paleo tethyan evolution of tibet as recorded in the east cimmerides and west cathaysides the paleozoic early mesozoic geology of tibet was controlled by the rift drift seafloor spreading and subduction zone tectonics of a paleo tethyan realm which evolved between the west cathaysides wc and the east cimmerides ec different suture zones with ophiolites and ophiolitic melanges high pressure metamorphic belts magmatic arcs and accretionary prism complexes separating different terranes mark multiple subduction accretion systems within this paleo tethyan domain reminiscent of the modern western pacific ocean discrete basins separated by different continental blocks and magmatic arcs constituted a complex paleogeography of paleo tethys and these oceanic strands were closed as a result of subduction with different polarities during the late paleozoic triassic the longmu tso shuanghu changning menglian suture zone ls cms in tibet represents the main tectonic boundary between the wc and ec that developed in the devonian the east kunlun a nyemaqen oceanic slab was subducted northward beneath the east kunlun terrane in northern tibet whereas the sumdo oceanic slab was subducted northward beneath the south qiangtang north lhasa terrane in southern tibet the longmu tso shuanghu changning menglian and jinshajiang ailaoshan song ma ophiolites were developed and emplaced in subduction accretion systems with opposite polarities westward and eastward beneath the north qiangtang qamdo simao indochina terrane in central tibet the jinshajiang ailaoshan song ma oceanic slab was subducted westward beneath the north qiangtang simao indochina terrane along the jinshajiang and ailaoshan song ma trenches in a trench ridge trench triple junction plate configuration the emeishan mantle plume produced a large permian basaltic terrane developed on the western passive margin of the south china block the final closure of the paleo tethyan oceanic branches resulted in continental collisions and development of a vast indosinian orogenic collage in the latest triassic jurassic

monitoring and modelling particle and reach scale morphological change in gravel bed rivers applications and challenges this paper focuses on developments in topographic data acquisition including airborne remote sensing digital photogrammetry differential gps and laser profiling e g lidar technologies that allow rapid acquisition of high resolution and high precision topographic data sets over a range of spatial scales these developments have offered new opportunities for investigating spatial and temporal patterns of morphological change in gravel bed rivers and have contributed to revitalization in three key areas 1 morphometric estimates of sediment transport and sediment budgeting 2 boundary conditions for numerical models including computational fluid dynamics and cellular modelling 3 three dimensional characterisation of morphology that is independent of flow stage the potential is clear but there remain a number of significant challenges including quality control and the effects of error on specific applications and morphologies this paper presents results from two investigations representing field and laboratory analyses of gravel bed river morphology at different spatial scales and for different applications case study 1 is concerned with monitoring and modelling morphological change in a large braided gravel bed river using ground based gps survey and digital photogrammetry derived from airborne imagery case study 2 is an investigation of the mechanisms for infiltration of fine sediment into gravel bed rivers which applies close range laser altimetry in flume experiments to derive very high resolution digital elevation models dems that are used to quantify and analyse changes in bed texture these case studies highlight the strengths and weaknesses of specific technologies and approaches to analysis of channel and floodplain morphology and change and suggest key areas that remain to be fully resolved in particular the critical need to define a specific threshold level of detection associated with each acquisition method and for different fluvial settings e g bar surface sub aqueous zone is emphasised

the modi taung nankwe gold district slate belt central myanmar mesothermal veins in a mesozoic orogen abstract the recently discovered quartz gold veins comprising the modi taung nankwe gold district in central myanmar are largely hosted by mudstones of the late palaeozoic slate belt mesozoic rocks of the paunglaung mawchi zone separate the slate belt from the shan scarp and shan plateau to the east at modi taung 5 km of exploration adits indicate that the veins within steeply dipping oblique reverse slip shear zones are displaced by movements along the shears intruded by late jurassic calc alkaline dykes and offset on conjugate cross faults drill intercepts show that mineralization extends vertically for more than 500 m coarse visible gold book and ribbon texture and stylolitic laminations and trace metal values are consistent with mineralization at mesothermal depths of several kilometres in the brittle ductile regime our field observations suggest that mineralization took place in the early jurassic following collision of myanmar on the passive western margin of a greater shan thai continental block with an oceanic arc on the overriding plate to the west collision generated intra continental thrusting in and east of the paunglaung mawchi zone metamorphism of plateau rocks thrust west beneath the slate belt to form the mogok metamorphics and ascent of mineralizing fluids expelled from dehydrating underthrust rocks reversal in orogenic polarity initiated late jurassic eastward subduction of oceanic crust beneath myanmar and generation of a magmatic arc with dykes cutting the quartz gold veins renewed east directed thrusting translated the slate belt over arc clastics and probably resulted in exhumation of the mogok metamorphics and offsets of the veins on conjugate faults young k ar rb 87 sr 86 and ar 40 ar 39 ages on the mogok metamorphic belt imply renewed tertiary uplift and possibly intrusion of mid tertiary or palaeogene granites

mesozoic cenozoic tectonic evolution and metallogeny in myanmar evidence from zircon cassiterite u pb and molybdenite re os geochronology abstract it is well known that there are many sn w mo and cu au metal resources in myanmar however the absence of precise mineralization ages for these deposits significantly hinders to understand the close genetic relationship among metallogeny ore bearing intrusions and tectonic evolution in this study two groups of consistent molybdenite re os and zircon u pb ages indicate that the dapingba mo w deposit in northern myanmar tengchong terrane formed at early cretaceous 119 ma and 114 ma the dapingba ore bearing granitic magmas were mainly derived from melting of ancient tengchong crust on the basis of zircon hf isotopic compositions ehf t 9 3 to 2 5 moreover the first reported cassiterite u pb ages of 60 ma for the bawapin and kalonta sn w deposits in southern myanmar western sibumasu terrane suggest that the two deposits formed at paleocene whereas the precise molybdenite re os age for the shangalon porphyry cu au deposit in the west burma terrane indicates that this deposit formed at eocene 39 ma importantly combined with previous studies on tectonic evolution and magmatic petrogenesis in myanmar and southwest china a comprehensive mesozoic cenozoic tectono magmatic and metallogenic model are proposed two periods of early cretaceous 120 114 ma and late cretaceous 75 70 ma crust derived felsic melts and related mo sn w deposits from the tengchong and western sibumasu terranes likely formed in a continental arc during subduction of the meso and neo tethys oceanic lithosphere respectively subsequently paleocene eocene 60 50 ma sn w deposits and coeval ore bearing granites in the western sibumasu terrane possibly formed during roll back of the neo tethys oceanic slab after 50 ma india asia collision eocene 41 39 ma porphyry cu au west burma terrane and sn w deposits western sibumasu terrane likely formed during the neo tethys oceanic slab tear and break off in a collisional setting whereas miocene 19 14 ma high sulfidation epithermal cu deposit in the west burma terrane possibly formed in an arc setting during oblique subduction of the indian oceanic lithosphere

late cretaceous early palaeogene tectonic development of se asia abstract the late cretaceous early palaeogene history of the continental core of se asia sundaland marks the time prior to collision of india with asia when se asia from the tethys in the west to the palaeo pacific in the east lay in the upper plate of subduction zones in myanmar and sumatra subduction was interrupted in the aptian albian by a phase of arc accretion woyla and mawgyi arcs and in java eastern borneo and western sulawesi by collision of continental fragments rifted from northern australia subsequent resumption of subduction in the myanmar thailand sector explains 1 early creation of oceanic crust in the andaman sea in a supra subduction zone setting 95 ma 2 the belt of granite plutons of late cretaceous early palaeogene age starting 88 ma in western thailand and central myanmar and 3 amphibolite grade metamorphism between 70 and 80 ma seen in gneissic outcrops in western and central thailand and 4 accretionary prism development in the western belt of myanmar until glancing collision with the ne corner of greater india promoted ophiolite obduction deformation and exhumation of marine sediments in the early palaeogene the ranong strike slip fault and other less well documented faults were episodically active during the late cretaceous palaeogene time n to nw directed subduction of the palaeo pacific ocean below southern china vietnam and borneo created a major magmatic arc associated with rift basins metamorphic core complexes and strike slip deformation which continued into the late cretaceous the origin and timing of termination of subduction has recently been explained by collision of a large luconia continental fragment either during the late cretaceous or palaeogene evidence for such a collision is absent from the south china sea well and seismic reflection record and here collision is discounted instead relocation of the subducting margin further west possibly in response of back arc extension which created the proto south china sea is preferred lying between the two subduction related arcs the khorat basin is of predominantly late jurassic early cretaceous age but stratigraphic and apatite fission track data also indicates deposition of 1 2 km of late cretaceous sediments the synformal basin geometry probably arose due to the dynamic topography created by converging tethyan and palaeo pacific subduction zones the aptian albian slowing of basin subsidence and onset of evaporite deposition coincides with collision of the mawgyi and woyla island arcs extensive palaeogene deformation and exhumation 3 km in places affected all margins of the khorat plateau deformation includes folds of the phu phan uplift and strike slip faults thrusts and folds on the southern and eastern margins south of the khorat plateau outcrop and seismic reflection data from the ton le sap basin cambodia and the gulf of thailand indicate syn depositional fault controlled subsidence was important during cretaceous deposition the hot thickened crust developed during the late cretaceous palaeogene events follows the weak indosinian crustal scale inthanon and sukhothai zones which persistently guided the location of later structures including cenozoic extensional and post rift basins and influenced the widespread occurrence of low angle normal faults metamorphic core complexes and eastern gulf of thailand super deep post rift basins

tin metallogenesis associated with granitoids in the southwestern sanjiang tethyan domain nature deposit types and tectonic setting article i nfo tin mineralization in the southwestern sanjiang tethys sn metallogenic domain extends from the southeast asia tin belt in the south the eastern part of the domain does not contain significant sn deposits whereas the central part of the domain composed of the changning menglian sn belt and related to ca 239 178 ma s type granitoids generated by the collision between tengchong baoshan and simao blocks carries wide spread the hydrothermal vein type mineralization the western part of the domain composed of the tengchong baoshan sn metallogenic belt is related to both 136 113 ma and 89 52 ma s type granitoids the former granitoids resulted from the collision between western burma and tengchong baoshan blocks and generated skarn type tin deposits the younger groups correspond to the india asia continental collision and are associated with the xiaolonghe and lailishan greisen type sn deposits

late triassic granites from bangka indonesia a continuation of the main range granite province of the south east asian tin belt the south east asian tin belt is one of the most tin productive regions in the world it comprises three north south oriented granite provinces of which the arc related eastern granite province and the collision related main range granite province run across thailand singapore and indonesia these tin producing granite provinces with different mineral assemblages are separated by paleo tethyan sutures exposed in thailand and malaysia the eastern province is usually characterised by granites with biotite hornblende main range granites are sometimes characterised by the presence of biotite muscovite however the physical boundary between the two types of granite is not well defined on the indonesian tin islands because the paleo tethyan suture is not exposed on land there both hornblende bearing previously interpreted as i type and hornblende barren previously interpreted as s type granites are apparently randomly distributed on the indonesian tin islands granites exposed on bangka the largest and southernmost tin island no matter whether they are hornblende bearing or hornblende barren are geochemically similar to malaysian main range granites the average epsilon nd t value obtained from the granites from bangka average epsilon nd t 8 2 falls within the range of the main range province 9 6 to 5 4 these granites have sims zircon u pb ages of ca 225 ma and ca 220 ma respectively that are both within the period of main range magmatism similar to 226 201 ma in the peninsular malaysia we suggest that the granites exposed on bangka represent the continuation of the main range province and that the paleo tethyan suture lies to the east of the island

the role of strike slip faults in the displacement of the palaeotethys suture zone in southeast thailand abstract six n s tectono stratigraphic belts can be recognized in southeast thailand each with a distinct stratigraphy and igneous history the westernmost belt i is thought to be part of the sibumasu block and the easternmost v to include part of the indochina block between those belt iii comprises acid volcanic rocks volcaniclastics and carboniferous to triassic sedimentary rocks with distinctive faunas interpreted to be a volcanic arc belt iv comprises triassic rocks of back arc basin origin belt v is interpreted as a permian accretionary complex on the western flank of indochina and vi is an unconformable cover of jurassic cretaceous red beds correlating with the khorat group a history of the triassic indosinian orogeny is proposed leading to the cratonization of southeast thailand by the end triassic the apparent absence in southeast thailand of rocks from the devonian triassic palaeotethys ocean the inthanon zone of northern thailand is suggested to have resulted from a phase of post indosinian oblique to longitudinal sinistral strike slip faulting that phase is thought to have included displacement on the mae yuam fault which bounds the inthanon zone in northern thailand then followed a phase of transverse sinistral strike slip faulting which offset the tectono stratigraphic belts and faults of the earlier phase

