a 3 ma paleomagnetic record of coastal continental deposits in argentina abstract continental deposits of upper cenozoic age laid down under alternating depositional environments were subjected to paleomagnetic analyses the sequence was found to cover the last about 3 ma and to include the upper gauss the matuyama and brunhes epochs and the olduvai and jaramillo events the reversals are independent of stratigraphic boundaries the polarity changes are connected with low intensities and susceptibilities the reversals seem to form oblique vgp paths between approximately 90 w and 90 e longitude the magnetostratigraphy established may serve as a local south american magnetostratigraphic standard section

thrust tectonics in the andean retro foreland basin of northern peru permian inheritances and petroleum implications abstract in northern peru the huallaga moyabamba maranon subandean foreland basin system results from the interaction between thin and thick skinned tectonics geophysical data and the construction of two balanced cross sections show that this structural configuration has been controlled by permian inheritances a fossilized west verging middle permian fold and thrust belt which developed during the gondwanide orogeny has been partly reactivated by the andean compression and controlled thick skinned tectonics propagation this west verging thrust system is still active and causes the crustal and damaging seismicity of the moyabamba region late permian salt which has sealed the middle permian fold and thrust belt controlled thin skinned tectonics propagation and the development of the must large overthrust of the peruvian subandean zone the fossilized and partly reactivated middle permian fold and thrust belt constitutes a new petroleum play for the exploration in the northern peruvian subandean basins sub thrust traps of the moyabamba and huallaga wedge top basins are particularly attractive but stay unexplored

paleofloods and ancient fishing weirs in nw iberian rivers a 15 m thick fluvial sedimentary record of the nw iberian lower mino river was studied grain size analyses were performed and twelve samples were dated using optically stimulated luminescence dating techniques documenting a 1300 yr old reconstructed fluvial record that does not match with known climate fluctuations in the area but is linked instead to the construction of a series of ancient fishing weirs pesqueiras the sedimentation phases are in agreement with known episodes of increased population density which suggests active use of the pesqueiras a number of sedimentation hiatuses in the fluvial record point towards damage to the pesqueiras during large scale flooding in the mino river basin and a sudden drop in population probably due to the arrival of the plague in the 13th century ad the oldest sedimentation phases started just after 700 ad and we infer that the first pesqueiras were constructed around this time this timing coincides with the transition of the nw iberian landscape towards a more intensively used agricultural landscape as evidenced from other geo archeological investigations the results demonstrate that the pesqueiras are several hundreds of years older than known from historical records but not so old as to date back to the roman occupation

bouguer gravity map of indonesia abstract a bouguer gravity map of indonesia on mercator projection at a scale of 1 5 000 000 and with a contour interval 20 mgal has been prepared over the past few years as part of a joint research program of the geological survey of indonesia and the university of new england armidale a new base station network was set up throughout indonesia and tied to the igsn stations at sydney and singapore a discussion of the gravity features and the tectonic implications are given the map is obtainable in folded form only from the publications department university of new england armidale n s w australia 2351 for a 5 plus postage

oxygen isotope calibration of the onset of ice rafting and history of glaciation in the north atlantic region we report here that dsdp site 552a cored with the hydraulic piston corer on the west flank of rockall bank recovered an undisturbed sequence of alternating white deep sea carbonate oozes and dark coloured layers that are rich in glacial debris oxygen isotope analysis of the sequence together with detailed nannofossil and palaeomagnetic stratigraphy shows that the first major horizon of ice rafting occurred at about 2 4 myr and was preceded by a minor pulse of ice rafting at about 2 5 myr the carbon isotope record shows that the site has been bathed by a water mass of similar characteristics to present day north atlantic deep water at least since 3 5 myr

the evolution of andesite volcano structures new evidence from gravity studies in costa rica abstract published gravity data on active volcanoes generally reflect either the low density scoriaceous pumiceous deposits that are localized within ring fracture collapse depressions such as the calderas of mature silicic volcanoes or the high density frozen magma conduits that occur beneath basaltic shields and cones the intensive gravity surveys reported here over three complex andesite volcanoes reveal features of both types their multi component gravity fields have crater centred positive anomalies 1 2 km diameter surrounded by broader zones of negative gravity with similar amplitudes but greater width 5 10 km the former are thought to reflect sub crater magma pipes of normal density ca 2 5 2 6 mg m 3 surrounded by pyroclastic scoria ashes and occasional lava flows of much lower net density 1 8 2 4 mg m 3 which in turn account for the negative anomalous zones because the deeper more consolidated and older parts of these andesite volcano edifices have more normal densities 2 3 2 6 mg m 3 the low density materials are particularly interesting because they appear to have filled topographic depressions to depths of several hundred metres especially where old caldera like structures have been postulated from the steep gravity gradients over perimeter ring faults a model is developed whereby short periods of caldera collapse associated with intermittent large high level magma bodies are interspersed by normal crater like activity with narrow sub surface magma pipes dominantly pyroclastic activity from summit craters generates the materials that gradually fill earlier formed topographic depressions this study demonstrates the unique value of detailed gravity surveys combined with surface geological information for modelling and understanding the evolution of active volcano summit regions

the changing geomorphology of the humid tropics abstract it is debatable whether tropical geomorphology is intrinsically different from the geomorphology of other places the traditional geomorphology of the humid tropics had certain expectations with regard to landforms and processes a number of case studies over the last three decades however using new concepts and field and laboratory techniques have changed such expectations this paper primarily examines the research themes of the last ten years or so identifies the major trends and attempts to predict areas where interest is expected to concentrate in near future the following topics among the current research trends are highlighted geochemical erosion movement on tropical slopes rivers in the tropics tropical landforms hydrology and sedimentation in the rainforest denudation efficiency in the humid tropics the quaternary evolution and changes and the applied side of tropical geomorphology clearly the landforms and geomorphological processes in the tropics are dependent only partially on climate but to greater extent on neotectonism lithology episodic and catastrophic events such as tropical cyclones and above all on anthropogenic alterations of the landscape a wide variety of landforms and processes are found in the humid tropics and generalisations are extremely difficult in the next century geomorphological studies in the tropics are likely to develop along certain lines environmental investigations will form a major component along with the study of postulated sea level rise current major research trends will undoubtedly continue but increasingly through a multidisciplinary and multipeople approach large scale investigations involving pantropic correlation of past events such as synchronised large floods will grow use of new research tools such as satellite imagery various dating facilities etc will become common and expected it seems likely that the arrival of so much information will modify mainstream geomorphological and sedimentological theories or will provide these with a tropical version

a gravity and volcanostratigraphic interpretation of the lake toba region north sumatra indonesia abstract in northern and central sumatra a wide distribution of ignimbrite and volcanic sediments is observed some geologists consider that these volcanic products were erupted from lake toba the subduction of the indian ocean plate along the trench of central sumatra started at least as long ago as the late miocene fitch s model 1972 obtained the plate convergence vector 67 mm yr decomposed into its components perpendicular 58 mm yr and parallel 34 mm yr to the trench axis tears seaward of the mountain range created the sumatran fault about 2 ma ago at that time the edge of the plate reached a depth of almost 100 km and a large amount of dacite magma was generated the tuk tuk dacite a kind of ignimbrite was erupted along the sumatran fault and covered a broad area the age of this ignimbrite was obtained as 1 9 0 4 ma k arage and 2 0 0 3 ma fission track age since this eruption the hinterland of this fault has been changed to a tensional field forming a graben structure at the northern end of this graben west of harranggaoul the ignimbrite haranggaoul formation was erupted 1 3 0 3 ma ago forming a caldera the lacustrine sediments of samosir island have a normal magnetization and overlie the tuk tuk dacite unconformably from this we can conclude that the graben structure has been covered with water lake toba at 0 7 0 6 ma ago this tectonic movement has continued so that it is difficult to distinguish the caldera structure on the gravity anomaly map of the northern part of lake toba from the results of the gravity survey it can be concluded that at 0 1 ma ignimbrite flowed down along the asahan river and filled the old river along the lowland between parapat and porsea forming a caldera 30 000 years ago dacite and and esite eruptions have occurred around lake toba forming the volcanic cones

the plio pleistocene record of the central eastern pampas buenos aires province argentina the chapadmalal case study abstract the plio pleistocene record of central eastern pampas argentina is preserved in loess like sediments exposed in the sea cliffs south of mar del plata the uplift of the andes during miocene triggered the deposition of wind blown material the source areas are located about 1000 km away in western argentina volcanic ashfalls play a significant role in the formation of eolian sediments which were reworked and redeposited by aqueous transport in a flat low relief landscape under varying climatic conditions vertebrate fossil assemblages document warm and wetter pliocene and early pleistocene climates during montehermosan and uquian land mammal ages more arid and cooler conditions alternating with humid and warmer intervals prevailed during the middle to late pleistocene in ensenadan and lujanian land mammal ages the chapadmalal locality is the best exposed and most complete section almost all the units have been modified by pedogenesis truncated paleosols as well as pedogenic and non pedogenic calcretes are very frequent throughout the stratigraphic succession several paleosurfaces with prominent paleosols and calcretes suggest that sedimentation was an episodic process with numerous depositional gaps recording relatively long lasting intervals of landscape stability the depositional events represent alternations of fluvial and eolian sedimentation low frequency catastrophic episodes played an important role in the sedimentation process

titan s haze structure in 1999 from spatially resolved narrowband imaging surrounding the 0 94 μm methane window 1 we use narrowband images of titan obtained in november 1999 to explore the haze vertical structure in titan s lower atmosphere the images were taken with the mount wilson 2 54 m telescope using the nasa gsfc built acousto optic imaging spectrometer these images were recorded at five wavelengths surrounding the 0 94 m methane window and are sensitive to a range of altitudes in titan s lower atmosphere we characterize titan s limb darkening by fitting the minnaert function limb darkening coefficient k to our data at 0 latitude and compare our observed limb darkening to that predicted from three radiative transfer models the vertical haze profiles suggest a gap in haze below 75 km with an increase in haze abundance near the surface

