gravel bodies in the kumtagh desert and their geomorphological implications although developed in predominantly arid environments desert geomorphology sometimes bears information about past environmental change china s kumtagh desert has only recently been studied by researchers these investigations revealed the existence of several unique features compared with other chinese deserts including gravel bodies distributed in the northern part of the desert this paper summarizes the results of previous research in the region as well as information obtained from remote sensing and field investigations then discusses the geological background underlying quaternary geomorphology and the types development stages and geomorphological implications of the desert s gravel bodies four main types of gravel bodies and four developmental stages were identified it is suggested that the great elevation difference between the altyn tagh mountains and the kumtagh desert caused by uplift of the qinghai tibetan plateau constitutes the overall background for the development of gravel bodies but subsequent climatic events were the direct causes of their evolution the gravel bodies resulted from alluvial deposits on loose fine sediments mainly of aeolian origin that were subsequently subjected to wind erosion erosion cycles then progressively scattered these gravels to form gravel sheets the gravel bodies have three main geomorphological implications they record anomalous ancient climate events after the dune field formed and have little influence on the development of nearby seif dunes in the northeast demonstrate that the altyn tagh mountains are the main sediment source for the kumtagh desert and suggest that the evolution of the environment and geomorphology of the kumtagh desert have been influenced by neotectonic movements

identification of fractured carbonate vuggy reservoirs in the s48 well area using 3d 3c seismic technique a case history from the tarim basin

seismic conditioning and attenuation of high angle coherent noise in a mixed carbonate and siliciclastic setting campos basin offshore brazil a case study we demonstrate the use of two industry standard noise attenuating algorithms f k and p filtering to attenuate coherent noise improve event continuity and obtain more reliable interpretation within the pampo field campos basin offshore brazil we analyze 3d seismic data for noise type and associated maximum dip and then determine optimal attenuating parameters required by the algorithms in the crossline direction coherent noise with dips as high as 16 to 18 ms trace in the data masks real reflected signals in the inline direction the noise exhibited an approximately zero dip the filtering process eliminated noise trains and improved event continuity as well as obtained better well to seismic tie the output wavenumber associated with noise trains is less than the nyquist wavenumber therefore we conclude that the noise is not related to spatial aliasing but to other undetermined sources though the noise occurs within the entire data volume it is most severe in the vicinity of the carbon

geometry and kinematics of the arlar strike slip fault sw qaidam basin china new insights from 3 d seismic data abstract the right stepping en echelon kunbei fault system consisting of the hongliuquan arlar xiii and kunbei faults features importantly in the tectonic evolution of the southwest qaidam basin the 3d seismic cross section interpretation and key horizon similarity attribute analysis show that the nww striking arlar fault is composed of two steeply dipping faults f1 and f2 in cross sectional view and branches eastward into two west dipping faults f5 and f6 in map view the fact that the strata above t 2 the base of the early miocene xiayoushashan formation become dramatically thinner toward the high points of the arlar fault suggests an early miocene initiation ca 22 0 ma for this fault as indicated by the windowed amplitude related attribute maps the arlar fault and f5 one branch of the arlar fault have cumulative sinistral offsets of 8 6 8 7 km and 5 2 5 4 km respectively these considerably greater strike slip components in conjunction with the respective maximum true dip slip displacements of

slope failure of chalk channel margins implications of an upper cretaceous mass transport complex southern england the importance of mass transport and bottom currents is now widely recognized in the upper cretaceous chalk group of northern europe the detailed dynamics and interaction of the two phenomena are difficult to study as most evidence is based on seismic data and drill core here field observations provide evidence for recurring margin collapse of a long lived campanian channel compressionally deformed and thrust chalk hardgrounds are correlated to thicker non cemented chalk beds that form a broad gentle anticline these chalks represent a slump complex with a roll over anticline of expanded non cemented chalk in the head region and a culmination of condensed hardgrounds in the toe region observations strongly suggest that the slumping represents collapse of a channel margin farther northwards the contemporaneous succession shows evidence of small scale penecontemporaneous normal faulting towards the south here interpreted as gravitational settling of the chalk immediately adjacent to the channel margin detailed biostratigraphic studies and sedimentological observations provide evidence for at least two discrete collapse events and suggest the slumping to be the result of channel margin oversteepening rather than evidence for a regional tectonic phase the described example thus serves as an analogue for processes commonly only inferred from subsurface data

