palaeomagnetic re investigation of early permian rift basalts from the baoshan block sw china constraints on the site of origin of the gondwana derived eastern cimmerian terranes a palaeomagnetic investigation was carried out on a series of rift basalts woniusi formation that accumulated on the baoshan block sw china in the early permian the aim being to provide quantitative palaeogeographical information on the eastern cimmerian terrane as it detached from eastern gondwana reliable data were obtained from four locations 28 individual cooling units and when combined with the findings of an earlier study three locations 19 sites indicate that breakup occurred at 41 9 s with errors 34 2 51 2 s using this information we fit baoshan against gondwana within a narrow longitudinal belt close to where northeast greater india and northwest australia were once in close proximity furthermore we suggest that sibumasu simao burma malyasia sumatra the largest of the eastern cimmerian blocks lay directly to the east offshore of australia qiangtang and lhasa almost certainly sat to the west off northern greater india se arabia but we are uncertain as to their exact configuration our findings are compared with several rather different models that have been published in recent years the new palaeomagnetic constraint highlights the flexibility authors currently have in reconstructing the region principally because of the overall lack of similar high quality data from the various blocks we explain how new data could resolve these ambiguities thereby offering more robust explanations for eastern gondwana s late palaeozoic development

paleomagnetism of upper cretaceous red beds from the eastern qiangtang block clockwise rotations and latitudinal translation during the india asia collision abstract high temperature magnetization component was isolated between 600 c and 680 c from upper cretaceous red beds in the mangkang area in the eastern end of the qiangtang block tibetan plateau the tilt corrected site mean direction is d s i s 51 3 56 1 with k 31 0 and 95 6 5 corresponding to a paleolatitude of 36 7 6 7 n positive fold and reversal tests indicate a primary magnetization inclination shallowing tests show that inclination bias is not present in the upper cretaceous red beds of the qiangtang block that might induce through depositional and or compaction process however previous paleomagnetic data obtained from cretaceous and paleocene eocene volcanic rocks show that the paleolatitudes of the lhasa block were 17 1 3 3 n and 22 3 4 4 n respectively and 28 7 3 7 n for the central qiangtang block yielded from eocene volcanic rocks these results show that there was a 10 latitudinal discrepancy between the lhasa block and qiangtang relative to eurasia however the mangkang area of the southeastern qiangtang block experienced 3 2 7 8 to 7 3 5 2 southward extrusion and 40 clockwise rotational movement relative to eurasia since the cretaceous which coincided with the early cenozoic rotational extrusion of the indochina and shan thai blocks the crustal deformation in the eastern qiangtang block should have been caused by the indian plate penetrating into eurasia in the eastern end of tibetan plateau and the formation of the eastern himalaya syntaxis since the oligocene miocene

paleomagnetic investigation of the early permian panjal traps of nw india regional tectonic implications abstract the 289 ma panjal traps of nw india kashmir are part of a series of rift related mafic suites abor sikkim etc that were erupted onto northern india present day coordinates around the same time as separation of the cimmerian blocks of qiangtang and sibumasu we report new data from only the second paleomagnetic investigation of this unit standard alternating field and thermal demagnetization methods were used to isolate characteristic magnetizations from seven outcrops at three locations within the kashmir valley nw india analysis of four sections 14 individual cooling units from close to srinagar that together form a tectonically coherent sequence spanning 3 km of stratigraphy yield a single component primary magnetization with a mean direction of dec 134 8 inc 55 3 95 8 9 k 21 0 an inclination only mean of 52 5 95 8 9 k 47 2 gives a paleolatitude of 33 s 5 a paleopole of 110 5 e 8 4 s a 95 10 7 is also calculated assuming the magnetization records a portion of the reverse polarity kiaman superchron the new result indicates extrusion of the panjal traps basalts at mid latitudes in the southern hemisphere by inference this constrains the location of central gondwana and informs debates related to cimmeria s detachment from gondwana

structure of the crust in the vicinity of the banggong nujiang suture in central tibet from indepth magnetotelluric data 1 magnetotelluric data from a 150 km long profile crossing the banggong nujiang suture bns central tibet acquired as part of the international deep profiling of tibet and the himalaya indepth project have been examined for crustal and upper mantle structure strike and dimensionality analyses demonstrate that regional scale electrical structures are two dimensional and oriented approximately parallel to surface geological strike as seen elsewhere in tibet the double thickness crust is generally characterized by resistive upper crust hundreds to thousands of ohm meters overlying conductive middle and lower crust tens to hundreds of ohm meters but in detail there are lateral variations at all levels regionally a northward transition from thick 45 km to thin 15 km resistive upper crust coincides with 1 the surface trace of the bns 2 a prominent strand of the karakorum jiali fault system 3 northward decrease in upper mantle seismic velocities and increase in attenuation and 4 pronounced northward onset of seismic polarization anisotropy the latter two seismological features have been taken to mark the northern limit of indian mantle lithosphere thrust beneath southern tibet on the basis of our electrical model we speculate that 1 the resistive upper crustal root beneath the neogene lunpola and duba basins was produced by crustal shortening localized along the northern edge of the lhasa terrane 2 the low midcrustal resistivity beneath the bns reflects enhanced neogene melting and or metamorphic dewatering of relatively fertile subduction zone complex rocks 3 observed steep upper crustal low resistivity anomalies are produced by hydrothermal fluids within active faults localized within and adjacent to the bns and 4 these strike slip and extensional fault arrays are surface manifestations of lithosphere penetrating shear localized along the northern edge of the underthrust indian plate

more than just nopcsa s transylvanian dinosaurs a look outside the haţeg basin abstract since the end of the 19th century the notorious palaeontologist baron nopcsa reported several late cretaceous small sized dinosaurs in the ha eg basin he explained their sizes as the consequence of unusual evolution on an island he named the ha eg island he found similar dinosaurs outside ha eg in other regions of transylvania near alba iulia or nearby jibou recent surveys carried out in these areas support nopcsa s presumptions even adding several new outcrops with dinosaur remains in s laj and cluj counties the dinosaur fossils are rather scarce but still obvious in the jibou formation in alba county the main outcrops are located between vurp r and ard on the right bank of the mures river but also between petresti and oarda de jos along the sebes valley the majority of the taxa from ha eg are also documented in these areas during the palaeogene and early miocene several of these mesozoic reptile bones were reworked to younger deposits another area with high potential for finding maastrichtian vertebrates is the rusca montan basin

shrimp zircon u pb geochronology geochemistry and sr nd hf isotopic compositions of a mafic dyke swarm in the qiangtang terrane northern tibet and geodynamic implications abstract regional mafic dyke swarms are commonly emplaced in extensional tectonic settings and are typically considered to be linked with continental break up a large number of mafic dykes areal extent of 40 000 km 2 have recently been documented in the middle of the qiangtang terrane northern tibet zircon u pb isotope analyses using a sensitive high resolution ion microprobe shrimp indicate that the dykes were emplaced in the early permian 279 2 ma 283 1 ma 285 1 ma and 285 3 ma whole rock geochemical data show that the qiangtang mafic dykes are tholeiitic in composition and exhibit relative enrichment in light rare earth element lree and depletion in nb ta and ti resembling continental intra plate basalts whole rock sr nd and zircon hf isotopic data suggest that mafic dyke magma was derived from a depleted mantle source e nd t 5 1 to 7 6 and e hf t 4 9 to 14 8 the chemical and isotopic characteristics make the mafic dykes similar to the panjal traps and permian basalts in the tethyan himalayas the contemporaneous and widespread emplacement of ca 283 ma continental intra plate basaltic rocks in the qiangtang terrane and in the himalayas is suggestive of a large igneous province lip this lip is linked to the initial rifting and opening of the meso tethys ocean during the permian

u pb monazite ages from the pakistan himalaya record pre himalayan ordovician orogeny and permian continental breakup the greater himalayan sequence in india and nepal records crustal thickening processes that took place during and following the onset of india asia collision ca 54 50 ma these resulted in late eocene early miocene kyanite and sillimanite grade regional metamorphism and oligocene miocene crustal anatexis which formed migmatites and leucogranites we present new u pb monazite data for kyanite and sillimanite grade gneisses of the neoproterozoic to cambrian tanawal formation in the pakistan himalaya which have metamorphic ages of 482 4 7 9 ma and 464 5 4 0 ma respectively these ages together with along strike equivalent rocks in the lesser himalaya of india and nepal help to define an ordovician orogeny the bhimpedian orogeny also called the kurgiakh orogeny spanning at least from 490 to 460 ma which followed neoproterozoic cambrian sedimentation and preceded late ordovician silurian postorogenic molasse deposition and development of a stable shelf margin at 460 440 ma these new ages for peak metamorphism of neoproterozoic rocks in the pakistan himalaya overlap with those of widespread s type granites that exist along the length of the lesser himalaya e g mansehra mandi and kathmandu granites greater himalaya e g nanga parbat kinnaur kailas and ama drime and in the north himalayan domes e g the tso morari kangmar and kampa domes thus based on stratigraphic metamorphic and u pb geochronological criteria we equate rocks of the tanawal formation gneisses to the lesser himalayan rocks to the east and rocks of the alpurai group to the higher himalaya our data also confirm that the lesser greater and tethyan himalaya are all part of a single contiguous plate staurolite grade schists from a higher structural level of the tanawal formation record u pb monazite ages of ca 272 267 ma indicating the occurrence of permian regional metamorphism in the area concomitant with major rifting and extrusion of the panjal trap volcanics

lhasa terrane in southern tibet came from australia the u pb age and hf isotope data on detrital zircons from paleozoic metasedimentary rocks in the lhasa terrane tibet defi ne a distinctive age population of ca 1170 ma with e hf t values identical to the coeval detrital zircons from western australia but those from the western qiangtang and tethyan himalaya terranes defi ne an age population of ca 950 ma with a similar e hf t range the ca 1170 ma detrital zircons in the lhasa terrane were most likely derived from the albany fraser belt in southwest australia whereas the ca 950 ma detrital zircons from both the western qiangtang and tethyan himalaya terranes might have been sourced from the high himalaya to the south such detrital zircon connections enable us to propose that the lhasa terrane is exotic to the tibetan plateau system and should no longer be considered as part of the qiangtang greater india tethyan himalaya continental margin system in the paleozoic reconstruction of the indian plate as current models show rather it should be placed at the northwestern margin of australia these results provide new constraints on the paleogeographic reconstruction and tectonic evolution of southern tibet and indicate that the lhasa terrane evolved as part of the late precambrian early paleozoic evolution as part of australia in a different paleogeographical setting than that of the qiangtang greater india tethyan himalaya system

the latest cretaceous fauna with dinosaurs and mammals from the haţeg basin a historical overview abstract research on the uppermost cretaceous continental deposits with dinosaur remains from the ha eg basin has behind it a history of more than 110 years the first studies were by franz nopcsa 1877 1933 who published between 1897 and 1929 a series of notes and papers on this fauna including five monographs dedicated to the ha eg dinosaurs nopcsa described 10 vertebrate taxa including dinosaurs crocodilians and turtles from the ha eg basin out of which 6 are still valid he recognized the primitiveness and the small size of most of the taxa from the ha eg palaeofauna characters that he related to the isolated island environment within which this fauna lived for a long time span after nopcsa systematic research on the ha eg fauna was interrupted for many decades being resumed after 1977 when d grigorescu leading a small group of students in geology started to explore the deposits outcropping along the sibisel valley near s npetru village from where nopcsa made most of his collection of fossil bones since then the fieldwork continued every summer until now numerous remains of dinosaurs crocodiles and turtles being unearthed the list of the maastrichtian fauna from ha eg currently includes 56 taxa from all vertebrate classes more than half of the recorded taxa were discovered in micropalaeontological samples through screen washing the most spectacular discoveries made after 1977 include a large variety of small theropods several sites with dinosaur egg clutches one of these also yielding hatchling remains one of the largest pterosaurs in the world representing a new genus and species hatzegopteryx thambema and several taxa of multituberculate mammals studies of the ha eg fauna were not restricted to systematic palaeontology but also covered all the fields that contribute together to an accurate reconstruction of the environment within which the maastrichtian fauna existed this overview includes a list of contributors to the actual knowledge on the ha eg fauna during the last 30 years divided by fields of scientific interest

