making avo sections more robust1 when large quantities of seismic data are involved it is impossible to examine all gathers by eye for avo anomalies the standard approach is to compute for each amplitude profile at a specific time on each gather the intercept and gradient of a straight line fit to seismic amplitudes these intercepts and gradients are each plotted as a sort of seismic section an intercept section and a gradient section estimation of the intercept and gradient for a straight line fit to each amplitude profile proceeds traditionally via least squares two undesirable features can be hidden from the user by the fitting procedure namely i the effect of outlying or uncharacteristic amplitudes on the intercept and gradient estimates and ii complete breakdown of the straight line model for the amplitudes thus rendering meaningless the intercept and gradient estimates it should be remembered that least squares can always fit any sequence of numbers to any other sequence of numbers checks are needed to show that the result is meaningful it is shown that statistically robust estimation methods can greatly limit the damage done by outlying amplitudes and that a simple test on the model the runs statistic is capable of detecting breakdown of the straight line assumption it is demonstrated using two seismic data sets that these two techniques used in tandem facilitate much better quality control of avo intercept and gradient calculations

cenozoic tectonic evolution in the central andes in northern chile and west central bolivia implications for paleogeographic magmatic and mountain building evolution a review of available stratigraphic structural and magmatic evolution in northernmost chile and adjacent peru and bolivia shows that in this region 1 compression on the paleogene intra arc during the middle eocene incaic phase formed the nne ssw oriented incaic range along the present day precordillera and western cordillera and 2 post incaic tectonic conditions remained compressive until present contrasting with other regions of the andes where extensional episodes occurred during part of this time lapse a late oligocene early miocene peak of deformation caused further uplift the incaic range formed a pop up structure bounded by two thrusts systems of diverging vergencies it represented a major paleogeographic feature that separated two domains with different tectonic and paleogeographic evolutions and probably formed the andean water divide this range has been affected by intense erosion and was symmetrically flanked by two major basins the pampa del tamarugal and the altiplano magmatic activity remained located along the previous late cretaceous early eocene arc with slight eastward shift further compression caused westvergent thrusting and uplift along the western eastern cordillera bounding the altiplano basin to the east by another pop up shaped ridge eastward progression of deformation caused eastvergent thrusting of the eastern cordillera and subandean zone

erosional processes topographic length scales and geomorphic evolution in arid climatic environments the lluta collapse northern chile the lluta collapse of northern chile is one of the oldest recognizable landslides 2 5 ma in a hyperarid continental setting this paper develops a conceptual landscape evolution model of the lluta collapse and analyzes the controls of mass wasting and erosion sediment transport in channels on the topographic development the data presented here imply that high relief along a topographic scarp surface fracturing elevated groundwater table during a more humid climate and an aquitard underlying permeable ignimbrites are preparatory causal factors for landsliding 2 5 ma ago a strong seismic event then possibly resulted in the displacement of ca 26 km3 of mass subsequent modification of the landslide scar occurred by backward erosion resulting in the establishment of a dendritic drainage network and the removal of an additional ca 24 km3 of material it appears that this mass was produced by mass wasting in the headwaters and exported by high concentrated debris flows in channels in addition morphometric information suggest that whereas the geometrical development of the lluta collapse has been controlled by gravitational mass wasting the rates of the development of this geomorphic unit have been limited by the export rates of mass and hence by the transport capacity of the flows

deformational styles of the eastern mediterranean ridge and surroundings from combined swath mapping and seismic reflection profiling abstract recent swath mapping and seismic reflection profiling across the eastern levantine branch of the mediterranean ridge mr in the eastern mediterranean sea illustrate a strong variability of the deformational styles that characterize this precollisional accretionary prism along a north south cross section of the mr a structural analysis based on surface mapping combined with vertical seismic reflection data reveals two main structural domains a southern outer domain consists of a series of three disconnected distinct fold belts folding affects a sedimentary cover which includes an approximately 2 km thick pliocene and quaternary wedge in this domain resting on fairly thick messinian evaporitic sequences that act as probable decollement layers the mr inner domain includes three regions showing evidences of strong internal deformations and of numerous probable mud cones and mud flows but no seismic evidence of significant underlying messinian evaporites can be detected the inner sub regions are thrusting northwards over an area made of faulted and locally uplifted acoustic basement blocks that constitute the southernmost extension of the crete continental margin acting as a continental buttress for the mr this innermost domain is itself structurally disconnected from the crete continental margin by the en echelon pliny troughs system that shows evidence of left lateral displacement altogether the different structural and sedimentary cover patterns reveal a strong contrast between both mr inner and outer domains and important lateral variations within the inner mr itself strike slip faulting seams to characterizes both areas and large scale mud accumulations potentially exist in the northern one our results support a model of imbricated accretionary prisms including at least two stages 1 a pre messinian stage during which the inner mr probably developed in response to northward subduction of the african lithosphere beneath southern europe and 2 a messinian to post messinian period during which the kinematics of the aegean anatolian microplates and the presence of thick messinian deposits became prevalent and which led to the creation of the outer mr folded wedge piling against the previous one in our interpretation the occurrence of thick messinian evaporites in this area induces important local and regional modifications of the structural pattern strike slip activities reflect partitioning related to oblique subduction and likely lateral escape of the sedimentary cover in the whole studied area

palaeo geoecological significance of pleistocene trees in the lluta valley atacama desert in the lluta valley northern chile climate is hyperarid and vegetation is restricted to the valley floors and lowermost footslopes fossil tree trunks and leaves of predominantly escallonia angustifolia however are abundant up to 15 m above the present valley floor where they are intercalated with slope deposits reflecting higher water levels in the past a total of 17 samples have been radiocarbon dated yielding ages between 38 and 15k cal a bp the youngest ages of 15 4k cal a bp are interpreted as reflecting the beginning of river incision and lowering of the valley floor impeding the further growth of trees at higher parts of the slopes the most plausible scenario for this observation is intensified river incision after 15 4k cal a bp due to increased stream power and runoff from the rio lluta headwaters in the western cordillera and altiplano corresponding to the highstand of the tauca and central andean pluvial event cape wet phase

the nature and hydrogeologic significance of mud diapirs and diatremes for accretionary systems in accretionary wedges often morphologically similar sedimentary intrusions when observed by remote geophysical means may have one of two quite different driving mechanisms and a highly variable significance for the regional hydrogeologic picture for example mud diapirs are driven by buoyancy forces that arise from bulk density contrasts in them mud and pore fluid upwell en masse and fluid migration is a related sometimes important but generally subsidiary process in contrast diatremes contain sediments fluidized during rapid fluid advection and are forcibly and directly driven by the hydrogeologic system the nature of fluid input from local and exotic source regions can therefore strongly affect sedimentary intrusive processes and vice versa this complicates the process of defining the main features of the hydrogeological systems operating in accretionary wedges focused vertical advection through steep sided piercement mud diapirs requires conduit systems otherwise flow will be diffuse and directed more horizontally out of the low permeability mud mass however where the permeability of the overburden is less than that of the diapir the whole diapir may act as a conduit apart from this special case conduits will be associated with highly anisotropic scaly fabrics that can sometimes develop in the marginal shear zone of diapirs scaly fabrics form during deformation and compaction of a mud matrix under conditions of constant or increasing effective stress however the effective stress path can be complex as it is both controlled by the relative rates of upward intrusion and burial by sedimentation and or structural thickening and the hydrogeologic system due to this it appears likely that even in a geographically related group of diapirs effective stress histories will vary widely between intrusions so that some can form advective pathways for fluids and some cannot mixed systems of behavior may also be present with local diatremes developing within diapirs above the terminations of conduit systems and rapidly expanding methane gas pockets the potentially heterogeneous near surface behavior may be why the surface manifestations of sedimentary intrusions are so variable when observed in the field diatremes can also form separately as large primary features above any structural or stratigraphic conduit that rapidly expels water or gas into the base of an unlithified sediment column when active large diatremes require enormous quantities of fluid water or gas to drive them particularly if they are long lived features and hence are a direct indication of at least an episodically vigorous hydrogeologic system

assessing the age of relief growth in the andes of northern chile magneto polarity chronologies from neogene continental sections the andes of northern chile currently experience a phase of relief rejuvenation as indicated by valleys that are 1000 m dissected into pediplains however it has been unclear when this phase of relief enhancement started this paper discusses the use of palaeomagnetic chronologies from four sections in the taracapa region northern chile to assess this age the sections are located in distal and proximal positions sediment accumulation occurred between c 22 5 and 8 7 5 ma with a hiatus that possibly spans a time interval between c 19 5 and 11 ma the magnetic polarity chronologies suggest a preferred age between 8 0 and 7 5 ma for the time when relief growth started in proximal positions however alternative correlations suggest an age of 8 5 ma in addition the palaeomagnetic data reveal no rotation of the analysed strata suggesting a minimum age of c 22 5 ma for the tectonic block rotation south of the arica deflection

