetic and gravity data indicate that precambrian basement is involved in the deformation modern seismicity indicates that faults mapped at the surface and subsurface are dominated by strike slip displacement the kohat plateau is located near the intersection of the transcurrent chaman fault system a 1000 km long system of north south striking sinistral strike slip faults and east west striking contractual structures that form the grain of the himalayan mountain chain in this area of northwest pakistan surface and subsurface structures fit the expected regional patterns that result from transpressional deformation in this complex zone of intersection our reinterpretation has applicability to other deformed belts worldwide that exhibit analogous characteristics and criteria of transpressional tectonics but are interpreted as being dominated by low angle thrust tectonics

field techniques for measuring bedrock erosion and denudation bedrock erosion rates in natural landscapes are usually slow of the order of millimeters per year or less and sophisticated techniques have been developed to measure them different techniques have proved to be valuable depending on the spatial and temporal scale on which information is needed on the environment and on the scientific question that is asked here we give an overview of the various methods that have been developed we introduce their working principles and outline their advantages and disadvantages further we provide comprehensive references to relevant literature both on the methods and on scientific examples of their application 2016 the authors earth surface processes and landforms published by john wiley sons ltd

increase of seawater mo inventory and ocean oxygenation during the early cambrian abstract the early cambrian radiation of macroscopic animals commonly referred as the cambrian explosion is one of the most important biological innovations in earth history because oxygen is a requirement for complex animal life it is generally accepted that ocean oxygenation may have been the environmental trigger for animal evolution but direct geochemical evidence supporting oxygen increase prior to the cambrian explosion remains sparse and insufficient to better understand the casual relationship between ocean oxygenation and animal evolution we have carried out a systematic analysis of redox sensitive trace element rste concentrations total organic carbon toc contents and pyrite morphology for the early cambrian niutitang formation of the hejiapu section northeastern guizhou province south china the new data in combination with previously published data from other sections show strong mo enrichments average of 88 ppm and high mo toc ratios average of 14 ppm wt in the euxinic black shales of the lower niutitang formation 520 ma indicating increase of the oceanic mo reservoir in the light of the positive correlation between sediment mo toc and aqueous mo in modern basins the early cambrian oceanic mo concentration is estimated as 50 nmol which is about half of the modern ocean mo concentration 105 nmol but is significantly higher than that of the mesoproterozoic oceans 10 20 nmol the marked increase in oceanic mo reservoir is therefore interpreted as recording significant rise of atmospheric oxygen and pervasive ocean oxygenation which may have facilitated the diversification of macroscopic metazoans during the early cambrian

hinterland vergent tectonic wedge below the riwat thrust himalayan foreland pakistan implications for hydrocarbon exploration the riwat thrust with a surface trace of over 50 km is one of the major faults in the footwall of the main boundary thrust in the himalayan foreland of pakistan surface geology shows that the riwat thrust is a foreland vergent thrust along which lower to middle siwalik molasse strata are thrust southward over upper siwalik strata seismic reflection interpretation shows that the riwat thrust developed as a roof thrust of a hinterland vergent tectonic wedge triangle zone underlain by evaporites the riwat thrust propagates upsection from a depth of about 4 km at the base of the siwalik group at this depth it merges into a hinterland vergent blind thrust that propagates upsection as a ramp from eocambrian evaporites covering the basement at a depth of about 6 km bounded between this set of conjugate faults a tectonic wedge of eocambrian evaporites to neogene strata is thrust toward the hinterland to form a triangle zone the roof thrusts of triangle zones have been widely mapped as backthrusts in deformed mountain fronts hinterland motion of tectonic wedges as in the riwat thrust triangle zone may be a feature of the fold and thrust belts underlain by evaporites acting as an extremely weak decollement layer their recognition with a trap forming geometry below a thrust is important for interpreting particular fold belts and for hydrocarbon exploration these structures could be predicted by the surface geology data where hinterland vergence of a fold below a thrust is apparent however seismic reflection data appear to be critical in recognizing these structures

the india asia collision in north pakistan insight from the u pb detrital zircon provenance of cenozoic foreland basin the northernmost exposures of sub himalayan cenozoic strata in the hazara kashmir syntaxial region of north pakistan comprises the paleocene eocene marine strata in the lower part and oligocene miocene nonmarine strata in the upper part this study provides the detrital zircon u pb geochronology of the cenozoic strata in this area the strong resemblance of u pb age spectra of paleocene hangu lockhart and patala formations with those of himalayan strata indicate an indian plate provenance the first appearance of 100 ma detrital zircon u pb ages within the lower most part of the early eocene margalla hill limestone indicates a shift from an indian to asian provenance geologic mapping shows the existence of a disconformity between the lower and upper most part of the patala formation which is interpreted to have been formed by the migration of a flexural forebulge through this region we consider the upper most part of the patala formation to have been deposited within the distal foredeep of the foreland basin the indian to asian provenance shift and the presence of a possible foreland basin forebulge provide strong evidence that india asia collision was underway in northern pakistan at ca 56 55 ma

unroofing incision and uplift history of the southwestern colorado plateau from apatite u th he thermochronometry the source of buoyancy for the uplift of cratonic plateaus is a fundamental question in continental dynamics the 1 9 km uplift of the colorado plateau since the late cretaceous is a prime example of this problem we used apatite u th he thermochronometry 230 analyses 36 samples to provide the fi rst single system regional scale proxy for the unroofi ng history of the southwestern quadrant of the plateau the results confi rm overall southwest to northeast unroofi ng from plateau margin to plateau interior a single phase of unroofi ng along the plateau margin in late cretaceous to early tertiary sevierlaramide time contrasts with multiphase unroofi ng of the southwestern plateau interior in early and mid to late tertiary time the early cretaceous was characterized by northeastward tilting and regional erosion followed by aggradation of 1500 m of upper cretaceous sediments along the eroded plateau margin sevier laramide denudation affected the entire southwestern plateau was concentrated along the plateau margin and migrated from northwest to southeast following a period of relative stability of the landscape from ca 50 30 ma signifi cant unroofi ng of the southwestern plateau interior occurred between ca 28 and 16 ma additional denudation north of the grand canyon took place in latest tertiary time mid tertiary dates from the grand canyon basement at the bottom of the upper granite gorge limit signifi cant incision of the modern grand canyon below the kaibab surface to 1500 m difference in vertical structural position if these models are correct they indicate that a proto grand canyon of kilometer scale depth had incised post paleozoic strata by the early eocene evidence for kilometerscale mid tertiary relief in northeast fl owing drainages along the plateau margin as well as the mid tertiary episode of plateau interior unroofi ng imply that the southwestern plateau interior had attained substantial elevation by at least 25 20 ma if not much earlier these observations are inconsistent with any model calling for exclusively late tertiary uplift of the southwestern plateau sevier laramide plateau surface uplift and incision thus result from one or more processes that enhanced the buoyancy of the plateau lithosphere expanding the cordillera s orogenic highlands into its lowstanding cratonic foreland the onset of the laramide slab s demise at ca 40 ma and the major pulse of extension in the basin and range from ca 16 10 ma appear to have had little infl uence on the denudation history of the southwestern plateau in contrast the post laramide unroofi ng episodes may be explained by drainage adjustments induced by rift related lowering of regions adjacent to the plateau without the need to otherwise modify the plateau lithosphere our data do not preclude a large component of post early eocene elevation gain or the geodynamic mechanisms it may imply but they do point toward laramide age buoyancy sources as the initial cause of signifi cant surface uplift ending more than 500 m y of residence near sea level