mathematical modeling of graded river profiles numerical modeling of the longitudinal profiles of rivers at grade is accomplished using the basic equations of open channel flow sediment transport equations and empirical relations for downstream variation in flow discharge sediment discharge sediment caliber and channel width only in some cases are the computed stream profiles fit exactly by any one of the commonly supported mathematical function analogs to graded profile form exponential logarithmic or power function but in most cases any of these functions can provide a fit with a degree of error smaller than would be noted in treating field data profiles dominated by spatial change in fluid and sediment discharge are distinctly power functions while profiles dominated by sediment size reduction are not necessarily exponential in form other important controls on profile shape are the degree of downstream width change in response to increasing discharge and the general range of sediment size a dynamic model of a river s approach to grade

loess stratigraphy in central china abstract loess sequences in central china provide a detailed record of climate changes during the last 2 5 million years at least 44 major shifts from glacial to interglacial conditions occurred during this time in china prolonged loess deposition lasting more than 40 millennia occurred eleven times with only four of these intervals in brunhes chron the climate oscillations took place with increased frequency between 2 4 and 0 5 ma compared to the last half million years major shifts toward cooler and drier climates occurred at about 2 4 ma 1 2 ma and 0 5 ma while less pronounced shifts are dated to 1 65 ma 0 8 ma and 0 2 ma three of the last four reversals of the earth s magnetic field whose lithostratigraphic position has been detail are recorded in a glacial deposit the low field magnetic susceptibility of loess and soils which reflects the concentration of ultrafine magnetite is related to the degree of pedogenesis and serves as a proxy measure of climate the accumulation rate of the magnetite was fairly constant throughout the last 1 2 million years and can serve as a measure of time susceptibility records from localities near xifeng and luochuan located 160 km apart are compared and used to define informal lithostratigraphic units in the loess plateau of china

optical dating of young coastal dunes on a decadal time scale we explore the use of quartz optically stimulated luminescence osl dating for reconstructing coastal evolution on a time scale of decades to a few hundred years samples are taken from the accretionary south west coast of texel a barrier island just offshore of the northern netherlands the ages of dune ridges are known from historical sources an excellent chronology with a decadal accuracy exists for the past 260 years osl ages of less than 10 years on the youngest samples indicate that the osl signal of the quartz grains is very well zeroed prior to deposition and burial osl ages of five samples from a 250 year old dune ridge are indistinguishable and the osl ages on 17 out of 20 samples are in excellent agreement with the well known independent age controls our results highlight the potential of osl dating for high resolution reconstruction of coastal evolution over the past few centuries

the subsurface structure of the aira caldera and its vicinity in southern kyushu japan abstract southern kyushu japan includes a chain of large and small calderas and active volcanoes and the greatest part of it is covered with thick pyroclastic ejecta the regional and local structures of this area are discussed from the standpoint of physical volcanology with consideration of all available data the regional structure of this area is examined in the light of gravity and geomagnetic anomalies two layers of the earth s uppermost crust are defined by spectrum analysis of the gravity anomalies these two layers are identical with the two identified by seismicwave velocities the bouguer gravity anomalies are relatively high and rather monotonous over outcrops of the mesozoic basement and the granite but are relatively low and perturbed over calderas and caldera like structures two low gravity anomalies in kagoshima bay are remarkable one is circular with its center on the aira caldera the other is elongated between the satsuma and oosumi peninsulas the southern end of the latter anomaly is occupied by the ata caldera discussion of the gravity anomalies of the aira caldera suggests that the subsurface basement has a funnel shape and is overlain by fallback the sub bottom geology of the caldera suggests that it is formed by a few smaller depressions though the distribution of the overall gravity anomalies is parallel with its shape the southern part of kagoshima bay is characterized by a graben like topography and low gravity anomalies and moreover by several calderas the middle part between the aira and ata calderas may have a graben like structure a profile crossing the bay through sakurajima volcano is modeled on the basis of results from drilling and gravity surveys the basement has a graben like structure and is filled with coarse and low density deposits and the structure continues northwards to the aira caldera with a funnel shape a comparison of this area with the taupo rotorua depression in new zealand and lake toba in indonesia leads the authors to the conclusion that such major volcanic depressions may have been formed by amalgamation of a series of caldera like structures which were formed by multiple violent explosions accompanied by ejection of a tremendous amount of pyroclastic material

the transition from temperate phases to stadials in the long upper pleistocene sequence from les echets france abstract from two sections of the long sequence of les echets corresponding to the end of the eemian and to the end of st germain ii interstadial respectively detailed pollen diagrams have been established which provide information about the climatic conditions prevailing during the transitions from very temperate periods to the following cold stadials

north atlantic sea surface temperatures for the last 1 1 million years summary a 1 2 ma time series of north east atlantic sea surface temperature sst has been assembled from the spliced record of piston core k 708 7 0 68 0 ma and hydraulic piston cores taken in nearby dsdp hole 552a 1 2 0 68 ma a no analogue fauna precludes making credible sst estimates in the interval 1 2 1 1 ma but the record above 1 1 ma is suitable for sst estimates and related time series analysis the amplitude of sst variation is considerably higher in the brunhes than in the upper matuyama this is due both to colder glacial sst minima after 0 85 ma and to increasingly warm interglacial sst maxima from 0 7 to 0 4 ma the dominant periodicity in the sst signal is centred near 95 000 years it increases in amplitude by a factor of four from the bottom of the record to the top with the largest increase occurring between 0 7 and 0 4 ma this suggests a relatively gradual evolution of 100 000 year power over half a million years of the late quaternary rather than a single abrupt change at 0 9 ma significant but progressively smaller spectral peaks occur at periods of 54 000 41 000 31 000 23 000 and 19 000 years both the 54 000 year and 31 000 year signals may be a response to insolation forcing by minor obliquity terms long term 18 o records show small responses by the ice sheets at or near these two periods indicating the probable initial response of the climate system to these insolation rhythms in phase relationships between 18 o and sst at these periods suggest that the ice sheets then impose these rhythms on the ocean with no lag the mechanism by which such small insolation and ice volume signals become enhanced in the sst record is not clear

potential field and bathymetric investigation of the monowai volcanic centre kermadec arc implications for caldera formation and volcanic evolution the dynamics of caldera formation are affected by internal factors such as magma chamber structure and properties and regional tectonic stresses understanding their interrelationship is important for assessing volcanic hazard and reconstructing the evolution of a volcano the monowai volcanic centre located at the tonga kermadec arc is a basaltic andesitic submarine stratovolcano and caldera recent surveys have shown that it is active but little is known about its structure and evolution here we present a combined analysis of swath bathymetry and potential field data from monowai acquired during cruise so215 on the r v sonne in 2011 april june the monowai caldera is associated with a 20 25 mgal bouguer gravity anomaly high and a broad positive magnetic anomaly short wavelength magnetic anomalies of up to 1400 and 800 nt are observed along the caldera rim and on the summit of monowai cone inversion of the bouguer gravity anomaly data shows that the caldera high is caused by a buried dense body with density contrast of up to 450 kg m 3 with respect to the surrounding arc crust the body has a volume of 250 km3 and is divided into a main unit extending from 3 to 6 km depth and a shallower ring structure that underlies the rim of monowai caldera we estimate the density of the body to be 2650 2850 kg m 3 suggesting a mafic composition the ring structure is interpreted as set of ring dykes and the main unit as a solidified or partly solidified magma chamber system the monowai pluton the observed magnetic anomalies are consistent with pluton intrusion within the bruhnes magnetic polarity analysis of the swath bathymetry data shows that monowai is located in a 20 km wide graben part of an en echelon left stepping horst and graben system that spans the length of the arc and backarc the monowai caldera is elongated perpendicular to the direction of rifting suggesting that it is affected by the regional stress regime geomorphological analysis suggests that the caldera was created by repeated collapse of a single caldera structure and that its complex shape and multiple ring faults can be attributed to prolonged activity and multiple cycles of inflation and collapse we propose a multiphase evolution of the monowai volcanic centre comprising initial magma emplacement and crustal inflation magma chamber evacuation and caldera collapse caldera resurgence and mass waisting southward migration of the eruptive vent and formation of monowai cone it remains unclear whether the current eruption at the monowai cone is fed directly from a small underlying magma chamber or laterally from the monowai pluton observation of radial fissure ridges on its flanks suggests that a shallow magma body may have been recently emplaced beneath the summit causing inflation and the formation of extensional cracks the summit appears unstable and may be prone to lateral or vertical collapse therefore the region remains a potential source of regional volcanic and tsunami hazard

the most complete quaternary record of the swiss alpine foreland abstract the open pit section at thalgut near berne switzerland had already been considered as a quite complete reference section with interglacial lacustrine beds complex glacial sequences and evidence for morphogenetic activity during an earlier interglacial by a drilling operation this section has been extended and completed a long core of a still older interglacial has been recovered containing palynostratigraphic segments characterized by high percentages of pterocarya and fagus pollen assemblages with this discovery the thalgut section has become the most complete quaternary sequence of the northern alpine foreland with two different interglacial lacustrine beds and with a relic paleosoil separated each by complex glacial and glaciolacustrine sediments this record also implies a much older age for maximum erosion in the alpine foreland

controls on timing of exhumation and deformation in the northern peruvian eastern andean wedge as inferred from low temperature thermochronology and balanced cross section in northern peru a 500 km long regional balanced section has been constructed across the eastern andean wedge using fieldwork industrial seismic sections and wells the structure is characterized by a thin skinned thrust system involving the eastern cordillera ec the sub andean zone saz and the maranon foredeep in the saz and the easternmost foredeep the development of the thrust system has been driven by the combination of two structural events permian thrust faults had been reactivated to form a basement duplex underlying the saz and the foredeep at the same time a triassic jurassic extensional basin has been transported as a crustal ramp anticline on to the duplex roof fault giving rise to the ec the impingement of the ec was responsible for the deformation of the saz and the propagation of the thrust wedge the minimum shortening calculated is 142 km representing a shortening strain of 28 a sequential restoration calibrated by u th he and fission track dating on apatites and vitrinite reflectance values shows that shortening rates vary from 7 1 mm yr 1 between 17 and 8 ma to 3 6 mm yr 1 between 8 ma and today and suggests that the thrust wedge commenced propagation between 30 and 24 ma when compared with other andean thrust wedges we suggest that the timing of the thrust wedge propagation is not a simple function of the distance to the hinge of the bolivian orocline and the propagation is not controlled by the precipitation regime we rather suggest that reactivated basement faults favored thrust wedge propagation

