architecture and facies model in a non marine to shallow marine setting with continuous base level rise an example from the cretaceous denglouku formation in the changling depression songliao basin china abstract the analysis of 2d and 3d seismic data drilled cores and well log data has resulted in a sequence stratigraphic framework of the cretaceous denglouku formation in the changling depression in the underfilled songliao basin the cretaceous denglouku formation can be divided into four third order sequences each sequence consists of two systems tracts a transgressive systems tract and a highstand systems tract a braided river delta is the main sedimentary facies in the study interval these sequences were deposited in a back arc rift basin during a transitional period from fault dominant subsidence to downwarp subsidence a sequence stratigraphic model is discussed based on the above interpretations typical unconformities are absent due to the absence of base level fall instead maximum regressive surfaces which are generally reworked by transgressive ravinement act as the sequence boundaries each sequence bounded by these surfaces can be divided into two depositional units a transgressive unit tst and normal regressive unit hst on land a tst is characterized by a decreasing channel floodplain ratio and an hst is characterized by an increasing channel floodplain ratio lakes are analogs to marine settings in which the shoreline moves forwards and backwards and their strata show alternating retrogradation and progradation patterns the results of this study may encourage the application of similar approaches to the correlation of successions within and beyond the songliao basin

comment on alam akhtar ahmad shabir sultan bhat m ahmad bashir 2015 tectonic evolution of kashmir basin in northwest himalayas geomorphology doi 10 1016 j geomorph 2015 03 025 abstract alam et al 2015 have challenged the classic piggyback tectonic model for the development of kashmir basin nw himalaya however all the evidence shown is completely contrary to the geologic tectonic structural seismologic geodetic and geomorphic data of previous works a perfectly planar major 165 km dextral strike slip fault has been mapped however with such planar geometry any strike slip fault cannot produce a pull apart basin because such basins are characteristic features of step overs and linkage fault geometries and the horsetail structures are impossible for a major planar strike slip fault geometry that is proposed by the authors the recent geodetic data of the kashmir basin strongly refutes the pure strike slip model therefore the structures geomorphology geology and kinematics associated with typical dextral strike slip fault geometry completely contradict to what has been proposed by alam et al 2015

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

petroleum generation and charge history of the northern dongying depression bohai bay basin china insight from integrated fluid inclusion analysis and basin modelling abstract the petroleum generation and charge history of the northern dongying depression bohai bay basin was investigated using an integrated fluid inclusion analysis workflow and geohistory modelling one and two dimensional basin modelling was performed to unravel the oil generation history of the eocene shahejie formation es3 and es4 source rocks based on the reconstruction of the burial thermal and maturity history calibration of the model with thermal maturity and borehole temperature data using a rift basin heat flow model indicates that the upper interval of the es4 source rocks began to generate oil at around 35 ma reached a maturity level of 0 7 ro at 31 30 ma and a peak hydrocarbon generation at 24 23 ma the lower interval of the es3 source rocks began to generate oil at around 33 32 ma and reached a maturity of 0 7 ro at about 27 26 ma oil generation from the lower es3 and upper es4 source rocks occurred in three phases with the first phase from approximately 30 20 ma the second phase from approximately 20 5 ma and the third phase from 5 ma to the present day the first and third phases were the two predominant phases of intense oil generation samples from the es3 and es4 reservoir intervals in 12 wells at depth intervals between 2677 7 m and 4323 0 m were investigated using an integrated fluid inclusion workflow including petrography fluorescence spectroscopy and microthermometry to determine the petroleum charge history in the northern dongying depression abundant oil inclusions with a range of fluorescence colours from near yellow to near blue were observed and were interpreted to represent two episodes of hydrocarbon charge based on the fluid inclusion petrography fluorescence spectroscopy and microthermometry data two episodes of oil charge were determined at 24 20 ma and 4 3 ma respectively with the second episode being the predominant period for the oil accumulation in the northern dongying depression the oil charge occurred during or immediately after the modelled intense oil generation and coincided with a regional uplift and a rapid subsidence suggesting that the hydrocarbon migration from the already overpressured source rocks may have been triggered by the regional uplift and rapid subsidence the expelled oil was then charged to the already established traps in the northern dongying depression the proximal locations of the reservoirs to the generative kitchens and the short oil migration distance facilitate the intimate relationship between oil generation migration and accumulation

shortening rate and holocene surface rupture on the riasi fault system in the kashmir himalaya active thrusting within the northwest himalayan orogenic wedge new mapping demonstrates that active emergent thrust faulting is occurring within the fold and thrust belt north of the deformation thrust front in the nw himalaya the 60 km long riasi fault system is the southeasternmost segment of a seismically active regional fault system that extends more than 200 km stepwise to the southeast from the balakot bagh fault in pakistan into northwestern india two fault strands the main riasi and frontal riasi thrusts dominate the fault system in the study area the main riasi thrust places precambrian sirban formation over folded unconsolidated quaternary sediments and fluvial terraces new age data and crosscutting relationships between the main riasi thrust and the quaternary units demonstrate that the main riasi thrust accommodated shortening between 100 and 40 ka at rates of 6 7 mm yr deformation shifted to the southern frontal riasi thrust splay after ca 39 ka differential uplift of a 14 7 ka terrace yields a range of shortening rates between 3 and 6 mm yr together shortening across the two strands indicates that a 6 7 mm yr shortening rate has characterized the riasi fault system since 100 ka geodetic data indicate that an 11 12 mm yr arc normal shortening rate characterizes the interseismic strain accumulation across the plate boundary due to india tibet convergence these data combined with rates of other active faults in the kashmir himalaya indicate that the suruin mastgarh anticline at the thrust front accounts for the remainder 40 50 of the convergence not taken up by the riasi fault system active deformation and therefore earthquake sources include both internal faults such the riasi fault system as well as rupture of the basal decollement the main himalayan thrust to the thrust front limited paleoseismic data from the riasi fault system the historical earthquake record of the past 1000 yr the high strain rates and partitioning of slip between the riasi fault system and the thrust front demonstrate that a substantial slip deficit characterizes both structures and highlights the presence of a regionally important seismic gap in the kashmir himalaya slip deficit scaling relationships and a scenario of rupture and slip on the basal decollement the main himalayan thrust parsed onto either the riasi fault system or the thrust front or both suggests that great earthquakes mw 8 pose an even greater seismic hazard than the mw 7 6 2005 earthquake on the balakot bagh fault in pakistan azad kashmir

high resolution sequence stratigraphy of clastic shelves iii applications to reservoir geology abstract high frequency clastic shelf sequences contain porous deposits consisting of coastal to shallow water sandstones and conglomerates which may represent very good reservoirs and therefore critical targets for exploration and production as well as for fluid hydrocarbon water or co2 storage the study of these reservoirs following a sequence stratigraphic approach is essential to predict their features and distribution within systems tracts forming high frequency sequences which in turn compose higher rank systems tracts and sequences a critical aspect to improve the exploitability of the reservoirs is their heterogeneity which directly affects the volume of the reservoirs and determine internal compartmentalization the heterogeneity can be primary related to depositional processes influencing grain size and facies distribution and secondary related to diagenesis in particular the primary heterogeneity is referred to the facies variability from distal to proximal settings to the accumulation of condensed shell beds and to facies characteristics of bedsets whereas the secondary heterogeneity derives from diagenetic processes at sequence stratigraphic surfaces and facies contacts and within sandbodies both the distribution of reservoirs and their heterogeneity can be predicted following a high resolution sequence stratigraphic approach ultimately the integration of subsurface data with the analysis of outcrop analogs is essential to better understand the features of clastic shelf reservoirs and to develop 3d models of fluid migration

