an outline of the plate tectonics of china china is principally a part of the eurasian plate but the margins of the indian and philippine sea plates are involved in the himalayas and in the coastal range of taiwan respectively within the eurasian plate the cathaysian paleoplate is separated from the angaraian paleoplate by the junggar hegen suture which contains paleozoic ophiolites and rare blueschists the three microplates of the cathaysian paleoplate consist of precambrian cratons and or phanerozoic accretionary fold belts these coalesced precambrian cratons record at least six stages of intense orogeny before cratonization the paleozoic to cenozoic accretionary fold belts of china can be correlated with similar events now found in west pacific andean and atlantic type active continental margins ophiolites occupying many of these tectonic zones provide evidence for the age and igneous history of oceanic crust formed during the paleozoic to cenozoic the presence of blueschist in some of these chinese sutures reveals evidence of large scale subduction and tectonic exhumation during consolidation of the eurasian plate cenozoic collision of the eurasian and indian plates produced deformation and uplift of the himalayas strongly influencing the tectonics of western china in contrast mesozoic tertiary evolution of eastern china is typical basin range geology similar to that of the western united states which included development of deep sedimentary basins along with calc alkaline plutonic and volcanic activity associated with crustal thinning and high heat flow the complicated tectonic evolution of china is greatly illuminated by the presence of ophiolites and blueschists in proterozoic to tertiary convergent boundaries these petrotectonic assemblages provide evidence of an extremely mobile history of plate movement in china

lower permian paleomagnetism of the tarim block northwestern china we collected 262 samples at 39 sites in three thick lower permian sections along the northwestern margin of the tarim block the lower permian sections are basalts interbedded with limestones or sandstones or shallow marine limestones and sandstones alone all with biostratigraphic age control alternating field af and thermal demagnetization experiments remove small secondary components and reveal characteristic magnetizations reversed directions consistent with the kiaman reversed interval similar directions between basalts sandstones and limestones a positive fold test and apparent polar wander and polarity changes recorded in underlying devonian sediments all attest to the primary nature of the remanence two paleomagnetic poles one from the limestone section 65 1 n 162 5 e k 128 a95 4 1 n 11 sites and the other from the two basalt sections 54 5 n 172 3 e k 66 a95 4 0 n 21 sites differ primarily in colatitude 8 1 6 5 suggesting a difference in magnetization age permian paleomagnetic poles from tarim siberia north china and south china all differ significantly suggesting substantial post permian relative motions

experimental study of acoustic anisotropy and birefringence in dry and saturated fontainebleau sandstone the velocities of ultrasonic p sh and sv waves have been measured in two perpendicular directions in samples of fontainebleau sandstone as received or thermally cracked dry or saturated under uniaxial stress we have investigated the effect of cracking saturation and uniaxial stress on the velocity of p and s waves in two orthogonal directions anisotropy and the velocity of s waves with two orthogonal polarizations in each direction of propagation birefringence the effect of cracking saturation and uniaxial stress on poisson s ratio has also been investigated the velocity anisotropy is larger for s waves than for p waves and practically disappears in saturated samples birefringence is attenuated in saturated samples inversion of the results using crampin s model gives values of the crack densities in three directions in qualitative agreement with the state of cracking observed by scanning electron microscopy in particular the crack density is found to be near zero in sandstones with r

the fold test in palaeomagnetism summary the fold test suggested by mcelhinny is shown to be inappropriate more correctly one should determine whether the mean direction of a group of sites from one limb of a fold may be distinguished statistically from the mean direction of a group of sites from another limb details of the application of this test are given with examples it is shown that the test indicates significance under far less severe folding than does the test suggested by mcelhinny

first early permian paleomagnetic pole for the yili block and its implications for late paleozoic postorogenic kinematic evolution of the sw central asian orogenic belt we conducted a paleomagnetic study on the early permian volcanic and sedimentary rocks and the neoproterozoic mafic dikes in the yili block nw china magnetite and hematite were proven to be the principal magnetic remanence carriers demagnetizations revealed stable characteristic remanence magnetizations with a sole reversed magnetic polarity the magnetic remanence of only the early permian strata turned out to be primary based on positive fold tests meanwhile the magnetic remanence age of the mafic dikes is ambiguous accordingly the first early permian paleomagnetic pole for the yili block is calculated at 81 5 n 256 5 e n 11 and a95 10 9 comparisons of this new pole with published ones from the yili tarim and south junggar blocks provide new quantitative constraints on late paleozoic kinematic evolution of the sw central asian orogenic belt 1 between the yili and tarim blocks significant relative movement took place along major strike slip faults during the late carboniferous to early permian 580 290 km and the early to late permian 585 340 km and the displacement rate increased from the late carboniferous to early permian 19 3 9 7 mm yr to the early to late permian 29 3 17 0 mm yr 2 a significant relative rotation of 28 3 18 3 in the late permian and a lateral displacement of 630 295 km after the late permian occurred between the yili and south junggar blocks the significant strike slip movements played an important role in the formation of the central asian orogenic belt and should be considered with great attention in tectonic and paleogeographic reconstructions

plate tectonic history basin development and petroleum source rock deposition onshore china abstract china comprises a mosaic of distinct continental fragments separated by fold belts these fold belts are suture zones resulting from the accretion of various fragments formerly separated by intervening areas of oceanic crust the major sedimentary basins onshore china can be classified into four groups those in western china are flexural developing as a result of north south compression in contrast those in the east are extensional and related to development of the pacific oceanic margin in central china basins have a more problematic origin those of north central china ordos sichuan are flexural basins controlled by eastward directed thrusting along their western margin in contrast basins further south chuxiong shiwandashan are predominantly extensional and related to major strike slip movements by synthesizing basin stratigraphies across china in tectonostratigraphic terms and in particular comparing the nature and timing of unconformities it is possible to formulate a coherent model for the palaeoreconstruction of china we identify five major tectonostratigraphic breaks which equate with the collision of the following continental fragments tarim north china carboniferous permian south china block permian triassic qiantang late triassic early jurassic lhasa block late jurassic early cretaceous and india early tertiary prior to permian times the southern margin of eurasia ran approximately along the northern border of modern china the late carboniferous collision of tarim north china with eurasia resulted in the development of a flexural basin junggar and deposition of non marine clastics to the south of the suture shallow marine deposition continued in the late permian early triassic the progressive collision from east to west of the south china block with the north china block resulted in a change to fluvial lacutrine sedimentation across the entire north china tarim block open marine carbonate deposition in the north of the south china block passed southward into a deeper marine clastic sequence deposited in a backarc basin further south a subduction zone existed along the southeastern margin of the south china block in western china northward subduction throughout the triassic resulted in the development of the songban ganzi accretionary prism with retroarc thrusting resulting in flexure and the first development of the tarim basin oblique collision of the qiantang block in the late triassic along the east of the south china block resulted in east west directed thrusting which initiated the suchuan and ordos basins continued strike slip deformation along the south western margin of the south china block resulted in the development of basins with a significant extensional component such as chuxiong the collision of the qiantang block with the southern edge of the tarim basin early jurassic resulted in a renewed clastic influx in both the tarim and junggar basins along the eastern pacific margin a compressional arc and retroarc basin in the south passed northwards into an extensional arc system subduction rollback of the extensional arc initiated rifting in the late jurassic in the eren and songliao basins the late jurassic early cretaceous collision of the lhasa block in the west rejuvenated the thrust systems bordering the western basin and resulted in a renewed clastic influx in the southeast the compressional arc phase culminated in widespread thrusting and folding of early cretaceous age in the northeast extension continued with the progressive migration of the rift system southward with time the arrival of the indian block in the early tertiary rejuvenated the bounding thrust belts of all the western basins in the east the change in convergence of the pacific plate to a more westerly direction is marked by extension and widespread rifting along the entire length of eastern china throughout most of china mesozoic and cenozoic deposition occurred in predominantly non marine environments source rocks in such settings comprise principally mudstones deposited in lakes organic rich mudstones these can accumulate in both deep and shallow lakes in order to accumulate substantial volumes the lake must be significant in space and time in china lacustrine orms occur in both rift and flexural basins lacustrine orms deposited under humid climatic conditions are restricted to the period of maximum tectonic subsidence in the flexural basins of western china source rock deposition follows basin initiation by 20 30 ma in the extensional basins of eastern china source rock deposition takes place 5 15 ma after basin initiation by contrast semi arid and arid climate lacustrine orms whilst being best developed during the period of maximum tectonic subsidence occur at all stages in the basin history

permian sedimentary record of the turpan hami basin and adjacent regions northwest china constraints on postamalgamation tectonic evolution the permian marks an important yet poorly understood tectonic transition in the tian shan region of northwestern china between devonian carboniferous continental amalgamation and recurrent mesozoic cenozoic intracontinental orogenic reactivation the turpan hami basin accommodated up to 3000 m of sediment and is ideally positioned to provide constraints on this transition new stratigraphic data and mapping indicate that extension dominated early permian tectonics in the region whereas flexural foreland subsidence controlled late permian basin evolution lower permian strata in the northwestern turpan hami basin consist of coarse grained debris flow and alluvial fan deposits interbedded with mafic to intermediate volcanic sills and flows in contrast lower permian rocks in the north central and northeastern turpan hami basin unconformably overlie a late carboniferous volcanic arc sequence these lower permian strata include possible shallow marine carbonate rocks and thick volcanic and volcaniclastic rocks that are in turn overlain by littoral to profundal lacustrine facies above a regional lower permian upper permian unconformity regional sedimentation patterns record the development of a more integrated sedimentary basin the upper permian is entirely nonmarine and can be correlated east west along the depositional strike of the basin the lower upper permian consists of a broad belt of braided fluvial deposits shed northward these strata are overlain by fluctuating littoral and profundal lacustrine facies and associated fluvial facies the uppermost permian is characterized by shallow lake plain and fluvial environments the early permian association of diffuse volcanism and partitioning of subbasins by normal faulting is consistent with an early phase of lithospheric extension local relationships indicate west east extension in the turpan hami basin along faults oriented normal to late devonian carboniferous collisional sutures within the tian shan the cause of extension in the wake of carboniferous orogenesis remains enigmatic however the temporal and spatial relationships of the two strain regimes suggest that they are genetically related upper permian stratigraphy and unconformities and local late permian triassic contractional deformation record foreland basin development when the turpan hami region became a wedge top basin with respect to the north tian shan fold and thrust belt flexurally induced late permian subsidence is also manifested in the larger junggar basin to the north where 4000 m of strata are preserved in the foredeep region the turpan hami and junggar basins were depositionally connected for much of the late permian when a vast lacustrine system developed across northwestern china this lacustrine paleogeography was only occasionally interrupted possibly by structural damming during uplift of the orogenic wedge

