mid ocean ridge and island arc affinities in ophiolites from iran palaeographic implications complementary reference abstract fifty six samples of ophiolitic rocks from various late cretaceous eocene suture zones in iran have been analyzed for major and trace elements in order to assess their petrogenetic affinity and to determine their original tectonic setting in both southern baluchestan i e between the makran range and the lut block the fanuj maskutan sequence and northeastern baluchestan i e in the east iranian ranges the tchehel kureh sequence the ophiolitic complexes are well developed the rocks display affinities with mid ocean ridge tholeiites the basaltic rocks are comparable to respectively transitional fanuj maskutan and normal tchehel kureh morb in contrast the sequence along the zagros the sahneh sequence appears to have formed in an island arc setting in iranshar i e in southeastern baluchestan ophiolites are dismembered into a melange which includes cumulate intrusives similar to those from fanuj maskutan and lavas with island arc tholeiitic affinity a similar island arc origin may be inferred for the sabzevar ophiolitic sequence north of the lut block studied by other authors the chemical data thus help to elucidate the development of the jigsaw puzzle of microplates of gondwanian origin that during the mesozoic were intermediate in position between afro arabia india and eurasia and that now constitute the middle east ophiolite obduction in iran occurred during arc basin continent or ocean continent collisions in the late cretaceous early paleogene largely predating the final suturing between arabia and india with eurasia to which the intermediate microplates were already attached which did not take place before the neogene

tectonic evolution of a part of the tethyside orogenic collage the kargi massif northern turkey the central part of the rhodope pontide fragment one of the major tectonic units in turkey provides critical data for evaluating the cimmeride and alpide evolution of the mediterranean tethysides tectonic events that affected the central part of the rhodope pontide fragment since the end of the paleozoic generated east west trending belts with the event of every episode redeforming and partly obliterating the structures of previous episodes this evolution may be conveniently described in terms of three major episodes 1 two different realms of pre dogger oceanic rocks are present in the area the northern realm coincided with main branch of paleo tethys that was being actively destroyed by south dipping subduction the southern realm the karakaya ocean a back arc basin related to this subduction began opening by rifting of a retroarc carbonate platform during the permo triassic to the west a continental domain with sparse magmatism seperated the two oceanic areas toward the east the two oceans become united by the wedging out of the continental domain these two pre dogger oceans closed during the lias and their remnants were emplaced between the southern margin of laurasia and the fragments of the cimmerian continent 2 the second episode partly overlapped the first with rifting south of the cimmerian continent fragment during the lias this rifting was followed by a transgression which covered the ruins of the cimmeride orogenic belt by the malm this rifting concurrently led to the development of the northern branch of the neo tethys and a south facing atlantic type continental margin a southerly thickening sedimentary prism developed on this margin during the lias to early cretaceous interval 3 the floor of the northern branch of neo tethys began to be consumed along the north dipping subduction zone beneath the previosly constructed continental margin this convergent margin generated a magmatic arc to the north and to the south a subduction accretion complex present width of which approaches 80 km to the south of the subduction accretion complex yet another convergent margin is indicated by the presence of the remnants of an ensimatic arc the northern branch of the neo tethys was totally consumed in the late cretaceous to eocene interval

meso tethyan oceanic sutures and their deformation abstract on the basis of comparative stratigraphie and paleontologic analysis supported by some key paleomagnetic data and interpretations it is shown that during the mesozoic and the cenozoic the eurasian continent grew by accretion of microcontinents these microcontinents separated basins with oceanic crust from the main ocean during the late cretaceous and the early cenozoic the collision of the microcontinents with eurasia resulted in the closure of the basins and meso tethyan oceanic sutures originated in the region under consideration from the carpathians to tibet there are two main meso tethyan sutures the carpathian lesser caucasus and the afghan tibet suture the above mentioned main structures also had branches which remained as sutures of small basins the kamennopotock interpontide nain baft basins and others in the west carpathians the carpathian lesser caucasus suture is overlain by a widespread gemeric tatric allochton from the west carpathians the suture passes through the pannonian basin into the vardar ophiolite zone and farther to the ophiolites of the izmir ankara zone being displaced along the north anatolian right lateral strike slip fault the main suture passes from the eastern pontides into the lesser caucasus where it is marked by ophiolites of the amasia area the shirak bozum and zangezur ridges sunsequently it can be observed through the iranian qara dagh mountains to lake urumiyeh and the north anatolian strike slip fault being again shifted along the strike slip fault the carpathian lesser caucasus meso tethyan suture ends in the western zagros near the cenozoic neo tethyan suture the afghan tibet meso tethyan suture is situated in the pamirs in the rushan pshart zone the east prolongation of the suture has been displaced along the pamir karakorum right lateral strike slip fault in tibet west of the pamirs this suture is also displaced along strike slip faults and continues in the farahrud zone in afghanistan and than passes through the zabol baluch and daz murian ophiolite zones and approaches the neo tethyan suture the paleomagnetic data allow us to reconstruct the location of those sutures in the late cretaceous early cenozoic if one compares the present position of the carpathian lesser caucasus and afghan tibet meso tethyan sutures with the late cretaceous early cenozoic reconstructions of these sutures it is possible to trace the inner deformation of the alpine belt according to these data the carpathian lesser caucasus suture moved northwards over 1200 km ahead of the arabian turkish syntaxis with the displacement direction across the fold belt at the border of the dinarides and hellenides the displacement decreases to 400 500 km and its direction is along the fold belt the amplitude of the suture displacement increases in the pannonian region and again decreases towards the eastern alps the displacement of the afghan tibet suture was 2000 km during the alpine deformation a great ensemble of cenozoic nappes folds and structural arcs of the pamir punjab and arabian turkish syntaxes and carpathian loop is the result of lateral shortening of the alpine belt through the collision