channel flow extrusion model to constrain dynamic viscosity and prandtl number of the higher himalayan shear zone constraining magnitudes of mechanical and thermo mechanical parameters of rocks and shear zones are the important goals in structural geology and tectonics talbot in j struct geol 21 949 957 1999 such parameters aid dynamic scaling of analogue tectonic models ramberg in gravity deformation and the earth s crust in theory experiments and geological applications 2nd edn academic press london 1981 which are useful to unravel tectonics in further details schultz ela and walsh in j struct geol 24 247 275 2002 the channel flow extrusion of the higher himalayan shear zone hhsz higher himalaya can be explained by a top to s sw simple shear i e the d2 deformation in combination with a pressure gradient induced flow against gravity presuming its newtonian incompressible rheology with parallel inclined boundaries the viscosity of this shear zone along a part of the himalayan chain through india nepal and bhutan is estimated to vary widely between 1016 and 1023 pa s and its prandtl number pr within 1021 1028 the estimates utilized ranges of known thickness 6 58 km of the hhsz that of its top subzone of ductile shear of normal shear sense stdsu 0 35 9 4 km total rate of slip of its two boundaries 0 7 131 mm year 1 pressure gradient 0 02 6 kb km 1 density 2 2 3 1 g cm 3 and thermal diffusivity 0 5 10 6 2 1 10 6 m s 2 along the orogenic trend considering most of the parameters specifically for the sutlej section india the calculated viscosity and the prandtl number pr of the hhsz are deduced to be 1017 1023 pa s and pr 1022 1028 the upper limits of the estimated viscosity ranges are broadly in conformity with a strong tibetan mid crust from where a part of the hhsz rocks extruded on the other hand their complete ranges match with those for its constituent main rock types and partly with those for the superstructure and the infrastructure the estimated mechanical and thermo mechanical parameters of the hhsz will help to build dynamically scaled analogue models for the himalayan deformation of the d2 phase

higher himalayan shear zone zanskar indian himalaya microstructural studies and extrusion mechanism by a combination of simple shear and channel flow thin section studies of the zanskar shear zone zsz rocks reveal a top to sw and subsequent primary and secondary top to ne ductile shearing brittle ductile and brittle extensions top to sw brittle shear steep normal faulting and fracturing in the proposed two phase model of ductile extrusion of the higher himalayan shear zone hhsz a top to sw simple shearing during 22 18 ma was followed by a combination of top to sw simple shear and channel flow at 18 16 ma the second phase simulates a thin zsz characterized by a top to ne shearing the channel flow component ceased around 16 ma the extruding hhsz entered the brittle regime but the top to sw shearing continued until perturbed by faults and fractures variation in the extrusion parameters led to variable thickness of the zsz shear strain after the extrusion is presumably maximum at the boundaries of the hhsz and falls towards the base of the zsz which crudely matches with the existing data the other predictions 1 spatially uniform shear strain after the first stage 2 fastest extrusion rate at the base of the zsz and 3 a lack of continuation of the zsz along the himalayan trend are not possible to validate due to paucity of suitable data non parabolic shear fabrics of the zsz indicate their heterogeneous deformation

revised magnetostratigraphy and characteristics of the fluviolacustrine sedimentation of the kashmir basin india during pliocene pleistocene 1 the pliocene pleistocene karewa group sediments of the kashmir basin india provide an important continental archive for past climatic reconstruction the present study reevaluates the magnetic polarity stratigraphy and the nature of the depositional environment at a 440 m thick section along romushi river near pakharpur 33 48 50 n 74 45 54 e magnetic remanences are predominantly carried by ti rich titanomagnetite and magnetite we identified eight normal and eight reversed polarity magnetozones in this succession ranging between 4 40 and 0 77 ma the polarity sequence includes the new identification of the cochiti and the mammoth and their preceding and succeeding reversed normal as well as the jaramillo subchrons anisotropy of magnetic susceptibility data suggest the existence of northeast and northwest flowing fluvial system before 4 18 ma indicating the pir panjal range at the southwest as the sediment source area following this the valley was under the influence of fluviolacustrine environment between 4 18 and 0 77 ma our results suggest relatively strong flow velocity toward the northeast during the upper gilbert gauss and lower and middle matuyama chrons 4 18 1 07 ma in the upper matuyama chron 1 07 ma the prevailing paleocurrent direction in the basin changed toward the northwest with a reduced flow velocity indicating the emergence of the ancestral jhelum river on the basis of the magnetic polarity chronology the sediment accumulation rate indicates a very low value of 4 6 cm kyr 1 before 1 95 ma to 33 cm kyr 1 between 1 95 and 1 77 ma and 23 cm kyr 1 after 1 77 ma we attribute temporal changes in sedimentation rate to the interplay between climate predominantly westerlies and tectonics pulsating pir panjal uplift

laramide tectonics and humid alluvial fan sedimentation ne uinta uplift utah and wyoming abstract laramide uplift and erosion of the uinta mountains are recorded in a 10 km long outcrop of the lower eocene wasatch formation on the utah wyoming border this 750 m thick package of interbedded sandstones and conglomerates is dominated by a coarsening then fining upward megasequence 650 m thick that records the growth and abandonment of a humid alluvial fun system during a major cycle of uplift and unroofing of the thrust bounded northern flank of the uinta mountains grain size thickness and lateral extent of channel complex deposits increase upward in the lower 400 m of the sequence reflecting construction and northward progradation of the fan grain size and channel complex thickness decrease upward in the upper 250 m of the sequence reflecting gradual reduction of both sedime t yield and sediment caliber during postorogenic lowering of source area relief within the megasequence coarsening up sequences 10 100 m thick built mainly of channel complex deposits reflect progradation of fan lobes punctuated by periodic fan head avulsions these medium scale sequences in turn comprise small scale fining up cycles 1 10 m thick that reflect such fluvial processes on the fan as bar building discrete flood events and the filling and lateral migration of braided stream channels both the medium scale and small scale sequences are commonly underlain by paleosols evidence of debris flows or other mass movement processes is conspicuously lacking above the main megasequence a second thinner megasequence containing lacustrine mudstones and wave reworked conglomerates indicates that the fan persisted as a locus of coarse clastic deposition during the first of a series of lacustrine transgressions that began as ratios of sediment flux to subsidence rate decreased toward the end of the early eocene partial inundation of the fan during this transgression transformed it into a fan delta