tulelake california the last 3 million years abstract the tulelake basin formed by east west extension and faulting during the past several million years contains at least 550 m of lacustrine sediment interdisciplinary studies of a 334 m long cored section from the town of tulelake california near the center of the basin document a 3 m y record of environmental changes the core consists of a thick sequence of diatomaceous clayey silty and marly lacustrine sediments interbedded with numerous tephra layers paleomagnetic study puts the base of the core at about 3 0 ma twelve widespread silicic tephra units provide correlations with other areas and complement age control provided by magnetostratigraphy mafic and silicic tephra units erupted from local sources are also common in the core widespread tephra units include the llao rock pumice tsoyawata 7 ka the trego hot springs bed 23 ka and the rockland 0 40 ma lava creek 0 62 ma and rio dell 1 5 ma ash beds as well as several ash beds also found at summer lake oregon and an ash bed originally recognized in dsdp hole 173 in the northeastern pacific several tephra layers found in the core also occur in lacustrine beds exposed around the margins of the basin and elsewhere in the ancestral lacustrine system diatoms are present throughout the section pollen is present in most of the section but some barren zones are found in the interval between 50 and 140 m the greatest change in behavior of the pollen record takes place just above the top of the olduvai normal polarity subchronozone ostracodes are present only in high carbonate 10 caco3 intervals evolutionary changes are found in the diatom and ostracode records bulk geochemical analyses show significant changes in elemental composition of the sediment through time

critical taper model of fold and thrust belts and accretionary wedges the fold and thrust belts and submarine accretionary wedges that lie along compressive plate boundaries are one of the best understood deformational features of the earth s upper crust although there is considerable natural variation among the many fold and thrust belts and accretionary wedges that have been recognized and explored several features appear to be universal in cross section fold and thrust belts and accretionary wedges occupy a wedge shaped deformed region overlying a basal detachment or decollement fault the rocks or sediments beneath this fault show very little deformation the decollement fault characteristically dips toward the interior of the mountain belt or in the case of a submarine wedge toward the island arc the topography in contrast slopes toward the toe or deformation front of the wedge deformation within the wedge is generally dominated by imbricate thrust faults verging toward the toe and related fault bend folding two north american fold and thrust belts that exhibit these features are shown in figure 1 neither of these two examples is tectonically active today the southern canadian fold and thrust belt was active during the late jurassic and cretaceous 150 100 ma whereas the southern appa lachians were deformed during the late carboniferous to permian alle ghenian orogeny 300 250 ma figure 2 shows two examples that are currently active the taiwan fold and thrust belt produced by the sub duction of the eurasian plate beneath the philippine sea plate suppe 1981 1987 and the barbados accretionary wedge produced by the sub

reconstructing the interacting effects of base level climate and tectonic uplift in the lower mino river terrace record a gradient modelling evaluation the origin of the lower mino river terraces in the nw iberian peninsula has been a topic of debate since the 1940s various hypotheses about their main controlling factors have been put forward but general consensus is still lacking field studies of terrace distribution and the weathering of quartzite pebbles in the terrace deposits demonstrated that terrace longitudinal correlation is not parallel to the current river bed in addition the longitudinal profile model fluver2 was used to simulate the profile evolution of the mino river over the past 450 ka a reconstructed longitudinal profile and an offshore climate record were used as inputs several scenarios with variable uplift rates were investigated and evaluated against properties of four selected reaches along the river for a match with the number of terraces their relative altitude timing and sediment thickness an uplift scenario with a net constant vertical uplift rate of 0 08 m ka 1 yielded the best results the best fit scenarios indicate that base level changes from glacioeustatic changes in combination with tectonic uplift are the main driving forces of the observed terrace formation and valley incision contrary to most nw european fluvial systems the timing of upstream controlled sediment supply has a less dominant effect on terrace formation this can be explained by the close proximity to the narrow passive atlantic margin

surface expression of eastern mediterranean slab dynamics neogene topographic and structural evolution of the southwest margin of the central anatolian plateau turkey 1 the southwest margin of the central anatolian plateau has experienced multiple phases of topographic growth including the formation of localized highs prior to the late miocene that were later affected by wholesale uplift of the plateau margin our new biostratigraphic data limit the age of uplifted marine sediments at the southwest plateau margin at 1 5 km elevation to 7 17 ma and regional lithostratigraphic correlations imply that the age is 6 7 ma single grain ca tims u pb zircon analyses from a reworked ash within the marine sediments yield dates as young as 10 6 ma indicating a maximum age that is consistent with the biostratigraphy our structural measurements within the uplifted region and fault inversion modeling agree with previous findings in surrounding regions with early contraction followed by strike slip and extensional deformation during uplift focal mechanisms from shallow earthquakes show that the extensional phase has continued to the present broad similarities in the change in the tectonic stress regime after 8 ma and the onset of surface uplift after 7 ma imply that deep seated process es caused post 7 ma uplift the geometry of lithospheric slabs beneath the plateau margin pliocene to recent alkaline volcanism and the uplift pattern with accompanying normal faulting point toward slab tearing and localized heating at the base of the lithosphere as a probable mechanism for post 7 ma uplift of the southwest margin considering previous work in the region there appears to be an important link between slab dynamics and surface uplift throughout the anatolian plateau s southern margin

pleistocene climates in china dated by magnetic susceptibility the magnetic susceptibility of loess and interbedded soils in central china varies with the degree of pedogenesis and serves as a proxy measure of climate the concentration of magnetic minerals in the sediment is inversely proportional to sedimentation rates throughout the brunhes epoch susceptibility measurements combined with the reversal stratigraphy provide a time scale that is independent of astronomic chronology on this scale the susceptibility record closely parallels the oxygen isotope fluctuations in deep sea sediments suggesting a close interdependence of the chinese dust falls the volume of land based ice and global climate

relationships between fluvial evolution and karstification related to climatic tectonic and eustatic forcing in temperate regions this paper reviews the diversity of relationships between river evolution and karstogenesis it also underlines the fundamental role of numerical dating methods e g cosmogenic nuclides applied to sedimentary sequences in tiered cave passages as they have provided new insights into these complex interactions although karst terrain is widespread worldwide we focus on european karst catchments where the sedimentary records are especially well preserved we review the recent dating of fluvial sediments and speleothems to examine the timing of karstification incision and deposition in cave levels the most complete alluvial records occur in tectonically uplifted high mountains where some of the oldest sediment fills date to the miocene evidence indicates that not only uplift but also climatic conditions and fluvial dynamics e g knickpoint retreat increased channel flow and or sediment load and stream piracies can play a major role in speleogenesis and geomorphological evolution in evaporite rocks speleogenesis is characterized by rapid dissolution and subsidence in european catchments gypsum cave development largely occurred during cold climate periods while limestone caves formed during warm interglacial or interstadial phases our synthesis is used to propose four models of fluvial and karst evolution and highlight perspectives for further research

correlations of cave levels stream terraces and planation surfaces along the river mur timing of landscape evolution along the eastern margin of the alps the transition zone of the eastern alps to the pannonian basin provides one of the best sources of information on landscape evolution of the eastern alpine mountain range the region was non glaciated during the entire pleistocene thus direct influence of glacial carving as a landscape forming process can be excluded and relics of landforms are preserved that date back to at least the late neogene in this study we provide a correlation between various planation surfaces across the orogen basin transition in particular we use stream terraces planation surfaces and cave levels that cover a vertical spread of some 700 m our correlation is used to show that both sides of the transition zone uplifted together starting at least about 5 ma ago for our correlation we use recently published terrestrial cosmogenic nuclide tcn burial ages from cave sediments new optically stimulated luminescence osl ages of a stream terrace and u th ages from speleothems minimum age constraints of cave levels from burial ages of cave sediments covering the last 4 ma are used to place age constraints on surface features by parallelizing cave levels with planation surfaces the osl results for the top section of the type locality of the helfbrunn terrace suggest an early wurm development 80 5 3 7 to 68 7 4 0 ka the terrace origin as a penultimate gravel deposit in classical alpine terminology riss is therefore questioned u series speleothem ages from caves nearby indicate formation during marine isotope stages mis 5c and 5a which are both interstadial warm periods as osl ages from the terrace also show a time of deposition during mis 5a ending at the mis 5 4 transition this supports the idea of temperate climatic conditions at the time of deposition in general tectonic activity is interpreted to be the main driving force for the formation and evolution of these landforms whilst climate change is suggested to be of minor importance obvious hiatuses in miocene to pleistocene sediments are related to ongoing erosion and re excavation of an uplifting and rejuvenating landscape

brunhes matuyama polarity epoch boundary in the osaka group of the senriyama hills southwest japan abstract magnetic measurements were carried out on core samples of the osaka group distributed in the senriyama hills north of osaka bay the studied section about 53 m thick includes four layers of clay or silts and intercalated sand and gravel layers the four muddy layers which have been known as the ma 3 ma 4 ma 5 and ma 6 marine clay beds in ascending order seem to have been deposited in shallow marine environments possibly associated with transgression during interglacial periods the mud layers were sampled using a new type of core sampler designed to mark the north direction on the cores the magnetic analysis revealed that the upper part of the section ma 5 and ma 6 has normal polarity and that the lower part ma 3 has reversed polarity the ma 4 bed which was formerly assigned to the brunhes chron showed reversed polarity in the lower part while its upper part had downward inclinations this result shows that the brunhes matuyama polarity transition occurred in an interglacial period the ma 4 layer is assigned to the period of marine transgression corresponding to the oxygen isotope stages 19 18