landslide driven drainage network evolution in a pre steady state mountain belt finisterre mountains papua new guinea the emergence of an orogen is generally characterized by an early phase of rapid surface uplift and the concomitant evolution of montane topography leading in some cases to a steady state in which tectonic mass flux is balanced by erosion this early phase of mountain growth is exemplified in the finisterre mountains of papua new guinea a propagating growth fold whose catchments can be observed at a range of stages in their temporal evolution watersheds appear to initiate by isolated gorge incision to expand by large scale landsliding in a manner controlled by ground water seepage and to entrench by fluvial incision of landslide scars and deposits once a montane system of ridges and valleys is established only rare major landslides can modify the drainage pattern the steady state morphology of a mountain belt is therefore intimately related to its initial phase of growth

understanding caldera structure and development an overview of analogue models compared to natural calderas abstract understanding the structure and development of calderas is crucial for predicting their behaviour during periods of unrest and to plan geothermal and ore exploitation geological data including that from analysis of deeply eroded examples allow the overall surface setting of calderas to be defined whereas deep drillings and geophysical investigations provide insights on their subsurface structure collation of this information from calderas worldwide has resulted in the recent literature in five main caldera types downsag piston funnel piecemeal trapdoor being viewed as end members despite its importance such a classification does not adequately examine a the structure of calderas particularly the nature of the caldera s bounding faults and b how this is achieved including the genetic relationships among the five caldera types various sets of analogue models specifically devoted to study caldera architecture and development have been recently performed under different conditions apparatus materials scaling parameters stress conditions the first part of this study reviews these experiments which induce collapse as a result of underpressure or overpressure within the chamber analogue the experiments simulating overpressure display consistent results but the experimental depressions require an exceptional amount of doming seldom observed in nature to form therefore these experiments are not appropriate to understand the structure and formation of most natural calderas the experiments simulating underpressure reveal a consistent scenario for caldera structure and development regardless of their different boundary conditions these show that complete collapse proceeds through four main stages proportional to the amount of subsidence progressively characterized by 1 downsag 2 reverse ring fault 3 peripheral downsag 4 peripheral normal ring fault the second part of this study verifies the possibility that these latter calderas constitute a suitable analogue to nature and consists of a comprehensive comparison of the underpressure experiments to natural calderas this shows that all the experimental structures as well as their progressive development are commonly observed at natural calderas highlighting a consistency between models and nature as the shallow structure of experimental calderas corresponds to a precise architecture at depth it provides a unique key to infer the deeper structure of natural calderas recognizing diagnostic surface features within a caldera will thus allow it to be categorized within a precise structural and evolutionary context the general relationship between the evolutionary stage of a caldera and its d s diameter subsidence ratio allows such a quantification with stage 1 calderas characterized by d s 40 stage 2 by 18 the four stages adequately explain the architecture and development of the established caldera end members along a continuum where one or more end members downsag piston funnel piecemeal trapdoor may correspond to a specific stage while such a continuum is controlled by progressive subsidence specific collapse geometries will result from secondary contributory factors roof aspect ratio collapse symmetry pre existing faults these considerations allow proposing an original classification of calderas incorporating their structural and genetic features

tracking the amplitude versus offset avo by using orthogonal polynomials1 inversion for s wave velocities from the amplitude variation with offset of p wave data is far from being a standard routine in the seismic processing sequence however the need for tracking the amplitude versus offset avo occurs in several situations for example in order to estimate the zero offset amplitude to reveal areas with particular avo characteristics or to compress the avo so that it is more easily obtainable at a later stage of the seismic processing furthermore weak reflections can occasionally due to the effect of the angle dependent reflectivity have a polarity shift with offset resulting in a very poor or even vanishing stack response in such cases the reflection event has to be represented by some other property than its mean amplitude or stack value we outline how the avo of seismic data may be extracted and classified by the use of orthogonal polynomials the main advantage of this method compared to a general polynomial fit is that the avo may be classified by a unique spectrum of polynomial coefficients this is in analogy to fourier coefficients where the orthogonal basis is harmonic functions the set of orthogonal polynomials is constructed entirely from the set of offset coordinates and these polyno mials are defined only on the offset window considered compared to a fourier transform this is a major advantage since there is no effect of a limited spatial bandwidth the avo of normal moveout corrected data may be represented by a data gather where the orthogonal polynomial coefficients are given as time traces with each trace revealing a certain avo characteristic for instance the stack is proportional to the zeroth order coefficient the mean gradient is given by the firstorder coefficient while the second order coefficient indicates whether the avo increases and then decreases or vice versa

landscape response to tectonic forcing digital elevation model analysis of stream profiles in the mendocino triple junction region northern california the topographic evolution of orogens is fundamentally dictated by rates and patterns of bedrock channel incision quantitative field assessments of process based laws are needed to accurately describe landscape uplift and denudation in response to tectonics and climate we evaluate and calibrate the shear stress or similar unit stream power bedrock incision model by studying stream profiles in a tectonically active mountain range previous work on emergent marine terraces in the mendocino triple junction region of northern california provides spatial and temporal control on rock uplift rates digital elevation models and field data are used to quantify differences in landscape morphology associated with along strike northwest to southeast changes in tectonic and climatic conditions analysis of longitudinal profiles supports the hypothesis that the study area channels are in equilibrium with current uplift and climatic conditions consistent with theoretical calculations of system response time based on the shear stress model within uncertainty the profile concavity of the trunk streams is constant throughout the study area 0 43 as predicted by the model channel steepness correlates with uplift rate these data help constrain the two key unknown model parameters the coefficient of erosion k and the exponent associated with channel gradient n this analysis shows that k cannot be treated as a constant throughout the study area despite generally homogeneous substrate properties for a reasonable range of slope exponent values n best fit values of k are positively correlated with uplift rate this correlation has important implications for landscape evolution models and likely reflects dynamic adjustment of k to tectonic changes due to variations in orographic precipitation and perhaps channel width sediment load and frequency of debris flows the apparent variation in k makes a unique value of n impossible to constrain with present data

deformation of the western mediterranean ridge importance of messinian evaporitic formations abstract multichannel seismic data were acquired across several areas of the mediterranean ridge m r in the eastern mediterranean sea during the mcs prismed survey march 1993 the m r is a wide high standing and elongated swell emplaced between the southern aegean and africa as a consequence of the long term convergence and the ongoing collision between europe and africa sedimentary piling and associated deformation have built a thick deformed sediment wedge the internal geological structures of which remain poorly understood processing of two mcs lines pm 02 and pm 03 across the western branch of the mediterranean ridge reveals that messinian evaporite bearing formations which were deposited within the deep ionian oceanic basin 5 my ago play an important part in the present structural deformation of the m r accretionary wedge within the outer m r the messinian lower evaporites are believed to act as one of the main decollement levels while the top of these formations may operate as a disharmonic layer below thin plio quaternary sediments the present day m r toe appears to be affected by ductile flow deformation however most of the accreted outer wedge is believed to have resulted from the progressive piling up and associated thrusting of messinian and overlying plio quaternary sediments toward the northeast i e toward the central m r domain a major backthrust zone indicates a structural boundary between the outer wide and convex m r and its inner rather flat domain which is inferred to act as a backstop

giant landslide triggerings and paleoprecipitations in the central western andes the aricota rockslide dam south peru abstract the central part of the western andes holds an exceptional concentration of giant paleolandslides involving very large volumes of rock material v km3 while those gravitational slope failures are interpreted consensually as an erosional response to the geodynamic activity of the andes relief formation and tectonic activity the question of their triggering mechanisms remains enigmatic to clarify the respective roles of climatic versus seismic forcing on the andean landslides new temporal constraints on paleo movements are essential here we focus on one of those giant slope failures the aricota giant rockslide that damned the locumba valley in southern peru we conducted fieldwork high resolution dem analysis and cosmogenic nuclide dating to decipher its development history and failure mechanisms our results point to the occurrence of two successive events a giant failure mobilizing a rock volume of ca 2 km3 first produced a dam at 17 9 0 7 ka considering its height of ca 600 m the aricota rockslide dam is one of the three largest landslide dams worldwide at 12 1 0 2 ka a second event produced ca 0 2 km3 of material and the rock avalanche debris spread out over the dam as the chronology of those two events is pointing to the two main paleoclimatic pluvial periods in this region heinrich stadial 1a and younger dryas we favor the interpretation of a climatic forcing at a regional scale the concomitant aggradation of alluvial terraces and fan systems along the nearby valleys highlights higher regional erosion sediments supply and mass wasting events during those paleoprecipitation events and strengthens this conclusion