dynamics of phytoplankton distribution and photosynthetic capacity in a western norwegian fjord during coastal upwelling effects on optical properties abstract the present study describes the coupling between optical properties and the dynamics of phytoplankton distribution and photosynthetic capacity in the lysefjord during an exceptional coastal upwelling at the mouth of the fjord transparent coastal water was piled up against the sill while more turbid fjord water from the outer fjord system was flowing over the sill creating the intermediate layer which extended further into the fjord this was reflected by high spectral attenuation coefficients in the upper 10 m of the fjord outside the sill clear water with low spectral attenuation coefficients were found below sill depth down to at least 30 m while the attenuation coefficients inside the sill were significantly higher between 10 and 20 m about 4 7 km outwards from the head of the fjord clearer deep basin water was entering the upper layer due to the upwelling which could be traced up to 7 m bounded by the 7 5 c and the 31 salinity isolines in the outer part of the fjord waters with a high chl a content and photosynthetic capacity were observed below the outflowing surface layer containing old water from the inner part of the fjord which was characterized by low nutrient and chl a concentrations maximum quantum efficiencies 0 5 were encountered within this subsurface layer quantum efficiencies exceeded 0 3 when nitrate and silicate concentrations increased above 2 mmol m 3 about 50 of the par light attenuation 0 30 m was caused by chl a and the 1 light depth varied between 27 and 35 m along the transect due to the influence of freshwater outlets non pigmented particles were more abundant in the inner part of the fjord than in the outer part colored dissolved organic matter cdom contributed strongly to absorption within the upper 10 m at wavelengths below 470 nm while scattering was the major attenuation contributor for wavelengths above 600 nm with respect to possible climate change effects on the growth of phytoplankton in norwegian fjords our results indicate that the alteration of coastal wind patterns due to its impact on coastal fjord water exchanges is probably more important than increased temperature and or increased precipitation

tectonic evolution of kashmir basin in northwest himalayas abstract geomorphology has long been recognised as a key to evaluate the interplay between tectonics and landscape geometry in the regions of active deformation we use geomorphic signatures at varied spatial scales interpreted from srtm dem landsat etm data supplemented with field observations to review the tectonic evolution of kashmir basin in northwest himalayas geomorphic evidence is persuasive of a credible nnw sse trending dextral strike slip structure central kashmir fault ckf with the strike length of 165 km stretched centrally over the nnw sse length of the kashmir basin as a result of the strike slip motion and subsequent erosion significant deformation has taken place along the ckf in addition broad geomorphic architecture of the basin reveals typical pull apart characteristics hence we deduce that the kashmir basin has evolved as a pull apart quaternary sediment depression owing to the deformation along the central kashmir fault the spatial distribution pattern of seismic events neic catalogue 1973 2013 and gps measurements published collectively substantiate our geomorphic interpretations

kinematic evolution of fault ramps and its role in development of landslides and lakes in the northwestern argentine andes the quebrada del toro and quebrada de las conchas in the cordillera oriental of northwestern argentina are notable for repeated landsliding and damming of major drainages both areas correspond to displacement transfer zones along major thrust systems that developed during the neogene uplift of the central andes during this period displacement transfer zones were areas of subdued relief that localized where rivers cross the fault systems however neotectonic deformation converted the transfer zones into restraining bends along strike slip systems resulting in enhanced uplift at river crossings the antecedent streams responded by rapidly downcutting into the ascending hanging wall blocks producing precipitous local relief the extreme local relief that was controlled by the kinematic evolution of faulting in both areas provides an effective precondition for landsliding which may have been ultimately triggered by seismicity and gravitational failure aided by enhanced undercutting during past humid conditions

earthquake geology of kashmir basin and its implications for future large earthquakes two major traces of active thrust faults were identified in the kashmir basin kb using satellite images and by mapping active geomorphic features the n130 e strike of the mapped thrust faults is consistent with the regional ne sw convergence along the indian eurasian collision zone the ne dipping thrust faults have uplifted the young alluvial fan surfaces at the sw side of the kb this created a major tectono geomorphic boundary along the entire strike length of the kb that is characterised by 1 a low relief with sediment filled sluggish streams to the se and 2 an uplifted region with actively flowing streams to the sw the overall tectono geomorphic expression suggests that recent activity along these faults has tilted the entire kashmir valley towards ne further the mw 7 6 earthquake which struck northern pakistan and kashmir on 8 october 2005 also suggests a similar strike and ne dipping fault plane which could indicate that the kb fault is continuous over a distance of 210 km and connects on the west with the balakot bagh fault however the geomorphic and the structural evidences of such a structure are not very apparent on the north west which thus suggest that it is not a contiguous structure with the balakot bagh fault therefore it is more likely that the kb fault is an independent thrust a possible ramp on the main himalayan thrust which has uplifting the sw portion of the kb and drowning everything to the ne e g madden et al 2011 furthermore it seems very likely that the kb fault could be a right stepping segment of the balakot bagh fault similar to riasi thrust as proposed by thakur et al 2010 the earthquake magnitude is measured by estimating the fault rupture parameters e g wells and coppersmith in bull seismol soc am 84 974 1002 1994 therefore the total strike length of the mapped kb fault is 120 km and by assuming a dip of 29 avouac et al in earth planet sci lett 249 514 528 2006 and a down dip limit of 20 km a mw of 7 6 is possible on this fault

recent movements along the main boundary thrust of the himalayas normal faulting in an over critical thrust wedge abstract the main boundary thrust mbt is one of the major himalayan thrusts occurring during the cainozoic and it is presently incorporated within the himalayan thrust wedge lesser and outer himalayas displaced above the indian lithosphere nonetheless the mbt shows recent normal displacement along most of its length we suggest that the orientation of the major principal stress within the himalayan thrust wedge deviates significantly from the horizontal and when this deviation exceeds the dip of the vectors normal to back tilted thrusts the normal component of displacement may act along these faults steep north dipping segments of the mbt therefore show a normal component of displacement if a geometrical definition is used but they are faults in a compressional regime where the major principal stress axis has deviated from the horizontal micro structural data recorded along the surkhet ghorahi segment of the mbt are consistent with a strong deviation of the state of stress the presence of such peculiar normal faulting along the mbt is used to calibrate the mechanical characteristics of the belt considered as a coulomb wedge the following characteristics are suggested a very poor strength contrast between basal decollement and rocks in the wedge body b a high pore fluid pressure ratio probably close to 0 8 0 9 and a higher fluid pressure ratio close to 1 0 along the active normal faults if a high internal friction angle close to the byerlee value is considered the strong deviation in principal stress direction may have recently increased due to a taper of the himalayan wedge exceeding the stability boundary and may be controlled by erosion and isostatic uplift rebound of the himalayan range