b rich melt immiscibility in late cretaceous nattaung granite myanmar implication by composition and b isotope in tourmaline abstract there is a strong controversy about the petrogenesis of tourmaline nodules and their relationship with coeval tourmaline bearing granites which are commonly associated with magmatic hydrothermal rare metal deposits e g sn nb and ta in this study tourmaline is extensively distributed in tourmaline bearing nodules nt type pegmatite pt type and fine grained granitic dyke gt type which are hosted by the late cretaceous nattaung biotite granite myanmar zircon u pb dating results 71 ma indicate that pt and gt types tourmaline bearing magmatic rocks formed synchronously with biotite granite all tourmalines have alkali group and schorl composition with mg mg fe ratios of 0 03 0 45 and na na ca ratios of 0 73 to 1 00 nt type tourmaline shows high nb ta ratios and v and sr contents indicating that they were likely crystallized from b rich melts early immiscible with less evolved granitic magmas pt and gt type tourmalines probably formed in aggregated b rich melts that continuously separated from more evolved granitic magma supported by their low nb ta ratios and v and sr contents in addition the studied tourmaline displays a slight variation of b isotopic compositions 11b values ranging from 12 2 0 7 to 14 9 0 4 likely resulted by rayleigh fractionation of tourmaline their light b isotopic values are consistent with those of average continental crust also revealing that the nattaung granite was mainly derived from partial melting of the ancient sibumasu crust importantly late stage pt and gt type tourmalines have higher sn zn nb and ta contents than early stage nt type tourmaline suggesting that the evolved b rich magma could be one precursor to produce sn nb ta zn deposits associated with extensive tourmaline in the world

rb sr sm nd and u pb geochronology of the rocks within the khlong marui shear zone southern thailand abstract in southern thailand the khlong marui shear zone is dominated by a nne ssw striking high topographic lozenge shaped area of ca 40 km long and 6 km wide between the khlong marui fault and the bang kram fault the geology within this strike slip zone consists of strongly deformed layers of mylonitic meta sedimentary rocks associated with orthogneisses mylonitic granites and pegmatitic veins with a steeply dipping foliation the strike slip deformation is characterized by dextral ductile deformation under amphibolite facies and low to medium greenschist facies in situ u pb ages of inherited zircon cores from all zircons in the khlong marui shear zone indicate that they have the same material from the archean late triassic to late cretaceous ages obtained for zircon outer cores of the mylonitic granite are probably related to a period of magmatic activity that was significantly influenced by the west burma and shan thai collision and the subduction along the sunda trench the early dextral ductile deformation phase of the khlong marui shear zone in the early eocene suggested by u pb ages of zircon rims and the later dextral transpressional deformation in the late eocene indicated by mica rb sr ages rb sr sm nd and u pb dating correlation implies that the major exhumation period of the ductile lens was in the eocene this period was tectonically influenced in the se asia region by the early india asia collision

india and sunda plates motion and deformation along their boundary in myanmar determined by gps using a regional gps data set including 190 stations in asia from nepal to eastern indonesia and spanning 11 years we update the present day relative motion between the indian and sundaland plates and discuss the deformation taking place between them in myanmar revisiting measurements acquired on the main boundary thrust in nepal it appears that points in southern nepal exhibit negligible deformation with respect to mainland india including these points using a longer time span than previous studies and making an accurate geodetic mapping in the newest reference frame allows us to refine the present day indian motion our results confirm that the current motion of india is slower than predicted by the nuvel 1a model and in addition our india eurasia motion is significantly 5 mm yr slower than previous geodetic determinations this new indian motion combined with a refined determination of the sundaland motion gives way to a relative india sunda angular velocity of 20 2 n 26 1 e 0 370 myr in itrf2000 predicting a relative motion of 35 mm yr oriented n10 at the latitude of myanmar there the sagaing fault accommodates only 18 mm yr of right lateral strike slip only half of the shear component of motion we present two models addressing how and where the remaining deformation may occur a first model of distributed deformation implies convergence on the arakan subduction the northern continuation of the now famous sumatra andaman trench and wrench faulting in the arakan wedge the second model uses localized deformation where deformation observed west of the sagaing fault is entirely due to elastic loading on a faster and oblique arakan subduction 23 mm yr this latter model predicts that a major earthquake of mw 8 5 may occur every century on this segment of the subduction

should sibumasu be renamed sibuma the case for a discrete gondwana derived block embracing western myanmar upper peninsular thailand and ne sumatra the luxi nujiang suture which extends from yunnan into myanmar is shown to continue into thailand and the malacca strait it forms the eastern boundary of a discrete block here called the irrawaddy block which was formerly considered to be part of gondwana derived sibumasu it has a distinct palaeozoic succession with thick lower permian glacially influenced diamictite bearing marine mass flow intervals deposited at the gondwana margin the rest of sibumasu east of the suture also has local thin lower permian diamictite units however they have been interpreted as ice rafted deposits laid down at a greater distance from the gondwana margin in ne sumatra a diamictite bearing carboniferous lower permian succession has also been described as of mass flow origin and it is suggested that it is also part of the irrawaddy block it requires that the bounding suture is aligned se beneath the malacca strait in the late cretaceous palaeogene the dextral india australia oceanic transform propagated onshore as a strike slip fault bounding on the east the north going india plate it disrupted the irrawaddy block and for much of its length coincided with the line of the earlier suture insofar as the acronym sibumasu was coined to include sumatra consideration should be given to renaming this block sibuma

the crustal architecture of myanmar imaged through zircon u pb lu hf and o isotopes tectonic and metallogenic implications abstract the tethys margin in central and eastern asia is comprised of continental terranes separated by suture zones some of which remain cryptic determining the crustal architecture and therefore the geological history of the eastern tethyan margin remains challenging sited in the heart of this region myanmar is a highly prospective but poorly explored minerals jurisdiction a better understanding of myanmar s mineralization can only be realized through a better understanding of its tectonic history itself reflected in at least four major magmatic belts the eastern and the main range provinces are associated with the late permian to early triassic closure of palaeo tethys the mogok mandalay mergui belt and wuntho popa arc are a response to the eocene closure of neo tethys however magmatic ages outside these two orogenic events are also recorded we present new zircon u pb lu hf and o isotope data from magmatic rocks across myanmar which we append to the existing dataset to isotopically characterize myanmar s magmatic belts eastern province permian i type magmatism has evolved ehf 10 9 to 6 4 whilst main range province triassic s type magmatism also records evolved ehf 13 5 to 8 8 the mogok mandalay mergui belt is here divided into the tin province and the mogok metamorphic belt the tin province hosts ca 77 50 ma magmatism with evolved ehf 1 2 to 15 2 and 18o of 5 6 8 3 the mogok metamorphic belt exhibits a more complex magmatic and metamorphic history and granitoids record jurassic late cretaceous and eocene to miocene phases of magmatism all of which exhibit evolved ehf values between 4 6 and 17 6 and 18o between 6 3 and 9 2 from the tagaung myitkyina belt we report a magmatic age of 172 ma and ehf of 18 1 to 10 8 to accommodate the geological evidence we propose a tectonic model for myanmar involving a greater sibumasu where the documented zircon isotopic variations reflect compositional variations in magmatic source and invoke the role of a tengchong block the baoshan block and greater sibumasu were likely assembled on or before the triassic a former andean margin and suture which may lie across the northern shan plateau and reflected in isotopic differences between the northern and southern parts of the mogok metamorphic belt this contiguous sibumasu baoshan block then sutured onto the indochina margin in the late triassic we propose that a tengchong block within myanmar provides for a southerly termination of the meso tethys suture immediately north of the mogok area a discrete tengchong block may explain a discontinuous arc of late triassic to jurassic i type magmatism in central myanmar representing an andean type margin sited above a subducting meso tethys on the margin of sibumasu the tengchong block sutured onto greater sibumasu before the late cretaceous after which subduction of neo tethys drove the magmatism of the wuntho popa arc and ultimately that of the tin province the metallogenic character of granite belts in myanmar reflects the crustal architecture of the region which is remarkable for its prolific endowment of granite hosted sn w mineralization in two quite distinct granite belts related to sequential indosinian and himalayan orogenesis

influence of survey strategy and interpolation model on dem quality accurate characterisation of morphology is critical to many studies in the field of geomorphology particularly those dealing with changes over time digital elevation models dems are commonly used to represent morphology in three dimensions the quality of the dem is largely a function of the accuracy of individual survey points field survey strategy and the method of interpolation recommendations concerning field survey strategy and appropriate methods of interpolation are currently lacking furthermore the majority of studies to date consider error to be uniform across a surface this study quantifies survey strategy and interpolation error for a gravel bar on the river nent blagill cumbria uk five sampling strategies were compared i cross section ii bar outline only iii bar and chute outline iv bar and chute outline with spot heights and v aerial lidar equivalent derived from degraded terrestrial laser scan tls data digital elevation models were then produced using five different common interpolation algorithms each resultant dem was differentiated from a terrestrial laser scan of the gravel bar surface in order to define the spatial distribution of vertical and volumetric error overall triangulation with linear interpolation tin or point kriging appeared to provide the best interpolators for the bar surface lowest error on average was found for the simulated aerial lidar survey strategy regardless of interpolation technique however comparably low errors were also found for the bar chute spot sampling strategy when tins or point kriging was used as the interpolator the magnitude of the errors between survey strategy exceeded those found between interpolation technique for a specific survey strategy strong relationships between local surface topographic variation as defined by the standard deviation of vertical elevations in a 0 2 m diameter moving window and dem errors were also found with much greater errors found at slope breaks such as bank edges a series of curves are presented that demonstrate these relationships for each interpolation and survey strategy the simulated aerial lidar data set displayed the lowest errors across the flatter surfaces however sharp slope breaks are better modelled by the morphologically based survey strategy the curves presented have general application to spatially distributed data of river beds and may be applied to standard deviation grids to predict spatial error within a surface depending upon sampling strategy and interpolation algorithm

structures uplift and magmatism of the western myanmar arc constraints to mid cretaceous paleogene tectonic evolution of the western myanmar continental margin abstract knowledge of trans himalayan tectono magmatic evolution is critical to understanding the complex pre collisional history of southern eurasia active continental margin it has been proposed that magmatic rocks of the trans himalayan batholith extending from southern tibet to southeast asia are now exposed as the western myanmar arc and central granite belt in myanmar yet origin emplacement and relationships of the two juxtaposed belts remain poorly constrained in this study 2d seismic and drilling data for the western myanmar arc zircon u pb age and hf isotope and whole rock geochemical data for magmatic rocks from the arc have been applied our seismic profiles borehole stratigraphic sequences and zircon u pb data show that a typical arc basin system was well developed along the western myanmar continental margin the magmatic arc has experienced at least three igneous events in the mid cretaceous 110 90 ma latest cretaceous early paleocene 69 64 5 ma and eocene 53 38 ma as well as three associated uplift processes in the late cretaceous eocene and late oligocene whole rock geochemical characteristics and zircons showing variable but predominately positive e hf t values suggest a significant juvenile mantle source involving a proportion of ancient subducted sediments and juvenile crustal materials for these typical arc related magmatic rocks the identification of mid cretaceous to paleogene magmatic rocks having positive e hf t values from the western myanmar arc 1 indicates that the magmatism can be correlated with the gangdese arc within the lhasa terrane of the southern tibetan plateau 2 provides evidence for the proximal derived model that paleogene sediments in the central myanmar basin were from the western myanmar arc but were not delivered by the paleo yarlung tsangpo irrawaddy river system from the gangdese arc and 3 enables a model of eastward subduction of the neo tethyan indian oceanic crust to reflect onset of the magmatism at the mid cretaceous and a long existed back arc extension in western myanmar