the origin and distribution of soluble salts in the sand seas of northern china article i nfo article history basedonsamples takenfrom four large sandseasof northernchina thispaper first provides basicdataabout the concentrations and chemistries of soluble salts in deserts of northern china and then discusses the origins and parameters triggeringgeographicalvariations the total concentration ofsoluble saltsinthe aeolian sandsof four large sand seas in northern china ranges between 0 14 and 1 32 with the ph of the soluble salts solution mixing ratio of sand and water 1 5 changing between 8 4 and 9 6 confirming alkaline soil conditions in these regions sodiumchloride andbicarbonateare the dominantsaltsoccurringassoluble saltsinthe aeolian deposits of these sand seas the geographical changes of soluble salts concentration display a clear correlation with regionalclimaticparameters i e precipitationandtemperature thedominationofsedimentationofsolublesalts in the aeolian sands deposited via atmospheric processes is discussed which are heavily associated with dry deposition the mean percentages of na and cl derived from dry depositions are estimated to be n90 in both badain jaran and taklamakan deserts

using multi attribute neural networks classification for seismic carbonate fades mapping a workflow example from mid cretaceous persian gulf deposits abstract seismic facies mapping in large seismic surveys can be time consuming even if only a basic overview of the facies distribution is needed therefore this study outlines an approach for the use of volume based seismic attributes from 2d surveys for automated seismic facies mapping within carbonate settings the study area is located in the central persian gulf offshore iran the interval of interest is the mid cretaceous sarvak formation which is part of the extensive cretaceous shallow water carbonate platform of the eastern arabian plate a set of nine volume based seismic attributes calculated from time amplitude and frequency information of post stacked 2d seismic data was chosen to characterize geological information within the interval of interest the volume based attributes were supplemented by two grid based attributes to highlight structural elements the geological significance of each attribute was evaluated by comparing it with results of seismic sedimentological geomorphological studies furthermore statistical methods were applied to highlight direct relationships amongst the attributes the results of these tests were then used to choose a limited set of attributes for neural network based multi attribute classifications the results show that seismic attributes derived from 2d surveys can be used to map basic seismic facies types in carbonate settings and that the outlined general approach might be applied in other studies

3 d seismic attributes applied to carbonates coherency mapping has become a widely used tool within amoco and is being applied in both frontier exploration and exploitation areas coherency and other 3 d seismic attributes have been successfully used to identify and delineate features in clastic depositional environments including reworked deltaic sand bodies deltaic channels with associated point bars slump features debris flow outrunner blocks and various geologic drilling hazards including faults salt diapirs buried channels and shallow gas pockets

linear dunes on titan extensive dunes produced by wind transport of sand sized particles are common on earth and are also seen on mars and venus saturn9s moon titan is now shown to have similar dunes

seismic stratigraphy of the chalk group in the norwegian central graben north sea abstract the late cretaceous to early palaeogene chalk group in the norwegian central graben contains prolific hydrocarbon reservoirs that have been producing at high rate for more than forty years based on integration of regionally extensive 3d seismic data and numerous wells this paper describes the seismic development of the chalk group with particular focus to the syndepositional geomorphological features produced by the activity of bottom currents and large scale gravity flows using standard seismic stratigraphic interpretation techniques eight seismic sequence boundaries are identified which in turn define seven seismic stratigraphic sequences characterized by different seismic facies and well log signatures the seismic sequences can be grouped into three sequence groups that reflect the general tectono stratigraphic evolution of the chalk depositional system in the norwegian central graben during the late cretaceous uplift of the lindesnes ridge and the albuskjell anticline due to inversion tectonic and halokinesis modified the physiography of the norwegian central graben basin and affected the style of chalk sedimentation by influencing the location and importance of gravity flows in addition bottom currents sea level fluctuations and environment changes significantly influenced the chalk depositional system creating regional unconformities and influencing the input of terrigenous material in the chalk epeiric sea