variable style of transition between palaeogene fluvial fan and lacustrine systems southern pyrenean foreland ne spain two palaeogene fluvial fan systems linked to the south pyrenean margin are recognized in the eastern ebro basin the cardona su ria and solsona sanau ja fans these had radii of 40 and 35 km and were 800 and 600 km2 in area respectively during the priabonian to the middle rupelian the fluvial fans built into a hydrologically closed foreland basin and shallow lacustrine systems persisted in the basin centre in the studied area both fans are part of the same upward coarsening megasequence up to 800 m thick driven by hinterland drainage expansion and foreland propagation of pyrenean thrusts fourteen sedimentary facies have been grouped into seven facies associations corresponding to medial fluvial fan channelized terminal lobe nonchannelized terminal lobe mudflat deltaic evaporitic playa lake and carbonate rich shallow lacustrine environments lateral correlations define two styles of alluvial lacustrine transition during low lake level stages terminal lobes developed whereas during lake highstands fluvial dominated deltas and interdistributary bays were formed terminal lobe deposits are characterized by extensive 100 600 m wide sheet like fine sandstone beds formed by sub aqueous quasi steady hyperpycnal turbidity currents sedimentary structures and trace fossils indicate rapid desiccation and subaerial exposure of the lobe deposits these deposits are arranged in coarsening fining sequences metres to tens of metres in thickness controlled by a combination of tectonics climatic oscillations and autocyclic sedimentary processes the presence of anomalously deeply incised distributary channels associated with distal terminal lobe or mudflat deposits indicates rapid lake level falls deltaic deposits form progradational coarsening upward sequences several metres thick characterized by channel and friction dominated mouth bar facies overlying white grey offshore lacustrine facies deltaic bar deposits are less extensive 50 300 m wide than the terminal lobes and were also deposited by hyperpycnal currents although they lack evidence of emergence sandy deltaic deposits accumulated locally at the mouths of main feeder distal fan streams and were separated by muddy interdistributary bays whereas the terminal lobe sheets expand from a series of mid fan intersection points and coalesced to form a more continuous sandy fan fringe

linking bacterial community structure to advection and environmental impact along a coast fjord gradient of the sognefjord western norway abstract here we present novel data on bacterial assemblages along a coast fjord gradient in the sognefjord the deepest 1308 m and longest 205 km ice free fjord in the world data were collected on two cruises one in november 2012 and one in may 2013 special focus was on the impact of advective processes and how these are reflected in the autochthonous and allochthonous fractions of the bacterial communities both in november and may bacterial community composition determined by automated ribosomal intergenic spacer analyses arisa in the surface and intermediate water appeared to be highly related to bacterial communities originating from freshwater runoff and coastal water whereas the sources in the basin water were mostly unknown additionally the inner part of the sognefjord was more influenced by side fjords than the outer part and changes in bacterial community structure along the coast fjord gradient generally showed higher correlation with environmental variables than with geographic distances high resolution model simulations indicated a surprisingly high degree of temporal and spatial variation in both current speed and direction this led to a more episodic discontinuous horizontal current pattern with several vortices 10 20 km wide being formed from time to time along the fjord we conclude that during periods of strong wind forcing advection led to allochthonous species being introduced to the surface and intermediate layers of the fjord and also appeared to homogenize community composition in the basin water we also expect vortices to be active mixing zones where inflowing bacterial populations on the southern side of the fjord are mixed with the outflowing populations on the northern side on average retention time of the fjord water was sufficient for bacterial communities to be established

middle tertiary extension recorded by lacustrine fan delta deposits plush ranch basin western transverse ranges california abstract the plush ranch formation upper oligocene and lower miocene consists of more than 1800 m of nonmarine sedimentary and volcanic rocks that record the history of an extensional basin referred to here as the plush ranch basin distinctive depositional facies provenance and sediment transport directions along each basin margin suggest an asymmetric basin shape that is consistent with a half graben origin the northern basin margin consists of sandstone dominated alluvial plain deposits 0 1 1 5 m thick normally graded lenticular sandstone beds small deltaic sequences 1 2 m thick were formed where these alluvial systems flowed southward into a lake lenses of massive boulder rich granitic breccia that represent rockslide deposits derived from a nearby northern granitic provenance nterfinger with the alluvial plain facies in contrast to the northern margin the southern basin margin is represented by coarse grained fan delta deposits matrix and clast supported lenticular conglomerate beds 0 2 5 m thick with interbedded trough cross bedded pebbly sandstone represent braided stream and flood flow and or noncohesive debris flow deposits of alluvial fans that drained a highland area to the south the alluvial fan deposits interfinger to the north with several types of subaqueous sediment gravity flow facies including turbidite sandstone beds and matrix supported debris flow conglomerate each of the basin margin depositional systems grades basinward and to the east into lacustrine deposits that include organic rich dark shale evaporite and limestone the lacustrine deposits represent the central and eastern parts of the plush ranch basin which received little coarse siliciclastic sediment basalt deposits that are at least 50 m thick in the west and thicken eastward are interbedded mainly with the lacustrine facies the southern margin of the plush ranch basin formed along a north dipping normal slip fault along which dip separation increased toward the southwest the northern margin developed on the tilted hanging wall block of this fault this fault was later reactivated in post middle miocene time as the present left lateral strike slip big pine fault the plush ranch is one of several extensional and transtensional basins that formed in southern california and western arizona about 25 20 ma as a response to the change from a convergent to a strikeslip tectonic regime along western north america

eocene early miocene foreland basin development and the history of himalayan thrusting western and central nepal sedimentologic petrographic and u pb detrital zircon ages from middle eocene through early miocene sedimentary rocks in the lesser himalayan zone of western and central nepal indicate that a peripheral foreland basin system had developed in the eastern himalayan collision zone by middle eocene time the shallow marine eocene bhainskati formation accumulated in a back bulge depozone between a southward migrating forebulge and the indian craton migration of the forebulge through this region during eocene oligocene time produced a regional unconformity that spans 15 20 myr by early miocene time the forebulge unconformity was onlapped by the distal fringes of the southward migrating foredeep depozone represented by fluvial deposits of the dumri formation continued southward migration of the foredeep during the neogene accommodated the fluvial siwalik group light mineral provenance data and u pb detrital zircon ages suggest that the bhainskati was derived partly from tethyan sedimentary rocks of the tibetan himalayan zone during initial growth of the himalayan fold thrust belt the dumri was derived from metasedimentary and crystalline rocks of the greater himalayan zone during emplacement of the main central thrust and contemporaneous tectonic unroofing by normal faulting along the south tibetan detachment system the lesser himalayan crystalline thrust sheets were emplaced soon after deposition of the dumri formation 15 10 ma paleocurrent and lithofacies data from the dumri formation indicate deposition by west southwestward flowing rivers that drained into the indus portion of the himalayan foreland basin system during the early miocene thick channel sandstones in the lower dumri may represent the early miocene counterpart of the modern ganges river eastward diversion of the ganges drainage system to near its present location had occurred by 15 ma as the high standing aravalli range on the northern indian shield approached the front of the fold thrust belt assuming reasonable values for the flexural rigidity of indian lithosphere the time span of the forebulge unconformity yields a velocity of 14 33 mm yr for the southward migration of the fold thrust belt relative to india this range of values is consistent with neogene and present day estimates and suggests that only one third to one half of india eurasia convergence has been accommodated by shortening in the himalayan fold thrust belt since the onset of collision

