provenance of neoproterozoic and early paleozoic siliciclastic rocks of the tepla barrandian unit bohemian massif evidence from u pb detrital zircon ages abstract new la icp ms u pb detrital zircon ages from ediacaran and paleozoic siliciclastic rocks are used to constrain provenance and paleogeographic affinities of the tepla barrandian unit tbu in the centre of the bohemian massif central europe czech republic the samples taken span the period from 635 ma to 385 ma and permit recognition of provenance changes that reflect changes in geotectonic regime detrital zircon age spectra of two ediacaran one lower cambrian and three upper ordovician samples resemble the ages known from the nw african proportion of gondwana particularly the trans saharan belt while three rocks from higher lower cambrian to lowermost ordovician strata contain detritus that may have been derived exclusively from local sources the age spectrum of the devonian rock is a combination of the nw gondwanan and local features these new findings in combination with a wide range of published data are in agreement with a neoproterozoic subduction related setting at the margin of gondwana followed by a cambrian early ordovician rifting stage and an ordovician passive margin setting furthermore the data are in favour of a position of the tbu at the gondwanan margin throughout pre variscan times

post glacial sea level rise from a coral record at huon peninsula papua new guinea dating of coral reef terraces can provide a record of changes in sea level which should be pronounced during the transition between glacial and interglacial periods cores drilled from coral reefs at barbados in the equatorial west atlantic1have revealed the sea level changes that occurred during the younger dry as event at the end of the last glacial maximum 11 000 yr bp it has not been known however whether pacific coral reefs can grow at a rate sufficient to keep up with the rise in sea level during such a transition here we report results obtained from a 52 m drill core from the post glacial reef at huon peninsula papua new guinea spanning the interval from 7 000 to 11 000 14c yr bp which show that coral growth kept pace while the relative sea level rose by 50m although the tectonic environment is very different from that at barbados the two records compare well when corrections are made for local tectonic uplift showing that sea level rise was similar at both locations the rate of rise was greatest between 9 000 and 10 00014c yr bp corresponding to the time of the younger dryas

geochemical evidence for the volcanic arc tectonic setting of the dhanjori volcanics singhbhum craton eastern india geochemical data on the dhanjori volcanics of the singhbhum craton indicate that they range from basalt to andesite and show an iron enrichment trend various chemical characteristics suggest that they are differentiated along the trend similar to that of orogenic suites and have a strong affinity with island arc tholeiites the field relationships as well as other geological information also support this conclusion and indicate their eruption on a thin continental margin it is inferred that the dhanjori volcanics were probably erupted as a result of plate convergence in northern singhbhum with subduction of oceanic crust below the singhbhum craton

geochemistry and origin of late archean volcanics from the ventersdorp supergroup south africa abstract the ventersdorp supergroup 2700 2750 ma is comprised chiefly of mafic to intermediate subaerially erupted volcanics with smaller amounts of clastic sediments the lower unit the klipriviersberg group consists of basal basaltic komatiites overlain by basalts which show a progressive increase in mg number and ni content and a decrease in incompatible element contents with increasing stratigraphic height volcanics of the overlying platberg and pniel groups consist of basaltic andesites and andesites and some felsic volcanics all ventersdorp volcanics exhibit a subduction zone geochemical component and are similar in incompatible element distributions to volcanics from continental margin arc systems both tholeiitic and calc alkaline trends occur in the ventersdorp succession with the former dominating crustal contamination appears to have played a minor role in the evolution of ventersdorp magmas with the exception of basaltic komatiite the klipriviersberg lavas can be related by progressive melting of a garnet lherzolite source containing a subduction zone component followed by up to 30 of shallow fractional crystallization the basaltic komatiite can be produced from the same source at higher temperatures and the pniel lavas by shallow fractional crystallization of basaltic komatiite the platberg volcanics must come from a within plate enriched mantle source and mafic and felsic members of this group can be related by shallow fractional crystallization geochemical and geologic data are consistent with a model for ventersdorp magmas involving a subduction zone in which klipriviersberg and pniel magmas are produced from the mantle wedge and platberg magmas come from an enriched mantle lithosphere with a superimposed subduction zone component secular trends in klipriviersberg lavas can be explained by progressive adiabatic melting of an ascending plume rooted in the mantle wedge

late pleistocene to holocene environmental changes as recorded in the sulfur geochemistry of coastal plain sediments southwestern taiwan abstract a core drilled at san liao wan in the southwestern coastal plain of taiwan has been analyzed for total sulfur contents isotopic values as well as ratios of pyritic sulfur to organic carbon our results demonstrate a close relationship between late pleistocene sea level change and the proxies generated in this study the inorganic sulfur contents indicate that at our study site the holocene transgression started at 11 ka and remained under seawater for thousands of years until the late holocene corresponding to a depth of 20 m in the study core the uppermost 20 m of core shows relatively high total organic carbon toc and 34s of inorganic sulfur suggesting a transitional environment such as muddy lagoon or marsh before the site turned into a modern coastal plain in the lower part of the core at depths of 110 145 m corresponding ages of 12 30 ka low sulfur contents are recorded probably indicating fluvial sediments deposited during the oceanic isotope stage ois 2 a sea level lowstand the lower part of the core roughly within ois 3 records at least two transgressions although the transgressional signals may be somewhat obscured by subsequent weathering the reworked origin of organic matter reported in previous studies is confirmed by our organic sulfur data however the marine organic source was periodically dominant the modern high sulfate concentrations in pore water have no correlation to the other sulfur species in the sediments probably indicating that the sulfate migrated into the site subsequent to early diagenesis

holocene tectonic uplift on the hua tung coast eastern taiwan abstract we used radiometric dates from 19 sites to determine the holocene uplift rates of the 140 km long hua tung coast in eastern taiwan these rates ensure that the formation of major marine terraces on the coast several tens of meters in height is related to the deglacial relative sea level cycle with which the uplift rates were further constrained by the elevations of the marine terrace elements uplift rates are less than 4 mm yr in the northernmost 30 km long coast and are 4 7 mm yr in the adjacent 30 km long coast the rest of the coast is generally uplifted 7 9 mm yr with local troughs 700 m and high 40 m mudstone platforms are observed to slope below the sea level these changes in uplift rate or style are all accommodated on the surface by warping most of them are irrelevant to the known bedrock structures suggesting a change in uplift style and perhaps also mechanics of the coast during the holocene

active deformation front delineated by drainage pattern analysis and vertical movement rates southwestern coastal plain of taiwan abstract orogenesis in taiwan results from an arc continent collision between the eurasian plate and the philippine sea plate the southwestern part of taiwan absorbs active shortening as evidenced by rapid crustal deformation and frequent earthquakes southwestern taiwan may be subdivided into three tectonic geomorphic domains including the plain pl the tilted tableland tt and the low hills lh based on geomorphology drainage pattern and stratigraphic records the pl domain is the westernmost and is characterized by meandering rivers with relatively low surface slope and river gradient but high river sinuosity the tt domain has slightly tilted terraces with river meanders and many tributaries are developed on its surface anomalous river sinuosity occurs as a result of active tectonics the lh domain has higher elevation and deformed geomorphic surfaces associated with a dissected landscape this domain also has high stream gradients with low sinuosity which may indicate active deformation we define crustal deformation using holocene deposits and radiocarbon dating in addition to geomorphic analysis that suggests a blind thrust may exist between the pl and tt domains this blind thrust may indicate the position of the active deformation front of the orogenic belt of southwest taiwan