new insights into the cenozoic lateral extrusion of crustal blocks on the southeastern edge of tibetan plateau evidence from paleomagnetic results from paleogene sedimentary strata of the baoshan terrane in order to characterize the lateral extrusion of crustal material during the cenozoic we conducted a paleomagnetic study of the eocene oligocene zhushan formation and paleocene muguahe formation in the central part of the baoshan terrane bst on the southeastern edge of tibetan plateau a primary magnetic component and a remagentized component with the miocene acquisition age were isolated from the muguahe formation and zhushan formation respectively these data indicate that the bst did not commence clockwise rotation in the period of the paleocene and the oligocene and that the bst experienced 80 clockwise rotation relative to east asia since the miocene combining with the documented history of crustal boundary strike slip faults on the southeastern edge of the tibetan plateau shows that the bst and tengchong terrane tct firstly underwent latitudinal crustal shortening in the oligocene and the eastward extension was the main type of motion of the crustal material during this period which induced the initial strike slip movement of their boundary faults since the miocene the main form of crustal motion of bst tct and simao terrane was gradually transformed into clockwise rotation which possibly indicates that the fold and thrusting fault systems induced crustal shortening and thickening in the southeastern edge of the tibetan plateau have reached extremity and the southeastern part of the tibetan plateau have already been uplifted to the similar elevation with today s elevation in the miocene

first report of lower permian basalts in south tibet tholeiitic magmatism during break up and incipient opening of neotethys abstract the neo tethys ocean began to form at early permian times when continental flood basalts were emplaced in various areas of the newly formed indian passive margin exposed today in the so called tibetan sedimentary zone of the himalaya lower permian mafic volcanic rocks which have long been known from various himalayan localities from kashmir to arunachal pradesh are here for the first time reported to occur also in south tibet bhote kosi basalts of the gyirong county the basalts unconformably overlie lowermost permian diamictites with locally intervening black shales and debris flow deposits and are followed in turn by chert bearing quartzarenites and silty to phosphatic marls yielding brachiopods of roadian wordian age the age of the lavas can thus be bracketed as late early permian post sakmarian and pre roadian the geochemistry of these subalkalic tholeiites akin to morbs testifies to their similarity not only with the adjacent nar tsum spilites of central nepal but also with the panjal traps and abor volcanics of the western and eastern himalayas respectively the geochemical signature of lower permian volcanic rocks is in fact uniform all along the himalayan range and markedly different from that of basaltic rhyolitic alkalic products sporadically emplaced during the previous rifting stage rift volcanism in the tethys himalaya began in the early carboniferous and came to an end in sakmarian times in the early permian initial submergence of the rift shoulders and sediment starvation were followed by tholeiitic magmatism which is therefore interpreted as following break up and incipient sea floor spreading in the neotethys ocean roughly contemporaneous emplacement of continental flood basalts of similar geochemical signature along a 2000 km long rift axis would in fact suggest extensive mantle melting at the transition from continental rifting to break up and opening of the neotethys between northern gondwana and the peri gondwanian blocks

albanerpetontid amphibians from the late cretaceous santonian of iharkut hungary with remarks on regional differences in late cretaceous laurasian amphibian assemblages since its discovery in 2000 the iharkut fossil locality in the upper cretaceous santonian csehbanya formation of western hungary has yielded a taxonomically diverse assemblage of terrestrial and freshwater vertebrates that continue to provide insights into the diversity paleobiogeography and paleoecology of late cretaceous vertebrates in europe albanerpetontidae an extinct group of superficially salamander like amphibians that were widespread across laurasia during the latter part of the mesozoic are represented at iharkut by 16 fragmentary jaws here we describe and figure these specimens as albanerpetontidae genus and species indeterminate based on the age of the iharkut locality several premaxillary features the known distribution late early cretaceous late pliocene of the type genus albanerpeton and an unusually large dentary specimen we suggest that the iharkut albanerpetontid may pertain to a previously unrecognized species of albanerpeton but verification of that must await the re

early and middle permian paleoclimates of the baoshan block western yunnan china insight from carbonates abstract in permian times the baoshan block of western yunnan southwest china formed the eastern part of the cimmerian continent most biogeographical and sedimentological data indicate that the early permian dingjiazhai formation formed on the block under conditions strongly influenced by the permo carboniferous glaciation after early permian rifting with post glaciation climatic amelioration and as the baoshan block drifted northwards to approach south china and indochina faunal elements characteristic of gondwana affinity decreased while those of cathaysian affinity increased finally late permian faunas are characterized by exclusively cathaysian elements this shift of marine provinciality becomes an important indicator in understanding the permian paleoclimatic evolution of the region this research investigated the composition of carbonate grain associations and the early diagenetic features of limestones from the upper part of the dingjiazhai formation and from the overlying yongde and shazipo formations a sharp distinction in petrological and diagenetic features is recognized between the dingjiazhai formation and the two overlying formations the dingjiazhai carbonates are characterized by the bryonoderm bryozoan echinoderm extended facies of the heterozoan association with no non skeletal grains because early diagenetic cement was rarely formed the dingjiazhai carbonates experienced strong diagenetic compaction in contrast the yongde and shazipo carbonates show a chloroforam facies of photozoan association with the common occurrence of non skeletal grains these carbonates were well cemented during early diagenetic processes from comparison with permian cool water carbonates from northern pangea and tasmania australia the dingjiazhai carbonates are interpreted as deposits of warm temperate conditions while the overlying carbonates are considered to be deposits of subtropical or tropical conditions this climatic interpretation based on the petrographic features of the permian carbonates agrees well with existing biogeographical data from the region

permian oolitic carbonates from the baoshan block in western yunnan china and their paleoclimatic and paleogeographic significance marine carbonate ooids are environment sensitive and hence valuable for paleoclimatic and paleogeographic reconstructions this paper describes permian ooids from the baoshan block in western yunnan china in order to offer a new means to refine the uncertain paleogeographic details of this gondwana derived block four major types of ooids micritic ooids compound ooids leached ooids and half moon ooids are documented from the hewanjie formation in the northern and the shazipo formation in the southern baoshan block these ooids are dated via biostratigraphic analysis to be wordian early wuchiapingian and signify an ameliorated shallow marine temperature for the guadalupian strata of the baoshan block results of this study coupled with literature data reveal diachronous debut of permian ooids among the gondwana derived blocks mostly sakmarian in central taurides of turkey central iran central pamir and karakorum block versus wordian capitanian in baoshan block peninsular thailand and south qiangtang in contrast asselian sakmarian strata of baoshan block as well as peninsular thailand and south qiangtang are characterized by glaciomarine diamictites these observations suggest that the baoshan block was probably situated at a considerably higher paleolatitude under distinct influence of gondwana glaciation during the asselian sakmarian than those blocks yielding sakmarian ooids moreover marine ooids are virtually absent nearby the equator within the permian tethys similar to the modern situation the baoshan block is accordingly interpreted to drift to warm water southern mid latitudes during the wordian capitanian and remain to the south of central iran karakorum block and south china which were equatorially located in the capitanian

south east asia as a part of an ordovician gondwanaland a palaeobiogeographic test of a tectonic hypothesis the hypothesis that thailand and malaysia the sibumasu block were adjacent to australia in the early palaeozoic has been tested by an examination of the ordovician sequences and faunas of sibumasu and australia the relatively stenogeographic nautiloids of the two areas are remarkably similar and have a simpson index of 0 92 at the generic level two new genera of discosorids are restricted to the two blocks andgeorgina andmesaktoceras are found elsewhere only in tibet very close affinities are also evident between the gastropod polyplacophoran and rostroconch molluscs the ordovician brachiopod faunas are also very close including the genusspanodonta other very close similarities are found between the upper cambrian trilobite faunas and the ordovician conodonts and stromatoporoids no ordovician faunas younger than upper whiterockian were found during this study in either northern australia or sibumasu and a stratigraphic gap probably exists from the upper whiterockian to the upper ordovician over most of the two blocks these remarkably close faunal similarities are good evidence in favour of the hypothesis that sibumasu was adjacent to australia during the early palaeozoic similarly close faunal relationships between north china south east asia tibet and australia may also suggest close proximity of those blocks during the early palaeozoic

magnetostratigraphic dating of the donggutuo and maliang paleolithic sites in the nihewan basin north china a detailed magnetostratigraphic investigation coupled with rock magnetic studies was carried out on a lacustrine sequence in the eastern nihewan basin northern china which contains the donggutuo and maliang paleolithic sites magnetite and hematite were identified as the main carriers for the characteristic remanent magnetizations magnetostratigraphic results show that the lacustrine sequence recorded the late matuyama and brunhes chrons furthermore the maliang artifact layer occurs just below the brunhes matuyama boundary and the donggutuo artifact layer is just below the jaramillo onset therefore the age of the maliang and donggutuo artifact layers can be definitely estimated to be about 0 78 myr and 1 1 myr respectively these two paleomagnetic ages coupled with previously obtained paleomagnetic data of the majuangou xiaochangliang banshan lantian and xihoudu paleolithic sites suggest an expansion and lengthy flourishing of human groups from northern to north central china during the entire early pleistocene

the permian fusulinoidean faunas of the sibumasu and baoshan blocks their implications for the paleogeographic and paleoclimatologic reconstruction of the cimmerian continent abstract permian fusulinoidean faunas occur in mainly four stratigraphic levels in the baoshan block of west yunnan and the sibumasu block of southeast asia which constituted part of the eastern cimmerian continent the oldest fauna from the upper part of the dingjiazhai formation in the baoshan block consists of pseudofusulina eoparafusulina and a new boultoniid genus and is assignable to the yakhtashian artinskian the second one which occurs in the basal part of the ratburi limestone and its equivalent strata in the sibumasu block is represented by monodiexodina and is probably referable to the bolorian kungurian the third fauna composed of eopolydiexodina rugososchwagerina yangchienia chusenella jinzhangia and several other genera is dated to the murgabian wordian and occurs in the lower part of the shazipo and daaozi formations in the baoshan block and the main part of the ratburi limestone in the sibumasu block the youngest fauna of probably dzhulfian wuchiapingian age is found in the upper part of the ratburi limestone and contains nanlingella reichelina codonofusiella and a few staffellid genera a smaller foraminiferal genus shanita found from the upper part of the ratburi limestone and the upper part of the shazipo formation is also an important element of the foraminiferal assemblage near the midian dzhulfian capitanian wuchiapingian boundary in the baoshan and sibumasu blocks in the eastern cimmerian continent low generic diversity throughout the permian and the paucity of tethys characterizing neoschwagerinid and verbeekinid genera during middle permian time are two remarkable features of the permian fusulinoidean faunas in the cimmerian continent the generic diversity of permian fusulinoidean faunas in space and time gradually increases from the early permian to late middle permian as well as from the eastern cimmerian areas to western ones the temporal increase of the generic diversity can be explained by the northward drift of the cimmerian continent during permian time in contrast the lower generic diversity of the eastern cimmerian permian fusulinoidean faunas against western ones is possibly due to an oblique arrangement of the continent to paleolatitude thus the western cimmerian continent was more proximal to the tropical tethyan domain than its eastern part in addition the middle permian cimmerian paleobiogeographic region is likely to be subdivided into two subregions the western tethyan cimmerian and the eastern gondwanan cimmerian based on the distribution pattern of verbeekinid and neoschwagerinid fusulinoideans and overall generic diversity the scarce occurrence or total absence of these essentially tethys indicating fusulinoideans in the baoshan and sibumasu blocks suggests that the eastern cimmerian continent was still far from the equatoro tropical cathaysian domain and was probably in a warm temperate or subtropical zone until the end of the permian the eastern cimmerian areas finally migrated into a tropical zone by the late triassic judging from well developed carnian sponge coral buildups in the chaiburi formation in the sibumasu block