the role of salt in fold and thrust belts davis d m and engelder t 1985 the role of salt in fold and thrust belts in n l carter and s uycda editors collision tectonics deformation of continental lithosphere tectonophysics 119 67 88 the style of deformation in thin skinned fold and thrust belts is critically dependent upon the resistance to sliding along the detachment between the mass of deforming sediments and the underlying rocks evaporites can provide an extremely weak horizon within which a basal detachment can form and along which only a relatively small shear traction can be supported fold and thrust belts that form atop a salt layer such as the appalachian plateau the franklin mountains in northwestern canada and the jura of the alps among others share several readily observable characteristics as predicted by a simple mechanical model for fold and thrust belts a detachment in salt permits a thrust belt to have an extremely narrow cross sectional taper in addition predicted orientations of the principal stress axes over a salt dtcollement are consistent with the commonly observed lack of a consistently dominant vergence direction of structures within the thrust belt other common attributes of salt basal thin skinned deformation include the presence of several widely but regularly spaced folds and abrupt changes in deformational style at the edge of the salt basin

the origin of decoupled carbonate and organic carbon isotope signatures in the early cambrian ca 542 520 ma yangtze platform abstract the early cambrian ca 542 520 ma strata in south china record two prominent negative carbonate carbon isotope 13ccarb excursions of early nemakit daldynian n d and early tommotian ages across each of these excursions carbonate and organic carbon isotopes 13ccarb and 13corg are strongly decoupled regional correlation across a shelf to basin transect shows lateral heterogeneity of 13corg during the early middle n d but more homogenized 13corg values across the basin during the late n d and tommotian the temporal and lateral variations in 13corg suggest that decoupled 13ccarb and 13corg across the n d 13ccarb excursion were possibly caused by diagenetic alteration of organic matter and or amplification of detrital organic carbon isotope signature in low toc carbonates in contrast decoupled 13ccarb and 13corg of the upper n d and tommotian were likely resulted from chemoautotrophic methanotrophic biomass contribution to toc in organic rich black shale and carbonates the decoupled 13ccarb 13corg pattern from the lower n d strata ca 542 ma shows striking similarities with those from the basal ca 635 ma and upper ca 551 ma doushantuo formation in all three cases decoupled 13ccarb 13corg are seen in organic poor carbonates toc 0 1 and coupled 13ccarb 13corg occur in organic rich black shale and carbonates at the end of the negative 13ccarb excursion these similarities suggest that the shift from decoupled to coupled 13ccarb 13corg has no causal link with the terminal oxidation of a large oceanic doc reservoir given the pervasive anoxia euxinia in ediacaran early cambrian oceans local doc rich environments may have been common but a large oceanic doc reservoir capable of buffering the 13c of marine organic matter requires independent evidence

extreme enrichment of polymetallic ni mo pge au in lower cambrian black shales of south china an os isotope and pge geochemical investigation extreme metal enrichments occur in the lower cambrian niutitang formation a thick black shale sequence deposited on the yangtze platform of south china and form a regionally distributed conformable polymetallic ni mo pge au sulfide horizon the origin for the extreme enrichment of metals in these black shales is discussed based on a comprehensive geochemical investigation of re os isotopes and platinum group elements the black shales of the lower cambrian niutitang formation in guizhou province yielded an re os isochron age of 535 11 ma with an initial 187 os 188 os ratio of 0 80 0 04 which is similar to the initial 187 os 188 os ratio 0 78 0 19 of the ni mo sulfide ores but slightly lower than the initial 187 os 188 os ratio 1 18 0 02 of lower cambrian black shales from the lesser himalaya india a comparison of os isotope data among the chinese ni mo sulfide ores the seafloor massive sulfide deposits and contemporaneous seawater suggests a possible similar hydrothermal forming mechanism for these deposits the pge concentrations pt anomaly pt pt pt pd ir pd au pd ratios of the chinese ni mo sulfide ores are similar to those metal rich black shales of submarine volcanogenic hydrothermal origin from czech republic namibia and canada but are different from those data of the ocean floor fe mn crusts that have scavenged their pge and other metals directly from seawater it is therefore suggested that the ni mo sulfide ores from the niutitang black shale sequence in south china had a submarine hydrothermal origin the anoxic environments and abundant organic matter in the ocean basin also played a key role for the extreme metal enrichments the discharge of hydrothermal fluids into the cambrian ocean may have had a great effect on life during the cambrian explosion 2007 elsevier b v all rights reserved

contrasting molybdenum cycling and isotopic properties in euxinic versus non euxinic sediments and sedimentary rocks refining the paleoproxies abstract the redox sensitive transition element molybdenum is present in the earth s crust at trace concentrations but is abundant in seawater marine sediments and ancient sedimentary rocks these occurrences have led to the development of a suite of paleoredox proxies based on the bulk concentration of mo its isotopic composition and the covariation of mo with total organic carbon toc in ancient black shales however these proxies have almost exclusively targeted the identification and interpretation of euxinic environments where bottom waters are both anoxic and sulfidic here we present a discussion of the mo geochemistry of non euxinic sediments where hydrogen sulfide is sometimes present yet always restricted to pore waters we propose a new paleoredox application that uses mo concentrations to help distinguish between environments where sulfide was present in the bottom waters and environments where sulfide was restricted to pore waters under ideal conditions it is also possible to infer the presence of mn oxides recycling in non euxinic paleoenvironments based on the mo isotope composition of ancient black shales providing a critical constraint on bottom water oxygenation

a proposed laramide proto grand canyon abstract the absence of rim gravels north of grand canyon and of canaan peak type gravels south of grand canyon suggests that a paleocanyon which intersected the transport of these gravels north and south may have begun forming in the laramide in approximately the same position as today s central grand canyon this laramide age canyon is envisioned as having flowed generally from the sw to ne from the peach springs canyon area to mile 197 where it was captured by karst then along a n 60 e joint system to the kanab point area where it converged with drainage coming off the west side of the kaibab arch from there it flowed north along the west flank of the kaibab arch to paleogene lake claron the critical idea suggested by this proposed model is that the modern colorado river utilized laramide paleotopography in establishing its course through the central grand canyon with younger sections of the canyon integrating with it later in the middle to late miocene this paleocanyon route in association with headward erosion from the grand wash cliffs toward the kaibab arch after 16 17 ma helps account for the total volume of rock eroded from grand canyon which cannot be explained by present day incision rates