geochronological and geochemical constrains on petrogenesis of the huangyangshan a type granite from the east junggar xinjiang nw china abstract the huangyangshan pluton occurs in the kalamaili region which is situated in the central part of the central asian orogenic belt east junggar xinjiang nw china the granitoid rocks are composed of medium grained biotite richterite arfvedsonite alkali feldspar granite fine grained arfvedsonite alkali feldspar granite and microgranular enclaves the granites have a pronounced a type affinity they are metaluminous to weakly peraluminous and calc alkaline to alkaline in composition with high concentrations of na 2 o k 2 o varying from 8 4 to 9 2 wt high feot mgo and 10 000 ga al ratios low abundances of cao mgo and tio 2 enrichment in some liles such as rb and th and hfses such as zr y and rees except eu depletion in sr and ba moreover they display characteristic tetrad ree patterns and non charac trace element behavior which is well demonstrated in highly differentiated rocks with strong hydrothermal interaction the u pb zircon la icp ms ages of the host rocks and enclaves are 311 5 ma and 300 6 ma respectively the similar of these two ages suggests that host rocks and enclaves formed at a same time furthermore the time span closely corresponds to known ages of post collisional a type granitoids of the junggar terrane geochemical geochronological and isotopic data e nd t in the range 5 2 to 6 6 and i sr mostly in the range 0 7031 0 7041 suggest that the huangyangshan intrusions and the enclaves are of mixed origin and are most probably formed by the interaction between the lower crust and mantle derived magmas in the late carboniferous post collisional tectonic setting a 2 type granite the magma for the huangyangshan granites was derived by partial melting of an enriched subcontinental lithospheric mantle sclm that was modified by slab derived components from an earlier subduction event this melting resulted from heat supplied from the asthenosphere through an opening created during the break off of an oceanic slab this further proves the important contribution of the late paleozoic granitic magmatism in terms of vertical crustal growth in northern xinjiang

control of internal structure and fluid migration pathways within the barbados ridge decollement zone by strike slip faulting evidence from coherence and three dimensional seismic amplitude imaging the application of three dimensional seismic reflection and coherence imaging to the study of the decollement zone of the barbados ridge accretionary complex has provided new insights into the relationships among internal structure fluid flow and previously unrecognized strike slip faulting combined coherence and seismic amplitude imaging of the decollement zone reveal anomalous northeast trending lineaments parallel to and abutting zones of high amplitude negative polarity reflections analysis of these lineaments shows them to be penetrative structures dipping southeast with apparent reverse dip slip offset isopach mapping of the accretionary wedge indicates significant right lateral displacement across these structures these faults apparently channel fluid flow within the decollement zone and the prominent northeast trending conduits so formed are readily visible as high amplitude negative polarity reflections additionally north northeast trending zones of variable coherence and high positive amplitude are inferred barriers to up structure fluid migration pathways movement along strike slip structures probably alternates with displacement along the decollement zone northeast trending strike slip faults extend for 13 km crossing the length of the survey area and into the incoming oceanic plate active arc oblique strike slip faulting of the decollement zone beneath the barbados ridge accretionary wedge implies a stress regime in that 1 is fixed and 2 and 3 either transpose with time or are nearly equal this state of stress may be a common occurrence in forearc tectonism and may have led to the formation of many as yet unrecognized arc oblique strike slip faults at convergent margins