middle permian plume related magmatism of the hawasina nappes and the arabian platform implications on the evolution of the neotethyan margin in oman 1 permian pillow basalts are commonly found in oman either at the base of the hawasina nappes or within the arabian platform successions exposed in the saih hatat tectonic window there is an ongoing debate on whether these lavas include normal mid oceanic ridge basalts nmorb witnessing the permian opening of the neotethys or if they are plume related magmas that are emplaced either on the arabian platform or on its thinned continental margin we sampled these lavas from several paleontologically dated middle permian sites four of them buday ah rustaq al ajal and wadi wasit are located within the hawasina nappes and are exposed as thrust slices overlain by the samail nappe and one wadi aday is within the arabian platform units and is exposed in the saih hatat window these lavas are associated with marine sediments deposited in environments ranging from proximal saih hatat wadi wasit and base of the thrust pile of al ajal to distal buday ah rustaq and top of the al ajal pile with respect to the arabian platform major and trace element features of the basalts allow two groups to be recognized enriched high ti basalts similar to alkali basalts from intracontinental traps rifted continental zones and oceanic islands are exposed in wadi aday wadi wasit and at the structural base of the al ajal pile moderately enriched to slightly depleted low ti tholeiitic basalt magmas resembling the low ti flood basalts and those from seaward dipping reflector sequences are represented in wadi al hulw in saih hatat buday ah rustaq and at the top of the al ajal thrust pile both groups show distinct plume related trace element signatures and they do not include typical nmorb although emplaced in shallow to deep submarine environments these basalts provide no direct evidence for a neotethyan seafloor spreading event in the hawasina basin instead they were likely erupted through the crust of the already rifted and drowned arabian continental margin thus despite their characteristic plume related geochemical signatures the middle permian basalts from oman were not likely emplaced during the evolution of a typical volcanic rifted margin we suggest that they originated from a mantle plume which ascended beneath the arabian passive margin well after the initiation of seafloor spreading of the neotethys

a tectonic model reconciling evidence for the collisions between india eurasia and intra oceanic arcs of the central eastern tethys abstract despite several decades of investigations inferences on the timing and nature of collisions along the mesozoic cenozoic eurasian margin remain controversial we assimilate geological and geophysical evidence into a plate tectonic model for the india eurasia collision that includes continuously closing topological plate polygons constructed from a time dependent network of evolving plate boundaries with synthetic plates constructed for now subducted ocean floor including back arc basins that formed on the southern eurasian margin our model is regionally constrained and self consistent incorporating geophysical data from abyssal plains offshore west australia and east antarctica including jurassic age data from offshore northwest australia limiting much of northern greater india to a 1000 km long indenter originally reaching to the wallaby zenith fracture zone southern eurasia and southeast asia are riddled with dismembered oceanic arcs indicating long lived tethyan intra oceanic subduction this intra oceanic subduction system was well established from cretaceous time in the india eurasia convergence zone in the neotethys which was consumed during greater india s northward trajectory towards eurasia from the early cretaceous fragments of obducted oceanic crust within the yarlung tsangpo suture zone between india and eurasia predominantly date to the late jurassic or mid cretaceous barremian aptian the various ophiolites along strike and a hiatus in subduction related magmatism during the tithonian aptian suggest that there was at least one generation of intra oceanic arc formation whose plate boundary configuration remains uncertain paleomagnetic and magmatic studies suggest that the intra oceanic arc was at equatorial latitudes during the early cretaceous before subduction resumed further north beneath the eurasian margin lhasa terrane with another hiatus in subduction related magmatism along southern lhasa during 80 65 ma possibly as the back arc spreading centre approached the active andean style margin in our model greater india collided with the tethyan intra oceanic arc in paleocene eocene time finally closing the tethyan seaway from mid late eocene time which is consistent with the age of the youngest marine deposits found between india and eurasia geological evidence from the collision zone indicates an age of initial arc continent collision by 52 ma followed by the soft initial continent continent collision between india and eurasia by 44 2 ma this timing is supported by marine geophysical data where the spreading centres in the indian ocean record a drastic decline in seafloor spreading rates and changes in spreading directions first at 52 ma followed by another reorganisation at 43 ma the abandonment of spreading in the wharton basin and the onset of extrusion tectonics in asia by 36 ma are likely indicators of hard complete continent collision and highlight the multi stage collisional history of this margin our continuously evolving network of mid ocean ridge and subduction zone geometries and divergence convergence vectors through time provide a basis for future refinements to assimilate new data and or test alternative tectonic scenarios

late permian to late triassic palaeomagnetic data from iran constraints on the migration of the iranian block through the tethyan ocean and initial destruction of pangaea summary a palaeomagnetic study of late permian to early jurassic rocks from the alborz and sanandaj sirjan zones in iran and a compilation of selected palaeopoles from the carboniferous to the present provide an updated history of the motion of the iranian block within the tethys ocean the iran assemblage part of gondwana during the palaeozoic rifted away by the end of the permian we ascertain the southernhemisphere palaeoposition of iran at that time using magnetostratigraphy and show that it was situated close to arabia near to its relative position today a northward transit of this block during the triassic is shown with an estimated expansion rate of the neotethyan ridge of 100 140 km myr 1 the northward convergence with respect to eurasia ended during the ladinian middle triassic and is marked by a collision in the northern hemisphere with the turan platform which was the southern margin of the eurasian continent at that time no north south component of shortening is evidenced north of iran afterwards an analysis of the declinations from the late permian to the present shows diverent large rotations emphasizing the important tectonic phases suvered since the triassic finally we propose palaeomagnetic reconstructions of the tethys area during the late permian and the late triassic showing that the palaeotethys ocean was narrower than previously thought and did not widen its gate to the panthalassa before the triassic period

petrogenesis and metallogenesis of the wajilitag and puchang fe ti oxide rich intrusive complexes northwestern tarim large igneous province abstract the wajilitag and puchang intrusive complexes of the tarim large igneous province tlip are associated with significant resources of fe ti oxide ores these two mafic ultramafic intrusions show differences in lithology and mineral chemistry clinopyroxenite and melagabbro are the dominant rock types in the wajilitag complex whereas the puchang complex is generally gabbroic and anorthositic in composition with minor plagioclase bearing clinopyroxenites in the marginal zone disseminated fe ti oxide ores are found in the wajilitag complex and closely associated with clinopyroxenites whereas the puchang complex hosts massive to disseminated fe ti oxide ores mainly within its gabbroic rocks the wajilitag intrusive rocks are characterized by a restricted range of initial 87sr 86sr ratios 0 7038 0 7048 and positive end t 0 04 3 01 indicating insignificant involvement of continental crustal contamination the slightly higher initial 87sr 86sr ratios 0 7039 0 7059 and lower end t values 1 05 2 35 of the puchang intrusive rocks also suggest that the isotopic characteristics was controlled primarily by their mantle source rather than by crustal contamination both complexes have sr nd isotopic compositions close the neighboring kimberlitic rocks and their hosted mantle xenoliths in the tlip this indicates that the ferrobasaltic parental magmas were most probably originated from partial melting of a metasomatized subcontinental lithospheric mantle modified recently with subduction related materials by the impingement of the ascending mantle plume the recycled subduction related materials preserved in the lithospheric mantle could play a key role in the formation of the parental fe rich magmas in the context of an overall lip system the distinct variations in mineral assemblage for each complex and modeled results indicated that the wajilitag and puchang complexes experienced different crystallization path fe ti oxides in wajilitag joined the liquidus earlier in the crystallization sequence especially relative to the crystallization of plagioclase this is attributed to the relatively high tfeo tio2 and initial h2o contents of the parental magma in combination with definitive field and petrological evidence the enrichment of highly incompatible elements e g zr hf nb and ta and the depletion of rare earth elements in the fe ti oxide ores is consistent with the plausible interpretation that the ores could be formed by fractional crystallization and crystal accumulation of the fe ti oxide crystals from the ferrobasaltic parental magmas a considerable amount of the fe ti oxides in the puchang has transported and sunk from higher up in the chamber to the underlying unconsolidated silicate crystal pile the highly dense fe ti oxide crystal slurries further tended to effective accumulate fe ti oxides to form high grade fe ti oxide ore bodies and subsequent rapid collapse and intrusive into lower lithologies within the complex under a h2o rich environment during the late stage of magmatic differentiation the development of massive fe ti oxide ores in the case of the puchang could plausibly result from a combination of the protracted differentiation history of a fe highly enriched parental magma and the later addition of external h2o from the country rocks e g carbonates to the slowly cooling magma chamber

afghanistan structure greater india concept and eastern tethys evolution abstract the large and complex area between central asia and the arabia india block includes from north to south the tien shan and hindu kush kun lun hercynian belts the turkman farah rud and tanghla shan neokimmerian belt the zagros makran baluch himalayan alpine belt and relics of corresponding oceanic spaces the angarian or gondwanian affinities of the different blocks separated by these successive peri indian belts are discussed an interpretation is proposed for the paleogeographic and structural evolution of this area from early paleozoic to present this interpretation is based on geologic and paleomagnetic data and on global tectonic considerations the hindu kush kun lun pre hercynian ocean probably separated laurasia from gondwanaland it was an early paleozoic tethys tethys 1 the tien shan ocean may have been a marginal basin for the hindu kush kun lun ocean the turkman farah rud tanghla shan pre neokimmerian ocean resulted from the break up of the gondwanaland margin its opening seems to have been related to the pre hercynian ocean closure resulting in the formation of a new tethys tethys 2 its subsequent closure may also have been related to the opening of the zagros baluch indus tsang po pre alpine ocean tethys 3 according to this interpretation eurasia appears to have increased from early paleozoic to cenozoic by successive accretion of cratonic blocks which came from the south through the tethys this evolution can be compared to the similar mediterranean evolution this interpretation is in agreement with the greater india concept however the northern border of greater india differs according to the stage of the gondwanaland evolution which is considered actually greatest india extended north to the caledonian belt and consequently has recorded the whole history of the eastern tethys

petrogenesis of the flood basalts from the early permian panjal traps kashmir india geochemical evidence for shallow melting of the mantle article i nfo the early permian panjal traps of northern india represent a significant eruption of volcanic rocks which occurred during the opening of the neotethys ocean basaltic basaltic andesites dacitic and rhyolitic rocks collected from guryal ravine and pahalgam show evidence for subaerial and subaqueous eruptions indicating that they are contemporaneous with the formation of a shallow marine basin the major and trace element geochemistry of the basalts is consistent with a within plate setting and there are basalts which have high ti tio2 n 2 0 wt and low ti tio2 b 1 8 wt compositions the high ti basalts are similar to oib whereas the low ti basalts are similar to continental tholeiites the identification of high and low ti basalts within the panjal traps is analogous to other large igneous provinces e g karoo deccan parana emeishan the sr nd isotopic values end t 5 3 to 1 3 isr 0 70432 to 0 71168 of both types of basalts overlap indicating that the rocks may have originated from the same ancient subcontinental lithospheric i e emii like mantle source tdm 2000 ma the two groups of basalts can be modeled by using a primitive mantle source and different degrees of partial melting where the high tirocksare producedby 1 partial melting of a spinel peridotite source where as the low ti rocks are produced by 8 partial melting trace elemental and isotope modeling indicatesthat some of the basalts assimilated 10 crustal material in contrast the basaltic andesites are likely formed by mixing be tween basaltic magmas and crustal melts which produced rocks with higher sio2 55 wt content and enriched isotopic signatures end t 6 1 isr 0 70992 the panjal trap volcanism was likely due to partial melting of the sclm within a passive extensional setting related to the rifting of cimmeria from gondwana contemporaneous volcanic and plutonic granitic rocks throughout the himalaya are probably not petrogenetically related but are likely part of the same regional tectonic regime

