unconformity of red sandstones in north vietnam field evidence for indosinian orogeny in northern indochina we re examine several unconformity sites in northwestern vietnam where the indosinian orogenesis has been defined field observations in the black river song da region near son la demonstrate that red sandtones and conglomerates reportedly of cretaceous age occur unconformably above schistosed epimetamorphic middle triassic sediments a mesozoic unconformity thus really exists in this region though the age of deformation is poorly contrained upper triassic to upper cretaceous in most places however the unconformity is strongly deformed folded triassic limestones are often thrusted onto the cretaceous rocks this implies that tertiary deformations probably due to the india asia collision have been strong in the northern part of the indochina block

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

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

intraplate extension prior to continental extrusion along the ailao shan red river shear zone left lateral movement of the ailao shan red river shear zone lends support to the hypothesis of continental extrusion resulting from the collision of india with asia our new observations from northwestern yunnan china and northwestern vietnam on different sides of the shear zone demonstrate that the sinistral offset was 600 km according to correlations of permian triassic flood basalt successions and late paleogene highly potassic mafic magmas we conclude that the shear was propagating on the south china continental margin and does not correspond to a suture between south china and indochina furthermore the highly potassic magmas were emplaced from ca 40 to 30 ma before the shear movement which was caused by the late oligocene to early miocene ca 27 22 ma extrusion activity this suggests that a late eocene to early oligocene intraplate extension possibly induced by delamination of thickened continental lithosphere took place in northwestern yunnan or eastern tibet as a response to the india asia collision this extension and sea floor spreading of the south china sea that began ca 30 ma could have accounted for the initiation of the ailao shan red river shear zone

structural and geochronological constraints on the tectonic evolution of the dulong song chay tectonic dome in yunnan province sw china abstract the dulong song chay tectonic dome lies on the border of china se yunnan province and northern vietnam and consists of two tectonic and lithologic units a core complex and a cover sequence separated by an extensional detachment fault these two units are overlain unconformably by late triassic strata the core complex is composed of gneiss schist and amphibolite shrimp zircon u pb dating results for the orthogneiss yield an age of 799 10 ma which is considered to be the crystallization age of its igneous protolith formed in an arc related environment a granitic intrusion within the core complex occurred with an age of 436 402 ma which probably formed during partial closure of paleotethys within the core complex metamorphic grades change sharply from upper greenschist low amphibolite facies in the core to low greenschist facies in the cover sequence there are two arrays of foliation within the core complex detachment fault and the cover sequence s 1 and s 2 the pervasive s 1 is the axial plane of intrafolial s 0 folds d 1 deformation related to this foliation is characterized by extensional structures the strata were structurally thinned or selectively removed along the detachment faults indicating exhumation of the dulong song chay tectonic dome the major extension occurred at 237 ma determined by shrimp zircon u pb and 39 ar 40 ar isotopic dating techniques regionally simultaneous tectonic extension was associated with pre indosinian collision between the south china and indochina blocks the s 2 foliation appears as the axial plane of nw striking s 1 buckling folds formed during a compressional regime of d 2 d 2 is associated with collision between the south china and indochina blocks along the jinshajiang ailao shan suture zone and represents the indosinian deformation the dulong granites intruded the dulong song chay dome at 144 2 140 2 and 116 10 ma based on 39 ar 40 ar measurement on muscovite and biotite the dome was later overprinted by a conjugate strike slip fault and related thrust fault which formed a vortex structure contemporaneously with late cenozoic sinistral movement on the ailao shan red river fault

the indosinian orogeny a perspective from sedimentary archives of north vietnam the triassic stratigraphic framework for the song da and the sam nua basins north vietnam suffers important discrepancies regarding both the depositional environments and ages of the main formations they contain using sedimentological analyses and dating foraminifer biostratigraphy and u pb dating on detrital zircon we provide an improved stratigraphic framework for both basins a striking feature in the song da basin located on the southern margin of the south china block is the diachronous deposition over a basal unconformity of terrestrial and marine deposits the sedimentary succession of the song da basin points to a foreland setting during the late early to the middle triassic which contrasts with the commonly interpreted rift setting on the northern margin of the indochina block the sam nua basin recorded the activity of a proximal magmatic arc during the late permian up to the anisian this arc resulted from the subduction of a southward dipping oceanic slab that separated the south china block from the indochina block during the middle to the late triassic the song da and sam nua basins underwent erosion that led to the formation of a major unconformity resulting from the erosion of the middle triassic indosinian mountain belt built after an ongoing continental collision between the south china and the indochina blocks later during the late triassic as syn to post orogenic foreland basins in a terrestrial setting the song da and sam nua basins experienced the deposition of very coarse detrital material representing products of the mountain belt erosion

decorrelation in interferometric radar echoes a radar interferometric technique for topographic mapping of surfaces implemented utilizing a single synthetic aperture radar sar system in a nearly repeating orbit is discussed the authors characterize the various sources contributing to the echo correlation statistics and isolate the term which most closely describes surficial change they then examine the application of this approach to topographic mapping of vegetated surfaces which may be expected to possess varying backscatter over time it is found that there is decorrelation increasing with time but that digital terrain model generation remains feasible the authors present such a map of a forested area in oregon which also includes some nearly unvegetated lava flows such a technique could provide a global digital terrain map

indosinian dextral ductile fault system and synkinematic plutonism in the southwest of the ogcheon belt south korea reply abstract the structure of the mylonite belt in the southwestern part of the ogcheon belt has been investigated and interpreted in the light of recent radiometric data the shear belt is composed of several en echelon dextral shear zones relayed by compressional or extensional tectonic bridges the dextral displacement along the fault system which may be extended to the hida zone of japan is of the order of 200 km it has brought into contact the ryeongnam block and its cambrian middle ordovician cover of north china affinity with the southwestern margin of the ogcheon belt characterized by cambrian middle silurian rift facies and shelf deposits of south china affinity synkinematic plutons are emplaced within the shear belt which is postdated by uppermost triassic unfoliated granitoids at the surface the shear belt generated elongated intermontane coal basins initiated as transtensional half grabens because of its post permian pre early jurassic age and its dextral kinematics we correlate the shear belt with the late stages of the akyioshi indosinian collisional orogeny of the east asian margin the synkinematic plutonism that accompanied the shear zone may be due to post collisional crustal stretching and subsequent anatexis at the mantle crust interface

an evaluation of criteria to deduce the sense of movement in sheared rocks some of the most useful criteria for the deduction of the sense of shear are summarized for use in areas where unequivocal field evidence is lacking apparently conflicting evidence from rotated pressure shadow regions around porphyroclasts and porphyroblasts is clarified the use of quartz crystallographic fabric asymmetry to deduce the shear sense in the bulk rock should be treated with caution and used only together with detailed microstructural observations

the red river fault system in the tonkin gulf vietnam abstract the red river fault system in the tonkin gulf offshore haiphong was studied using seismic profiles calibrated by deep wells well characterised left lateral strike slip occurred continuously within a narrow 30 km wide zone southwest of the vinh minh fault between 30 ma and 5 5 ma however the corresponding amount of offset probably does not exceed a few tens of kilometres no sign of post 5 5 ma right lateral motion can be detected prior to 30 ma there is a widespread extension in a wider 100 km wide zone which could be related to a significant amount of left lateral motion the motion of the fault splays to the northeast of the vinh minh fault prior to 30 ma was absorbed in the rifting of the gulf of beibu a 15 5 ma unconformity separates the transtensional regime from a later transpresional regime this 15 5 ma date coincides with the cessation of sea floor spreading in the south china sea

north directed triassic nappes in northeastern vietnam east bac bo abstract a careful re examination of the previous tectonic descriptions and the acquisition of new structural and kinematic data have been undertaken in northeastern vietnam the structure of the area consists of a system of slightly metamorphosed but ductilely deformed nappes including recumbent folds formed during the triassic prior to the unconformable deposition of the upper triassic terrigenous sediments these results confirm the previous interpretation of preyunnanaises nappes represented by middle upper paleozoic foliated limestone resting through a flat mylonitic contact over an intermediate song mien unit deprat 1915 the latter made essentially of deformed lower triassic sedimentary and volcanic formations which previously filled the song hien rift bourret 1922a bourret 1922b in the external part of the belt the triassic strata conformably overlie slightly deformed and unmetamorphosed upper paleozoic rocks forming an autochthonous domain alternatively the same triassic succession can be seen resting tectonically through decollement zones directly over the middle paleozoic marbles to form a distinct but subsidiary allochthonous unit our data show that the song chay orthogneiss and its lower paleozoic sedimentary country rocks belong to the main nappe they also demonstrate that this nappe was transported to the n ne a newly discovered ophiolitic melange of supposed oceanic nature and triassic age lying along the song chay fault north of the nui con voi could hypothetically represent the rooted zone of the nappe a tertiary overprinting event in particular accommodated by strike slip movements likely accounts for the present orocline of ne vietnam

tertiary deformation and metamorphism se of tibet the folded tiger leap decollement of nw yunnan china the yulong haba xue shan range in the northwestern part of yunnan china is a large n s antiform that folds the paleozoic series of the yangzi platform the upper yangzi river jinsha jiang has cut a 3500 m deep valley hu tiao gorge across this antiform thus exposing folded bedding parallel ductile shear zones decollements with transport toward the ssw in the present geographical coordinates the large finite shear strain implies tens of kilometers of transport pointing to the regional significance of these decollements rb sr radiometric dating of phlogopites that crystallized in marbles within the foliation planes yields the age of the metamorphic and deformation event 35 9 0 3 2 ma the age derives from an internal rb sr isochron made on different size fractions of the same mineral which provides a novel demonstration of the feasibility of such plots transport on the decollement and related shortening occurred prior to or at the onset of extrusion of indochina along the ailao shan red river shear zone 80 km west of the yulong shan the 39ar 40ar age spectra of k feldspar from the core of the yulong shan suggest uplift by antiformal folding around 17 ma as indochina s extrusion came to an end we infer that other large scale cenozoic decollements such as that exhumed in the yulong shan underlie some of the vast folded areas that surround the eastern himalayan syntaxis transport on such decollements first toward the south and then toward the east and folding above them might have occurred during two principal shortening phases whose ages bracket indochina s escape toward the se