evidence of a paleoproterozoic basement in the moroccan variscan belt rehamna massif western meseta abstract for the first time an eburnian magmatic event has been identified in the rehamna massif moroccan variscan belt western meseta located north of the south meseta fault the best estimate of the crystallization age of rhyolitic porphyry is given by a weighted mean 207pb 206pb age of 2050 6 3 ma rhyacian orosirian the new u pb age obtained for rhyolitic porphyry from the rehamna massif is of great relevance for improving geological knowledge about the boundaries of the wac because i it overlaps the older eburnian magmatic event described in the anti atlas belt and the icartian magmatic event of the european variscan belt ii this suggests that exists paleoproterozoic basement in the western meseta a hundred kilometers further to the north of the south meseta fault as old continental crust slivers preserved in the cadomian and variscan belts and iii this means that the cambrian transgression in the western meseta probably took place based on a more complex structural architecture affecting the precambrian basement composed not only of ediacaran rocks as has been suggested in the literature but also with paleoproterozoic rocks ca 2 05 ga as discovered in this study

regional magnetic overprinting of witwatersrand supergroup sediments south africa shales from the late archean witwatersrand supergroup of south africa yield stable wellgrouped remanent magnetizations after thermal and alternating field demagnetization virtual geomagnetic poles from 17 sites located throughout the central and western parts of the basin indicate that rocks of the basin were remagnetized after folding a paleomagnetic fold test shows that the fisherian precision parameter k decreases from 22 to 3 after restoring the beds to paleohorizontal illite crystallinity indices show that the remagnetized samples were subjected to at least middle greenschist facies temperatures whereas magnetic blocking temperature estimates indicate upper greenschist facies temperatures a k ar age obtained from clays of 1945 40 ma 2 is assigned to this metamorphic event the new paleomagnetic pole obtained from the witwatersrand basin sites 19 n 46 e k 22 a95 8 is consistent with other 1950 2050 ma poles from southern africa confirming independently the k ar age the distinctive overprint direction seen in shale specimens may be useful as a directional marker for orienting deep bore cores

basalt geochemistry and tectonic settings a new approach to relate tectonic and magmatic processes abstract in recent years the effects of mantle heterogeneity crustal contamination mantle metasomatism and other non differentiation related processes on the composition of basalts have been documented in various well defined tectonic settings the fact that none of these effects are unique to a specific tectonic setting illustrates the fundamental logical error in the formulation of discrete tectonomagmatic classifications of basalts using empirical discrimination diagrams a more meaningful approach to the problem of tectonics and basalt geochemistry is careful stratigrapghc geochemical studies which document important temporal and spatial variations in melt compositions using this approach it may be possible to identify certain sequences of compositions which are characteristic of specific tectonic cycles the first problem encountered in any such study is the identification of significant compositional variations within a single tectonic province the niobium normalized spidergram presented here is a simple yet powerful tool for rapid detection of source heterogeneity or other non differentiation related compositional variations in basalts

holocene sea level changes in french polynesia abstract new data on holocene sea levels have been obtained in 28 atolls and 10 high islands in the society tuamotu gambier and austral islands in an area of the south pacific as wide as western europe sea level indicators are often very accurate 0 1 m and include exposed corals abandoned algal ridges and reef frameworks in growth position emerged tidal notches and skeletal reef conglomerates in which the position of the former low water level at the time of cementation has been determined by petrological analysis over 110 new samples have been dated by radiocarbon the overall pattern is that of a msl standstill at 0 8 1 0 m between 5000 and 1250 yr b p a set of radiocarbon dated samples covering the period 4500 1250 yr b p almost continuously is evidence that lasting msl drops could not ever have occurred below 0 7 m throughout this time the highest sea level peak about 1 0 m seems to have been reached between 2000 and 1500 yr b p since 1500 yr b p msl has been dropping gradually from about 1 0 m to the present position which has been reached only recently some islands show however a slightly different pattern the holocene emergence is smaller than average in moorea and tahiti and larger in rurutu makatea anaa and possibly hereheretue some data suggest also the possibility of a slight increase in the holocene emergence towards the south possible geodynamic isostatic oceanic and climatic causes of the sea level variations observed are discussed

coastal quaternary morphologies on the northern coast of the south china sea china and their implications for current tectonic models a review and preliminary study marine terraces tidal notches and sediments along a 1200 km long stretch of the northern coast of the south china sea passive margin were studied and divided into five areas with varying tectonic characters up to three marine terraces occur that have elevations reaching up to 60 m above mean sea level amsl and two marine notches occur up to 11 m amsl chronology of the morphologies and deposits was obtained mainly by comparison with quaternary sea levels derived from the oxygen isotope curve however prior to the last interglacial highstand mis 5e c 125 ka evidence of history of events is less well constrained leading to less precision on sea level positions prior to mis 5e using the morphological features of mis 5e as a marker mean coastal uplift rates in the last c 125 ka range from 0 07 mm yr to 0 18 mm yr the pattern of deformations is slightly higher than those observed on passive margin coasts in other parts of the world the cause of uplift of the south china coastline is not clear but may relate to the himalayan collision zone or any other large scale phenomena

radiolytic h2 in continental crust nuclear power for deep subsurface microbial communities 1 h2 is probably the most important substrate for terrestrial subsurface lithoautotrophic microbial communities abiotic h2 generation is an essential component of subsurface ecosystems truly independent of surface photosynthesis here we report that h2 concentrations in fracture water collected from deep siliclastic and volcanic rock units in the witwatersrand basin south africa ranged up to two molar a value far greater than observed in shallow aquifers or marine sediments the high h2 concentrations are consistent with that predicted by radiolytic dissociation of h2o during radioactive decay of u th and k in the host rock and the observed he concentrations none of the other known h2 generating mechanisms can account for such high h2 abundance either because of the positive free energy imposed by the high h2 concentration or ph or because of the absence of required mineral phases the radiolytic h2 is consumed by methanogens and abiotic hydrocarbon synthesis our calculations indicate that radiolytic h2 production is a ubiquitous and virtually limitless source of energy for deep crustal chemolithoautotrophic ecosystems

holocene uplift and subsidence along an active tectonic margin southwestern taiwan abstract taiwan is located along a convergent plate boundary where the luzon arc collides with the eurasia continental margin the tainan plain of southwestern taiwan is incorporated into and deformed by a regional fold and thrust belt associated with this convergent plate margin in this study we establish a tentative regional holocene relative sea level curve that allows us to analyze crustal uplift and subsidence rates of the tainan plain the maximum holocene uplift rates on the tainan plain occur on the tainan tableland and the chungchou terrace these two areas have experienced long term holocene uplift rates of 5 and 7 mm yr respectively the tawan lowland located between these two areas is subsiding at a long term rate of about 1 mm yr based on this pattern of the crustal movement the tainan tableland is interpreted as a mud diapiric dome and the chungchou terrace as the product of a blind thrust fault the holocene reference sea level curve proposed in this study can be used to determine the pattern of crustal movements elsewhere in taiwan it also can suggest that the holocene terrace development does not occur in area where the uplift rate exceeds 8 mm yr while late holocene regression the general trend around the western pacific is not recorded where the rate of subsidence is lower than 1 mm yr