experimental insights on the geometry and kinematics of fold and thrust belts above weak viscous evaporitic decollement abstract this paper discusses the differences in mechanical properties and kinematics between fold and thrust belts detaching on evaporitic decollements and those detaching on stronger detachments physical experiments are described that model shortening of a thick brittle cover overlying a weak viscous decollement to gain a better understanding of these differences we tested the influence of 1 the decollement layer thickness and 2 the presence of a deformable backstop on the hinterland side and of a decollement pinch out on the foreland side because of the very low shear strength of the viscous decollement folds and thrusts did not propagate according to a piggy back sequence but by centripetal back and forth propagation additional shortening was accommodated by growth of all existing structures fold symmetry and thrust vergence varied between experiments models confined between two rigid vertical endwalls always deformed by symmetric folding and thrusting in models having a deformable backstop and a foreland decollement pinch out forethrusting initially dominated folds were asymmetric and fault blocks rotated in models having a thick decollement layer folds kept growing asymmetrically diapirism also depended on the initial decollement geometry diapirs formed only in models having a deformable backstop and were restricted to the hanging wall of a fault related fold finally the implications of such kinematics on the thermal history are discussed as well as the likelihood of hydrocarbon maturation and preservation

mo total organic carbon covariation in modern anoxic marine environments implications for analysis of paleoredox and paleohydrographic conditions 1 sedimentary molybdenum mo s has been widely used as a proxy for benthic redox potential owing to its generally strong enrichment in organic rich marine facies deposited under oxygen depleted conditions a detailed analysis of mo s total organic carbon toc covariation in modern anoxic marine environments and its relationship to ambient water chemistry suggests that 1 mo s while useful in distinguishing oxic from anoxic facies is not related in a simple manner to dissolved sulfide concentrations within euxinic environments and 2 patterns of mo s toc covariation can provide information about paleohydrographic conditions especially the degree of restriction of the subchemoclinal water mass and temporal changes thereof related to deepwater renewal these inferences are based on data from four anoxic silled basins the black sea framvaren fjord cariaco basin and saanich inlet and one upwelling zone the namibian shelf representing a spectrum of aqueous chemical conditions related to water mass restriction in the silled basin environments increasing restriction is correlated with a systematic decrease in mo s toc ratios from 45 5 for saanich inlet to 4 5 1 for the black sea this variation reflects control of mo s by mo aq which becomes depleted in stagnant basins through removal to the sediment without adequate resupply by deepwater renewal the basin reservoir effect the temporal dynamics of this process are revealed by high resolution chemostratigraphic data from framvaren fjord and cariaco basin sediment cores which exhibit long term trends toward lower mo s toc ratios following development of water column stratification and deepwater anoxia mo burial fluxes peak in weakly sulfidic environments such as saanich inlet owing to a combination of greater mo aq availability and enhanced mo transport to the sediment water interface via fe mn redox cycling and are lower in strongly sulfidic environments such as the black sea and framvaren fjord these observations demonstrate that at timescales associated with deepwater renewal in anoxic silled basins decreased sedimentary mo concentrations and burial fluxes are associated with lower benthic redox potentials i e more sulfidic conditions these conclusions apply only to anoxic marine environments exhibiting some degree of water mass restriction e g silled basins and are not valid for low oxygen facies in open marine settings such as continent margin upwelling systems

origin and paleogeography of an immense nonmarine miocene salt deposit in the basin and range western usa this is the publisher s version which is also available electronically from http www jstor org stable 30079883

structural interpretation of seismic reflection data from eastern salt range and potwar plateau pakistan approximately 1 6000 km of seismic reflection profiles from the eastern salt range and potwar plateau sr pp of pakistan is integrated with available magnetostratigraphic surface geologic and well data to classify structural styles determine the timing of deformation and estimate the amount of telescoping of the sedimentary cover the eastern sr pp are similar to other fold and thrust belts underlain by evaporites in that 1 it is part of a zone of overthrusting that extends considerably farther over the himalayan foreland than adjacent areas not underlain by evaporites 2 the overall thrust wedge has a narrow cross sectional taper 3 structures verge toward the hinterland as well as toward the foreland and 4 fold trends are long and continuous consisting of tight salt cored anticlines separated by broad synclines disharmonic folding of the sedimentary section relative to the underlying basement is due to effective decoupling along the intervening salt layer subsurface mapping atop a strongly reflective sequence of cambrian to eocene strata reveals that many surface folds are cored by both foreland and hinterland dipping blind thrusts and some are fault propagation folds in some cases intersecting thrusts result in local triangle zones other surface folds have a pop up geometry the dip of the basement toward the inner part of the fold and thrust belt is more gentle in the eastern sr pp 1 1 5 than the central sr pp 2 3 mechanical considerations demonstrate that unlike the relatively undeformed central sr pp a broad deformational zone has developed in the eastern sr pp to provide a surface topographic slope necessary to maintain a critical taper of the thrust wedge cross section balancing indicates that approximately 24 km of shortening has occurred across the foreland in the eastern sr pp since 5 5 ma approximately 18 km in the last 2 5 m y the shortening rate of 7 mm year for the latter time interval is roughly 15 of the 40 to 50 mm year convergence rate between the indian and eurasian plates

late quaternary deformation of the salt range of pakistan in the salt range siwalik strata as young as 400 000 yr b p are strongly deformed and overlain with angular unconformity by fanglomerates that are themselves folded and thrust faulted the south flank of the salt range appears in map view as a series of scallops convex to the south produced by a thrust fault bringing the salt range south southeast over sediments of the jhelum river plain the western edge of the range is marked by right slip faults that cut the kalabagh conglomerate which itself rests upon siwaliks with angular unconformity the kalabagh conglomerate is folded and probably cut by diapirs from the salt range formation holocene alluvium appears to be undeformed and strike slip fault lineations are more subdued than those along the historically active chaman fault suggesting that the recurrence interval of faulting may be measured in thousands of years the low historic seismicity of the salt range may be due to such weak coupling between the salt range decollement and crystalline basement that fault displacement is not accompanied by great earthquakes in contrast to the indian foredeep of the himalaya

changes in marine productivity and redox conditions during the late ordovician hirnantian glaciation abstract changes in marine productivity and redox conditions during the end ordovician hirnantian glaciation and ordovician silurian transition were investigated through mo isotope and major and trace element analyses of the wangjiawan hubei province and nanbazi guizhou province sections from the yangtze platform of south china katian shales of the wufeng formation which yield the graptolites dicellograptus complanatus dicellograptus complexus and paraorthograptus pacificus were deposited under euxinic conditions at both localities as shown by high mo ef u ef and 98 mo values a major sea level regression during the hirnantian glaciation resulted in shallowing and a shift toward better oxygenated conditions within the yangtze sea as well as deposition of thin bedded siliceous sediments calcirudite debris flows and limestone turbidites of the kuanyinchiao formation the base of which correlates with the first phase of the end ordovician mass extinction the termination of the hirnantian glaciation at the top of the kuanyinchiao formation was associated with a major sea level transgression a rapid expansion of euxinia in the yangtze sea as documented by a return of high mo ef u ef and 98 mo values and the second phase of the mass extinction during which the cool adapted hirnantian fauna went extinct the long term cooling trend of the middle and late ordovician which culminated in the hirnantian glaciation was driven by enhanced burial of organic carbon as documented by 13 c carb 13 c org and 34 s py records increased organic carbon burial was linked to high rates of marine productivity as shown by high toc and biogenic ba concentrations especially at the deeper less restricted wangjiawan locale producing the hice hirnantian isotopic curve excursion 13 c carb excursion the locus of organic carbon burial during the hirnantian crisis shifted to deeper water environments that were located outside the study region the relatively rapid onset and termination of the hirnantian glaciation were probably due to crossing of tipping points in the late ordovician climatic oceanic system