trace and minor element records in aragonitic bivalve shells as environmental proxies abstract investigation of the geochemical composition of bivalve shells can provide information on changes in the marine environment occurring during the lifespan of an organism three species locally abundant in the adriatic sea were chosen in this study namely glycymeris pilosa callista chione and venus verrucosa of these g pilosa has the longest lifespan exceeding 50 years and therefore presents a potential archive of decadal climate variability the other two species c chione and v verrucosa are commercially important samples were collected alive by scuba diving in the north adriatic sea near barbariga istria major growth increments in these shells form on an annual basis and are clearly visible in shell cross sections enabling correct temporal positioning of geochemical data obtained from different shell parts in this study we applied laser ablation inductively coupled plasma mass spectrometry la icp ms in line scan mode to determine the trace and minor element composition along the major growth axis in the hinge area of the shells objectives of this study were to compare signals within and between species and to relate results to available environmental parameters high resolution time series of na cashell mg cashell and sr cashell display characteristic cyclic variations na cashell minima and mg cashell and sr cashell maxima occur near shell annual growth lines in all three studied species results indicate that seawater temperature is not a main driver for incorporation of these elements ba cashell data vary between years and species and have noncyclic sharp peaks callista chione and v verrucosa specimens show higher peaks and background ba cashell values than g pilosa most pronounced peaks in ba cashell occurred at the beginning of the growing season corresponding to the end of year 2011 and beginning of year 2012 and coincided with unusual dense water formation and subsequent changes in the plankton communities in the adriatic sea implications of our study suggest that synchronous peaks in studied specimens are caused by external forcing which could occur on larger regional scales encouraging future studies covering wider area in the adriatic sea and other parts of the mediterranean

palaeomagnetic constraints on the collision and rotation of north and south china the eastern half of china is dominated by the north china block ncb and south china block scb separated by a complex fold system that trends roughly east west interpretation of the geology of this fold belt has led to a variety of estimates of the age of amalgamation of these two blocks1 7 palaeomagnetic results are few and have also been subject to conflicting interpretations8 11 here we present our own palaeomagnetic results for late permian rocks for both the scb and ncb and summarize other relevant palaeomagnetic data by reinterpreting the polarity given in some previous studies we are able to synthesize the results for the widespread emeishan basalts of the scb and to suggest a new model for the collision and relative rotation of the two blocks

upper permian lacustrine oil shales southern junggar basin northwest china upper permian organic rich lacustrine mudstones oil shales that crop out in the southern junggar basin rank among the richest and thickest petroleum source rock intervals in the world with maximum toc values reaching 34 and rock eval pyrolytic yields s 2 up to 200 kg hc t rock lacustrine sedimentary facies define an overall transgressive regressive cycle of approximately 2000 m gross thickness which includes approximately 800 m of source rocks averaging 4 1 toc and 26 2 kg hc t rock basinal facies comprise silicic organic rich laminated lacustrine mudstones and interbedded siltstones organic matter contained in the mudstones ranges in composition from type i to type iii basinal facies were deposited in a deep oxygen deficient stratified lake lake margi facies consist of nonlaminated siliciclastic mudstones rippled dolomitic siltstones and sandstones and minor limestones maximum toc values are approximately 6 desiccation cracks are common in the marginal facies but evaporite minerals are rare or absent biomarker correlation parameters measured from rock extracts exhibit significant stratigraphic variability but strongly support the hypothesis that upper permian lacustrine oil shales charge the giant karamay field in the northwestern junggar basin karamay oils are characterized by high relative abundances of beta carotane this characteristic is restricted to desiccated facies in the outcrop sections however we therefore propose that an abundance of beta carotane indicates elevated environmental salinities during deposition of the oil shales orographic precipitation induced by a paleo tian shan range may have provided fresh water to the southern areas of the basin while more evaporative conditions prevailed to the north outcrop oil seeps confirm that the outcrop sections have attained sufficient thermal maturity to generate oil t max values range from 431 to 451 degrees c vitrinite reflectances range from 0 73 to 0 88 and sterane isomerization ratios range from 0 30 to 0 48 20s 20s 20r matoil registered trademark computer modeling of burial history and thermal maturity of the outcrop sections indicates that approximately 4 5 km of triassic jurassic cover was needed to bring the oil shales to their current maturity the major phase of hydrocarbon generation in this area appears to have preceded the creation of traps by neogene thrusting which may account for the lack of discoveries in the southern junggar basin most of the oil discovered so far is trapped in structures which originated duri g the late paleozoic or mesozoic

pore fluid effects on seismic velocity in anisotropic rocks a simple new technique predicts the high and low frequency saturated velocities in anisotropic rocks entirely in terms of measurable dry rock properties without the need for idealized crack geometries measurements of dry velocity versus pressure and porosity versus pressure contain all of the necessary information for predicting the frequency dependent effects of fluid saturation furthermore these measurements automatically incorporate all pore interaction so there is no limitation to low crack density the velocities are found to depend on five key interrelated variables frequency the distribution of compliant crack like porosity the intrinsic or noncrack anisotropy fluid viscosity and compressibility and effective pressure the sensitivity of velocities to saturation is generally greater at high frequencies than low frequencies the magnitude of the differences from dry to saturated and from low frequency to high frequency is determined by the compliant or crack like porosity predictions of s

lithological control on shear wave velocity anisotropy in core samples from the taiwan chelungpu fault drilling project abstract the present study provides laboratory constrains on the in situ source of shear wave birefringence in siltstone and sandstone lithologies from the taiwan chelungpu fault drilling project tcdp bench top measurements at ambient pressure and temperature are performed across the end faces of vertically drilled samples while the polarization angle of the source and receiver is rotated from 0 to 360 in azimuth shear wave birefringence in siltstone is low 3 5 and controlled by low angle 30 bedding dip the sandstone samples exhibit moderate 15 shear wave anisotropy due to a network of vertical microcracks with normal about the bedding strike direction as related studies infer that the microcracks responsible for shear wave birefringence in sandstone are also open at depth our results suggest that anisotropy in borehole measurements can simply be accounted for by the observed siltstone and sandstone microstructures i e without invoking larger scale objects nor randomly oriented cracks fractures subjected to triaxial stress state

end permian to mid triassic termination of the accretionary processes of the southern altaids implications for the geodynamic evolution phanerozoic continental growth and metallogeny of central asia the altaids is one of the largest accretionary orogenic collages in the world with the highest rate of phanerozoic continental growth and significant metallogenic importance it is widely accepted that subduction related orogenesis of the altaids started in the late precambrian and gradually migrated southward present coordinates however it is uncertain when and how the building of the altaids was finally completed based on structural geology geochemical geochronological and paleomagnetic data this paper presents late paleozoic to early mesozoic accretionary tectonics of two key areas north xinjiang in the west and inner mongolia in the east together with neighboring mongolia the late paleozoic tectonics of north xinjiang and adjacent areas were characterized by continuous southward accretion along the wide southern active margin of siberia and its final amalgamation with the passive margin of tarim which may have lasted to the end permian to early mid triassic in contrast in inner mongolia and adjacent areas two wide accretionary wedges developed along the southern active margin of siberia and the northern active margin of the north china craton which may have lasted to the mid triassic the final products of the long lived accretionary processes in the southern altaids include late paleozoic to permian arcs late paleozoic to mid triassic accretionary wedges composed of radiolarian cherts pillow lavas and ophiolitic fragments and high pressure ultrahigh pressure metamorphic rocks permian alaskan type zoned mafic ultramafic complexes intruded along some major faults of the tien shan we define a new tarim suture zone immediately north of the tarim craton that is probably now buried below the tien shan as a result of northward subduction of the tarim block in the cenozoic the docking of the tarim and north china cratons against the southern active margin of siberia in the end permian to mid triassic resulted in the final closure of the paleoasian ocean and terminated the accretionary orogenesis of the southern altaids in this part of central asia this complex geodynamic evolution led to formation of giant metal deposits in central asia and to substantial continental growth