new insights on the relative contributions of coastal processes and tectonics to shore platform development following the kaikōura earthquake we describe the immediate impact of the 14 november 2016 kaikoura magnitude 7 8 mw earthquake on shore platforms and cliffs around kaikoura peninsula the earthquake caused an instantaneous uplift of 1 01 m of the peninsula we resurveyed 7 profiles previously used for erosion monitoring and observed changes in the configuration of the shoreline the coseismic uplift has fundamentally changed the process regime operating on the platforms and altered the future trajectory of shore platform and cliff development our observations highlight the interplay of waves weathering biology and tectonics at this location tectonism strongly modulates the process regime driving instantaneous changes in morphology and altering rates and patterns of erosion finally the uplift of the kaikoura coast has implications for changing resilience to climate change and sea level rise

application of multivariate statistical techniques in alongshore differentiation of coastal barriers abstract this paper investigates the existence of statistical correlations and relationships between geological and oceanographic parameters along a coastal barrier system in southern brazil the existence of few statistical studies on coastal barriers motivated the use of multivariate statistical techniques that take environmental parameters such as coastal morphological sedimentary features and their morphometric measurements into account the hierarchical cluster analysis hca and principal component analysis pca were used to assess the spatial variations of fourteen parameters driving the current and past behavior of this coastal barrier system at fourteen locations through the application of hca these locations were divided into four groups groups 1 2 3 and 4 the hca results were analyzed using pca the first pc1 and the second pc2 principal components together explained at least 76 4 of the variability of all four groups the most important geological and oceanographic parameters that were correlated to pc1 and pc2 were different in each group in general the shoreface slope and shoreface dimensions were common to all groups as pc1 correlated parameters being the most important ones regarding data variability in addition for the progradational groups 1 and 4 retrogradational group 2 and aggradational barriers group 3 pca indicated that shoreline orientation wave exposure and beach type are secondary but relevant factors controlling the past and current behavior of coastal barriers in southern brazil

a nexus of plate interaction vertical deformation of holocene wave built terraces on the kamchatsky peninsula kamchatka russia kamchatsky peninsula lies within a complex meeting place of tectonic plates in particular the orthogonal interaction of the west moving komandorsky island block with mainland kamchatka examining the holocene history of vertical deformation of marine wave built terraces along the peninsular coast we differentiated tectonic blocks undergoing uplift and tilting separated by zones of stable or subsided shorelines we analyzed 200 excavations along 30 coastal profiles and quantified vertical deformation on single profiles as well as along the coast using paleoshorelines dated with marker tephras for the past 2000 yr the average rates of vertical deformation range from about 1 to 7 mm yr uplift patterns are similar to those detected from historical leveling and from mapping of the stage 5e quaternary marine terrace ca 120 ka average vertical deformation in the holocene is highest for the shortest studied time period from ca a d 250 to 600 and it is several times faster than rates for marine oxygen isotope stage mis 5e terraces vertical displacements observed along the coast are most likely coseismic and probably have included subsidence as well as uplift events because subsidence is generally associated with erosion almost surely more prehistoric large earthquakes occurred than are recorded as topographic steps in these terraces we suggest that the distribution of coastal uplift and subsidence observed along the kamchatsky peninsula coastline is qualitatively explained by the squeezing of the kamchatsky peninsula block between the bering and okhotsk plates and the komandorsky island block

geochemistry of archean metavolcanic rocks from kadiri schist belt andhra pradesh india abstract the basic volcanic group exposed in the kadiri schist belt includes high mg basalt basalt basaltic andestite and dacite the basalts are tholeiitic in composition and high mg basalts basaltic andesites and dacites show calc alkaline affinity major and trace element characteristics suggest that the volcanic suite has been derived from an initial tholeiitic magma which has given rise to an early basaltic type and a later calc alkaline type of rocks an island arc and active continental margin tectonic setting was inferred for these rocks

structural and geochronological constraints on the evolution of the bou azzer neoproterozoic ophiolite anti atlas morocco abstract the bou azzer ophiolite in the moroccan anti atlas represents the suture of the neoproterozoic pan african orogen the bou azzer inlier includes from ne to sw three main geological units a volcanic arc an ophiolite and a continental platform several subduction related plutons intrude the ophiolite and the volcanic arc and syn to late orogenic deposits unconformably cover the three terranes the eburnean 2 ga continental basement observed in other inliers of the anti atlas appears not to crop out at bou azzer where rocks traditionally attributed to that old basement are in fact neoproterozoic rocks either metagranitoids of the continental margin or ophiolitic metagabbros the age of a metagabbro of the ophiolite is reported here for the first time as 697 8 ma shrimp u pb on zircons u pb geochronological data are also presented for two syn kinematic subduction related plutons which together with previous data establish a time span of ca 655 635 ma for these arc type rocks moreover the oumlill granite previously attributed to the eburnean basement has been dated as 741 9 ma the earliest tectonometamorphic event affecting the ophiolite is recorded as a relic foliation and a garnet rutile metamorphic assemblage which might attest to an early peak pressure exceeding the 5 6 kbar medium pressure reported so far thus we suggest a first stage of ophiolite underthrusting below a volcanic arc followed by ophiolite exhumation and the concomitant development of the main low grade planar linear tectonic fabric the ages of the calc alkaline syn kinematic subduction related plutons 655 635 ma might be taken as the end of subduction and the beginning of the ophiolite exhumation obduction the author s work in the bou azzer region supports the ophiolite continental platform interpretation of leblanc 1975 and leblanc and moussine pouchkine 1994 rather than the tectonic melange interpretation proposed by saquaque et al 1989b and others a recumbent anticlinal and the basal thrust of the ophiolitic terrane are the main macrostructures formed during the obduction stage characterized by top to the w sw kinematics this deformational event is also recorded in the rocks of the underlying continental platform a syn orogenic unit namely the tiddiline formation unconformably overlies the arc volcanics the ophiolite and the continental platform further collisional deformation affected the tiddiline sediments giving way to ese wsw striking upright folds and oblique reverse faults the latest structures in this neoproterozoic suture were left lateral strike slip faults pointing to an increase in the left lateral component of the continental collision

sea level changes in the last several thousand years penghu islands taiwan strait abstract holocene shore face and beach face deposits form plains 14 c ages of detrital mollusk shells and coral in such deposits at the penghu islands twelve carbonate samples mainly from the largest island makung were dated age measurements for two coral samples and one mollusk sample from the same outcrop imply that the 14 c ages of mollusk shells give the best approximation of depositional age the highest holocene relative sea level in the penghu islands occurred about 4700 years ago with a height about 2 4 m above the present sea level thereafter relative sea level appreciably fell without detectable fluctuations to its recent position our sea level data are consistent with other studies from the central and western pacific except for the timing of peak sea level position this variation may reflect local crustal response to hydroisostatic effects on the continental shelf