new results and a palaeomagnetic overview of the pontides in northern turkey summary palaeomagnetic results are reported from 16 sites within volcanic and volcano sedimentary rocks of cretaceous and eocene age from the central pontides in northern turkey the sampled area is bounded by the north anatolian fault naf to the south and the black sea to the north the palaeomagnetic data collected demonstrate the presence of both non rotated and anticlockwise rotated regions i declination directions including lower upper cretaceous and eocene sites do not indicate any significant rotations north of where the naf exhibits an arcuate shape ii 20 anticlockwise rotation was observed in the sinop peninsula the northernmost extremity of the central pontides iii in the west of the central pontides two sites with normal and reversed antipodal directions indicate a 20 anticlockwise rotation and iv another region lies to the east of the study area and shows a rotation in an anticlockwise sense of about 5 30 the upper cretaceous and eocene directions reported in this paper and other palaeomagnetic studies show that there is not much difference between the inclination values of the upper cretaceous i 40 1 95 7 2 and the eocene sites i 39 6 95 8 1 furthermore the values of the inclination available from both sedimentary and volcanic upper jurassic lower cretaceous formations are shallower than the upper cretaceous ones this suggests that the entire pontides have undergone a northward drift of over 2000 km since the upper jurassic

the southern caspian a compressional depression floored by a trapped modified oceanic crust the south caspian intracontinental depression floored by oceanic basement is a relatively stable block with minor deformation surrounded by active fold thrust belts of arcuate form talesh alborz and kopeh dagh mountains which have undergone intense late cainozoic crustal shortening the basin is interpreted as a neogene quaternary compressional depression bounded by multi role mountain bordering reverse faults and apparently floored by a late paleozoic triassic or late mesozoic early tertiary modified oceanic crust trapped along an old geosuture it may be a relic of an old paleozoic triassic ocean or else a marginal sea developed behind a mesozoic paleogene ocean and analysis of geological and geophysical data enables a scheme to be suggested the general arcuate shape of the alborz and the talesh bordering mountain belts follows the pattern of the supposed rigid and thickened ocean crust of south caspian depression a tectono sedimentary study of the south caspian region coupled w

comparison of lignin phenols and branched isoprenoid tetraethers bit index as indices of terrestrial organic matter in doubtful sound fiordland new zealand abstract the branched isoprenoid tetraether bit index has recently been proposed as a qualitative proxy for the relative amounts of soil and marine derived organic matter om in marine sediments we compare bit values with lignin phenol cuo oxidation products and bulk om proxies in surface sediment samples from doubtful sound a fjord in the southwestern end of new zealand s south island as well as in soils and leaf litter from the local pristine temperate rainforest watershed the region has extreme rates of annual rainfall 7 m year 1 and large mass wasting soil and vegetation events on fjord slopes which results in relatively high fluxes of terrestrial organic matter om terr to fjord sediments sediments contained up to 11 4 w w organic carbon oc with terrestrial to a mixture of terrestrial marine 13 c 24 3 to 28 7 and c n 14 7 36 8 signatures bit values ranged from 0 24 to 0 93 lignin abundance in sediments reported as 8 values mg 8 lignin phenols 100 mg oc 1 ranged from 2 7 to 11 2 a weak correlation was found between concentrations of lignin phenols and bit values r 2 0 313 the likely cause of the differences between the two proxies is differences in the relative amounts of soil om om soil and vegetation intact and detrital transported to the fjord by episodic mass wasting events and gradual accumulation from overland leaching by rainfall and riverine sources interestingly the bit index correlated significantly with bulk sedimentary om om sed proxies 13 c r 2 0 774 c n r 2 0 629 while lignin phenol values 8 exhibited a much weaker correlation with 13 c values r 2 0 320 and no correlation with c n values r 2 0 005 this suggests that om soil represents the dominant fraction of om terr delivered to fjord sediments

sources sinks and subsidies terrestrial carbon storage in mid latitude fjords this work was supported by the natural environment research council grant number ne l501852 1 with additional support from the nerc life science mass spectrometry facility ceh l 098 11 2015 and the nerc geophysical equipment facility nggfsc minor loan 1031