paleomagnetism of the middle siwalik formations of northern pakistan and rotation of the salt range decollement abstract sampling for paleomagnetic study has been carried out at seven localities in the potwar plateau region of pakistan in the vicinity of the salt range in all 253 sites consisting of three samples per site were studied the sites were taken from the chinji nagri dhok pathan and upper siwalik formations which span the last 14 m y of earth history the formations have been deformed in the ongoing himalayan orogeny and are exposed today in sections which dip at angles of from 10 to 90 in different directions a characteristic direction of magnetization was isolated at all sections by thermal demagnetization at temperatures of from 550 to 650 c the sediments have been folded within the last 2 m y and because of a positive fold test it can be shown that the characteristic magnetization of these sediments was acquired before folding four of the sections have directions of magnetization which have been rotated in a counter clockwise fashion up to 40 however sections taken along the indus river the north flank of the soan syncline and the south flank of the salt range show small counter clockwise rotations of under 10 these observations are in agreement with previous suggestions that strata in the salt range have been moved to the south and rotated in a counter clockwise fashion the observations reported here indicate that the paleomagnetic poles derived from cambrian and permian formations within the salt range have probably also suffered rotation and should be removed from consideration in gondwanaland reconstruction of the paleozoic

hydrogen sulphide release to surface waters at the precambrian cambrian boundary changes in environmental conditions at the precambrian cambrian transition around 542 million years ago have been suggested as a possible explanation for the apparent rapid increase in abundance of multicellular organisms known as the cambrian explosion the nature of the environmental changes is still a matter of debate however wille et al now report molybdenum isotope signatures of black shales from two stratigraphically correlated sample sets with a depositional age of about 542 million years with the help of a box model of the oceanic molybdenum cycle they find that intense upwelling of hydrogen sulphide rich deep ocean water best explains the observed early cambrian molybdenum isotope signal this suggests that the early cambrian animal radiation may have been triggered by a major change in ocean circulation following a long period during which the ocean was stratified with sulphidic deep water this paper reports molybdenum isotope signatures of black shales from two stratigraphically correlated sample sets with a depositional age of around 542 million years the findings suggest that the early cambrian animal radiation may have been triggered by a major change in ocean circulation terminating a long period during which the proterozoic ocean was stratified with sulphidic deep water animal like multicellular fossils appeared towards the end of the precambrian followed by a rapid increase in the abundance and diversity of fossils during the early cambrian period an event also known as the cambrian explosion 1 2 3 changes in the environmental conditions at the precambrian cambrian transition about 542 myr ago have been suggested as a possible explanation for this event but are still a matter of debate1 2 3 here we report molybdenum isotope signatures of black shales from two stratigraphically correlated sample sets with a depositional age of around 542 myr we find a transient molybdenum isotope signal immediately after the precambrian cambrian transition using a box model of the oceanic molybdenum cycle we find that intense upwelling of hydrogen sulphide rich deep ocean water best explains the observed early cambrian molybdenum isotope signal our findings suggest that the early cambrian animal radiation may have been triggered by a major change in ocean circulation terminating a long period during which the proterozoic ocean was stratified with sulphidic deep water

macrostructures vs microstructures in evaporite detachments an example from the salt range pakistan abstract the salt range pakistan is the surface expression of an evaporite detachment over which the potwar plateau fold thrust belt has moved whilst previous publications regarding this region have focused on the petroleum prospectivity deformation and large scale processes this paper characterises the salt range detachment at the meso 10 cm to 10s of metres and micro scale cm to m and examines correlations to the macro scale 10s of metres to kms two detailed scaled cross sections are analysed alongside structural measurements to characterise the detachment at the meso scale with optical analysis of microstructures that formed during deformation characterising the micro scale both ductile and brittle features observed in cross section indicate composite deformation processes acting simultaneously this contrasts with models of salt detachments behaving homogeneously microstructural analysis indicates processes of grain boundary migration and crystal lattice distortions the microstructurally revealed competition between intra crystalline deformation and recrystallization at shallow depths and low temperatures links passes up scale to mesoscale evaporite mylonites and progressively in the weaker units whereas more brittle processes operate in the stronger lithologies in this near unique outcrop of a the emergent toe of a major salt bearing detachment fault

fold and thrust propagation in the western himalaya based on a balanced cross section of the surghar range and kohat plateau pakistan layer parallel slip is dominant in a wedge tapering about 2 degrees across the 70 km wide kohat foreland fold and thrust belt between the main boundary thrust and the surghar range of northern pakistan balanced cross sections show over 50 line length shortening by blind or partially emergent folding and thrusting of which only about half is documented cover sequence deformation folds with 1 to 5 km wavelengths thrust faults and backthrusts occur in the siwalik clastic wedge over buried tip lines and a zone of decoupling decollement thrusting advanced across the kohat plateau to the southernmost frontal thrust ramp of the surghar range about 2 ma before thrusting 12 20 km to the north of the surghar range in the northern kalabagh fault zone this out of sequence th usting is interpreted as a taper building response to an increased decollement dip above the basement the low critical taper of the kohat surghar wedge is explained by the nearly flat basement and low basal shear traction along eocene and eocambrian evaporite layers

the transition from tethys to the himalaya as recorded in northwest pakistan early cenozoic sedimentary rocks exposed in the kohat plateau of northwestern pakistan record tectonic closure of the tethys sea and development of a restricted marine basin that formed during himalayan collision between india asia and a series of microplates in the paleocene initial subsidence of the basin was caused by the downward deflection of the indian plate in response to loading of the asian plate the western margin of the early eocene basin was dominated by deposition of shale sandstone and conglomerate derived from microplates located to the north and west of the indian continental margin the eastern margin of the basin was a carbonate shelf and sabkha flat salt deposition occurred subaqueously in the central parts of the basin in the late early eocene redbeds derived from the northwest were deposited by a fluvial and or deltaic system this influx of clastic sediments marks the earliest record of terrestrial foreland basin deposition in northwest pakistan during the middle eocene the basin was reflooded and a carbonate shelf developed relative sea level rise may reflect subsidence of the indian plate in response to continued crustal loading in the himalayan suture zone uplift and erosion occurred between the late eocene and miocene possibly related to a peripheral bulge south of the himalayan suture zone the main phase of himalayan foreland basin fluvial deposition began in the miocene renewed uplift related to final collision of india and afghanistan during the pliocene is recorded by a thick sequence of conglomerate in the western kohat plateau correlation with eocene sedimentary rocks from southern pakistan to northern india delineates the depositional systems that developed as the tethys sea closed during himalayan convergence