new evidence for the incision history of the liuchong river southwest china from cosmogenic 26al 10be burial ages in cave sediments cosmogenic nuclides be 10 and al 26 have been analyzed for sediments from the multilevel riverside caves along the liuchong river at the southeastern margin of the tibetan plateau the liuchong river is the northern origin of wujiang river which passes through the northwestern guizhou plateau and cuts down hundreds of meters into the bedrock leaving behind an abundance of multilevel caves the measured al 26 be 10 ratios produced the apparent burial ages in range of 0 49 2 85 ma taking into account of geomorphic and geological backgrounds the dashi cave located at the highest level along the liuchong river system formed around 0 75 ma ago which probably suggests the initial formation age of the modern wujiang river the resulted incision rate of similar to 480 m ma in guizhou in the last 0 75 ma is slightly higher than those in adjacent areas this feature implies an intensive downcutting history of the liuchong river during the quaternary which might be primarily caused by the uplift of tibetan plateau cut through of the three gorges and soluble carbonate bedrock c 2013 elsevier ltd all rights reserved

gravity fields and the interpretation of volcanic structures geological discrimination and temporal evolution abstract a review of gravity data reflecting shallow concealed structures on volcanoes demonstrates that valuable information may be derived on the geological development of such structures and on the dynamic evolution of active volcanoes to a first approximation all recorded examples of anomalous gravity fields associated with volcanoes are concentric with and have sources that lie within the volcanic edifice positive anomalies with wavelengths less than 20 km and amplitudes up to ca 30 mgal characterise mainly basaltic volcanoes from various tectonic settings and are caused by a relatively dense intrusive complex magma body which contrasts with its surroundings either because the body is more mafic than average or more likely because near surface previously erupted materials are uncompacted negative anomalies with wavelengths up to 100 km and amplitudes up to ca 60 mgal occur over much larger volcanic calderas many of which have erupted highly silicic pyroclastic ash and pumice uncompacted silicic caldera infill with a possible contribution from low density magma bodies is responsible for the observed anomalies there is some evidence for a continuum of gravity anomaly types that corresponds to the geological evolution of volcanic systems generally from primitive rift or subduction related basaltic andesite to mature high level silicic calderas repeated microgravity observations over active volcanoes enable magma movements variations in magma input and changes in magma density to be monitored closely dynamic modelling of volcanic systems is providing new evidence on the behaviour of concealed magma bodies and could have considerable potential for predicting eruptive events

stratigraphy paleomagnetism and magnetic fabric of the toba tuffs constraints on the sources and eruptive styles the toba depression in north central sumatra is a complex of several overlapping calderas resulting from three major ignimbrite forming eruptions within the depression the upland masses of samosir and northern uluan consist of welded ignimbrite capped by coarse breccia and lacustrine sediment hitherto interpreted to be two parts of a single resurgent dome this study has demonstrated that the welded tuffs of samosir and uluan have different magnetic polarities and therefore at least two different ignimbrites are present the samosir uluan massif may consist of parts of two resurgent domes the first ignimbrite eruption occurred at 0 84 ma and produced a very thick 400 m densely welded unit having a reversed polarity anisotropy of magnetic susceptibility ams flow direction and lithic size data indicate that the source lies in the southern part of the toba depression and the thick deposit of uluan is thought to have ponded in a 40 km wide caldera the second ignimbrite is normally magnetized ams flow direction data indicate two separate source vents one to the north in the haranggaol caldera and another to the south the thick deposit at samosir is thought to have ponded in the southern caldera coarse sediments then accumulated over samosir and northern uluan and were capped by lacustrine deposits a renewed episode of resurgence then uplifted samosir island and possibly the northern part of uluan at approximately 0 075 ma the last and apparently largest ignimbrite eruption occurred from calderas in the north and south parts of the toba depression this ignimbrite is mostly nonwelded and normally magnetized part of the uluan dome was destroyed by collapse of the sibandung caldera and latung graben and concomitant with renewed subsidence of the haranggaol and porsea calderas

periglacial environments during the early pleistocene in the southern netherlands and northern belgium abstract the palaeoenvironment of three early pleistocene glacials in the netherlands and belgium are studied the intra tiglian beerse glacial and the eburonian and menapian cold stages climatic conditions are expressed by specific periglacial phenomena and by palaeobotanical data the three cold periods are characterized by a nearly treeless tundra vegetation and a continuous or discontinuous permafrost mean summer temperatures are estimated around or slightly below 10 c while mean annual temperatures were below 6 to 4 c

new zealand quaternary stratigraphy an overview abstract new zealand quaternary strata including marine sediments loess volcanic and glacial deposits offer detailed records of quaternary environmental change from a geographically significant location time stratigraphic subdivision of new zealand quaternary strata based on marine biostratigraphy and climatostratigraphy has resulted in a series of locally defined stages and substages the plio pleistocene boundary as defined at vrica in italy and dated at ca 1 63 ma lies near the top of the nukumaruan stage in new zealand the first faunal evidence of cooling in new zealand plio pleistocene sequences occurs much earlier at the base of the nukumaruan stage ca 2 4 ma with the appearance in central new zealand of the subantarctic taxa chlamys delicatula and jacquinotia edwardsii although glacial deposits of the south island have long been central to new zealand quaternary stratigraphy they are poorly dated and lack continuity more complete records of quaternary events are found within uplifted marine strata and associated terrestrial deposits of the north island such as in wanganui basin the use of widespread rhyolite tephra for precise correlation and dating in north island offers much for improved land sea correlations direct correlation of on land sequences using tephra with oxygen isotope stages of deep sea cores may negate the need for further local time stratigraphic subdivision in the new zealand quaternary however there will still be scope for regional comparisons highlighting climatic changes not apparent in deep sea cores

the fossil record of the desert adapted south american rodent tympanoctomys rodentia octodontidae paleoenvironmental and biogeographic significance abstract new mandibular remains of one specimen of the desert adapted south american rodent tympanoctomys from the pleistocene of central argentina are described these materials together with a hemimandible previously analyzed by ameghino represent the limited paleontological record of the genus and the first undoubted record of a living genus of the octodontinae subfamily the taxonomic paleoenvironmental and biogeographic significance of these materials is discussed the sediments yielding the new remains at the coastal region of mar del plata represent one of the glacial events that deposited the pichileufu drift in the cordillera region of argentina between isotopic stages 23 and 25 we propose that as a consequence of the glaciation favorable habitats for populations of tympanoctomys would have extended eastwards consequently the present distributional pattern of the genus may be considered a relict

structural controls on a geothermal system in the tarutung basin north central sumatra abstract the sumatra fault system provides a unique geologic setting to evaluate the influence of structural controls on geothermal activity whereas most of the geothermal systems in indonesia are controlled by volcanic activity geothermal systems at the sumatra fault system might be controlled by faults and fractures exploration strategies for these geothermal systems need to be verified because the typical pattern of heat source and alteration clays are missing so that conventional exploration with magnetotelluric surveys might not provide sufficient data to delineate favorable settings for drilling we present field geological structural and geomorphological evidence combined with mapping of geothermal manifestations to allow constraints between fault dynamics and geothermal activity in the tarutung basin in north central sumatra our results indicate that the fault pattern in the tarutung basin is generated by a compressional stress direction acting at a high angle to the right lateral sumatra fault system nw se striking normal faults possibly related to negative flower structures and nnw sse to nne ssw oriented dilative riedel shears are preferential fluid pathways whereas ene wsw striking faults act as barriers in this system the dominant of geothermal manifestations at the eastern part of the basin indicates local extension due to clockwise block rotation in the sumatra fault system our results support the effort to integrate detailed field geological surveys to refined exploration strategies even in tropical areas where outcrops are limited

rates of erosion and topographic evolution of the sierra nevada california inferred from cosmogenic26al and10be concentrations concentrations of cosmogenic 26 al and 10 be in cave sediments and bedrock surfaces combined with studies of landscape morphology elucidate the topographic history of the southern sierra nevada over the past 5 ma caves dated by 26 al 10 be in buried sediments reveal that river incision rates were moderate to slow between c 5 and 3 ma 0 07 mm a 1 accelerated between 3 and 1 5 ma c 0 3 mm a 1 and then have subsequently become much slower c 0 02 mm a 1 although the onset of accelerated incision coincides in time with both postulated pliocene tectonism and pronounced global climate change we argue that it primarily represents the response to a discrete tectonic event between 3 and 5 ma dated cave positions reveal that prior to 3 ma river canyons displayed up to 1 6 km of local relief suggesting that pliocene rock uplift elevated pre existing topography renewed incision beginning c 3 ma deepened canyons by up to 400 m creating narrow inner gorges tributary streams exhibit strong convexities indicating that the transient erosional response to pliocene uplift has not yet propagated into upland surfaces concentrations of 26 al and 10 be in bare bedrock show that upland surfaces are eroding at slow rates of c 0 01 mm a 1 over the past c 3 ma upland surfaces eroded slowly while adjacent rivers incised rapidly increasing local relief although relief production probably drove at least modest crestal uplift considerable prepliocene relief and low spatially averaged erosion rates suggest that climatically driven rock uplift is not sufficient to explain all uplift implied by tilted markers at the western edge of the range despite the recent pulse of erosion spatially averaged erosion rates are low and have probably acted to preserve the broad topographic form of the sierra nevada throughout much of the late cenozoic copyright 2005 john wiley sons ltd

titan s north south asymmetry from hst and voyager imaging comparison with models and ground based photometry abstract new measurements of titan s hemispheric brightness asymmetry from hst images from 260 to 1040 nm show that the contrast is strongest near 450 nm blue and with the opposite sign at 889 nm methane band comparison with a full titan year of disk integrated albedo data indicates that the seasonal cycle in asymmetry is smooth but is insufficient to explain the variation in albedo and a twice per year global albedo enhancement 50 larger than the hemispheric asymmetry amplitude is required as noted by other workers we also report measurements of limb darkening strongest at red wavelengths and note that the transition zone between the hemispheres lies in the northern brighter hemisphere at present comparison of models to the hst data set indicates that a change in aerosol number density above 70 km and largely below 120 km is the likely mechanism and is probably driven by aerosol transport by meridonal and vertical winds