fault related folding drainage network evolution and valley incision during the neogene in the andean precordillera of northern chile abstract we describe neogene drainage network development before during and after regional folding in the precordillera of the andes of northern chile 18 19 s the drainage network developed on an extensive regular erosional surface formed on oligocene miocene ignimbrites oxaya formation the folding affecting the rocks of the precordillera is represented by the oxaya anticline oa which trends n to nw is 50 km long and 30 km wide the fold is gentle west vergent and has resulted in an uplift of the hinge zone by up to 850 m it formed by the propagation on its western border of a subvertical east dipping blind reverse fault ausipar fault af the folding occurred in the middle late miocene essentially between 11 7 0 7 and 10 7 0 3 ma its maximum duration was 2 my two phases of drainage development are recognised in the precordillera an initial lower middle miocene 19 12 ma parallel drainage network is well preserved and synchronous with fluvial and lacustrine sedimentation in the central depression the network was poorly structured and attained maximum incision of to 250 50 m the minimum long term rate of incision was 36 7 m my folding generated the progressive abandonment and fossilisation of the initial parallel drainage network which became trellissed and concentrated in a few deeply incised valleys in the anticline hinge the lluta and azapa main valleys present a total incision of 1650 50 and 1605 50 m respectively whereas the cardones valley presents 595 50 m during folding river incision at the fold hinge was equal to or greater than the amplitude of the folding which is 790 50 m in the lluta valley and 715 50 m in the azapa valley consequently the long term rate of synfolding incision was much greater than 395 25 lluta valley and 358 25 m my azapa valley the cardones valley was fossilised approximately in the middle of the folding after folding 11 to 0 ma the incision in the lluta and azapa rivers was 610 100 and 640 100 m and with a rate of 56 9 and 58 9 m my respectively the postfolding incision rate is approximately twice than of the prefolding incision rate this implies an acceleration of valley incision since the late miocene which is considered as consequence of regional uplift of the andean forearc

the structure and formation of mud volcano summit calderas circular depressions bounded by inward dipping faults found at the upper terminations of large mud volcano systems 500 m diameter are termed mud volcano summit calderas from new mapping and comparison with previously identified examples we describe a series of common structural and morphological features found at a number of calderas and propose a mechanism for caldera formation a typical example consists of concentric deformational and volcanic zones including an outermost topographic rim inward dipping circular fault system moat and raised central pedestal of freshly extruded mud volcanic sediment this distinctive moat and pedestal morphology can be explained in terms of the quantity and rheology of extruded mud and appears characteristic of calderas from the south caspian basin and elsewhere the association of fresh mud volcanic deposits with the calderas in combination with extensive literature on caldera modelling leads us to conclude that the most likely causal mechanism is subsidence as a result of evacuation of fluids and sediment from shallow structural levels during eruptions summit calderas mapped in this study characterize dormant periods of mud volcanism in subaerial and submarine settings and appear to be a common structural element in the extrusive domain of mud volcano systems

age variation in the source of the diapiric mud breccia along and across the axis of the mediterranean ridge accretionary complex abstract pleistocene or younger mud diapirism is recorded along the arcuated crest of the mediterranean ridge accretionary complex over a distance of more than 450 km the extruded mud supported breccia named mud breccia is poorly fossiliferous but the matrix may be dated as late aptian to albian and late burdigalian to langhian in age based on the calcareous plankton content calcareous nannofossils and planktonic foraminifera diagnostic of other ages are sparse within the two above mentioned major assemblages they indicate the presence of sediments attributable 1 to the santonian and cenomanian which occur in association with the mid cretaceous assemblages toronto unnamed and aros domes and 2 to the serravallian which occur in association with the late burdigalian langhian assemblages in the gelendzhik dome aptian albian to late cretaceous sediments are pelagic in origin and are similar to the scisti a fucoidi and scaglia rossa formations well known from continental italy mixed dolomitic clasts and crystals also occur within the matrix indicating the presence of portions of the evaporitic sequence of messinian age in four cores from the western locations single very rare plankton specimens indicative of other ages different from those mentioned above also occur within the matrix at various places they are interpreted as reworked primarily within the late burdigalian langhian sediments the age of the emplacement of the breccia should be older than the middle pleistocene as supported by the occurrence of clasts of this age in the mud breccia and is still an ongoing process at least in the napoli dome

hydrocarbons in washington coastal sediments the sources and distributions of polycyclic aromatic hydrocarbons pah and aliphatic hydrocarbons are characterized in seventeen sediments from a highly river influenced sedimentary environment off the southwestern coast of washington the major hydrocarbons are land derived introduced as preformed compounds and display long term stability in sediment cores a series of pah of anthropogenic origin and two naturally derived compounds retene and perylene dominate the pah composition in these sediments plantwax n alkanes are the major aliphatic hydrocarbon constituents aliphatic hydrocarbons of marine origin pristane and a series of four acyclic multibranched c25 polyolefins are also observed in many sediments the concentrations of these marine derived hydrocarbons decrease to negligible levels rapidly with sediment depth from the sea sediment interface suggesting degradation in general the major land derived hydrocarbons are concentrated in the midshelf silt deposit which extends northwestward along the continental shelf from the columbia river mouth a quantitatively more minor natural series of phenanthrene homologs also of terrestrial origin is preferentially advected further offshore and deposited in continental slope sediments these distributions are consistent with recognized particle associations for these compounds and sediment dispersal processes in this coastal environment sediment core records suggest the present pattern of dispersal has persisted for at least the past century and possibly since the late pleistocene

origin and development of theater headed valleys in the atacama desert northern chile morphological analogs to martian valley networks abstract understanding planetary landforms including the theater headed valleys box canyons of mars usually depends on interpreting geological processes from remote sensing data without ground based corroboration here we investigate the origin and development of two mars analog theater headed valleys in the hyperarid atacama desert of northern chile previous workers attributed these valleys to groundwater sapping based on remote imaging topography and publications on the local geology we evaluate groundwater sapping and alternative hypotheses using field observations of characteristic features strength measurements of strata exposed in headscarps and estimates of ephemeral flood discharges within the valleys the headscarps lack evidence of recent or active seepage weathering such as spring discharge salt weathering alcoves or vegetation their welded tuff caprocks have compressive strengths multiple times those of the underlying epiclastic strata flood discharge estimates of cubic meters to tens of cubic meters per second derived using the manning equation are consistent with the size of transported clasts and show that the ephemeral streams are geomorphically effective even in the modern hyperarid climate we interpret that headscarp retreat in the quebrada de quisma is due to ephemeral flood erosion of weak miocene epiclastic strata beneath a strong welded tuff with erosion of the tuff facilitated by vertical jointing the quebrada de humayani headscarp is interpreted as the scar of a giant landslide maintained against substantial later degradation by similar strong over weak stratigraphy this work suggests that theater headed valleys on earth and mars should not be attributed by default to groundwater sapping as other processes with lithologic and structural influences can form theater headscarps

gigantic low gradient landslides in the northern periphery of the crimean mountains ukraine abstract large scale low gradient ancient landslides estimated at 5 4 18 9 km 2 in area and 0 2 1 2 km 3 in volume have been studied in the northern hilly periphery of the crimean mountains ukraine they originated on slopes along wide water gaps of rivers belbek kacha alma and biyuk karasu crossing the cuestas of the northern foothills the slopes generally consist of slightly northward tilting miocene mainly sarmatian limestones overlying weak clay rich lower neogene palaeogene substratum with a significant content of smectite although the region is characterised by the least active contemporary morphodynamics within the crimean mountains the landslides which were studied are of the same size or even larger than various types of landslides occupying active geomorphic domains of the highest mountain range in the southernmost part of the peninsula the landslides are generally a spreading type but the sliding mechanics were probably very complex involving toppling rotational slides gravitational folding and translational block slides all the landslides which were studied are located in the vicinity of regional faults and three of them have headscarps aligned along faults a common feature is also a location close within several km to the mesozoic suture zone which is the most important tectonic feature in the northern periphery of the crimean orogene this suture was formerly classified as aseismic however evidence of strong low frequency palaeoearthquakes was collected during the last decade within both the mesozoic suture and the low lying northern part of the crimean peninsula radiocarbon dating of deposits associated with the landslides has revealed at least two phases of increased landslide activity during the late glacial chronozone and holocene epoch the main landslide phase presumably took place at some time between the late glacial and atlantic chronozones minor reactivation of landslide toes occurred during the subatlantic chronozone and some of them have been active up to recent times the first major landslide phase was possibly triggered by an earthquake whereas late holocene activity can be attributed both to seismic and hydroclimatic factors

giant landslides in the foreland of the patagonian ice sheet abstract quaternary glaciations have repeatedly shaped large tracts of the andean foreland its spectacular large glacial lakes staircases of moraine ridges and extensive outwash plains have inspired generations of scientists to reconstruct the processes magnitude and timing of ice build up and decay at the mountain front surprisingly few of these studies noticed many dozens of giant 108 m3 mass wasting deposits in the foreland we report some of the world s largest terrestrial landslides in the eastern piedmont of the patagonian ice sheet pis along the traces of the former lago buenos aires and lago puyerredon glacier lobes and lakes more than 283 large rotational slides and lateral spreads followed by debris slides earthflows rotational and translational rockslides complex slides and few large rock avalanches detached some 164 56 km3 of material from the slopes of volcanic mesetas lake bounding moraines and river gorge walls many of these landslide deposits intersect with well dated moraine ridges or former glacial lake shorelines and offer opportunities for relative dating of slope failure we estimate that 60 of the landslide volume 96 km3 detached after the last glacial maximum lgm giant slope failures cross cutting shorelines of a large late glacial to early holocene lake glacial lake pis likely occurred during successive lake level drop between 11 5 and 8 ka and some of them are the largest hitherto documented landslides in moraines we conclude that 1 large portions of terminal moraines can fail catastrophically several thousand years after emplacement 2 slopes formed by weak bedrock or unconsolidated glacial deposits bordering glacial lakes can release extremely large landslides and 3 landslides still occur in the piedmont particularly along postglacial gorges cut in response to falling lake levels