geochemistry of the archean yellowknife supergroup the archean yellowknife supergroup slave structural province canada is composed of a thick sequence of supracrustal rocks which differs from most archean greenstone belts in that it contains a large proportion 80 of sedimentary rocks felsic volcanics of the banting formation are characterized by hree depletion without eu anomalies indicating an origin by small degrees of partial melting of a mafic source with minor garnet in the residua granitic rocks include synkinematic granites hree depleted low 87sr86sr i post kinematic granites negative eu anomalies high 87sr86sr i and granitic gneisses with ree patterns similar to the post kinematic granites sedimentary rocks turbidites of the burwash and walsh formations have similar chemical compositions and were derived from 20 mafic intermediate volcanics 55 felsic volcanics and 25 granitic rocks jackson lake formation lithic wackes can be divided into two groups with group a derived from 50 mafic intermediate volcanics and 50 felsic volcanics and group b characterized by hree depletion derived almost exclusively from felsic volcanics ree patterns of yellowknife sedimentary rocks are similar to other archean sedimentary ree patterns although they have higher lanybn these patterns differ significantly from typical post archean sedimentary ree patterns supporting the idea that archean exposed crust had a different composition than the present day exposed crust

geochemistry petrogenesis and tectonic setting of metavolcanics and their implications for gold mineralisation in gadag gold field southern india gold bearing metavolcanics of gadag gold field ggf are represented by mafic metabasalt metabasaltic andesite intermediate metaandesite and felsic metadacite metarhyolite rocks mafic metavolcanic rocks are low k fe rich tholeiites and were derived by partial melting of the upper mantle sources with high fe mg ratios and low m values intermediate and felsic metavolcanics were formed by remelting of these tholeiites mainly in crustal regimes although a complete sequence of metavolcanic rocks from mafic to intermediate to felsic fractions occurs these products were not the result of differentiation from a single magma crustal contamination was involved in the formation of intermediate and felsic rocks a clear gap in the chemical composition as well as index of differentiation among the mafic intermediate and felsic fractions indicate that these metavolcanics constitute a typical bimodal character it is suggested that these metavolcanics were emplaced in an active continental margin or a continental island arc setting the petrogenetic processes of formation of fe rich tholeiites that evolved in an active continental margin or a continental island arc setting could have provided a favourable geochemical environment for gold mineralisation under the conditions of deformation and metamorphism

active deformation of tainan tableland of southwestern taiwan based on geodetic measurements and sar interferometry the d insar technique is applied to detect the active fault related folding structure of the tainan tableland near the deformation front in sw taiwan by using ers sar images during 1996 2000 the tainan tableland is located in between a blind fault in the west and the houchiali fault in the east thus the tainan tableland is interpreted as a pop up structure in a fold thrust belt at active tectonic margin interferometric processing of six sar images reveals the average slant range deformation srd as 12 5 mm yr the uplift rate is higher in eastern tainan tableland than that in western tainan tableland and it increases from west edge of tainan tableland and decreases across the houchiali fault the campaign mode gps data set from 1999 to 2003 indicate an average horizontal movement of 12 4 mm yr in the direction of n44 w for the tainan tableland with respect to western coastline furthermore 5 precise leveling surveys across tainan tableland over a period of 2 years show an uplift rate of 14 mm yr for the benchmarks on the tableland based on the 2 d analytical solution with the constraint of he inferred fault geometry the slip rate along the inferred tainan fault is 16 mm yr 10 mm yr along the houchiali fault and 25 mm yr along the inferred chungchou fault consequently we propose that active deformation of the tainan tableland is likely resulted from the freely slipping of the tainan fault and the houchiali fault the locking depth should be located on the deeper part of decollement eastern of the chungchou fault in addition the combination of d insar gps data and the precise leveling data reveals that the short term deformation rate is larger than long term deformation rate which implies that a destructive seismic event could occur in the eastern tainan area

integration of underground mapping petrology and high resolution microseismicity analysis to characterise weak geotechnical zones in deep south african gold mines abstract a highly stressed shaft pillar is prone to large seismic events falls of ground and rockbursts which may cause injuries and loss of production especially in weak geotechnical zones it is thus important to identify weak geotechnical zones in order to mitigate risks in this study we present integrated studies underground mapping petrology rock mechanics and high resolution microseismicity analysis to understand the different geotechnical zones in the shaft pillar of cooke 4 mine in south africa the footwall of the remnant shaft pillar comprises the upper elsburg reef of the mondeor formation while the ventersdorp contact reef vcr of the venterspost formation and soft weak lavas of the westonaria formation form the hangingwall results from underground mapping and microscopic analysis show that the shaft pillar is composed of quartzites pebbly quartzites argillaceous quartzites and conglomerates underground mapping further shows that the shaft pillar is characterized by several discontinuities which vary from minor to macro scale fractures laboratory uniaxial compressive strength ucs tests indicate that quartzite has the strongest strength followed by pebbly quartzite argillaceous quartzite and lastly conglomerate analysis of high resolution acoustic emissions aes clusters indicates that the majority of aes are associated with the mining stope faces the clusters show the formation of ortlepp shears ahead of the stope which is caused by the excavation induced stress field microseismic data further reveal that the fracture turning point occurs in the soft strata weak hangingwall lavas the integration of these datasets has allowed us to develop the fracture model for different geotechnical zones which concurs with previous models developed for the similar underground environment i e weak soft lava hangingwall and quartzite conglomerate footwall this has major implications for future mining support production and safety

relicts of mud diapirism of the emerged wedge top as an indicator of gas hydrates destabilization in the manila accretionary prism in southern taiwan hengchun peninsula abstract due to oblique collision of the luzon volcanic arc and eurasian passive margin in taiwan we observe southward progression of mountain building processes consequently the southernmost tip of taiwan represents the most recently emerged part of the orogen the hengchun peninsula the area shows evidence of a trench slope basin that emerged in the holocene with landforms that bear submarine characteristics in the late pleistocene lagoonal sediments blanket the basin however the deeper deposits maanshan formation can be found on the surface in several areas we document that the maanshan formation was brought to the surface through upwelling structures mud diapirs as a consequence of fast and overpressured sedimentation from the emerging orogen although fast erosional processes continuously reorganize the new landscape we are able to capture relicts of fast eroding inactive mud volcanoes these unique features are preserved on the surface due to shielding by coral terraces during the shallowing and the lagoonal period of the basin stable carbon 13c and oxygen 18o isotope analysis performed on samples of carbonate blocks of cold vents collected on the outcrops of the maanshan formation confirm classic seep carbonates origins we also identify a mud core anticline below the study area acting as the main source for the mud volcanoes and a possible cause of the uplift of the trench slope basin two multichannel seismic profiles from marine surveys along with a synthesis of several previous surveys helped construct a model of the characteristics of mud diapirism in southeastern offshore taiwan

new evidence for episodic post glacial sea level rise central great barrier reef australia abstract we present an extensive database of 364 radiocarbon dates from coastal and marine sediments of the central great barrier reef gbr shelf of which 110 are previously unpublished the elevation data have been reduced to a common datum australian height datum ahd and the various sources of error have been assessed using modern lithological and biological relationships with sea level the elements of the radiocarbon database have been converted into sea level indicators the upper bound of the assembled dataset corresponds to a best estimate sea level curve and the full dataset provides a narrow envelope for sea level rise on the gbr shelf for the last 11 12 kyr not including hydro isostatic crustal flexing the envelope is consistent with episodic rise in post glacial sea levels the rising post glacial sea level probably included stillstands or minor falls at ca 45 m ahd at ca 10 5 kyr b p 5 m 7 8 kyr b p 2 m ca 6 kyr b p and 1 7 m 5 5 kyr b p there is evidence for a significant fall in sea level between stillstands at 11 m 8 5 kyr b p and 17 m 8 2 kyr b p stillstand durations apparently ranged between the vertical spread in the derived sea level data is very wide the use of shell material for dating seems unreliable and prone to large and unpredictable errors data from bulk mangrove muds appear reliable for determination of ancient sea level but may at times result in sea level being placed up to 4 m below the true level in situ biogenic carbonates such as preserved oyster beds and coral micro atolls are the most reliable indicators of sea level position while deposits of mangrove mud give a useful first order approximation of ancient sea levels caution should be used in drawing sea level curves from few data points we conclude that the post 11 12 kyr b p relative rise in sea level was episodic on the central gbr continental margin more data are required to define clearly sea level change up to ca 20 m at 9 kyr b p