understanding mesozoic accretion in southeast asia significance of triassic thermotectonism indosinian orogeny in vietnam results from a zircon u pb study of the metamorphic basement of vietnam reveal that a large part of the continental crust was affected by a short lived episode of ductile deformation and high temperature metamorphism between 258 6 ma and 243 5 ma although coincident with final stages of north south china collision qinling orogenesis the thermotectonism in vietnam was caused by accretion of sibumasu to indochina south china this accretion event indosinian orogeny has regional significance because it contributed to the final stages of north south china collision an aspect not explicitly recognized in qinling orogenic models

structural petrological and thermal evolution of a tertiary ductile strike slip shear zone diancang shan yunnan the diancang shan a horst massif within the red river fault zone in yunnan people s republic of china preserves a structural petrological and thermal record of two distinct phases of tectonic activity a left lateral ductile shear that terminated between 20 and 17 ma and a ductile to brittle phase of normal faulting which began at 4 7 ma and remains active mylonitic rocks in the core of the range display an early steep high temperature ht schistosity and a horizontal stretching lineation that are both parallel to the trend of the belt kinematic indicators indicate that shear was left lateral the complex shape of the ht schistosity at the southern termination of the massif likely results from a large scale oblique left lateral c shear plane that dismembered the shear zone and separated the ailao shan and the diancang shan as left lateral deformation terminated thermochronological and thermobarometric results suggest that the gneisses were partially unroofed during this event along the eastern edge of the diancang shan the ht fabrics were overprinted by low temperature structures during activation of east dipping normal faults cooling associated with this normal right lateral faulting along the diancang shan and perhaps activation of the right lateral normal movement on the range front fault farther south along the ailao shan began at 4 7 0 1 ma these results tend to support the view that extrusion of indochina occurred along the left lateral red river shear zone between 35 and 19 17 ma initiation of right lateral normal slip during the late miocene may relate to eastward extensional collapse of the thickened tibetan crust or more probably to initiation of the second phase of extrusion

structure and evolution of the himalaya tibet orogenic belt the 1981 french chinese expedition to tibet focused on the lhasa block extending earlier coverage 400 km north of the tsangpo suture the lhasa block stood between 10 and 15 n latitude over most of the upper cretaceous and eocene and if gondwanian in origin had detached from gondwana by early permian seismic profiles reveal a complex moho topography resulting both from multiple continental thrusting and large scale strike slip faulting subduction related granitoids representing mixtures of mantle and crustal components and anatectic granitoids have been analysed and dated this study emphasizes the role of smaller blocks in the accretion of the continental mosaic

porphyroclast systems as kinematic indicators porphyroclasts of relatively strong minerals in mylonites commonly have an internal monoclinic shape symmetry defined by tails of dynamically recrystallized material the geometry of a porphyroclast and its tails called a porhyroclast system can serve as a valuable indicator of the sense of vorticity porphyroclast systems have been divided into and types on the basis of the geometry of the tails types have wedge shaped recrystallized tails whose median lines lie on opposite sides of a reference plane parallel to the tails and containing the symmetry axis for the system types are further subdivided into a a types in which the porphyroclast is isolated in a relatively homogeneous matrix and b types in which the porphyroclast system is associated with a shear band foliation in the matrix types typically have narrow recrystallized tails whose median lines cross the reference plane adjacent to the porphyroclast consequently embayments of matrix material occur adjacent to the porphyroclasts and the tails display characteristic bends a porphyroclast system in a mylonite develops when the relatively weak dynamically recrystallized grain aggregate in the porphyroclast mantle changes its shape due to non coaxial flow in the adjacent matrix this behaviour has been modelled in shear box experiments passive marker lines around rigid cylinders embedded in silicone putty were subjected to simple shear the experiments were modified to simulate a change in recrystallization rate r with respect to rate of deformation by decreasing the diameter of the rigid cylinder during deformation at variable rates the ratio r appears to be one of the most important factors in determining which porphyroclast system will develop at high r values flow of recrystallized material away from the porphyroclast is continuously appended by the production of new grains and wedge shaped a type tails develop at low r values relatively few new grains are added to the tails which become thinned and deflected by drag due to the spinning motion of the porphyroclast in addition most porphyroclast systems at low shear strains are of a type or lack monoclinic symmetry whereas types are only developed at high shear strain values complex porphyroclast systems characterized by two generations of tails are observed in many of the natural and model shear zones studied and may form due to fluctuating r conditions that allow isolated a and type porphyroclast systems to be used as sense of vorticity indicators are the systems should have a monoclinic shape symmetry matrix grain size should be small with respect to porphyroclast size matrix fabric should be homogeneous deformation history should be simple and observations should be made on sections normal to the inferred bulk vorticity vector for the mylonite

high resolution insar constraints on flood related subsidence and evaporite dissolution along the dead sea shores interplay between hydrology and rheology abstract sinkhole generation and land subsidence are commonly attributed to dissolution of subsurface layers by under saturated groundwater and formation of cavities along the dead sea ds shorelines this process also involves seasonal flash floods that are drained into the subsurface by existing and newly formed sinkholes we quantify the contribution of flash floods to salt dissolution and land subsidence using high resolution interferometric synthetic aperture radar insar subsidence rates during a 3 year period 2012 2015 were calculated from 57 cosmo skymed x band interferograms bracketing major flood events and intra flood periods in 21 sinkhole sites the sites are located within channels and alluvial fans along the western shores of the dead sea israel the observed subsidence reaches maximum rates of 2 5 mm day accumulating in specific sites to 500 mm year in most of the sinkhole sites a gradual increase in the annual subsidence rate is observed during the 3 year study period three different modes of response to floods were observed 1 sites where floodwater is not directly channeled into sinkholes do not respond to floods 2 sites adjacent to active channels with sinkholes are unaffected by specific floods but their subsidence rates increase gradually from early winter to mid summer and decay gradually until the following winter and 3 sites in active channels with sinkholes are characterized by an abrupt increase in subsidence rates immediately after each flood by a factor of up to 20 and by a subsequent quasi exponential subsidence decay over periods of several months in these latter sites subsidence rates after each flood are temporally correlated with alternating groundwater levels in adjacent boreholes the rapid rise in groundwater head following floods increases the hydraulic gradient of the under saturated groundwater and hence also the groundwater discharge and the dissolution rate of the subsurface salt layer a subsequent quasi exponential water level drop results in similar deceleration in dissolution and subsidence rates with a similar characteristic decay time of about 150 days the observed subsidence decay pattern may also be explained by viscoelastic relaxation of the overburden in response to instantaneously formed dissolution cavities utilizing a kelvin viscoelastic model we show that the contribution of this process is most probably

late quaternary tectonics and seismotectonics along the red river fault zone north vietnam abstract a study of active tectonic development in vietnam is of great importance right lateral strike slip offsets along the red river fault during the pliocene present are determined by analyzing tributaries quaternary alluvial fans river valley from landsat spot images detailed topographical maps and field observation along the sw fault of the red river right lateral offsets of stream channels range between 150 and 700 m mean offsets of 300 m drainage offsets 170 450 m are found on the eastern branch assuming the major phase of incision is visible in this area which is close to the red river delta due to the onset of riss glaciation using the average length of offset channels and a minimum rate of 100 150 mm yr for river propagation we estimate the horizontal slip rates of 2 9 1 7 mm yr for song chay fault 2 3 1 5 mm yr for red river left side fault and 2 1 1 5 mm yr for red river left side fault several active faults associated with it are observed in son la area the phong tho nam pia fault is clearly seen in the geomorphology which separates tu le and song da rift zones in normal fault segments striking nw se sw dipping is observed clearly from spot images in the field triangular facets indicate typical dip slip displacement based on different data vertical slip rate of phong tho nam pia fault is estimated to be 0 2 0 4 mm y for pliocene present 0 5 3 mm y for quaternary present and 0 6 1 7 for the present time based on various methods maximum credible earthquakes for different fault segments in vietnam were estimated

new constraints on the structure thermochronology and timing of the ailao shan red river shear zone se asia new structural petrographic and 40ar 39ar data constrain the kinematics of the asrr ailao shan red river shear zone in the xuelong shan xls geochronological data reveal triassic early tertiary and oligo miocene thermal events the latter event 33 26 ma corresponds to cooling during left lateral shear in the fansipan fsp range thrusting of the sapa nappe linked to left lateral deformation and cooling of the fsp granite occurred at 35 ma rapid cooling resumed at 25 29 ma as a result of uplift within the transtensive asrr in the daynuiconvoi dncv foliation trends nw se but is deflected near large scale shear planes stretching lineation is nearly horizontal on steep foliations shear criteria indicate left lateral shear sense zones with flatter foliations show compatible shear senses petrographic data indicate decompression from 6 5 kbar during left lateral shear temperatures 700 c 40ar 39ar data imply rapid cooling from above 350 c to below 150 c between 25 and 22 ma without diachronism along strike along the whole asrr cooling histories show two main episodes 1 rapid cooling from peak metamorphism during left lateral shear 2 rapid cooling from greenschist conditions during right lateral reactivation of the asrr in the nw part of the asrr xls diancang shan we link rapid cooling 1 to local denudations in a transpressive environment in the sw part ailao shan and dncv cooling 1 resulted from regional denudation by zipper like tectonics in a transtensive regime the induced cooling diachronism observed in the ailao shan suggests left lateral rates of 4 to 5 cm yr from 27 ma until 17 ma dncv rocks always stayed in a transtensive regime and do not show cooling diachronism the similarities of deformation kinematics along the asrr and in the south china sea confirms the causal link between continental strike slip faulting and marginal basin opening

mapping ground movements caused by mining induced earthquakes applying satellite radar interferometry abstract anthropogenic activity related to the extraction of gas and oil raw materials or water pumping leads to slow or rapid ground deformation the ground motion rate is related to the type of the mined material geological conditions mining methods and other factors ground subsidence resulting from the collapse of underground post mining voids occurs gradually mining induced earthquakes and seismic earthquakes are largely unpredictable and have an adverse impact on the local inhabitants and buildings for this reason monitoring of this phenomenon is a challenge the application of interferometric sar for the evaluation of ground movement has brought satisfactory results over the past twenty years mainly in the regions where no other measurements were conducted during ground subsidence in this paper we have examined a mining induced earthquake with a magnitude 4 5 which occurred in an underground copper ore mine in poland on 29th november 2016 and caused eight fatalities it also had an impact on ground surface deformation in the vicinity of the mine tailings an assessment of the earthquake related impact on surface movement was carried out by sentinel 1 tops time series interferometry the velocity of ground movement and the scale of the phenomenon were investigated in addition the impact of the mining induced earthquake on zelazny most mine tailings site was analyzed moreover the process of dynamic ground compaction was also investigated in detail ground movement following the mine earthquake was explored two time phases of the movements were determined the first phase of dynamic ground displacement was rapid and 90 of total ground deformation appeared on the surface within 7 days the second phase of displacement was a vanishing one it lasted for approx 3 weeks and 10 of ground deformation appeared on the surface the study revealed that the maximum observed ground subsidence did not exceed 9 cm the presented results contribute to a better understanding of post earthquake ground deformations in the light of their spatial distribution in time