abrupt glacial valley incision at 0 8 ma dated from cave deposits in switzerland glacial erosion dramatically alters mountain landscapes but the pace at which glaciers carve a previously fluvial landscape remains poorly defined because long term valley incision rates are difficult to measure here we reconstruct the lowering history of the aare valley switzerland over the past 4 m y by dating cave sediments with cosmogenic 26al and 10be incision accelerated from 120 m m y to 1200 m m y at 0 8 1 0 ma at least 1 m y after the onset of local glaciation rapid incision may have been triggered by lowering of the equilibrium line altitude at the mid pleistocene climate transition

evaluation of aster gdem2 srtmv3 0 alos aw3d30 and tandem x dems for the peruvian andes against highly accurate gnss ground control points and geomorphological hydrological metrics abstract we present an analysis for peru of the vertical accuracy and derived geomorphological parameters of three freely available digital elevation models dems with 30 m grid sizes and one commercially available 12 m dem aster gdem2 srtmv3 0 hereafter called srtm3 alos world 3d aw3d30 and 12 m tandem x their elevation values were compared against values measured with a dual frequency trimble 5800 global navigation satellite systems gnss receiver with two antennas in static relative positioning a total of 139 ground control points gcps with elevations of up to 4334 m above sea level asl were obtained from four topographically contrasting regions along the flat arid coast the semi dry andes and the amazon rainforest the combined results of the four areas showed that the residuals of aster gdem2 had a root mean square error rmse of 6 907 m srtm3 5 113 m and aw3d30 6 246 m for the two areas where tandem x was investigated a rmse of 1 666 m was obtained when considering each area individually of the three 30 m dems srtm3 performed best in all areas while aster gdem2 was always performing worst the standard deviation sd of the residuals of aster gdem2 and aw3d30 varied much more between the four study areas than the sd of srtm3 and tandem x it was possible to establish linear correlations with r2 0 95 between the gnss measured and dem derived elevation values for all areas and all dems which can be used to correct aster gdem2 and aw3d30 for peru no relationship was found between absolute elevation and residuals slope angle of 15 however correlated to much higher residuals for srtm3 and aw3d30 whereas a constant increase in residual correlated to a constant increase in slope angle for tandem x in general the highest residuals corresponded to the highest slope classes a comparison of absolute elevation values and slope angles of selected areas between aster gdem2 and srtm3 as well as between aw3d30 and srtm3 showed in all cases more deviation from true values in areas with steeper slopes this effect seems independent of vegetation the presence of buildings however severely affected performance of aster gdem2 for some areas aw3d30 suffered from mismatch between adjacent scenes and horizontal and oblique stripping an analysis of drainage networks showed that all three 30 m dems were capable of producing a similar number of strahler orders total number of channels minimum and maximum channel length and accumulative channel length all dems produced accurate networks in the upper reaches of the catchments but suffered in flat areas such as wide fluvial valleys and sink filled areas aster gdem2 in particular produced parallel river channels and unnatural short cuts our results agreed well with those of other studies elsewhere around the world and showed that i the vertical error is much less than those officially reported for all dems ii slope is the most determinant factor in dem accuracy we conclude that srtm3 delivers the most stable performance in almost all tests and is therefore the dem of choice for landscape analysis in peru tandem x 12 m performed very well in our elevation accuracy test and could become a worthy successor to srtm3

quaternary and upper pliocene glaciations and forest development in the tropical andes evidence from a long high resolution pollen record from the sedimentary basin of bogota colombia pollen analysis of 1230 samples from a 357 m long core of lake sediments from the sedimentary basin of bogota eastern cordillera colombia alt 2550 m above sea level has provided a high resolution record of changes in the andean vegetation belts and long range climatic fluctuations during the last 3 5 ma direct time control is provided by k ar datings and fission track datings of 14 intercalated volcanic ash layers the resulting pollen diagram has been divided into 55 pollen zones representing 27 complete major climatic cycles glacial interglacial cycles a tentative correlation with the marine oxygen isotope chronology and the european stratigraphical climatic subdivision could be established the altitudinal position of the forest line which corresponds with the 9 5 c isotherm shifted between minimal c 1700 1800 m and maximal c 3400 3700 m alt at present situated at c 3100 m alt which rendered the altitudinal position of the high plain of bogota the dry bed of a former lake at 2550 m a sensitive recorder of temperature changes the estimated fluctuations in mean annual temperature at the level of the high plain of bogota are from 15 c a distinct change in the nature of the climatic cycles occurs around 2 5 ma b p the interval of 3 5 2 5 ma b p shows high frequency low amplitude climatic oscillations whereas the last 2 5 ma is characterized by low frequency high amplitude climatic oscillations with a superposed high frequency oscillation it is assumed that these oscillations correspond mainly with the variations in orbital eccentricity and obliquity the major constituents making up the andean forest have been subjected to considerable changes in the course of time in the early pliocene forests vallea and myrica are prominent elements weinmannia was almost absent the role of polylepis in the timberline forests increased markedly around 3 1 ma b p and also migrated by adaptation from the upper andean forest line to higher elevations the closure of the isthmus of panama during the pliocene enabled northern hemisphere elements to migrate into south america alnus reached the area of bogota around 2 7 ma b p and dramatically changed the vegetation especially on the flats around the lake of bogota where alnus swamp forests replaced myrica carr around 2 9 ma b p weinmannia became an important constituent of the upper andean forest but slightly later slope forests of alnus replaced parts of the area which had previously been covered by weinmannia forest the marked role of vallea in the andean forest diminished definitively after 2 5 ma b p quercus migrated more recently to south america and reached the area of bogota 1 ma b p it changed for the last time drastically the aspect of the andean forest all palynologically recognizable elements of the modern andean forest were present from now on and the subsequent adaptation and speciation of quercus and many other elements must have mainly taken place at the species level

titan s smile and collar hst observations of seasonal change 1994 2000 we observed titan with the hubble space telescope in november 2000 using the wide field plane tary camera wfpc2 and the space telescope imaging spectrograph stis considerable change is apparent be tween these and observations in 1994 1997 in particular the north south asymmetry at visible wavelengths has re versed with the southern hemisphere brighter as during the voyager epoch the asymmetry shows considerable varia tion with wavelength in the near infrared in the 889nm methane band the asymmetry which formerly resembled a smile has reversed in the last 3 years while at 953nm the southern limb is still bright a south polar collar dark at ultraviolet wavelengths is apparent some five years after equinox

late pliocene to early pleistocene ostracod stratigraphy and palaeoclimate of the lodin elv and kap kobenhavn formations east greenland the ostracoda documented in the lodin elv formation in east greenland provide us with data to reconstruct palaeotemperatures during the late pliocene palaeotemperature estimations use the overlap of temperature ranges of extant species in the deposits and indicate maximum summer bottom temperatures sbt of 4 c for member b diamict and slightly higher temperatures for member a 9 c these results are compared with new and previously published data from the kap kobenhavn formation in northeastern greenland ostracoda from the oldest part of this formation member a diamict indicate a sbt of about 4 c and confirm earlier views that these are glaciomarine sediments the ostracods of the lodin elv formation indicate a late pliocene to early pleistocene age and suggest contemporaneity with the kap kobenhavn formation the age of these two formations is considered in relation to the known ranges of pliocene marker species and to the timing of the onset of glaciations during the late pliocene three options are presented assuming that the diamict members of the two formations are contemporaneous then their age can be placed either shortly after 2 4 ma option a or at about 2 6 ma option b option a requires that the ranges of the two pliocene marker species pterygocythereis vannieuwenhuisei and rabilimis paramirabilis are not synchronous in arctic regions their lad s occurring later in greenland than in arctic north america option b requires that palaeomagnetic evidence from the upper part of unit b2 at kap kobenhavn be ignored a third option option c assumes that the two pliocene marker species are synchronous and that the two formations are of different age 2 6 ma for kap kobenhavn and 2 4 ma for lodin elv it is not clear at present which of these options is the most credible

titan s surface revealed by hst imaging we present for the first time relative albedo maps of titan s surface the maps were made from images taken by the hubble space telescope s planetary camera 295 km per pixel through atmospheric windows at 940 and 1080 nm coverage at all longitudes and between 45 s and 60 n was obtained with 14 orbits from 4 18 october 1994 each image is characterized by haze with both limb effects brightening and a large north south contrast subtracting an averaged image from each frame removes haze effects and reveals surface features of 10 maximum contrast many features are clearly visible in multiple images and in both filters but the surface map is dominated by a large bright roughly rectangular feature centered at 110 w 10 s and elongated in an east west direction 4000 2500 km2 this feature and others indicate the diversity of titan s surface we consider the origin of the bright feature in an otherwise dark landscape and suggest that highland washing by methane rainfall is a likely mechanism

depths and focal mechanisms of crustal earthquakes in the central andes determined from teleseismic waveform analysis and insar 1 we investigate the depths of crustal earthquakes mw 5 5 earthquakes from the global cmt catalog and previous work spanning 1944 2007 for 38 well recorded events we use teleseismic p and sh waveforms to model the strike dip rake focal depth and source time function we use insar observations of surface deformation from 9 earthquakes to compare inferred fault parameters with the waveform inversions and global catalogs to assess their accuracies while the depths from the insar and waveform analyses generally agree within error horizontal and depth errors in global catalogs are 10 to 50 km as found elsewhere as noted in previous work the majority of crustal earthquakes occur in the eastern cordillera and foreland regions of the central andes although a few normal and strike slip earthquakes occur beneath the altiplano plateau and in the forearc in southern peru and northernmost chile we propose a new interpretation of one of the basement thrusts shira mountain peru as a pop up block on the basis of our new earthquake depths we confirm that earthquakes in the flat slab areas of peru and argentina are within the sometimes aseismic lower crust lower crustal earthquakes are globally found in all types of tectonic settings only when the thermal lithosphere is more than 80 km thick and the amount of recent shortening extension is 30