metacraton nature genesis and behavior article i nfo in this paper we show with examples that cratons involved in intercontinental collisions in a lower plate position are often affected by orogenic events leading to the transformation of their margins in some cases craton interiors can also be shaped by intense collisional processes leading to the generation of intra cratonic orogenic belts we propose to call these events metacratonization and the resulting lithospheric tract metacraton metacratons can appear similar to typical orogenic belts i e active margin transformed by collisional processes but are actually sharply different their main distinctive characteristics not all are present in each metacraton are 1 absence of pre collisional events 2 absence of lithospheric thickening high pressure metamorphism being generated by subduction leading to high gradient in strain and meta morphic intensity 3 preservation of allochthonous pre collisional oceanic terranes 4 abundant post collisional magmatism associated with shear zones but not with lithospheric thickening 5 presence of high temperature low pressure metamorphism associated with post collisional magmatism 6 intraconti nental orogenic belts unrelated to subduction and oceanic basin closures reactivation of the rigid but fractured metacratonic lithosphere will cause doming asthenospheric volcanism emplacement and mineral izations due to repetitive mineral enrichments this paper provides several geological cases exemplifying these different metacratonic features in scandinavia sahara central africa and elsewhere a special focus is given to the saharan metacraton because it is where the term metacraton originated and it is a vastly ex panded tract of continental crust 5 000 000 km 2

fundamental uniformity in the trace element patterns of the volcanics of the kaapvaal craton from 3000 to 2100 ma evidence for the lithospheric origin of these continental tholeiites

geochemistry of archean shales from the witwatersrand supergroup south africa source area weathering and provenance with a few exceptions shales from the archean witwatersrand supergroup 2800 ma in south africa are depleted in na ca lile ree and hfse compared to phanerozoic shales cr co and ni are enriched in all witwatersrand shales and fe and mg are high in shales from the west rand groups wrg and lower central rand group crg shales from the crg and uppermost wrg are enriched in na al lile ree hfse and transition metals relative to shales from the lower wrg chondrite normalized ree patterns for all witwatersrand shales are enriched in light ree and exhibit small to moderate negative eu anomalies a positive correlation of ree and al2o3 contents in the shales suggests that ree are contained principally in clay minerals relative to shales from the crg shales from the wrg exhibit depletions of na ca and sr a feature probably reflecting intense chemical weathering of their source rocks cia indices in witwatersrand shales are variable chiefly 70 98 even within the same shale unit such variations reflect chiefly variable climatic zones or rates of tectonic uplift in source areas with perhaps some contribution from provenance and element remobilization during metamorphism compared to present day upper continental crust all but the orange grove roodepoort and k8 shales appear to have been derived from continental sources depleted in lile ree and hfse and enriched in transition metals computer mixing models based on six relatively immobile elements th hf yb la sc co and four source rocks indicate that the relative proportions of granite basalt and komatiite increased with time in sediment source areas at the expense of tonalite the contributions of basalt and komatiite appear to reach a maximum during deposition of the booysens shale and granite during deposition of the k8 shales and possibly during deposition of the orange grove shales

uplift of tainan tableland sw taiwan revealed by sar interferometry interferometric processing of five sar ers images reveals uplift of the tainan tableland sw of taiwan during the period 1996 1998 the maximum measured ground motion for these two years is 2 8 cm along the radar line of sight towards the satellite indicating for the displacement vector a vertical component of 3 2 cm and a horizontal component of 1 6 cm towards the wsw considering additional information from gps data the reconstructed displacement field is consistent with the geological interpretation of the tainan tableland as an actively growing anticline connected to the taiwan fold and thrust belt this implies that the deformation front is located farther west than usually assumed in the tainan area the large tainan city is thus located in an active deformation zone seismic hazard assessment is however difficult because the mechanisms and kinematics are not known in detail

fifteen years of surface deformation in western taiwan insight from sar interferometry abstract geodetically measured surface displacements are produced by a combination of underlying deformation processes acting at different spatial and temporal scales a complete history of surface measurements in an area can help discriminate contributions from tectonic hydrologic and anthropogenic processes in this study we use synthetic aperture radar sar images of the active mountain front and adjacent coastal plain of southwestern taiwan to generate time series of surface deformation from 1995 to 2001 and from 2005 to 2008 based on the insar small baseline method the insar measurements agree well with los motions estimated from continuous gps measurements of 3d displacements between 2006 and 2008 a significant range increase in line of sight los is dominated by land subsidence in the coastal area of western and southwestern taiwan subsidence rates vary with annual periods and are highly correlated with seasonal precipitation which are likely associated with groundwater recharge and withdrawal the long term deformation is dominated by long term tectonic loading in sw taiwan during the interseismic period of the earthquake cycle including elastic strain along or continuous creep on the active faults our results show the ability of insar to reveal spatiotemporal crustal deformation in western taiwan with high spatial resolution and accuracy which is potentially important for evaluating seismic hazards

modern vertical deformation rates and mountain building in taiwan from precise leveling and continuous gps observations 2000 2008 1 to characterize the present day vertical displacement field in the active taiwan orogenic belt 1843 precise leveling and 199 continuous gps measurements from 2000 to 2008 are collected and analyzed in this study vertical velocities derived from the leveling data are placed in a reference frame of the chinese continental margin using continuous gps observations at nearby sites the leveling and gps vertical velocities generally reveal a dome shaped pattern with uplift of 0 2 18 5 mm yr in the interior of the mountain range and subsidence on the flanks of the mountains and coastal plains modern uplift rates in the active fold and thrust belt are generally consistent with geologic uplift rates however present day uplift rates in the central range are faster than the million years averaged exhumation rates the modern subsidence rates are generally consistent with geologic rates except for the rates in western coastal areas due to groundwater pumping present day subsidence in the southern central range and northern coastal range is however inconsistent with long term uplift which may reflect interseismic elastic strain accumulation across faults present day subsidence in northern taiwan occurs in a region of postcollisional orogenic collapse we model the present day and geologic vertical velocities and published gps horizontal velocity data across southern taiwan using a 2 d lithospheric model the model suggests a combined slip rate of 40 mm yr on the frontal thrusts and 45 mm yr on the longitudinal valley fault the model requires an additional source of crustal thickening under the central range to match the observed present day uplift rates