geochronology and geochemistry of the late triassic longtan pluton in south china termination of the crustal melting and indosinian orogenesis the indosinian orogeny is recorded by triassic angular unconformities in vietnam and south china and by widely occurring granitoids in the yunkai nanling and the xuefengshan belts of south china the longtan pluton in the northwestern part of the xuefengshan belt is a typical high k calc alkaline i type granitoid which can shed light on the relationship between the indosinian tectonic and magmatic activity in the region three precise zircon u pb ages yielded a mean of 218 0 8 ma which is taken as the age of crystallization the pluton consists of both granodiorite 64 59 68 01 sio2 and 3 25 4 22 k2o and granite 70 49 71 80 sio2 and 4 07 4 70 k2o the granodiorites are characterized by relatively high mg 54 57 low contents of na2o 3 2 4 3 wt low abundances of incompatible elements lile nb and p high initial 87sr 86sr 0 7175 0 7184 and negative end t 9 98 to 9 72 ree patterns show moderate fractionation la yb cn 8 07 18 80 with negative eu anomalies eu eu 0 62 0 86 compared with the granodiorite the granite has a wider range of mg 49 59 lower contents of na2o 2 8 4 2 wt higher initial 87sr 86sr 0 7232 0 7243 and more negative end t 12 07 to 11 24 values ree patterns are relatively flat la yb cn 14 73 29 37 with smaller negative eu anomalies eu eu 0 48 0 63 the granodiorite has lower k2o na2o and al2o3 mgo feotot values than the granite based on major and trace element geochemistry and sr nd isotopes we interpret the longtan granodioritic magma to have been derived by partial melting of interlayered proterozoic metabasaltic to metatonalitic source rocks whereas the granite was probably derived from a mixture of proterozoic metagraywackes and metaigneous rocks field petrographic and geochemical evidence indicate that partial melting and fractional crystallization were the dominant mechanism in the evolution of the pluton the longtan granodiorites and granites are petrologically and geochemically similar to typical indosinian varieties and are considered to have been produced in a similar manner the indosinian granitoids in the region show a magmatic peak age of 238 ma from the yunkai nanling belt in the southeast and a magmatic peak age of 218 ma of the xuefengshan belt to the northwest these early and late magmatic episodes of the indosinian granitoids also display slight variations of regular compositions end t values and t dm ages thus we propose a syncollisional extension model that indosinian granitoids were generated by decompressional partial melting of crustal materials triggered by two extensions during collision of the indochina and south china blocks the longtan pluton in the northwesternmost part of the orogenic belt marks the termination of the indosinian magmatism and orogenesis

ar ar and fission track ages in the song chay massif early triassic and cenozoic tectonics in northern vietnam the song chay massif is the northeasternmost metamorphic complex in vietnam to the east of the red river shear zone it shows a large antiformal structure involving orthogneisses and migmatites overlain on its northern flank by muscovite bearing marbles an e w striking fault bounds the dome to the south kinematic indicators along a s n section reveal top to the n shear sense along the interface between the orthogneissic core and the overlying metasediments radiometric ages were obtained by the 40ar 39ar method using purified mica separates across the dome ages range from 236 ma at the southern edge to 160 ma in the core attesting to a strong imprint in the early triassic time a clear difference is seen between these mesozoic ages and the eocene to miocene ages from 40 to 24 ma that obtained in the nearby red river shear zone using the same method these data show that the song chay massif was already high in the crust when the high temperature deformation of the red river shear zone took place the final exhumation of the song chay orthogneiss constrained by fission track analysis on samples along the same transect occurred during the early miocene and could be interpreted as the consequence of a first normal sense of motion along the fault which bounds the massif to the south timing is similar to that of exhumation in the red river shear zone

sinkhole monitoring and early warning an experimental and successful gb insar application abstract sinkholes represent a natural risk that may hit catastrophically without clearly detectible precursors however they are often overlooked by people and administrators therefore sinkhole monitoring and associated early warnings constitute important research topics but currently only a few papers about sinkhole prediction can be found in this paper an experience of sinkhole monitoring and early warning with gb insar is described the latter is a highly precise instrument that is able to produce displacement maps with metric spatial resolution the described activities were carried out on elba island central italy where karstified limestone set off the occurrence of nine sinkholes since 2008 all within less than 3000 m2 causing major damage to an important road and many indirect losses in 1 year of monitoring two deforming areas were detected and the point where a sinkhole was about to propagate to the street level was predicted thus permitting the preventive closure of the road the deformation area was larger than the hole generated by the sinkhole thus showing a subsidence that continued for a prolonged time even after the cavity was filled up the occurrence of a 1 5 m wide sinkhole undetected by the gb insar also showed the lower detection limit of the instrument

palaeocene early eocene inversion of the phuquoc kampot som basin se asian deformation associated with the suturing of luconia abstract the little explored cambodian and vietnamese phuquoc kampot som basin is a late jurassic to early cretaceous foreland basin developed in response to the build up of a palaeo pacific magmatic arc a combination of seismic data well data and outcrop geology complemented by fission track and u pb analysis is used to unravel the basin history this reveals a hitherto unknown earliest palaeogene basin inversion associated with the luconian suturing to se asia and the shutdown of palaeo pacific subduction underneath se asia the phuquoc kampot som basin and the khorat basin in thailand constitute the erosional remnants of a larger basin that covered large parts of se asia in late mesozoic time and subsequently became segregated during earliest palaeogene inversion and erosion inversion was focused along the several hundred kilometres long kampot and khmer chanthaburi fold belts that confine the phuquoc kampot som basin and merge with the mae ping and the three pagodas fault zones these connections together with local nw se trending sinistral transpressional faults offshore indicate a link between initial se asian left lateral strike slip faulting and the luconian suturing the separation between the once unbroken khmer chanthaburi fold belt and the phetchabun fold belt in thailand suggests a 50 100 km cenozoic left lateral offset across the mae ping fault zone

the south china block indochina collision where when and how this study uses new field observations and existing studies to shed new light on the origin and significance of two nw se striking orogens in nw and ne vietnam we conclude that the architecture of each belt is a stack of ne directed nappes formed either under deep ductile synmetamorphic conditions or under shallow depth in the sw and ne parts respectively the song ma zone and song chay ophiolitic melange represent two ophiolitic sutures however the late permian song da and babu mafic rocks are not ophiolites but intraplate basalts related to the emeishan plume a late triassic unconformity the 225 205 ma postorogenic plutonism and the 250 230 ma syntectonic metamorphism support an early to middle triassic age for these tectonic events both nw and ne belts are due to sw directed subduction with arc magmatism ocean closure and continental collision though two contemporary s dipping subduction zones might explain the structural evolution of the two belts a single convergent system offset by the tertiary red river fault is preferred as this s directed subduction better accounts for the late permian intraplate magmatism this scenario is discussed in the general geodynamic framework of se asia

geodynamics of the indosinian orogeny between the south china and indochina blocks insights from latest permian triassic granitoids and numerical modeling

nanpanjiang basin a window on the tectonic development of south china during triassic assembly of the southeastern and eastern asia abstract as the largest siliciclastic sink in the south china block the triassic nanpanjiang basin is generally thought of as a foreland basin related to indosinian collision between the south china and indochina blocks our basin analysis spanning an eight years period provides details of lopingian to middle triassic stratigraphic fill and tectonic subsidence of the basin field observation and sedimentological analyses reveal that the basin was not filled by a monotonous turbidite system and suggest instead the development of five primary depositional units constituted by deep water turbidite systems mass transport deposits condensed drapes shallow water isolated carbonate platforms and volcano volcaniclastic rocks the stratigraphic completeness of the basin the coexistence of widespread but localized carbonate platforms within axially filled deep water basin tectonically generated cyclothems of transverse mass transport deposits along intrabasinal faults and basin fill of extrusive rocks of bimodal composition together apparently call in question the claim that crustal shortening prevailed during the late permian to pre norian triassic patterns of basin fill differential tectonic subsidence and very high subsidence rate of the region adjacent to master fault are more closely match the pattern expected for extensional to transtensional basin in a back arc setting the crustal extension in the southwestern south china was not consistent with hypothesized indosinian collision between south china and indochina blocks but more likely developed in response to northwestward subduction of the paleo pacific plate our results combined with regional considerations lead to a new model for the triassic tectonic evolution of south china during triassic assembly of the southeastern and eastern asia

late triassic post collisional slab break off along the ailaoshan suture insights from oib like amphibolites and associated felsic rocks what dynamic processes the south china indochina collision had gone through is still a pending problem our recent investigations identified a late triassic gabbroic intrusion in mengdong village and several granitic plutons near wana village yunnan province sw china both have underwent strong metamorphism and been altered to amphibolite and granitic gneiss respectively we carried out sims and la icpms zircon u pb dating for the amphibolites and granitic gneisses respectively dating results yield weighted mean 206pb 238u ages of 221 5 5 3 ma for the amphibolites and 224 0 1 8 and 235 4 0 6 ma for the granitic gneisses the amphibolite samples have low mg 41 7 42 8 high tio2 3 7 wt and na2o na2o k2o 1 89 2 68 contents and depleted sr nd isotopic compositions 87sr 86sr i 0 707647 and e nd t 1 17 they exhibit oib like ree patterns and spidergrams with strongly enriched lree contents insignificant eu anomalies eu 0 99 1 03 and moderate negative sr anomalies sr 0 46 0 56 the protolith gabbro of the mengdong amphibolites is derived from low degree partial melting of a homogeneous oib type mantle source in the garnet stability field and experienced significant fractionation of olivine clinopyroxene and plagioclase during magma evolution the wana samples are strongly peraluminous a cnk 1 1 and k enriched k2o na2o 2 93 3 63 they show enriched sr nd isotopic compositions with 87sr 86sr i 0 718589 0 719754 and e nd t 11 34 to 10 92 the wana plutons are typical s type granite and product of the dehydration melting of meta sedimentary rocks we summarized late triassic age data in the literature along the south china indochina suture zone and recognized a significant late triassic magmatic flare up in combination with previous studies on the late triassic hp uhp metamorphic rocks we proposed that during the late triassic the south china indochina suture zone had transformed into post collisional setting and accompanied slab break off triggered the oib type asthenospheric mantle upwelling and provided the heat source for the late triassic magmatic flare up