diel behavior of stable isotopes of dissolved oxygen and dissolved inorganic carbon in rivers over a range of trophic conditions and in a mesocosm experiment abstract rates of diel 24 h biogeochemical processes in rivers and their effect on daily changes in the concentration of metals and metalloids have been well documented in the literature over the last 20 years investigations into the effects of these processes on aquatic systems and the underlying mechanisms that control the processes can significantly improve our understanding of how natural aquatic environments function and will respond to changing environmental conditions and anthropogenic impacts daily changes in the rates of biogeochemical processes have more recently been shown to influence the stable isotope composition of dissolved oxygen and dissolved inorganic carbon in natural waters here we present a comprehensive picture of the persistence and reproducibility of diel cycles of the 18o composition of dissolved molecular oxygen 18o do and the 13c composition of dissolved inorganic carbon 13c dic across five montana usa rivers investigated over a 4 year period a mesocosm experiment showed the same behavior in 18o do and 13c dic as seen in riverine settings across light and dark periods a cross plot of 18o do and 13c dic from each stream exhibits a clockwise elliptical pattern which is attributed to the daily changes in the balance of metabolic rates as well as air water gas exchange the amplitude of the change in the isotope composition is shown to be directly related to the trophic state of the river and a relationship between net productivity and diel changes in 18o do and 13c dic is presented this relationship between trophic status with 18o do 13c dic and production emphasizes the significance of how rates of biogeochemical processes in natural systems can influence the daily changes in the composition of surface waters

late paleozoic polar wander path for the tarim platform and its tectonic significance abstract stepwise thermal and a f demagnetizations have been carried out on 518 samples 47 sites from the sishichang section across the akesu area in the tarim basin the results lead to a discussion on some problems concerning the tectonic history of the tarim platform and adjacent blocks during the late paleozoic from the late carboniferous until the early permian the tarim platform collided with the kazakhstan block siberian platform and russian platform no large displacements have occurred between these blocks since the mesozoic however the permian pole position of the tarim platform obviously differs from that for the sino korea platform the difference in paleolatitude between the tarim and sino korea platforms in the permian was about 10 their orientations were also different the paleomagnetic result is in contrast to the geologically accepted idea that the two platforms in question occur as a whole in the late paleozoic

continental growth of northwest china the northwest corner of china is the most interior part of central asia and includes parts of the siberian tarim and kazakhstan plates where the junggar and tarim basins are separated by the east west trending tianshan range a preliminary terrane map divides the area into thirteen separate areas which are classified into four types l continental 2 oceanic crust 3 island arc 4 composite the boundaries for these terranes are faults that have been previously defined either by geologic mapping or holocene activity passive consolidation of the southern margin of paleo asia is marked by accretion and subduction of the paleo tethys oceanic basins and by development of volcanic arcs paleomagnetic data indicate that the major plates and associated smaller terranes did not reach final consolidation until the permian or later the stratigraphic record reveals development of intracontinental basins in the late carboniferous followed by the pan asian thermal event that gave rise to widespread intrusion of a type granites of late paleozoic age the frontal collision of india along the southern border of asia in the paleocene reactivated nearly all of the older major strike slip and thrust faults formed during the late paleozoic consolidation of paleo asia the complex nature of the continental growth of central asia has produced and destroyed many varieties of sutures and reconstruction of the original plate and terrane configurations therefore is enigmatic

new paleomagnetic data from the mongol okhotsk collision zone chita region south central russia implications for paleozoic paleogeography of the mongol okhotsk ocean we present a reconnaissance paleomagnetic study of rocks from several formations of the chita region of south central russia representative location 51 n 116 e within the mongol okhotsk collision zone sections of siltstone and fine grained sandstone dated using fossils as bashkirian to moscovian epochs ussr carboniferous system middle carboniferous early permian late permian and triassic in age were sampled the resulting collection from five stratigraphic sections is a total of 319 oriented samples from 51 sites generally 5 to 10 samples per site were collected sample orientation was determined using both magnetic and sun shadow azimuths all paleomagnetic measurements were completed in the paleomagnetic laboratory at the university of pittsburgh using a 3 component 2g superconducting rock magnetometer srm in a magnetically shielded room thermal demagnetization was completed using between 12 to 20 heating steps up to temperatures of 685 c principal component analysis of the demagnetization data was successful in isolating two characteristic remanent magnetizations the lower unblocking temperature component component a fails the fold test is always of downward directed magnetic inclination and may record the present day earth s pdf magnetic field pdf i 69 4 d 351 8 component a ig 65 1 dg 356 5 95 6 2 n sites 50 the higher unblocking temperature magnetic component b was observed in the triassic bt n 3 late permian blp n 14 early permian bep n 5 and bashkirian to moscovian epochs of the late carboniferous bmc n 8 sections the b component differs significantly from component a and is recorded by sites of both downward and upward directed magnetic inclinations in the late permian and bashkirian to moscovian epoch sections component bmc and blp may represent primary remanent magnetizations the bashkirian to moscovian epochs of the late carboniferous mean paleolatitude is mc 19 9 14 8 and the late permian mean paleolatitude is lp 19 6 14 5 both are similar to that expected from reference paleomagnetic poles from the north china block but significantly different from paleolatitudes calculated using reference poles from the siberian or european plates we interpret the results of this study to suggest that the sampled sections were located near or associated with the north china block during their deposition

percolation of co2 rich fluids in a limestone sample evolution of hydraulic electrical chemical and structural properties percolation of co2 rich fluids in limestones causes the dissolution and eventual reprecipitation of calcium carbonate minerals which affect the rock microstructure and change the rock petrophysical properties i e hydraulic electrical and elastic properties in addition microstructural changes further feed back to affect the chemical reactions to better understand this coupled problem and to assess the possibility of geophysical monitoring we performed reactive percolation laboratory experiments on a well characterized carbonate sample 35 cm in length and 10 cm in diameter in a comprehensive study we present integrated measurements of aqueous chemistry ph calcium concentration and total alkalinity petrophysical properties permeability electrical formation factor and acoustic velocities and x ray tomography imaging the measured chemical and electrical parameters allowed rapid detection of the dissolution of calcite in the downstream fluid after circulating fluids of various salinities at 5ml min 1 for 32 days about 290 pore sample volumes at a pco2 of 1 atm ph 4 porosity increased by 7 from 0 29 to 0 31 permeability increased by 1 order of magnitude from 0 12 d to 0 97 d and the electrical formation factor decreased by 15 from 15 7 to 13 3 x ray microtomography revealed the creation of wormholes these along with the convex curvature of the permeability porosity relationship are consistent with a transport controlled dissolution regime for which advection processes are greater than diffusion processes confirming results from previous numerical studies this study shows that nonseismic geophysical techniques i e electrical measurements are promising for monitoring geochemical changes within the subsurface due to fluid rock interactions

constraining the intracontinental tectonics of the sw central asian orogenic belt by the early permian paleomagnetic pole for the turfan hami block in order to better understand the kinematics and geodynamics of the late paleozoic to early mesozoic transition from accretionary to intracontinental tectonics in the southwest central asian orogenic belt we performed a paleomagnetic study on lower permian strata in the turpan hami basin nw china magnetite and hematite are shown to be the principal magnetic remanence carriers a typical sedimentary fabric that has not been modified by postdepositional deformation is recognized via magnetic fabric study stable characteristic remanent magnetizations all of reverse magnetic polarity are revealed by step demagnetizations remanence age is determined to be of early permian affinity based on a fold test remanence behavior of minerals and geochronologic data with inclination shallowing corrections the first early permian paleomagnetic pole for the turpan hami block is acquired as 75 7 n 276 3 e a 95 5 7 and n 10 sites comparisons of this new pole with published ones from neighboring cratonic blocks provide kinematic constraints on the tectonic transition and subsequent intracontinental tectonics of this region the turpan hami and yili blocks have kept their relative positions since the early permian significant latitudinal movement of 14 7 7 2 occurred between the turpan hami and south junggar blocks and could be mainly accommodated by late paleozoic crustal shortening of at least 530 km across an intra arc basin in the bogda belt the turpan hami block has experienced large magnitude relative rotations of 41 1 7 1 a nd 21 2 9 4 with respect to tarim and south junggar since the early permian respectively corresponding to dominant intracontinental tectonics characterized by large magnitude strike slip displacements along megashear zones

barium and molybdenum records in bivalve shells geochemical proxies for phytoplankton dynamics in coastal environments barium calcium and molybdenum calcium ratios were investigated in shells of the tropical scallop comptopallium radula three juvenile specimens were harvested alive in the southwest lagoon of new caledonia after a 1 year hydrological survey calcite samples representing a few hours of biomineralization were laser ablated along the maximal growth axis and analyzed for ba and mo content using an inductively coupled plasma mass spectrometer absolute dates of shell precipitation assigned on the basis of periodic formation of shell growth patterns led to the accurate reconstruction of ontogenetic variations of elemental ratios with subweekly resolution inter individual variability of ba ca and mo ca time series was low indicating an environmental control on the incorporation of these elements within shells both profiles were characterized by a background level punctuated by sharp peaks the ingestion of diatoms enriched in ba adsorbed on iron oxyhydroxides associated with the frustules is the most likely cause of the formation of ba ca peaks some contribution of diatom associated barite is also possible in every instance ba ca would possibly be a proxy for the timing and magnitude of diatom blooms among all the theories that could be advanced to explain the occurrence of mo ca peaks the most plausible appears to be the ingestion of phytoplankton cells grown upon no3 and therefore containing high levels of mo required for the activity of nitrate reductase if this is so then mo ca could be a new proxy for nitrate uptake by phytoplankton in coastal ecosystems helping to reconstruct the balance between new and regenerated production in paleoenvironments