response to comments on the age and evolution of the grand canyon revealed by u pb dating of water table type speleothems pederson et al and pearthree et al offer critical comments on our study of the age and evolution of the grand canyon both sets of authors question our use of incision rates from two sample sites located outside the canyon and present alternative interpretations of our data as we explain even without the sites in question our data support a precursor western grand canyon older than 6 million years

deformation of brittle ductile thrust wedges in experiments and nature 1 even though the rheology of thrust wedges is mostly frictional a basal ductile decollement is often involved by comparison with purely frictional wedges such brittle ductile wedges generally display anomalous structures such as backward vergence widely spaced thrust units and nonfrontward sequences of thrust development laboratory experiments are used here to study the deformation of brittle ductile thrust wedges results are compared with natural systems in the jura mountains and the northern pakistan salt range and potwar plateau two series of three models are used to illustrate the effects of varying the basal wedge angle and shortening rate v these two parameters directly control variations in relative strength between brittle and ductile layers bd coupling wedges with strong bd coupling low and high v give almost regular frontward sequences with closely spaced thrust units and as such are not significantly different from purely frictional wedges weak bd coupling high and low v gives dominantly backward thrusting sequences intermediate bd coupling produces frontward backward oscillating sequences the spacing of thrust units increases as coupling decreases back thrusts develop in parts of a wedge where bd coupling is weak regardless of the thrust sequence wedges with weak bd coupling need large amounts of bulk shortening more than 30 to attain a state of equilibrium at which stable sliding along the base occurs on this basis we argue that a state of equilibrium has not yet been attained in at least some parts of the jura mountains and eastern salt range and potwar plateau thrust systems

geometry and development of zindapir anticlinorium sulaiman range pakistan abstract surface geological field and landsat images and subsurface geophysical seismic reflection and borehole data were analyzed for geometry and development of n s oriented frontal zindapir anticlinorium in the sulaiman range pakistan the anticlinorium with its four segments of structural relief salients north to south as dhodak rodho affiband and zindapir extends over about 130 km with east vergence of the fold axis of general ns trend highly oblique to the plate convergence vector based on seismic and well data correlation sedimentary strata are interpreted with an east to west increase in thickness over the basement along the western passive margin of the indian plate the basement is modelled to have ns trend with gentle 2 5 westward dip ns well correlation along the fold axis and seismic reflection interpretation depict structural relief of 2 4 km along different salient s based on seismic reflection profiles shallow rooted pop ups in tertiary and cretaceous strata are interpreted contrary to their earlier interpretation as thick skinned structures the core of the anticlinorium is occupied with duplication of jurassic and older triassic strata of flat ramp flat geometry as a fault bend fold and an anticlinal stack due to variable shortening from edges to the centre across strike of the anticline it is interpreted to develop along lateral ramps oblique to the direction of tectonic transport along the eastern edge of the sulaiman fold belt sfb shortening along the zindapir anticlinorium reflects a fraction of 37 mm yr convergence along thrust faults of flat and ramp geometry the zindapir anticlinorium serves an example for better understanding of oblique mountain fronts active tectonics and hydrocarbon exploration in the region

comment on age and evolution of the grand canyon revealed by u pb dating of water table type speleothems polyak et al reports 7 march 2008 p 1377 reported that development of the western grand canyon began about 17 million years ago however their conclusion is based on an inappropriate conflation of plio quaternary incision rates and longer term rates derived from sites outside the grand canyon water table declines at these sites were more likely related to local base level changes and miocene regional extensional tectonics

structure and kinematics of the central sivas basin turkey salt deposition and tectonics in an evolving fold and thrust belt this work has been made possible by funding from total s a in the framework of the structural geology chair at e2s university of pau pays adour held by jean paul callot

timing of india asia collision geological biostratigraphic and palaeomagnetic constraints 1 a range of ages have been proposed for the timing of india asia collision the range to some extent reflects different definitions of collision and methods used to date it in this paper we discuss three approaches that have been used to constrain the time of collision the time of cessation of marine facies the time of the first arrival of asian detritus on the indian plate and the determination of the relative positions of india and asia through time in the qumiba sedimentary section located south of the yarlung tsangpo suture in tibet a previous work has dated marine facies at middle to late eocene by far the youngest marine sediments recorded in the region by contrast our biostratigraphic data indicate the youngest marine facies preserved at this locality are 50 6 52 8 ma in broad agreement with the timing of cessation of marine facies elsewhere throughout the region double dating of detrital zircons from this formation by u pb and fission track methods indicates an asian contribution to the rocks thus documenting the time of arrival of asian material onto the indian plate at this time and hence constraining the time of india asia collision our reconstruction of the positions of india and asia by using a compilation of published palaeomagnetic data indicates initial contact between the continents in the early eocene we conclude the paper with a discussion on the viability of a recent assertion that collision between india and asia could not have occurred prior to 35 ma

kinematic evolution and structural styles of fold and thrust belts fold and thrust fat belts occur worldwide and have long been the focus of research of structural geologists who have devised a variety of techniques to image characterize and model their main structural features this introductory chapter reviews the principal geological features of fat belts formed in different settings emphasizing aspects related to their kinematic evolution and structural styles despite great advances challenges remain particularly in the understanding of the spatial and temporal evolution 4d of fat belts and their controlling factors these research efforts are being assisted by the growing availability to researchers of relatively new tools to collect field data high quality 3d seismic data and computer and laboratory modelling tools this volume includes technical papers presented in the conference international meeting of young researchers in structural geology and tectonics yorsget 08 held in oviedo spain together with other papers on the same theme these papers deal with fat belts in different parts of the world and cover a broad range of different aspects from detailed structural analysis of single structures to regional issues and from studies based on classical field structural geology to modelling

comment on age and evolution of the grand canyon revealed by u pb dating of water table type speleothems polyak et al reports 7 march 2008 p 1377 reported speleothem data leading to their inference that the western grand canyon incised much earlier than previously thought this contradicts several lines of published geological knowledge in the region hinges upon unjustified hydrogeological assumptions and is based on two anomalous data points for which we offer alternative explanations