sinkhole occurrence monitoring over shallow abandoned coal mines with satellite based persistent scatterer interferometry abstract unexpectedly occurring sinkholes caused by shallow submerged voids are one of the key problems of intensively built up post mining areas five percent of poland s territory is still under the influence of post mining deformation impending sinkholes which tend to develop randomly over very large areas cannot be detected by using traditional geophysical methods moreover geodetic measurement methods like global positioning system gps analyses tachymetry laser scanning or photogrammetry may be useful only for the registration of the dimensions and locations of sinkholes that have already occurred here we investigate an area in upper silesia poland where 345 sinkholes were recorded over a period of more than 20 years 1992 2013 most of the events occurred in intensively built up areas and thus these sinkholes posed a direct threat to the population in the test area 11 sinkholes were detected with a maximum depth of 16 m and maximum dimension of 25 m the root cause of sinkhole formation was the collapse of post mining shallow voids we used satellite radar technology to detect and monitor ground movements potentially associated with the impending sinkholes the findings showed that the application of persistent scatterer interferometry can support the identification of zones where sinkholes will occur given adequate spatio temporal sampling a stack of envisat synthetic aperture radar sar images acquired between march 2003 and august 2010 was used in the analysis and the results confirmed that precursory ground movements were detectable at an early stage of sinkhole development the land subsidence rate observed prior to sinkhole collapse was not constant in time accelerated ground movements within 100 m of an observed sinkhole were detected we conclude that satellite measurements may provide significant support in the early identification of areas prone to sinkhole occurrence

permo triassic granitoids in the northern part of the truong son belt nw vietnam geochronology geochemistry and tectonic implications abstract the northern segment of the truong son belt of northwestern vietnam is composed of three granitoid complexes chieng khuong dien bien and song ma respectively our new la icp ms u pb dating results of magmatic zircons from five granitoid samples in the dien bien and the chieng khuong complexes reveal the existence of three age populations of magma emplacement and crystallization from 276 to 202 ma the new data show that the quartz diorite of the chieng khuong complex is dated to be 271 ma however the previously named dien bien complex exposed at different localities has various ages from 281 to 202 ma of magmatic crystallization the chieng khuong quartz diorite exhibits high mg value 60 7 and enriched sr nd isotopic features i sr 0 713822 end t 11 34 with subduction related geochemical features e g depletion in nb ta and ti and enrichment in rb and la the dien bien gabbroic diorite at muong lay is characterized by relatively depleted isotopic data i sr 0 705050 end t 0 09 and extensive depletion in nb and ta by contrast the dien bien granodiorite and quartz monzonite at dien bien are high k calc alkaline to calc alkaline with high mg values 45 5 to 54 4 and they display enriched sr nd isotopic data i sr 0 714912 to 0 716430 end t 9 58 to 8 85 and post collisional geochemical characteristics e g enrichment in total alkali lile and lree and depletion in eu sr p ti and nb under the framework of regional tectonic evolution the permo triassic magmatism along the northern truong son belt is thus grouped into an early stage from ca 280 to 250 ma and a late stage from 229 to 202 ma the early permian early triassic arc magmatism 280 270 ma and 250 245 ma which is widely distributed in the truong son belt provides reliable information on the continuous subduction of the song ma oceanic plate beneath the indochina block furthermore the magmatism of the dien bien complex at dien bien was formed during post collisional extension at ca 229 to 202 ma diachronous suturing of the eastern tethyan evolution is characterized by the differences in the ages of subduction post collisional evolution along the ailaoshan and the song ma belts

geophysical constraints on the link between cratonization and orogeny evidence from the tibetan plateau and the north china craton abstract understanding the geodynamic process of orogeny and cratonization and their transition is among the key topics of research in evaluating the link between plate tectonics and continental dynamics the tibetan plateau and the north china craton ncc two key areas in mainland china offer excellent laboratories to understand continental tectonics over a broad span of earth history particularly the deep structure of the lithosphere as imaged from geophysical data on the tibetan plateau and the ncc provide important clues in understanding orogeny and cratonization the tibetan plateau is the largest and highest plateau on earth in terms of mean altitude and is an important region for understanding the mechanisms of continent continent collision and cenozoic plateau uplift the ncc is an archean craton that underwent lithospheric disruption during the mesozoic here we reconstruct the main features of the structure of the crust and upper mantle from surface wave tomography and gravity modeling in tibet and its neighboring regions in order to understand the modality of the convergence and collision process between the indian and eurasian plates and the influence of this process on the uplift of the plateau in the ncc geological geochemical geophysical and tectonic investigations demonstrate that lithospheric destruction mainly occurred in the eastern block the crustal structure of the ncc is reconstructed from ambient noise surface wave tomography and the different possible disruption mechanisms are evaluated the vs shear wave velocity tomography results and the density structure of the crust and upper mantle to about 350 km depth demonstrate the lateral variation of the thickness of the metasomatic lid between the south and north of the bangong nujiang suture bns and the west and east of tibet which suggest that the leading edge of the subducting indian slab reaches the bns the subduction angle of indian plate indicates a transition from steep to shallow from the west to east tibet sections depicting the gravitational potential energy suggest that mantle flow contributes to the subduction of the indian plate as far as the bns and the transition from the asthenospheric layer to the metasomatic lid overlaps with the transition from north south shortening in south tibet to eastward tectonic escape in north tibet qiangtang and songpan ganzi blocks both vs and models suggest the following 1 north southward lower crust flow beneath the eastern ncc and interaction between the westward mantle flow and eastward escape flow beneath the central ncc in addition to the earlier proposed mechanisms of delamination and thermal erosion played important roles in the lithospheric disruption of the archean craton 2 mantle flow plays an important role in the continental tectonic transition between neighboring tectonic blocks and within the cycle between orogeny and cratonization

ne sw trending hepu hetai dextral shear zone in southern china penetration of the yunkai promontory of south china into indochina abstract the ne sw trending hepu hetai shear zone extends for about 480 km along the boundary between guangdong and guangxi provinces in the southern part of south china field mapping and kinematic analyses indicate that the zone is characterized by dextral ductile strike slip deformation with an estimated displacement along the fault zone in excess of 500 km studies of synkinematic phengite and gas liquid inclusions in quartz within mylonite suggest that the ductile shear deformation occurred under medium temperature pressure conditions of the greenschist facies and 40ar 39ar analyses of muscovite yield ages of 213 195 ma based on these data and late paleozoic mesozoic paleogeographic data for southern china we propose that the hepu hetai shear zone originated via the penetration of the yunkai promontory of south china into indochina during the triassic

intraplate tectonics in asia a precise age for large scale miocene movement along the ailao shan red river shear zone china tertiary left lateral movement along the 1000 km long ailao shan red river shear zone appears to have played an important role in absorbing post collisional northward penetration of india into asia crustal strike slip shear along this zone caused the formation of a gneiss belt metamorphosed to amphibolite grade including anatectic melting both metamorphism and melting were induced by ductile deformation yielding the possibility to date the major tectonometamorphic event that shaped the ailao shan red river belt 17 u pb isotope analyses were performed on small size fractions of zircon monazite and xenotime extracted from two different leucogranitic layers the two samples are located about 50 km apart in the central segment of ailao shan in structurally well controlled settings where the melts crystallized within the strongly foliated gneisses during late stages of deformation all mineral u pb analyses had to be corrected for excess or deficit amounts of radiogenic 206 pb originating from initial 230 th disequilibrium in the 238 u decay series in monazite such disequilibrium 206 pb reaches 20 of total radiogenic 206 pb the corrected u pb ages of monazite and xenotime lie between 22 1 and 23 9 ma whereas zircon yields significantly discordant u pb ages between 30 5 and 33 9 ma pointing to precambrian material in the magma source region inherited components could also be detected in monazite the set of u pb data shows that monazite and xenotime formed simultaneously in both localities substantiating an early miocene age of 23 0 0 2ma for late kinematic crystallization of anatectic melts in the metamorphic belt of the ailao shan red river shear zone

review on sinkhole monitoring and performance of remediation measures by high precision leveling and terrestrial laser scanner in the salt karst of the ebro valley spain abstract the need to apply sinkhole remediation and monitoring programs is increasing concurrently with the rising engineering impacts of sinkholes in many regions however there is a significant gap in the scientific literature regarding the assessment of the performance of remedial works through subsidence monitoring monitoring techniques have experienced significant advances in the last few years thanks to the advent of new technologies this work presents a review of sinkhole monitoring methods and discusses some practical considerations about their capabilities and limitations it also documents a monitoring program high precision leveling and terrestrial laser scanner and the concurrent remedial works cement based and polyurethane grouting carried out in a highly active sinkhole that affects a flood control dike and the adjacent village of alcala ne spain the subsidence activity in the sinkhole is characterised by progressive sagging and the development of catastrophic nested collapses monitoring data reveal subsidence expansion and acceleration in the sector of the dike treated by polyurethane grouting above the main cavities in contrast subsequent cement based grouting of the large cavities significantly reduced subsidence rates displacement data also indicate substantial subsidence enhancement following flood recession and the associated water table drop buoyancy loss this case study illustrates that high precision leveling and terrestrial laser scanning are adequate complementary methods for monitoring specific sinkholes characterised by very high accuracy and detailed spatial resolution respectively

new data on the indosinian orogeny from central thailand the main aspects of the geosynclinal and orogenic evolution of the petchabun foldbelt in central thailand are described this area was previously thought to be deformed by the indosinian triassic orogeny the new data show that the main orogenic event in thailand can be dated post lower permian pre uppermost permian evidence is given that paleotethys closed on thai territory during this orogenic event the known upper triassic deformations in northern thailand are supposed to be strictly intracontinental and therefore of minor importance