fluvial response in a sequence stratigraphic framework example from the montserrat fan delta spain abstract exceptional exposure of the montserrat fan delta system eocene in northeastern spain provides an excellent framework to evaluate the alluvial response to sea level changes over two different time scales the alluvial system contains multiple fifth order cycles 104 yr and eight fourth order cycles 105 yr fifth order cycles are characterized by long distance shoreline migrations and occasionally by incised basal scour surfaces but not by changes in fluvial style lithofacies or channel stacking pattern fourth order cycles are composed of stacked fifth order cycles and have non erosional basal boundaries vertical sedimentation rates and channel stacking patterns change significantly within fourth order cycles the lower parts of these cycles referred to as the transgressive facies tract show overall shoreline transgression and associated alluvial deposits contain abundant overbank materials with isolated ribbon channel bodies during this time the supply of terrigenous material to the shoreline was reduced as indicated by sediment starvation offshore the overlying middle part of fourth order cycles the lower regressive facies tract differs only in that shoreline is overall regressive and there is increased clastic supply to the offshore in the upper part of hese cycles the upper regressive facies tract channel stacking geometries become denser and more sheet like shoreline regression is more pronounced and vertical aggradation rates are inferred to be reduced changes in the alluvial system during fourth order cycles are most pronounced adjacent to shoreline and die away upstream over just a few kilometers indicating that the base level signal decays away over the distance of a few backwater lengths channel flow depth slope higher frequency fifth order changes in relative sea level appear to produce the largest shoreline migrations but lower frequency fourth order changes have more impact on the channel stacking architecture of the alluvial systems observed changes in alluvial stacking pattern may be most commonly found in tectonically active rapidly subsiding foreland basins because of their back tilted geometry we propose a model in which sediment is trapped in the proximal basin during times of rapid tectonic subsidence and attendant relative sea level rise progradation occurs as erosion rates in the mountain belt increase and rates of subsidence and relative sea level rise diminish changes in alluvial architecture reflect an increase in sediment flux towards the shoreline as less sediment is trapped upstream hence changes in channel stacking pattern coincident with transgressions and regressions likely reflect the interplay between subsidence and sediment supply in the proximal part of the basin and are not necessari y driven by eustatic sea level changes

sequence stratigraphic architectures and sand body distribution in cenozoic rifted lacustrine basins east china cenozoic rifted lacustrine basins in east china display three main basin types 1 basins with steeply dipping boundary fault whose hanging walls tilt along pivot points 2 basins with listric boundary faults whose hanging walls bend along flexural bending points and 3 basins formed by earlier extensional rifting with later strike slip movement superimposed the sequence development is intimately linked to the tectonic movements in the area where second order sequences are regionally correlatable from basin to basin and relate to the large scale tectonic movements in the region third order sequences are related to local tectonic activity and are correlatable within basins between subbasins and sometimes between neighboring basins detailed sequence stratigraphic analysis and mapping of depositional systems demonstrate that sand body distribution patterns are related to sequence stratigraphic frameworks for the three kinds of basins the positions of pivot point zones flexural bend zones and strike slip faults plus the syndepositional faults all control the distribution of depositional systems systems tract and sand bodies these controlling factors can be attributed to different structural and stratigraphic features that change the accommodation structural elements include boundary faults syndepositional faults and abrupt changes in dip stratigraphic controls include preexisting surfaces with local channelization paleobathymetric lows and onlap onto clinoform slopes the lowstand sand bodies deposited at the downdip end of these controlling factors constitute the current and future exploration targets for conventional reservoirs

sequence stratigraphy and architectural variability in growth fault bounded basin fills a review of plio pleistocene stratal units of the crotone basin southern italy field examples from the pliocene to pleistocene succession of the crotone basin document the variability of stratal architecture in syntectonic units deposited in normal fault bounded basins relatively thick trangressive intervals are common within these successions as shown in the zinga 2 zinga 3 and strongoli stratal units transgressive packages are formed by lagoonal mudstones that are abruptly overlain by shoreface sandstones aggradational highstand shallow marine packages are typical of the lower pliocene succession in half graben basins these deposits resulted from balanced conditions between the rate of sediment supply and the rate of creation of accommodation relatively thick forced regressive deposits are common within basins during phases where the accommodation supply ratio is low e g the middle pleistocene san mauro sandstone these deposits influenced by growth faulting and folding recorded base level lowering linked to glacio eustasy a complex stratal architecture may be the consequence of the alternation between tectonic subsidence and uplift e g the serra piani stratal unit such variations are thought to be related to the onset of an earliest mid pliocene transpressional tectonic phase the studied deposits therefore show a marked tectonic control that strongly influenced their stratal architecture these examples represent interesting cases of sequence stratigraphic analysis in growth faulted contexts

a double cycle lake basin formed in extensional to transtensional setting the paleogene nanpu sag bohai bay basin china abstract it has been known that both extensional and transtensional tectonics commonly trigger a one cycle evolution of lake sediments but lake cycle development co controlled by extensional and transtensional tectonics still need identification here we report a double cycle of lake sediments formed in extensional to transtensional phases in the paleogene nanpu sag of the bohai bay basin china the sag successively experienced five phases of lake type evolution characterized by 1 overfilled 2 balanced fill 3 overfilled 4 balanced fill and 5 overfilled extensional tectonics was responsible for the opening of the basin and the initial creation of accommodation 1st through 3rd phase next subsidence increased again through transtensional tectonics resulting in the creation of new accommodation 4th 5th phases investigations show this double cycle lake type evolution is also present in other lake basins with similar tectonic settings e g both extensional and transtensional tectonics a different exploration and exploitation strategy should be devoted to the double cycle evolution of lake basins controlled by extensional to transtensional tectonics in comparison to the single cycle evolution in extensional or transtensional lake basins

the upper cenozoic white river tillites of southern alaska subaerial slope and fan delta deposits in a strike slip setting the white river tillites crop out over 8 km 2 either side of the totschunda fault in the northern foothills of the wrangell mountains in southern alaska and record glacially influenced slope and fan delta deposition in a high relief basin close to an active volcano between 10 and 2 7 ma two measured sections 1 200 and 450 m thick show diamictite and conglomerates interbedded with augite andesite lavas facies range from massive diamictites deposited subaerially as debris flows to crudely stratified sandstones and conglomerates formed by sheet flow processes on alluvial fans and well stratified and normally graded sandstones and conglomerates that accumulated subaqueously as turbidites large scale southward dipping foresets as much as 17 m high identify a fan delta that prograded into a temporary lake the white river succession is identified as a valley infill complex consisting of subaerial slope and lacustrine fan delta deposits there are no in situ primary glacial deposits present in the succession the glacial component of sedimentation was limited to the supply of coarse grained debris identified by the presence of glacially striated and faceted clasts the white river deposits may be typical of glacial sequences preserved as isolated local basin fills in high relief areas such as occur in convergent or strike slip plate margin settings they provide only a limited and fragmentary record of paleoenvironmental changes compared to coeval glacially influenced marine rocks preserved in the yakataga formation 5 km thick along the gulf of alaska coast