block rotation by strike slip faulting structural and paleomagnetic evidence geometric analysis shows that motion of sets of strike slip faults should cause block rotation otherwise the distorted fault domain would not fit with its surrounding the sense of the block rotation depends on the sense of fault slip and the spacing and orientation of the faults all of which can be obtained from structural data the predictions of the geometric model can then be independently tested by paleomagnetic measurements the model was tested in northern israel structural data reveal several domains of contemporaneous right and left lateral strike slip faults paleomagnetic measurements show that in a domain of nnw trending left lateral faults blocks rotated 23 3 8 2 clockwise and in a domain of right lateral faults blocks rotated 22 4 9 0 anticlockwise these results are in agreement with the prediction of the geometric analysis of the structure the combined results of the heterogenous deformation of the area resembles a pure shear which allows n s extension by about 1 3 in other domains rotations of 34 6 9 1 and 53 1 11 0 were found in their original orientation the left and right lateral faults intersected at angles of 60 70 enclosing the principal axis of shortening in accordance with theories of brittle failure as a result of block rotations this angle is now larger and may reach 110 the results demonstrate large block rotations in different senses in domains of strike slip faults the independent structural and paleomagnetic data can be interpreted within the framework of a simple geometric model northern israel is considered to be a good model for this efficient mechanism of intraplate deformation which is expected to occur in similar tectonic settings elsewhere

origin of structural arcs of the carpathian balkan region burtman vs 1986 origin of structural arcs of the pat an balkan region in l p zonenshain editor tectonics of the eurasian fold belts tectonophysics 127 245 260 the late cretaceous reconstruction shows that the inner zones of the west east and south carpathians were adjacent to the dinarides and hellenides at that time forming together with them a linear fold system with bilateral vergence this fold system had a northwest strike in paleogene early miocene times the general deformation of the given part of the alpine belt took place it was caused by rotation of its asia minor balkan part relative to the more northern part of the belt this rotation 30 40 counter clockwise was accompanied by a shortening of the considered segment of the alpine belt by 30 hence exfoliation of the carpathian pontide and dinaric tauride branches of the alpine belt from each other and their disharmonious plastic deformation resulted in the formation of the aegean and tauride structural arcs and the carpathian structural loop during formation of the carpathian loop the gemeric tatric tectonic block moved northwards along the pemrinic oceanic substratum and rotated over 90 counter clockwise relative to the eastern alps

latest marine horizon north of qomolangma mt everest implications for closure of tethys seaway and collision tectonics the newly discovered marine horizon at zhepure syncline north of qomolangma revises timing of the closure of the eastern neo tethys seaway in the central himalayas the marine pengqu formation conformably overlies a lutetian shallow water carbonate platform and comprises shales interbedded with sandstones deposited in a neritic shelf environment the strata are dated by nannofossils and foraminifera as late early lutetian to late priabonian age np15 np20 deposited 47 34 ma indicating that the final closure of the tethys seaway in this region occurred at 34 ma the newly discovered strata provide evidence about emplacement of a major thrust sheet south of southern tibet prior to 37 ma which affected the regional climate

petrogenesis of the early eocene i type granites in west yingjiang sw yunnan and its implication for the eastern extension of the gangdese batholiths abstract this study reports new zircon u pb and hf isotopes and whole rock elemental and sr nd isotopic data for the gneissic granite and leucogranite from the nabang metamorphic zone yingjiang area west yunnan sw china the metamorphosed granitoids crystallized during the early eocene 55 50 ma with zircons showing ehf t values from 11 to 5 3 and crustal model ages of 1 5 to 0 42 ga comparable to those of coeval i type granitoids from the gangdese batholith southern lhasa the rocks are characterized by metaluminous and weakly peraluminous hornblende bearing gneissic granites with a cnk 0 95 1 09 na2o k2o coupled with low initial sr isotopic values of 0 7049 0 7070 and high end t values from 1 1 to 7 1 the rocks were derived from crustal materials involving ancient upper crust sedimentary and juvenile mantle derived rocks together with available data from nearby regions it is proposed that the early eocene granitoids in the nabang and tengliang area can be correlated to the gangdese granitoids and represent the southeastward continuation of the magmatic arc resulting from the neotethyan subduction in southern tibet the petrogenesis of early eocene granitoids in western yunnan was probably related to the rollback of the subducting neotethyan slab that caused the remelting of the crustal materials newly modified by the underplated basaltic magma