geochemistry and petrogenesis of early proterozoic intracratonic volcanic rocks of the ventersdorp supergroup south africa abstract the 2 5 ga old predominantly volcanic rocks of the ventersdorp supergroup represent a cratonic cover sequence within the kaapvaal craton of southern africa they are underlain by the rocks of the witwatersrand supergroup and are overlain by sediments of the transvaal supergroup the sequence consists of six formations and is more than 3700 m thick it comprises basaltic andesitic dacitic and rhyolitic lavas with agglomeratic intercalations as well as subgreywacke conglomerate local stromatolitic limestone and shale petrographic investigations and the determination of major and trace elements were carried out on 45 samples of volcanic rocks from nine boreholes originating from the klerksdorp area the orange free state and the east rand the primary mineralogy of the mafic to intermediate volcanics consisted of clinopyroxene plagioclase and quartz but has been extensively altered during low temperature metamorphism with hornblende actinolite tremolite serpentinite epidote calcite chlorite sericite clinozoisite titanite and sphene occurring as secondary minerals the analyzed rock types consist of basalts basaltic andesites and andesites as well as felsic lavas two samples of ultramafic cumulate volcanic rock and two vitric tuffs were also investigated in spite of considerable alteration the preserved mineralogy and inter element correlations indicate that the basalts basaltic andesites and andesites are cogenetic the ultramafic and felsic rocks are probably also cogenetic but more geochemical data are required to demonstrate this relationship the systematic variations of ti y and nb vs zr throughout the volcanic succession suggest a crystal fractionation sequence involving ol pl cpx mt opx major and trace element data show that magnetite crystallized during the later stages of differentiation discrimination diagrams to infer the tectonic setting produce equivocal results and seem to have only limited validity for these early proterozoic rocks the geotectonic setting of the ventersdorp supergroup suggests a basin development whose further evolution into a proper continental rift system was aborted during the phase of basin subsidence chemical similarities with archaean greenstone belt volcanic assemblages suggest that the ventersdorp rocks reflect the evolution of an abortive greenstone belt on thick continental crust

tectonic evolution of the rehamna metamorphic dome morocco in the context of the alleghanian variscan orogeny structural and 40ar 39ar geochronological investigations of the rehamna massif meseta moroccan variscan belt provide new constraints on the tectonic evolution of the alleghanian variscan orogen during the upper paleozoic three main tectonic events have been recognized 1 southward thrusting of an ordovician sequence over the proterozoic basement its cambrian sedimentary cover and the overlying devono carboniferous basin this event caused subhorizontal shearing and prograde barrovian metamorphism of the buried rocks 2 continuous shortening resulting in the development of a synconvergent extrusion of metamorphosed units to form a dome elongated e w this was responsible for synconvergent detachment of the ordovician upper crustal sequence the timing of these two episodes is constrained to 310 295 ma by cooling and metamorphic amphibole and mica ages 3 a nw wnw convergence in a direction orthogonal to the previous one and characterized by the accretion of the rehamna dome to the continental basement in the east based on 40ar 39ar cooling ages from a syntectonic granitoid and its host rocks and metamorphic 40ar 39ar ages from greenschist facies mylonite the timing of this event falls between 295 and 280 ma the end of the variscan orogeny in the moroccan meseta is constrained by the 40ar 39ar cooling age of a posttectonic pluton dated at 275 ma the tectonic events highlighted in morocco coincide with the late variscan alleghanian tectonic evolution of southern europe and north america and can be correlated with the global reorganization of plates that accompanied suturing of pangaea at around 295 ma

holocene coseismic and aseismic uplift of isla mocha south central chile abstract during the past 6000 years isla mocha a 12 km long island 30 km off the coast of south central chile experienced a 38 m fall of relative sea level caused primarily by rapid tectonic uplift of the island as many as 18 raised shorelines strandlines record this uplift historic accounts of uplift during the great earthquakes m 8 of 1835 and 1960 suggest some of the more prominent prehistoric strandlines also emerged during great earthquakes on the interface between the nazca and south america plates but the close elevational spacing of strandlines subdued morphology of strandline beaches scarcity of exposed bedrock wave cut platforms and the extremely high rates of aseismic uplift ca 70 mm yr of the island since the last great earthquake suggest that many strandlines were raised by aseismic rather than coseismic uplift strandline heights and 14 new radiocarbon ages on marine shells show that the present day uplift rate is more than three times the net rate ca 20 mm yr of the past 1000 years the recent high rate probably reflects increased aseismic slip on an inferred thrust fault in the overriding south america plate isla mocha overlies an area of high stress concentration between two major segments of the chilean subduction zone the inferred high rate of slip on the thrust fault may be a response to stress changes on the plate interface near the boundary between the segments

middle late holocene river terraces in the erhjen river basin southwestern taiwan implications of river response to climate change and active tectonic uplift abstract we reconstruct the holocene river history of the erhjen river area 140 km 2 by correlating river terraces aided by 28 radiocarbon dates multiple terraces developed in the lower erhjen river since the middle holocene they converge downstream to the coastal plain the rates of channel incision into bedrock calculated from these terraces at yuehshihchieh are 7 8 mm year during ca 5 7 2 5 ka 5 cm year during 1 5 1 3 ka and 1 cm year since 1 ka the last is close to the average incision rate since middle holocene meanwhile only a single but wide middle late holocene paleo floodplain was developed in the upper erhjen river it was completely abandoned only after 0 8 ka likely following an episode of base level fall starting from the coastal plain based on the apparent downstream and upstream convergence of these dated terraces we identify a doming structure or anticline within the basin which results in a tilt rate of 10 6 to 10 7 per year in the lower erhjen river valley the major terraces here had different initial long profiles which implies that a critical graded long profile may not be a prerequisite for formation of a wide erosional terrace surface instead we propose that these terraces were initiated by a series of catastrophic rainfall events probably climatic related which brought a large amount of bedload from hillslopes to prevent the channel from incising when valley widening was facilitated by high discharge runoff we find that not only terrace surface formation but also channel incision can be strongly controlled by climatic driven discharge and bedload conditions as suggested by the contrast of bedrock incision rates we observe at yuehshihchieh apparently the climate and its effects on the landscape cannot be regarded as constant during the holocene even in a humid tropical area like taiwan however such a fluctuation of climate could only be recorded in a setting where rivers have a high tendency to incise so that multiple terraces can be created the lower erhjen river that is characterized by active tectonic tilting is an example of this setting

millennial slip rate of the longitudinal valley fault from river terraces implications for convergence across the active suture of eastern taiwan the longitudinal valley fault is a key element in the active tectonics of taiwan it is the principal structure accommodating convergence across one of the two active sutures of the taiwan orogeny to understand more precisely its role in the suturing process we analyzed fluvial terraces along the hsiukuluan river which cuts across the coastal range in eastern taiwan in the fault s hanging wall block this allowed us to determine both its subsurface geometry and its long term slip rate the uplift pattern of the terraces is consistent with a fault bend fold model our analysis yields a listric geometry with dips decreasing downdip from about 50 to about 30 in the shallowest 2 5 km the holocene rate of dip slip of the fault is about 22 7 mm yr this rate is less than the 40 mm yr rate of shortening across the longitudinal valley derived from gps measurements the discrepancy may reflect an actual difference in millennial and decadal rates of convergence an alternative explanation is that the discrepancy is accommodated by a combination of slip on the central range fault and subsidence of the longitudinal valley floor the shallow listric geometry of the longitudinal valley fault at the hsiukuluan river valley differs markedly from the deep listric geometry illuminated by earthquake hypocenters near chihshang 45 km to the south we hypothesize that this fundamental along strike difference in geometry of the fault is a manifestation of the northward maturation of the suturing of the luzon volcanic arc to the central range continental sliver