mechanics of the salt range potwar plateau pakistan a fold and thrust belt underlain by evaporites the salt range and potwar plateau are part of the active foreland fold and thrust belt of the himalaya in northern pakistan in this region the distance from the main boundary thrust mbt to the front of the fold and thrust belt is very wide 100 150 km because a thick evaporite sequence forms the zone of decollement recent studies have combined seismic reflection profiles petroleum exploration wells bouguer gravity anomalies and surface geology to construct cross sections in the eastern central and western salt range potwar plateau areas in this study the sections are compared with a model that considers the mechanics of a fold and thrust belt to be analogous to that of a wedge of snow or soil pushed in front of a bulldozer chapple 1978 davis et al 1983 dahlen et al 1984 dahlen 1984 models which include the effects of evaporites at the base chapple 1978 davis and engelder 1985 suggest that these thrust belts will have 1 narrow 1 cross sectional tapers 2 larger widths than areas not underlain by evaporites 3 symmetrical structures and 4 changes in deformational style at the edge of the evaporite basin the section across the eastern potwar plateau most closely resembles this latter model having 1 a taper of 0 8 0 1 2 a width of 100 150 km 3 thrust faults that verge both to the north and south and 4 structures rotated 30 counterclockwise with respect to the salt range from the observed taper and pore fluid pressures of the eastern potwar plateau estimates of the values for the yield strength of the evaporites o and the coefficient of internal friction of the overlying wedge are calculated as o 1 33 1 50 mpa and 0 95 1 04 which are then applied to the other cross sections in the central and western sections a basement uplift the sargodha high interferes with the front of the fold and thrust belt this feature causes the ramping of the salt range thrust and produces a relatively steep basement slope 2 4 beneath the potwar plateau this dip in the presence of the weak evaporite decollement is sufficient to provide critical taper no topographic slope is necessary and the thrust wedge of the southern potwar plateau is pushed over the decollement without significant internal deformation the northern potwar plateau is strongly folded and faulted yet the topographic slope remains flat although the deformation suggests that evaporites are not present there the observed taper in the northern potwar plateau is best fitted by the model with evaporites at the decollement combining this with published paleomagnetic and geologic constraints a model for the evolution of the northern potwar plateau suggests that the area deformed as a steeply tapered 3 5 5 5 thrust wedge until approximately 2 million years ago when the southward propagating decollement encountered the evaporites between 2 ma and the present the northern potwar plateau has been pushed along the salt decollement without deformation and erosion has reduced its original steep topographic slope to a nearly level surface

40ar 39ar and field studies of quaternary basalts in grand canyon and model for carving grand canyon quantifying the interaction of river incision and normal faulting across the western edge of the colorado plateau 40ar 39ar dates on basalts of grand canyon provide one of the best records in the world of the interplay among volcanism differential canyon incision and neotectonic faulting earlier 40k 40ar dates indicated that grand canyon had been carved to essentially its present depth before 1 2 ma but new 40ar 39ar data cut this time frame approximately in half new ages are all 723 ka with age probability peaks at 606 534 348 192 and 102 ka strategic sampling of basalts provides a semicontinuous record for deciphering late quaternary incision and fault slip rates and indicates that basalts flowed into and preserved a record of a progressively deepening bedrock canyon the eastern grand canyon block east of toroweap fault has bedrock incision rates of 150 175 m ma over approximately the last 500 ka western grand canyon block west of hurricane fault has bedrock incision rates of 50 75 m ma over approximately the last 720 ka fault displacement rates are 97 106 m ma on the toroweap fault last 500 600 ka and 70 100 m ma on the hurricane fault last 200 300 ka as the river crosses each fault the apparent incision rate is lowest in the immediate hanging wall and this rate plus the displacement rate is sub equal to the incision rate in the footwall at the reach scale variation in apparent incision rates delineates 100 m ma of cumulative relative vertical lowering of the western grand canyon block relative to the eastern block and 70 100 m of slip accommodated by formation of a hanging wall anticline data from the lake mead region indicate that our refined fault dampened incision model has operated over the last 6 ma bedrock incision rate has been 20 30 m ma in the lower colorado river block in the last 5 5 ma and displacement on the wheeler fault has resulted in both lowering of the lower colorado river block and formation of a hanging wall anticline of the 6 ma hualapai limestone in modeling long term incision history extrapolation of quaternary fault displacement and incision rates linearly back 6 ma only accounts for approximately two thirds of eastern and approximately one third of western grand canyon incision this incision discrepancy for carving grand canyon is best explained by higher rates during early 5 to 6 ma incision in eastern grand canyon and the existence of miocene paleocanyons in western grand canyon differential incision data provide evidence for relative vertical displacement across neogene faults of the colorado plateau basin and range transition a key data set for evaluating uplift and incision models our data indicate that the lower colorado river block has lowered 25 50 m ma 150 300 m relative to the western grand canyon block and 125 150 m ma 750 900 m relative to the eastern grand canyon block in 6 ma the best model explaining the constrained reconstruction of the 5 to 6 ma colorado river paleoprofile and other geologic data is that most of the 750 900 m of relative vertical block motion that accompanied canyon incision was due to neogene surface uplift of the colorado plateau

3d evolution of fold and thrust belts formed by oblique convergence abstract this paper presents the results of a series of scaled analogue models designed to simulate thrust belt development formed by orthogonal and oblique convergence the models were constructed to produce doubly vergent orogenic wedges with a pro wedge and a retro wedge separated by an uplifted orogenic core models were constructed from homogeneous layered sandpacks in a 3 m 1 3 m deformation rig the progressive evolution of the models was recorded using digital photography and the photographs were animated for analysis the experiments investigated convergence obliquities from orthogonal 90 to as low as 15 obliquity orthogonal models produced long linear critically tapered pro wedge fold and thrust belts parallel to the convergence margin together with a narrow uplifted core and a steep retro wedge thrust system the taper angle of the pro wedge was typically 11 12 whereas the retro wedge maintained a steeper taper of 38 42 models where the convergence vector was oblique at angles of 60 and 45 to the margin produced doubly vergent thrust wedges with thrust faults trending parallel to the margin there was little evidence of linked penetrative strike slip faulting but en echelon riedel like shear systems developed in the 45 oblique model subordinate oblique slip motion was observed on some thrust faults in contrast for 30 and 15 oblique convergence models strong deformation partitioning developed with steeply sloping pro wedges that did not have critical tapers through going linked strike slip faulting was developed that cut the uplifted axial zones of these models analysis of the models by animation of the digital photographs shows how the thrust systems initiated and propagated in particular it is clear that at any one time several thrusts were moving simultaneously serial cross sections through the moderately oblique convergence models 60 45 are almost indistinguishable from the orthogonal model cross sections the results of orthogonal convergence experiments compare well to the map patterns of faults and folds in the salt range pakistan 60 and 45 oblique convergence models compare well to the zagros where some strain partitioning on strike slip faults occurs the highly oblique models show very strong strain partitioning with penetrative margin parallel strike slip faulting similar to that found in ne venezuela

thrust kinematics in the kohat plateau trans indus range pakistan abstract the kohat plateau consists of a heavily deformed and structurally elevated thrust sheet pop ups broad synclines and narrow fault and evaporite cored anticlines record high level translation of a large thrust mass along eocene evaporites a lower detachment level is also inferred located at the base of the mesozoic palaeozoic section this lower detachment is common to both the kohat and the adjacent potwar plateaux whereas the upper level is restricted to the kohat beneath the kohat a blind imbricate stack of pre tertiary rocks is developed above their roof thrust the foreland basin fill of kohat records greater internal deformation compared to that of the adjacent potwar plateau in contrast the potwar thrust belt displays a greater amount of overthrusting on its basal surface this displacement emerging in the salt range total shortening across the two plateaux is comparable but is accommodated in an areally smaller thrust belt with a higher structural relief in the kohat as compared to the potwar structural province the resultant geographical offset of the thrust front is denoted by the hukni kalabagh lateral ramp the differences in the thrust kinematics are tentatively suggested to be caused by the mechanical response of the orogenic wedge to different imposed geometries of the wedge laterally within the basin the kohat plateau appears to have a lower basal dip than does the western potwar and thus shows greater internal deformation