patagonian origin of glacial dust deposited in east antarctica vostok and dome c during glacial stages 2 4 and 6 abstract the source area of continental dust deposited at both vostok and dome c sites east antarctica during the glacial stages stage 2 18 ka last glacial maximum stage 4 60 ka and stage 6 160 ka of the last two climatic cycles has remained constant the isotopic composition 87 sr 86 sr and 143 nd 144 nd of the ice core dust has been compared with the isotopic composition of the potential source areas antarctica new zealand southern africa australia and south america this comparison reveals the southern south american provenance of the dust for all three glacial periods as has already been shown for the lgm 1 we show that the patagonian loess and the marine shelf sediments from the argentine continental shelf which was variably emerged during glacial periods display different isotopic compositions and that the composition of the patagonian loess best matches the signature of the ice core dust the identification of the patagonian region as the source of the windblown dust deposited over east antarctica during all the latest glacial periods permits a better understanding of paleo atmospheric circulations of the last climatic cycles and a better constraint on the parametrization of dust sources for paleoatmospheric general circulation models

continuous pollen diagrams for the last 3 5 m y from israel vegetation climate and correlation with the oxygen isotope record abstract several continuous pollen diagrams have been obtained from boreholes penetrating the entire quaternary sequences of the hula and dead sea lakes in the jordan rift valley israel the dead sea served as a terminal base level through this period thus ensuring a complete continuous deposition volcanic intercalations within the hula lake sediments permit some control of the absolute datings a paleoclimatic model for the last 150 k y based on better dated sequences serves as a basis for correlating the israeli sections with the oxygen isotope records known from the oceans and the mediterranean the glacial phases are manifested in israel by periods of somewhat lower temperatures and higher rainfall some in summertime the interglacials are hot and dry with saharan conditions prevailing the interstadials are of the present day character of a short rainy winter and a dry hot long summer the first major cooling of the quaternary in israel took place some 2 4 2 6 m y ago followed by a series of alternating wetter and drier phases corresponding quite well to changes in the global ice volume expressed by the oxygen isotope curves it seems however that some successions of the glacial phases are grouped in israel into longer wetter periods with the interglacials manifested as interstadials a similar case is seen for some of the interglacials successions with glacial phases as interstadials a possible explanation for the difference between the continental and the ocean records may lie in the distribution of the global ice volume differences in the accumulations of ice at the arctic and antarctic regions during some of the glacial phases could explain the extent of a glacial period on land while not being apparent from the oxygen isotope records and vice versa for the interglacials thus a well developed ice cap on antarctica may cause only a minor glaciation in the northern hemisphere but be recorded as a full glacial in the oceans

geomorphic evidence of active deformation and uplift in a modern continental wedge top foredeep transition example of the eastern ecuadorian andes abstract the eastern ecuadorian andes appear as a fold and thrust belt adjacent to a continental foredeep represented by one of the world s largest tropical alluvial megafans the pastaza megafan debouching into the amazonian lowland the apex of the pliocene pleistocene megafan situated in the present day wedge top subandean zone has been cut by an erosion surface the western part of which has been uplifted of 500 m along the frontal thrust forming a poorly dissected plateau the mera plateau this erosion surface erased most of the previous fluvial landscape but preserved a large thrust related anticlinal hinge deforming less erodible underlying strata the mirador fold and smaller sized anticlines this surface has been then incised by two antecedent major rivers the pastaza and the napo and few tributaries the plateau edge is marked by a series of large scale gently sloping landslides clustered along a 70 km long concave eastward line associated with the frontal thrust fault the newly formed immature rivers issued from the landslides or sourced within east dipping remnants of the erosion surface downstream of the landslide line constitute the greatest part of the streams feeding the ecuadorian amazonian basin at 70 to 100 km from the landslide line the drainage abruptly changes from highly immature to mature with a well defined hinge line representing the outer limit of landslide and tectonic control the diversions of the pastaza river indicate ongoing fold growth since at least the late pleistocene in the eastern cordillera and the early holocene in the mera plateau the preserved terraces of the pastaza valley are all degradational and are ascribed to periods of tectonic seismic activity alternating with periods of tectonic quiescence or decreased seismic activity rather than to climatic events 14c dating of the plateau erosion surface and of the upper pastaza terraces indicates that the minimum average incision rate since 18 000 years bp varies locally in the upper pastaza valley from 0 5 to 0 67 cm year 1 increasing from 18 000 years bp to now a comparison of these incision rates with fold and thrust fault uplift rates indicates that incision in the upper pastaza valley was a result of rapid uplift up to 1 cm year 1 along the mirador fold and thrust which caused a restoration of the local equilibrium profile of the upper reach combined with smaller local fault uplift along the westernmost thrust faults the uplift of the whole mera plateau with respect to the upper amazonian basin gives a minimum average uplift rate of 2 8 cm year 1 since 18 000 years bp the overall uplift of the mera plateau and the eastern cordillera is likely to have been caused by a regional scale low angle thrust ramp emerging as the frontal thrust fault

long continental records of climate an introduction abstract the symposium on long continental records presented new information on past climates on land it seems that throughout the last 2 5 million years the climate in the middle latitudes changed in the same complex fashion as during the better known late pleistocene and holocene times over 40 interglacial glacial shifts took place during this interval out of those 40 10 12 glacials were markedly stronger and or longer lasting than the others the apparently abrupt shifts from interglacials to glacials were probably gradual oscillatory coolings interrupted by warming episodes in that respect the detailed anatomy of the past climate changes does not differ substantially from the climate oscillations documented by instrumental weather records in the last two centuries the pronounced expansions of dry and cold steppes on land were accompanied by corresponding increases of the ice volume indicated by the oxygen isotope ratio the two exceptions occurred around 1 4 ma ago and 1 6 ma ago the reason for this discrepancy is not known by far the most expressed change of land environments occurred at about 2 4 ma ago

stratigraphy and isotope records of middle and late pleistocene mollusks from a continuous corehole in the hula basin northern jordan valley israel morphological changes in melanopsis shells and the sudden disappearance of viviparus were observed in a continuous core representing about 700 000 yr taken from the l 12 corehole in the hula basin northern jordan valley israel two major events in 18o values are recorded the first at about 435 000 yr b p is accompanied by a shift in 13c values and indicates a shallowing phase with slightly higher evaporation this event is concurrent with the abundant occurrence of a monotypic distorted melanopsis suggesting an ecophenotypic event during deposition of the lake s pleistocene lower lacustrine beds the second major isotopic event is evidenced in the lower part of the section as a gradual depletion in 18o toward the bottom of the corehole minor shifts of 1 20 in the oxygen isotope content along the core may represent changes in the 18o values of the water from glacial to interglacial periods representing the major climatic cycles of the pleistocene five of these cycles were observed along the core

sumatran granitoids and their relationship to southeast asian terranes abstract three subparallel n s trending granitoid provinces occur in southeast asia the eastern granitoid province of peninsular malaysia the central granitoid province extending from northwestern thailand to the western part of peninsular malaysia and to the tin islands indonesia and the western granitoid province in western thailand and burma it has been asserted that each of these granitoid provinces is restricted to one of the southeast asian terranes defined using gondwanan palaeozoic stratigraphic relations and faunal distributions very little is known about possible continuations of these terranes in sumatra and here we use the granite basement terrane concept and the geochemical and isotopic compositions of sumatran granitoids and fragmental rocks to extend the southeast asian terrane boundaries into sumatra and investigate the nature of the sumatran lithosphere granitoids west of the semangko fault and within the basement of the quaternary volcanic arc have low initial 87 sr 86 sr values granitoids in eastern sumatra east of the semangko fault including those of the tin islands of bukit batu close to palembang the hatapang pluton and granodiorites and fragmental volcanics of the lake toba area and possibly sijunjung pluton in central sumatra all share high 87 sr 86 sr values and other s type isotopic and compositional similarities and seem to be related to the central granitoid province s type granitoids of the sibumasu terrane siam burma malaysia sumatra metcalfe 1984 these similarities suggest that the granitoids define a granite basement terrane which may form the basement of the sibumasu terrane they also imply that the magmatism of the toba caldera was derived from the same crustal source granitoids that are geochemically and isotopically similar to those of the western province are not yet known in sumatra and granitoids similar to those of the eastern province are rare the distribution of sumatran granitoids suggests that the semangko fault and the sunda strait may mark the southwesternmost and southeasternmost limits of the sibumasu terrane and that the boundary between the central and the eastern granite provinces may run through the tin islands

trench parallel flow and seismic anisotropy in the mariana and andean subduction systems shear wave splitting measurements above the mantle wedge of the mariana1 and southern andean2 3 subduction zones show trench parallel seismically fast directions close to the trench and abrupt rotations to trench perpendicular anisotropy in the back arc these patterns of seismic anisotropy may be caused by three dimensional flow associated with along strike variations in slab geometry1 2 3 4 5 the mariana and andean subduction systems are associated with the largest along strike variations of slab geometry observed on earth6 7 and are ideal for testing the link between slab geometry and solid state creep processes in the mantle here we show with fully three dimensional non newtonian subduction zone models that the strong curvature of the mariana slab and the transition to shallow slab dip in the southern andes give rise to strong trench parallel stretching in the warm arc and warm back arc mantle and to abrupt rotations in stretching directions that are accompanied by strong trench parallel stretching these models show that the patterns of shear wave splitting observed in the mariana and southern andean systems may be caused by significant three dimensional flow induced by along strike variations in slab geometry

vertical distribution of scattering hazes in titan s upper atmosphere abstract radial intensity scars of a voyager 2 high phase angle image of titan have been inverted to yield vertical extinction profiles at 1 intervals around the limb a detached haze layer with peak particle number densities 0 2 cm 3 exists at all latitudes south of 45 n and at an altitude of 300 350 km the optical depth 0 01 level lies at a radius of 2932 5 km at the equator and at a radius of 2915 10 km over the poles altitudes of 357 5 and 340 10 km respectively in addition to the haze layer at 300 350 km there is a small enhancement in the extinction at 450 km which exists at all latitudes between 75 s and 60 n