mud volcanoes the most important pathway for degassing deeply buried sediments abstract this paper discusses the nature of the phenomenon of mud volcanism with respect to degassing of deeply buried sediments mud volcanoes are defined as geological structures and their main elements are described based on the nature of activity mud volcanoes are grouped in to three main types and the relationship between each type and corresponding morphological expression is discussed the presented up to date data of the world geographical distribution of mud volcanoes show that they approximate to 1800 individuals a detail overview of geological environments in which they occur helps to deduce some necessary conditions for mud volcano formation the basic mechanisms of mud volcano formation are discussed specifically the fluid pressure hypothesis and some triggering events are identified the most common investigation approach and some criteria for recognizing of a submarine mud volcano on side scan sonar records and seismic sections are given mud volcanism in the mediterranean ridge an accretionary complex and black sea abyssal plane a back ark basin with tectonic regime of extension are described as case studies to show variety in morphology and common factors in development of mud volcanoes the manifestation of continuous gas migration through mud volcanoes is clarified and the attempt made to quantify the gas release shows that mud volcanoes are one of the significant natural sources of atmospheric methane emitting a total amount of about 10 3 to 12 6 tg annually

uplift of the central andean plateau and bending of the bolivian orocline the topography of the central andes can be considered the primary tectonic signal of late cenozoic mountain building in an arid region where the effects of uplift and magmatism are little obscured by denudation the spatial coverage of the topographic signal is more complete than that for sparsely sampled geological and geophysical data a color coded image of digitized topography between 12 s and 37 s highlights the altiplano puna one of the world s most remarkable plateaus and reveals important physiographic clues about the formation of that major feature the topographic data combined with information on structure magmatism seismicity and paleomagnetism support a simple kinematical model for the late cenozoic evolution of the central andes the model does not require collisional effects or enormous volumes of intrusive additions to the crust but instead calls upon plausible amounts of crustal shortening and lithospheric thinning the model interrelates andean uplift a changing geometry of the subducted nazca plate and a changing outline in map view of the leading edge of the south american plate crustal shortening has accommodated convergence between the chilean peruvian forearc and the south american foreland the altiplano puna plateau can be constructed by a combination of crustal shortening and thickening and lithospheric thinning above a shallow dipping 20 30 subducted plate the seawardly concave bend of western south america the bolivian orocline was enhanced but not completely produced by an along strike variation in the amount of late cenozoic shortening maximum shortening in bolivia both produced the widest part of the plateau and increased the seaward concavity of the bolivian orocline the along strike variations of shortening are hypothesized to result from corresponding along strike variations in the width of a weakened zone in the overriding plate weakening occurs above the wedge of asthenosphere located between the subducted and overriding plates hence the width of the zone of weakening depends upon the dip of the subducted plate two types of shortening are recognized 1 a widespread basin and range laramide like shortening that characterizes modem activity in the sierras pampeanas and late miocene deformation of the altiplano puna and 2 on the eastern side of the cordilleras and plateau an east verging foreland fold thrust belt in which the underthrust foreland compresses and thickens the ductile lower crust and produces a plateau uplift of the upper crust the second type of shortening can be applied to plio quaternary deformations throughout the central andes but with a substantial narrowing of the region of plateau uplift in peru and south of 28 s a proposed monoclinal flexure of the upper crust on the western side of the plateau uplift explains the remarkably simple and regular morphology of the main western slope of the central andes the monocline is located above the tip of the asthenospheric wedge between the converging plates it is postulated to occur above the western limit of lower crustal thickening in the regions of horizontal subduction the monocline can be associated with a late miocene asthenospheric wedge tip

alkane and pah biomarkers as tracers of terrigenous organic carbon in arctic ocean sediments abstract we present the first sedimentary biomarker study encompassing the entire arctic ocean a large data set of organic markers for terrigenous petroleum and combustion inputs alkanes hopanes and steranes parent and alkyl polycyclic aromatic hydrocarbons pahs is examined for patterns in space and time using principal components analysis pca and partial least squares pls biomarker patterns reveal the central arctic ocean basin sediments to be compositionally distinct from those of the mackenzie river beaufort sea and barents sea but similar to those of the laptev sea pah distributions reflected in pah ratios and pca projections demonstrate that arctic ocean sediment is dominated by natural inputs to the extent that anthropogenic combustion pahs are not significant we find only modest changes between the glacial and post glacial sediments for atmospherically transported hydrocarbon biomarkers while particle associated biomarkers were captured strongly at basin edges during the glacial period and much more evenly transported across basins during the post glacial period the orders of magnitude decreases in particle associated petrogenic alkanes and pahs in central basins during glacial times coupled with the uniformity of most petrogenic biomarker parameters for most basin and shelf locations reflect a massive reduction in ice transport that makes the margins the most likely source of petrogenic material for the pleistocene holocene central arctic basins the proximity of large coal deposits of various maturity levels along the lena river the overlap in pah and biomarker composition of the laptev sea and surficial sediments from the central arctic ocean and the location of the laptev sea at the origin of the main transpolar drift all point to eroded coals from the lena river laptev sea as the likely source of petrogenic hydrocarbons to the central arctic ocean the ubiquitous presence of allochthonous coal in arctic ocean surface sediments provides a major constraint on the use of petrogenic biomarkers to infer the presence of subsurface petroleum reserves

submersible study of mud volcanoes seaward of the barbados accretionary wedge sedimentology structure and rheology abstract in 1992 the nautile went to a mud volcano field located east of the barbados accretionary wedge near 13 50n using nannofossil analysis on cores we determined the sedimentation rate and provided a new estimation of the age of the mud volcanoes 750 000 years for the oldest one six structures have been explored with the submersible nautile and manifestations of fluid venting chimneys carbonate cementation and chemosynthetic communities were observed on all sedimentological analysis identifies two sources of diapiric mud most mud volcanoes expel mud containing late miocene to quaternary faunae that have the same composition as sediments drilled above the barbados wedge decollement one volcano also contains older oligocene taxa with a mud composition corresponding to the sedimentary sequence below the decollement we use diving observations to map the fine scale morphology the distribution of chemosynthetic fauna and define two end member types of structures mud pies flat topped mud volcanoes and conical mounds mud pies atalante and cyclops are characterised by the presence of a lake of highporosity mud 70 to 75 in their central parts chemosynthetic benthic communities calyptogena colonies and sponge bushes are concentrated in the outer parts contrasting morphologies of the two mud pies indicate different stages of activity cyclops is growing whereas atalante is collapsing expulsion of water and methane occurs mostly through the mud lake and may be stronger during the collapse phase on conical mounds there are no mud lakes fluid venting concentrates near the summit and occurs through carbonate cemented chimneys which form within the sediment viscosity measurements have been carried out on mud samples from the two mud pies and one conical mound all mud samples have a plastic fluid behaviour the plastic threshold decreases with porosity and thixotropy is observed for a porosity of more than 70 an analogue experiment shows that for this thixotropic mud shearing in the feeding conduit liquefies the mud which then spreads to form a mud pie conical mounds form when the mud remains plastic we show that the dissociation of methane hydrate is the cause of the high porosity in mud pies and confirm that these structures are a consequence of large scale dissociation of methane hydrate at the base of its stability field dissociation of hydrates before and during ascent is only slightly contributing to the pore fluid in conical mounds but solid hydrates still present in the mud may contribute to its buoyancy

channel initiation and the problem of landscape scale since the 1940s it has been proposed that landscape dissection into distinct valleys is limited by a threshold of channelization that sets a finite scale to the landscape this threshold is equal to the hillslope length that is just shorter than that necessary to support a channel head a field study supports this hypothesis by showing that an empirically defined topographic threshold associated with channel head locations also defines the border between essentially smooth undissected hillslopes and the valley bottoms to which they drain this finding contradicts assertions that landscapes are scale independent and suggests that landscape response to changes in climate or land use depends on the corresponding changes in the threshold of channelization