sources and distribution of terrigenous organic matter delivered by the atchafalaya river to sediments in the northern gulf of mexico abstract suspended sediments ss from the atchafalaya river ar and the mississippi river and surficial sediment samples from seven shallow cross shelf transects west of the ar in the northern gulf of mexico were examined using elemental oc c n isotopic 13c 14c and terrigenous biomarker analyses the organic matter om delivered by the ar is isotopically enriched 24 5 and relatively degraded suggesting that soil derived om with a c4 signature is the predominant om source for these ss the shelf sediments display oc values that generally decrease seaward within each transect and westward parallel to the coastline a strong terrigenous c n 29 signal is observed in sediments deposited close to the mouth of the river but values along the remainder of the shelf fall within a narrow range 8 13 with no apparent offshore trends depleted stable carbon isotope 13c values typical of c3 plant debris 27 are found near the river mouth and become more enriched 22 to 21 offshore the spatial distribution of lignin in shelf sediments mirrors that of oc with high lignin yields found inshore relative to that found offshore water depth 10 m the isotopic and biomarker data indicate that at least two types of terrigenous om are deposited within the study area relatively undegraded c3 plant debris is deposited close to the mouth of the ar whereas more degraded isotopically enriched soil derived om appears to be deposited along the remainder of the shelf an important input from marine carbon is found at the stations offshore from the 10 m isobath quantification of the terrigenous component of sedimentary om is complicated by the heterogeneous composition of the terrigenous end member a three end member mixing model is therefore required to more accurately evaluate the sources of om deposited in the study area the results of the mixing calculation indicate that terrigenous om soil derived om and vascular plant debris accounts for 79 of the om deposited as inshore sediments and 66 of om deposited as offshore sediments importantly the abundance of terrigenous om is 40 higher in inshore sediments and nearly 85 higher in offshore sediments than indicated by a two end member mixing model such a result highlights the need to reevaluate the inputs and cycling of soil derived om in the coastal ocean

an alternative isochron method for measuring cosmogenic 3he in lava flows this study evaluates an alternative isochron method designed to improve the precision and the accuracy of the measurement of cosmogenic 3he 3hec and the calibration of 3hec production rates in lava flows while the accuracy of the standard two steps routine i crushing ii melting may be affected by possible crushing induced release of matrix sited 3hec this new isochron technique does not involve the preliminary crushing step such advance is thus potentially able to improve the accuracy of 3hec determination moreover this method has the advantage to yield cosmogenic 3he concentrations using only one type of extraction technique cosmogenic 3he isochrons can be built successfully measuring the 3he and 4he concentrations of several phenocrysts replicates fused in vacuo provided that these aliquots have identical magmatic 3he 4he ratios identical 3hec concentrations and variable magmatic helium contents when plotted in the 3he 4he vs 1 4he space such a suite of data define a straight line whose intercept yield the magmatic 3he 4he mag ratio and whose slope is the cosmogenic 3he concentration the frequent addition of radiogenic 4he 4helow asterisk may be easily accounted taking advantage of a property that is characteristic of non eroded lava flows the 3hec 4helow asterisk ratio is not time dependent this radiogenic correction of the isochron slope involves the r factor whose calculation requires that the u and th abundances in the phenocrysts and the host lava be known as well as the diameter and the shape of the analyzed minerals this correction also requires that all the analyzed aliquots have identical radiogenic 4he concentration the isochron method was tested on surface samples of three quaternary basalt flows from mount etna and mauna loa aged of 6 1 8 2 0 1 and 41 3 ka the obtained data set yielded statistically robust isochrons and cosmogenic 3he concentrations that are not significantly different from those obtained with the standard method importantly for samples with high magmatic cosmogenic 3he ratio the isochron technique offers both better accuracy and precision than the standard two steps method this alternative technique should thus open new perspectives for the particularly important task of 3hec production rate calibrations from lava flow surfaces

timing aegean extension evidence from in situ u pb geochronology and cathodoluminescence imaging of granitoids from nw turkey abstract the biga peninsula of nw turkey hosts granitoid plutons that record the timing of extension in the aegean region here we focus on three plutons the kozak eybek and kestanbol and apply new methods to obtain a detailed tectonic history of their generation and exhumation in situ in thin section ion microprobe zircon geochronology and color cathodoluminescence cl imaging of zircon grains and whole thin sections show these granites experienced magma mixing brittle deformation and significant fluid rock interactions zircon ages range from the late eocene to late miocene with two ages from a single grain that are permian the late eocene early oligocene ages record the end stages of subduction during the closure of a branch of the neo tethyan ocean whereas late oligocene late miocene ages record the plutons extension and exhumation we present a model in which kozak eybek and kestanbol magmas were initially generated by fluid flux melting from dehydration of the subducting anatolide tauride block as evidenced by the late eocene to early oligocene ages late oligocene ages document the initiation of extension in the biga peninsula region and correlate to ages timing exhumation of the kazdag massif early miocene ages indicate continued aegean extension in the southern biga peninsula region at this time