ba ca ratios in shells of arctica islandica potential environmental proxy and crossdating tool abstract ba ca shell time series of marine bivalves typically show flat background levels which are interrupted by erratic sharp peaks evidence from the literature indicates that background ba ca shell ratios broadly reflect salinity conditions however the causes for the ba ca shell peaks are still controversial and widely debated although many researchers link these changes to primary productivity freshwater input or spawning events the most striking feature is that the ba ca shell peaks are highly synchronous in contemporaneous specimens from the same population for the first time we studied ba ca shell in mature and ontogenetically old up to 251 year old specimens of the long lived arctica islandica also we analyzed specimens from surface water and deeper water the typical pattern of low background and erratic peaks persisted throughout ontogeny however due to decreasing sampling resolution and greater time averaging in older slower growing shell portions the background ba ca shell values appeared to gradually increase with ontogenetic age whereas the peaks became attenuated and broader despite that ba ca shell maxima were still highly synchronous among contemporaneous specimens from the same locality and habitat confirming previous reports from short lived species computing of annual ba ca shell averages largely eliminated any bias introduced by time averaging and sampling resolution strongly elevated annual ba ca shell peaks in specimens from surface waters iceland faroe islands isle of man during the 1980s appear to coincide with an extreme primary productivity pulse recorded by remote sensing however due to the lack of in vivo experiments we cannot ultimately test a causal link between annual ba ca shell excursions and primary productivity we propose that ba ca shell time series specifically the highly synchronous ba ca shell peaks and annual ba ca shell values in contemporaneous specimens from the same locality can serve as a tool to verify crossdating and facilitate the construction of statistically robust growth increment width master chronologies long term environmental reconstructions based on bivalve shell growth chronologies can likely greatly benefit from this new technique

evaluation of direct hydrocarbon indicators through comparison of compressional and shear wave seismic data a case study of the myrnam gas field alberta shear waves differ from compressional waves in that their velocity is not significantly affected by changes in the fluid content of a rock because of this relationship a gas related compressional wave bright spot or direct hydrocarbon indicator will have no comparable shear wave anomaly in contrast a lithology related compressional wave anomaly will have a corresponding shear wave anomaly thus it is possible to use shear wave seismic data to evaluate compressional wave direct hydrocarbon indicators this case study presents data from myrnam alberta which exhibit the relationship between compressional and shear wave seismic data over a gas reservoir and a low velocity coal

middle cambrian to permian subduction related accretionary orogenesis of northern xinjiang nw china implications for the tectonic evolution of central asia abstract middle cambrian to permian subduction related records are widely distributed in northern xinjiang which can be grouped into the chinese altay east junggar eastern tien shan west junggar yili and tarim domains by integrating paleogeographic and geological data we suppose that the chinese altay east junggar eastern tien shan domain was more closely located to siberia while the west junggar and yili domains occupied an intermediate position near the kazakhstan block in the early paleozoic paleoasian ocean distribution of andean type magmatic arcs island arcs accretionary wedges ophiolitic slices and or microcontinents shows an archipelago paleogeography forming a huge accretionary active margin sequences the tarim domain was on the opposite side of the early paleozoic paleoasian ocean remaining passive margin these tectonic units drifted northwards and approached the southern active margin of the siberian craton in the late paleozoic leading to termination of the paleoasian ocean and formation of a complicated orogenic collage between siberian craton and the tarim block between the end permian and triassic these multiple accretion processes significantly contributed to the lateral growth of central asia

paleomagnetic results from late paleozoic dikes from the northwestern junggar block northwestern china abstract paleomagnetic data have been obtained from late paleozoic mafic and silicic dikes in northwestern junggar a triangular fragment of early to middle paleozoic trapped oceanic crust located between the kazakhstan tarim and siberian blocks discordance between the observed declination and expected declinations from tarim and kazakhstan suggests a 30 40 counterclockwise tectonic rotation of the sampling region relative to tarim and kazahkstan this rotation is attributed to post triassic thrust and strike slip faulting at face value there is a good agreement between the observed mean inclination and those expected from kazakhstan and tarim tectonic interpretation of this mean inclination is obscured by a large difference in inclination from two sampling localities a combination of geomagnetic secular variation and local tilt of fault block may cause this dispersion

junggar turfan and alakol basins as late permian to early triassic extensional structures in a sinistral shear zone in the altaid orogenic collage central asia the junggar turfan and alakol basins in northwestern china and kazakhstan formed as late permian to early triassic extensional structures in a broad sinistral shear zone between large strike slip faults that separate two main domains of the altaid orogenic collage this extension was in response to an inferred large l000 km sinistral motion of the east european craton with respect to the angaran craton during this time deformation associated with the formation of the basins was taken up in part by counter clockwise rotations of crustal blocks with respect to the altaid orogenic collage and to the angaran craton this event is the only important phase of extension in a region otherwise dominated by compressional tectonics throughout the phanerozoic the basement rocks of these basins formed by altaid subduction accretion through the latter half of the palaeozoic and the region was subsequently thrown into compression again during the mesozoic cimmeride and cenozoic alpide evolution

isotopic studies bearing on the tectonics of the west junggar region xinjiang china isotopic investigations from the hercynian age fold belt between the kazakhstan and siberian cratons in the west junggar region determine the timing of tectonic evolution and the petrogenesis of the granitic rocks of the region sphene from the leucogabbro phase of the tangbale ophiolite melange the oldest member of the ophiolite sequences in the fold belt yields an isotopic pb pb age of 523 2 7 2 ma zircon from a postcollision alkali granite yields slightly discordant isotopic u pb ages that indicate magma crystallization at 321 4 6 7 ma dating it in the lower carboniferous period radiometric dating thus documents a time span of circa 200 ma for igneous activity in the area petrogenetic studies were made to test whether precambrian crustal rocks might underlie the junggar sedimentary basin initial lead isotope ratios determined from potassium feldspars from five alkali granites show clear affinity with ratios from mid ocean ridge basalts in pb isotope correlation diagrams sm nd data from sphene and apatite from one of the granites yield an initial end t 6 1 the granite sources are depleted mantle rocks of oceanic affinity that show no involvement of recycled aged granitic crustal rocks

junggar basin northwest china trapped late paleozoic ocean abstract the junggar basin originated during the late paleozoic as either a remnant lower to mid paleozoic ocean basin or a mid carboniferous back arc intra or inter arc basin bounded by emergent volcanic arcs south of the siberian craton the retreating junggar sea left behind a regressive sedimentary section comprising at least 3 4 km of marine volcaniclastics in the southern junggar area sandstones deposited in the junggar basin since the devonian are exclusively volcaniclastic demonstrating that precambrian basement rocks have never been exposed in the basin and supporting the hypothesis that the junggar is underlain by oceanic crustal materials the mid carboniferous junggar ocean may have been a remnant ocean basin of early to mid paleozoic age or alternatively may have been an extending intra or inter arc basin formed behind an emergent volcanic arc in the northern turpan region subsequent strike slip deformation and the general sparsity of geologic and geophysical data from the junggar area make it difficult to distinguish between these models late early permian through triassic sediments of the junggar basin are exclusively non marine deposited in a flexurally subsiding foreland basin during initial uplift of the ancestral tian shan mountains the sedimentary section deposited during the late permian early triassic appears to be inconsistent with a proposed rifting episode during this period

statistical significance of the fold test in palaeomagnetism summary the significance of the change in direction dispersion on applying the fold test in palaeomagnetism is used as the criterion for deciding whether or not the fold test has statistical significance a set of tables is compiled which can be used for quick application of the test

late paleozoic paleomagnetic results from the junggar block northwestern china we have obtained middle carboniferous to permian paleomagnetic results from the junggar block in order to test its tectonic coherence and to reconstruct its late paleozoic position from hoboksar on the northwestern margin of junggar a paleomagnetic pole from basic silicic flows yields p 299 e p 70 n n 15 sites k a95 36 6 4 in the same general area a pole from lava flows plutons and as well as from remagnetized limestones sandstones is at p 350 e p 69 n n 26 site k a95 15 7 5 farther to the southwest in keramayi a pole from late paleozoic dike swarms lies at p 230 e p 80 n n 23 sites k a 95 16 7 8 in the southern margin near urumqi from sedimentary rocks and volcaniclastics of the middle to upper carboniferous qijiagou and aoertu formations a pole is produced at p 7 e p 72 n n 15 sites k a95 28 7 4 from the middle carboniferous liushugou formation and dike swarms intruding into the formation two poles are located at p 231 e p 69 n n 4 sites k a95 46 13 7 and p 172 e p 55 n n 7 sites k a95 17 15 1 respectively though reliabilities of these two poles are in question magnetic polarities of all the poles in our study are exclusively reversed based on positive fold tests and a baked contact test we believe that these magnetizations were acquired during the kiaman reversed interval 250 320 ma more accurate ages of the magnetizations cannot be resolved at present despite widely separate locations the pole positions are roughly located on a small circle segment around the junggar block similar inclinations suggest a coherent junggar block since permian time based on the results of this study and other published paleomagnetic data a mean middle carboniferous to permian paleomagnetic pole is calculated at p 329 e p 82 n n 6 poles k a95 26 13 4 recognition of late paleozoic apparent polar wander for junggar is obscured by a lack of detailed geochronologic data and possible relative horizontal rotations around vertical axis the paleolatitude for the southern junggar predicted by this pole is only 4 south of the present latitude difference exists between the mean pole from junggar and permian poles from other tectonic units in asia tarim siberia kazakhstan and north and south china indicating post permian relative motions at the boundary between tarim and junggar this motion is likely to have a left lateral sense