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

tham lod rockshelter pang mapha district north western thailand evolution of the lithic assemblages during the late pleistocene abstract tham lod pang mapha district mae hong son province is one of the rockshelters in the limestone karst of north western thailand the site was excavated from 2002 to 2006 under the direction of one of us r s in the context of the highland archeological project the stratigraphical sequence of the site provided dates ranging from late pleistocene 35 ka tl to late holocene 3000 bp thousands of lithic and faunal remains occur throughout the sequence ceramics and metal items appear in the upper layer holocene noteworthy are the few human burials in the late pleistocene layers this paper presents the lithic material from area 2 sectors s20w10 and s21w10 unearthed from the stratigraphic layers 3 to 10 late pleistocene artefacts are mostly made in locally available grey sandstone which is overwhelming in all the layers the lithic assemblage includes a large proportion 2 3 of rock fragments brought to the site and artificially or thermally broken these are mostly small fragments as some of the artefacts are definitely considered as hoabinhian the detailed technological study of the lithic industry will help in understanding this techno cultural facies and in tracing how the stone artefacts were manufactured used maintained and finally discarded by the hunters gatherers analysis of the whole sequence in tham lod aims at reconstructing the technical evolution in the context of the late pleistocene climatic changes in this part of eurasia

an experimental investigation into the nature of faceted limestone spheroids in the early palaeolithic abstract at some early palaeolithic sites e g ain hanech algeria and el ubeidiya israel archaeologists have uncovered interesting and enigmatic artefact forms that have received special attention these are the faceted limestone spheroids sometimes called boules a facettes or boules polyedriques these artefacts usually between 5 and 10 cm in maximum dimension and weighing between 250 and 1000 g are characterized by their roughly globular shape and the numerous flake scars on their exterior surface previous interpretations of these forms have suggested that they are intentionally shaped tools representative of an evolved pebble tool stage recent experimental replicative and functional studies of artefacts from the oldowan site of ain hanech in north east algeria have demonstrated that these limestone forms may simply be very exhausted cores from flake production these experiments also highlight that there is a continuum from simple limestone core forms choppers polyhedrons to these heavily reduced cores spheroids in the process of core reduction with the heavily reduced faceted spheroids fairly rare in the overall archaeological assemblage at ain hanech

tropical limestone forest resilience and late pleistocene foraging during mis 2 in the trang an massif vietnam abstract in this paper we present a multi proxy study of tropical limestone forest and its utilization by human groups during the significant climatic and environmental upheavals of mis 2 29 11 7 kbp our data are drawn from new field research within the trang an world heritage property on the edge of the red river delta northern vietnam key findings from this study include 1 that limestone forest formations were resilient to the large scale landscape transformation of the sunda continent at the end of the last glaciation 2 that prehistoric human groups were probably present in this habitat through out mis 2 and 3 that the forested insular karst of trang an provided foragers with a stable resource base in a wider changing landscape during the late pleistocene and into the holocene these results have implications for our understanding of the prehistoric utilization of karst environments and resonance for their conservation in the face of climate and environmental change today

duration of strike slip movements in large shear zones the red river belt china abstract sixty four size fractions of zircon monazite xenotime and titanite were dated by the u pb method to temporally and spatially constrain left lateral movements in the red river shear zone between the depths of 15 and 20 km the shearing led to the formation of the high grade metamorphic gneisses that form the bulk of the 4200 m high diancang shan and 3100 m high ailao shan mountain ranges the omnipresence of melt layers and pockets in these gneisses shows that temperatures associated with tectonometamorphism lie at and above the solidus of continental crust and deformation patterns are very homogeneous over the entire length of the belt north of the gneisses subvolcanic bodies intrude unmetamorphosed cover rocks in particular eocene red beds along the projected trend of the red river shear zone for a leucogranitic layer in the diancang shan gneisses an age of 24 2 0 2 ma 2 is obtained for monazite and 22 4 0 2 ma is obtained for xenotime whereas zircon formed through two growth stages at 24 23 ma these ages record solidification of the anatectic melts over a period of at least 1 8 0 4 ma during which left lateral shear was continuously active in the ailao shan gneisses zircon and titanite ages are 26 3 0 3 and 26 1 0 2 ma for two monzonitic bodies and 24 1 0 2 and 22 4 0 2 ma for two pegmatitic layers that occur within the monzonitic intrusions these results show that zircon monazite titanite and probably also xenotime are closed systems for u and pb under melting conditions 650 c therefore the ages date mineral formation in the melt rather than cooling below certain closure temperatures a significantly older age of 35 0 0 1 ma is obtained for a monzonitic subvolcanic intrusion north of the diancang shan gneisses because these intrusions follow the trend of the shear zone they most likely represent the surface expression of early activity along that zone indicating that strike slip movement had already occurred in latest eocene time the total set of u pb ages shows that magmatic and metamorphic activity occurred from 35 to 20 ma strengthening the idea that the red river shear zone absorbed most of the intraplate movements required to compensate the opening of the south china sea between 32 and 16 ma the existence of monzonitic syenitic intrusions along the red river zone implies that melting affected source rocks other than the diancang shan and ailao shan gneiss protoliths potential sources to produce such rocks lie in the deep crust possibly including melts from the mantle consequently the red river shear zone must be a deep rooted structure along which melts migrated to the surface moreover the contemporaneity of shear motion and magma generation suggests that melting occurred in direct relation to strike slip activity

40ar 39ar chronology petrology and geodynamic setting of mesozoic to early cenozoic magmatism from the benue trough nigeria the benue trough is a continental scale intraplate tectonic megastructure which is part of mid african rift system this rift initiated in the latest jurassic was related to the opening of the central and south atlantic oceans mesozoic to early cenozoic magmatism accompanied this evolution two principal magmatic domains are evident the northern and southern benue in the northern domain magmatism is characterized by transitional alkaline basalts and transitional tholeiitic basalts acidic magmatism of peralkaline nature is also present in the southern benue several magmatic districts exhibit alkaline or tholeiitic affinities a detailed chronology of emplacement of this volcanism has been established using the 40 ar 39 ar radiometric method which lead to recognition of three periods of magmatic activity 1 147 106 ma well expressed in the northern benue represefited by transitional basaltic types 2 97 81 ma occurring only in the southern benue represented exclusively by alkaline intrusive rocks 3 68 49 ma restricted also to the southern benue with alkaline intrusions followed by tholeiitic subvolcanic rocks in the light of the general geodynamic evolution a scenario is proposed supported by the three chronological periods the late jurassic to albian magmatism occurred when the equatorial atlantic was still closed contemporaneous with the ne brazilian magmatism both magmatism could represent the forerunners of opening of the equatorial atlantic this activity occurred under a general extensional regime during which crustal strike slip faults gave rise to the emplacement of transitional alkaline basalts transitional tholeiitic basalts erupted along normal faults the second period of activity cenomanian to santonian restricted to the southern benue occurred after the opening of atlantic ocean during a period of decreasing extension this period ended with a santonian compressional episode the last period of activity from late maastrichtian to eocene is characterized by subsidence generated as an isostatic response to the early cretaceous crustal thinning and post rift thermal relaxation of the lithosphere expressed by tertiary e w extension

indosinian nw trending shear zones within the truong son belt vietnam 40ar39ar triassic ages and cretaceous to cenozoic overprints abstract several nw trending ductile and partly mylonitic shear zones cross the truong son belt of central vietnam along the song ma and song ca valleys and north of the kontum block from da nang to aluoi and khe sanh high grade metamorphic rocks of amphibolite facies showing a retrograde evolution and consisting of ortho and paragneisses metavolcanics amphibolites marbles and quartzites are exposed along these structures they display a homogeneous deformation pattern characterized by a generally steeply dipping foliation and a near horizontal to gently plunging mineral stretching lineation indicating a strike slip tectonic regime of deformation along the southernmost fault zone at least various and consistent kinematic indicators including s c structures asymmetric tails of porphyroclasts prove that the strain and metamorphism have been generated by a phase of dominantly non coaxial deformation with a dextral sense of shear 40ar 39ar dating applied on the high grade metamorphic rocks minerals occurring along these zones provide plateau cooling ages closely around 245 ma establishing that this event took place in the lowermost triassic as an early phase of the indosinian orogeny the existence of indosinian movements in vietnam as they have been defined by previous authors during the early century is now accurately confirmed and this is the first insight in the occurrence of ductile strike slip tectonics of indosinian age along nw se fault zones well expressed in central vietnam is a cretaceous thermal and deformational overprint marked by epimetamorphism which took place between 90 and 120 ma as attested by low temperature degassing ages this cretaceous event is not found further north in the song ma zone where younger ages appear as a result of the influence of cenozoic shear movements along the red river fault which displays 20 30 ma ages on the northern flank of song ca in the bu khang phu hoat core complex comparable oligocene lower miocene ages 20 35 ma yielded by biotite and phlogopite reflect a strong overprinting and attest to a rapid uplift of the basement

40ar 39ar single grain dating and mineral chemistry of hornblendes south of the red river shear zone vietnam new evidence for early proterozoic tectonothermal event abstract the pre mesozoic metamorphic belt runs parallel to the day nui con voi red river shear zone in vietnam to the south the belt is mainly composed of hornblende gneisses amphibolite lenses and mica schists five hornblendes from a gneiss and an amphibolite were analyzed chemically and chronologically by electron probe micro analysis epma and 40ar 39ar methods epma analyses show that hornblendes in the gneiss and the amphibolite have significant amount of edenite component and similar average composition however the recalculated fe3 content is significantly heterogeneous in a thin section while total fe is nearly the same among the analyses the rim of each crystal is higher in fe3 fe3 fe2 than the core these chemical and petrological features suggest that the hornblendes have suffered significant oxidation in particular largely in the gneiss 40ar 39ar analyses showed that the gneiss has a significant variation of plateau ages 2089 14 1977 19 and 1873 13 ma among three hornblende grains whereas the amphibolite gives the same plateau ages 2056 14 and 2044 21 ma for two grains all grains of both samples have excess ages in the first few fractions at low temperatures and partial loss ages between the excess and plateau spectra the ca k ratios indicate some disturbed phases for the lower temperature spectra but the partial loss ages are also derived from hornblende phase these facts suggest that hornblende in the gneiss has experienced partial argon loss by oxidation and or thermally activated argon diffusion process however the gneiss and the associated amphibolite have preserved the early proterozoic tectono metamorphic event in the hornblende crystals except for their rims giving new evidence for the early proterozoic event within the pre mesozoic metamorphic belt northern vietnam south of the red river shear zone in indochina