sedimentary organic matter geochemistry of clayoquot sound vancouver island british columbia surface sediment samples from three interconnected fjords of clayoquot sound british columbia were density fractionated 1 6 g cm 3 to isolate discrete organic debris od from mineral associated organic matter mom total organic carbon oc values varied greatly ranging from 0 1 to 8 8 by weight with a general decreasing trend from fjord head to the continental shelf within the sediment terrestrial om was present either as vascular plant debris or soil mom down fjord the woody vascular plant material in the od fraction acquires nitrogen which is hypothesized to be due to the bacterial incorporation of nitrogen from the water terrestrial oc in the mom is incompletely replaced by marine oc within the fjords resulting in a 65 net loss of mom sediments deposited under oxic and intermittently anoxic water column conditions have organic carbon to surface area ratios oc sa ranging from 0 4 to 1 2 mg c m 2 similar to that of typical continental margin sediments given that temperate fjords contain an estimated 12 of the continental margin sediment deposited during the last 100 000 yr and that they bury at least a margin equivalent amount of oc either weight or surface area normalized we hypothesize that temperate fjords may contain 12 or more of the sedimentary oc buried during this time

the ophiolites of the tibetan geotraverses lhasa to golmud 1985 and lhasa to kathmandu 1986 ophiolite belts are found in tibet along the zangbo banggong and jinsha river sutures and in the anyemaqen mountains the eastern extension of the kunlun mountains where studied the zangbo suture ophiolites are characterized by apparently thin crustal sequences 3 3 5 km an abundance of sills and dykes throughout the crustal and uppermost mantle sequences common intraoceanic melanges and unconformities and an n morb petrological and geochemical composition the ophiolites probably formed within the main neo tethyan ocean and the unusual features may be due to proximity to ridge transform intersections rather than to genesis at very slow spreading ridges as the current consensus suggests the banggong suture ophiolites have a supra subduction zone petrological and geochemical composition although at least one locality in the ado massif shows morb characteristics however it is also apparent that the dykes and lavas show a regional chemical zonation from boninites and primitive island arc tholeiites in the south of the ophiolite belt through normal island arc tholeiites in the central belt to island arc tholeiites transitional to n morb in the north the ophiolites could represent fragments of a fore arc island arc back arc complex developed above a jurassic northward dipping subduction zone and emplaced in several stages during convergence of the lhasa and qiangtang terranes the ophiolites of the jinsha river suture have a n morb composition where analysed but more information is needed for a proper characterization the anyemaqen ophiolites where studied have a within plate tholeiite composition and may have originated at a passive margin it is not however certain whether true oceanic lithosphere as opposed to strongly attenuated continental lithosphere existed in this region

assessing the importance of terrestrial organic carbon in the chukchi and beaufort seas abstract the western arctic ocean is a unique part of the world s oceans and is an area undergoing significant climate changes the effects and possible climate feedbacks of these changes are not yet fully understood decreased sea ice cover could lead to increased productivity in the water column or a reduction in total productivity through the loss of sea ice algal contributions climate change could also alter the patterns of terrestrial inputs from rivers and coastal erosion in order to better understand the balance of organic material inputs in the western arctic ocean this report presents carbon and nitrogen elemental and isotopic compositions from 19 surface sediment samples and 7 cores from 4 shelf to basin transects as evidence of the sources of organic matter buried in the sediments of the chukchi and alaskan beaufort seas the c n ratios for surface sediments were between 5 3 and 11 5 mean 9 0 1 3 the mean toc was 1 2 0 3 and mean tn was 0 16 0 02 the highest toc contents were observed in the barrow canyon transect likely reflecting heightened overlying productivity the 13 c of this preserved material varied from 22 1 to 16 7 mean 19 4 1 3 a trend to depletion in 13 c and higher c n in eastern sites was observed among the surface samples 15 n varied from 4 1 to 7 6 mean 5 7 1 1 an evaluation of the inputs of organic matter to the western arctic sediment was accomplished using 13 c and 15 n values with the novel technique of a bayesian analysis multi source mixing model this model was used to estimate proportional contributions of sea ice algae water column phytoplankton and terrestrial organic matter we conclude that water column productivity is the source of between 50 and 70 of the organic carbon buried in this portion of the western arctic the remaining 25 35 of carbon is mainly supplied by sea ice algal productivity with at most 15 of sedimentary carbon derived from terrestrial inputs