assessing the reproducibility and reliability of estuarine bivalve shells saxidomus giganteus for sea surface temperature reconstruction implications for paleoclimate studies studies using oxygen isotopes y 18 o of mollusk shells to determine paleotemperature need to assume water y 18 o values which could severely influence calculated temperatures we analyzed aragonitic shells of the butter clam saxidomus giganteus deshayes 1839 to determine the reproducibility of the isotopic signal between individuals and to assess how precisely temperature could be calculated given known salinity and temperature furthermore carbon isotopes are also investigated as an environmental proxy the abundance of well preserved s giganteus shells in archeological and geological deposits in northwestern north america makes them a particularly suitable species for paleoclimate studies seasonally resolved stable oxygen isotope profiles in three s giganteus shells collected from the same site in puget sound washington usa were well correlated 0 77br 2 b0 87 although there were differences up to 0 58x in high resolution y 18 o profiles of the three shells the difference between the average y 18 o of each shell was less than half of this 0 19x and half of what has been reported for between colony coral variability y 13 c profiles on the other hand were more complex with shell y 13 c being about 2 5x lower than expected equilibrium values however this roughly conforms to the idea that about 10 of the shell carbon originates from metabolic co2 both y 18 o and y 13 c indicate that s giganteus do not grow during periods of reduced salinity despite the excellent reproducibility of y 18 o between shells and the fact that salinity effects were duly considered calculated temperature still differed from instrumental temperature applying different salinity y 18 o water relationships to average shell y 18 o and considering salinity from the shell collection site and a nearby offshore station resulted in calculated average water temperatures ranging from 1 7 to 6 4 8c warmer than measured although we could not determine if s giganteus precipitate their shells in isotopic equilibrium we believe that the difficulty in predicting temperature arose from not being able to accurately determine

mg ca in fossil oyster shells as palaeotemperature proxy an example from the palaeogene of central asia fossil oyster shells are well suited to provide palaeotemperature proxies from geologic to seasonal timescales due to their ubiquitous occurrence from triassic to quaternary sediments the seasonal nature of their shell growth and their relative strong resistance to post mortem alteration however the common use to translate calcitic oxygen isotopes into palaeotemperatures is challenged by uncertainties in accounting for past seawater 18o especially in shallow coastal environment where oysters calcify in principle the mg ca ratio in oyster shells can provide an alternative palaeothermometer several studies provided temperature calibrations for this potential proxy based on modern species nevertheless their application to palaeo studies remains hitherto unexplored here we show that past temperature variability in seawater can be obtained from mg ca analyses from selected fossil oyster species and specimens high resolution mg ca profiles combined with 18o were obtained along 41 fossil oyster shells of seven different species from the palaeogene proto paratethys sea central asia found in similar as well as different depositional age and environments providing comparison suitable mg ca profiles defined by continuous cyclicity and reproducibility within one shell are found to be consistent for specimens of the same species but differ systematically between species implying a dominant species specific effect on the mg ca signal two species studied here ostrea turkostrea strictiplicata and sokolowia buhsii provide an excellent proxy for palaeoclimate reconstruction from china to europe in palaeogene marine sediments more generally the protocol developed here can be applied to identify other fossil oyster species suitable for palaeoclimate reconstructions

new paleomagnetic results from northern china collision and suturing with siberia and kazakhstan abstract we report new results from our paleomagnetic studies of the inner mongolia autonomous region in northeastern china and the xinjiang autonomous region in northwestern china primary magnetizations are isolated in tertiary cretaceous late jurassic and late permian rocks and secondary components of magnetization of late jurassic and recent ages are seen in strata of inner mongolia western junggar basin and part of the tarim block suffered widespread complete tectono thermal remagnetization at about 280 ma permian the paleomagnetic evidence suggests that the sampled areas in inner mongolia have been part of the north china block at least since late permian time and the junggar block collided with the tarim block by late permian time our own paleomagnetic results together with available data from other parts of eastern eurasia suggest a tectonic model in which kazakhstan europe and siberia collided with each other and formed the europe siberia kazakhstan plate eur sib kaz in late permian time to the east mongolia outer mongolia inner mongolia and the north china block were also wedged together forming the mongolia north china plate mon nc by this time these two composite continental plates were not a stable unit in the late permian the geometrical relationship of the paleomagnetic poles for these two plates suggests that collision initially occurred in the late permian near the western end 50 n 75 e of the southern siberian fold belt and progressed eastward as the mon nc plate rotated and clockwise about 117 relative to the eur sib kaz plate during the early mesozoic suturing and rotation were probably complete by the late jurassic significant relative motion between the tarim and siberia blocks continued from early triassic to late jurassic as tarim moved northeastward 1400 km relative to siberia

tectonic evolution of the west junggar region xinjiang china the west junggar region of northwestern china consists of a hercynian age fold belt occupying a late paleozoic zone of convergence between three major eurasian plates siberian tarim and kazakhstan the northern part of the west junggar area includes part of the irtysh zaysan fold belt that extends to the northwest into the ussr where it marks a broad boundary between the siberian and kazakhstan plates the central part of the west junggar area includes the southeastern extension of the chingiz tarbgatay early paleozoic island arc sequence the southern part of the west junggar area is truncated by the deep fundamental junggar alakol fault that has brought the yili microplate into juxtaposiition with the west junggar region in the vicinity of ebin nur lake to the east the junggar area is covered by sediments of the junggar basin paleogeographic reconstructions and geologic evidence indicates that these plates began converging in the middle carboniferous and by late carboniferous alkali granites began invading the imbricated leading edges of the coalescing plates paleomagnetic data reveals that the plates continued to move along strike slip faults bringing the tarim plate and yili microplate into their present positions sometime in the early mesozoic six separate ophiolite occurrences in the west junggar region are strongly tectonized and dismembered the tangbale ophiolite is considered to be late cambrian 508 20 ma and represents the earliest known oceanic crust in western china petrologic and chemical data indicate that the tangbale ophiolite represents a possible back arc or forearc tectonic setting situated close to a developing island arc the darbut ophiolite has been tectonized to a melange and is overlain by late devonian flysch ages of the radiolaria in the cherts associated with the pillow lavas indicate that it formed in the middle devonian other occurrences of ophiolite melange in the northern part of the west junggar region may be as young as late devonian these ophiolites record ocean crust formation in the early to middle paleozoic within the junggarian ocean and their present tectonic setting indicates continental accretion and imbrication shortly after their formation associated blueschist blocks in the ophiolite melange further supports the concept of imbrication brought about by b type subduction and associated obduction postcollisional alkali granites intrude the oceanic sequences of the west junggar region and are considered to represent melted lower crustal material lead isotopic systematics on feldspars from six separate granite plutons indicate ratios that could only be considered oceanic as far as the magmas are concerned the implications of this finding is that the junggar basin basement rocks in the north and west are probably oceanic evidence presented in this study shows a complex history for the development of the west junggar region major movements of consolidating plates in the late paleozoic followed by rejuvenation of these same zones of closure during the himalayan tectonic event of the late tertiary demonstrates that convergence zones and fold belts may respond to vertical and horizontal stress even after many million years of inactivity

the giant pacific oyster crassostrea gigas as a modern analog for fossil ostreoids isotopic ca o c and elemental mg ca sr ca mn ca proxies 1 modern analogs are an essential part of palaeoclimate studies because they provide the basis for the understanding of geochemical signatures of fossils ostreoids are common in many sedimentary sequences and because of their fast growth high temporal resolution sampling of past seasonal variability is possible here two shell structures of modern giant pacific oysters crassostrea gigas the chalky substance and foliate layers have been sampled for trace element distributions mg sr mn and stable isotope variability c o ca oxygen isotopes exhibit a clear seasonal signature mean carbon isotope values of different oysters agree within 0 1 but ontogenic variability is complicated by shell growth patterns and potential small vital effects the calcium isotope ratios are found to be constant throughout ontogeny within analytical precision at a value of 44 40ca 0 68 0 16 2 sd srm 915a which is consistent with other bivalve species calcium isotope ratios in oyster shell material might thus be a possible proxy for palaeo seawater calcium isotope ratios element ca ratios are significantly higher in the chalky substance than in the foliate layers and especially high sr ca and mn ca ratios are observed for the first growth season of the oysters mg ca ratios in the chalky substance show a negative correlation with 18o values compatible with a temperature dependence whereas this correlation is absent in the foliate layers seasonal changes of sr ca are controlled by metabolic processes whereas for mn ca an additional environmental control is evident

controls on magnesium manganese strontium and barium concentrations recorded in freshwater mussel shells from ohio abstract freshwater bivalve shells may record inter annual fluctuations in water chemistry which in turn may archive variations in solute load due to pollution or discharge events here using weekly surface water chemistry collected at two locations and shells of lampsilis cardium grown in the surface water we investigate if the mg ca mn ca sr ca and ba ca ratios measured at high resolution in the shells on an intra annual time scale consistently reflect the chemistry of the surface water two relationships appear highly correlated sr cacarb and sr cawater and mn cacarb and temperature ba cacarb correlated strongly with ba cawater in one shell but temperature in another shell yielding inconclusive results mn cacarb and mg cacarb were not strongly correlated with elemental ratios in the water but mn cacarb did show variable weak to moderate correlation with ph we found consistent partition coefficient dme values between individual shell samples grown in the same water with mean dmg 0 0006 dmn 17 dba 0 13 and dsr 0 176 sr cacarb and sr cawater exhibited the strongest most consistent correlation with partitioning coefficients that were consistent with published values suggesting sr cacarb can be used as a proxy for sr cawater in freshwater mussels