late cenozoic to recent transtensional deformation across the southern part of the gaoligong shear zone between the indian plate and se margin of the tibetan plateau and its tectonic origin abstract within the southeastern part of the tibetan plateau the gaoligong shan shear zone forms the boundary between the tengchong and baoshan blocks and is one of the main cenozoic strike slip fault systems of the eastern himalayan syntaxis the mountain ranges rise to a maximum elevation of 3623 m with a width of 20 km and a length of 400 km the core of the shear zone consists of a narrow belt of mylonitic rocks with right lateral strike slip fabrics formed during the northward movement of india relative to eurasia in oligocene and miocene time to the south the mountains decreases in elevation and end against the wanding fault the latter is one of a series of ne sw striking active left lateral strike slip faults within the southeastern part of the tibetan plateau the cause and timing for the change in elevation of the gaoligong shan is unknown but based on our recent structural and fission track geochronological work the decrease in elevation is the result of east west extension across the southern part of the gaoligong shear zone inferred from the late cenozoic and active normal faults along its eastern and western boundaries southward the eastern boundary fault system merges with a series of splays of the wanding strike slip fault while the western boundary fault system is bent into parallelism with the wanding fault this geometric relationship suggests that the normal faulting along the eastern and western boundary of the gaoligong shear zone was caused by transfer of the ne sw left lateral movement along the wanding fault into e w extension on faults to the northeast the resultant normal faulting caused the lowering of the topography in the southern part of the shear zone fission track data from 11 samples from the mylonitic rocks in the footwall of the ruili oblique slip fault left lateral thrust slip yielded ages between 8 4 and 0 9 ma coeval with volcanism within the jietou and mangbang basins the left lateral strike slip movement along the wanding and ruili faults is interpreted to have accommodated differential clockwise rotation of the gaoligong shear zone and its adjacent tectonic units during late cenozoic to recent time during the northward movement of the indian plate with respect to the southeastern margin of the tibetan plateau along the right lateral sagaing fault

jurassic to miocene magmatism and metamorphism in the mogok metamorphic belt and the india eurasia collision in myanmar situated south of the eastern himalayan syntaxis at the western margin of the shan thai terrane the highgrade mogok metamorphic belt mmb in myanmar occupies a key position in the tectonic evolution of southeast asia the first sensitive high resolution ion microprobe u pb in zircon geochronology for the mmb shows that strongly deformed granitic orthogneisses near mandalay contain jurassic 170 ma zircons that have partly recrystallized during 43 ma high grade metamorphism a hornblende syenite from mandalay hill also contains jurassic zircons with evidence of eocene metamorphic recrystallization rimmed by thin zones of 30 9 plus or minus 0 7 ma magmatic zircon the relative abundance of jurassic zircons in these rocks is consistent with suggestions that southern eurasia had an andean type margin at that time mid cretaceous to earliest eocene 120 to 50 ma i type granitoids in the mmb myeik archipelago and western myanmar confirm that prior to the collision of india an up to 200 km wide magmatic belt extended along the eurasian margin from pakistan to sumatra metamorphic overgrowths to zircons in the orthogneiss near mandalay date a period of eocene 43 ma high grade metamorphism possibly during crustal thickening related to the initial collision between india and eurasia at 65 to 55 ma this was followed by emplacement of syntectonic hornblende syenites and leucogranites between 35 and 23 ma similar syntectonic syenites and leucogranites intruded the ailao shan red river shear belt in southern china and vietnam during the eocene oligocene to miocene and the wang chao and three pagodas faults in northern thailand that most likely link with the mmb were also active at this time the complex history of eocene to early miocene metamorphism deformation and magmatism in the mmb provides evidence that it may have played a key role in the network of deformation zones that accommodated strain during the northwards movement of india and resulting extrusion or rotation of indochina

rock relationships in the mogok metamorphic belt tatkon to mandalay central myanmar abstract the mogok metamorphic belt mmb over 1450 km long and up to 40 km wide consists of regionally metamorphosed rocks including kyanite and sillimanite schists and granites lying along the western margin of the shan plateau in central myanmar and continuing northwards to the eastern himalayan syntaxis exposures in quarries allow correlation of palaeozoic meta sedimentary early mesozoic meta igneous and late mesozoic intrusive rocks within a 230 km long northerly trending segment of the mmb from tatkon to kyanigan north of mandalay and with the mogok gemstone district 100 km to the northeast relationships among the metamorphic and intrusive rocks with sparse published radiometric age controls indicate at least two metamorphic events one before and one after the intrusion of late jurassic to early cretaceous calc alkaline rocks these relationships can be explained by either of two possible tectonic histories one constrained by correlation of mid permian limestones across myanmar requires early permian and early jurassic regional metamorphic events prior to an early tertiary metamorphism in the western part of but within a shan thai western myanmar block the second not compatible with a single laterally continuous permian limestone requires pre upper jurassic regional metamorphism and orogenic gold mineralization in the mergui group and western myanmar early cretaceous collision of an east facing mergui western myanmar island arc with the shan plateau and early tertiary metamorphism in the mmb related to reversal in tectonic polarity following the arc plateau collision

the development of an automated correction procedure for digital photogrammetry for the study of wide shallow gravel bed rivers this paper develops an automated correction procedure for dealing with point errors associated with through water photogrammetry for application in the study of clear water shallow gravel bed rivers the procedure involves combining digital photogrammetry and image analysis techniques to i correct for the effects of refraction at an air water interface and ii eliminate and reinterpolate points where the bed has not been seen the correction procedure was applied to raw digital elevation models dems generated using digital photogrammetry from 1 3000 scale aerial photography of a small reach of the north ashburton river new zealand the accuracy of corrected and uncorrected dems is evaluated using an independent data set a measure of geomorphological usefulness as well as dem external reliability is obtained from calculations of water depth distributions and mean bed level results show that digital photogrammetry used in conjunction with image analysis techniques can successfully be used for extracting high resolution dems of gravel river beds in exposed areas errors are small and random tending to cancel out over large numbers of points where water is shallow and following correction point elevation errors are statistically no different from those for exposed zones in deeper water despite an improvement following application of the correction procedure elevation errors scale with water depth the geomorphological potential of photogrammetric survey of large gravel river beds is demonstrated by the ease and accuracy of calculations of water depth distribution important for the assessment of a river s ecological and recreational characteristics and mean bed level important for the calculation of reach scale sediment volumes copyright 2000 john wiley sons ltd

paleomagnetism of peninsular malaysia abstract paleomagnetic results from upper jurassic to paleocene rocks in peninsular malaysia show counter clockwise ccw rotations while clockwise rotations cw are predominantly found in older rocks continental redbeds of the upper jurassic to lower cretaceous tembeling group have a post folding remagnetization giving a vgp at n54 e29 corresponding to approximately 40 of ccw rotation relative to eurasia and 60 ccw relative to the indochina block khorat plateau samples from cretaceous to paleocene mafic volcanics of the kuantan dike swarm and the segamat basalts give vgps at n59 e47 and n34 e36 respectively these malayasian data are indistinguishable from the late eocene and oligocene vgps reported for borneo and the celebes sea and are similar to the eocene vgps reported for southwest sulawesi and southwest palawan the occurrence of ccw deflected data over this large region suggests that much of malaysia borneo sulawesi and the celebes sea rotated approximately 30 to 40 ccw relative to the geocentric axial dipole gad between the late eocene and the late miocene although not necessarily synchronously nor as a single rigid plate these regional ccw rotations are not consistent with simple extrusion based tectonic models cw declinations have been measured in late triassic granites permian to triassic volcanics and remagnetized paleozoic carbonates the age of this magnetization is poorly understood and may be as old as late triassic or as young as middle or late cretaceous the plate or block rotations giving rise to these directions are correspondingly weakly constrained

multitemporal alsm change detection sediment delivery and process mapping at an active earthflow remote mapping and measurement of surface processes at high spatial resolution is among the frontiers in earth surface process research remote measurements that allow meter scale mapping of landforms and quantification of landscape change can revolutionize the study of landscape evolution on human timescales at mill gulch in northern california usa an active earthflow was surveyed in 2003 and 2007 by airborne laser swath mapping alsm enabling meter scale quantification of landscape change we calculate four year volumetric flux from the earthflow and compare it to long term catchment average erosion rates from cosmogenic radionuclide inventories from adjacent watersheds we also present detailed maps of changing features on the earthflow from which we can derive velocity estimates and infer dominant process these measurements rely on proper digital elevation model dem generation and a simple surface matching technique to align the multitemporal data in a manner that eliminates systematic error in either dataset the mean surface elevation of the earthflow and an opposite slope that was directly influenced by the earthflow decreased 14 1 mm yr from 2003 to 2007 by making the conservative assumption that these features were the dominant contributor of sediment flux from the entire mill gulch drainage basin during this time interval we calculate a minimum catchment averaged erosion rate of 0 30 0 02 mm yr analysis of beryllium 10 10be concentrations in fluvial sand from nearby russian gulch and the south fork gualala river provide catchment averaged erosion rates of 0 21 0 04 and 0 23 0 03 mm yr respectively from translated landscape features we can infer surface velocities ranging from 0 5 m yr in the wide upper source portion of the flow to 5 m yr in the narrow middle transport portion of the flow this study re affirms the importance of mass wasting processes in the sediment budgets of uplifting weak lithologies copyright 2011 john wiley sons ltd

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

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

significant decadal channel change 58 67 years post dam accounting for uncertainty in topographic change detection between contour maps and point cloud models abstract construction of digital elevation models dems and the subtraction of dems between different points in time as a method to determine temporal patterns of scour and fill is a highly valuable procedure emerging in geomorphology these dems of differences dods must be assessed for error in order to distinguish actual topographic change from uncertainty and surface error current methods include 1 uniformly excluding all values that fall below a minimum threshold 2 using a spatially variable approach such as the construction of minimum level of detection lod grids or 3 the creation of a fuzzy inference system although spatially variable methods for determining error have been more accurate in excluding noise without discarding large amounts of meaningful data a challenge remains in performing dods against preexisting contour based maps for which no original point data are available the goals of this study were to 1 develop a method that overcomes the unknown point density of contour and other historical data sets and allows for some assessment of dod uncertainty on the basis of information on topographic variability 2 perform comprehensive uncertainty analysis testing to understand the opportunities and constraints associated with this new method and 3 report and interpret the overall pattern and volume of decadal topographic change for a regulated river 67 years post dam in light of alternate conjectured mechanisms of post dam longitudinal profile adjustment the key feature of the new approach is the introduction of a high density artificial point grid that samples the topographic variability evident in the available historical data set the testbed used to develop and assess this new dod method was the 37 5 km lower yuba river california historical data consisted of 0 6 m contours from a 1999 survey while a more detailed point cloud was available for the most recent survey in 2006 2008 to evaluate uncertainty in the method this study applied seven different uncertainty metrics of varying strictness t 1 t 1 96 uniform 0 3 m exclusion t 1 plus uniform 0 3 m exclusion t 1 with lod minimum at 0 3 t 1 96 plus uniform 0 3 m exclusion and t 1 96 with lod minimum at 0 3 and two different dod adjustment methods exclusion and subtraction a stringent approach involving joint use of the contour half interval and the spatially distributed lod grid at a 95 confidence limit excluded 44 3 of the study area from spatial assessment of channel change and volumetric change computation this preferred approach yielded an estimated 2 518 million m 3 of total scour and 2 455 million m 3 of total fill in 7 9 years after considering different mapping epochs the net annual average export was 17 000 m 3 32 500 tons to the feather river and a river valley sediment yield of 2205 tons km 2 year this amount is 36 of the post dam annual yield of gravel and cobble to the upstream reservoir that blocks sediment conveyance into the study domain suggesting that the lowland system is still highly dynamic 67 years after the dam was built the scientific significance of this is that the response of rivers to dams can be far more long lasting and complex depending on the suite of cumulative societal impacts to rivers the ability to account for spatially explicit dod uncertainty i e data retention when uncertainty is low and data removal when uncertainty is high when comparing historic contour based and modern point cloud based dems will allow for more detailed and reliable dods and sediment budgets in these cases