active mountain building along the eastern colombian subandes a folding history from deformed terraces across the tame anticline llanos basin active crustal shortening and surface uplift are vividly expressed in the foothills of the eastern cordillera of colombia quaternary alluvial fan and terrace deposits are folded and uplifted tens to hundreds of meters above the local base level recording deformation and incision of the landscape we used geomorphic observations and structural analysis from a 300 km 2 three dimensional seismic reflection survey over an actively growing anticline to investigate the relationship between finite shortening and surface uplift and its effects on landscape evolution a quantitative description of finite shortening of the pregrowth strata from excess area and line length calculations were compared with uplift and shortening estimates obtained from geomorphic strain markers dated using in situ 10 be cosmogenic nuclide depth profiles this combined approach provides the first estimates of quaternary surface uplift and horizontal shortening rates along the foothills of the northeastern colombian andes finite shortening for the tame anticline was calculated using two different approaches excess area shortening varies from 530 36 m 2 at its southern end decreasing northward to 404 72 m 2 whereas line length shortening is typically an order of magnitude smaller using the maximum horizontal shortening our results for the tame anticline reveal a quaternary uplift rate of 2 8 1 5 mm yr and a shortening rate of 2 1 1 2 mm yr 2 with the older terraces located at the highest elevations and recording the highest rotation from the horizontal indicating growth by limb rotation based on these rates the initiation of folding is estimated to be 0 25 0 09 0 05 ma 2 we hypothesize that the discrepancy between shortening estimates from line length and excess area calculations can be reconciled by accounting for internal deformation likely developed during the initial stages of folding which can be represented by strain hardening for example the shortening rates we obtain are comparable to geodetically derived shortening rates but are slightly lower than long term geologic shortening rates slower shortening rates and the presence of a youthful structure at the thrust front suggest that the orogen has been migrating eastward since the late pleistocene probably due to reorganization of a supercritical thrust wedge farther west in the hinterland to attain critical taper

the toba caldera complex abstract the toba caldera in indonesia is one of the most remarkable volcanic features formed during quaternary geologic time its rich history of research for over a century has yielded important information on the physical volcanology of silicic calderas and super eruptions geochemical evolution of silicic magma bodies and geophysical imaging of active sub volcanic systems during the past 1 3 my the toba area has erupted intermediate composition lavas followed by intermediate pyroclastics three quartz bearing silicic tuffs and most recently intermediate to silicic lavas this pattern represents the incremental assembly and periodic eruption of a crustal magma body of batholithic proportions the apparent migration of activity to the west may have implications for the next toba super eruption

lake toba volcano magma chamber imaged by ambient seismic noise tomography 1 for the first time ambient noise tomography is used to clearly image the magma chamber beneath lake toba caldera one of the largest quaternary calderas on earth using data from 40 seismic stations deployed between may and october 2008 around lake toba empirical green s functions are extracted from long term cross correlations of continuous records these functions are dominated by rayleigh waves whose group velocities can be measured in the period range from 2 5 to 12 seconds arrival times of these waves are picked for a given period and inverted using 2 d tomography to calculate lateral variations in velocity for the given period this was done for six different periods which all correspond to different sampling depths thus the six 2 d models presented together provide information on velocity variations with depth the results show a low velocity body coincident with the lake toba caldera representing the magma chamber under the volcano the chamber is observed to have a complex 3 d geometry with at least two separate sub chambers underlying the caldera other results include a deep low velocity body possibly another magma chamber south west of the lake with an upper limit of 7 km depth the maximum depth to which this body reaches could not be resolved the sumatra fault marks a velocity contrast but only down to depths not greater than 5 km the reliability of the results was further confirmed by checkerboard recovery tests

interpretation of recent crustal movementsbouguer gravity map of indonesia a bouguer gravity map of indonesia on mercator projection at a scale of 1 5 000 000 and with a contour interval 20 mgal has been prepared over the past few years as part of a joint research program of the geological survey of indonesia and the university of new england armidale a new base station network was set up throughout indonesia and tied to the igsn stations at sydney and singapore a discussion of the gravity features and the tectonic implications are given the map is obtainable in folded form only from the publications department university of new england armidale n s w australia 2351 for a 5 plus postage

thermoluminescence dating of sediments abstract the potential for using the thermoluminescence behaviour of sediments for dating them was first recognized by soviet scientists g v morozov and v n shelkoplyas and for over a decade their tl dates obtained from a variety of sediments have appeared in the soviet literature since 1977 tl sediment dates have been published by six additional groups using a variety of methods in this review we describe the principles of tl dating the various methods used and contrast tl dating of sediments with the now well accepted tl dating of pottery we conclude that while tl dating has the potential to solve many sedimentary problems more fundamental research needs to be carried out before such dates should be accepted a set of criteria for acceptable dates is proposed

distribution of magma beneath the toba caldera complex north sumatra indonesia constrained by three dimensional p wave velocities seismicity and gravity data 1 we estimate the one and three dimensional p wave velocity structure beneath the toba caldera complex a 30 100 km topographic depression in north sumatra using arrival time data of local earthquakes recorded by a 40 station seismic network that operated for 4 months inversions reveal the presence of p velocities up to 37 below normal that likely map the distribution of magma within this subduction related volcanic system considered the world s largest in the upper 10 km of crust the largest low velocity region underlies the southern two thirds of the depression and coincides with a gravity low centered over the resurgent dome a smaller volume of low velocities is observed in the upper crust under the north end of the depression separating the two regions is a zone of locally high velocities indicating that the shallow subcaldera magma system is composed of two separate reservoirs not a single one that extends the entire length of the caldera complex above each low velocity region is a postcollapse volcano that erupted mostly mafic lavas after the last major caldera collapse 74 kyr ago a low velocity column below one of these volcanoes can be traced into the uppermost mantle and corresponds with a planar distribution of low frequency earthquakes in the 20 to 40 km depth range the low frequency earthquakes apparently record the migration of melt in the mafic roots of this large volume crustal magma system

quantification of fluvial incision in the duero basin nw iberia from longitudinal profile analysis and terrestrial cosmogenic nuclide concentrations the duero basin is one of the largest cenozoic basins in iberia and contains a relatively well preserved sedimentary infill the top of the sedimentary sequence crops out at elevations up to 900 m above sea level the present day basin drains to the atlantic ocean via the duero river through the arribes gorge but during the cenozoic the basin experienced a long endorheic period marked by the formation of evaporites the time the basin opened to the atlantic ocean and the formation of the modern duero river drainage system remains poorly constrained in this study we quantify the spatial distribution of river incision within bedrock and sedimentary units by comparing the nearly relict higher reaches with the lower deeply incised reaches of the tributary system results show an abrupt increase in stream incision westward reaching a minimum bedrock incision depth of 600 m in the arribes gorge using cosmogenic 10be and 21ne data we estimate exposure ages for erosion surfaces at various levels in the incised duero river the cosmogenic nuclide dataset suggests that the final 2 300 m of fluvial incision in the arribes gorge occurred at a rate of 2 3 mm yr over the last 100 ka

marine transgressions on the pleistocene pecangan formation in the sangiran area central java indonesia abstract sangiran in central jawa indonesia is very famous for the occurrence of the fossil bones of pithecanthropus erectus the pleistocene sediment at sangiran area is divided into two formations kabuh formation of volcanic material and pecangan formation of mainly clays with some diatomites thin volcanic ashes and thick pyroclastic flow deposits about a hundred samples were taken from muddy beds of the pecangan formation for paleomagnetic measurements diatom analysis and electric conductivity measurement nineteeen of them contain fossil diatoms as the results of diatom analysis and electric conductivity measurements four marine transgressions are found in the pecangan formation the first major transgression took place after the olduvai event and the next one just before the jaramillo event the latter can be correlated with that of the ma0 marine clay bed in the osaka area in japan the results of the work indicate that the age of the marine transgression in the east pacific areas reflects the glacial eustasy

climatically controlled river terrace staircases a worldwide quaternary phenomenon a comparison of fluvial terrace sequences from around the world based on data collected as part of international geoscience programme igcp project no 449 has revealed significant patterns river terraces provide important records of uplift which is essential for their formation and of landscape evolution their cyclic formation however almost invariably seems to have been a response to climatic fluctuation sequences in the european core area of igcp 449 which has the longest and most extensive research history have been used as templates for worldwide comparison there is evidence for a global acceleration of uplift at the time of and perhaps in response to the mid pleistocene revolution when climatic fluctuation switched to 100 kyr milankovitch cycles terraces formed prior to this generally consist of wide aggradational sheets that probably each represent formation over several 41 kyr cycles subsequently river valleys became more steeply entrenched and terraces formed in response to the stronger 100 kyr climatic forcing in many cases at approximately one per cycle this paper uses the new data resource to explore differences between records in different climate zones between sequences with variable numbers of middle late pleistocene terraces and between systems in which the all important incision event has occurred in different parts of climatic cycles key records discussed include european examples from the rhine thames somme dniester dnieper don volga and aguas from asia the gediz turkey and orontes syria from north america the south platte and colorado from south africa the vaal and sundays from australia the shoalhaven and from south america the amazon paraguay and tributaries of the colorado and negro

stratigraphy of the toba tuffs and the evolution of the toba caldera complex sumatra indonesia during the past 1 2 m y a magma chamber of batholithic proportions has developed under the 100 by 30 km toba caldera complex four separate eruptions have occurred from vents within the present collapse structure which formed from eruption of the 2800 km3 youngest toba tuff ytt at 74 ka eruption of the three older toba tuffs alternated from calderas situated in northern and southern portions of the present caldera the northern caldera apparently developed upon a large andesitic stratovolcano the calderas associated with the three older tuffs are obscured by caldera collapse and resurgence resulting from eruption of the ytt samosir island and the uluan block are two sides of a single resurgent dome that has resurged since eruption of the ytt samosir island is composed of thick ytt caldera fill whereas the uluan block consists mainly of the oldest toba tuff ott in the past 74000 years lava domes have been extruded on samosir island and along the caldera s western ring fracture this part of the ring fracture is the site of the only current activity at toba updoming and fumarolic activity the toba eruptions document the growth of the laterally continuous magma body which eventually erupted the ytt repose periods between the four toba tuffs range between 0 34 and 0 43 m y and give insights into pluton emplacement and magmatic evolution at toba