first triassic palaeomagnetic constraints from junggar nw china and their implications for the mesozoic tectonics in central asia northwestern china belts result from the palaeozoic collage of central asia and the subsequent reactivations due to far field effects of the mesozoic tibetan and the cenozoic himalayan collisions triassic is a crucial period to understand and decipher the tectonics related to these two episodes about 250 oriented palaeomagnetic cores from 43 sites were collected from six sections of upper permian to late triassic sandstone in south and west junggar northwestern china thermomagnetic irm and hysteresis measurements reveal magnetite as the main carrier of the magnetic remanence with minor hematite and maghemite stepwise thermal demagnetisation has generally isolated two components the low temperature component up to 300 350 c displays a direction consistent with the present day geomagnetic field the locality mean directions related to the high temperature component above 350 c were also calculated two out of six sections display intense viscous magnetisation and the occurrence of maghemite reveals a possible cenozoic chemical remagnetisation for these two localities for the other four localities we assume that the magnetisation is primary because 1 ams measurements reveal a primary fabric 2 there are local occurrences of antipodal polarities and 3 palaeolatitudes of tilt corrected poles are compatible with previous studies the consistency between the early triassic poles of west and south junggar indicates that junggar evolved as a rigid block only since early mesozoic the comparison of the late palaeozoic and the early mesozoic poles of junggar and those of siberia and tarim shows major rotations between the late permian and the late jurassic early cretaceous these periods of discrete rotations are characterized by strike slip faulting in tianshan and altai and they may correlate with the major episodes of coarse grained detrital sedimentation and uplift of the range especially the counter clockwise rotations of junggar relative to tarim and siberia which occurred between the early and the late triassic and between the late triassic and the late jurassic are accommodated by transpressive tectonics in the tianshan and the altai belts this reactivation is a far field effect of tibetan blocks diachronous collisions therefore these first triassic palaeomagnetic results from junggar infer that post carboniferous rotations were due to the combined effect of the post orogenic transcurrent movement and the mesozoic oblique reactivation

paleomagnetism and tectonics of the southern tarim basin northwestern china we report late carboniferous permian and early tertiary paleomagnetic data from the southern tarim basin prefolding magnetizations were isolated in each case the late carboniferous permian and early tertiary poles lie at 64 6 n 166 5 e a95 6 3 and 58 1 n 202 0 e a95 12 7 respectively the late jurassic to early tertiary j3 e1 paleolatitudes of tarim and several basins throughout central asia are similar yet significantly 10 to 20 shallower than those predicted by the eurasian apparent polar wander path resolving this discrepancy remains a major problem in asian paleomagnetism discordance of the late paleozoic poles from tarim and siberia suggest that tarim has rotated about 30 counterclockwise with respect to siberia since the permian where paleomagnetic samples of both late carboniferous to early triassic c3 t1 and j3 e1 ages were collected from the same area of tarim a great circle passes through the means of the poles and the sampling locality this suggests that 1 only a difference in inclination and not declination distinguishes the two data sets and 2 vertical axis block rotations of the c3 e1 strata occurred after e1 although based on data of lesser quality the mean early to middle jurassic j1 2 pole from tarim differs significantly from the eurasian reference pole requiring radical tectonic solutions to resolve them the tarim j1 2 pole is indistinguishable from both the mean j3 e1 and c3 t1 poles the similarity of all the poles and the analogous tectonic setting of present day central asia to that of the late paleozoic in eastern north america raises the question whether all the data from tarim are overprinted

primary carboniferous and permian paleomagnetic results from the yili block nw china and their implications on the geodynamic evolution of chinese tianshan belt in order to better understand the tectonic role of the yili block on the paleozoic evolution of the chinese tianshan belt we performed a primary paleomagnetic study on carboniferous and permian rocks from different areas in the yili block nw of china more than 320 sedimentary and volcanic samples were collected from 39 sites except for the ordovician samples showing a weak and unstable magnetic remanence the majority of this collection presents characteristic remanent magnetization carried by magnetite and hematite in the study area though positive fold test has been observed on the early carboniferous rocks a general remagnetization of these rocks has been identified and attributed to the late carboniferous magmatism moreover all early and late carboniferous samples from the interior of the yili block yield stable and coherent magnetic directions with exhaustively reverse magnetic polarity the late carboniferous c2 is considered as the magnetic remanence age since these rocks are covered or intruded by synchronous magmatic rocks of the yili arc which lasted until to 310 ma the c2 paleomagnetic pole is therefore calculated at 68 6 n 290 6 e with 95 6 4 and n 15 the late carboniferous rocks located close to a deformation zone present a consistentmagnetic inclination but significant different declination with respect to other areas and are suspected to have probably experienced a local rotation although no fold test can be performed due to the monoclinal bedding stable magnetic components are isolated from late permian p2 red beds in the interior of the yili block with also a solo reverse magnetic polarity the p2 paleomagnetic pole of the yili block has been therefore calculated from the characteristic remanent magnetization 79 7 n 172 0 e with 95 11 3 and n 5 keeping important uncertainties in mind comparisons of the c2 and p2 paleomagnetic poles of the yili block with available coeval poles of junggar tarim and siberia indicate 1 no significant relative motion between the yili and junggar blocks since the late carboniferous 2 no significant or weak latitudinal relative motion occurred since the late carboniferous among these blocks but 3 the 46 2 15 1 and the 31 6 15 1 counterclockwise rotations of the yili junggar blocks with respect to tarim and siberia took place during c2 to p2 these rotations are accommodated by the permian dextral strike slip faults along the northern and southern sides of tianshan belt and sinistral strike slip faulting along the erqishi fault of altay belt resulting in about 1000 km and 600 km lateral displacements in the tianshan and altay belts respectively

paleomagnetic study of late paleozoic rocks in the tacheng basin of west junggar nw china implications for the tectonic evolution of the western altaids abstract to better understand the tectonic evolution of west junggar in the western altaids we have conducted a combined paleomagnetic and geochronological study on late devonian d3 late carboniferous c2 and early permian p1 successions from the tacheng basin northwest of china both primary and secondary characteristic remanent magnetization components have been successfully isolated and yield three reliable paleomagnetic poles of c2 and late permian p2 ages the c2 and p2 poles reveal a significant clockwise rotation of 35 6 10 4 which is comparable to the rotation deduced in the western part of the chingiz range during the time interval c2 to p2 similar rotation patterns for the two units suggest that the chingiz west junggar has remained as a quasi rigid block by the p2 time and constituted the northeast limb of the kazakhstan orocline the differential rotation of ca 25 to 30 deduced between the northeast and middle limbs of the kazakhstan orocline further suggests that at least a part of the curvature of the balkhash arc was acquired during the c2 to p2 interval and was a continuation of the middle paleozoic oroclinal bending moreover the c2 poles for west junggar and the junggar block are significantly different while the p2 ones almost overlap supporting the view that final closure of the balkhash junggar ocean occurred during the c2 to p2 interval on the other hand a large scale counterclockwise rotation of ca 80 to 90 is observed in west junggar and junggar relative to the western part of the chingiz range since the p2 time and this rotation probably represents an important intra continental deformation within the western part of the altaids a reconstruction of the paleo asian ocean has been proposed in which the kazakhstan orocline was emphasized by using the paleomagnetic results and geological evidence

preliminary evaluation of potential stable isotope and trace element productivity proxies in the oyster crassostrea gigas abstract as most bivalve mollusks are filter feeders or deposit feeders predatory septibranchs poromyacea being the notable exception they are closely linked with the activity of primary producers perhaps this is nowhere more evident than in shallow water habitats influenced by seasonal phytoplankton blooms in these systems photoautotrophs are capable of changing the physical and chemical properties of the water column in turn clams ingest large quantities of phytoplankton and precipitate their shells in these chemically altered waters thus clam shells likely archive valuable information about phytoplankton dynamics in shallow water habitats to better understand this relationship we investigated geochemical records from two potential productivity proxy systems archived in shells of the oyster crassostrea gigas that live in the san francisco bay estuary california usa here we present multi year records of shell carbon isotope 13ccarb and barium calcium ba cacarb variation these archives are compared with records of environmental variation using oxygen isotopes 18ocarb as a temporal marker we also present high resolution 13ccarb 18ocarb and ba ca profiles associated with the 2003 spring phytoplankton bloom our results suggest that the prominent positive 13ccarb excursion present in shell material deposited in the spring of 2003 most likely reflects photosynthetic enrichment of the dissolved inorganic carbon pool calibration of stable isotopes with calculated chlorophyll a concentrations measured during the bloom suggests that our 13ccarb sample variation reflects phytoplankton abundance with 3 to 4 day resolution these findings highlight the potential utility of stable isotope records as tools for reconstructing patterns of primary productivity elevated ba ca values are recorded each year in the spring thus like stable isotope profiles ba ca profiles from these specimens demarcate individual years of shell growth and establish ontogenetic age low and high resolution ba ca profiles do not however correlate with the 2003 spring phytoplankton bloom casting doubt on the relationship between ba ca ratios and phytoplankton blooms although the ba ca peak timing loosely correlates with freshwater discharge events peak amplitude does not leaving the environmental cause trigger of these peaks unknown nevertheless the san francisco bay estuary seems like an ideal environment in which to further investigate the relationship between skeletal geochemical variation and patterns of primary productivity

a devonian paleomagnetic pole from red beds of the tarim block china the authors present new devonian paleomagnetic results from 59 sites in three stratigraphic sections exposed on the northwestern margin of the tarim block at one section 1 998 m of red sandstone is continuously exposed the other two sections can be correlated with the first on both magnetostratigraphic and lithologic grounds progressive thermal demagnetization reveals three characteristic magnetizations one is a late permian overprint which is isolated below 578c at sites near contacts with late permian dikes the other two components are approximately antipodal have a much higher unblocking temperature than the overprint and are directionally distinct from the late permian overprint they believe that these are characteristic devonian magnetizations within the continuous 1 998 m section results denote a 395 m reversed polarity zone overlying a 1 603 m normal polarity zone one reversed event is recorded at the base of the section a paleomagnetic pole calculated by averaging results from 47 normal and reversed sites lies at lambda sub p 16 5 degree n phi sub p 165 0 degree e k 25 and a sub 95 4 3 degree this pole is statistically distinct from a previously reported late devonian pole for tarim on the basis of field geologic and rock magnetic studies they believe that the previously reported pole in addition to results frommore one of their three sections reflects at least partial contamination in the form of a thermal overprint caused by late permian igneous activity an analysis of devonian to late carboniferous polar wander suggests that the tarim block was attached to a subducting plate and moved northward and rotated clockwise during the late paleozoic comparison of the devonian paleolatitudes of siberian kazakhstan tarim and south china blocks indicates that both the tarim and south china blocks were located in equatorial regions and were far south of the northern angaran plate siberia and kazakhstan less