paleomagnetism of the earliest cretaceous to early late cretaceous sandstones khorat group northeast thailand implications for tectonic plate movement of the indochina block abstract a total of 400 samples 33 sites were collected from the earliest cretaceous to early late cretaceous sandstones of the khorat group in the indochina block for paleomagnetic study to unravel the tectonic evolution of the region the sites were adopted from 3 traverses located in the northern edge of the khorat plateau northeastern thailand results indicate that almost all the sandstones exhibit similar magnetic values with an average declination d 31 7 inclination i 30 3 59 7 190 9 k 54 4 and a95 3 7 at reference point 17 30 n and 103 30 e the calculated paleolatitude points are inferred to deviate from the present latitude point by 1 2 2 3 only the lowermost part of the cretaceous sandstones can pass a positive fold test at 95 confidence level the relationship between the virtual geomagnetic poles vgps of cretaceous rocks of the indochina plate in thailand and those of the south china plate advocate that there is a major displacement of indochina along the northwest trending red river and associated faults by about 950 150 km with a 16 0 17 0 clockwise rotation relative to the south china plate during earliest cretaceous times paleomagnetic results of the early late cretaceous indochina plate point to a 20 25 clockwise rotation relative to the present occurring since very late cretaceous 65 myrs early neogene times which may be due to the collision between india and asia

s c mylonites two types of foliations are commonly developed in mylonites and mylonitic rocks a s surfaces related to the accumulation of finite strain and b c surfaces related to displacement discontinuities or zones of relatively high shear strain there are two types of s c mylonites type i s c mylonites described by berthe et al typically occur in deformed granitoids they involve narrow zones of intense shear strain which cut across mylonitic foliation type ii s c mylonites described here have widespread occurrence in quartz mica rocks involved in zones of intense non coaxial laminar flow the c surfaces are defined by trails of mica fish formed as the result of microscopic displacement discontinuities or zones of very high shear strain the s surfaces are defined by oblique foliations in the adjacent quartz aggregates formed as the result of dynamic recrystallization which periodically resets the finite strain clock these oblique foliations are characterized by grain elongations alignments of segments of the grain boundary enveloping surfaces and by trails of grains with similar c axis orientations examples of this aspect of foliation development in mylonitic rocks are so widespread that we suggest the creation of a broad class of s c tectonites and a deviation from the general tradition of purely geometric analysis of foliation and time relationships kinematic indicators such as those discussed here allow the recognition of kilometre scale zones of intense non coaxial laminar flow in crustal rocks and unambiguous determination of the sense of shear

tertiary diachronic extrusion and deformation of western indochina structural and 40ar 39ar evidence from nw thailand the wang chao and three pagodas fault zones cut the western part of the indochina block and run parallel to the red river fault evidence of intense ductile left lateral shear is found in the lansang gneisses which form a 5 km wide elongated core along the wang chao fault zone dating by 40 ar 39 ar shows that such deformation probably terminated around 30 5 ma the wang chao and three pagodas faults offset the north striking lower mesozoic metamorphic and magmatic belt of northern thailand 40 ar 39 ar results suggest that this belt suffered rapid cooling in the tertiary probably around 23 ma these results imply that the extrusion of the southwestern part of indochina occurred in the upper eocene lower oligocene it probably induced rifting in some basins of the gulf of thailand and in the malay and mekong basins in the oligo miocene the continuing penetration of india into asia culminated with the extrusion of all of indochina along the ailao shan red river fault this occurred concurrently with the onset of e w extension more to the south plotting in a geographical reference frame the diachronic time spans of movement on left lateral faults east and southeast of tibet implies that the northward movement of the indian indenter successively initiated new strike slip faults located farther and farther north along its path

rapid drought induced land subsidence and its impact on the california aqueduct abstract the central valley in california is characterized by a semi arid climate prone to droughts a variable surface water supply and immense agricultural areas dependent on groundwater irrigation the groundwater is stored in a complex aquifer system composed of alternating layers of coarse sediments and fine grained sediments acting as confining materials groundwater fluctuations are coupled with both the elastic and inelastic land surface deformation historically observed in the central valley surface deformation poses a hazard to the california aqueduct which supports central valley agriculture and large urban populations in southern california the risk of reduced aqueduct efficacy and expensive repairs compels water resource managers to carefully monitor land deformation in the valley a persistent drought in the region began in 2012 intensified in 2014 and was abruptly alleviated by a wet period from dec 2016 to feb 2018 nasa s uavsar l band synthetic aperture radar acquired 31 high resolution radar images between may 2013 and nov 2018 the interferometric phase difference between acquisitions is used to develop a time series of vertical displacement and identify and track a rapidly forming subsidence feature adjacent to the california aqueduct the surface area of the feature that subsided 10 cm or more by the end of the time series reaches 4452 ha and a 10 5 km segment of the aqueduct this study also incorporates extensometer measurements precise leveling surveys sentinel 1a displacement concurrent water elevation data well construction reports nearby extensometer measurements aquifer material characterization and environmental conditions spatiotemporal data availability limits the appropriateness of calculations and models able to be performed for different sites along the aqueduct we aim to offer insight into heterogeneous subsurface properties and mechanics estimate the permanent loss of aquifer storage volume and identify additional data that would aid water management

anticipating and managing engineering problems in the complex karst environment karst environments are characterized by distinctive landforms and a peculiar hydrologic behavior dominated by subsurface drainage karst systems can be extremely complex heterogeneous and unpredictable due to the wide range of geological and hydrological controlling factors the great variability results in serious problems for engineers and in difficulties to characterize the karstified rock masses and in designing the engineering works to be performed the design and development of engineering projects in karst environments require specific approaches aimed at minimizing the detrimental effects of hazardous processes and environmental problems further karst aquifers that provide approximately 20 25 of the world s drinking water are extremely vulnerable to pollution due to the direct connection between the surface and the subsurface drainage the rapidity of the water flow in conduit networks and the very low depuration capability sinkholes are the main source of engineering problems in karst environments and may cause severe damage in any human structure the strategies and solutions that may be applied to mitigate sinkhole problems are highly variable and largely depend on the kind of engineering structure the karst setting and the typology and size of the sinkholes a sound geological model properly considering the peculiarities of karst and its interactions with the human environment is essential for the design of cost effective and successful risk reduction programs due to the unique direct interaction between surface and subsurface environments and the frequent ground instability problems related to underground karstification management of karst environments is a very delicate matter disregarding such circumstances in land use planning and development inevitably results in severe problems with high economic impacts karst environments require specific investigation methods in order to properly manage and safeguard the sensitive geo ecosystems and natural resources associated with them

bayou corne louisiana sinkhole precursory deformation measured by radar interferometry catastrophic sinkholes are formed through the collapse of natural or human made subterranean caverns and are common in areas with evaporite and carbonate rock despite their danger advance warning of these events is rare we report a measurement of precursory surface deformation of as much as 260 mm derived with interferometric synthetic aperture radar insar and evident over a month before surface collapse at the site of the bayou corne louisiana usa sinkhole that formed in august 2012 data collected by the airborne uninhabited aerial vehicle sar uavsar instrument were used for the study analysis of data acquired from two flight tracks with near opposing imaging geometries reveal a deformation pattern consistent with compressive loading at the surface due to loss of support from a subterranean cavity collapse related to texas brine oxy geismar well 3 the precursor deformation was nearly entirely horizontal i e oriented along the surface and manifested as movement of surface material toward the location where the sinkhole later formed the sinkhole formed in the area with the largest gradient in surface strain but did not cover the full extent of the precursory deformation detected with radar this work suggests that insar data collected operationally for hazard monitoring could in some cases identify sinkhole development before surface collapse and decrease subsequent danger to people and property

the early triassic indosinian orogeny in vietnam truong son belt and kontum massif implications for the geodynamic evolution of indochina new structural field data at various scale and 40ar 39ar geochronological results from the basement rocks in the truong son belt and kontum massif of vietnam confirm that ductile deformation and high temperature metamorphism were caused by the early triassic event of the indosinian orogeny in the range of 250 240 ma a compilation of isotopic data obtained in other countries along the sibumasu indochina boundary broadly indicates same interval of ages this tectonothermal event is interpreted as the result of a synchronous oblique collision of indochina with both sibumasu and south china inducing dextral and sinistral shearing along e w to nw se and n s fault zones respectively the collision along song ma follows the northwards subduction of indochina beneath south china and the subsequent development of the song da zone which in turn was affected by the late triassic indosinian phase of shortening within the indochina plate internal collisions occurred coevally in the early triassic as along the poko suture at the western border of the kontum massif

new insights into the triassic sedimentary environment of the eastern parts of the song da and sam nua basins alongside the indosinian song ma suture northern vietnam this study documents the sedimentology structures and foraminifer content of triassic formations from the eastern part of the truong son belt northern vietnam sedimentary rocks in the eastern song da and sam nua basins occur on both sides of the middle triassic song ma suture zone that separates the indochina block from the south china block the main outcomes of our study include detailed stratigraphic successions that we have established for the two basins new foraminifer determinations indicate a middle to late triassic age for the carbonate deposition the depositional settings of the carbonate deposits and their deformation patterns support a southward subduction beneath the indochina block ending with the collision with the south china block during the middle triassic moreover our new biostratigraphic dating of the stratigraphic successions can be used to compare the triassic carbonate platforms from northern vietnam with other platforms elsewhere including those that have already been well documented in indonesia

definition of sinkhole triggers and susceptibility based on hydrogeomorphological analyses sinkholes represent a geological risk that is often underrated mainly due to its very localized nature in fact sinkholes occur only under particular circumstances and typically affect relatively small areas despite these characteristics the difficulty in forecasting the precise location and timing of their sudden collapse creates serious problems for civil protection authorities and urban planners in this framework identifying the mechanism and thus the triggering factor of sinkholes is strategically pivotal in developing management plans the present paper addresses the sinkhole prone area of il piano elba island central italy the integration of hydrogeological surveys coupled with a thorough study of historical maps and aerial photographs suggests that the main triggering factor in this area may not be related to water pumping from the karst aquifer as initially hypothesized instead sinkholes appear to be caused by ravelling and erosive processes occurring entirely in the sedimentary cover when heavy rainfall induces water overpressure within the superficial aquifer

the human settlement of central iberia during mis 2 new technological chronological and environmental data from the solutrean workshop of las delicias manzanares river valley spain abstract the recent excavations 2008 2009 conducted at the open air site of las delicias located in the manzanares river valley madrid have revealed new important data for the understanding of the human settlement of central iberia during solutrean times in this paper we present a geomorphological and taphonomic study of the pleistocene deposits of las delicias a technological analysis focused on the bifacial lithic reduction processes documented at the site new optically stimulated luminescence dates and new palynological data together with the existence of numerous solutrean lithic assemblages from the early 20th century excavations of the manzanares terraces these new data highlight the importance of the manzanares valley as a focus of solutrean settlement not only related to flint procurement but also to foraging activities moreover they require reconsideration of central iberia as a virtually unpopulated region during the late pleniglacial mis 2 and of the associated idea of its cultural dependence on the coastal areas of the iberian peninsula we propose new avenues of research aimed at approaching the central region of iberia in its own cultural and ecological terms