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

geostatistical estimations of bathymetric lidar errors on rivers the geometry of river channels is a key descriptive element for hydromorphology hydraulics and hydroecology gravel bed rivers usually have a mean water depth of 0 5 m for such shallow waters the accuracy of bathymetric lidar data has to be precisely assessed alongside this accuracy investigation methodological questions arise how to assess the data quality of elevation lidar when comparing reference topographic points on river beds to laser beam footprints of several square metres at different locations what are the consequences of uncertainties and scaling in accuracy estimations in this study we designed a methodology to assess the quality of lidar topographical data within rivers using a specific geostatistical method that conducts upscaling as well as interpolation of reference data that takes into account uncertainties this method uses an anisotropic block kriging from dgps points on lidar footprint areas within a channel fitted coordinate system this assessment focused on a 1 5 km long reach of the gardon gravel bed river in the south of france dgps points pseudo regularly located along the river were acquired at the same time as the lidar survey with the hawkeyeii system lidar accuracy results for river bottom elevation show a negative bias for high depth added to that bias a random error with 0 32 m standard deviation was found by considering upscaling and uncertainties in reference data and a 0 20 m standard deviation was found if they were not considered consequently if lidar bias can be corrected measuring a water depth less than 32 cm i e for 28 of the river area is unrealistic however this experiment shows that lidar provides an accurate representation of the riverbed forms it also provided a useful continuous topographic surface from the underwater river bed up to riparian areas copyright 2010 john wiley and sons ltd

kinematics and ar 40 ar 39 geochronology of the gaoligong and chongshan shear systems western yunnan china implications for early oligocene tectonic extrusion of se asia the gaoligong and chongshan shear systems glss and csss in western yunnan china have similar tectonic significance to the ailaoshan red river shear system asrrss during the cenozoic tectonic development of the southeastern tibetan syntaxis to better understand their kinematics and the cenozoic tectonic evolution of se asia this paper presents new kinematic and 40 ar 39 ar geochronological data for these shear systems all the structural and microstructural evidence indicate that the glss is a dextral strike slip shear system while the csss is a sinistral strike slip shear system and both were developed under amphibolite to greenschist grade conditions the 40 ar 39 ar dating of synkinematic minerals revealed that the strike slip shearing on the glss and csss at least began at 32ma possibly coeval with the onset of other major shear systems in se asia the latestage shearing on the glss and csss is dated at 27 29ma by the biotite 40 ar 39 ar ages consistent with that of the wang chao shear zone wcsz but 10ma earlier than that of the asrrss the dextral gaoligong shear zone within the glss may have separated the india plate from the indochina block during early oligocene combined with other data in western yunnan we propose that the baoshan southern indochina block escaped faster southeastward along the csss to the east and the glss to the west than the northern indochina block along the asrrss accompanying with the obliquely northward motion of the india plate during early oligocene 28 36ma during 28 17ma the northern indochina block was rotationally extruded along the asrrss relative to the south china block as a result of continuously impinging of the india plate

monitoring and modelling morphological change in a braided gravel bed river using high resolution gps based survey recent research in fluvial geomorphology has emphasized the direct monitoring of channel topography as a useful tool to better understand the interrelationship between river form and process and in particular to estimate bedload transport rates and reach scale sediment budgets until recently however this morphometric approach has been limited to comparison of repeatedly surveyed cross sections with the associated problems of low frequency sampling and an emphasis on cross stream as opposed to downstream morphological dynamics recent advances in analytical photogrammetry have however permitted the acquisition of data at sufficient resolutions to represent macroform 101 m and microform 10 m channel geometry in fully three dimensions while inherently spatially distributed the photogrammetric approach to land surveying is however restricted to observable areas of the channel and is thus of limited use in the subaqueous zone especially if flows are turbid or highly coloured this paper presents an alternative approach to the study of three dimensional morphological dynamics of a divided reach of the gravelly river feshie scotland in which topographic survey of both exposed and submerged areas of the reach was undertaken using the global positioning system gps survey results from two field programmes in 1998 and 1999 are presented in which a geotronics geotracer 2000 real time kinematic gps receiving unit was used to survey a 200 80 m reach rapid radial survey methods were employed permitting the collection of 2000 survey points per day giving a mean density over the 13 ha reach of 1 1 points per square metre a detailed assessment of survey errors and dem quality is presented and a limit of detection of c 10 cm proposed as an upper threshold for the identification of significant change between dems preliminary interpretation of channel dynamics in 1998 99 reveals relatively little change to the overall macroscale reach structure dem differencing techniques however highlight important local changes including the progradation of submerged bar fronts bar head aggradation and scour along major channel thalwegs and the erosion of fines from sloughs copyright 2000 john wiley sons ltd

ocean plate stratigraphy in east and southeast asia abstract ancient accretionary wedges have been recognised by the presence of glaucophane schist radiolarian chert and melange recent techniques for the reconstruction of disrupted fragments of such wedges by means of radiolarian biostratigraphy provide a more comprehensive history of ocean plate subduction and successive accretion of ocean floor materials from the oceanic plate through offscraping and underplating reconstructed ocean floor sequences found in ancient accretionary complexes in japan comprise from oldest to youngest pillow basalt limestone radiolarian chert siliceous shale and shale and sandstone similar lithologies also occur in the melange complexes of the philippines indonesia thailand and other regions this succession is called ocean plate stratigraphy ops and it represents the following sequence of processes birth of the oceanic plate at the oceanic ridge formation of volcanic islands near the ridge covered by calcareous reefs sedimentation of calcilutite on the flanks of the volcanic islands where radiolarian chert is also deposited deposition of radiolarian skeletons on the oceanic plate in a pelagic setting and sedimentary mixing of radiolarian remains and detrital grains to form siliceous shale in a hemipelagic setting and sedimentation of coarse grained sandstone and shale at or near the trench of the convergent margin radiolarian biostratigraphy of detrital sedimentary rocks provides information on the time and duration of ocean plate subduction the ages of detrital sediments becomes younger oceanward as younger packages of ops are scraped off the downgoing plate ops reconstructed from ancient accretionary complexes give us the age of subduction and accretion direction of subduction and ancient tectonic environments and is an important key to understanding the paleoenvironment and history of the paleo oceans now represented only in suture zones and orogenic belts

tectonic amalgamation of the gaoligong shear zone and lancangjiang shear zone southeast of eastern himalayan syntaxis abstract the gaoligong shear zone glgsz and lancangjiang shear zone lcjsz are two major large scale shear zones southeast of eastern himalayan syntaxis ehs and play important roles in the accommodation of the intracontinental deformation in southeast asia the two shear zones which are mainly composed of high grade metamorphic rocks and have long been regarded as the precambrian basement of this area are gradually merged northward and become tectonically amalgamated from fugong to gongshan area structural and kinematic analyses reveal that the amalgamation area has experienced strongly partitioned dextral transpression n s trending tight to isoclinal folds sub vertical foliation and sub horizontal lineation are ubiquitously developed both within the shear zones and the carboniferous flysch sediments of baoshan block in between micro and macro kinematic indicators such as cs structures rotated porphyroclasts asymmetric shear folds sheath folds domino and boudin structures suggest that the shear sense of the glgsz and lcjsz is dextral in the amalgamation area comparative analyses of strata reveal that the baoshan block is aligned with south qiangtang block and the lanping simao block was aligned with north qiangtang block prior to the cenozoic large scale tectonic extrusion and rotation the amalgamation area which has progressively switched positions from northeast of ehs to east and southeast of ehs is just located at the neck of the large scale boudin of south qiangtang baoshan block a boudin model is proposed for the tectonic amalgamation of the glgsz and lcjsz from fugong to gongshan area in response to the continued northward convergence between indian plate and eurasian plate since early eocene resistance of south china block southeastward extrusion and clockwise rotation of baoshan block around ehs

understanding sibumasu in the context of ribbon continents abstract well described ribbon continent collision belts and modern examples with 2d seismic coverage particularly zealandia provide analogues for the permo triassic development of sibumasu two key parameters for the ribbon continents are their width and how rifting developed which in turn impact the structural metamorphic igneous and stratigraphic development of ribbon continents in ways that make them significantly different from the collisional development of major continents key characteristics of the tectonics of sibumasu are 1 a tendency towards basin inversion during the late triassic and possibly early jurassic and mixed thick skinned and thin skinned style deformation 2 extensional collapse around 215 ma is an important feature of sibumasu particularly in northern thailand and probably other areas too 3 slab delamination and extension related decompression melting were probably important mechanisms for generating granites in addition to crustal thickening 4 metamorphism is relatively high temperature lower pressure

multiple alternating forearc and backarc ward migration of magmatism in the indo myanmar orogenic belt since the jurassic documentation of the orogenic architecture of eastern neotethys in se asia abstract we integrated our new data with a review of published work on the indo myanmar orogenic belt imob of the eastern neotethys in myanmar western yunnan china and naga hills india in order to better understand subduction accretion processes of the neotethys ocean in se asia and interactive relationships between the gondwana and laurasia supercontinents from east to west the imob is divided into three geographic units the shan thai plateau myanmar central basin and indo burma range the mogok metamorphic and slate belt is within the shan thai plateau the shan thai plateau and eastern myanmar central basin contain paleozoic sedimentary successions low grade to amphibolitic facies metamorphic rocks and the luxi ultramafic and myitkyina mogok ultramafic diorite belts unmetamorphosed and metamorphosed sediments have similar detrital zircon age peaks of 1000 ma and 700 ma or 500 ma and they are separated by the luxi ultramafic belt whose end 0 and 87sr 86sr i values are similar to surrounding granite diorite and migmatite and the os 4 8 8 8 is indicative of old sub continental lithospheric mantle rather than an oceanic suture zone these data and relations suggest that these regions belong to the cimmerian continental sliver derived from the gondwana supercontinent the myitkyina mogok ultramafic diorite belt located along the eastern margin of the myanmar central basin that was associated with the continental sliver contains peridotite andesite hornblende gabbro diorite granodiorite and plagiogranite all with arc geochemical signatures and ages of 177 166 ma the source region of some of these igneous rocks contains a component of em1 which is close to low 87sr 86sr i ratio of a migmatite in the cimmerian continental sliver as shown by sr nd isotopes values suggesting this belt developed as a jurassic continental margin arc the mogok metamorphic and slate belt contains granodiorite diorite tonalite granite and migmatite extending from the gongshan tengchong and luxi areas in western yunnan china to mandalay kalaw padatchaung and moulmein in myanmar these rocks have arc geochemical character and yield ages of 185 170 ma 128 112 ma 91 ma and 75 45 ma suggesting development of four episodes of arc magmatism along the central axis of the myanmar central basin there are magmatic arc related 106 94 ma diorite granodiorite and tonalite as well as eocene and neogene present 38 0 ma andesite dacite trachyte and rhyolite accretion took place along the central axis of the myanmar central basin towards the indo burma range and westward to the present trench axis on the margin of the indian ocean as shown by westward younging of accretionary complexes and trench slope basins a jurassic accretionary complex located in the hpakan area in the north of the myanmar central basin contains 189 147 ma high pressure metamorphic rocks such as jadeitite garnet mica schist and glaucophane schist in the eastern belt of the indo burma range early cretaceous 119 115 ma accretionary complexes consist of upper plate triassic unmetamorphosed and low grade metamorphic sediments and lower plate amphibolites high pressure metamorphic rocks and jurassic early cretaceous oceanic plate stratigraphy containing morb and oib type basalts and thin bedded radiolarian cherts late early cretaceous 100 ma and late cretaceous to middle eocene 75 45 ma trench slope basin deposits containing abundant fossil plants and shallow water sedimentary structures cover most of the indo burma range where sediments rest with an angular unconformity on older accretionary complexes the presence of earlier magmatic arcs accretionary complexes and trench slope basins suggests that the present trench on the margin of the indian ocean has evolved by continuous eastward subduction since the jurassic the magmatic arc axis migrated eastward landward during some time periods jurassic to early cretaceous and late cretaceous to middle eocene and westward seaward migration during others early cretaceous to late early cretaceous and middle eocene to present during continuous east dipping subduction

neo tethyan magmatism and metallogeny in myanmar an andean analogue abstract plate margin tectonism magmatic and hydrothermal processes and the genesis of mineral deposits are intricately linked in myanmar two near parallel magmatic belts that together contain a significant proportion of that country s mineral wealth have contrasting metallogenic endowments the mogok mandalay mergui belt hosts crustal melt s type granites with significant tin tungsten mineralization while the wuntho popa arc comprises i type granites and granodiorites with copper gold mineralization the spatial juxtaposition of the two belts and their distinct but consistent metallogenic endowment bears strong similarities to the metallogenic belts of the south american cordillera recent u pb age dating has shown the potential for the two belts to be near contemporary from the late cretaceous to eocene here we investigate whether an andean type setting during subduction of neo tethys could explain the observed magmatism and mineralization within these two belts