a karst hydrology model for the geomorphic evolution of grand canyon arizona usa abstract the evolution of grand canyon started 85 ma when the southwestern hualapai plateau section of the colorado plateau began uplifting this uplift initiated a northeast trending drainage canyon system laramide paleo grand canyon that was to constrain all later routes including that of the colorado river this drainage proceeded down dip but up the stratigraphic section so that northward incision intersected progressively younger paleozoic to mesozoic rock we propose a capture of groundwater by the karstic redwall limestone at rm 197 that shifted the drainage direction of this early canyon along a n60 e trending section to rm 130 uplift of the kaibab arch at 80 65 ma forced coconino plateau drainage to divert around the west side of the arch rather than northeast across it in the mid tertiary an arizona river in the western grand canyon transported shinumo clasts to the california sespe formation and a magmatism tectonic volcanism episode occurred on and south of the hualapai plateau by 17 ma basin and range down faulting furthered earlier miocene canyon headward erosion eastward and then northward into utah causing a complete regional drainage reversal southward this miocene western paleo grand canyon river incised into the redwall muav karst aquifer so as to supply the 12 6 ma hualapai limestone with high 87sr 86sr carbonate spring water a 6 0 5 5 ma final connection between the east and west sides of the kaibab arch was accomplished by karst piracy drainage traversing under the arch this complexity of origin separate canyon sections joined drainage reversals and a final karst connection is why grand canyon remains enigmatic to geologists

co evolution of eukaryotes and ocean oxygenation in the neoproterozoic era the oxygenation of the earth s deep oceans is often thought to have triggered the evolution of simple animals a review article proposes that instead the evolution of animal life set off a series of biogeochemical feedbacks that promoted the oxygenation of the deep sea

spatial variability in oceanic redox structure 1 8 billion years ago the deposition of iron formations ceased about 1 84 billion years ago reconstructions of ocean chemistry suggest that the advent of euxinic conditions along ocean margins preferentially removed dissolved iron from the water column in the form of the mineral pyrite inhibiting widespread iron oxide mineral deposition

reappraisal of the ages of neoproterozoic strata in south china no connection with the grenvillian orogeny the jiangnan fold belt separates the yangtze and cathaysia blocks in south china and has long been considered grenvillian in age in order to place south china in central rodinia it consists of deformed early neoproterozoic strata that are unconformably overlain by undeformed late neoproterozoic strata and intruded by undeformed and unmetamorphosed granitic plutons zircons from the early neoproterozoic strata yield u pb ages as young as 830 ma and one granitic pluton has a zircon u pb age of ca 827 ma the 830 ma mafic rocks along the southeastern margin of the yangtze block have arc affinity geochemical characters whereas mafic rocks younger than 830 ma have typical ocean island basalt oib like compositions thus we suggest that the early neoproterozoic strata were deposited on an active continental margin prior to amalgamation of the yangtze and cathaysia blocks at ca 830 ma the overlying late neoproterozoic strata were deposited in the intracontinental rifted nanhua basin at 820 730 ma and probably reflect backarc spreading above the long lived 950 735 ma oceanic subduction zone along the northern and western margin of the yangtze block this model is consistent with the secular tectonic evolution of south china during the neoproterozoic the jiangnan fold belt is therefore not a grenvillian feature as previously suggested and there is no evidence to place south china in central rodinia instead we believe that south china was located in a marginal position relative to this supercontinent

rapid long term rates of denudation high rates of erosion 1 15 mm yr of fluvial strata have persisted over intervals of 0 2 1 5 m y and across areas of 60 2000 km2 in the cenozoic foreland basin of northern pakistan these rates occur in areas associated with thrust shortening and they indicate that erosion nearly kept pace with the rates of latest miocene to pleistocene uplift such high rates of erosion are predicted to promote hindward imbrication of thrusts and to reduce the amount of subsidence directly attributable to thrust loading

physical analog centrifuge model investigation of contrasting structural styles in the salt range and potwar plateau northern pakistan abstract we use scaled physical analog centrifuge modeling to investigate along and across strike structural variations in the salt range and potwar plateau of the himalayan foreland fold thrust belt of pakistan the models composed of interlayered plasticine and silicone putty laminae comprise four mechanical units representing the neoproterozoic salt range formation basal detachment cambrian eocene carapace sequence and rawalpindi and siwalik groups neogene molasse on a rigid base representing the indian craton pre cut ramps simulate basement faults with various structural geometries a pre existing north dipping basement normal fault under the model foreland induces a frontal ramp and a prominent fault bend fold culmination simulating the salt range the ramp localizes displacement on a frontal thrust that occurs out of sequence with respect to other foreland folds and thrusts with a frontal basement fault terminating to the east against a right stepping east dipping lateral ramp deformation propagates further south in the east strata to the east of the lateral ramp are telescoped in ene trending detachment folds fault propagation folds and pop up structures above a thick basal detachment salt range formation in contrast to translated but less deformed strata with e w trending salt range structures to the west the models are consistent with salt range potwar plateau structural style contrasts being due to basement fault geometry and variation in detachment thickness

deep confined karst detection analysis and paleo hydrology reconstruction at a basin wide scale using new geophysical interpretation of borehole logs summary deep karst voids can be identified by a new method of geophysical interpretation of commonly used borehole logs in deeply confined carbonate aquifers we show that deep buried karst voids can be characterized by combining this geophysical interpretation together with geological and hydrological data and with known speleological constraints we demonstrate how this characterization can reveal past hydrological regimes and allow mapping of karst distribution on a basin wide scale a combined analysis of geophysical geological hydrological and speleological data in the confined yarkon taninim aquifer israel led us to reconstruct past groundwater levels at different relief and sea levels with the karst voids as a marker for long term flow close to the water table paleo canyons along the mediterranean sea shoreline strongly affected the region s paleo hydrology by serving as major outlets of the aquifer during most of the cenozoic we conclude that intensive karstification was promoted by flow periods of longer duration and or higher flux and flow velocities close to the aquifer s past and present outlets in addition we suggest that karst voids found under shallow confinement were developed by renewed aggressivity due to hypogene water rising in cross formational flow becoming mixed with fresh lateral water flow from the east

deformation within an exposed salt wall recumbent folding and extrusion of evaporites in the dead sea basin abstract despite the enormous global interest in salt tectonics which is largely driven by its importance to hydrocarbon exploration direct field based studies of salt exposed at the earth s surface are rare however mount sedom located at the western side of the dead sea basin presents one such opportunity for detailed analysis of salt and the associated sedimentary and structural record of its movement the sedom salt wall is a 10 km 1 5 km n s trending ridge comprising a range of late miocene pliocene evaporites and clastics which have penetrated the overlying pleistocene clastic sequence the salt wall displays a moderate steep west dipping western margin and an overturned west dipping eastern flank the sedimentary record of passive wall growth includes sedimentary breccia horizons that locally truncate underlying beds and are interpreted to reflect sediments having been shed off the crest of the growing salt wall structurally the overturned eastern flank is marked by upturn within the overburden extending for 300 m from the salt wall deformation within the evaporites is characterised by ductile folding and boudinage while a 200 m thick clastic unit within the salt wall forms a tight recumbent fold traceable for 5 km along strike and associated with a 500 m wide inverted limb this overturned gently dipping limb is marked by ne directed folding and thrusting sedimentary injections and a remarkable attenuation of the underlying salt from 380 m to