mud volcanism on the mediterranean ridge initial results of ocean drilling program leg 160 drilling during ocean drilling program leg 160 april may 1995 revealed important new evidence concerning the internal composition depositional processes and age of two mud volcanoes within the mediterranean ridge accretionary complex holes were drilled at ca 2000 m water depth on the crest areas across the flanks of the mud volcanoes and onto adjacent deep sea sediments the main depositional units forming the flanks of both mud volcanoes are debris flows mud breccias composed of a volumetrically dominant mud matrix containing clasts of mainly clay mudstone siltstone sandstone and limestone more variable muddy silty and sandy sediments were recovered from the crestal areas of both volcanoes the lowest mud volcano units drilled include well sorted medium to coarse grained sediments mainly composed of clay that were deposited partly by turbidity currents the mud volcano sediments are associated with background deep sea sediments that allow dating by using microfossils the milano mud volcano is at least 1 75 ma and is apparently now dormant and the napoli mud volcano started prior to or during 1 5 1 2 ma and is currently active pore fluids at napoli and to a lesser extent at milano indicate the presence of halite of presumed latest miocene age beneath the volcanoes hydrocarbon gas is venting from the crest of the napoli mud volcano and gas was also detected on the crest of the milano mud volcano methane hydrates clathrates are also inferred to exist beneath the crest of the milano mud volcano the mud volcanoes are located above a shallowly dipping subduction zone in an area where the accretionary complex is apparently being thrust northward over a backstop of continental crust related to initial collision of the african and eurasian plates mud volcanism may have begun when backthrusting punctured a seal of latest miocene evaporites allowing the escape of overpressured materials

possible flexural accommodation on the eastern edge of the altiplano in relation to focussed erosion in the rio la paz drainage system it has been proposed that erosional unloading by focused incision can be accommodated by flexural rebound which in turn potentially exerts a positive feedback on erosion this paper presents morphometric data from the la paz drainage basin in the bolivian andes to illustrate the effects of such a feedback mechanism between erosion and crustal bending the rio la paz is a prominent system with the headwaters on the altiplano and a trunk stream segment that cuts across the cordillera real thereby connecting large portions of the altiplano with the amazon basin the flexural feedback model explains why all drainages beyond the watershed disperse their waters to the altiplano it also provides an explanation for the presence of the highest peaks just next to the location where the la paz river cuts into the bedrock across the cordillera real

cyclic activity of mud volcanoes evidences from trinidad se caribbean fluid and solid transfer in mud volcanoes show different cyclic phases of activity including catastrophic events and periods of relative quiescence characterized by moderate activity this is notably well shown by the compilation of historical data onshore trinidad it appears that each eruptive mud volcano has its own period of catastrophic activity and this period is variable from one volcano to another the frequency of the eruptions seems essentially controlled by local pressure regime within the sedimentary pile the dynamics of expulsion of the mud volcanoes during the quiescent phases has been studied with the help of temperature measurements within the mud conduits the mud temperature in these conduits is notably concurrently controlled by the gas flux endothermic gas depressurizing induces a cooling effect and by the mud flux mud is a vector for convective heat transfer complex temperature distribution was observed in large conduits and pools especially in the bigger pools the temperature distribution characterizes convective cells with an upward displacement of mud above the deep outlet and ring shaped rolls associated with the burial of the mud on the flanks of the pools in tube like shaped narrow conduits the temperature is more regular but we observed different types of profiles with either downward increasing or decreasing temperatures near constant to even negative gradients compared to the general temperature gradient are typical for very dynamic fluid systems the temperature profiles varied from one place to another as well as over time the temperatures measured within the conduits and their base show that the fluid flow is not constant but highly variable through short time periods we observed locally a significant daily change of the temperature of the expelled mud which shows also that the mud flux is changing very rapidly due to the migration dynamics of the mud in fracture systems we also observed very short time period cyclic variations with a frequency of several minutes these high frequencies temperature changes could be related to the dynamics of two phase flows gas and mud through the mud volcano conduits

14c activity and global carbon cycle changes over the past 50 000 years a series of 14c measurements in ocean drilling program cores from the tropical cariaco basin which have been correlated to the annual layer counted chronology for the greenland ice sheet project 2 gisp2 ice core provides a high resolution calibration of the radiocarbon time scale back to 50 000 years before the present independent radiometric dating of events correlated to gisp2 suggests that the calibration is accurate reconstructed 14c activities varied substantially during the last glacial period including sharp peaks synchronous with the laschamp and mono lake geomagnetic field intensity minimal and cosmogenic nuclide peaks in ice cores and marine sediments simulations with a geochemical box model suggest that much of the variability can be explained by geomagnetically modulated changes in 14c production rate together with plausible changes in deep ocean ventilation and the global carbon cycle during glaciation

terrestrial methane seeps and mud volcanoes a global perspective of gas origin abstract a global database of gas composition and methane stable isotopes of 143 terrestrial mud volcanoes from 12 countries and 60 seeps independent from mud volcanism from eight countries was compiled and examined in order to provide the first worldwide statistics on the origin of methane seeping at the earth s surface sixteen seep data were coupled with their associated subsurface reservoirs the surface seepage data indicate that at least 76 of the mud volcanoes release thermogenic gas with only 4 biogenic and 20 with mixed character the average 201 data of methane concentration and methane carbon isotope ratios 13 c 1 of mud volcanoes are 90 v v and 46 4 respectively the other types of seeps which are independent from mud volcanism have an average 13 c 1 value that is slightly higher 42 9 gases from mud volcanoes are generally lighter more methane less ethane and propane than their associated reservoir gases suggesting a molecular fractionation during advective fluid migration other types of seeps especially dry seeps maintain the reservoir c 1 c 2 c 3 bernard ratio mud volcanoes behave like a natural refinery and the origin of gas more isotopically enriched than 50 and with c 1 c 2 c 3 500 should be attributed to a thermogenic source rather than partial oxidation of biogenic gas some data that appear biogenic in the bernard diagram can be explained by molecular fractionation of mixed gas consequently the bernard parameter may be misleading when applied to mud volcanoes since it does not always reflect the original gas composition the mechanisms of the molecular advective segregation should be studied quantitatively by specific models and experiments

assessment of the eruptive activity and identification of the mud breccia s source in the olimpi mud volcano field eastern mediterranean abstract even though the intensity and frequency of the eruptive episodes of deep sea mud volcanoes mvs substantially regulate the methane fluxes into the hydrosphere and the development of the near seafloor sulfate zone that affects the position of the gas hydrate stability zone these factors are not yet adequately investigated moreover the evaluation of the eruptive sediment s thermal maturity may provide solid documentation of the petroleum generation potential in high depths below seafloor bsf hence the present study through the integration of sedimentary facies analysis with hydrocarbon biomarker analysis based on the concentrations of long chain c25 c35 n alkanes hopanes and steranes supported by swath bathymetry data examined five sediment cores recovered from the gelendzhik moscow milano leipzig and heraklion mvs of the olimpi mud volcano field omvf on the central mediterranean ridge the main objective of this investigation was to assess the modern eruptive activity in the omvf and identify the mud breccia s origin and mobilization depth based on its maturity level and the ages of the source beds among the studied mvs milano leipzig and heraklion appear recently active while moscow perhaps remains in dormancy for at least one century the eruptive activity in the omvf seems to be generally vigorous and persistent while it is linked with several source beds of variable stratigraphy or environmental condition the multiple eruptive episodes occurring as uninterrupted events or via pulses create conditions that perhaps favour high releases of methane into the water column as well as the growth of the gas hydrate phase near the seafloor the identified modern mudflows appear thermally immature for oil generation while they most probably originate from terrestrial source beds located not deeper than 2 km bsf a messinian age could be suggested for the principal sources of the very soft to soft mud breccias of the omvf while stratigraphic horizons of early middle miocene might be proposed as the likely major sources for the firm to very stiff mud breccias of the area

weighted stacking for rock property estimation and detection of gas amplitude versus offset concepts can be used to generate weighted stacking schemes here called geo stack which can be used in an otherwise standard seismic data processing sequence to display information about rock properties the zoeppritz equations can be simplified and several different approximations appear in the literature they describe the variation of p wave reflection coefficients with the angle of incidence of a p wave as a function of the p wave velocities the s wave velocities and the densities above and below an interface using a smooth representative interval velocity model from boreholes or velocity analyses and assuming no dip the angle of incidence can be found as a function of time and offset by iterative ray tracing in particular the angle of incidence can be computed for each sample in a normal moveout corrected cmp gather the approximated zoeppritz equation can then be fitted to the amplitudes of all the traces at each time sample of the gather and certain rock properties can be estimated the estimation of the rock properties is achieved by the application of time and offset variant weights to the data samples before stacking the properties which can be displayed by geo stack are p wave reflectivity or true zero offset reflectivity s wave reflectivity and the reflectivity of p wave velocity divided by s wave velocity or pseudo poisson s ratio reflectivity if assumptions are made about the relation between p wave velocity and s wave velocity for water bearing clastic silicate rocks then it is possible to create a display which highlights the presence of gas