establishing statistical confidence in cortex ratios within and among lithic assemblages a case study of the middle paleolithic of southwestern france abstract recent studies have demonstrated the usefulness of the cortex ratio for quantifying the cortex composition in lithic assemblages and as a viable index of prehistoric artifact transport yet the lack of means for assigning statistical confidence to archaeologically observed cortex ratios inhibits the approach s utility for objective comparisons and interpretation here we derive statistical confidence for archaeological cortex ratios through monte carlo and resampling techniques experimental data with known geometric properties and measured cortex values were employed as a reference for attaching a probability to an archaeological assemblage s cortex ratio the method is demonstrated on assemblages from the middle paleolithic sites of roc de marsal pech de l aze iv and combe capelle bas in southwestern france

sinkhole precursors along the dead sea israel revealed by sar interferometry the water level in the dead sea israel and jordan has been dropping at an increasing rate since the 1960s exceeding one meter per year during the last decade this drop has triggered the formation of sinkholes and widespread land subsidence along the dead sea shoreline resulting in severe economic loss and infrastructural damage in this study the spatiotemporal evolution of sinkhole related subsidence and the effect of human activities and land perturbation on sinkhole development are examined through interferometric synthetic aperture radar measurements and field surveys conducted in israel during 2012 interferograms are generated using cosmo skymed satellite images and a high resolution 0 5 m pixel elevation model obtained from lidar measurements as a result of this unique combination of high resolution data sets millimeter scale subsidence has been resolved in both natural and human disturbed environments precursory subsidence over a period of a few months occurred before the collapse of all three sinkhole sites reported in this study the centers of the subsiding areas migrated possibly due to progressive dissolution and widening of the underlying cavities filling of newly formed sinkholes with gravel and mud injections into drill holes seem to enhance land subsidence enlarge existing sinkholes and form new sinkholes apart from shedding light on the mechanical process the results of this study may pave the way for the implementation of an operational sinkhole early warning system

from blunt to cutting distinguishing alternating method flakes in early stages on rounded blanks abstract two main knapping strategies can be used to start bifacial reduction on a lithic cobble or nodule the alternate strategy in which first one face is knapped and then the other and the alternating strategy in which both faces are removed in the same sequence interspersing core about turns between strikes flaking reduction of spherical and elliptical blanks cobbles or nodules is a common knapping process documented in many archaeological records rounded and thick edges require different fracture parameters and give rise to constraints in terms of viable knapping methods when analysing abandoned cores it is only possible to see the last strikes so it is important to know how they were shaped or exploited in the earlier knapping stages in order to understand the entire reduction process as cortical flakes are the direct evidence of the first reduction phases we undertook an experimental programme for the purpose of comparing the first flakes generated using the alternate and alternating knapping strategies we have focused our efforts on identifying and diagnosing distinctive features produced by each strategy in the first or cortical flakes our study indicates that several platform attributes can be considered as diagnostic features to differentiate between the alternate and alternating knapping strategies and that this kind of analysis can be translated to archaeological assemblages

insar based modeling and analysis of sinkholes along the dead sea coastline sinkholes commonly form by subsurface dissolution cavities that collapse after the overlying layers become mechanically unsupported sinkholes along the dead sea shorelines are preceded by associated with and followed by gradual surface subsidence that accompanies the cavities growth we exploit satellite radar interferometry interferometric synthetic aperture radar to resolve temporal and spatial relationships between gradual subsidence and sinkhole collapse the geometry of the deflating cavity roof is determined by elastic inverse modeling of the surface displacements a coulomb failure stress criterion is applied to calculate the stress field induced by the deflating cavity at the ground surface we find that the induced stress field favors generation of sinkholes at the perimeters of the subsiding areas rather than at their centers in agreement with field observations providing important information for sinkhole hazard assessment further our analysis suggests that short term deformation in consolidated gravel layers at shallow depths could be approximated by simple elastic modeling

evolution of sinkholes over wink texas observed by high resolution optical and sar imagery abstract two caprock and cover collapse sinkholes wink sinks 1 and 2 in winkler county texas collapsed in 1980 and 2002 respectively they are located in a region underlain by the salado formation on the eastern edge of the delaware basin the sinkhole collapses were associated with intense hydrocarbon drilling and production activities in the hendrick oilfield production records and prior investigations imply the sinkholes developed after salt dissolution due to freshwater intrusion cavity formation roof failure and successive upward cavity migration high resolution 1 m aerial photography shows the ensuing expansion of wink sink 2 from 2002 through 2010 and relative stability of the ground surface after 2010 very high resolution 25 cm staring spotlight mode terrasar x reveals the spatiotemporal details of wink sinkhole deformations the vicinities around the two existing sinkholes wink sinks 1 2 deformed at a rate of 5 cm yr in line of sight los direction from october 2015 to march 2016 and the deformation was possibly caused by the gradual deposit of the debris from overlying unconsolidated alluvium and santa rosa sandstones infilling the cavity after the sinkhole collapse specifically the largest deformation of 53 cm yr in los direction was found 1 km east of wink sink 2 our study suggests that severe drought in 2011 widened and created fractures as well as ground fissures in the rocks overlying and underlying the salt formation due to the increased effective stress fractures ground fissures and the abandoned unplugged boreholes or improperly completed wells opened one or more vertical pathways of freshwater from groundwater flow and precipitation toward the salt bed finally causing the rapid salt dissolution and the opening of new cavities to explain the onset of a rapid subsidence near the wink sinkholes our study considers the combined effect of natural perturbation i e drought rock fractures ground fissures subsurface drainage precipitation and anthropogenic effects i e improper well control our method to explore high resolution imagery can be applied to characterize the sinkhole deformation and mitigate sinkhole related geohazards

comment on discovery of the fossiliferous cu brei formation lower devonian in the kon tum block south viet nam tong dzuy thanh than duc duyen nguyen huu hung bui phu my abstract the publication of tong dzuy thanh et al calls for two remarks the metamorphism in the kon tum block cannot be younger than permian because the outcrop they describe is not metamorphic their very interesting discovery is a new piece of evidence for the exotic origin of the dien binh series

the influence of raw material size on stone artefact assemblage formation an example from bone cave south western tasmania this paper specifically examines the influence of raw material size on stone artefact assemblage formation in conjunction with two behavioural assemblage formation processes reduction intensity and artefact transport the aim is to establish whether raw material size can influence the way in which reduction intensity and artefact transport form a stone artefact assemblage and should a significant influence be established whether this has any bearing on human behavioural reconstructions this is first investigated in an experimental setting followed by an archaeological setting using a quartzite and chert assemblage from bone cave in south western tasmania reduction intensity and artefact transport are respectively measured using the scar density index flake to core ratio non cortical to cortical flake ratio and cortex ratio while tool blank sizes are also reconstructed the combined experimental and archaeological analyses find that raw material size variation is capable of exerting a substantial influence on stone artefact assemblage formation this particularly with reference to the nature of change in stone artefact assemblages both reduction intensity and artefact transport will alter assemblage composition at faster rates when nodule sizes are smaller this can have significant implications for intra and inter site reconstructions of past human behaviour

the permo triassic paleotethys in mainland southeast asia and adjacent parts of china aspects of the geodynamic evolution of mainland southeast asia and china are discussed in consideration of the permo triassic paleotethys problem it is shown that all sutures in thailand vietnam and yunnan already closed during the paleozoic era and that the entire region must be regarded as part of the northern continents the permo triassic paleotethys must be expected south of tibet and in burma

a functional approach to the use of the earliest blade technology in upper paleolithic hokkaido northern japan abstract to understand the behavioral significance of the emergence and proliferation of blade technology in the northeastern asian upper paleolithic this paper explores the function of the earliest blade technology in hokkaido northern japan through an integrated analysis of edge morphology and use wears on blade tools from the last glacial maximum lgm assemblage of kawanishi c although varied edge morphologies i e straight convex concave denticulate have been distinguished the results of use wear analysis suggest that morphological differences of edges are not related to specific functions straight and convex edges experienced different use lives and use trajectories both straight and convex edges were principally served for cutting sawing and whittling while some edges changed their functions to scraping as edge resharpening blunted the edges the results of use wear analysis also suggest that lgm blades were intensively used for performing a narrow range of activities e g skin and meat stripping because this blade technology differs from the dominant flake technology in lgm hokkaido lgm foragers were able to employ it to perform intensive processing activity to exploit critical faunal resources that may have been sporadically clumped in the landscape

natural versus human control on subsurface salt dissolution and development of thousands of sinkholes along the dead sea coast one of the most hazardous results of the human induced dead sea ds shrinkage is the formation of more than 6000 sinkholes over the last 25 years the ds shrinkage caused eastward retreat of underground brine replaced by fresh groundwater which in turn dissolved a subsurface salt layer to generate cavities and collapse sinkholes the areal growth rate of sinkhole clusters is considered the most pertinent proxy for sinkholes development analysis of light detection and ranging lidar digital elevation models dems and interferometric synthetic aperture radar insar allows translation of the areal growth rate to a salt dissolution rate of the salt layer revealing two peaks in the history of the salt dissolution rate these peaks cannot be attributed to the decline of the ds level instead we show that they are related to long term variations of precipitation in the groundwater source region the judea mountains and the delayed response of the aquifer system between the mountains and the ds rift this response is documented by groundwater levels and salinity variations we thus conclude that while the ds level decline is the major trigger for sinkholes formation the rainfall variations more than 30 km to the west dominate their evolution rate the influence of increasing rainfall in the judea mountains reaches the ds at a typical time lag of four years and the resulting increase in the salt dissolution rate lags by a total time of 5 6 years

new paleomagnetic constraints on the extrusion of indochina late cretaceous results from the song da terrane northern vietnam abstract samples were collected for paleomagnetic investigations from the upper cretaceous yen chau formation in the song da terrane 21 7 n 103 9 e bounded by the ailao shan red river fault system and song ma fault in an attempt to examine extrusion tectonics of east asia primary nature of the high temperature 600 690 c component of magnetization from 13 sites is supported by a positive fold test the tectonic corrected data provides the characteristic late cretaceous paleomagnetic direction for the song da terrane d 6 4 i 32 0 with 95 8 5 n 13 sites corresponding to a paleopole lying at 82 9 n 220 7 e a95 6 9 comparison with coeval paleomagnetic poles for the neighboring tectonic blocks indicates no latitudinal translation of the son da terrane with respect to the south china block whereas the shan thai block and the southern part of the indochina block revealed a southward displacement of 10 5 9 5 in latitude with respect to the song da terrane we conclude that the southeastern segment of the ailao shan red river fault system to the east of the dien bien phu fault is not a demarcation of the extruded indochina peninsula the indochina block extruded probably along some faults between the song da terrane and the khorat plateau