origin and assembly of the tethyside orogenic collage at the expense of gondwana land abstract the tethysides are a superorogenic complex flanking the eurasian continent to the south and consisting of the cimmerides and alpides products of palaeo and neo tethys respectively we here review their evolution mainly on the basis of new maps showing the distribution of sutures magmatic rocks certain palaeobiogeographically and palaeoclimatologically significant taxa and facies and fragments of pan african 900 450 ma orogenic system forming the basement of many tethyside blocks these are supplemented by palaeomagnetic data reported in the literature a fundamental tenet of this paper is that major sutures which contain ophiolite fragments represent tectonic sections between continental blocks where oceanic crust has been subducted palaeo tethys came into existence largely in late carboniferous time coevally it began to be consumed by both internal and peripheral subduction zones which continued into the permian some of these had been inherited from pre tethyan times in the later permian rifting subparallel with the northern margin of gondwana land began between the zagros and malaysia separating a cimmerian continent from n gondwana land and thus heralding the opening of neo tethys and other smaller oceans that were back arc basins of palaeo tethys this rifting possibly also extended farther west into crete and mainland greece however the north china block yangtze block huanan block the eastern moity of the qangtang block north tibet and annamia all originally pieces of the end proterozoic early palaeozoic gondwana land had already separated from it in pre late carboniferous times possibly during the devonian all of these blocks and the cimmerian continent were characterized by cathaysian floral elements in late palaeozoic time palaeomagnetic and palaeontological data showing the original gondwana land affinity of these continental blocks are supplemented by correlating late proterozoic early palaeozoic pan african sutures orogenic belts and sedimentary basin fragments across tethyside sutures late permian foraminiferal provinces are related to this palaeogeographical interpretation by triassic times most cimmeride subduction zones were already in existence the cimmerian continent accelerated its separation from gondwana land and locally in the late permian began disintegrating internally along the waser rushan pshart banggong co nu jiang mandalay ocean by late triassic time all of the chinese blocks except lhasa and annamia had collided with each other and with laurasia the resulting enormous orogenic collage had a soft cushion between itself and laurasia in the form of the enormous accretionary complex of the songpan ganzi this connection enabled laurasian land vertebrates to reach south east asia by late triassic time in late triassic to middle jurassic times most major cimmeride collisions were completed widespread aridity in central asia occurred in late jurassic time probably in the rain shadow of the newly formed cimmeride mountain wall neo tethyan subduction systems formed along the s margin of the cimmerides or within neo tethyan oceanic lithosphere during the jurassic most if not all were north or east dipping they continued the northerly migration of the tethyside blocks evolution of the tethysides influenced the distribution of marine and terrestrial organisms and affected sea level changes and patterns of atmospheric circulation during much of the mesozoic and cainozoic it is likely to have reflected the surface expression of a persistent trend in the large scale convective circulation in the mantle that continuously transported material northward into the tethyan domain

deep seismic reflection waves and structure of the crust from dangxung to yadong on the xizang plateau tibet abstract in this paper we study the travel times velocities and spectral distributions of reflected waves generated by underwater explosions in lakes on the xizang plateau the crustal structure on both sides of the yarlung zangbo river has been estimated by the inverse solution known as damped least squares the depth of the moho is 70 73 km in the region north of the yarlung zangbo river the depth of the moho in the southern region is 68 45 km there is a low velocity 5 47 km s 1 layer in the crust and the crustal thickness decreases from north to south in the xizang plateau

preservation of elemental and isotopic source identification of sedimentary organic matter the amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation selective degradation modifies the character of the surviving small fraction of organic matter which becomes incorporated in bottom sediments organic matter alterations can continue to sub bottom depths of hundreds of meters corresponding to millions of years source and paleoenvironmental information nonetheless remains preserved in the molecular elemental and isotopic compositions of organic matter c n and 13c values of total organic matter in particular appear to retain paleoenvironmental information for multi myr time periods

lipid biomarker δ13c and plant macrofossil stratigraphy of a scottish montane peat bog over the last two millennia abstract seven horizons of a peat core covering the last 2000 years from moine mhor a blanket bog in the cairngorm mountains scotland have been examined for the carbon number distributions of the long chain hydrocarbon alcohol and acid components using gas chromatography gc and gas chromatography mass spectrometry gc ms compound specific 13 c values for individual n alkanes were obtained using gas chromatography isotope ratio mass spectrometry gc irms the lipid biomarker distributions and the 13 c values have been compared with those of eleven species of living plant dominant at the contemporary surface of the bog the observed lipid stratigraphy shows only partial agreement with that calculated using macrofossil abundance data and the lipid distributions for the living taxa a result which reflects the inherent uncertainties in both the lipid biomarker and the macrofossil approaches to palaeoenvironmental stratigraphy the carbon isotope values for the individual n alkanes of the plants 27 6 to 36 6 and of the peat layers 29 to 31 7 are as expected for the c 3 photosynthetic pathway however the n alkanes from the surface samples were more depleted by 2 in 13 c than those from the rest of the core a negative shift which may in part reflect the shift 1 2 in 13 c estimated for co 2 in a pre industrialised to an industrialised atmosphere

carbon cycling and burial in new zealand s fjords understanding carbon cycling in continental margin settings is critical for constraining the global carbon cycle here we apply a multiproxy geochemical approach to evaluate regional carbon cycle dynamics in six new zealand fjords using carbon and nitrogen concentrations and isotopes lipid biomarkers and redox sensitive element concentrations we show that the new zealand fjords have carbon rich surface sediments in basins that promote long term storage i e semirestricted basins with sediment accumulation rates of up to 4 mm yr 1 using 13c distributions to develop a mixing model we find that organic carbon in fjord sediments is well mixed from marine and terrestrial sources in down fjord gradients this is driven by high regional precipitation rates of 6 m yr 1 which promote carbon accumulation in fjord basins through terrestrial runoff in addition we have identified at least two euxinic subbasins based on uranium molybdenum iron and cadmium enrichment that contain 7 organic carbon because the strength and position of the southern hemisphere westerly winds control precipitation and fjord circulation carbon delivery and storage in the region are intimately linked to westerly wind variability we estimate that the fjord region 759 km2 may be exporting up to 1 4 107 kgc yr 1 outpacing other types of continental margins in rates of carbon burial by up to 3 orders of magnitude