significance of mud volcanism 1 mud volcanism and diapirism have puzzled geoscientists for 2 centuries they have been described onshore and offshore in many places on earth and although they occur in various tectonic settings the majority of the features known to date are located in compressional tectonic scenarios this paper summarizes the main thrusts in mud volcano research as well as the various regions in which mud volcanism has been described mud volcanoes show variable geometry up to tens of kilometers in diameter and several hundred meters in height and a great diversity regarding the origin of the fluid and solid phases gas predominantly methane water and mud may be mobilized at subbottom depth of only a few meters but in places can originate from several kilometers depth with minor crustal or mantle input the possible contribution of mud extrusion to global budgets both from quiescent fluid emission and from the extrusive processes themselves is important in regions where mud volcanoes are abundant such as the collision zones between africa and eurasia fluid flux through mud extrusion exceeds the compaction driven pore fluid expulsion of the accretionary wedge also quiescent degassing of mud volcanoes may contribute significantly to volatile budgets and hence to greenhouse climate

mud volcanoes and gas hydrates in the anaximander mountains eastern mediterranean sea abstract detailed multibeam sedimentological and geophysical surveys provide ample new data to confirm that the anaximander mountains eastern mediterranean are an important area for active mud volcanism and gas hydrate formation more than 3000 km of multibeam track length was acquired during two recent missions and 80 gravity and box cores were recovered morphology and backscatter data of the study area have better resolution than previous surveys and very detailed morphology maps have been made of the known targeted mud volcanoes amsterdam kazan and kula especially the amsterdam crater and the related mud breccia flows gas hydrates collected repeatedly from a large area of amsterdam mud volcano at a sub bottom depth of around 0 3 1 5 m resemble compacted snow and have a rather flaky form new gas hydrate sites were found at amsterdam mud volcano including the mud flow sloping off to the south gas hydrates sampled for the first time at kazan mud volcano are dispersed throughout the core samples deeper than 0 3 m and display a rice like appearance relative chronology and ams dating of interbedded pelagic sediments late holocene hemipelagic sapropel layer s1 and ash layers within the mud flows indicate that successive eruptions of kula mud volcano have a periodicity of about 5 10 kyrs new mud volcanoes identified on the basis of multibeam backscatter intensity were sampled documented as active and named athina and thessaloniki gas hydrates were sampled also in thessaloniki mud volcano the shallowest 1264 m among all the active mediterranean sites at the boundary of the gas hydrate stability zone biostratigraphical analyses of mud breccia clasts indicated that the source of the subsurface sedimentary sequences consists of late cretaceous limestones paleocene siliciclastic rocks eocene biogenic limestones and miocene mudstones rough estimations of the total capacity of the anaximander mud volcanoes in methane gas are 2 56 6 40 km3

evolution of the west andean escarpment at 18 s n chile during the last 25 ma uplift erosion and collapse through time abstract the geological record of the western andean escarpment warp reveals episodes of uplift erosion volcanism and sedimentation the lithological sequence at 18 s comprises a thick pile of azapa conglomerates 25 19 ma an overlying series of widespread rhyodacitic oxaya ignimbrites up to 900 m thick ca 19 ma which are in turn covered by a series of mafic andesite shield volcanoes between 19 and 12 ma the surface of the oxaya ignimbrites evolved into a large monocline on the western slope of the andes a giant antithetically rotated block oxaya block 80 km 20 km formed on this slope at about 10 12 ma and resulted in an easterly dip and a reversed drainage on the block s surface morphology topography and stratigraphic observations argue for a gravitational cause of this rotation a secondary gravitational collapse 50 km3 extending 25 km to the west occurred on the steep western front of the oxaya block alluvial and fluvial sediments 11 2 7 ma accumulated in a half graben to the east of the tilted block and were later thrust over by the rocks of the escarpment wall indicating further shortening between 8 and 6 ma flatlying upper miocene sediments

structural and lithological controls on large quaternary rock avalanches sturzstroms in arid northwestern argentina landsat thematic mapper tm analysis aerial photograph interpretation and field studies of the semiarid puna plateau adjacent eastern cordillera and sierras pampeanas of argentina lat 24 28 s have revealed the existence of at least 55 rock avalanche deposits with volumes larger than 10 6 m 3 that formed by the collapse of entire mountain fronts the spatial distribution of landslide deposits is not random but it clusters along mountain fronts bounded by active faults inspection in the field reveals five principal controls on the distribution of these events the source area of the rock avalanches has two topographic constraints 1 vertical relief contrasts between the breakaway zone and the mountain front must exceed a threshold of 400 m and 2 the slope inclinations must be steeper than 20 rock avalanches are restricted to three types of lithology granites low grade metamorphic rocks and coarse clastic sediments structural controls are very important rock avalanches are controlled by planar structures such as bedding planes exfoliation joints minor faults and cleavage that all dip toward the valley in addition major slide clusters occur along mountain fronts that underwent quaternary reverse fault reactivation of former transfer faults with strike slip kinematics the trigger mechanism for the majority of these landslides is interpreted to be seismic although the ages of some major slides are about 30 ka and they may correspond to a more humid interval in southern south america

organic carbon provenance and maturity in the mud breccia from the napoli mud volcano indicators of origin and burial depth abstract mud volcanism on the mediterranean ridge is caused by extrusion of overpressured sediments with consequent formation of spectacular dome shaped features composed of mud breccias at the seafloor the organic material in the mud breccia of the napoli mud volcano is a mixture of different facies stratigraphic origin and thermal maturities one portion is synsedimentary organic material with only minor diagenetic alterations and represents sedimenting material that was embedded into the mud volcano during its extrusion the mud breccia also contains thermally mature organic material of mainly terrestrial provenance with algae of fresh and brackish water origin vitrinite reflectance data of this maturity generation range from 0 65 to 0 90 roil and thus characterize thermally mature source rocks a rank which is corroborated by fluorescence and molecular characteristics the predominance of vitrinite in the maceral assemblages and the occurrence of biomarkers of terrigenous origin suggest that the major part of the mud matrix derives from a lacustrine or riverine sedimentary unit in the subsurface possibly from the messinian stage a third generation of organic material includes inertinites and vitrinites of high reflectance which represent recycled organic matter present in any marine sediment by use of the lopatin method for modelling the thermal maturation of hydrocarbon source rocks from the vitrinite reflectance data we calculated that the depth of mobilization ranges from 4900 m to 7500 m depending upon the temperature gradient used

channelized and hillslope sediment transport and the geomorphology of mountain belts this paper uses the results of landscape evolution models and morphometric data from the andes of northern peru and the eastern swiss alps to illustrate how the ratio between sediment transport on hillslopes and in channels influences landscape and channel network morphologies and dynamics the headwaters of fluvial and debris flow dominated systems channelized processes are characterized by rough high relief highly incised surfaces which contain a dense and hence a closely spaced channel network also these systems tend to respond rapidly to modifications in external forcing e g rock uplift and or precipitation this is the case because the high channel density results in a high bulk diffusivity in contrast headwaters where landsliding is an important sediment source are characterized by a low channel density and by rather straight and unstable channels in addition the topographies are generally smooth the low channel density then results in a relatively low bulk diffusivity as a consequence response times are greater in headwaters of landslide dominated systems than in highly dissected drainages the peruvian and swiss case studies show how regional differences in climate and the litho tectonic architecture potentially exert contrasting controls on the relative importance of channelized versus hillslope processes and thus on the overall geomorphometry specifically the peruvian example illustrates to what extent the storminess of climate has influenced production and transport of sediment on hillslopes and in channels and how these differences are seen in the morphometry of the landscape the swiss example shows how the bedding orientation of the bedrock drives channelized and hillslope processes to contrasting extents and how these differences are mirrored in the landscape

constraints on the long term colluvial erosion law by analyzing slope area relationships at various tectonic uplift rates in the siwaliks hills nepal 1 the large database of topographic form and uplift rates that exists for the siwaliks hills central nepal makes possible a thorough analysis of the long term erosion model the study especially focuses on drainage areas larger than 5 10 3 km2 fixed by the database resolution and smaller than 1 km2 above which a fluvial signature is recorded this area range corresponds to colluvial valleys in which the dominant erosion process is likely debris flow we evaluate a phenomenological model wherein erosion is considered to depend on drainage area and slope we test this model by assuming that the uplift rate is in approximate equilibrium with erosion the stream power law model formulated by analogy to river incision and transport problems is found to be consistent with data since an inverse power law relationship between slope and drainage area is systematically observed between 7 10 3 and 1 km2 with little variability on the exponent 0 24 thanks to the range of uplift rates we obtain constraints on the slope dependency of erosion law which appears linear and which predicts a significant erosion threshold the linear dependence on slope in the debris flow zone is consistent with findings by kirby and whipple 2001 in the fluvial downstream zone and with the linear relationship between local relief and uplift rate documented by hurtrez et al 1999 the transition between this colluvial channel regime and the fluvial regime appears quite sharp in contrast with recent studies but the latter regime is not sufficiently documented to derive definite conclusions