modeling river bed morphology roughness and surface sedimentology using high resolution terrestrial laser scanning 1 recent advances in technology have revolutionized the acquisition of topographic data offering new perspectives on the structure and morphology of the earth s surface these developments have had a profound impact on the practice of river science creating a step change in the dimensionality resolution and precision of fluvial terrain models the emergence of hyperscale survey methods including structure from motion photogrammetry and terrestrial laser scanning tls now presents the opportunity to acquire 3 d point cloud data that capture grain scale detail over reach scale extents translating these data into geomorphologically relevant products is however not straightforward unlike traditional survey methods tls acquires observations rapidly and automatically but unselectively this results in considerable noise associated with backscatter from vegetation and other artifacts moreover the large data volumes are difficult to visualize require very high capacity storage and are not incorporated readily into gis and simulation models in this paper we analyze the geomorphological integrity of multiscale terrain models rendered from a tls survey of the braided river feshie scotland these raster terrain models are generated using a new computationally efficient geospatial toolkit the topographic point cloud analysis toolkit topcat this performs an intelligent decimation of point cloud data into a set of 2 5 d terrain models that retain information on the high frequency subgrid topography as the moments of the locally detrended elevation distribution the results quantify the degree of terrain generalization inherent in conventional fluvial dems and illustrate how subgrid topographic statistics can be used to map the spatial pattern of particle size grain roughness and sedimentary facies at the reach scale

the phuket terrane a late palaeozoic rift at the margin of sibumasu abstract it is widely accepted that sibumasu rifted from gondwana in the late palaeozoic but the rifts themselves have not previously been documented in southeast asia this paper identifies the pre middle permian kaeng krachan group of upper peninsular thailand as the infill of one such rift which is given the name phuket terrane indirect evidence suggests the rift infill is several kilometres thick and glacially influenced diamictites are conspicuous in the succession there are significant similarities with the 3 km thick pre middle permian rift infill of the carnarvon basin of western australia east of the khlong marui fault belt the succession is thinner and diamictites are a minor component a tectono stratigraphic model is proposed involving gondwana glaciers dropping their load at the present western margin of the phuket terrane from where it was re sedimented in the rapidly subsiding marine rift basin it is suggested that the khlong marui fault formed part of the eastern boundary of the rift system the three pagodas fault belt similarly juxtaposes different pre middle permian successions rifting ceased in the early permian and a passive margin formed as the mesotethys ocean widened the upper part of the kaeng krachan group and the overlying ratburi limestone representing the post rift sequence

first records of early permian conodonts from eastern myanmar and implications of paleobiogeographic links to the lhasa block and northwestern australia abstract an early permian cisuralian conodont fauna is reported for the first time from the sibumasu terrane in eastern myanmar the conodont fauna includes vjalovognathus nicolli and typical mesogondolella idahoensis some m idahoensis possess transitional characters with m lamberti and m siciliensis this fauna indicates a late kungurian age the longest range of the taungnyo group was from late tournaisian to late kungurian and the range of the overlying moulmein limestone might be from late kungurian through guadalupian middle permian the nearly synchronous occurrence of identical conodont faunas from eastern myanmar the lhasa block and northwestern australia provides important evidence that these tectonic units had a close paleogeographic paleobiogeographic and paleoclimatic evolution during the late cisuralian the occurrence of this conodont fauna across the continuous boundary interval between the taungnyo group and moulmein limestone might indicate a paleoclimatic transition from early permian cool water conditions to a middle to late permian warm water setting due to tectonic drifting of the relevant blocks and or paleoclimatic amelioration after the late paleozoic ice age lpia from carboniferous to cisuralian this discovery also suggests that the terranes in eastern myanmar are complicated by subsequent tectonic mergence and possibly of multiple origins based on the conodont and fusuline faunal affinities in different areas of eastern myanmar

methodological sensitivity of morphometric estimates of coarse fluvial sediment transport abstract the estimation of fluvial sediment transport rate from measurements of morphological change has received growing recent interest the revival of the morphological method reflects continuing concern over traditional methods of rate determination but also the availability of new survey methods capable of high precision high resolution topographic monitoring remote sensing of river channels through aerial digital photogrammetry is a potentially attractive alternative to labour intensive ground surveys however while photogrammetry presents the opportunity to acquire survey data over large areas data precision and accuracy particularly in the vertical dimension are lower than in traditional ground survey methods this paper presents results of recent research in which digital elevation models dems have been developed for a reach of a large braided gravel bed river in scotland using both digital photogrammetry and high resolution rtk gps ground surveys a statistical level of change detection is assessed by comparing surfaces with independent check points the methodological sensitivity of the annual channel sediment budget 1999 2000 to the threshold is presented results suggest that while the remote survey methods employed here can be used to develop qualitatively convincing moderate precision dems of channel topography rmse 0 21 m the remaining errors imply significant limits on reliable change detection which lead to important information losses tests at a 95 confidence interval for change detection show that over 60 of channel deposition and 40 of erosion may be obscured by the lower level of precision associated with photogrammetric monitoring when compared to ground survey measurements this bias reflects the difficulty of detecting the topographic signature of widespread but shallow deposition on bar tops

the bentong raub suture zone abstract it is proposed that the bentong raub suture zone represents a segment of the main devonian to middle triassic palaeo tethys ocean and forms the boundary between the gondwana derived sibumasu and indochina terranes palaeo tethyan oceanic ribbon bedded cherts preserved in the suture zone range in age from middle devonian to middle permian and melange includes chert and limestone clasts that range in age from lower carboniferous to lower permian this indicates that the palaeo tethys opened in the devonian when indochina and other chinese blocks separated from gondwana and closed in the late triassic peninsular malaysia segment the suture zone is the result of northwards subduction of the palaeo tethys ocean beneath indochina in the late palaeozoic and the triassic collision of the sibumasu terrane with and the underthrusting of indochina tectonostratigraphic palaeobiogeographic and palaeomagnetic data indicate that the sibumasu terrane separated from gondwana in the late sakmarian and then drifted rapidly northwards during the permian triassic during the permian subduction phase the east malaya volcano plutonic arc with i type granitoids and intermediate to acidic volcanism was developed on the margin of indochina the main structural discontinuity in peninsular malaysia occurs between palaeozoic and triassic rocks and orogenic deformation appears to have been initiated in the upper permian to lower triassic when sibumasu began to collide with indochina during the early to middle triassic a type subduction and crustal thickening generated the main range syn to post orogenic granites which were emplaced in the late triassic early jurassic a foredeep basin developed on the depressed margin of sibumasu in front of the uplifted accretionary complex in which the semanggol formation rocks accumulated the suture zone is covered by a latest triassic jurassic and cretaceous mainly continental red bed overlap sequence

combined effects of eurasia sunda oblique convergence and east tibetan crustal flow on the active tectonics of burma it is widely accepted that deformation of the india sunda plate is the result of partitioned hyper oblique convergence presently sub meridian dextral strike slip faulting accommodates this india sunda motion in a buffer zone the burma platelet this wide dextral strike slip shear zone is complicated by the side effect of the tibet plateau collapse that can be described in term of crustal flow and gravity tectonics the loss of potential energy related to this plateau collapse affects most of the burmese platelet particularly in its northernmost part interaction of these two distinct geodynamic processes is recorded in the gps based regional strain field the analysis of seismic focal mechanism but also from direct geologic observations both onshore and offshore myanmar and bangladesh we propose the apparent e w shortening component of this so called partitioned hyper oblique subduction is only the effect of regional gravitational forces related to the tibet plateau collapse whereas the ns strike slip faulting accommodates the india sunda motion

early cretaceous highly fractionated i type granites from the northern tengchong block western yunnan sw china petrogenesis and tectonic implications abstract western yunnan an important constituent of the southeastern segment of the east tethyan tectonic domain lies along a transformed orientation from the nww trending himalayan tethyan segment to the northerly trending southeast asian segment however the geodynamical setting of the early cretaceous tectonothermal magmatism along the bangong nujiang lushui luxi ruili belt as the tethyan branch in western yunnan sw china remains controversial the donghe granitoid which is located between the gaoligong and tengliang belts in the northern tengchong block reveals its petrogenesis and its tectonics both of which play a vital role in resolving previous disputes our zircon laser ablation inductively coupled plasma mass spectrometry u pb dating of granites from the donghe batholith yields ages of 119 9 0 9 130 6 2 5 ma these granites display features typical of highly fractionated i type granites high sio 2 contents 71 wt high k contents k 2 o 3 88 5 66 wt calc alkaline character slight peraluminosity a cnk 1 02 1 16 and a highly differentiated index ranging from 83 6 to 95 6 in addition as sio 2 contents increase the rare earth element ree abundances especially heavy ree abundances and ree pattern slopes change gradually but the negative eu anomalies increase sharply while the degree of enrichment in rb th u and pb and depletion in ba nb sr p and ti are enhanced these features indicate that k feldspar plagioclase biotite amphibole apatite sphene garnet and fe ti oxides such as ilmenite play the major role in the fractional crystallization process the high initial 87 sr 86 sr 0 7067 and 0 7079 and negative e nd t values 8 6 to 10 1 with t 2dm ranging from 1 39 to 1 49 ga indicate that the sources were mainly derived from the mature ancient middle to lower crust and minor mantle derived materials the initial 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb ratios of 18 462 18 646 15 717 15 735 and 38 699 39 007 respectively signify that some subduction related material such as ocean island volcanic rocks and mature arc primitive rocks may be involved as sources based on an analysis of similar zircon saturated temperature and geochemical characteristics of typical highly fractionated i type granites in se and sw china and consideration of the regional geological setting we suggest that the parent magma may be derived from the ancient middle to lower continental crust and mantle derived basaltic magma these were generated in the setting of a westward subducted lushui luxi ruili llr tethyan oceanic slab where mantle wedge derived sources provided enough heat and material to melt the middle to lower ancient crust taking into account the temporal spatial distributions of early cretaceous magmatic rocks in the region we further suggest the existence of an andean type active continental margin from the lhasa block to the tengchong block along the bangong nujiang llr tethys ocean during the early cretaceous

the upper paleozoic pebbly mudstone facies of peninsular thailand and western malaysia continental margin deposits of paleoeurasia reply the phuket group in peninsular thailand and the singha formation in nw malaysia are of devonian to lower permian age these approximately 3000 m thick strata which are part of the se asian pebbly mudstone belt stretching from southern tibet to sumatra have been interpreted as continental margin deposits mitchell et al 1970 in contrast recent papers bunopas et al 1978 stauffer 1983 propose a glaciomarine origin these authors follow the scenario that parts of mainland se asia shan thai craton rifted away from gondwana during the lower carboniferous and collided with eurasia during the late triassic after crossing the tethys ocean under clockwise rotation of more than 180 degrees in this paper the arguments of these authors will be discussed and a sedimentological description will be given which shows that the pebbly mudstones are not glaciomarine sediments but rather of continental margin origin the investigations on phuket and langkawi islands when compared with newest results from central and north thailand clearly show that the shan thai craton was a part of or closely connected with palaeoeurasia indosinia during carboniferous and permian times comp helmcke 1985 the pebbly mudstones were deposited on the southern continental margin of this continent northern margin of tethys