rapid subsidence in damaging sinkholes measurement by high precision leveling and the role of salt dissolution abstract investigations dealing with subsidence monitoring in active sinkholes are very scarce especially when compared with other ground instability phenomena like landslides this is largely related to the catastrophic behaviour that typifies most sinkholes in carbonate karst areas active subsidence in five sinkholes up to ca 500 m across has been quantitatively characterised by means of high precision differential leveling the sinkholes occur on poorly indurated alluvium underlain by salt bearing evaporites and cause severe damage on various human structures the leveling data have provided accurate information on multiple features of the subsidence phenomena with practical implications 1 precise location of the vaguely defined edges of the subsidence zones and their spatial relationships with surveyed surface deformation features 2 spatial deformation patterns and relative contribution of subsidence mechanisms sagging versus collapse 3 accurate subsidence rates and their spatial variability with maximum and mean vertical displacement rates ranging from 1 0 to 11 8 cm yr and 1 9 to 26 1 cm yr respectively 4 identification of sinkholes that experience continuous subsidence at constant rates or with significant temporal changes and 5 rates of volumetric surface changes as an approximation to rates of dissolution induced volumetric depletion in the subsurface reaching as much as 10 900 m3 yr in the largest sinkhole the high subsidence rates as well as the annual volumetric changes are attributed to rapid dissolution of high solubility salts

what attributes are important for the measurement of assemblage reduction intensity results from an experimental stone artefact assemblage with relevance to the hoabinhian of mainland southeast asia abstract our understanding of variation in the technology of flaked stone artefacts from mainland southeast asia during the terminal pleistocene and holocene periods has improved little since they were originally labelled hoabinhian in 1932 chronological and geographical variation has been described in terms of typological differences but there are few anthropological explanations of lithic diversity and change an analysis of an experimentally produced hoabinhian assemblage is undertaken here to show which flake variables are significant indicators of assemblage reduction intensity the results show that recording the presence of overhang removal interior platform angle and percentage of dorsal cortex will provide robust data on the extent of assemblage reduction a new method for detecting assemblage variation based on the location of dorsal cortex on flakes is also presented and experimentally verified these methods are designed to take advantage of the typical geometry and reduction patterns of hoabinhian assemblages these findings provide another tool to build anthropological explanations of hoabinhian archaeology

timing of metamorphism of the lansang gneiss and implications for left lateral motion along the mae ping wang chao strike slip fault thailand the mae ping fault mpf western thailand exhibits dominantly left lateral strike slip motion and stretches for 600 km reportedly branching off the right lateral sagaing fault in myanmar and extending southeast towards cambodia previous studies have suggested that the fault assisted the large scale extrusion of sundaland that occurred during the late eocene early oligocene with a geological offset of 120 150 km estimated from displaced high grade gneisses and granites of the chiang mai lincang belt exposures of high grade orthogneiss in the lansang national park part of this belt locally contain strong mylonitic textures and are bounded by strike slip ductile shear zones and brittle faults geochronological analysis of monazite from a sample of sheared biotite k feldspar orthogneiss suggests two episodes of crystallization with core regions documenting th pb ages between c 123 and c 114 ma and rim regions documenting a significantly younger age range between c 45 37 ma these data are interpreted to represent possible magmatic protolith emplacement for the lansang orthogneiss during the early cretaceous with a later episode of metamorphism occurring during the eocene textural relationships provided by in situ analysis suggest that ductile shearing along the mpf occurred during the latter stages of or after this metamorphic event in addition monazite analyzed from an undeformed garnet two mica granite dyke intruding metamorphic units at bhumipol lake outside of the mae ping shear zone produced a th pb age of 66 2 1 6 ma this age is interpreted to date the timing of dyke emplacement implying that the mpf cuts through earlier formed magmatic and high grade metamorphic rocks these new data when combined with regional mapping and earlier geochronological work show that neither metamorphism nor regional cooling was directly related to strike slip motion

geological development of the central and south vietnamese margin implications for the establishment of the south china sea indochinese escape tectonics and cenozoic volcanism abstract the vietnamese margin forms a key region to the understanding of escape tectonics and the development of the south china sea scs the existing geological reconstructions of the region are restricted to studies of single basins are based on limited amounts of geophysical data or analysis of onshore geological features these models are critically assessed on the basis of interpretation of the most comprehensive 2 d digital seismic database published to date within the area combined with a thorough analysis of existing literature and a new model is presented the vietnamese margin is underlain by a series of paleogene rift basins established through southeastward extrusion of indochina the east vietnam boundary fault evbf forms the almost 1000 km long seaward continuation of the left lateral ailao shan red river shear zone asrrsz toward the southern half of the phu khanh basin the evbf breaks up into discrete segments and splays into the se directed tua hoa fault zone paleogene faults splayed from the evbf and the mae ping shear zone and accommodated the coeval motion of these two major left lateral structural lineaments during the late oligocene basin inversions offshore occurred contemporaneously with initial right lateral inversion along the mae ping shear zone and the onset of major uplift of the metamorphic core complexes along the asrrsz it is suggested that a dramatic change of the regional stress pattern occurred in response to the northward movement of india and the effective coupling of the west burma block and india the later resulting in broadening of the indenting continental mass after the mid oligocene left lateral movements across the offshore evbf decreased and eventually ceased later onshore sinistral movements were accommodated by internal shortening and local clockwise block rotations within the shan thai terrain renewed rifting offshore south vietnam resulted from the jump of the scs spreading axis and subsequent neogene southwestward propagation of continental break up the neogene opening of the scs is viewed as a consequence of a slab pull associated with subduction of the proto scs underneath borneo as offshore neogene escape tectonism had virtually ceased during this phase of rifting right lateral transtension is inferred along n to nw oriented fault zones in the phu khanh and the nam con son basins rifting and by inference seafloor spreading continued until the end of middle miocene time although at significantly reduced rates during the final 5 10 ma termination of seafloor spreading is marked by a distinct latest middle miocene unconformity in the nam con son and the southern phu khanh basins neogene volcanism resulted in the build up of several magmatic structures across the central and south vietnamese margin and induced reactivation of older faults in the phu khanh basin the offshore magmatism heralded widespread volcanism onshore southern indochina associated with a latest neogene uplift and denudation event the uplift led to significantly increased siliciclastic accumulation rates offshore which repressed widespread carbonate deposition

impact of differential tectonic subsidence on isolated carbonate platform evolution triassic of the nanpanjiang basin south china the nanpanjiang basin of south china contains four exceptionally well exposed isolated triassic carbonate platforms detailed mapping of two dimensional transects and description of stratigraphic sections allow the reconstruction of facies architecture sequence stratigraphy and evolution of the platforms biostratigraphy magnetic susceptibility profiles and volcanic ash horizons allow chronostratigraphic correlation and thus a basinwide evaluation of mechanisms controlling platform evolution a comparison of platform architecture demonstrates that southerly platforms have substantially greater thickness backstepping geometry pinnacle development and earlier drowning that resulted from greater tectonic subsidence proximal to a probable convergent margin along the southern perimeter of the basin felsic volcanics thicken southward and contributed to the termination of the southernmost platform indicating the development of a volcanic arc along the southern margin of the south china tectonic block the northernmost isolated platform had greater longevity and lesser accumulation and lacks backstepping and pinnacle phases of development basin margin intertonguing relationships or lack thereof demonstrate that earlier siliciclastic influx into the basin to the south and concurrent starved basin conditions to the north impacted the evolution of platform margin geometries comparative analysis of platform evolution shows that the timing and rates of tectonic subsidence controlled the timing of platform termination by drowning backstep geometries pinnacle development and overall platform thickness the timing of siliciclastic basin fill dictated differences in platform margin geometries such as slope angle relief above basin floor and the presence or absence of basinward platform progradation despite the dramatic differences in platform architecture eustatic sea level fluctuations imparted a basinwide sequence stratigraphic signal

measuring core reduction using 3d flake scar density a test case of changing core reduction at klasies river mouth south africa a new core reduction index is presented calculated as the ratio of flake scar number to 3d surface area sdi the index is tested experimentally on five types of core blade discoid levallois biface and multiplatform cores and then applied to the core assemblages from five sub stages of the middle stone age at klasies river mouth south africa preliminary results indicate that the sdi possesses the desirable attributes of a successful reduction index and is a significant improvement on traditional proxy measures of core reduction the results of the archaeological case study confirm previous untested observations that cores from the howiesons poort and msaiii sub stages are more heavily reduced than preceding and following stages and that local and exotic raw materials as well as different types of cores are all more heavily reduced during these periods the sdi fills a significant lacuna in available core reduction measures

zircon and monazite upb dating of the doi inthanon core complex northern thailand implications for extension within the indosinian orogen abstract the doi inthanon metamorphic core complex occupies a prominent central position within the northwestern thai gneiss belt which has been inferred to be as old as precambrian and as young as permo triassic u pb dating of zircon from core orthogneisses of the complex suggests that the orthogneisses were derived from granitic protoliths with essentially the same late triassic early jurassic age as the mae cham pluton 205 3 4 ma to the west of the doi inthanon complex monazite ages from the orthogneisses indicate that low pressure and high temperature metamorphism and migmatitization occurred in the late cretaceous 84 72 ma limited published radiometric age data from elsewhere in the migmatitic gneiss belt suggest that widespread minor plutonism accompanied this thermal event a younger u pb data of 26 8 0 5 ma for zircon and monazite from the mae klang granite which intruded mylonitic gneisses on the eastern side of the doi inthanon complex indicates that there was also significant plutonism in the late oligocene these u pb ages constrain the development of the complex and hence of the migmatitic gneiss belt as a whole to an interval between late cretaceous and early miocene ductile shearing uplift and tectonic denudation via detachment faulting chronologically overlap the initiation of extensional basin development to the east and southeast of the gneiss belt and imply a genetic connection thus oligocene early miocene thermal rifting from the gulf of thailand northward into mainland thailand may have been the direct product of crustal extension rather than the transtensional product of regional strike slip faulting