eocene paleomagnetism of the caucasus southwest georgia oroclinal bending in the arabian syntaxis abstract the caucasus is very important for our understanding of tectonic evolution of the alpine belt but only a few reliable paleomagnetic results were reported from this region so far we studied a collection of more than 300 samples of middle eocene volcanics and volcano sedimentary rocks from 10 localities in the adjaro trialet tectonic zone atz in the western part of the caucasus stepwise thermal demagnetization isolates a characteristic remanent magnetization chrm in 19 sites out of 31 studied chrm reversed directions prevail and a few vectors of normal polarity are antipodal to the reversed ones after tilt correction the fold test is positive too and we consider the chrm primary analysis of tertiary declinations and strikes of alpine folds in the adjaro trialet zone and the pontides in northern turkey shows a large data scatter late cretaceous data from the same region however reveal good correlation between paleomagnetic and structural data combining late cretaceous and tertiary data indicates oroclinal bending of the alpine structures which are locally complicated with different deformation the overall mean tertiary inclination is slightly shallower than the reference eurasian inclination recalculated from one apparent polar wander path apwp but agrees with other this finding is in accord with geological evidence on moderate post eocene shortening across the caucasus we did not find any indication of long lived paleomagnetic anomalies such as to cenozoic anomalously shallow inclinations further to the east in central asia

lower and middle jurassic paleomagnetic results from the south lesser caucasus and the evolution of the mesozoic tethys ocean abstract we studied lower jurassic pliensbachian toarcian basalts and tuffs and middle jurassic bajocian limestones and marls from 9 sites in the southern part of the lesser caucasus ca 39 3 n 45 4 e a component showing rectilinear decay to the origin was reliably isolated from most volcanics this characteristic component reveals nearly antipodal directions for both polarities and passes the fold test the conglomerate test performed on lava boulders from the aalenian basal conglomerates is also positive we think that a primary remanence d 20 i 38 a 95 5 was isolated from the volcanics in contrast middle jurassic sediments yielded controversial results and the only reliably isolated intermediate temperature component itc does not pass the fold test the itc directions show a considerable improvement in data grouping during incremental unfolding with a maximum at 40 unfolding we argue however that the thus obtained mean direction does not correspond to any paleofield and is most probably an artefact when compared to reference data for the eurasian and african plates the lower jurassic mean inclination of 21 n 4 agrees well with the latter thus implying that in the early jurassic the area studied belonged to gondwana and was separated by the tethys ocean from eurasia in agreement with paleontological data we tried to locate the position of the boundary between the eurasian and gondwanian realms in the caucasus region in the early middle jurassic unfortunately the available jurassic paleomagnetic data from other tectonic units of the region did not reveal any clear pattern

paleogeographic and tectonic evolution of southern tibet since middle cretaceous time new paleomagnetic data and synthesis during the second french chinese paleomagnetic campaign in tibet in the summer of 1981 we sampled the middle cretaceous red beds of the takena formation and the cenozoic volcanics of the lingzizong formation a detailed analysis of about 400 specimens of red beds reveals a stable component of normal magnetization n in the north of the lhasa block north of the nyainqentanglha range and two stable components in the south lt ht where the red beds are more strongly folded and are unconformably overlain by the lingzizong volcanics all three components are carried by hematite blocking temperatures range from 400 to 600 c for lt and up to the neel temperature of hematite for both n and ht lt is shown to postdate part of the folding of the takena whereas n and ht both indicate a positive fold test at the 99 probability level in addition a small less than 10 of the natural remanent magnetization antiparallel component is superimposed in most samples and may be consistent with a model of long term acquisition of a chemical remanent magnetization for the red beds analysis of the volcanics reveals a single stable component with mixed polarities carried either by hematite or magnetite the paleomagnetic directions indicate that 1 the lhasa block stood at 12 5 3 n by upper cretaceous and at 13 5 6 5 n in the paleocene eocene thus confirming the limited displacement of the margin of eurasia between albian aptian deposition of the red beds and eocene onset of the india asia collision these values imply crustal shortening by as much as 1900 850 km north of the block since the upper cretaceous and by 1400 1200 km south of the block since the onset of the collision 2 southern tibet formed a single tectonic unit by middle cretaceous time and 3 differential rotations are observed within the block and are related to the collision these rotations are discussed in the frame of a recent propagating extrusion tectonics model this study confirms the close paleogeographic relationship between indochina khorat plateau and southern tibet prior to the india asia collision