diagenesis and reservoir quality of sandstones with ancient deep incursion of meteoric freshwater an example in the nanpu sag bohai bay basin east china abstract an example of diagenesis and reservoir quality of buried sandstones with ancient incursion of meteoric freshwater is presented in this study the interpretation is based on information including porosity and permeability petrography stable isotopic composition of authigenic minerals homogenization temperatures th of aqueous fluid inclusions afis and pore water chemistry these sandstones closely beneath or far from the regional unconformity formed during the late paleogene period are located in the thick shahejie formation in the gaoliu area of nanpu sag bohai bay basin east china early diagenetic calcite cements were leached to form intergranular secondary pores without precipitation of late diagenetic calcite cements in most sandstones feldspars were leached to form abundant intragranular secondary pores but with small amounts of concomitant secondary minerals including authigenic quartz and kaolinite the mass imbalance between the amount of leached minerals and associated secondary minerals suggests that mineral leaching reactions occurred most likely in an open geochemical system and diagenetic petrography textures suggest that advective flow dominated the transfer of solutes from leached feldspars and calcites low salinity and ion concentrations of present pore waters and extensive water rock interactions suggest significant incursion of meteoric freshwater flux in the sandstones distances of the sandstones to the regional unconformity can reach up to 1800 m while with significant uplift in the gaoliu area the burial depth of such sandstones below sea level can be less than 800 1000 m during the uplift and initial reburial stage significant uplift during the oligocene period provided substantial hydraulic drive and widely developed faults served as favorable conduits for downward penetration of meteoric freshwater from the earth s surface unconformity to these sandstone beds extensive feldspar leaching has been occurring since the uplift period coupled high th 95 115 c of afi and low 18 o smow values 17 20 within the quartz overgrowths show that quartz cementation occurred in the presence of diagenetic modified meteoric freshwater with 18 o smow values of 7 2 indicating that authigenic quartz only have been formed during the late reburial stage when meteoric fresh water penetration slowed down secondary pores in thin sections and tested porosity suggest that meteoric freshwater leaching of feldspars and calcite minerals generated approximately 7 10 enhanced secondary porosity in these sandstones meteoric freshwater leaching reactions cannot be ignored in similar sandstones that located deep beneath the unconformity with great uplift moving these sandstones above or close to sea level and with faults connecting the earth s surface with the sandstone beds

autostepping during the transgressive growth of deltas results from flume experiments a series of three dimensional flume experiments on the transgressive growth of deltas conducted with constant rate of relative sea level rise a constant sediment discharge s and constant upstream water discharge q reveals an inbuilt geomorphic process that inevitably forms discrete steps on the abandoned subaqueous deltaic slope the stepped topography and its process of formation are here referred to as autostep s and autostepping respectively the stepped topography is caused by the lateral migration of delta front lobes that inevitably shift landward but fail to cover lobes of older cycles the autostepping arises from the principle of autoretreat combined with autocyclic lateral shifting of the feeder system discrete changes of a s a s or q s are not required to explain the origin of episodic backstepping in an overall transgressive regime allocyclic changes in a and s as commonly invoked in the sequence stratigraphy literature are not an alternative to autostepping but would only enhance or reduce the inbuilt process of autostepping in river dominated delta systems

implications of channel flow analogue models for extrusion of the higher himalayan shear zone with special reference to the out of sequence thrusting the higher himalayan shear zone hhsz contains a ductile top to n ne shear zone the south tibetan detachment system lower stdsl and an out of sequence thrust oost as well as a top to n ne normal shear at its northern boundary and ubiquitously distributed compressional top to s sw shear throughout the shear zone the oost that was active between 22 ma and the holocene varies in thickness from 50 m to 6 km and in throw from 1 4 to 20 km channel flow analogue models of this structural geology were performed in this work a newtonian viscous polymer pdms was pushed through a horizontal channel leading to an inclined channel with parallel and upward diverging boundaries analogous to the hhsz and allowed to extrude to the free surface a top to n ne shear zone equivalent to the stdsu developed spontaneously this also indirectly connotes an independent flow confined to the southern part of the hhsz gave rise to the stdsl the pdms originally inside the horizontal channel extruded at a faster rate through the upper part of the inclined channel the lower boundary of this faster pdms defined the oost the model oost originated at the corner and reached the vent at positions similar to the natural prototype some time after the channel flow began the genesis of the oost seems to be unrelated to any rheologic contrast or climatic effects profound variations in the flow parameters along the hhsz and the extrusive force probably resulted in variations in the timing location thickness and slip parameters of the oost variation in pressure gradient within the model horizontal channel however could not be matched with the natural prototype channel flow alone presumably did not result in southward propagation of deformation in the himalaya

on the influence of topographic factors upon the oxygen consumption rate in sill basins of fjords abstract the rate of oxygen consumption has been estimated for 29 different sill basins of fjords all located in a relatively small area of the norwegian west coast it is found that cons the volume mean rate of oxygen consumption in a sill basin i e below the sill level is inversely proportional to the mean depth h b of the sill basin in addition it is demonstrated that cons decreases with increasing sill depth h t in an approximately linear fashion our results are compatible with a regionally horizontally homogeneous and downward decreasing vertical flux of organic carbon based on data from the present set of sill basins an empirical formula has been derived for cons as a function of h t and h b this may be looked upon as a regionally valid empirical fjord model which may be used to determine whether or not the oxygen consumption in a sill basin is normal

development of coarse grained facies in lacustrine rift basins examples from east africa detailed studies of high resolution and multifold seismic reflection data from the two largest east african rift lakes malawi and tanganyika reveal a complex suite of coarse grained depositional facies these facies occur within specific regions of the controlling half grabens that compose the rift lakes sand prone environments include subaqueous channels and small drowned fluvial complexes channel systems range from large erosional canyons to deep water turbidite channel levee systems lowstand and highstand deltas of axial and shoaling side rivers are volumetrically important coarse grained facies fan deltas develop along the base of major border faults during lake lowstands subaqueous talus fan deposits occur along the base of the border faults during lake highstands lowstand deltas are the best preserved progradational facies in these rift lakes in addition to simple tectonic control drastic tectonically or climatically induced lake level change significantly regulates the production of coarse grained lacustrine synrift deposits

the sequence stratigraphy of fluvial depositional systems the role of floodplain sediment storage abstract the currently used model for alluvial sequence stratigraphy has been criticised miall 1991 and an alternative model is offered here in this model alluviation mainly takes place during transgressive and not highstand phases when accommodation space allows sediment storage the high capacity for some river systems to store floodplain sediments is a critical consideration the effects of climatic and intrinsic geomorphic changes during fluvial deposition are likely to greatly complicate simple base level controlled sequence models and recognising higher order fourth and fifth order cycles will be particularly difficult

controls and evolution of fan delta systems in the miocene pohang basin se korea abstract the miocene pohang basin southeastern korea occurs in the eastern part of the ne sw trending yangsan fault which has experienced right lateral strike slip deformation since the eocene during the miocene however the strike slip movement was negligible and instead was under extensional regime large scale drainage systems were developed at the junction between the strike slip zone and the oblique transfer faults acting as major sources for coarse grained sediments high rate of sediment supply and rapid subsidence of the hanging wall resulted in the progradation of large scale gilbert type fan deltas doumsan duksung and gohyun systems which all show a radial distributional pattern along the steeply inclined footwall scarps created by ne sw trending faults the drainage systems were relatively small here low rate of sediment supply formed scree apron type malgol and yugye systems and steep faced slope type maesan system fan deltas based on variations in sedimentary facies and distribution architecture and overlapping patterns the fan delta systems in the pohang basin can be divided into four stages of evolution during the early stage early miocene alluvial fans prograded into shallow marine setting in the doumsan and duksung systems high rate of sediment supply and rapid rise of relative sea level resulted in the transformation of shoal water type to gilbert type foresets in the malgol and maesan systems rapid sea level rise accompanied with low rate of sediment supply caused transformation of alluvial fans to scree apron type and steep faced slope type fan deltas respectively in the second stage subsidence of the hanging wall formed large scale truncation surfaces in the doumsan and duksung fan deltas coarse grained sediments were continuously supplied in the doumsan system whereas only fine grained sediments were deposited in the duksung system in the malgol system sediment supply was almost terminated in this stage in the third stage middle miocene sediment supply rate of the doumsan fan delta decreased abruptly and the system was overlain by fine grained gilbert type deposits the duksung fan delta was overlain by the maesan and gohyun systems the maesan system prograded further basinward during the last stage late miocene sediment supply of the doumsan and maesan systems was also terminated and the entire basin was draped by fine grained biogenic materials mainly diatoms