an empirical relationship between thermal conductivity and elastic wave velocities in sandstone measurements in three samples of very clean quartz sandstone in the porosity range 4 16 under dry and 100 water saturated conditions show that p and s wave velocities are linearly correlated with thermal conductivity the experimental results agree with the theoretical relation between seismic velocities predicted by the kuster and toksoz model 1974 and thermal conductivity predicted by weighted geometric mean

paleomagnetic investigation of upper permian sediments in the south junggar basin china lacustrine organic rich mudstones of the upper permian lucaogou formation are a significant petroleum source bed throughout most of the junggar basin in northwest china and paleomagnetic data may provide insight into tectonic conditions prevalent during their deposition secondary magnetizations were removed from 180 samples from 29 sites within the south junggar basin characteristic magnetizations of these samples were either revealed directly during thermal demagnetization or were calculated from great circle trajectories the primary nature of the characteristic magnetization is attested to by a positive fold test by exclusively reversed magnetizations which are consistent with the mid carboniferous to late permian kiaman reversed interval for the geomagnetic field and by relatively low levels of thermal maturity found in the mudstones tectonically corrected remagnetization circles and direct observations combined give a steep direction i 61 9 d 163 0 k 17 n 78 specimens the steep mean inclination recorded within the lacustrine organic rich mudstones suggests that junggar was situated near its present day latitude during deposition of the mudstones in late permian times consistent with the marginal ocean basin origin for junggar that has been proposed based upon stratigraphic relationships our data suggest that junggar may always have been associated with the northern continents of laurasia initially as a pre permian marginal ocean basin north of the tethys and subsequently as a permian mesozoic and cenozoic nonmarine foreland basin

crustal scale thrusting and extension in the hercynian schwarzwald and vosges central europe the hercynian outcrop areas in the schwarzwald of sw germany and vosges of easternmost france consist from north to south of three major lithotectonic complexes very low to medium grade metamorphics of the saxothuringian belt the polymetamorphic central gneiss complex and the tectonic melange of the southern complex juxtaposition of these three complexes occurred by oblique convergent motions in early carboniferous time the saxothuringian belt is part of a major se dipping accretionary wedge that consists of lower paleozoic meta sedimentary and metaigneous rocks and superimposed upper devonian to lower carboniferous synorogenic volcanics and elastics the central gneiss complex consists of polymetamorphic paragneisses orthogneisses metabasites and meta ultramafics dipping to the nw the southern complex consists of an imbricated melange of north to nw dipping synorogenic elastics volcanics and blocks of ultramafics and gneissic basement the central gneiss complex cgc experienced pervasive hercynian low pressure high temperature metamorphisrn before it was emplaced against and thrust over the sedimentary and volcanic fill of the adjacent synorogenic basins this convergence 340 330 ma produced mylonitic cataclastic shear zones in the cgc the most significant shear zones are the se verging todtnau fault zone between the cgc and the southern complex and the nw verging lubine fault zone between the central gneiss complex and the rocks of the saxothuringian belt these two fault zones enclose a bivergent pop up of the polymetamorphic basement the todtnau fault zone probably extends for more than 100 km along strike and can be traced to a depth of 10 km by deep seismic reflection studies detachment probably occurred along a mid crustal zone of anatexis expressed by a domain of low seismic reflectivity between about 10 and 15 km crustal thickening during early carboniferous convergence led to an extensional phase of crustal reordering between about 330 and 280 ma that was accompanied by the massive rise of posttectonic granitic plutons from middle to high crustal levels simultaneous creation of a structural lamination in the refractory lower crust neglected the main convergent tectonic boundaries it produced a basin and range type lower crust and mantle crust transition in early permian time and involved a major advective input of heat

late paleozoic paleogeographic reconstruction of western central asia based upon paleomagnetic data and its geodynamic implications abstract carboniferous to permian volcanoclastic rocks have been collected from south junggar and west junggar primary magnetizations have been observed from the characteristic components of 10 sites of early permian p1 and late permian p2 red beds of south junggar area the 14 early carboniferous sites from west junggar mountains expose post folding secondary magnetizations and according to their spatial distribution 9 remagnetized sites are related to late carboniferous early permian granite emplacement whereas 5 sites are located at the vicinity of late permian mafic dykes two new paleomagnetic poles have been consequently calculated for the periods of p1 at 79 5 n 36 6 e and of p2 at 60 4 n 4 7 e with a95 of 6 8 and 5 4 respectively they yield two paleomagnetic poles at 65 3 n 329 7 e with a95 of 6 3 and 64 8 n 179 5 e with a95 of 6 9 respectively compilation of available data shows stationary and consistent poles for south junggar area during the carboniferous and permian whereas nw junggar underwent a significant anticlockwise rotation between the late carboniferous early permian and the late permian indicating that junggar was not a rigid block up to the end of the paleozoic west junggar and south junggar may have experienced contrasting tectonic evolutions comparisons of late paleozoic poles of central asia blocks show 1 counterclockwise rotation of west junggar with respect to siberia contrasting with the clockwise rotation of north kazakhstan with respect to siberia 2 no significant movements between west junggar north kazakhstan and siberia since late permian indicating that they were rigidly welded since that time and 3 anticlockwise rotations of tarim yili and south junggar with respect to the welded siberia kazakhstan west junggar block such rotations may have been accommodated by late permian to early triassic strike slip faults with an estimation of the displacements of 1570 280 km along the irtysh gornotsaev shear zone 410 380 km along the nikolaiev nalati tectonic line and 490 250 km along the chingiz alakol north tian shan fault since late permian time

paleomagnetic study of mesozoic continental sediments along the northern tien shan china and heterogeneous strain in central asia a paleomagnetic study of rocks from the northern foot of the tien shan and the southern border of the dzungar basin east of urumqi 44 2 n 86 0 e spanning ages from middle jurassic to early tertiary was carried out to constrain the tectonic evolution in central asia since mesozoic time five middle jurassic sites reveal a remagnetized direction close to the present earth field in geographic coordinates d 6 6 i 72 6 95 7 4 thirteen out of 17 upper jurassic and lower cretaceous sites yield a characteristic direction stratigraphic coordinates of d 12 7 i 48 6 95 5 5 nine of 16 upper cretaceous and lower tertiary sites provide a characteristic direction of d 12 5 i 51 3 95 6 9 the latter two directions pass fold and reversal tests the pole positions are close to each other and to the besse and courtillot 1989 1990 eurasian apparent polar wander path for ages ranging from 130 to 70 ma however the difference in paleolatitudes amounts to about 5 9 3 7 which could indicate significant continental shortening in the altai mountains and perhaps further north subsequent to india asia collision the pole positions from the dzungar basin are close to those found for the tarim li et al 1988a leading to an insignificant paleolatitude difference 3 0 6 9 but showing a larger difference in declination 8 6 8 7 these paleomagnetic results are compatible with a model of heterogeneous deformation in the western part of the collision zone between india and siberia a significant shortening in the altai a slight counterclockwise rotation of the dzungar block the westward increasing shortening in the tien shan with attendant clockwise rotation of the tarim block are all consistent with this model in which tibet the tien shan and the altai undergo differential strain along strike in a relay fashion with the total india siberia convergence remaining approximately constant

laboratory measurements of ultrasonic wave velocities in rocks from the campi flegrei volcanic system and their relation to other field data the campi flegrei caldera located near the city of naples italy has shown signs of unrest characterized by large ground deformation seismic activity and changes in the hydrothermal system since 1970 any attempt to model the processes giving rise to these phenomena requires some knowledge of the subsurface structure and of the physical properties of the rocks at depth in this study we report the results of laboratory measurements of ultrasonic compressional and shear wave velocities in rock samples cored in 4 different geothermal wells reaching a maximun depth of 3 km the wells are located in the san vito sv and mofete mf areas at about 3 km north and 4 km west respectively from the center of the caldera we selected 10 core samples 7 from the sv wells and 3 from the mf wells the attention being focused on the most important rock formations underneath campi flegrei and on the lower sections of the wells where data had been lacking the measurements involved the transmission of ultrasonic waves along three orthogonal directions through dry and water saturated rocks at room conditions the samples are only moderately anisotropic 13 for one sv sample and 8 for all the other samples wave velocities generally increase with the depth of the sample the range of velocities is 3 5 4 km s 1 for p waves and 1 5 2 9 km s 1 for s waves for the sv samples water saturation generally implies slightly larger 10 vp values and smaller 20 vs values as compared with dry velocities for the mf samples water saturation implies both higher vp and vs velocities up to 35 and 18 respectively these results may be explained by the different type of porosity of the sv samples vesicular and the mf samples fissurai the ultrasonic measurements on water saturated samples are slightly higher than the available in situ vp sonic measurements 25 for one sv sample and 15 for all the other samples these differences can be explained by velocity dispersion between ultrasonic and sonic frequencies and by the different pressure temperature conditions existing at depth