lipid biomarkers in sediments of mud volcanoes from the sorokin trough ne black sea probable source strata for the erupted material abstract mud volcanoes mvs are formed by expulsion due to lateral or vertical compression of overpressured fluids in the sub surface their sediments are characterized by a specific lithology called mud breccia which is composed of inorganic and organic matter sourced from different sedimentary units and transported from the sub surface to the seafloor biomarker lipid distributions were determined for sediment cores collected from the kazakov nioz and odessa mvs in the sorokin trough northeastern black sea this revealed different mud breccia sources that are directly linked to the location of the fracture zones or diapiric folds formed by tectonic compression the kazakov mv shows biomarker characteristics of relatively mature organic matter likely related to the maycopian shale formation the nioz and odessa mvs contain immature organic matter derived from much shallower sediments overpressed by rising maycopian diapirs in the mud breccia from the nioz mv biomarkers clearly record two different mud eruption episodes reflected in distinct distributions from unrelated sedimentary facies hence the study shows that although the organic matter of a mud breccia is sourced from a complex mixture of lithofacies the collective biomarker signal reveals specific signatures of the sedimentary sections that contributed most to the migrated fluid

the oxaya anticline northern chile a buckle enhanced by river incision a prominent structure in the western escarpment of the andes of northern chile is the oxaya anticline dissected at the culmination by 1500 m deep valleys the distribution of fault and fold structures indicates that the anticline could represent a simple buckle buckling thus appears to have accommodated crustal shortening in the plate overriding the subducting plate between the trench and the western cordillera cross cutting relationships between structures and dated strata indicated that the time interval of enhanced buckling coincides with the period when rates of valley formation were enhanced we thus propose that the formation of this anticline was enhanced by fluvial incision which is consistent with the results of published theoretical models

a neogene giant landslide in tarapaca northern chile a signal of instability of the westernmost altiplano and palaeoseismicity effects abstract giant landslides which usually have volumes up to several tens of km 3 tend to be related to mountainous reliefs such as fault scarps or thrust fronts the western flank of the precordillera in southern peru and northern chile is characterized by the presence of such mega landslides a good example is the latagualla landslide 19 15 s composed of 5 4 km 3 of miocene ignimbritic rock blocks located next to the moquella flexure a structure resulting from the propagation of a west vergent thrust blind fault that borders the precordillera of the central depression the landslide mass is very well preserved allowing reconstitution of its movement and evolution in three main stages the geomorphology of the landslide indicates that it preceded the incision of the present day valleys during the late miocene given the local geomorphological conditions 8 9 ma ago morphology slopes and probably a high water table large magnitude earthquakes could have provided destabilization forces enough to cause the landslide on the other hand present seismic forces would not be sufficient to trigger such landslides therefore the hazard related to them in the region is low

geomorphologic environment and age of supergene enrichment of the cuajone quellaveco and toquepala porphyry copper deposits southeastern peru copper ore grades of the cuajone quellaveco and toquepala porphyry cu mo deposits situated at 3 000 to 4 000 m a s l on the pacific slope of the cordillera occidental of southernmost peru lats 17 degrees 02 17 degrees 15 s have been markedly increased by supergene sulfide enrichment following the emplacement of the hypogene mineralization in the early eocene 52 57 ma as the terminal stage in the development of the toquepala group continental volcano plutonic terrane this andean transect was gradually reduced by erosion in a semiarid climate to a low altitude topography unroofing of the deposits had taken place by the mid oligocene the initiation of cordilleran uplift at ca 25 to 26 ma accompanied by the episodic eruption of felsic ash flow tuffs at the oceanward front of the volcanic arc led to more rapid erosion and the conversion of the mid tertiary landscape into the subplanar altos de camilaca surface this regionally extensive pediplain constitutes the major landform component of the present precordillera surrounding the porphyry centers its final configuration was attained at ca 18 to 19 ma ash flow tuff eruption was widespread and frequent at this time supergene enrichment began in the late oligocene during the progressive lowering of topography and continued through the more abrupt water table depression resulting from the latest oligocene to early miocene uplift however the distribution of chalcocite sensu lato in the three porphyry deposits and the local postmineralization landforms and volcanic histories differed significantly during the latter interval at toquepala and to a lesser extent quellaveco the landform regimes were dominated by open valleys and ignimbrite blanketing was short lived whereas the exposed cuajone deposit was both the site of aggressive early miocene valley incision and the deposition of an unusually thick in part welded ash flow tuff at 22 8 or 0 7 ma as a result the enrichment blanket at cuajone remained relatively thin and was even partially eroded in the early miocene whereas the blankets at quellaveco and toquepala were thickened continued strong uplift in the mid miocene ca 8 15 ma generated the array of apron and terrace pediments of the multiple pediment stage which dominates the lower cordilleran slopes and in the mineralized areas led to the deepening of existing valleys and the development of new fluvial channels ignimbrite eruption persisted throughout the miocene again local regimes of erosion and volcanism proved inimical to supergene activity at cuajone but enrichment continued at quellaveco and particularly toquepala where there is no record of later miocene ash flow accumulation uplift in this period was apparently also most extensive in the vicinity of the toquepala deposit which experienced the formation of a deep chalcocite blanket while the extant enrichment zone at quellaveco was thickened the development of enriched assemblages containing massive chalcocite had clearly terminated by 13 1 or 0 4 ma at cuajone and by 9 5 or 0 5 ma at quellaveco the timing of later enrichment at toquepala is less constrained but a mid miocene age is probable supergene upgrading of the three peruvian deposits was contemporaneous with that of copper mineralization in northernmost and northern chile as at chuquicamata and la escondida and in the copiapo mining district in all of which areas a late oligocene to mid miocene age has been inferred for supergene alteration this major and regionally developed metallogenic episode took place during and between two major periods of cordilleran uplift under semiarid climatic conditions the termination of intense enrichment along this 2 000 km stretch of the cordillera occidental in the late miocene was a direct result of marked climatic desiccation which not only reduced the overall supergene activity but focused fluvial erosion leading to the incision of steep walled canyons less favorable for supergene alteration than the earlier subplanar landforms

lithology of mud breccia clasts from the mediterranean ridge abstract clasts from mud breccia extruded by mud volcanoes discovered during the ttr 3 cruise of the r v gelendzhik 1993 on the mediterranean ridge are represented by a number of different source rocks they provide important information about the composition and genesis of the deep seated deposits of the mediterranean ridge detailed descriptions of the main rock types obtained as clasts from the mediterranean ridge mud breccia were made on the basis of a study of more than three hundred thin sections and x ray data the genetic features of the rock types indicate deep sea conditions during their accumulation and the presence of turbidities in the sedimentary sequence of the mediterranean ridge this suggests that turbidity currents from the african margin were capable of reaching the area presently forming the modern mediterranean ridge crest and that the mediterranean ridge was not a positive morphologic structure during the accumulation of lithologies which were extruded from depth by mud volcanoes the dating of the clasts should shed some light on the history of the mediterranean ridge

seismic character of bottom simulating reflectors examples from the mid norwegian margin three classes of bottom simulating reflectors bsr cross cut the post breakup sediments of the mid norwegian margin the first class is caused by free gas at the base of the pressure and temperature dependent gas hydrate stability zone the second class of bsr is caused by the diagenetic transition from opal a to opal ct the third class of bsr is always observed underneath the opal a opal ct transition but heat flow data and the amplitude characteristics of this arrival exclude one of the known silicate diagenetic transitions or gas hydrates as the explanation for this reflector odp site 643 drilling results from the voring plateau suggest two possible processes as the reason for this third bsr a smectite illite conversion or b a sudden increase in the abundance of authigenic carbonates the genesis of both is pressure and temperature dependent and could potentially result in a cross cutting seismic reflector the data are not conclusive as to which process is causing the third class of observed bsr

organic geochemical evidence of late glacial holocene climate instability in the north aegean sea sedimentary molecular biomarker compositions organic carbon and caco3 concentrations and bulk organic 13c and total 15n values document a series of paleoclimatic changes that have affected organic matter production and sedimentation in the north aegean sea from the termination of the latest glacial maximum through the middle holocene continental environmental conditions have been inferred from land plant biomarkers paleoproductivity patterns of diatoms prymnesiophytes dinoflagellates and nannoplankton were discerned from marine derived biomarkers although organic matter is predominantly marine variations in the proportion of marine and land contributions and in its general preservation are evident rapid changes in the eastern mediterranean thermohaline circulation evidently occurred in parallel to sea surface temperature oscillations enhanced deep water ventilation accompanied cold intervals in the late last glacial the younger dryas and during an interruption of deposition of the s1 sapropel probably in response to strengthening of north winds over the region in contrast decreased thermohaline circulation occurred during the warm interval associated with the s1 sapropel during this period increased freshwater inputs diminished ventilation of deep water masses and enhanced organic matter production and preservation intriguing fluctuations in sea surface temperatures and the concentrations of marine and terrestrial biomarkers within the sapropelic layer most prominently in the interruption from 8 2 to 7 8 calibrated radiocarbon conventional kyr bp support the hypothesis that several distinct events of deep water reoxygenation occurred in the north aegean sea during deposition of the s1 sapropel these events reflect centennial excursions to the more common low productivity and well ventilated conditions of the mediterranean that may possibly be related to north atlantic oscillation cycles