reconstruction of the deformed collision zone between india and asia by backward motion of lithospheric blocks 1 on the basis of a synthesis of tectonic data available on the india asia collision we present a first attempt to reconstruct the evolution of the collision zone assuming that the deformation of the lithosphere is localized along narrow shear zones and that the interiors of mantle blocks in between remain relatively undeformed we define block contours from the fault pattern and move back the blocks along their boundary faults along convergent or extensional boundaries the crust is assumed to shorten or stretch coherently step by step we go backward in time to finally reach the collision onset for each time step we find a solution compatible with the data set available and the position of the adjacent blocks for each block the search for compatibility at the scale of the entire collision zone allows for solving the kinematics of regions with fewer data and suggests plausible scenarios for regions where data is lacking for each step we calculate large scale displacement maps and determine euler poles for each block for the most recent time step the map proposed is compared to gps motions the deformation budget implies that extrusion absorbed 30 of the convergence between india and siberia during the entire collision span but varied with time accounting for as little as 3 or as much as 60 of this convergence at different epochs

a temporal link between the emeishan large igneous province sw china and the end guadalupian mass extinction abstract previous studies have suggested that there were two mass extinction events in the late permian one that occurred at the permo triassic p t boundary 251 ma and a second smaller mass extinction that occurred 5 8 myr earlier at the end of the guadalupian many workers have argued that there is a causal relationship between large scale volcanic activity and mass extinctions the major mass extinction event at the p t boundary coincides with the outpouring of huge quantities of lava that formed the siberian flood basalt province in russia courtillot et al earth planet sci lett 166 1999 177 195 and wignall earth sci rev 53 2001 1 33 suggested that the earlier late permian mass extinction coincided with the eruption of the lavas that formed the emeishan flood basalt efb province in sw china however the age of eruption of the efb lavas is poorly constrained using the sensitive high resolution ion microprobe to analyze zircons we have established the age of the xinjie intrusion believed to be a feeder to the main phase of efb volcanism to be 259 3 ma hence the formation of the efb is coincident with a proposed extinction event at 256 259 ma this result supports a temporal link between the emeishan large igneous province and the end guadalupian mass extinction

illawarra reversal the fingerprint of a superplume that triggered pangean breakup and the end guadalupian permian mass extinction abstract the permian magnetostratigraphic record demonstrates that a remarkable change in geomagnetism occurred in the late guadalupian middle permian ca 265 ma from the long term stable kiaman reverse superchron throughout the late carboniferous and early middle permian to the permian triassic mixed superchron with frequent polarity changes in the late permian and triassic this unique episode called the illawarra reversal probably reflects a significant change in the geodynamo in the outer core of the planet after a 50 million years of stable geomagnetism the illawarra reversal was likely led by the appearance of a thermal instability at the 2900 km deep core mantle boundary in connection with mantle superplume activity the illawarra reversal and the guadalupian lopingian boundary event record the significant transition processes from the paleozoic to mesozoic modern world one of the major global environmental changes in the phanerozoic occurred almost simultaneously in the latest guadalupian as recorded in 1 mass extinction 2 ocean redox change 3 sharp isotopic excursions c and sr 4 sea level drop and 5 plume related volcanism in addition to the claimed possible links between the above listed environmental changes and mantle superplume activity i propose here an extra explanation that a change in the core s geodynamo may have played an important role in determining the course of the earth s surface climate and biotic extinction evolution when a superplume is launched from the core mantle boundary the resultant thermal instability makes the geodynamo s dipole of the outer core unstable and lowers the geomagnetic intensity being modulated by the geo and heliomagnetism the galactic cosmic ray flux into the earth s atmosphere changes with time the more cosmic rays penetrate through the atmosphere the more clouds develop to increase the albedo thus enhancing cooling of the earth s surface the illawarra reversal the kamura cooling event and other unique geologic phenomena in the late guadalupian are all concordantly explained as consequences of the superplume activity that initially triggered the breakup of pangea the secular change in cosmic radiation may explain not only the extinction related global climatic changes in the end guadalupian but also the long term global warming cooling trend in earth s history in terms of cloud coverage over the planet

mineral magnetic properties of loess paleosol couplets of the central loess plateau of china over the last 1 2 myr 1 we have conducted a multiparameter investigation of 15 loess paleosol couplets s0 l1 to s14 l15 from the jiaodao section in the central loess plateau of china using environmental magnetic approaches coupled with soil science techniques the magnetic parameters display systematic variations that seem to be closely related to paleoclimate variations and intensity of pedogenesis high temperature susceptibility curves of paleosols show a generally decreasing trend in reversibility from the base of the lishi formation to the holocene black loam possibly indicating a decrease in weathering intensity this may reflect a long term increase in aridity and or a general long term cooling trend of the interior of the asian continent from 1 2 ma to the present several samples display wasp waisted hysteresis loops these are most pronounced in moderately enhanced paleosols less pronounced in the practically unaltered loess and subdued in the well developed paleosols but wasp waistedness reappears in the most developed paleosols this wasp waistedness sequence suggests that the composition concentration and grain size of magnetic minerals all contribute to the hysteresis behavior of samples from the studied loess paleosol sequence but each factor has a different effect at different stages of pedogenesis

geochronological geochemical and sr nd hf isotopic constraints on the petrogenesis of late cretaceous a type granites from the sibumasu block southern myanmar se asia abstract the late cretaceous to paleogene granitoids occur widespread in the sibumasu block within myanmar se asia which show a close association with tin tungsten mineralization however the precise timing petrogenesis and tectonic significance of these granitoids are poorly constrained so far in this study we present a detailed study on geochronology elemental and sr nd hf isotopic geochemistry for the hermyingyi and taungphila granites in southern myanmar with the aim of determining their petrogenesis and tectonic implications la icp ms u pb dating of zircon grains from the two granites yield ages of 69 70 ma indicating a late cretaceous magmatic event these granitic rocks are weakly peraluminous and belong to the high k calc alkaline series they are both characterized by high sio2 k2o na2o feot feot mgo and ga al ratios and low al2o3 cao mgo p2o5 and tio2 contents enriched in rb th u and y but depleted in ba sr p and eu suggesting an a type granite affinity moreover they display prominent tetrad ree patterns and non charac trace element behavior which are common in late magmatic differentiates with strong hydrothermal interaction or deuteric alteration the granites belong to a2 type and probably formed at a high temperature and anhydrous condition they have zircon ehf t values from 12 4 to 10 0 and whole rock end t values from 11 3 to 10 6 with paleoproterozoic tdm2 ages 1741 1922 ma for both hf and nd isotopes geochemical and isotopic data suggest that these a type granites were derived from partial melting of the paleoproterozoic continental crust dominated by metaigneous rocks with tonalitic to granodioritic compositions without significant input of mantle derived magma and followed by subsequent fractional crystallization by integrating all available data for the regional tectonic evolution in se asia and adjacent regions we attribute the formation of the late cretaceous a type granites to a back arc extension in the hinterland behind the subduction zone which is induced by the rollback of the flat neo tethyan subducting slab around ca 70 ma

palaeozoic and mesozoic tectonic evolution and palaeogeography of east asian crustal fragments the korean peninsula in context east and southeast asia comprises a complex assembly of allochthonous continental lithospheric crustal fragments terranes together with volcanic arcs and other terranes of oceanic and accretionary complex origins located at the zone of convergence between the eurasian indoaustralian and pacific plates the former wide separation of asian terranes is indicated by contrasting faunas and floras developed on adjacent terranes due to their prior geographic separation different palaeoclimates and biogeographic isolation the boundaries between asian terranes are marked by major geological discontinuities suture zones that represent former ocean basins that once separated them in some cases the ocean basins have been completely destroyed and terrane boundaries are marked by major fault zones in other cases remnants of the ocean basins and of subduction accretion complexes remain and provide valuable information on the tectonic history of the terranes the oceans that once separated them and timings of amalgamation and accretion the various allochthonous crustal fragments of east asia have been brought into close juxtaposition by geological convergent plate tectonic processes the gondwana derived east asia crustal fragments successively rifted and separated from the margin of eastern gondwana as three elongate continental slivers in the devonian early permian and late triassic late jurassic as these three continental slivers separated from gondwana three successive ocean basins the palaeo tethys meso tethys and cenotethys opened between these and gondwana asian terranes progressively sutured to one another during the palaeozoic to cenozoic south china and indochina probably amalgamated in the early carboniferous but alternative scenarios with collision in the permo triassic have been suggested the tarim terrane accreted to eurasia in the early permian the sibumasu and qiangtang terranes collided and sutured with simao indochina east malaya in the early middle triassic and the west sumatra terrane was transported westwards to a position outboard of sibumasu during this collisional process the permo triassic also saw the progressive collision between south and north china with possible extension of this collision being recognised in the korean peninsula culminating in the late triassic north china did not finally weld to asia until the late jurassic the lhasa and west burma terranes accreted to eurasia in the late jurassic early cretaceous and proto east and southeast asia had formed palaeogeographic reconstructions illustrating the evolution and assembly of asian crustal fragments during the phanerozoic are presented d 2005 international association for gondwana research published by elsevier b v all rights reserved

updating and reinterpreting the dinosaur track record of italy abstract the recently discovered and unexpectedly rich dinosaurian ichnological record of italy has proven to be integral to the paleogeographic understanding of the peri mediterranean area and is updated and refined herein through analysis of the stratigraphic spatial and geodynamic contexts of the entirety of the current ichnological dataset three distinct associations are recognized late triassic early jurassic late tithonian late cenomanian and coniacian maastrichtian while the first and last associations can be largely encompassed by pre existing models the late tithonian late cenomanian assemblage requires further investigation to account for the spatio temporal distribution of the ichnological evidence a model that invokes repeated dinosaur migrations from africa to the southern italian carbonate platforms up to the late cenomanian is needed at the end of this time interval a still poorly known extensional tectonic phase broke up adria causing the last dinosaur occurrence locally and requiring a re evaluation of the geodynamic models for this region

taphonomic modes in the maastrichtian continental deposits of the haţeg basin romania palaeoecological and palaeobiological inferences abstract the uppermost cretaceous continental deposits of the ha eg basin sw romania have yielded a high diversity vertebrate assemblage including the dwarf insular dinosaurs of nopcsa in 1902 franz nopcsa was the first to comment on the preservation patterns of vertebrate fossils suggesting that the most important fossil accumulations which he simply referred to as fossiliferous pockets were the result of the predatory activity of crocodilians crocodilian feeding grounds recent investigations of the fossil occurrences within the ha eg basin revealed a much wider range of taphonomic modes from microfossil bonebeds to isolated partially articulated skeletons than previously believed the survey of the vertebrate accumulation types and their sedimentary context documents a wide range of processes responsible for their genesis operating within a fluvial dominated upland setting study of the individual fossil accumulations yields important information on the palaeoecology composition of local biocenoses trophic interactions and palaeobiology social behaviour habitat preferences of the ha eg fossil assemblage

new paleomagnetic results of the early permian in the xainza area tibetan plateau and their paleogeographical implications abstract the characteristic remanent magnetizations chrms of the late paleozoic in the lhasa terrane reported previously were not widely used for paleogeographical reconstructions because the rocks have been obliterated significantly by multiphase orogeny this study reports the paleomagnetic data of 131 samples collected from 17 sites in the permian and the late triassic rocks from the zhakang section of the xainza area where the relative undeformed paleozoic strata were preserved consequently the chrms of high temperature with the different paleomagnetic directions were isolated from the permian sandstones limestones dolomites and the late triassic silicalites without the constraints with the spatial and temporal limitation of the chemical remagnetization derived from the fluids driven by the neogene strike slip faults and the paleogene thrusting faults in the study area the chrms carried by hematite in early permian sandstones away the faults have potentially preserved a primary magnetization which has a paleomagnetic direction of d 46 6 i 31 2 69 0 95 9 3 n 5 sites after tilt correction corresponding to a pole at 24 5 n 219 3 e with a95 7 8 the new corresponding paleomagnetic pole with the former carboniferous poles shows the lhasa terrane drifted into the middle lower latitude and isolated in the paleo tethys ocean rather than adjacent to the northern margin of gondwanaland during the early permian after being rifted from the australian continent in the late carboniferous