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

mapping hydraulic biotopes using terrestrial laser scan data of water surface properties for more than a decade habitat mapping using biotopes in channel hydraulically defi ned habitats has underpinned aquatic conservation in the uk through a providing baseline information on system complexity and b allowing environmental and ecological change to be monitored and evaluated the traditional method used is the subjective river habitat or corridor survey this has recently been revised to include the fl oodplain via georhs but issues still exist concerning development of a national database due to the labour intensive nature of the data collection subjectivity issues between samplers temporal changes the fuzzy nature of perceived habitats and habitat boundaries this paper takes an innovative approach to biotope defi nition using high resolution spatial data to defi ne water surface roughness for two representative reaches of the river south tyne cumbria and the river rede northumberland uk data was collected using a terrestrial laser scanner tls and hydraulic variability simply expressed through assigning a local standard deviation value to a set of adjacent water surface values statistical linkage of these data with biotope locations defi ned visually in the fi eld allowed complete mapping of the surveyed reach defi ning habitat and biotope areas to the fi ne scale resolution of the tls data despite issues of data loss due to absorption and transmission through the water the refl ected signal generated an extremely detailed and objective map of the water surface roughness which may be compared with known biotope locations as defi ned by visual identifi cation in the fi eld the tls accuracy achieved in the present study is comparable with those obtained using hyperspectral imagery with 84 of the pool glide marginal deadwater amalgamated biotope 88 of riffl es 57 of runs and 50 of the amalgamated cascade rapid biotope successfully plotted it is clear from this exercise that biotope distribution is more complex than previously mapped using subjective techniques and based upon the water surface roughness delimiters presented in this study the amalgamation of pools with glides and marginal deadwaters riffl es with unbroken standing waves and cascades with rapids is proposed

geochemistry and nd isotopic composition of the permian ko sire formation phuket island thailand implications for palaeoclimate and palaeogeographical configuration of the sibumasu terrane the sibumasu terrane is a continental block in se asia that is considered to have been attached to gondwana before its collision with indochina during the triassic the elemental geochemistry and sm nd isotopic composition of mudrocks from the lower permian ko sire formation of the phuket group on phuket island central sibumasu terrane thailand were analysed to investigate its provenance weathering history and palaeogeographical location prior to its separation from gondwana the whole rock elemental geochemistry identified a felsic granodioritic source rock which is consistent with the general consensus regarding gondwanan sediment provenance despite the evidence for sediment recycling such as abundant dropstone clasts derived from sedimentary rocks the low degree of chemical weathering and lack of zircon enrichment indicate a cold and arid palaeoclimate in its source area which resulted in ice rafted transportation of clasts and suspension deposition of fine grained clastic sediments sm nd isotopic data and previously published detrital zircon u pb age spectra provide more detailed information on the source rock composition which was similar to that of the north australian crustal element suggesting that the central sibumasu terrane was located on the northern margin of north australia during the late paleozoic supplementary material a table of trace element concentrations is available at https doi org 10 6084 m9 figshare c 4877289

step by step error assessment in braided river sediment budget using airborne lidar data abstract sequential airborne lidar surveys were used to reconstruct the sediment budget of a 7 km long braided river channel in southeastern france following a 14 year return period flood and to improve its accuracy step by step data processing involved i surface matching of the sequential point clouds ii spatially distributed propagation of uncertainty based on surface conditions of the channel and iii water depth subtraction from the digital elevation models based on water depths measured in the field the respective influence of each processing step on sediment budget computation was systematically documented this showed that surface matching and water depth subtraction both have a considerable effect on the net sediment budget although dem of difference thresholding based on uncertainty analysis on absolute elevation values had a smaller effect on the sediment budget this step is crucial for the production of a comprehensive map of channel deformations a large independent data set of rtk gps checkpoints was used to control the quality of the lidar altimetry the results showed that high density 7 9 points m 2 airborne lidar surveys can provide a very high level of detection of elevation changes on the exposed surfaces of the channel with a 95 confidence interval level of detection between 19 and 30 cm change detection from lidar data revealed that 54 of the pre flood active channel was reworked by the flood the braided channel pattern was highly disturbed by the flood owing to the occurrence of several channel avulsions

carboniferous permian facies and tectono stratigraphic successions of the glacially influenced and rifted carnarvon basin western australia abstract the carnarvon basin of western australia is a rift basin that contains a thick up to 5 km succession of late carboniferous early permian glacially influenced marine sedimentary strata these rocks accumulated in near polar paleolatitudes along the uplifted and glaciated margin of the west australian shield pilbara craton three stratigraphic successions i ii iii can be recognised each characterised by distinct facies associations that record different stages in the tectonic evolution of the basin and associated changes in the rate of basin subsidence and sediment accommodation a lowermost succession i comprises rapidly deposited 30 m ma glacially influenced marine strata lyons group containing palynomorphs of westphalian tastubian early sakmarian and possibly older age strata are dominated by subaqueously deposited sediment gravity flow facies succession ii is composed of richly fossiliferous cool water shales callythara and cordalia formations that record much reduced sedimentation rates 2 m ma in turn shales are overlain by an uppermost succession iii of shallow marine wave and storm influenced sandstone moogooloo sandstone comparison with other rift basin fills indicates that succession i likely records initial basin infilling where abundant coarse debris was produced by faulting and glaciation of the adjacent pilbara craton shales of succession ii mark a phase of sediment underfilling characterized by rapid tectonic subsidence an increase in relative sea level and reduced sediment supply shallow water sandstone facies of succession iii record a late stage in the tectonic cycle when subsidence rates had decreased and sediment supply outpaced accommodation such successions where found in other late paleozoic basins are widely interpreted in terms of glacioeustatically driven changes in sea level resulting from deglaciation events across gondwana instead the three successions within the carnarvon basin are argued to reflect a dominantly tectonic control on sedimentation and preservation

models of glaciomarine sedimentation and their application to the interpretation of ancient glacial sequences abstract this paper argues that glaciomarine environments can be regarded as special glacially influenced types of continental margin environments e g continental shelf slope rise and basin plain knowledge of the stratigraphic architecture and typical sedimentary sequences of non glacial margins is becoming well known but remains limited for those that have been glacially modified the principal influences on sedimentation in these environments relate to the glacial sediment input controlled by relief of basin margin glacier thermal regime and ice flow dynamics and depositional environments influence of traction currents substrate relief and proximity to nearby ice margins typical ranges of sedimentation rates can be established for glacially influenced continental margin environments and these may provide a framework for ancient sequences starvation of sediment supply to glacially influenced continental margins is common the nature of sub ice shelf sedimentation a model that has been applied to many ancient glacial sequences is critically reviewed the significance of such sedimentation in the rock record has probably been exaggerated because of oversimplistic interpretations of diamictite sequences existing process models of glaciomarine sedimentation derived from study of modern environments are sometimes difficult to employ in investigation of ancient sedimentary sequences because simple lithofacies criteria and typical vertical profiles are not available to aid in interpretation in addition compositional data emphasized by many workers for distinguishing glaciomarine from continental glacial diamict ite s frequently fingerprint sediment source and not mode of deposition the importance of facies analysis methods for isolating depositional environments is illustrated by three examples of ancient glaciomarine sequences these are the early proterozoic gowganda formation 2 3 ga of northern ontario canada the late proterozoic port askaig formation 670 ma of scotland and ireland and the late cenozoic yakataga formation 20 ma to recent of the gulf of alaska these examples illustrate the significance of detailed genetic studies of ancient glacial rocks in the interpretation of palaeogeographic and tectonic settings diamictite units in ancient glaciomarine sequences cannot be easily interpreted in terms of climatic or ice advance retreat cycles because of the varied controls on diamict accumulation and diamictite preservation in marine basins

tectonics and history of the andaman sea region abstract the andaman sea is an active backarc basin lying above and behind the sunda subduction zone where convergence between the overriding southeast asian plate and the subducting australian plate is highly oblique the effect of the oblique convergence has been formation of a sliver plate between the subduction zone and a complex right lateral fault system the late paleocene collision of greater india and asia with approximately normal convergence started clockwise rotation and bending of the northern and western sunda arc the initial sliver fault which probably started in the eocene extended through the outer arc ridge offshore from sumatra through the present region of the andaman sea into the sagaing fault with more oblique convergence due to the rotation the rate of strike slip motion increased and a series of extensional basins opened obliquely by the combination of backarc extension and the strike slip motion these basins in sequence are the mergui basin starting at 32 ma the conjoined alcock and sewell rises starting at 23 ma east basin separating the rises from the foot of the continental slope starting at 15 ma and finally at 4 ma the present plate edge was formed alcock and sewell rises were separated by formation of the central andaman basin and the faulting moved onshore from the mentawai fault to the sumatra fault system bisecting sumatra

subaqueous mass flow origin for lower permian diamictites and associated facies of the grant group barbwire terrace canning basin western australia the intracratonic canning basin is western australia s largest sedimentary basin 400 000 km2 and has experienced repeated episodes of phanerozoic extension and subsidence resulting in deposition of a number of first order megasequences a major phase of basin extension and sedimentation grant group occurred in the late carboniferous early permian when australia lay at high palaeolatitudes facies analysis of 5000 m of drill core from 25 continuously cored wells in grant group strata on the fault bounded barbwire terrace in the northern canning basin identified three facies associations fas these record the predominance of fault generated subaqueous mass flow and sediment reworking the lowest association fa i up to 355 m thick rests unconformably on tilted older strata and consists of coarse grained subaqueously deposited sediment gravity flow facies these include fault generated breccias massive and graded sandstones and conglomerates deposited by turbidity currents and diamictites generated by mixing of different textural populations during downslope remobilization fa i is overlain abruptly by relatively fine grained deposits of fa ii up to 140 m thick which consist of laminated to thin bedded mudstone and sandstone turbidites recording an abrupt increase in relative water depths in turn these facies coarsen upwards and are transitional into shallow water swaley cross stratified and rippled sandstones of fa iii up to 125 m thick the overall stratigraphic succession probably records an initial phase of faulting and accommodation of coarse sediment fa i a subsequent phase of rapid subsidence increasing water depths and sediment underfilling fa ii and finally a regressive phase of shoreface progradation the occurrence of rare striated clasts in fa i suggests reworking of glacial sediment but no direct glacial influence on sedimentation can be identified

rock falls in high alpine rock walls quantified by terrestrial lidar measurements a case study in the mont blanc area 1 the global warming observed in recent decades and its future increase may affect permafrost distribution on high mountain faces with consequences for their stability in this paper we show that rock falls from high alpine rock walls can be computed with a decimetre resolution using lidar measurements a laser scanner was used to create point clouds and triangulated irregular network models on the east face of the tour ronde at 3792 m asl mont blanc massif comparison of the models realised from measurements of july 2005 and july 2006 enabled quantification of rock falls with reduced uncertainty the volume of rock fall reached a total of 536 m3 in the scanned area which matches an erosion rate of 8 4 mm yr 1 this rate slightly higher to the ones reported in former studies enable to assume that this rock fall may be the consequence of the permafrost degradation in this rock face

the timing of strike slip shear along the ranong and khlong marui faults thailand 1 the timing of shear along many important strike slip faults in southeast asia such as the ailao shan red river mae ping and three pagodas faults is poorly understood we present 40ar 39ar u pb shrimp and microstructural data from the ranong and khlong marui faults of thailand to show that they experienced a major period of ductile dextral shear during the middle eocene 48 40 ma centered on 44 ma which followed two phases of dextral shear along the ranong fault before the late cretaceous 81 ma and between the late paleocene and early eocene 59 49 ma many of the sheared rocks were part of a pre kinematic crystalline basement complex which partially melted and was intruded by late cretaceous 81 71 ma and early eocene 48 ma tin bearing granites middle eocene dextral shear at temperatures of 300 500 c formed extensive mylonite belts through these rocks and was synchronous with granitoid vein emplacement dextral shear along the ranong and khlong marui faults occurred at the same time as sinistral shear along the mae ping and three pagodas faults of northern thailand a result of india burma coupling in advance of india asia collision in the late eocene 37 ma the ranong and khlong marui faults were reactivated as curved sinistral branches of the mae ping and three pagodas faults which were accommodating lateral extrusion during india asia collision and himalayan orogenesis

middle permian foraminifers from the zhabuye and xiadong areas in the central lhasa block and their paleobiogeographic implications abstract two new middle permian foraminifer faunas are described from the xiala formation in the zhabuye and xiadong sections in the central lhasa block the presence of some significant taxa in paleobiogeography such as shanita lysites biconcavus hemigordiopsis subglobosa indicates that the lhasa block was in the cimmerian province in paleobiogeography during the middle permian furthermore the nankinella chusenella fusuline assemblage that occurs in the upper part of the xiala formation in the xiadong section resembles contemporaneous fusuline faunas from the xainza and bashor areas in the lhasa block and the northern part of the tengchong block the endemism of the nankinella chusenella assemblage in the lhasa and tengchong blocks indicates that these two blocks were isolated from both the south qiangtang block and the northern gondwanan margin during the middle permian it further suggests that both the bangong nujiang ocean and the neotethys ocean would have opened before the middle permian a new species chusenella tsochenensis sp nov was described