active faulting south of the himalayan front establishing a new plate boundary abstract new tectonic uplifts south of the salt range thrust and himalayan front thrust hft represent an outward step of the plate boundary from the principal tectonic displacement zone into the indo gangetic plain in pakistan the lilla anticline deforms fine grained overbank deposits of the jhelum river floodplain 15 km south of the salt range the anticline is overpressured in eocambrian non marine strata in northwest india south of dehra dun the piedmont fault pf lies 15 km south of the hft coalescing fans derived from the himalaya form a piedmont old piedmont zone 15 20 km wide east of the yamuna river this zone is uplifted as much as 15 20 m near the pf and bedding is tilted 5 7 northeast holocene thermoluminescence optically stimulated luminescence dates for sediments in the old piedmont zone suggest that the uplift rate might be as high as several mm a the old piedmont zone is traced northwest 200 km and southeast another 200 km to the nepal border these structures analogous to protothrusts in subduction zones indicate that the himalayan plate boundary is not a single structure but a series of structures across strike including reactivated parts of the main boundary thrust north of the range front the hft sensu stricto and stepout structures on the indo gangetic plain displacement rates on all these structures must be added to determine the local india himalaya convergence rate

geology of petroleum in kohat potwar depression pakistan the 36 000 km2 kohat potwar depression in northern pakistan has more than 5 000 m of marine deposition precambrian to eocene with a major break during ordovician to carboniferous more than 10 000 m of miocene to pleistocene alluvial sediments overlies the marine sequence the tectonic depression formed as a result of continent to continent collision at the northwestern margin of the indian plate although the region has been under active petroleum exploration since the mid nineteenth century it has been tested by only 60 exploratory wells ten oil fields have been discovered original recoverable reserves total 200 million bbl of which 112 million bbl has been produced the region has several attractive features for petroleum generation and accumulation i cluding source reservoir trap assemblages and thermal maturity regimes total ultimately recoverable hydrocarbon resource of the area is estimated at 2 4 billion bbl of oil equivalent many unexplored surface and subsurface prospects and stratigraphic leads are known parts of the region particularly the bannu depression and kohat salt zone can be regarded as frontier areas based on the exposed geology and available seismic information we believe these areas are promising recent discoveries of dakhni field 1983 and dhurnal field 1984 which were the first discoveries in the northern part of the platform zone of the potwar plateau and production from paleozoic horizons have added new dimension to petroleum prospects of the area the region needs careful reevaluation of available information exploratory drilling on selected targets and detailed exploration in its western part

pyrite morphology and redox fluctuations recorded in the ediacaran doushantuo formation abstract recent geochemical studies of the doushantuo formation ca 635 551 ma in south china suggested that the ediacaran ocean was strongly stratified with an oxic surface layer above a euxinic wedge that was sandwiched within ferruginous deep waters this ocean redox model however was derived largely from the data obtained from stratigraphic sections in the yangtze gorges area that according to recent paleogeographic reconstruction were deposited in a restricted intrashelf lagoon in order to test the redox conditions in open ocean deep water environments we have conducted a detailed morphological analysis of authigenic pyrites from the upper to lower slope sections of the doushantuo formation in analogy to modern euxinic basins such as the black sea framboidal pyrites with smaller and less variable size distribution are taken as evidence for sulfide precipitation in euxinic water column while larger and more variable framboidal and euhedral pyrites are formed or diagenetically altered in sediments with an overlying oxic dysoxic water column except for a few brief intervals pyrites from the doushantuo formation in upper slope sections siduping and taoying sections are mainly of early diagenetic origin and do not record water column euxinia during deposition in contrast pyrites from the doushantuo formation in the lower slope section wuhe section are dominated by fine grained framboids indicative of pervasive water column euxinia below chemocline in both upper and lower slope sections temporal changes in genetic pyrite types occur at centimeter to decameter scales suggesting frequent chemocline fluctuations the overall decrease in abundance of framboidal pyrites toward the upper doushantuo formation in upper slope sections suggests increasing water column oxygenation and deepening of the chemocline macroalgae and metazoan fossils are found mainly from shale intervals without syngenetic pyrites in upper slope sections indicating the sensitivity of macroscopic eukaryotes to the ocean chemocline the redox fluctuations recorded by the doushantuo pyrites compels for comprehensive geochemical data in deep water successions to further test the existing paleoceanographic models of the ediacaran ocean

strike slip faulting in a foreland fold thrust belt the kalabagh fault and western salt range pakistan the 120 km long kalabagh fault zone is formed by transpressive right lateral strike slip along the western salt range potwar plateau allochthon in northern pakistan lateral ramping from a decollement thrust along an eocambrian evaporite layer produced nnw to nw trending folds and ne to n dipping thrust faults in a topographically emergent zone up to 10 km wide piercing points along the main kalabagh fault indicate 12 14 km of middle to late quaternary right lateral offset the older right lateral surghar fault displaced axes of frontal folds of the eastern surghar range by 4 5 km total displacement is reduced northward in the kalabagh fault zone where north dipping thrust faults splay to the west cumulative right slip offset in the kalabagh fault zone is comparable to displacement along the salt range frontal thrust at a minimum average displacement rate of 7 10 mm year near the indus river since 2 ma in the basement which dips 2 3 north along the kalabagh fault a nnw trending discontinuous ridge beneath the lateral ramp is interpreted from residual gravity anomalies the eastern flank of this basement ridge probably ramped allochthonous strata upward from a depth of over 5 km in the kalabagh fault zone kalabagh faulting displaced and uplifted holocene terrace deposits and shifted the course of the indus river eastward a high slip rate and associated seismicity indicate that the kalabagh fault zone should be considered active and capable of earthquakes

passive roof duplex geometry in the frontal structures of the kirthar and sulaiman mountain belts pakistan abstract exploration for hydrocarbons over the past few years has greatly improved our understanding of the geometry of frontal mountain belt structures in this study we introduce and discuss the concept of the passive roof duplex using as the main example the kirthar and sulaiman ranges in the baluchistan province of pakistan structures similar to those described here have been recognized previously in other mountain belts and they appear to exist as a common feature in many more frontal regions of mountain belts our example of a passive roof duplex which we describe from pakistan is compared briefly with similar structures reported by others the passive roof duplex is here defined as a duplex whose roof thrust has backthrust sense passive roof thrust and whose roof sequence those rocks lying above the roof thrust remains relatively stationary during foreland directed piggy back style propagation of horses within the duplex