forearc uplift rates deduced from sediment cores of two coastal lakes in south central chile abstract the present paper introduces a new approach for deriving information about local forearc tectonics and related uplift rates based on the study of lake sediments we investigated two coastal lakes at the south central chile margin lakes lanalhue and lleu lleu located south of the arauco peninsula 38 s both lakes developed within the valleys of ancient rivers that once drained to the pacific ocean being subsequently dammed by rising sills in the late pleistocene early holocene seismic profiling and sedimentological analyses of cores from both lakes revealed similar successions consisting of marine to brackish sediments covered by lacustrine deposits radiocarbon dating indicates that the marine lacustrine transition occurred at 8 ka and 8 15 ka respectively the correlation of this transition with global sea level curves allowed the calculation of local uplift rates for the holocene uplift rates for the lake basins amount to 0 42 0 71 and 0 49 0 44 mm a respectively which are consistent with rates determined from a late pleistocene marine terrace in the area however conspicuously higher though likely transient vertical movements at 8 83 2 7 mm a and 11 36 1 77 mm a respectively were calculated for the sills that block both lakes nowadays these barriers are interpreted to be the surface expression of a blind reverse fault associated to the morguilla fault system a seismically active structure that controls uplift and folding along the adjacent arauco peninsula

holocene sea level highstand and its implications for the vertical stability of panglao island southwest bohol philippines abstract emerged tidal notches in panglao island southwest bohol central philippines were used to investigate relative sea level changes during the holocene the elevation and profile of a laterally continuous notch were surveyed at 22 sites around panglao island the tidal notch documents higher than present mean sea level pmsl consistent with regional field observations and predictions for mid holocene time the reconstructed paleo shoreline elevations range from 0 to 1 6 m above pmsl exhibiting a general increase to the northeast the more protected part of the coast this lateral variation in the holocene paleo mean sea level msl along with changes in notch depth and profile suggests tilting of the island best explained by differential land movement last interglacial msl estimates by previous workers also show tilting to the southwest moreover the holocene notch data suggest segmentation of the island into several blocks that tilt consistently to the southwest suggesting the presence of faults lineations in aerial photographs trending northeast southwest confirm the presence of these faults these data indicate differential land movements during the holocene and late pleistocene calculated rates of uplift are 0 3 and 0 06 mm yr for the holocene and for the late pleistocene respectively these values relative to the high uplift rates from tectonically active regions imply that panglao is relatively vertically stable after accounting for tectonic tilting mid holocene sea level is estimated at approximately 0 3 0 6 m

a growing structure near the deformation front in sw taiwan as deduced from sar interferometry and geodetic observation 1 we apply the d insar technique to monitor the active growing structure on the tainan tableland near the deformation front in sw taiwan using ers sar images in the period of 1996 2000 interferometric processing of six sar images reveals the average slant range displacement srd to be 12 5 mm yr and it increases from the west edge of the tainan tableland and decreases across the houchiali fault the gps campaign data indicate an average horizontal movement of 12 4 mm yr in the direction of n44 w for the tainan tableland with respect to the western coastline five precise leveling surveys across the tainan tableland over two years show an uplift rate of 14 mm yr for the benchmarks on the tableland by combining the horizontal velocity of gps data and the srd of d insar we transfer the srd into vertical deformation and discuss the deformation pattern and seismic hazards in the tainan area

the chiuhsiungken fault a candidate to trigger a hazardous earthquake in western taiwan abstract the chiuhsiungken fault located along the boundary between the western foothills fold and thrust belt and the coastal plain in the chiayi yunlin area of taiwan has been identified as an active thrust through geological and geomorphic investigations young geomorphic features provided by shortening across the chiuhsiungken fault are well preserved and provide excellent examples to illustrate features provided by active thrust faulting historic seismicity records show that the deformation front in the chiayi yunlin area is very active and the fault slips at a rate of mm yr based on tectonic geomorphic investigation the chiuhsiungken fault has the potential to produce large earthquakes in the future the fault with a length about 15 km can be traced northward to the sinistral kuken transfer fault and southward to near the sinistral chuchi transfer fault the maximum potential magnitude of an earthquake triggered by the chiuhsiungken fault is estimated to be a m w 6 4 however the magnitude of the earthquake could be larger than expected if the adjacent faults rupture together with the chiuhsiungken fault

the cambrian volcano sedimentary formations of the westernmost high atlas morocco their place in the geodynamic evolution of the west african palaeo gondwana northern margin abstract in the westernmost part of the high atlas two palaeozoic formations rich in mafic volcanic rocks are distinguished they belong to different structural blocks created during the variscan orogeny new u pb dating yields an early cambrian age the basaltic lavas have the composition of continental tholeiites and the magmatic signature of an initial rifting tectonic setting they are related to the western moroccan cambrian rift their geodynamical context could be a passive margin initiated from an active rift that aborted in the middle cambrian

fault activity and lateral extrusion inferred from velocity field revealed by gps measurements in the pingtung area of southwestern taiwan abstract four campaigns of dense gps measurements have been conducted since 1995 to investigate crustal deformation patterns in sw taiwan the station velocities decrease westwards from 42 2 to 55 5 mm yr along the azimuths from 247 1 to 272 5 in central part of the study area gps stations move nearly toward the west whereas in the pingtung kaohsiung coastal area displacement vectors demonstrate a clear counter clockwise deviation toward the sw the transtensional deformation and the along strike variation of southward increase of extensional deformation is due to the low lateral confining conditions related to the manila subduction zone as a free boundary or and the presence of the prominent peikang high as a rigid indentor the chishan fault is dominated by right lateral motion with a fault slip rate 7 mm yr in a n50 w direction the kaoping fault is dominated by left lateral motion with a 4 8 mm yr in a n s direction the significant right lateral component of motion of 24 30 mm yr is accommodated along the active structures west of the chishan fault the right lateral and left lateral structures facilitate the southwestward extrusion the velocity gradients of the gps stations across the chaochou fault are not significant this implies that the chaochou fault is locked along the fault plane

holocene sea levels in oceanic islands implications for the rheological structure of the earth s mantle abstract relative sea levels in oceanic islands that are situated sufficiently far from glaciated regions were studied in relation to the rheological structure of the earth s mantle the local hydro isostatic adjustment associated with the mantle flow from the oceanic side to an inland side depends on the size of the island the effective upper mantle viscosity and the elastic plate thickness the relative sea level has a significant dependence on the upper mantle rheology for islands with a radius larger than 10 km but it is almost independent of the upper mantle rheology for islands with a radius less than 10 km in other words the observed sea level changes in such small islands follow the global isostatic adjustment which depends strongly on the lower mantle viscosity in fact the relative sea levels in small oceanic islands impose important constraints on the lower mantle viscosity on the other hand the effective upper mantle viscosity and the elastic plate thickness are determined by analyzing the relative sea levels for islands greater than 10 km the observed sea level curves in japan and new zealand are consistent with the effective viscosity of the upper mantle equal to 2 to 6 10 21 poises the effective elastic plate thickness for japan and new zealand is estimated to be less than 50 km and greater than 100 km respectively the thickness of the lithosphere obtained by sea level curves in japan and new zealand is compatible with the results obtained by seismological studies