the simulation of the sedimentary fill of basins an interactive computer simulation which erects models of sedimentary geometries by filling in a two dimensional basin from both sides with a combination of clastic sediment and or in situ and transported carbonate sediments is described the simulation program is implemented in c using graphical plotting functions data entry including the initial basin configuration the local tectonic behavior the sea level curves the amount and source direction of clastic sediment and the growth rates of carbonates as a function of water depth is performed interactively geometries of clastic and carbonate sediments evolve through time and respond to tectonic movement eustasy and sedimentation clastic modeling includes sedimentary bypass and erosion and sedimentation in alluvial and coastal plains marine shelf basin slope and basin floor settings carbonate modeling includes progradation the development of hard grounds downslope aprons keep up catch up back step and drowned reef settings as well as lagoonal and epeiric settings also included in the model are extensional vertical faulting of the basin sediment compaction and isostatic response to sediment loading sediment geometries are plotted on a graphics terminal as they are computed so the user can immediately view the results based on these observations parameters can be changed and the program rerun until the user is satisfied with the resultant geometry this paper includes output showing the simulation s sensitivity to eustatic sea level variations and variations in sedimentation and subsidence rates also shown are outputs demonstrating the modeling of some examples from the geologic section in the permian basin of west texas and the upper permian of the sichuan basin

the late cenozoic chronologic and stratigraphic development of the kashmir intermontane basin northwestern himalaya abstract the intermontane basin of kashmir developed within the thrust faulted southern margin of the himalayan range detailed lithostratigraphies magnetic polarity stratigraphies and fission track dates on enclosed volcanic ashes were determined at four separate localities in order to develop a chronology of the late cenozoic evolution of the kashmir basin the results indicate that sedimentation had commenced by about 4 m y ago since then over 1300 m of sediments have aggraded at inferred average rates varying from 16 to 64 cm per 1000 yr lacustrine and deltaic sediments dominate the kashmiri sequences and appear to respond sensitively to tectonic events along the basin margins conglomerates shed from the faulted basin margins at about 1 7 2 1 2 7 and 3 0 3 5 m y ago punctuate the predominantly low energy fluviolacustrine depositional record paleocurrent analyses indicate a switch from northeasterly derived conglomeratic facies to southwesterly derived ones about 1 7 m y ago this transition reflects enhanced activity along the main boundary thrust complex to the southwest and an apparent diminution of faulting along the northeastern margin of the basin in the pir panjal range 1400 3000 m of uplift at inferred rates of up to 10 mm yr 1 have terminated widespread sedimentation within the kashmir basin since the middle pleistocene

comment on coexistent pre existing extensional and subsequent compressional tectonic deformation in the kashmir basin nw himalaya by akhtar et al 2017 article in press

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

estimating the viscosity and prandtl number of the tso morari crystalline gneiss dome indian western himalaya the tso morari crystalline tmc gneiss dome in the indian himalaya extruded from a depth of 120 km through an inclined subduction channel of sub elliptical cross section at the leading edge of the indian plate the velocity profile of this gneiss dome is derived after 1 presuming its incompressible newtonian rheology 2 finding the best fit of the outcrop of the gneiss dome to an ellipse 3 taking into account different lithologies to have existed at the top of the extruding gneiss body 4 considering the extrusion to have been driven by the buoyant push of the denser mantle beneath the lighter gneiss and 5 assigning a range of plausible densities for different litho units fitting the known rates of extrusion from a few centimetres up to about one hundredth of a millimetre per year from 53 ma onwards of this gneiss dome to its velocity profile constrains its maximum possible viscosity to 7 5 1022 pa s this magnitude is 102 104 times higher than previous estimates for gneisses and granites alternative explanations of our data are the following 1 there was a fall in extrusion rates of the tmc gneiss from 53 to 30 ma because of an increase in the estimated maximum viscosity from 6 2 1020 to 7 5 1022 pa s possibly indicating a fall in temperature and or compositional change of the tmc gneiss 2 lower the extrusion rates higher are the estimated viscosities 3 the tmc gneiss was more viscous probably due to its eclogite content 4 the estimated maximum viscosity is 102 times higher than that in collision zones and 102 104 times than that in the tibetan lower crust but broadly conforms to that for the crustal channel and average lithospheric and asthenospheric values the high magnitude of maximum possible prandtl number of 1028 of the tmc gneiss might be related to isothermal decompression of the gneiss during its extrusion

sedimentology and mechanism of a lacustrine syn rift fan delta system a case study of the paleogene gaobei slope belt bohai bay basin china abstract fan delta systems have long been studied as a kind of good hydrocarbon reservoirs although many models have been raised according to their local conditions there still exists some controversies regarding the formations of the ones developed in continental syn rift settings taking paleogene es32 3 of gaobei slope belt as an example this paper conducted a comprehensive geological study and a forward depositional modeling the results show that the sediment within the study area came mainly from the northeastern baigezhuang uplift and the northwestern xinanzhuang uplift over a short distance the sedimentary system is characterized by subaerial debris flow subaerial braided channels subaqueous distributary channels front sand bars and front sand sheets furthermore the study area is a balance filled basin that experienced a 3rd order normal regression followed by a transgression during the development of the study interval the results also show that a stable subsidence rate with small magnitude climate changes would be a plausible explain for the entire sequence of the fan delta system in the study area the tectonic subsidence was indeed the dominant driving force to a continental syn rift fan delta system although the climate sediment supply or lake level might bring some lower order e g 4th and 5th order superimpositions this paper proposed a likely model for fan deltas developed in continental syn rift settings which is expected to gain some insights into the forming mechanism and provide some supports for the reservoir characterization of similar and correlative sedimentary systems

coexistent pre existing extensional and subsequent compressional tectonic deformation in the kashmir basin nw himalaya abstract this paper presents a new interpretation of overlapping differential deformations and likely causes of the structural heterogeneity within the kashmir basin representing a prominent and distinctive strain feature in nw himalaya the broad geomorphic expression of the kashmir as an elongated nw se trending sedimentary trough is inconsistent with general compression governing structural trend and deformation pattern of 2500 km long himalayan frontal thrust zone in addition to the general extensional geometry there are prominent anomalous deformation features at varied spatial scales in the basins that imply dominance of extensional tectonics we infer that contrary to the overall compression dominant mechanism of the himalaya the apparent extensional geometry of the basin connotes orogen parallel extensional deformation pull apart triggered by oblique convergence in the nw himalaya moreover we construe that the comparatively younger contractile positive features in form of the geomorphic convexity push up accompanied by out of sequence reverse faulting balapur fault hereafter called as bf within the basin which is generally believed to be associated with the uplift along ne dipping southern thrust complex mbt mct possibly resulted due to the tectonic reversal positive inversion the presence of the compressional features within the locally predominant extensional setting is suggestive of the basin s hybrid character where variable tectonic regimes earlier extension and subsequent compression seem to be coexistent