development of the khao khwang fold and thrust belt implications for the geodynamic setting of thailand and cambodia during the indosinian orogeny abstract the indosinian orogeny in thailand is often viewed as having developed between strongly linear terranes which today trend approximately n s the terranes were subsequently disrupted by later tectonics particularly nw se trending cenozoic strike slip faults the ene wsw to ne sw striking thrusts and folds in the khao khwang platform area of the saraburi group on the sw margin of the indochina terrane are not easily explained in the context of this traditional view reversal of the clockwise rotation shown to have affected the block north of the mae ping fault zone only enhances the e w orientation of structures in the fold and thrust belt and moves the belt further east towards cambodia one solution for the trend that fits better with regional understanding from hydrocarbon exploration of the khorat plateau is that the indochina terrane was actually a series of continental blocks separated by permian rifting during the early triassic the early stages of collision south china cathaysian terrane collision with vietnam indochina resulted in the amalgamation of disparate blocks that now form the indochina terrane by closure along the rifts at the same time or following on from the collision there was closure of the back arc area between indochina and the sukhothai zone the rift basins were thrusted and inverted during the early stages of the indosinian orogeny and only underwent minor reactivated when later sibumasu collided with sukhothai zone indochina terrane margin during the late triassic the scenario described above requires the presence of a minor e w trending suture in nw cambodia evidence for this suture is suggested by the presence of permo triassic calc alkaline volcanism

paleomagnetic results from the upper permian of the eastern qiangtang terrane of tibet and their tectonic implications abstract paleomagnetic samples were collected from red intercalations within the upper permian tuoba formation from the eastern qiangtang terrane of tibet progressive thermal demagnetization has revealed a prefolding possibly primary characteristic remanent magnetization chrm which yields a tilt corrected mean direction ofd i 25 2 6 7 95 8 6 the equatorial paleolatitude for the qiangtang terrane indicated by this result and the similarity of late permian fauna and flora shared by the qiangtang terrane and south china block scb suggest that the two terranes were in close proximity during the late permian a late permian paleogeographic reconstruction involving the major terranes of the present day east asia is constructed in which the songpan garze sea is surrounded by laurasia the north china block ncb the scb and the qiangtang terrane the permian development of the songpan garze sea appears to be related to the rifting of the qiangtang terrane off the scb its triassic evolution may resemble that of the solomon sea today in the southwestern pacific

geomagnetic secular variation in the cretaceous normal superchron and in the jurassic abstract it is now widely thought that geomagnetic polarity reversals occur spontaneously as a result of normal dynamo action rather than being externally triggered if this is the case then it may well be that periods of time in which the geomagnetic reversal frequency was dramatically different were characterised by different styles of secular variation two such periods were the cretaceous normal superchron cns 84 125 ma when the field was dominantly of a single polarity for 40 myr and the jurassic period 145 200 ma when reversals occurred at an average rate of as much as 4 6 myr 1 here we analyse a database of new and published palaeomagnetic directions from lavas emplaced during these periods in order to obtain first order descriptions of the palaeosecular variation psv during these times we then compare these records with one another and with that produced for the period 0 5 ma with average reversal frequency of 4 0 myr 1 our results are more equivocal than those obtained in a previous similar study mcfadden p l merrill r t mcelhinny m w lee s h 1991 reversals of the earths magnetic field and temporal variations of the dynamo families journal of geophysical research solid earth and planets 96 3923 3933 we demonstrate that this is probably a result of the previous study being affected by an artefact of their correction for within site scatter the usefulness of our jurassic record is severely limited by the restricted palaeolatitudinal span of the available data however our record for the cns is sufficient to allow us to conclude that it was likely that secular variation then was different from that in the 0 5 ma period this supports the hypothesis of a link between psv and reversal frequency and therefore endorses psv analysis as a first order tool for determining geomagnetic stability in the past

origin of the silicic volcanic rocks of the early permian panjal traps kashmir india abstract the panjal traps of kashmir india represent a significant outpouring of mafic and silicic volcanic rocks during the early permian and are synchronous with the opening of the neotethys ocean previous studies have suggested that the silicic volcanic rocks are derived by differentiation of mafic magmas dacites and rhyolites collected from the lower portions of the volcanic pile near pampore kashmir are peraluminous anck 1 0 in composition their calculated whole rock i sr values are variable i sr 0 69307 to 0 71825 and indicate open system behavior of either rb or sr or both whereas their nd isotope compositions end t 8 6 to 8 9 are nearly uniform the end t values and trace element th nb pm 4 nb u 8 ratios suggest the rocks are derived partially or wholly from the crust least squares and melts modeling indicate that the likely source of the silicic rocks is the middle crust rather than the lower or upper crust furthermore the silicic panjal traps have trace element compositions similar to some felsic volcanic rocks and a type granitic rocks from other large igneous provinces e g karoo parana and camp the paleoproterozoic t dm ages t dm 1836 to 1937 ma indicate that the rocks were likely derived from an ancient crustal source which experienced multiple episodes of recycling in contrast to silicic volcanic rocks from other lips the silicic panjal traps are unusual in that they did not involve mantle source material the heat required to melt the crust was likely due to the continuous injection of contemporaneous basaltic magmas which formed the majority of the mafic panjal traps

investigation of two elemental error sources in boat mounted acoustic doppler current profiler measurements by large eddy simulations measurements of water discharge and flow velocities in riverine and tidal environments are commonly made with acoustic doppler current profilers adcps mounted on a moving boat this paper presents results of high resolution large eddy simulations les conducted to investigate two elemental error sources in adcp measurements from a moving boat one of these errors is due to the flow disturbance induced by the boat mounted adcp the other error is due to the lack of flow homogeneity in horizontal layers assumed by the adcp algorithm to compute orthogonal velocities from the measured radial velocities along the acoustic beams the first error is investigated by comparing les results for an undisturbed flow field with les results for a flow field disturbed by a boat mounted adcp the second error is investigated by comparing the velocities beneath the adcp simulated by les with virtual adcp velocities which are obtained by applying the adcp algorithm to les velocities data mined along the path of the acoustic beams of the virtual profiler the distribution of the reynolds stresses beneath the adcp estimated with the adcp algorithm from the virtual adcp velocity data are also compared with those obtained from the les solutions for both the undisturbed and adcp disturbed flows results show that the boat significantly disturbs the flow field and that the disturbed flow field is qualitatively different from the flow fields observed around an isolated adcp no boat

climate changes caused by degassing of sediments during the emplacement of large igneous provinces most mass extinctions during the last 500 m y coincide with eruptions of large igneous provinces lips the cretaceous tertiary extinction was synchronous with the deccan flood volcanism the permian triassic extinction with the eruption of the enormous siberian traps and the end guadalupian extinction with the emeishan volcanic province the causal link remains disputed however and many lips apparently had no significant impact on the biosphere here we show that a key control on the destructive consequences of lip emplacement is the type of sedimentary rock in basins beneath the flood basalts contact metamorphism around intrusions in dolomite evaporite coal or organic rich shale generates large quantities of greenhouse and toxic gases co 2 ch 4 so 2 which subsequently vent to the atmosphere and cause global warming and mass extinctions the release of sediment derived gases had a far greater impact on the environment than the emission of magmatic gases

permo carboniferous sequences of gondwana affinity in southwest china and their paleogeographic implications abstract in southwest china permo carboniferous depositional sequences of gondwana affinity were first discovered in the himalayan region by the expedition team of acadimia sinica in 1975 by 1983 gondwana affinity permo carboniferous sequences had been identified also in the lhasa block the south qiangtang block in tibet and the tengchong and baoshan blocks in yunnan these sequences are characterised by the presence of successions which are interpreted as glacio marine deposits and by the presence of gondwana affinity biota the distribution of gondwana affinity permo carboniferous indicates that basins whose remnants are now represented by the yarlung zangbo suture and the bangong nujiang suture did not exist at that time and the vast area south of the lungmu shuanghu jinshajiang zone in tibet and west of the changning menglian belt in yunnan formed a part of the northern margin of gondwana

paleomagnetic constraints on the paleogeography of the east asian blocks during late paleozoic and early mesozoic times abstract although the axial and dominant geocentric character of the earth s magnetic field means that paleolongitude is indeterminate paleomagnetism is otherwise the only truly quantitative method available to the earth scientist for constraining paleogeography and reconstructing the kinematic evolution of continental blocks during the past half century numerous paleomagnetic results have provided substantial quantitative constraints on the origin and tectonic evolution of the major tectonic divisions now comprising eastern asian in this paper we first assess the available early paleozoic to early cretaceous paleomagnetic results from the south china north china and tarim blocks using internationally recognized reliability criteria we then construct a running mean through a 20 ma window by weighting the poles according to their q factors and fit a spherical spline with smoothing factor of 300 to derive apparent polar wander apw paths for these three major blocks during this early paleozoic to late mesozoic time interval together with late paleozoic to early mesozoic paleomagnetic poles from the qaidam qiangtang lhasa sibumasu indochina and some other smaller blocks terranes of east asia we produce a series of paleogeographic reconstructions for these major blocks and lesser terranes of east asia between mid ordovician and late jurassic times 460 160 ma which although based primarily upon paleomagnetic evidence aim to embrace the geological constraints finally we discuss the current evidence for closure times of the paleo asian mianlue and east paleo tethyan oceans which incorporate fundamental issues concerning the formation of the east asian continental collage and collision with the northern main body of the pangean supercontinent we use the collective evidence to argue that these major paleo oceans had closed by the late triassic and that the east asian sector of the supercontinent had united to become an integral part of pangea by that time 220 ma

catastrophic environmental transition at the permian triassic neo tethyan margin of gondwanaland geochemical isotopic and sedimentological evidence in the spiti valley india abstract interpreting global consequences of the permian triassic p tr extinction requires examination across paleogeographic realms of pangaea the spiti valley in india remnant of the peri gondwanan shelf preserved trails of this environmental catastrophe in the neo tethys ocean we document new sedimentological observations and high resolution trace element concentrations and carbon oxygen lead isotope data across the p tr boundary in spiti framboidal pyrites fossils and laminated lithology of the late permian shales indicate deeper anoxic depositional environment while 13 c org excursions of 2 4 and 3 1 in atargu and guling outcrops respectively identify the p tr transition across a clayey partly gypsiferous ferruginous layer sedimentological similarities of this layer to other neo tethyan sections from transcaucasia and iran indicate subaqueous oxidation of shallow marine sediments on a regional scale light rare earth element enriched late permian shales with conspicuous ce eu anomalies reflect their source from the adjacent panjal trap basalts ca 289 ma of kashmir continental crustal nb ta and zr hf anomalies appear at the p tr boundary sediments and prevail through the overlying early triassic carbonates original pb isotope ratios along with an increasing pb abundance closer to the p tr boundary distinguish the volcanic source of the late permian shales from the continental crustal siliciclastic signature of the early triassic carbonates our 13 c org trace element and pb isotope record from spiti indicate catastrophic changes in sediment sources and facies with effects on carbon cycle and are consistent with an abrupt episode of marine regression and erosional forcing also observed elsewhere along northern gondwanaland simultaneous eruption of siberian volcanics and bolide impacts in parana basin of brazil and elsewhere implicating impact triggered volcanism left catastrophic regional global imprints on sea level climate marine anoxia and tectonic stability that connected the p tr crisis across terrestrial and marine realms worlwide

no link between the panjal traps kashmir and the late permian mass extinctions 1 voluminous late permian flood basalt eruptions are contemporaneous with the mid capitanian 260 ma and end permian 251 ma mass extinction events the panjal traps of kashmir are thought to be correlative to the mid capitanian mass extinction however no radiometric age has been determined we report a single zircon u pb laser ablation icp ms date of a rhyolite from the lower middle part of the volcanic sequence twenty four individual zircon crystals yield a mean 206u 238pb age of 289 3 ma the results show that the panjal traps are considerably older than previously interpreted and not correlative to post neo tethys rifting of the gondwanan margin or the mid capitanian mass extinction and are in fact correlative to the opening of the neo tethys ocean in contrast to other similarly size large igneous provinces the panjal traps are not coincident with a mass extinction event and therefore casts doubt on the direct relationship between continental flood basalt volcanism and ecosystem collapse