filtering spatial error from dems implications for morphological change estimation abstract scour and fill estimation from digital elevation model dem subtraction or differencing is an increasingly common technique in morphological and sediment transport investigations the technique is commonly used to estimate scour and fill volumes and to produce scour and fill maps that provide process based information to geomorphologists accounting for sources of uncertainty within the dem is of critical importance dem error is spatially variable and has a tendency to be greater at breaks of slope such as bar and bank edges in the past however this has been achieved using a uniform error metric across the dem resulting in over conservative estimates of error in turn this has led to over conservative scour and fill volumes and incorrect process interpretation this paper applies a new approach that permits assessment of spatially distributed error across a dem the method is tested on a sequence of field surveys of the gravel bed river nent cumbria uk the results demonstrate some dramatic differences application of conventional techniques that account for mean error across a dem led to a 15 and 31 underestimation in scour and fill volumes respectively between july and october 1998 whilst for the october 1998 june 1999 subtraction 31 and 13 of scour and fill were underestimated respectively use of a uniform error across a surface captures less change in comparison to a spatially distributed approach furthermore the changes captured using a uniform error are biased toward areas of the channel that have more local topographic variability such as bar and bank edges in contrast the use of a spatially distributed approach provides information on change from flatter surfaces such as bar tops that would otherwise be missed this study also demonstrates that estimates of morphological change can be misleading in the absence of an error filter where the raw survey data is available it is recommended that sediment budgeting studies take account of the spatial variability of error in each dem involved in the subtraction

early cretaceous wedge extrusion in the indo burma range accretionary complex implications for the mesozoic subduction of neotethys in se asia the indo burma range ibr of myanmar the eastern extension of the yarlung tsangpo neotethyan belt of tibet in china contains melanges with serpentinite greenschist facies basalt chert sericite schist silty slate and unmetamorphosed triassic sandstone mudstone and siltstone interbedded with chert in the east and farther north high pressure blueschist and eclogite blocks in the naga hills melange our detailed mapping of the mindat and magwe sections in the middle ibr revealed a major 18 km antiformal isocline in a melange in which greenschist facies rocks in the core decrease in grade eastwards and westwards symmetrically outwards to lower grade sericite schist and silty slate and at the margins to unmetamorphosed sediments and these metamorphic rocks are structurally repeated in small scale imbricated thrust stacks in the mindat section the lower western boundary of the isoclinal melange is a thrust on which the metamorphic rocks have been transported over unmetamorphosed sediments of the triassic pane chaung group and the upper eastern boundary is a normal fault these relations demonstrate that the ibr metamorphic rocks were exhumed by wedge extrusion in a subduction generated accretionary complex along strike to the north in the naga hills is a comparable isoclinal melange in which central eclogite lenses are succeeded outwards by layers of glaucophane schist and glaucophanite and to lower grade greenschist facies sericite schist and slate towards the margins in the natchaung area from west to east unmetamorphosed triassic sediments overlie quartzites sericite schists actinolite schists and meta volcanic amphibolites derived from morb type basalt which are in fault contact with peridotite olivine in the peridotite has undulatory extinction suggesting deformation at 600 700 c similar to the peak temperature of the amphibolite these relations suggest generation in a metamorphic sole the amphibolites have u pb zircon ages of 119 3 ma and 115 ma which are close to the zircon ages of nearby calc alkaline granite and diorite which belong to an active continental margin arc that extends along the western side of the shan thai block the ibr accretionary complex and the active continental margin arc were generated during early cretaceous 115 128 ma subduction of the neotethys ocean

the topographic signature of vegetation development along a braided river results of a combined analysis of airborne lidar color air photographs and ground measurements 1 this paper combines archived remotely sensed data airborne lidar and digital color air photographs with nonsynchronous ground observations including observations of topographic form and vegetation cover and growth to test the hypothesis that colonization of exposed river sediments by riparian trees has an impact on channel form and to quantify any impact that is identified this is achieved along a 21 km reach of the braided gravel bed tagliamento river in northeast italy where the width of the braided corridor typically exceeds 800 m lidar data are analyzed to extract a 2 m resolution digital evolution model dem and determine riparian vegetation extent height and structure within the active corridor aerial photographs are used to map the topography of the submerged parts of the corridor these data are divided into 1 km length subreaches which possess strong contrasts in vegetation height and extent joint analysis of vegetation and morphological properties of these subreaches reveals significant associations between vegetation properties and reach morphology residuals from a gamma function fitted to the topographic data for each subreach show a good fit with poorly vegetated reaches but a weakening fit with increasing vegetation cover largely as a result of the appearance of secondary peaks in the elevation frequency distribution associated with the heavily vegetated areas furthermore the overall skewness and kurtosis of the elevation frequency distribution within each of the subreaches are both significantly correlated with vegetation extent height median elevation and growth rate indicating a clear topographic signature of vegetation development along this braided river that reflects sediment accumulation within and around the vegetated patches

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

enrichment of arsenic lead and antimony in balingian coal from sarawak malaysia modes of occurrence origin and partitioning behaviour during coal combustion abstract the concentrations of mineral forming elements and trace elements in coal and coal ashes from balingian coalfield sarawak malaysia were assayed and their modes of occurrence enrichment origin and partitioning behaviour during coal combustion were studied as well balingian coal is high in as cu pb sb th and zn of particular concern are as as high as 181 ppm pb 325 ppm and sb 96 ppm all of which are highly enriched in balingian coal relative to their respective coal clarke values arsenic pb and sb in the coal are mostly organic and to a lesser extent they are bound to discrete minerals in the form of aluminosilicates during coal combustion in the power plant a substantial portion of organically associated as pb and sb in the coal vaporize and are released into the atmosphere whereas ba and mn are highly enriched in the coal ashes as compared to the raw coal the as pb and sb anomalies observed in balingian coal may be related to a large sb as and probably pb mineralization in the vicinity of the coalfield with some localised epigenetic infiltration of these elements from the surrounding rocks by circulating groundwaters

tectonic evolution of the sibumasu indochina terrane collision zone in thailand and malaysia constraints from new u pb zircon chronology of se asian tin granitoids three principal granite provinces are defined across se asia as follows 1 the western thailand myanmar burma province consists of hornblende biotite i type granodiorite granites and felsic biotite k feldspar garnet tourmaline granites associated with abundant tin mineralization in greisen type veins new ion microprobe u pb dating results from phuket island show zircon core ages of 212 2 and 214 2 ma and a thermal overprint with rims of 81 2 1 2 and 85 75 ma 2 the north thailand west malaya main range province has mainly s type biotite granites and abundant tin mineralization resulting from crustal thickening following collision of the sibumasu plate with indochina during the mid triassic biotite granites around kuala lumpur contain extremely u rich zircons up to 38000 ppm that yield ages of 215 7 and 210 7 ma 3 the east malaya province consists of dominantly permian triassic i type hornblende biotite granites but with subordinate s type plutons and a type syenite gabbros biotite k feldspar granites from tioman island off the east coast of malaysia also yield a zircon age of 80 1 ma showing cretaceous magmatism in common with province 1 geological and u pb geochronological data suggest that two east dipping in present day coordinates subduction zones are required during the triassic one along the bentong raub palaeo tethyan suture and the other west of the phuket burma province 1 belt supplementary material a full description of u pb analytical methods used and data tables are available at www geolsoc org uk sup18523

tectonic evolution of the mogok metamorphic belt burma myanmar constrained by u th pb dating of metamorphic and magmatic rocks 1 the mogok metamorphic belt mmb extends for over 1500 km along the western margin of the shan thai block from the andaman sea north to the eastern himalayan syntaxis previous geochronology has suggested that a long lasting jurassic early cretaceous subduction related event resulted in emplacement of granodiorites and orthogneisses 171 120 ma and a poorly constrained tertiary metamorphic event on the basis of new u pb isotope dilution thermal ionization mass spectrometry and u th pb laser ablation multicollector inductively coupled plasma mass spectrometer geochronology presented here we propose two tertiary metamorphic events affected the mmb in burma the first was a paleocene event that ended with intrusion of crosscutting postkinematic biotite granite dikes at 59 ma a second metamorphic event spanned late eocene to oligocene at least from 37 possibly 47 to 29 ma this resulted in the growth of metamorphic monazite at sillimanite grade growth of zircon rims at 47 43 ma sillimanite muscovite replacing older andalusite and synmetamorphic melting producing garnet and tourmaline bearing leucogranites at 45 5 0 6 ma and 24 5 0 7 ma these data imply high temperature sillimanite muscovite metamorphism peaking at 680 c and 4 9 kbar between 45 and 33 ma to around 606 656 c and 4 4 4 8 kbar at 29 3 0 5 ma the later metamorphic event is older than 24 5 0 3 ma the age of leucogranites that crosscut all earlier fabrics our structural and geochronological data suggest that the mmb links north to the unexposed middle or lower crust rocks of the lhasa terrane south tibet and east to high grade metamorphic core complexes in northwest thailand

evaluation of an experimental lidar for surveying a shallow braided sand bedded river reaches of a shallow 1 0 m braided sand bedded river were surveyed in 2002 and 2005 with the national aeronautics and space administration s experimental advanced airborne research lidar eaarl and concurrently with conventional survey grade real time kinematic global positioning system technology the laser pulses transmitted by the eaarl instrument and the return backscatter waveforms from exposed sand and submerged sand targets in the river were completely digitized and stored for postflight processing the vertical mapping accuracy of the eaarl was evaluated by comparing the ellipsoidal heights computed from ranging measurements made using an eaarl terrestrial algorithm to nearby 0 5 m apart ground truth ellipsoidal heights after correcting for apparent systematic bias in the surveys the root mean square error of these heights with the terrestrial algorithm in the 2002 survey was 0 11 m for the 26 measurements taken on exposed sand and 0 18 m for the 59 measurements taken on submerged sand in the 2005 survey the root mean square error was 0 18 m for 92 measurements taken on exposed sand and 0 24 m for 434 measurements on submerged sand in submerged areas the waveforms were complicated by reflections from the surface water column entrained turbidity and potentially the riverbed when applied to these waveforms especially in depths greater than 0 4 m the terrestrial algorithm calculated the range above the riverbed a bathymetric algorithm has been developed to approximate the position of the riverbed in these convolved waveforms and preliminary results are encouraging

the kinematic history of the khlong marui and ranong faults southern thailand abstract the khlong marui fault kmf and ranong fault rf are major nne trending strike slip faults which dissect peninsular thailand they have been assumed to be conjugate to the nw trending three pagodas fault tpf and mae ping fault mpf in northern thailand which experienced a diachronous reversal in shear sense during india eurasia collision it follows that the kmf and rf are expected to show the opposite shear sense and a slip sense reversal at a similar time to the tpf and mpf new field data from the kmf and rf reveal two phases of ductile dextral shear separated by campanian magmatism paleocene to eocene post kinematic granites date the end of this phase while a brittle sinistral phase deforms the granites and has exhumed the ductile fault rocks the timing of these movements precludes formation of the faults in response to himalayan extrusion tectonics instead they formed near the southern margin of a late cretaceous paleocene orogen and may have been influenced by variations in the rate of subduction ahead of india and australia north south compression prior to reactivation of the subduction zone around southern sundaland in the eocene caused widespread deformation in the over riding plate including sinistral transpression on the kmf and rf

the panghkawkwo graptolite bed llandovery silurian myanmar and the location of the sibumasu or sibuma terrane in the silurian abstract the panghkawkwo graptolite bed is shown to comprise several graptolitic horizons extending through the aeronian middle llandovery and into the lower telychian upper llandovery graptolite assemblages are diverse indicating an outer shelf or deeper depositional environment they are similar to those of bohemia and saudi arabia peri gondwanan europe and core gondwana respectively but include also taxa agetograptus and species of metaclimacograptus not known from these regions but which characterize lower latitude llandovery graptolite assemblages the evidence for the silurian location of the sibuma su terrane is discussed the presence of monograptus belophorus and cyrtograptus rigidus in the lower sheinwoodian wenlock of western yunnan suggests a non equatorial palaeolatitude the panghkawkwo graptolites suggest a location for sibuma su between gondwana and south china