geochemical expressions of anoxic conditions in nordasvannet a land locked fjord in western norway abstract the nordasvannet fjord in western norway is a modern semi enclosed basin suitable for studying sedimentary cycles as they occur under anoxic bottom conditions it is characterized by strongly anoxic conditions in the water column and bottom sediments diagenetic pyrite formation occurs in the sediments and syngenetic pyrite is formed in the lower water column organic matter burial in the fjord exceeds that of other environments with normal marine or upwelling conditions this is due to the better preservation of organic matter organic matter composition appears to have changed over time with higher fractions of terrigenous organic matter being present in the most recent sediments this may be a result of increased input of terrigenous organic matter possibly due to sewage supply to the fjord over the last decades organic c and caco3 contents of the sediments do not appear to reflect a productivity signal calcium carbonate content is influenced by chemogenic calcite formation biogenic opal content appears to reflect a productivity signal but different degrees of dissolution may obscure its clear recognition

eocene ostracods from southern tibet implications for the disappearance of neo tethys abstract the yadong area was located in the residual neo tethyan basin during the paleogene it contains a record of the youngest marine deposition in the tethyan himalayas therefore biostratigraphic data from this area are essential to constrain the timing of elimination of the tethyan ocean and the india asia collision ostracods are one of the most diverse groups of living crustaceans inhabiting marine non marine and even some semi terrestrial habitats they provide important evidence to reconstruct paleoenvironment and biogeography this investigation examined ostracod faunas recovered from the paleogene zhepure formation in the gulupu section tuna yadong southern tibet the formation can be further divided into a lower limestone member and an overlying shale member which are conformable abundant diverse well preserved marine ostracods were recovered from the shale member we report 29 species from 15 genera the stratigraphic distribution of the eocene ostracod assemblages found reveals three ostracod zones and shows strong affinity to sections previously investigated throughout the neo tethyan region the zhepure formation also yields diverse planktonic and benthic foraminifers charophytes nannofossils and pteropods and indicates that open marine conditions existed widely during the eocene based on this study of little known eocene ostracods we suggest that final closure of the tethyan seaway occurred after early late eocene

isotopic constraints of sedimentary inputs and organic carbon burial rates in the saguenay fjord quebec abstract the saguenay fjord quebec has exceptionally high sedimentation rates resulting in up to 100 m thick holocene sequences filling some of its basins partly due the frequent occurrence of rapidly deposited layers landslides seismic events floods in the present study special attention is paid on the incidence of such events on organic carbon oc fluxes sources and burial rates using physical sedimentological geochemical and isotopic measurements on 4 sediment cores raised from the inner basin of the fjord and the adjacent baie des ha ha in these cores rapidly deposited layers rdl include notably a turbidite linked to a major earthquake in 1663 a landslide layer dating from 1971 saint jean vianney landslide and a flood layer from 1996 compared with background sediments rdl are characterized by low oc contents 3 contents 2 and low 13 c values in oc 13 c oc values 26 8 0 2 and c n ratios 17 7 1 7 in the pre industrial pre 1663 fjord sediments indicate that most sedimentary organic matter om was then of terrigenous origin paper mill activity during the 20th century has resulted in om fluxes growing almost exponentially until the mid 1960s when major changes in industrial practices and the implementation of environmental regulations during the 1970s and later on reduced the amount of industrial om discharged into the fjord this industrial om shows an isotopic signature of 26 34 0 02 and c n ratios 20 not unlike those of the regional terrestrial om oc burial rates since the 1663 earthquake varied between 20 and 290 gc m 2 yr 1 rdl seem to favour oc preservation in the fjord by reducing bioturbation and both oxic and anoxic oc degradation and by contributing themselves to higher carbon burial rates therefore transitional environments such as the saguenay fjord could represent significant long term carbon sinks

high rates of organic carbon burial in fjord sediments globally fjords have been hypothesized to be hotspots of organic carbon burial a global compilation of organic carbon data and sedimentation rates shows that fjords sequester twice as much carbon as other ocean regions

paleomagnetism of cretaceous and paleogene sedimentary rocks from the kopet dagh and its tectonic implications abstract in the kopet dagh mountains the northernmost part of the alpine fold belt east of the caspian sea about 600 oriented samples from 21 sites were taken from the middle cretaceous through oligocene sedimentary series prefolding and most probably primary remanence were isolated in middle cretaceous terrigenous rocks and upper cretaceous paleocene limestones and marls after stepwise thermal cleaning only recent postfolding magnetization was found in eocene oligocene clays the middle cretaceous mean pole 75 n 153 e agrees well with that from extra alpine eurasia a strong negative correlation between paleomagnetic inclinations and clay content in the upper cretaceous paleocene sedimentary rocks is interpreted as arising from diagenetic compaction the limestones least affected by this process also yielded a paleopole 78 n 179 e closely matching the eurasian data the bends of fold axes in the kopet dagh are primary tectonic rotations are discovered only within the local wrench zone in the southwestern part of the region the close agreement of paleopoles from the kopet dagh and extra alpine eurasia suggests that these land masses have been welded together since the middle cretaceous