characterization of a deeply buried paleokarst terrain in the loppa high using core data and multiattribute seismic facies classification the recognition of paleokarst in subsurface carbonate reservoirs is not straightforward because conventional seismic interpretation alone is generally not sufficient to discriminate karstified areas from their surroundings in the loppa high norwegian barents sea a protracted episode of subaerial exposure occurring between the late paleozoic and mid triassic late permian to anisian resulted in a significant overprinting of the previously deposited carbonate units here we map the extension of the karstified areas using an integrated approach consisting of 1 a core study of critical paleokarst intervals 2 a three dimensional 3 d seismic stratigraphic analysis and 3 a 3 d multiattribute seismic facies sf classification a core retrieved in the flat topped loppa high revealed breccia deposits at least 50 m 164 ft thick which probably resulted from cave collapses following the burial of the karst terrain the sf classification was tested on a 3 d cube to 1 discriminate the respective sf related to the breccia deposits compared with other sf and 2 to estimate their spatial extent seismic facies analysis suggests that breccias occupied the topmost area of the structural high extending up to 12 km 7 mi in width 46 km 29 mi in length and tens of meters in thickness the inference of such a large amount of breccia suggests that a significant part of this terrain was derived from the amalgamation of successive cave development events including periods of subaerial exposure and subsequent burial and collapse resulting in a coalesced collapsed paleocave system previous observations from the loppa high revealed the presence of karst plains associated with sinkholes caves and other dissolution phenomena associated with the breccia facies further suggesting that a large volume of carbonate rocks in this area was affected by subaerial exposure and karstification our integrated approach and proposed karstification model could be applied to similar sedimentary basins that accommodate deeply buried carbonate successions affected by protracted episodes of subaerial exposure where only few wells as well as 3 d seismic data are available

geomorphological patterns in a linear dune field and ages of the linear dunes in the northern kumtagh desert northwest china the unique linear dunes in the northern kumtagh desert of northwest china have inspired enthusiastic debate among aeolian geomorphologists over their origins and classification their uniqueness lies not only in their morphology but also in their geomorphological patterns in this paper the geomorphological patterns and ages of the linear dunes in the northern kumtagh desert are analyzed using the pattern analysis method that was recently adopted by geomorphologists the analysis suggests that these linear dunes have developed since 13 ka bp during the late part of the most recent deglaciation stage when the region s dry climate was favorable for dune formation the differences in dune construction time within this region result from the complex factors that control their formation and spatial variations in the local environment but these factors were not strong enough to prevent us from estimating the dune age recorded by the geomorphological patterns with acceptable precision it is also suggested that the pattern analysis method can be used to estimate dune ages in the absence of more reliable dating methods

large scale controls on the development of sand seas in northern china abstract although sand seas are located in arid regions given that the proportions of dune areas vary greatly from region to region they are clearly influenced by other factors as well as aridity this paper discusses the distribution pattern and major features of sand seas and large fields of stabilized dunes in northern china and demonstrates the main influences on their development it appears that the availability of onsite loose sediments not wind strength is critical to the occurrence of the sand seas on a regional scale tectonic endorheic basins or areas of alluvial fans or forelands of mountain ranges are advantageous to the accumulation of fluvial sediments and thus are ideal locations of large sand seas in an arid climate the large dune fields currently stabilized by vegetation were active sand seas during the drier periods of the late pleistocene and early holocene the distribution patterns of chinese sand seas suggest that the height or size of the dunes in the sand seas are determined more by the availability of sands than any other potential factors as the sand seas in china account for a large portion of deserts in the middle latitudes of the northern hemisphere taklamakan is the second largest sand sea on earth knowledge of these sand seas past changes is important for understanding climatic changes in the terrestrial regions of mid latitudes

granule ripples in the kumtagh desert china morphology grain size and influencing factors granule ripples are found mainly in four regions of the kumtagh desert in china they are characterized by an asymmetrical shape with gentle lower slopes on both sides and abrupt crests the ripples tend to be oriented perpendicular to the prevailing winds except when they form near obstacles such as yardangs the wavelengths range between 0 31 m and 26 m and heights h range from 0 015 m to 1 m the relationship between wavelength and height can be described by a simple linear function and the mean ripple index h is about 20 4 for the study sites the sediments are poorly sorted with negative to very negative skewness at lee and stoss slopes and between ripple troughs which confirms the poured in and shadow appearance described by previous researchers the bimodal or trimodal distributions of grains with modes of 1 16 0 5 and 3 16 and the enrichment of coarse particles at the ripple surface with coarse granule contents ranging between 5 2 and 62 1 indicate that the underlying layer is the original sediment source and that the granule ripples resist erosional processes although the impact of saltating particles and consequently the creep and reptation of coarse grains are responsible for granule ripple initiation at a micro scale however the characteristics of local sediments wind regimes and topographical obstacles as well as the feedbacks among bedform and airflow more strongly affect the development and alignment of granule ripples at a macro scale