theory and application of the day plot mrs ms versus hcr hc 2 application to data for rocks sediments and soils 1 new theoretical curves relating the hysteresis parameters mrs ms and hcr hc for single domain sd superparamagnetic sp pseudo single domain psd and multidomain md grains and their mixtures are applied to published data for natural materials the day plot of mrs ms versus hcr hc has been used to crudely classify samples into box like sd psd and md or sometimes incorrectly md sp regions with arbitrary boundaries new type curves for md psd sd md and sd sp grains and mixtures permit more subtle and precise modeling the predicted md trend and its junction with the psd trend are observed in two data sets for magnetite spherules from carbonate rocks and for temperature varying hysteresis results spanning the verwey transition the latter data are the basis of a suggested new method for pinpointing the psd md threshold size selected data for pottery clays soils and paleosols generally follow sd md type curves and indicate intermediate size psd magnetite with narrow to broad size distributions a lake sediment section with known grain size progression tracks in the predicted sense along the sd md trend selected data for glaciomarine and pelagic sediments are also generally compatible with sd md trends examples of remagnetized carbonate rocks submarine basaltic glasses and glassy rims of pillow basalts all follow predicted sp sd or sp psd mixing curves with a large range in volume fraction of sp grains 0 75 but a narrow range of sp particle sizes 10 2 nm larger sp grains spanning the range to sd size 25 30 nm are absent for unknown reasons oceanic dolerites gabbros and serpentinized peridotites in some cases fall in a novel region of the day plot parallel to but below magnetite sd md mixing curves

volcanism impact and mass extinctions incredible or credible coincidences massive continental volcanism and or bolide impacts are considered by many authors to have caused three major mass extinction events during the last 300 million years the end permian end cretaceous and end triassic extinctions however reevaluation of the frequency of bolide impacts and plume related flood basalt provinces indicates that both types of event occur much more frequently than mass extinctions and so in isolation may not be responsible for the largest extinctions furthermore the kill mechanisms associated with either flood basalts or impacts do not appear to be sufficiently powerful to cause worldwide collapse of ecosystems leading to the largest mass extinctions contemporaneous flood basalts and bolide impact may be prerequisites for the largest mass extinctions we present a statistical analysis of the probability of coincidence between volcanism and impact and show that three random coincidences of these events in the last 300 m y are likely no causal relationship between impact and volcanism is necessary the lesser mass extinctions on the other hand may not require juxtaposition of two such catastrophic events such coincidences occurring on more than three occasions during the last 300 m y become increasingly unlikely d 2004 elsevier b v all rights reserved

late paleozoic faunal climatic and geographic changes in the baoshan block as a gondwana derived continental fragment in southwest china abstract the carboniferous and permian of the baoshan block consist of three major depositional sequences a lower carboniferous carbonate sequence a lower permian siliciclastic sequence and a middle permian carbonate sequence these three sequences were interrupted by two major regressive events first the namurian uplift ranging in age from serpukovian to gzhelian and second the post sakmarian regression occurring probably at artinskian time in the baoshan block although the precise time interval of the latter event is still unclear the baoshan block is characterized by warm water highly diverse and abundant faunas during the early carboniferous by cold water and low diversity faunas during the early permian and by possibly warm water but low diversity faunas during the middle permian the sweetognathus bucaramangus conodont fauna constrains the upper boundary of the diamictite bearing siliciclastic deposits dingjiazhai formation to the sakmarian to early artinskian as well as the eruption of the rifting basalts woniusi formation to at least the post early artinskian paleozoogeographically affiliation of the faunas in the baoshan block changed from eurasian in the early carboniferous to peri gondwanan in the early permian and to marginal cathaysian cimmerian in the middle permian cimmerian blocks have more or less comparable geohistory to one another in the carboniferous and permian during the middle permian the eastern cimmerian blocks such as sibumasu s s baoshan and tengchong are not far from the palaeoequator but apparently more distant than the western cimmerian blocks based on the presence or absence of some index taxa such as the fusulinaceans eopolydiexodina and neoschwagerina and the corals thomasiphyllum and wentzellophyllum persicum

mineral magnetic variation of the jiaodao chinese loess paleosol sequence and its bearing on long term climatic variability 1 to retrieve reliable long term paleoclimatic signals from the chinese loess paleosol sequences deposited over the past 2 6 myr multiparameter mineral magnetic investigations have been conducted on the jiaodao section on the chinese central loess plateau first the lithogenic magnetic components and the pedogenic overprinting were chemically separated by the citrate bicarbonate dithionite cbd method the magnetic properties of the least pedogenically altered loess units and post cbd loess paleosols are dominated by coarse grained lithogenic magnetite increasing degree of pedogenesis increases both the concentration and grain size of pedogenic magnetite maghemite long term changes of the pre cbd magnetic properties suggest a long term decrease in summer monsoon intensity and a long term increase in winter monsoon intensity from the late pliocene to the late pleistocene long term variations of the post cbd magnetic properties suggest an increase in both concentration and grain size of coarse grained lithogenic psd md magnetite grains and hence indicate a long term increase in winter monsoon intensity over that period the coercivity decrease of the lithogenic component for the loess unit l15 may be related to the accelerated uplift of the tibetan plateau and its adjacent regions during the period of l15 deposition from paleosol s5 to loess l1 higher values of coercivity of the lithogenic component occur in typical loess and paleosols and lower values are found at the loess paleosol transition these coercivity variations are thought to be related to significant changes in the source region as well as dust deposition in the loess plateau caused by changes in ice snow or vegetational cover these new results lead to a better understanding of the relationships between the effects of tectonic paleoclimatic and paleoenvironmental processes in northwestern china

global time scale and regional stratigraphic reference scales of central and west europe east europe tethys south china and north america as used in the devonian carboniferous permian correlation chart 2003 dcp 2003 the boundaries of the devonian carboniferous and permian stages of the global stratigraphic reference scale abbreviated to global stratigraphic scale gss are described in relation to the biostratigraphic and or lithostratigraphic units of the regional stratigraphic reference scales abbreviated to regional stratigraphic scales rss of central and west europe east europe tethys south china eastern tethys and north america in their type regions the boundaries of gss units rarely coincide with those of homonymous rss units moreover the definitions of some rss units have changed several times over the last decades and subsequent misunderstanding of the stratigraphical significance of these changes has often introduced errors into proposed global correlation charts the stratigraphic framework proposed in our global devonian carboniferous permian correlation chart 2003 dcp 2003 devonian carboniferous permian correlation chart 2003 menning m schneider j w alekseev a s amon e o becker g von bitter p h boardman d r bogoslovskaya m braun a brocke r chernykh v chuvashov b i clayton g dusar m davydov v i dybova jachowicz s forke h c gibling m gilmour e h goretzki j grunt t a hance l heckel p h izokh n g jansen u jin y g jones p kading k ch kerp h kiersnowski h klets a klug ch korn d kossovaya o kotlyar g v kozur h w laveine j p martens th nemyrovska t l nigmadganov a l paech h j peryt t m rohn r roscher m rubidge b schiappa t a schindler e skompski s ueno k utting j vdovenko m v villa e voigt s wahlman g p wardlaw b r warrington g weddige k werneburg r weyer d wilde v winkler prins c f work d m 2004 abschlusskolloquium dfg schwerpunktprogramm 1054 evolution des systems erde wahrend des jungeren palaozoikums im spiegel der sedimentgeochemie abstracts univ erlangen germany 2004 p 43 herein abbreviated to dcp 2003 and cited as dcp 2003 in references is an attempt to reduce these errors the dcp 2003 is the stratigraphic base for project 1054 of the deutsche forschungsgemeinschaft dfg the evolution of the late palaeozoic in the light of sedimentary geochemistry this composite time scale has been carefully balanced as far as data allows to remove unnecessary artificial compression and expansion of time intervals biozonations and depositional events the ages selected in dcp 2003 are markedly different to those in the geologic time scale 1989 gts 1989 harland w b armstrong r l cox a v craig l e smith a g smith d g 1990 a geologic time scale 1989 cambridge univ press cambridge harland w b armstrong r l cox a v craig l e smith a g smith d g 1990 a geologic time scale 1989 cambridge univ press cambridge pp 1 263 and in gradstein and ogg gradstein f m ogg j 1996 a phanerozoic time scale episodes 19 1 2 3 4 insert whereas they are closer to those of the geologic time scale 2004 gts 2004 gradstein f m ogg j g smith a g 2004 a geologic time scale 2004 cambridge univ press cambridge pp 1 589 mostly the ages are rounded to the nearest 0 5 ma in order to avoid estimates of questionable accuracy whereas ages of 0 1 ma in the gts 2004 and their error bars of 0 4 ma to 2 8 ma for the devonian to permian stage boundaries suggest an improved accuracy in contrast in the dcp 2003 questionable ages and positions of stratigraphic boundaries are marked by arrows c 2006 elsevier b v all rights reserved

zircon u pb and hf isotopic constraints from eastern transhimalayan batholiths on the precollisional magmatic and tectonic evolution in southern tibet abstract before the indian collision with asia northward subduction of the neo tethyan oceanic lithosphere produced an andean type convergent margin in south asia characterized by arc magmatism starting from the early jurassic and lasting until the eocene the magmatic arc is now represented by widespread intrusive bodies or the so called transhimalayan batholiths in the lhasa terrane of southern tibet that have been divided into two main magmatic suites i e the northern plutonic belt and the southern gangdese batholith their temporal distribution concerning how exactly the magmatic suites correlate eastwards and then southeastwards around the eastern himalayan syntaxis however remains poorly constrained here we report the first combined zircon u pb and hf isotopic study of the transhimalayan batholiths from the eastern part of the lhasa terrane 95 97 5 e and 28 5 30 n se tibet zircon u pb dating results of 24 granitoids indicate that the rocks were emplaced principally in the early cretaceous 133 110 ma and subordinately in the paleocene 66 57 ma long after an older granite intrusion in the earliest jurassic 198 ma the zircon ehf t values range from 5 to 20 yielding hf crustal model ages tdmc between 0 8 and 2 4 ga that peak at 1 7 ga suggesting a major episode of crustal growth in the proterozoic and a predominantly or even exclusively crustal source for the granitoid petrogenesis these zircon u pb and hf isotopic constraints together with whole rock geochemical characteristics allow us to correlate them to s type granitoids in the northern plutonic belt rather than to the i type gangdese batholith from the central part of the southern lhasa terrane in contrast to the gangdese magmatism that formed with a significant juvenile mantle input related to the neo tethyan subduction these s type granitoids show geochemical similarities to the north american cordilleran interior batholiths that did not form directly from a subduction setting thus we attribute the petrogenesis of the widespread early cretaceous granitoids in the northern belt and eastern himalayan batholiths to a postcollisional regime due to the late jurassic early cretaceous continental collision between the lhasa and qiangtang terranes under this framework the s type magmatism was generated in response to collision induced crustal thickening which may have capabilities of causing crustal anatexis by itself in the region however continued interplay with the neo tethyan subduction zone processes such as back arc extension could also have played a crucial and long lasting role in the magma generation

internal crustal deformation in the northern part of shan thai block new evidence from paleomagnetic results of cretaceous and paleogene redbeds in order to describe the internal deformation of the northeast part of the shan thai block resulting from the penetration of the indian plate into asia a paleomagnetic study was carried out on the cretaceous and paleogene strata in the southern part of the simao terrane high temperature magnetic components with unblocking temperatures around 680 degrees c were isolated and positive fold test shows its primary nature of magnetization the tilt corrected site mean directions of the lower cretaceous and upper cretaceous from the menglun area are d s 46 2 degrees i s 45 9 degrees k 11 0 alpha 95 10 6 degrees and d s 33 2 degrees i s 30 9 degrees k 68 4 alpha 95 8 2 degrees respectively the site mean directions of the upper cretaceous and lower paleogene for the mengban area are d s 50 5 degrees i s 31 0 degrees k 207 6 alpha 95 6 4 degrees and d s 43 5 degrees i s 23 0 degrees k 26 1 alpha 95 13 4 degrees respectively the results of the lower cretaceous and upper paleogene from the mengla area are d s 46 9 degrees i s 42 2 degrees k 27 3 alpha 95 7 7 degrees and d s 41 8 degrees i s 23 8 degrees k 38 9 degrees alpha 95 5 8 degrees respectively in comparison with previous paleomagnetic data of the simao terrane the rotational deformation can be divided into four stages the cretaceous and paleocene sediments of the simao terrane experienced intensive folding before the early oligocene during the early oligocene to early miocene the shan thai and indochina blocks experienced southeastward extrusion with similar to 20 degrees clockwise rotation relative to the south china block during the middle to late miocene the shan thai blocks experienced more 15 degrees clockwise rotation since the late miocene the activity of strike slip faults surrounding the simao terrane enhanced the internal differential rotations of the terrane these deformation processes finally resulted in a complex internal deformation of the simao terrane c 2013 elsevier b v all rights reserved