brunhes epoch paleoclimates of japan and israel abstract continuous pollen diagrams for the brunhes epoch two from lake biwa japan and two from the dead sea rift israel are the basis for reconstructing paleoenvironments and paleoclimatic trends on both sides of asia east and west at approximately the same latitudes the mid 30 n the paleoclimatic curves are compared and correlated with the ocean oxygen isotope records the correlation is based on detailed and better dated climatic models obtained for both localities for the last 100 150 k y generally similar climatic trends have been observed for both sides of asia correlating to the oxygen isotope curves the glacial phases are manifested by cooler and more humid periods the interglacials by a temperate climate in japan and a warm dry climate in israel local climatic responses to global cooling or warming differ in japan and israel and peaks of the oxygen isotope curves may appear amplified or reduced in any of the regions the climatic responses to global processes differ from japan to israel in terms of amplitude but not the style of changes the causes for these differences in amplitude may lie with either the different local conditions japan being mainly controlled by the ocean while israel is strongly influenced by the sahara or differences in the global distribution of ice through the ages not recorded in the oxygen isotopes as long as the ice volume remains constant

radiometric ages and paleomagnetism of the sigura gura formation upper part of the toba tuffs in sumatra indonesia abstract a radiometric age determination by means of k ar and fission track method was carried out on the sigura gura formation upper part of the toba tuffs in sumatra indonesia the results are as follows 1 k ar age 0 96 0 15 ma 2 fission track ages by re etched method of external crystal surface are 1 11 0 12 and 1 11 0 14 ma 3 fission track ages by external detector method of crystal surface are 0 87 0 09 and 0 86 0 10 ma 4 the paleomagnetic polarity of the sigura gura formation is reversed so this reversed polarity surely belongs to the matuyama reversed epoch though it was previously correlated with the blake event in the brunhes normal epoch 5 the ash flow deposit which was the uppermost part of the sigura gura formation shows the youngest fission track age 0 03 0 01 ma in previous and this works so this must be a different unit called the porsea formation which overlies the sigura gura formation 6 the porsea formation may be a product of the same volcanic activity which erupted the toba ash layer identified in the deep sea sediments at about 0 075 ma ago 7 in addition six fission track age values were obtained from the younger toba tuffs of toba volcanic complex they are dated at 0 62 0 1 ma

active tectonics of peru heterogeneous interseismic coupling along the nazca megathrust rigid motion of the peruvian sliver and subandean shortening accommodation over 100 gps sites measured in 2008 2013 in peru provide new insights into the present day crustal deformation of the 2200 km long peruvian margin this margin is squeezed between the eastward subduction of the oceanic nazca plate at the south america trench axis and the westward continental subduction of the south american plate beneath the eastern cordillera and subandean orogenic wedge continental active faults and gps data reveal the rigid motion of a peruvian forearc sliver that extends from the oceanic trench axis to the western eastern cordilleras boundary and moves southeastward at 4 5 mm yr relative to a stable south america reference frame gps data indicate that the subandean shortening increases southward by 2 to 4 mm yr in a peruvian sliver reference frame the residual gps data indicate that the interseismic coupling along the nazca megathrust is highly heterogeneous coupling in northern peru is shallow and coincides with the site of previous moderate sized and shallow tsunami earthquakes deep coupling occurs in central and southern peru where repeated large and great megathrust earthquakes have occurred the strong correlation between highly coupled areas and large ruptures suggests that seismic asperities are persistent features of the megathrust creeping segments appear at the extremities of great ruptures and where oceanic fracture zones and ridges enter the subduction zone suggesting that these subducting structures play a major role in the seismic segmentation of the peruvian margin in central peru we estimate a recurrence time of 305 40 years to reproduce the great 1746 mw 8 8 lima callao earthquake

milankovitch scale multi proxy records from fluvial sediments of the last 2 6 ma pannonian basin hungary abstract the continuous cores of two nearly 500 m deep boreholes cutting pleistocene fluvial sequences in the eastern part of the pannonian basin hungary have been studied magnetostratigraphy indicates that the sediment sequences span the last 2 6 ma without significant hiatuses comparison of systematic variations in magnetic susceptibility with changes in grain size distribution revealed milankovitch scale cyclicity in sedimentation of 40 and 100 kyr cyclicity which also shows a correspondence with the 18o variations of the odp 677 site comparison of pollen and gastropod paleoecological data with the magnetic susceptibility proxies suggests that climate was a major allogenic control on the cyclicity zones of high magnetic susceptibility correspond closely with sandy and coarse silty parts of the borehole successions which largely coincide with pollen and molluscs indicating a warm climate on the contrary zones with low magnetic susceptibility correspond to silts and clays and in most cases coincide with cold climate indicator pollen and molluscs heavy mineral and xrd studies revealed that magnetic susceptibility reflects the absolute amount of detrital fe oxide minerals mostly magnetite variations in the amount of magnetite are related to changes in heavy mineral content which arise primarily from changes in sediment supply to the basin by rivers the depositional model for the pleistocene fluvial sediments suggests that sediment flux increased towards the basin during interglacials due to the increased discharge and transport capacity of the rivers while a decreased sediment supply to the distal parts of the basin occurred during glacials a delay between erosion and storage of weathering products near to the source area and subsequent transportation and re deposition of sediments in the basin interior setting is an important cause of this effect

fluvial terraces as quantitative markers of late quaternary detachment folding and creeping thrust faulting in the peruvian huallaga basin abstract in the western huallaga basin located in the peruvian subandes a series of nine fluvial terraces with elevations of up to 160 m above current floodplain level fp were formed against the biabo anticline the terraces are progressively more folded with age and terrace elevation and present growth strata suggesting ongoing folding of the anticline optically and infrared stimulated luminescence osl and irsl dating of fluvial terrace sediments yielded ages of 10 8 0 7 ka for the t2 24 2 2 ka for the t4 and 46 9 ka for the t7 terrace uniform uplift rates of 2 mm a 1 for the past 46 ka were calculated terrace profiles and two new seismic profiles that cross the biabo anticline longitudinally and transversally were used to calculate shortening rates of 2 6 mm a 1 for the anticline over the past 46 ka our calculations took into account potential contributions of detachment thrusting parallel to the biabo fold and reverse tear faulting perpendicular to the fold tip as visible on the seismic sections a maximum uplift rate of 0 62 mm a 1 due to reverse thrusting of the bellavista tear fault for the past 46 ka could have contributed to the overall uplift of the bellavista terraces based on trigonometric relationships a reverse fault slip rate of 0 86 mm a 1 and an age of 137 ka were calculated for this fault in the eastern part of the huallaga basin a series of two fluvial terraces were formed with elevations of 13 15 m and 30 m fp and with osl ages of 6 9 0 7 ka for t1 and 30 2 3 1 ka for t2 the interpretation of a third new seismic profile crossing the study area in combination with field observations and trigonometric relationships shows that the terraces were formed by a complex system of oblique ramp and strike slip faulting resulting in uplift and shortening rates of 1 mm a 1 and 1 96 mm a 1 between 30 2 ka and 6 9 ka respectively and uplift and shortening rates of 2 mm a 1 and 3 70 mm a 1 from 6 9 ka until the present reverse slip of the shapaja oblique ramp that was responsible for uplift of the terraces was calculated at 2 19 mm a 1 for the period 30 2 to 6 9 ka and 4 15 mm a 1 from 6 9 ka until the present measured total slip in combination with the calculated slip rates allowed an age calculation of 181 ka for the shapaja thrust ramp our inferences showed that the studied tectonic structures absorb most of the present day deformation in the huallaga basin the calculated uplift and shortening rates are compatible with published present day crustal movement velocities and miocene to present shortening rates for various studied sites of the tropical subandes and suggest that it is deforming at a relatively uniform rate the timing of sedimentation of the terrace sediments may have corresponded to periods of increased precipitation which occurred coeval with the heinrich events of the northern hemisphere terrace records similar as ours have been described for other tectonically highly active areas in the tropical subandes but not in the tectonically less active amazonian lowlands it is suggested that uplift rates of at least 1 mm a 1 are needed to preserve suborbital climate cycles as individual terraces the tropical subandes could therefore be a new key area to investigate the interactions between tectonics suborbital climate forcing and fluvial response during the late quaternary

comparison of u th paleomagnetism and cosmogenic burial methods for dating caves implications for landscape evolution studies caves are useful in landscape evolution studies because they often mark the level of previous water tables and when dated yield incision rates dating caves is problematic however because their ages are only constrained by the oldest deposits contained within which may be far younger than the cave itself we dated cave deposits in the sierra nevada using u th dating of speleothems paleomagnetic dating of fine sediment and cosmogenic 26 al 10 be burial dating of coarse sediment the sampled caves formed sequentially as the water table lowered providing an important stratigraphic test for the dating methods large discrepancies between deposit ages from similar cave levels demonstrate that even when accurately determined deposit ages can seriously underestimate the timing of cave development drip type speleothems are most prone to this minimum age bias because they can accumulate long after caves form and because the u th method is limited to 400 ka paleomagnetic dating requires correlation with the global reversal chronology and is hindered by a lack of continuous stratigraphy the fine sediment analyzed for paleomagnetism is also highly susceptible to remobilization and deposition in cave passages well above base level cosmogenic 26 al 10 be dates bedload material deposited when caves were at or very near river level and can date material as old as 5 ma in the sierra nevada speleothem u th ages and sediment burial ages from the same cave levels differ by as much as an order of magnitude these results suggest speleothem ages alone may significantly underestimate cave ages