the sand seas of titan cassini radar observations of longitudinal dunes the most recent cassini radar images of titan show widespread regions up to 1500 kilometers by 200 kilometers of near parallel radar dark linear features that appear to be seas of longitudinal dunes similar to those seen in the namib desert on earth the ku band 2 17 centimeter wavelength images show 100 meter ridges consistent with duneforms and reveal flow interactions with underlying hills the distribution and orientation of the dunes support a model of fluctuating surface winds of 0 5 meter per second resulting from the combination of an eastward flow with a variable tidal wind the existence of dunes also requires geological processes that create sand sized 100 to 300 micrometer particulates and a lack of persistent equatorial surface liquids to act as sand traps

3d volumetric multispectral estimates of reflector curvature and rotation one of the most accepted geologic models is the relation between reflector curvature and the presence of open and closed fractures such fractures as well as other small discontinuities are relatively small and below the imaging rangeofconventionalseismicdata dependingonthetectonic regime structural geologists link open fractures to either gaussian curvature or to curvature in the dip or strike directions reflector curvature is fractal in nature with different tectonic and lithologic effects being illuminated at the 50 m and1000 m scales untilnow suchcurvatureestimateshave been limited to the analysis of picked horizons we have developed what we feel to be the first volumetric spectral estimates of reflector curvature we find that the most positive and negative curvatures are the most valuable in the conventional mapping of lineations including faults folds and flexures curvatureismathematicallyindependentof andinterpretatively complementary to the well established coherence geometric attribute we find the long spectral wavelengthcurvatureestimatestobeofparticularvalueinextracting subtle broad features in the seismic data such as folds flexures collapse features fault drags and under and overmigrated fault terminations we illustrate the value of these spectral curvature estimates and compare them to other attributes through application to two land data sets a salt domefromtheonshorelouisianagulfcoastandafractured karsteddatavolumefromfortworthbasinofnorthtexas

pseudo feathery dunes in the kumtagh desert abstract the kumtagh desert is the last explored desert in china the unique patterns on aerial photographs and satellite images have led previous researchers to the conclusion that the kumtagh desert is the only place over the world where typical feathery dunes are developed and that some unique wind regimes are at work recent field investigation reveals that the feathery patterns in fact reflect the albedo contrasts between the seif dunes bright dune like drifts and the dark inter dune lag sediments the wind regime in the area containing the so called feathery dunes is typical of the regime that produces seif dunes that were considered to be shafts of the feathery dunes and the vanes of the feathery dunes are in fact bright dune like drifts with indistinct height from the surroundings rather than true transverse dunes further analysis indicates that the sediments of seif dunes dune like drifts and dark inter dune flats differ in grain size distribution mineralogy reflectance spectrum and particle micro morphology sediments that constitute seif dunes and dune like drifts are finer and poorly rounded contain relatively more quartz and hence have higher albedo while the sediments that constitute the dark inter dune flats are coarser and better rounded contain far less quartz but relatively more andesite and dacite and hence have lower albedo as a result what was originally perceived as unique feathery dunes are in fact only pseudo feathery dunes composed primarily of seif dunes this discovery also demonstrates that blowing sand drifts can form dune like patterns that remain visible for long periods of time it is important to distinguish between the patterns of true dunes and those of dune like drifts pseudo dunes that cause albedo contrasts in interpreting remote sensing images

new azimuthal binning for improved delineation of faults and fractures we suggest and test a new way to define azimuth binning in kirchhoff prestack migration with this new definition we sort seismic data by the azimuth of the average travel path traversed from the source to the subsurface image point and back to the receiver rather than the azimuth between source and receiver on the surface of the earth this approach avoids mixing the typically weaker side scattered energy with the stronger in plane reflections thereby providing greater leverage in identifying image contributions from out of the plane steeply dipping reflectors fractures and faults we examine the impact of this new imaging approach combined with analysis of seismic attributes that have proved useful for fracture detection on data from the fort worth basin texas united states we find that the image of features such as reflectors and discontinuities focus into azimuths perpendicular to the strike of each feature the discrimination achieved in the azimuthal domain allows for an increased resolution in analysis of geologic features according to their strike direction it should also result in improved residual azimuthal velocity analysis