tandem suturing and disarticulation of the taiwan orogen revealed by its neotectonic elements taiwan s numerous active faults and folds demarcate distinct eastern and western neotectonic belts the western belt results from the attachment and subsequent detachment of a sliver of continental lithosphere to the eurasian continental margin the eastern belt is the product of the same continental sliver docking with and then separating from the luzon volcanic arc thus the active taiwan orogen is a tandem suturing and tandem disengagement of a volcanic arc and a continental sliver to and from the eurasian continental margin this progressive suturing and separation is a superb living demonstration of the fundamental weakness of lithospheric sutures furthermore this neotectonic architecture provides the basis for understanding the taiwan s seismic sources

holocene coastal uplift in the western pacific rim in the context of late quaternary uplift abstract this paper reviews recent studies of holocene coastal uplift in tectonically active areas near the plate boundaries of the western pacific rim emergent holocene terraces exist along the coast of north island of new zealand the huon peninsula of papua new guinea the japanese islands and taiwan these terraces have several features in common all comprise series of subdivided terraces the highest terrace is a constructional terrace underlain by estuarine or marine deposits and the lower terraces are erosional cutting into transgressive deposits or bedrock the highest terrace records the culmination of holocene sea level rise at ca 6 6 5 ka bp lower terraces were coseismically uplifted repeated major earthquakes have usually occurred at ka intervals and meter scale uplift the maximum uplift rate and number of terraces are surprisingly similar about 4 m ka and seven to four major steps in north island huon peninsula and japan taiwan especially along the east coast of the coastal range is different reaching a maximum uplift rate of 15 m ka with 10 subdivided steps they record a very rapid uplift comparison between short term holocene and long term since the last interglacial maximum sub stage 5e uplift rates demonstrates that a steady uplift rate huon peninsula or accelerated uplift toward the present several areas of japan and north island has continued at least since isotope sub stage 5e rapid uplift in eastern taiwan probably started only in the early holocene judging from the absence of any older marine terraces most of the causative faults for the coastal uplift may be offshore reverse faults branched from the main plate boundary fault but some of them are onshore faults which deformed progressively with time

late quaternary activity of the feldbiss fault zone roer valley rift system the netherlands based on displaced fluvial terrace fragments abstract the meuse river crosses the feldbiss fault zone one of the main border fault zones of the roer valley graben in the southern part of the netherlands uplift of the area south of the feldbiss fault zone forced the meuse river to incise and as a result a flight of terraces was formed faults of the feldbiss fault zone have displaced the middle and late pleistocene terrace deposits in this study an extensive geomorphological survey was carried out to locate the faults of the feldbiss fault zone and to determine the displacement history of terrace deposits the feldbiss fault zone is characterized by an average displacement rate of 0 041 0 047 mm a 1 during the late pleistocene individual faults show an average displacement rate ranging between 0 010 and 0 034 mm a 1 the spatial variation in displacement rates along the individual faults reveals a system of overstepping faults these normal faults developed by reactivation of paleozoic strike slip faults as fault displacements at the bases of the younger terrace deposits are apparently similar to the tops of the adjacent older terrace the age of these horizons is the same within thousands of years this implies that the model of terrace development by rapid fluvial incision followed by slow aggradation does apply for this area

new evidence for the holocene sea level high from the inner shelf central great barrier reef australia radiocarbon dates from fossil oyster beds of intertidal origin on magnetic island north queensland indicate that the local holocene maximum of relative sea level was attained no later than 5660 50 b p conventional uncorrected age and remained at 1 6 1 7 m above modern levels until 4040 50 b p given the tectonic stability of the area this implies that eustatic sea level remained at its holocene peak for at least ca 1600 yr the new high precision sea level data indicate sea levels 1 5 m higher than those of the same age inferred from buried mangrove deposits on the inner shelf in north queensland uncertainties in deriving relative sea level from such mangrove deposits may be a significant source of error in worldwide attempts to distinguish the eustatic and crustal warping components off relative sea level change especially in the tropics

mid holocene sea level highstand along the southeast coast of china various sea level curves have been proposed for the coast of china in the past two decades these sea level curves indicate a complex history of holocene sea level and so the debate on whether or not a higher mid holocene sea level highstand exists in the coast of china has continued this paper aims to re examine the holocene sea level history for the low latitude part of the china coast between 18 n and 32 n by re assessing all the sea level data available from the east to south coasts and separating them according to geological settings in order to examine the influences of global and local factors the reconstructed sea level histories from different coastal sectors of the china coast reveal a certain degree of variability in the timing and height of mid holocene sea level highstand within large river deltas the mid holocene sea level highstand occurred earlier by almost 1000 years than that from other coastal sites the highstand from large river deltas appears also lower in altitude a few metres below the present day sea level due probably to the local factors of subsidence and sediment consolidation in geologically stable coastal sites the highstand is recorded at the same altitude as the present day sea level a 1 2 m higher highstand is found from sites where tectonic uplift is observed

what caused the mysterious eighteenth century tsunami that struck the southwest taiwan coast several different historical records allude to a disastrous tsunami on the southwestern taiwan coast sometime between 1781 and 1782 with a reported death toll of more than 40 000 despite consistent reports from southwest taiwan no corroborative information exists for neighboring shorelines in southeast china or northwest luzon philippines and a plausible source of this tsunami has never been identified neither a large earthquake from the manila trench and active thrust faults nor a submarine volcanic eruption from the northern luzon arc can explain the very localized area affected and the physical phenomena described in the historical records comparing the results of 13 numerical models of tsunamis generated from different sources earthquake volcano and submarine mass failure we therefore suggest that a seismically triggered submarine mass failure on the upper portion of the continental slope offshore from southwestern taiwan is the most likely source of the eighteenth century event

sediment trapping in deltas of small mountainous rivers of southwestern taiwan and its influence on east china sea sedimentation abstract taiwan s setting of high mountains steep gradients frequent earthquakes erodible lithology and heavy rainfall represents an ideal site to focus on sedimentary processes of the deltas of small mountainous rivers smrs several smrs in southwestern taiwan have deposited a thick sedimentary succession in the composite southwest taiwan delta swtd since the middle holocene evidence from the swtd can help to determine its trapping efficiency and assess the role of smrs in sediment transport to the sea we used historical nautical charts bathymetric data satellite radar data and 14c dates to calculate the sediment volume of the swtd on millennial and decadal scales the 14c dates of core samples indicate deposition of thick deltaic sediment in subsiding areas since the time of the maximum flooding surface about 7 cal ka bp the paleo shoreline changes of the swtd suggest a steady westward progradation since 7 cal ka bp in contrast the nautical charts suggest minor volume reduction of the offshore part of the swtd with a deepening trend and retreating shorelines during the last seven decades the results show that at least 201 72 13 90 km3 3 23 105 mt of sediment has been trapped in the swtd since 7 cal ka bp and that the delta has shifted to a destructive phase during the past seven decades as human influences such as construction of reservoirs dams and weirs in the hills have reduced the sediment supply the birth of the taiwan warm current and following continuous sediment supply from the western rivers of taiwan to the east china sea since 7 3 cal ka bp have played a crucial role in the sedimentation of the east china sea particularly in the okinawa trough and the japan sea through the tsushima warm current