early permian granitic dykes of alkaline affinity in the indian high himalaya of upper lahul and se zanskar geochemical characterization and geotectonic implications

mineral magnetic variation of the jingbian loess paleosol sequence in the northern loess plateau of china implications for quaternary development of asian aridification and cooling a high resolution mineral magnetic investigation has been carried out on the jingbian loess paleosol sequence at the northern extremity of the chinese loess plateau results show that the magnetic assemblage is dominated by large pseudo single domain and multidomain like magnetite with associated maghemite and hematite variations in the ratios of sirm100mt sirm sirm100mt sirm30mt and sirm100mt sirm60mt sirm is the saturation isothermal remanent magnetization sirmnmt represents the residual sirm after an n mt alternating field demagnetization have been used to document regional paleoclimate change in the asian interior by correlating the mineral magnetic record with the composite 18o record in deep sea sediments the long term up section decreasing trend in those ratios in both loess and paleosol units has been attributed to a long term decrease in the relative contributions of eolian hematite during glacial extrema and of pedogenic hematite during interglacial extrema respectively which reveals a long term decreasing trend in chemical weathering intensity in both glacial stage source region the gobi and deserts in northwestern china and interglacial stage depositional area the loess plateau region we further relate this long timescale variation to long term increasing aridification and cooling during both glacial extrema in the dust source region and interglacial extrema in the depositional area over the quaternary period changes in those ratios are most likely due to quaternary aridification and cooling driven by ongoing global cooling expansion of the arctic ice sheet and progressive uplift of the himalayan tibetan complex during this period

crustal thickening versus lateral expulsion in the indian asian continental collision since the beginning of the continental collision between india and asia there has been about 2500 km of convergence and the northward movement of india has been accommodated by major internal deformation of the asian lithosphere the crustal thickening in and around the tibetan plateau is clearly a direct consequence of this collision but there is considerable debate as to whether a large fraction of the indentation has been accommodated by eastward motion of the lithospheric blocks of southeastern asia and southern china numerical experiments described here test this hypothesis for a range of indentation geometries and rheological models of the lithosphere we employ a thin viscous sheet model of the lithosphere with a depth averaged nonlinear viscous rheology described by a stress strain rate exponent n and including gravitational buoyancy forces scaled by the dimensionless argand number ar the eastern boundary for the collision region is described as a lithostatic boundary the precollision normal stress is determined by static balance and that constant stress is applied throughout the collision the experiments show that during collision the eastern boundary is smoothly displaced to the east at a rate about 1 4 of the indentation rate with only minor variation due to geometry or rheology crustal thickening rates in the region of the plateau are reduced by between 10 and 25 of the corresponding rates determined for similar experiments with a rigid eastern boundary to generalize from the results of these experiments the total north south shortening strain produced by the collision is partitioned between crustal thickening and eastward displacement in the ratio of at least 3 1 and more probably 4 1

devonian paleomagnetism of yunnan province across the shan thai south china suture a paleomagnetic study of devonian sedimentary sequences from western and eastern yunnan china yields contrasting paleolatitudes for these two areas they indicate an equatorial position for eastern yunnan as part of the yangtze paraplatform or south china block and a paleolatitude of about 40 for western yunnan as part of the shan state or shan thai block which probably was part of the gondwana supercontinent the majority of samples is strongly overprinted by a present day field magnetization but thermal demagnetization has been successful in isolating ancient dual polarity characteristic directions of magnetization in rocks from eastern and western yunnan with results from the latter passing the fold test the paleopole from eastern yunnan is located at 8 9 n 10 4 e declination inclination 279 2 2 7 k 13 alpha 95 6 9 n 33 samples from 7 sites the paleopole from western yunnan is located at 66 5 n 133 8 e declination inclination 18 0 62 0 k 21 alpha 95 5 8 n 31 samples from 7 sites yielding a paleolatitude of 42 the two blocks studied are separated by the red yuan river and lancang mekong river fault zones one of which is inferred to be an ancient suture

permian tectonic framework and palaeogeography of se asia abstract the principal continental lithospheric terranes now comprising se asia and that existed in the permian are the south china indochina super terrane and the sibumasu simao west burma and sw borneo semitau terranes the simao terrane is here regarded a separate terrane derived from south china by back arc spreading in the lower carboniferous rather than as an extension of indochina the main palaeo tethys ocean in thailand is identified as being represented by the chiang mai and sra kaeo sutures and the eastern boundary of the sibumasu terrane is thus interpreted to lie farther west in thailand than previously inferred the nan uttaradit suture is interpreted as representing a marginal back arc basin and contiguous with the ailaoshan and jinshajiang sutures in sw china the south china indochina super terrane and the simao terrane were located within the palaeo tethys in equatorial latitudes during the permian where they together with north china exhibit cathaysian floras and faunas the sibumasu terrane was located on the nw australian margin of gondwana until the sakmarian major shifts in faunal affinities from gondwana province faunas to an independent sibumasu province and then to assimilation into the cathaysian province records the separation and rapid northward drift of sibumasu after the late sakmarian the principal permian palaeogeographic models for the region are assessed for internal consistencies and conflicts

cenozoic deformation in western yunnan china myanmar border in the present paper we describe ductile and brittle deformation styles in western yunnan and ne myanmar using field data and landsat 7 imagery we show that this complex area located at the northern termination of sunda plate three rivers area was wedged during the tertiary between the left lateral ailao shan chong shan metamorphic belts to the east and the right lateral shan scarp gaoligong metamorphic belt in west this triangular region therefore underwent the effects of these continental size ductile strike slip faults separating major blocks with a dominant ew to ene compression since the late miocene date of the reversal of motion along the rrf the incipient eastward motion of the sunda block and the persisting right lateral motion along its western boundary sagaing fault created n s compression and e w to wnw extension underlined by left lateral transtension along the wanding nanting fault zones at the same time the diangcan shan situated along strike the ailao shan metamorphic belt was slightly impinged by the blocks extruded from the syntaxis and exhumed again from the early pliocene in accordance with this late and still active state of stress q 2004 elsevier ltd all rights reserved

volcanism mass extinction and carbon isotope fluctuations in the middle permian of china the 260 million year old emeishan volcanic province of southwest china overlies and is interbedded with middle permian carbonates that contain a record of the guadalupian mass extinction sections in the region thus provide an opportunity to directly monitor the relative timing of extinction and volcanism within the same locations these show that the onset of volcanism was marked by both large phreatomagmatic eruptions and extinctions amongst fusulinacean foraminifers and calcareous algae the temporal coincidence of these two phenomena supports the idea of a cause and effect relationship the crisis predates the onset of a major negative carbon isotope excursion that points to subsequent severe disturbance of the ocean atmosphere carbon cycle

permian carboniferous and permian triassic magmatism in the rift zone bordering the tethyan margin of southern pangea magma was emplaced in the india australia rift zone along the tethyan margin during permian carboniferous and permian triassic time permian carboniferous alkalic granite and basaltic and rhyolitic lava flows and tuffs formed at the same time as right lateral transtension of pangea as recorded by the magmatic rocks of neocratonic post variscan europe and post kanimblan eastern australia permian triassic tholeiitic basalt in india alkalic magmatic rocks in oman and rhyolite dolerite and undersaturated alkalic volcanic rocks in western australia preceded and accompanied the early opening of the neo tethys ocean coeval magmatism included the voluminous mid plate siberian traps the emeishan basalt of south china and the peak activity of the magmatic arc along the convergent panthalassan margin the background magmatism probably permitted the siberian traps to trigger the environmental catastrophe at the permian triassic boundary

paleomagnetic results from the upper carboniferous of the shan thai malay block of western yunnan china the upper carboniferous basaltic woniusi formation was sampled at 21 sites from two limbs of a syncline near baoshan city 25 2 n 99 3 e and from a monocline near yongde county 23 9 n 99 2 e for paleomagnetic study the study area is generally thought to be part of the shan thai malay microplate thermal demagnetization reveals a single polarity characteristic remanent magnetization chrm which is carried by both magnetite and hematite with the former being the dominant mineral in basalt and the latter being the principal carrier in associated tuffaceous basalt and sandstone the tilt corrected formation mean from baoshan d 209 2 i 61 0 95 6 7 confirms the results reported by previous workers and a positive fold test constrains the chrm acquisition to be prefolding the paleomagnetic inclinations determined from this study are similar to that derived from the devonian rocks from the same area by other workers indicating a paleolatitude of about 42 for the baoshan area during the devono carboniferous time the paleomagnetic declinations however present a large difference between the two sampling localities for the upper carboniferous as well as between the sampling sites for the devonian and for the upper carboniferous the paleo declination difference can be partly explained by the apparent polar wander of gondwana if the shan thai malay microplate was rigidly attached to gondwanaland during this time interval the large part of it has to be ascribed to tectonic rotations between the sampling sites this fact suggests that extreme caution should be exerted when trying to establish an apparent polar wander path for and to reconstruct the paleo geographic position of the shan thai malay microplate

errors in acoustic doppler profiler velocity measurements caused by flow disturbance acoustic doppler current profilers adcps are commonly used to measure streamflow and water velocities in rivers and streams this paper presents laboratory field and numerical model evidence of errors in adcp measurements caused by flow disturbance a state of the art three dimensional computational fluid dynamic model is validated with and used to complement field and laboratory observations of flow disturbance and its effect on measured velocities results show that near the instrument flow velocities measured by the adcp are neither the undisturbed stream velocity nor the velocity of the flow field around the adcp the velocities measured by the adcp are biased low due to the downward flow near the upstream face of the adcp and upward recovering flow in the path of downstream transducer which violate the flow homogeneity assumption used to transform beam velocities into cartesian velocity components the magnitude of the bias is dependent on the deployment configuration the diameter of the instrument and the approach velocity and was observed to range from more than 25 at 5 cm from the transducers to less than 1 at about 50 cm from the transducers for the scenarios simulated

tectonic framework and phanerozoic evolution of sundaland abstract sundaland comprises a heterogeneous collage of continental blocks derived from the india australian margin of eastern gondwana and assembled by the closure of multiple tethyan and back arc ocean basins now represented by suture zones the continental core of sundaland comprises a western sibumasu block and an eastern indochina east malaya block with an island arc terrane the sukhothai island arc system comprising the linchang sukhothai and chanthaburi blocks sandwiched between this island arc formed on the margin of indochina east malaya and then separated by back arc spreading in the permian the jinghong nan uttaradit and sra kaeo sutures represent this closed back arc basin the palaeo tethys is represented to the west by the changning menglian chiang mai inthanon and bentong raub suture zones the west sumatra block and possibly the west burma block rifted and separated from gondwana along with indochina and east malaya in the devonian and were accreted to the sundaland core in the triassic west burma is now considered to be probably cathaysian in nature and similar to west sumatra from which it was separated by opening of the andaman sea basin south west borneo and or east java west sulawesi are now tentatively identified as the missing argoland which must have separated from nw australia in the jurassic and these were accreted to se sundaland in the cretaceous revised palaeogeographic reconstructions illustrating the tectonic and palaeogeographic evolution of sundaland and adjacent regions are presented