a quantitative simulation study of asymmetrical tectonic subsidence control on non synchronous sequence stacking patterns of eocene lacustrine sediments in bohai bay basin china abstract compared with large scale passive margin marine basins continental basins are susceptive to local or regional tectonic geomorphologic and climatic influences and can form complicated sequence stratigraphic architectures configurations and sedimentary facies we report herein a quantitative simulation study on the influences of asymmetrical tectonic subsidence on sequence stratigraphic stacking patterns in rift basins by varying tectonic subsidence sediment supply and intra rift lake levels it has been demonstrated that isochronous sequences within a rift basin can exhibit both synchronous and non synchronous stacking patterns as a result of differential asymmetric tectonic subsidence in sequence stratigraphy synchronous stacking patterns refer to isochronous sequences at any parts of a basin which are either all retrogradational or all progradational we propose the concept of non synchronous stacking patterns of isochronous sequence stratigraphy for rift basins non synchronous stacking patterns refer to the fact that within the same basin some parts may concomitantly exhibit stacking patterns that are exactly opposite to that of other parts non synchronous stacking patterns can form when the accommodation space increment a is less than that of sedimentary supply s in one area but larger than or equal to that of s in another moreover the duration of non synchronous stacking patterns is controlled by both a and s recognition of non synchronous stacking patterns within isochronous sequence stratigraphy provides a conceptual model for correlation of sequence stratigraphic units in tectonically asymmetric rift basins in eastern china and similar basins around the world

intermontane basin development in the past 4 myr in the north west himalaya the through the combined use of magnetic polarity stratigraphy with fission track dating of volcanic ashes a new chronology spanning 4 myr has been developed for the intermontane basin of kashmir in the northwestern himalaya

sequence stratigraphy and importance of syndepositional structural slope break for architecture of paleogene syn rift lacustrine strata bohai bay basin e china abstract sequence stratigraphy and syndepositional structural slope break zones define the architecture of the paleogene syn rift lacustrine succession in eastern china s bohai bay basin jiyang huanghua and liaohe subbasins are of particular interest and were our primary research objectives interpretation of 3d seismic data well logs and cores reveals one first order sequence 4 second order sequences and ten to thirteen third order sequences were identified on the basis of the tectonic evolution lithologic assemblage and unconformities in the subbasins of bohai bay basin three types of syndepositional paleo structure styles are recognized in this basin they are identified as fault controlled slope break zone flexure controlled slope break zone and gentle slope the three active structural styles affect the sequence stratigraphy distinct third order sequences within second order sequences have variable systems tract architecture due to structuring effects during tectonic episodes second order sequences 1 and 2 were formed during rifting episodes 1 and 2 the development of the third order sequences within these 2 second order sequences was controlled by the active nw and ne oriented fault controlled slope break zones second order sequence 3 formed during rifting episode 3 the most intense extensional faulting of the basin two types of distinctive lacustrine depositional sequence were formed during rifting episode 3 one was developed in an active fault controlled slope break zone the other in an active flexure controlled slope break zone second order sequence 4 was formed during the fourth episode of rifting syndepositional fault and flexure controlled slope break zones developed in the subsidence center shore to offshore areas of the basin and controlled the architecture of third order sequences in a way similar to that in second order sequence 3 sequences in the gentle slope and syndepositional flexure controlled slope break zones were developed in subaerial region distribution of lowstand sandbodies was controlled primarily by active structuring on the slope break zones and these sandbodies were deposited downdip of the slope break zones sand bodies within lowstand systems tracts have good reservoir quality and are usually sealed by the shale sediments of the subsequent transgressive systems tract they are favorable plays for stratigraphic trap exploration

mid to late holocene oxygen isotopes from voldafjorden western norway basin water in deep silled norwegian fjords is primarily influenced by inflowing atlantic water originating from the norwegian atlantic current nwac previous studies suggest that benthic foraminiferal oxygen isotope records from such fjords are strongly influenced by variability in this current the present paper presents a mid to late holocene record 6 2 2 ka with 17 yr time resolution from a western norwegian deep silled fjord voldafjorden an age model based on ten ams radiocarbon dates on marine carbonates and on one plant macrofossil has been established the study focuses on the oxygen isotope results obtained from two species of benthic foraminifera cassidulina laevigata and uvigerina mediterranea the 18o c laevigata record has systematically larger amplitudes than the 18o u mediterranea record which most likely is related to different life cycles periods of calcification the oxygen isotope results show a clear shift towards higher values between 5 and 4 ka interpreted to reflect

a mechanism for syn collisional rock exhumation and associated normal faulting results from physical modelling abstract properly scaled physical modelling of the subduction of continental lithosphere is performed with a three layer lithospheric model the model includes a strong upper crust a weak ductile lower crust and a strong mantle part the lithosphere is underlain by a low viscosity asthenosphere subduction is produced by a piston push force and the pull force from the mantle lithospheric layer which is slightly denser than the asthenosphere the results of the modelling are tested on the example of the himalayas in the experiments all lithospheric layers subduct into the mantle to a depth corresponding to 200 300 km in nature until the upper crustal layer fails in front of the subduction zone forming a first major thrust fault the mct in our interpretation of the himalayas underthrusting along this fault increases relief which upon reaching a height corresponding to several kilometres in nature is removed mechanically by a blade the blade is moved horizontally back and forth throughout the experiment this erosional unloading mechanism causes the previously subducted segment of the buoyant upper crust to slide upward over the weak lower crust at a rate comparable to the subduction rate the rise of the crustal slice accelerates displacement along the crustal thrust while producing a normal sense motion and exhumation of the material from great depth up to 40 50 km depending on the model parameters along the upper surface of the slice the rapid uplift of the crust then ceases and the orogenesis occurs further due to continuing underthrusting along the first major thrust at a certain stage the crust fails again producing a new major crustal thrust the mbt in the himalayas

pleistocene lacustrine fan delta deposits of the valdarno basin italy abstract during the early pleistocene mouth bar fan deltas formed on the northern margin of the shallow water lacustrine valdarno basin which developed during the last phases of the northern apennines evolution one fan delta studied in detail here is a coarse grained fluvial dominated system and shows characteristics different from the classic gilbert type model the apex is morphologically and sedimentologically similar to those reported for alluvial fans of humid climates very course grained poorly organized deposits dumped as lobes during intense floods or laid down in braided channels predominate downfan in the transition zone braided channels change into stable straight channels lacking evidence of lateral accretion these consist of lenticular pebbly sand and sandy bodies in luded within massive mud and fine sand in the subaqueous zone the straight distributary channels cut into muddy lacustrine deposits are filled with sand distally such channels give way to lenticular bodies composed of sands arranged into coarsening and thickening upward sequences the occurrence of drowned channels is explained by scouring during periods of low water stand or due to hyperpycnal flows the very shallow water the small size and the low energy of the lake favored the formation of mouth bar fan deltas instead of gilbert type foresets