brittle deformation and damage induced seismic wave anisotropy in rocks summary we study the relations between rock fracturing non linear deformation and damage and stress induced anisotropy of seismic waves by comparing theoretical predictions of a damage rheology model to results of laboratory experiments with granite samples the employed damage model provides a generalization of hookean elasticity to a non linear continuum mechanics framework of cracked media incorporating degradation and recovery of the effective elastic properties along with gradual accumulation of irreversible deformation beyond the elastic regime the model assumes isotropic distribution of local microcracks expressed in terms of a scalar damage variable but the non linear elastic response caused by the opening closure and evolution of the internal cracks is predicted to lead to seismic wave anisotropy we develop relations between the seismic wave anisotropy internal rock damage and stress field and test the viscoelastic damage rheology against sets of laboratory experiments with cylindrical granite samples the observed data include measurements of stress and strain in three loading cycles culminating in a final macroscopic failure together with measured wave velocities along and perpendicular to the axis of the cylinder using a single set of parameters the model fits well the overall evolution of the axial and transversal stress strain relations as well as the anisotropic elastic wave velocities during all cycles from the onset of fracturing in the first cycle until the macroscopic failure in the final cycle

unraveling environmental histories from skeletal diaries advances in sclerochronology high resolution proxy archives from aquatic settings are essential to better understand processes and mechanisms of global change during the last decade it has become increasingly evident that calcified tissues of bivalve mollusks and cold water corals in particular can significantly increase our knowledge of seasonal to multi decadal paleoclimate and paleoenvironmental variability in the extratropical oceans and coastal marine settings daily tidal fortnightly and annual growth patterns of periodically formed skeletal hard parts provide a means to place the proxy record in a precise temporal context their extreme longevity coupled with the running similarity between growth increment time series of contemporaneous bivalves opens the possibility of constructing stacked chronologies covering centuries to millennia which provide information on decadal climate and environmental variability and magnitudes of climate variability through time a current major research focus is on how to translate geochemical properties of the skeletons into quantifiable environmental proxy data and how to eliminate the adverse influence of vital effects on the proxy records this special issue presents the most recent advances in the field of sclerochronology specifically calcified tissues of bivalve mollusks cold water corals and tropical shallow water corals the majority of the contributions deal with the potential reconstruction of temperature ph and productivity through the analysis of variable growth rates sr ca mg ca ba ca u ca li ca 13c 18o and 44 40ca four papers present composite chronologies of two long lived bivalve species and discuss inherent decadal climate variability and one study demonstrates that sclerochronology can shed light on socioeconomic patterns of past human populations as well as resource use and resource management by people

decoding the oxygen isotope signal for seasonal growth patterns in arctic bivalves abstract chemical and physical variations in skeletal structures of marine organisms can reflect environmental variability forming the basis for reconstructing the conditions in which the organism lived the successful use of these bio archives for reconstructing seasonal environmental conditions is dependent on understanding intra annual growth patterns and timing of their deposition within skeletal structures we studied intra annual shell growth patterns as well as the timing and environmental processes associated with winter growth line deposition in two circumpolar bivalve mollusks serripes groenlandicus and ciliatocardium ciliatum shell growth deposited during a 1 year deployment on oceanographic moorings in kongsfjorden and rijpfjorden svalbard was analyzed in situ for 18 o values using high spatial resolution secondary ion mass spectrometry sims a new digital method was developed to measure the location of sims spots along chronologically deposited shell material dynamic time warping algorithms were adapted to align sims determined 18 o values with 18 o values predicted from continuous mooring instrument recordings of seawater temperature and salinity in order to derive intra annual shell growth models the resulting growth models indicated that the prominent winter growth band was formed during a slow shell growth period lasting from december until may in kongsfjorden and from november until mid june in rijpfjorden the length of the slow growth period was most likely controlled by food availability shell growth rate during the growing season was significantly explained by temperature marginal r 2 0 29 p

the triassic of the thakkhola nepal ii paleolatitudes and comparison with other eastern tethyan margins of gondwana during the triassic the thakkhola region of the nepal himalaya was part of the broad continental shelf of gondwana facing a wide eastern tethys ocean this margin was continuous from arabia to northwest australia and spanned tropical and temperate latitudes a compilation of permian triassic and early jurassic paleomagnetic data from the reconstructed gondwana blocks indicates that the margin was progressively shifting northward into more tropical latitudes the thakkhola region was approximately 55 s during late permian 40 s during early triassic 30 s during middle triassic and 25 s during late triassic this paleolatitude change produced a general increase in the relative importance of carbonate deposition through the triassic on the himalaya and australian margins regional tectonics were important in governing local subsidence rates and influx of terrigenous clastics to these gondwana margins but eustatic sea level changes provide a regional and global correlation of major marine transgressions prograding margin deposits and shallowing upward successions a general mega cycle characterizes the triassic beginning with a major transgression at the base of the triassic followed by a general shallowing upward of facies during middle and late triassic and climaxing with a regression in the latest triassic

inter annual climate variability in europe during the oligocene icehouse abstract new sclerochronological data suggest that a variability comparable to the north atlantic oscillation nao was already present during the middle oligocene about 20 myr earlier than formerly assumed annual increment width data of long lived marine bivalves of oligocene 30 25 ma strata from central europe revealed a distinct quasi decadal climate variability modulated on 2 12 mainly 3 7 year cycles as in many other modern bivalves these periodic changes in shell growth were most likely related to changes in primary productivity which in turn were coupled to atmospheric circulation patterns stable carbon isotope values of the shells 13 c shell further corroborated the link between shell growth and food availability sub decal oscillations in the 3 7 year band in other annually resolved fossil archives were often interpreted as el nino southern oscillation enso cycles this possibility is discussed in the present study however combined shell derived proxy and numerical climate model data lend support to the interpretation of a nao like variability according to numerical climate models winter sea level pressure wslp and precipitation rate wpr across central europe during the oligocene exhibited a pattern similar to the modern nao the simulated nao index for the oligocene shows periodicities coherent with those revealed by the proxy data 2 5 6 years yet on shorter wavelengths than the modern nao biennial and 6 10 year cycles likely the different paleogeography and elevated atmospheric co 2 concentrations not only influenced the sea level pressure pattern but also the temporal variability of the nao precursor the present study represents the first attempt to characterize the inter annual climate variability in central europe during the oligocene and sets the basis for future studies on the early phase of the cenozoic icehouse climate state

microcracks in rocks a review abstract in the past decade the number of studies about microcracks in rocks has rapidly increased this review of recent work concentrates on microcracks in rock as separate entities emphasizing microcrack morphogenesis kinematics dynamics population statistics and observational techniques cracks are produced when the local stress exceeds the local strength the local stress may be augmented by twin lamellae interactions kink bands and deformation lamellae stress concentrations at grain boundary contacts and around intracrystalline cavities local strength may be reduced along cleavage planes along grain boundaries and along any internal surface as a result of corrosion by chemically active fluids dislocations appear not to be a significant factor for crack nucleation below about 500 c in silicates spatial and temporal changes in temperature can also induce microcracking as a result of differential thermal expansion between grains with different thermoelastic moduli and thermal conductivities the amount of quartz in the rock has a significant effect on thermally induced microcracks because of its large and variable thermal expansivity the application of hydrostatic pressure between 100 and 200 mpa effectively closes most cracks but the closure may not be uniform if crack wall asperities exist hydrostatic pressure appears to stabilize cracks and make crack growth more difficult the number and average size of mechanically induced microcracks is greater in rock deformed at higher pressures the application of a deviatoric stress field on the boundaries of a rock mass results on a microscopic scale in a very complex stress system which greatly affects nucleation and propagation paths the relative amount of intragranular and intergranular cracking appears to depend upon mineralogy rock type and stress state the vast majority of stress induced microcracks in rocks appear to be extensional statistically they are predominantly oriented within 30 of the macroscopic maximum stress direction crack densities increase as macroscopic deviatoric stress increases above a threshold level crack size distributions may be either lognormal or exponential fracture in rock under compressive boundary loads is a result of the coalescence of many microcracks not the growth of a single crack some crack configurations are more favorable for coalescence than others as deviatoric stress increases and rock failure is approached the microcrack population changes spatially from random to locally intense zones of cracking away from the fault the crack density dies off rapidly to the background level a few grains away under lesser deviatoric stresses slow subcritical microcrack growth can occur as a result of stress aided corrosion at the crack tip the rate governing mechanism may be either the chemical reaction rate or the rate at which water can get to the crack tip important details still remain to be worked out

stratigraphy and facies development of the marine late devonian near the boulongour reservoir northwest xinjiang china late devonian to early carboniferous stratigraphic units within the zhulumute formation honggulelengformation stratotype hebukehe formation and the heishantou formation near the boulongourreservoir in northwestern xinjiang are fossil rich the hongguleleng and hebukehe formations are biostratigraphicallywell constrained by microfossils from the latest frasnian linguiformis to mid famenniantrachytera conodont biozones the hongguleleng formation 96 8 m is characterized by bioclastic argillaceouslimestones and marls the dominant facies intercalated with green spiculitic calcareous shales ityields abundant and highly diverse faunas of bryozoans brachiopods and crinoids with subordinatesolitary rugose corals ostracods trilobites conodonts and other fish teeth the succeeding hebukehe formation 95 7 m consists of siltstones mudstones arenites and intervals of bioclastic limestone e g blastoid hill and cherts with radiolarians a diverse ichnofauna phacopid trilobites echinoderms crinoids and blastoids together with brachiopods ostracods bryozoans and rare cephalopods have beencollected from this interval analysis of geochemical data microfacies and especially the distribution ofmarine organisms which are not described in detail here but used for facies analysis indicate a deepeningof the depositional environment at the boulongour reservoir section results presented here concernmainly the sedimentological and stratigraphical context of the investigated section additionally onelate devonian palaeo oceanic and biotic event the upper kellwasser event is recognized near the sectionbase