lineament preserving filtering recently developed seismic attributes such as volumetric curvature and amplitude gradients enhance our ability to detect lineaments however because these attributes are based on derivatives of either dip and azimuth or the seismic data themselves they can also enhance high frequency noise recently published structure oriented filtering algorithms show that noise in seismic data can be removed along reflectors while preserving major structural and stratigraphic discontinuities in one implementation the smoothing process tries to select the most homogenous window from a suite of candidate windows containing the analysis point a second implementation damps the smoothing operation if a discontinuity is detected unfortunately neither of these algorithms preserves thin or small lineaments that are only one voxel in width to overcome this defect we evaluate a suite of nonlinear feature preserving filters developed in the image processing and synthetic aperture radar sar world and apply them to both synthetic and real 3d dip and azimuth volumes of fractured geology from the forth worth basin usa we find that the multistage median based modified trimmed mean algorithm preserves narrow geologically significant features of interest while suppressing random noise and acquisition footprint

bright dunes on mars seasonal changes observed on the surface of mars can in part be attributed to the transport of geological materials by wind1 images obtained by orbiting spacecraft in the 1970s showed large wind formed features such as dunes and revealed regional time varying albedos that could be attributed to the effects of dust erosion and deposition but the resolution of these images was insufficient to identify different types and sources of aeolian materials nor could they reveal aeolian deposits other than large dunes or extensive surface coverings that were redistributed by dust storms here we present images of mars with up to 50 times better resolution these images show that martian dunes include at least two distinct components the brighter of which we interpret to be composed of relatively soft minerals possibly sulphates we also find large areas of the martian surface that have several metres or more of aeolian mantle lacking obvious bedforms

raked linear dunes in the kumtagh desert china abstract linear dunes are extensive in sand seas and dune fields around the world but they take a range of forms due to the complex factors that control their development raked linear dunes composed of primary ridges and subsidiary ridges that lie almost perpendicular to the primary ridges were recently identified in the northern part of china s kumtagh desert the primary ridges are typical linear dunes but the subsidiary ridges display vestiges of barchan dunes the subsidiary ridges are sufficiently short that they do not greatly affect the general appearance of the linear dunes however the raked linear dunes in the kumtagh desert have several unique characteristics that distinguish them from typical linear dunes these dunes develop in an environment that is deficient in available sediment and under a wind regime typical of linear dunes an environment with a high wind energy and a directional variability index rdp dp around 0 5 the raked linear dunes appear to have evolved from barchans following a modified form of tsoar s 1984 model barchans formed under a northern wind regime were modified by an eastern wind regime oriented at an oblique angle to the barchans the strengths of the two wind regimes are similar under these conditions the barchans became reoriented with the limbs farthest from the eastern winds extending to form subsidiary ridges and the limbs closest to the eastern winds forming the primary ridges which appear to form mainly from dune collisions

growth mechanisms and dune orientation on titan dune fields on titan cover more than 17 of the moon s surface constituting the largest known surface reservoir of organics their confinement to the equatorial belt shape and eastward direction of propagation offer crucial information regarding both the wind regime and sediment supply herein we present a comprehensive analysis of titan s dune orientations using automated detection techniques on nonlocal denoised radar images by coupling a new dune growth mechanism with wind fields generated by climate modeling we find that titan s dunes grow by sediment transport on a nonmobile substratum to be fully consistent with both the local crestline orientations and the eastward propagation of titan s dunes the sediment should be predominantly transported by strong eastward winds most likely generated by equinoctial storms or occasional fast westerly gusts additionally convergence of the meridional transport predicted in models can explain why titan s dunes are confined within 30 latitudes where sediment fluxes converge