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

the tectonic and metallogenic framework of myanmar a tethyan mineral system myanmar is perhaps one of the world s most prospective but least explored minerals jurisdictions containing important known deposits of tin tungsten copper gold zinc lead nickel silver jade and gemstones a scarcity of recent geological mapping available in published form coupled with an unfavourable political climate has resulted in the fact that although characterized by several world class deposits the nation s mineral resource sector is underdeveloped as well as representing a potential new search space for a range of commodities many of myanmar s known existing mineral deposits remain highly prospective myanmar lies at a crucial geologic juncture immediately south of the eastern himalayan syntaxis however it remains geologically enigmatic its mesozoic recent geological history is dominated by several orogenic events representing the closing of the tethys ocean we present new zircon u pb age data related to several styles of mineralization within myanmar we outline a tectonic model for myanmar from the late cretaceous onwards and document nine major mineralization styles representing a range of commodities found within the country we propose a metallogenetic model that places the genesis of many of these metallotects within the framework of the subduction and suturing of neo tethys and the subsequent himalayan orogeny temporal overlap of favourable conditions for the formation of particular deposit types during orogenic progression permits the genesis of differing metallotects during the same orogenic event we suggest the evolution of these favourable conditions and resulting genesis of much of myanmar s mineral deposits represents a single evolving mineral system the subduction and suturing of neo tethys

an early permian cool water fauna from pebbly mudstones in south thailand a small brachiopod fauna of early permian age is recorded from pebbly mudstones and sandstones of the phuket kaeng krachan group at the thai islands of ko muk and ko phi phi in the andaman sea most species belong to genera found in temperate to high permian palaeolatitudes whereas other permian faunas from thailand are strong in tropical affinities suggesting that the pebbly mudstones are cool water deposits contemporaneous with the late asselian glacial deposits of gondwana new taxa are arctitreta percostata sp nov komukia solita gen nov sp nov rugosochonetidae cancrinelloides monticulus sp nov rhynchopora culta sp nov arionthia sapa sp nov and elasmata retusus gen nov sp nov heterelasminidae

first evidence of the cambrian basement in upper peninsula of thailand and its implication for crustal and tectonic evolution of the sibumasu terrane abstract although the sibumasu terrane in asia was previously considered to be composed of phanerozoic rocks with cambrian crystalline basement no reliable or direct radiometric dating evidences of such crystalline basement was ever reported our new in situ zircon u pb dating of the khao tao orthogneiss yields a concordant age of 501 5 7 5 ma 2 which provides the first robust evidence for the cambrian crust in upper peninsula of thailand the zircon ehf t values range from 3 7 to 6 1 with model ages tcdm of 1244 1827 ma suggests a mixed crust mantle source the chemical similarity and spatial continuity of the khao tao orthogneiss with other pre neotethys marginal eurasian and sibumasu granitoids indicate the linear paleogeographic association under a similar magmatic arc related regime along the gondwana india australia margin as part of the pan african orogeny system

magmatic history of central myanmar and implications for the evolution of the burma terrane the burma terrane is a microplate at the eastern edge of the himalayan tibetan orogen the origin of which remains poorly understood its basement comprises metamorphic and igneous rocks forming the wuntho popa arc wpa and has been correlated with tibetan gondwana or transtethyan rocks yet little is known about the magmatic history of the wpa we report elemental and sr nd isotopic compositions of magmatic rocks crystallization zircon and apatite u pb and exhumation apatite fission track ages from rocks and river sands and structural measurements from the wuntho ranges central myanmar where the wpa is best exposed we show that the wpa in the wuntho ranges is characterized by two magmatic events at 108 90 ma and 46 32 ma magmatism is subduction related for both events characterized by depleted nd and sr isotopic compositions with more enriched values with time apatite fission track data suggest arc exhumation during the 39 22 ma time interval partly overlapping with the last magmatic event structural data indicate nw se striking tilting folding and thrusting that we associate with at least two phases of deformation in the cretaceous and the late paleogene correlating the wpa with tibetan gondwana or transtethyan rocks based on its magmatic history remains ambiguous however models arguing for a transtethyan origin for the wpa are most compatible with our results combined with available burmese geological data

accuracy assessment of lidar derived dems of bedrock river channels holtwood gorge susquehanna river 1 we evaluate the accuracy of 1 m lidar derived dems of an exposed bedrock channel and use these high resolution terrain models to calculate erosional fluxes between four levels of strath terraces dated previously with 10be recent investigations into the timing rates and processes by which rivers incise their bedrock channels have greatly enhanced our understanding of landscape evolution however measuring channel geometries in 3 dimensions is difficult thus volumes of bedrock eroded during incision events are rarely considered although our analysis successfully demonstrates the proportionality between incision rates and erosional fluxes for terraces high above the channel floor in this gorge unusually high river flows on the date of acquisition inundated lower bedrock surfaces preventing accurate volume estimates to ensure optimal low flow lidar coverage for fluvial environments we discuss methods to improve the scheduling of data acquisition by using archived discharge records and predictive models based on real time data

two parallel magmatic belts with contrasting isotopic characteristics from southern tibet to myanmar zircon u pb and hf isotopic constraints before the india asia collision neotethyan subduction gave rise to an andean type convergent margin on the southern margin of asia to investigate the spatial and temporal distribution of the subduction related magmatism we undertook a combined determination of zircon u pb ages and hf isotopes of mesozoic to paleogene intrusive and volcanic rocks from southern tibet to myanmar to characterize the two parallel magmatic belts that have previously been considered separately one belt extends from the gangdese batholith in the southern lhasa sub terrane to the lohit batholith the sodon pluton and the popa loimye arc in the west burma block and the other from the central lhasa plutonic belt to the bomi chayu batholith the dianxi batholith and the shan scarps batholith in central myanmar the gangdese belt as the main arc component consists typically of i type granitoids that contain magmatic zircons showing positive ehf t values in contrast the central lhasa plutonic belt belt is dominated by s type granites in which most zircons show negative ehf t values suggesting the involvement of older continental crust in their petrogenesis the distinct geochemical characteristics indicate not only distinct tectonic settings of their genesis but also the diverse nature of the crust forming the exotic continental ribbons amalgamated to asia supplementary material details of sample locations and analytical results are available at https doi org 10 6084 m9 figshare c 4311485

closing a sediment budget for a reconfigured reach of the provo river utah united states 1 we quantified all components of a fluvial sediment budget for a discrete flood on an aggrading gravel bed river bed load transport rates were measured at the upstream and downstream ends of a 4 km study area on the provo river utah during a dam controlled flood we also collected high resolution measurements of channel topography before and after the controlled flood for the entire reach topographic uncertainty in the digital elevation models dem was characterized using a spatially variable approach the net sediment flux provided unambiguous indication of storage sediment input to the reach 319 m3 exceeded output 32 m3 producing a net accumulation of approximately 290 m3 the difference between the scour and fill was also positive 470 m3 but uncertainty in the topographic differencing was larger than the observed net storage thus the budget would have been indeterminate if based on morphologic data alone although topographic differencing was not sufficiently accurate to indicate net storage it was able to demonstrate that internal erosion was a larger sediment source than the net sediment flux the magnitude of total erosion 1454 m3 and deposition 1926 m3 was considerably larger than net change in storage showing that internal sources and sinks were the dominant driver of channel change the findings provide guidance for the development of sediment budgets in settings in which one must choose between a morphological approach and the direct measurement of sediment flux

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

the origin and pre cenozoic evolution of the tibetan plateau different hypotheses have been proposed for the origin and pre cenozoic evolution of the tibetan plateau as a result of several collision events between a series of gondwana derived terranes e g qiangtang lhasa and india and asian continent since the early paleozoic this paper reviews and reevaluates these hypotheses in light of new data from tibet including 1 the distribution of major tectonic boundaries and suture zones 2 basement rocks and their sedimentary covers 3 magmatic suites and 4 detrital zircon constraints from paleozoic metasedimentary rocks the western qiangtang amdo and tethyan himalaya terranes have the indian gondwana origin whereas the lhasa terrane shows an australian gondwana affinity the cambrian magmatic record in the lhasa terrane resulted from the subduction of the proto tethyan ocean lithosphere beneath the australian gondwana the newly identified late devonian granitoids in the southern margin of the lhasa terrane may represent an extensional magmatic event associated with its rifting which ultimately resulted in the opening of the songdo tethyan ocean the lhasa northern australia collision at similar to 263 ma was likely responsible for the initiation of a southward dipping subduction of the bangong nujiang tethyan oceanic lithosphere the yarlung zangbo tethyan ocean opened as a back arc basin in the late triassic leading to the separation of the lhasa terrane from northern australia the subsequent northward subduction of the yarlung zangbo tethyan ocean lithosphere beneath the lhasa terrane may have been triggered by the qiangtang lhasa collision in the earliest cretaceous the mafic dike swarms ca 284 ma in the western qiangtang originated from the panjal plume activity that resulted in continental rifting and its separation from the northern indian continent the subsequent collision of the western qiangtang with the eastern qiangtang in the middle triassic was followed by slab breakoff that led to the exhumation of the qiangtang metamorphic rocks this collision may have caused the northward subduction initiation of the bangong nujiang ocean lithosphere beneath the western qiangtang collision related coeval igneous rocks occurring on both sides of the suture zone and the within plate basalt affinity of associated mafic lithologies suggest slab breakoff induced magmatism in a continent continent collision zone this zone may be the site of net continental crust growth as exemplified by the tibetan plateau c 2012 international association for gondwana research published by elsevier b v all rights reserved

gondwana and cathaysian blocks palaeotethys sutures and cenozoic tectonics in south east asia the triassic indosinian orogeny followed extinction of the palaeotethys ocean resulting in suturing of gondwana affinity and cathaysian blocks

zircon u pb ages in myanmar magmatic metamorphic events and the closure of a neo tethys ocean abstract previous isotopic age studies have concluded that the main metamorphism in the mogok metamorphic belt mmb in myanmar was tertiary and caused by collision with or underthrusting by india we present here results of zircon u pb age determinations on 18 samples from myanmar largely on intrusive rocks from the north trending 550 km long shan scarps segment of the sickle shaped mmb the oldest determination is 491 ma on orthogneiss north of mandalay interpreted as a protolith age and similar to the stratigraphic age of the bawdwin volcanics augen gneiss at kyaukse has a 114 ma protolith age our zircon u pb ages on undeformed intrusive rocks in the mmb range from cretaceous to miocene the oldest 128 ma on a diorite near yebokson implies an earliest cretaceous minimum age for regional metamorphism here younger ages on undeformed intrusions include 91 ma on diorite at mokpalin 72 ma on the weakly foliated garnet bearing nattaung granite 44 and 48 ma respectively on the mec and sedo granites and 17 20 ma on granite dykes for the 128 ma diorite sr and nd isotopes indicative of a continental crust component and mapped continuity of metamorphic host rocks suggest correlation with mid early cretaceous plutons in the eastern transhimalayas zircon u pb ages for the mec sedo and other granites within the mmb and slate belt help to define a late cretaceous to early eocene age range for mostly ilmenite series peraluminous granites within the western granite belt and more restricted western tin belt of myanmar and southern thailand in the wuntho popa arc west of the dextral sagaing fault our new u pb zircon age of 105 ma on diorite at salingyi supports previous k ar ages 106 93 ma for pre tertiary intrusions in the cretaceous this arc may have occupied the andaman sea and continued northwards through the mokpalin diorites and west of the mmb to the 103 80 ma i type plutons in the gandise batholith of southern tibet we interpret the mmb and slate belt as part of a western myanmar block separated in the jurassic from the shan plateau to the east by the southwestward continuation of the bangong nujiang luxi neo tethys i ocean we relate most intrusive and metamorphic events in and near the mmb to westward subduction of this ocean and end jurassic collision of the plateau with the overriding western myanmar slate belt block to orogenic polarity reversal and early cretaceous westward translation of the plateau sequence over the suture zone and to eastward subduction of the ancestral indian ocean or neo tethys ii beneath myanmar with generation of the wuntho popa arc beginning before the late cretaceous the mmb includes meta plateau rocks near mandalay but meta slate belt rocks to the north and south within the mmb previous monazite xenotime thorite ages of eocene oligocene and oligocene early miocene cooling ages on micas with no deformation in eocene granites suggest a high temperature thermal event related to intrusion of these and other granites during a previously proposed regional extension our data imply that the main fabric forming metamorphic event in the mmb pre dated the india asia collision

permian of myanmar abstract permo triassic carbonates with minor basal clastics cover extensive tracts of the shan plateau in the eastern part of myanmar these carbonates are grouped into the permian thitsipin limestone formation and the late permian early triassic nwabangyi dolomite formation the thitsipin formation occurs as isolated masses in many places faulted against older rocks it is now known that there is a regional unconformity between the thitsipin limestone formation and the underlying silici carbonates of devonian age in shan state and between the thitsipin limestone formation and carboniferous meta siliciclastics in kayah state mon state kayin state and tanintharyi division some of the thitsipin limestone is dolomitized and passes transitionally upward into the nwabangyi dolomite formation permian shelf carbonates occur within two different sequences the silici carbonate sequence of the shan thai block and the meta siliciclastic sequence of the mergui terrane suggesting that the permian limestones were deposited after the emplacement of the mergui terrane onto the southern margin of the shan thai block this event occurred when the shan thai block was in the southern hemisphere