abor volcanics further evidence for the birth of the tethys ocean in the himalayan segment the himalayan region has a record of several phases of igneous activity which indicate a continued n s orientated tensional regime since at least late precambrian time though the earlier volcanic eruptions were restricted both in time and space the late carboniferous triassic activity was widespread in terms of both the time interval and area covered the abor volcanic activity in the eastern syntaxial bend of the himalayan fold belt is coeval with the initiation of late carboniferous triassic panjal trap volcanism of the western syntaxial bend and eruption of the sikkim lavas chemical characters of the abor volcanics indicate 1 a within plate rift tectonic setting of the lava eruptions 2 a transitional nature between tholeiitic and alkalic compositions 3 relative enrichment in incompatible elements and 4 high fe ti values similar to many such basalts erupted in the regions of active lithospheric rifting the olivine free nature a linear trend for mgo and low co contents of the studied rocks are suggestive of high pressure olivine fractionation for the generation of the bulk chemistry however large variations in the incompatible element abundances and ratios of rocks at a similar fractionation stage discount the evolution of the lava chemistry exclusively by simple fractionation or partial melting processes instead these characters together with the low zr nb ratio and within plate rift tectonic setting suggests the modification of an upper mantle source region possibly by fluid phase co 2 immediately before the partial melting and lithospheric rifting combining geology of the region with the geochemistry and inferred tectonic setting of these rocks the lava eruptions are suggested to have been associated with the 9rift valley stage9 of the tethys ocean formation in the present himalayan region

progress problems and prospects an overview of the guadalupian series of south china and north america abstract the guadalupian epoch is marked by the formation of the pangean supercontinent global sea level change rifting and drifting of the cimmerian continents formation of large igneous provinces and dramatic biotic changes a high resolution biostratigraphic chemostratigraphic and high precision geochronologic framework of this critical transition is fundamental to understanding these events extensive studies of the latest cisuralian and guadalupian series in both south china and north america reveal the same conodont lineages but the conodont interval zones based on jinogondolella within the guadalupian series are slightly diachronous high precision u pb geochronological studies ca id tims method calibrate the base of the guadalupian series base roadian at 273 01 0 14 ma a previously reported age from an ash bed overlying the emeishan flood basalts 259 51 0 21 ma is adopted for the guadalupian lopingian boundary glb based on recently published geochronology and bayesian age modeling from the guadalupian series the base of the capitanian is constrained at 264 28 0 16 ma and the base of the wordian is interpolated to be 266 9 0 4 ma the illawarra reversal is of early middle wordian age both north america and south china possess a distinct negative 13ccarb excursion of 3 5 at the latest kungurian and early roadian lk er cie which coincides with the early stages of a significant 3rd order sea level rise the large end guadalupian 13ccarb negative excursion may have been affected by post depositional diagenesis or a warming event associated with the emeishan volcanism the 87sr 86sr ratios in both regions declined from the latest kungurian to the late capitanian but have different ratios and reveal several fluctuations in the middle guadalupian measured 18oapatite values suggest that the delaware basin was 3 4 c cooler than the eastern yangtze block analysis of a new high resolution database of marine taxa indicates only a minor pre lopingian diversity drop from 261 04 ma to 259 98 ma which coincides with the peak emeishan volcanism the widely perceived end guadalupian mass extinction in north america is evidently masked by and possibly an artefact of a stratigraphic truncation effect due to rapid lithofacies changes from limestone to laminated evaporites with the closure of the west texas basins

flow conditions of undular hydraulic jumps in horizontal rectangular channels the flow conditions of undular jumps for fully developed inflow condition have been investigated systematically if the inflow froude number is larger than 1 2 an undular jump has lateral shock waves near the toe of the jump for a narrow channel the shock waves cross upstream of the first wave crest and the flow conditions of undular jumps depend on the aspect ratio and the inflow froude number in contrast for a wide channel the shock waves do not cross upstream of the first wave crest and the flow conditions of undular jumps are independent of the aspect ratio the flow conditions of undular jumps are classified by considering the cross position of the lateral shock waves and the inflow froude number also the hydraulic conditions for the formation of nonbreaking and breaking undular jumps are determined the effect of the reynolds number on undular jump formations is discussed and changes of the flow conditions with the reynolds number are described

wasp waisted hysteresis loops mineral magnetic characteristics and discrimination of components in mixed magnetic systems rock magnetic studies of complex systems that contain mixtures of magnetic minerals or mixed grain size distributions have demonstrated the need for a better method of distinguishing between different magnetic components in geological materials hysteresis loops that are constricted in the middle section but are wider above and below the middle section are commonly observed in mixed magnetic assemblages such wasp waisted hysteresis loops have been widely documented particularly with respect to rare earth permanent magnets basaltic lava flows remagnetized paleozoic carbonate rocks and an increasingly wide range of other rocks our modelling combined with a review of previous work indicates that there are several conditions that give rise to as well as magnetic properties that are characteristic of wasp waisted hysteresis loops first at least two magnetic components with strongly contrasting coercivities must coexist this condition can arise from either mixtures of grain sizes of a single magnetic mineral or a combination of magnetic minerals with contrasting cocrcivities or a combination of these two situations second materials that give rise to wasp waisted hysteresis loops will have relatively high ratios of the coercivity of remanence to coercive force b cr b c because b0 is controlled by the soft low coercivity component whereas bcris controlled by the hard high coercivity component third values of b cr b c 10 usually only occur for strongly wasp waisted loops when the low coercivity component comprises an overwhelmingly large fraction of the total volume of magnetic grains fourth a given mixture of superparamagnetic and single domain sd grains is more likely to give rise to wasp waisted hysteresis loops than an equivalent mixture of sd and multidomain grains fifth our results provide empirical confirmation that the total magnetization of a material is the sum of the weighted contributions of each component in the absence of significant magnetic interaction between particles thus to contribute significantly to wasp waisted behavior a mineral magnetic component must give rise to a significant portion of the total magnetization of the rock as a result minerals with weak magnetic moments such as hematite need to occur in large concentrations to cause wasp waistedness in materials that also contain ferrimagnetic minerals we outline a method for determining the magnetic components that can give rise to wasp waisted hysteresis loops this method is based on high and low temperature magnetic measurements that are used to identify the dominant remanence bearing mineral s and on mineral magnetic techniques that are used to discriminate between different magnetic domain states the method is illustrated with several examples from archaeological geological and synthetic materials

further paleomagnetic results for lower permian basalts of the baoshan terrane southwestern china and paleogeographic implications abstract the baoshan terrane of southwestern china is considered to have been part of the cimmerian block during the late paleozoic consequently knowledge of its paleoposition and geological evolution can provide constraints on the permian breakup of northern east gondwana therefore we conducted paleomagnetic and rockmagnetic studies on lower permian basalts from four localities in the baoshan terrane the basalts hold a stable characteristic remanent magnetization chrm at high temperatures 300 680 c that is carried by magnetite maghemite and hematite with both pseudo single and multiple domains to test the reliability of data from these volcanic rocks we analyzed the geomagnetic secular variation gsv and reliability of both the present data and previous paleomagnetic data the results from 23 sites yield a single reversed polarity directed downwards to the southwest giving a site mean direction of d g i g 156 7 56 6 k g 8 0 95 11 4 before tilt correction and d s i s 218 3 60 1 k s 14 1 95 8 4 after tilt correction the result passed the fold test but the gsv was able to be averaged out in only two sections all available data were examined section by section using the angular dispersion s b of virtual geomagnetic poles vgps to ensure that the gsv was completely averaged out because the dispersion in declinations is likely to have been affectedby subsequent tectonic deformation the paleosecular variation psv could not be evaluated from all the data amassed from different sections and the psv was able to be removed from only four combined sections a small circle fit of these vgps gives an averaged paleocolatitude of 51 9 3 7 n 31 sites centered on 24 n 99 e the result indicates that the sampled area of the baoshan terrane was located at a latitude of 38 s 3 7 during the late early permian a comparison of this result with early permian data from gondwanan blocks suggests that the baoshan terrane was situated near the junction of northern india and northwestern australia and that it broke away from western australia after the early permian

re evaluating the geochronology of the permian tarim magmatic province implications for temporal evolution of magmatism the permian tarim magmatic province has 118 published ages ranging from 358 to 205 ma but the timing of mafic magmatism is not well constrained we report two new secondary ion mass spectrometry u pb zircon dates on the halahatang trachydacite and wajilitag olivine clinopyroxenite which are 287 2 2 0 ma and 283 2 2 0 ma respectively the trachydacite overlies the uppermost basalt and constrains the latest eruption age of basalt in northern tarim the latter is the first high resolution date for the wajilitag mafic layered intrusion by screening all published ages we identified 22 robust ages ranging from 290 9 4 1 to 261 7 1 8 ma the robust ages together with our new data reveal a protracted period of mafic magmatism at c 283 and c 267 ma silicic magmatism occurred from 291 to 272 ma although the current known volume of tarim basalt is too small to qualify as a large igneous province the eroded and intrusive components as well as pyroclastic deposits and silicic lavas may increase the estimated volume further work is required to refine the duration of magmatism and the volume estimate of the province supplementary material a list of all the published dates raw data of published 40 ar 39 ar dates raw data of published u pb dates published geochemistry data used for calculation and complete details of the data evaluation are available at http www geolsoc org uk sup18862

early permian pangea b to late permian pangea a the pre drift wegenerian model of pangea is almost universally accepted but debate exists on its pre jurassic configuration since tedirving introd ucedpangea b by placing gond wana farther to the east by v3000 km with respect to laurasia on the basis of paleomagnetic data new paleomagnetic data from radiometrically dated early permian volcanic rocks from parts of adria that are tectonically coherent with africa gondwana integrated with published coeval data from gondwana and laurasia again only from igneous rocks fully support a pangea b configuration in the early permian the use of paleomagnetic data strictly from igneous rocks excludes artifacts from sedimentary inclination error as a contributing explanation for pangea b the ultimate option to reject pangea b is to abandon the geocentric axial dipole hypothesis by introducing a significant non dipole zonal octupole component in the late paleozoic time averaged geomagnetic field we demonstrate however by using a dataset consisting entirely of paleomagnetic directions with low inclinations from sampling sites confined to one hemisphere from gondwana as well as laurasia that the effects of a zonal octupole field contribution would not explain away the paleomagnetic evidence for pangea b in the early permian we therefore regard the paleomagnetic evidence for an early permian pangea b as robust the transformation from pangea b to pangea a took place during the permian because late permian paleomagnetic data allow a pangea a configuration we therefore review geological evidence from the literature in support of an intra pangea dextral megashear system the transformation occurred after the cooling of the variscan mega suture andlasted v20 myr in this interval the neotethys ocean opened between india arabia and the cimmerian microcontinents in the east while widespread lithospheric wrenching and magmatism took place in the west around the adriatic promontory the general distribution of plate boundaries and resulting driving forces are qualitatively consistent with a right lateral shear couple between gondwana and laurasia during the permian transcurrent plate boundaries associated with the pangea transformation reactivated variscan shear zones andwere subsequently exploitedby the opening of western neotethyan seaways in the jurassic

an island of dwarfs reconstructing the late cretaceous haţeg palaeoecosystem abstract the cretaceous was a special time in the evolution of terrestrial ecosystems and yet the record from europe in particular is patchy this special issue brings together results of multidisciplinary investigations on the late cretaceous ha eg area in southwestern romania and its continental fossil assemblage with the aim of exploring an exceptional palaeoecosystem from the european late cretaceous the ha eg dinosaurs which seem unusually small have become especially well known as some of the few latest cretaceous dinosaurs from europe comparable with faunas from the south of france and spain and preserved at a time when most of europe was under the chalk seas eastern europe then at a time of exceptionally high sea level was an archipelago of islands some of them inhabited but none so extraordinary as ha eg if ha eg truly was an island and this is debated the apparently small dinosaurs might well be dwarfs as enunciated over 100 years ago by the colourful baron franz nopcsa discoverer of the faunas the dwarfing of dinosaurs and other taxa is explored in this volume the ha eg dinosaurs appear to be very latest cretaceous maastrichtian in age and they provide unique evidence at a time when there are few dinosaurs known from europe about some of the last faunas before the kt mass extinction further the flora and fauna ostracods fishes frogs turtles lizards crocodilians pterosaurs dinosaurs and mammals have never been reviewed comprehensively and we provide here the current best evidence of what was there and how the taxa fit in a global context