relationships between landscape morphology climate and surface erosion in northern peru at 5 s latitude the northern segment of the peruvian andes is affected by a twofold climate with measurable implications on landscapes and landscape dynamics during normal or neutral years easterly winds bring rain from the atlantic and the amazon basin to the sierras which results in a seasonal climate with rather low intensity precipitations in contrast during the large scale warm phase of the enso cycle el ninos transfer moisture from the pacific to the peruvian coast by westerly winds and result in high intensity precipitation we investigate the effects of this twofold climate for the case of the piura drainage basin at ca 5 s latitude northern peru in the headwaters that have been under the influence of the easterlies the landscape is mantled by a thick regolith cover and dissected by a network of debris flow channels that are mostly covered by a thick layer of unconsolidated sediment this implies that in the headwaters of the piura river sediment discharge has been limited by the transport capacity of the sediment transfer system in the lower segment that has been affected by high intensity rainfall in relation to the westerlies el ninos the hillslopes are dissected by debris flow channels that expose the bedrock on the channel floor implying a supply limited sediment discharge interestingly measurements at the piura gauging station near the coast reveal that during the last decades sediment was transferred to the lower reaches only in response to the 1982 1983 and 1997 1998 el nino periods for the latter period synthetic aperture radar sar intensity images show that the locations of substantial erosion are mainly located in areas that were affected by higher than average precipitation rates most important these locations are coupled with the network of debris flow channels this implies that the seasonal easterlies are responsible for the production of sediment through weathering in the headwaters and the highly episodic el ninos result in export of sediment through channelized sediment transport down to the coastal segment both systems overlap showing a partially coupled sediment production delivery system

origin of mud breccia from the mediterranean ridge accretionary complex based on evidence of the maturity of organic matter and related petrographic and regional tectonic evidence abstract drilling the milano mud dome situated in the olimpi field on the northern flank of the mediterranean ridge accretionary complex has documented episodic eruptive activity over the last 1 to 1 5 million years mud extrusion is related to backthrust faulting due to subduction of the africa plate beneath a relatively rigid backstop of cretan continental crust the mud dome is mainly composed of mud breccia with up to 65 of polymictic clasts embedded in a clayey matrix previously published results from petrography and new maturity data of both clasts and mud matrix presented here allow us to distinguish between two different areas of provenance 1 a northern province characterised by a trimodal maturity distribution of organic material was found for the majority of the mud breccia matrix samples studied similarly some of the clasts studied show the three vitrinite reflectance populations these are carbonate and sandstone clasts inferred to have been eroded from the upper nappes of the cretan thrust stack after exhumation in the late miocene as well as mudstone clasts clay mineralogy of these clasts coincides with earlier results on seafloor samples of a northern provenance recovered in the hellenic trench 2 a southern provenance is proposed for a second group of clasts with a bimodal maturity distribution not showing the second population 0 64 0 82 rm these clasts are litharenites calcilutites and calciturbidites of a proposed southern provenance i e north africa the presence of huminite in all clast and matrix samples studied 0 26 0 45 rm is indicative of a shallow burial history estimates regarding the depth of mobilisation of the mud using the regional thermal gradient indicate burial not deeper than 2 km below the seafloor organoclastic matrix components mirror the northern clast provenance so that prior to subduction and subsequent extrusion deposition of the mud in the northeastern mediterranean can be inferred we propose a model in which sediment from the north was trapped within the forerunner of the pliny trench this sediment was deposited above the backstop of the subduction complex which was later overridden by the accretionary prism as a result of incipient collision density inversion forces then favoured uprise and extrusion of underconsolidated sediments as mud volcanoes the mud matrix was probably largely derived from a messinian succession although alternatives remain possible

scale of relief growth in the forearc of the andes of northern chile arica latitude 18 s the stream profiles of rivers of northern chile reveal two graded segments separated by 20 km long knickzones their formation was initiated in the late miocene in response to surface uplift of the western flank of the altiplano this phase of uplift that was coeval with the shift of deformation from the altiplano to the sub andean zone caused relief to grow at the scale of the whole drainage basin above and beneath these knickzones the presence of braided channels and the absence of erosion on adjacent pediplains suggest no substantial modification in the local relief the knickzones however show bedrock channels and fluvial dissection rates have exceeded erosion rates on adjacent pediplains by two orders of magnitudes hence the data imply that the only geomorphic recorders of relief growth are the knickzones that currently transpose the effects of the late miocene phase of surface uplift from the coast to the altiplano

the giant coastal landslides of northern chile tectonic and climate interactions on a classic convergent plate margin abstract documented for the first time are an extensive suite of late neogene giant terrestrial coastal landslides along the classic convergent margin of western south america 18 to 24 south these are remarkable in terms of their unusual abundance and atypical setting such failures previously being linked with oceanic volcanic edifices or over steepened glaciated coastlines located within the hyper arid coastal cordillera of the atacama desert of northern chile we report the presence of more than 60 individual large scale landslides with individual volumes up to 9 km 3 developed over a horizontal coastline distance of some 650 km these landslides were emplaced as a combination of rock avalanches and multiple rotational failures the majority terminated directly into the pacific likely generating significant tsunami hazard to the chilean and south peruvian coastline in a region which is today considered to be part of a notorious seismic gap the proliferation and scale of these late neogene giant landslides in this actively uplifting hyperarid terrain suggests they are the main geomorphic agent for relief reduction probably triggered by megathrust earthquakes and potentially providing a unique palaeoseismic archive the temporal and spatial distribution of these giant landslides corresponds with a period of surface steepening of the forearc wedge in the central andes and south to north differential uplift associated with factors such as aseismic ridge subduction the resulting surface gradient increases combined with the persistent climatic aridity of the region have served to limit effective relief reducing geomorphic processes in this oversteepened terrain to large scale landsliding the phenomena documented here geospatially link previously recognised large scale slope failures from the off shore environment and higher altitude areas of the andean forearc suggesting that large scale landsliding is capable of transferring sediment on a regional scale to the off shore peru chile trench this has implications for the friction of the subducting nazca plate and associated seismicity and uplift

sensitivity of biomarker properties to depositional environment and or source input in the lower toarcian of sw germany abstract a sequence of lower toarcian sediments which are highly contrasting in their depositional environment over a 5 m depth interval has been investigated in detail for the variability of geochemical properties which are used for source characterization and oil to source correlation lower liassic marls are representative of a well aerated shallow water environment in contrast to the immediately overlying bituminous shales which are deposited under extremely reducing conditions various properties have been found to vary considerably within these two units amongst the most important are carbon isotopic composition of the kerogen the pristane phytane ratios nickel as opposed to vanadyl porphyrins and the c27 dia regular steranes although maturation within the profile does not change some of the maturation dependent biomarker properties such as the monoaromatic steroid side chain cracking and the tm ts ratio exhibit large changes which can be assigned to diagenetic processes another maturation dependent property the 20s 20r epimerization of c29 steranes exhibits smaller changes which could also be due to early diagenetic processes the study suggests that reducing and oxidizing conditions i e eh and ph in the sediment exert an influence on several biomarker precursor product pathways in maturation studies initial variations due to depositional conditions have therefore to be taken into account

late quaternary pelagic sedimentation on the southern calabrian ridge and western mediterranean ridge eastern mediterranean abstract cores from plateaus lying some 150 200 m above the basin floors in areas of strong vertical relief visited during the cobblestone project consist entirely of pelagic marls with sapropels and tephras as minor lithologies all the plateau cores were correlated by means of isochronous lithologies and biostratigraphically calibrated a core from area 3 no 29 and two cores from area 4 no 45 and 6 were selected as reference sections and studied quantitatively in terms of grain sizes carbonate content and microfossil content faunal curves based on selected species of planktonic foraminifers correlate between the three cores which extend back in time to approximately 185 000 yr for area 4 and to 430 000 yr for area 3 winnowing resulted in a reduced sedimentation rate in area 3 in unusually high percentages of the coarser sediment fraction and in extended hiatuses at the top of the cores the highest temperature in surficial waters as indicated by the foraminiferal faunas is recorded in all three references sections at the base of an interval correlative with isotopic stage 5e 125 000 yr b p within sapropel s 5 clay mineralogy indicates basically uniform conditions in the two areas with the exception that smectite is more abundant in the calabrian ridge which is closer to its source area sicily sicily channel carbonates include calcite magnesian calcite and some dolomite sapropels sedimentary expression of stagnation represent up to 25 of the sedimentary column in an interval encompassing isotopic stage 5 through 7 the average organic carbon content in analysed sapropels is 3 1 versus 0 29 in normal pelagic sediments sapropels s 6 and s 8 are consistently accompanied by a foraminiferal fauna that is indicative of low salinity cool surficial waters whereas sapropels s 1 s 5 and s 7 occur in coincidence with the warmest peaks of the climatic faunal curve average sedimentation rate is 3 2 cm 1000 yr for core 29 5 5 cm 1000 yr for core 45 sedimentation rates calculated for basin cores are five to ten times higher sedimentation rates of sapropels and tephras are independent from regional sedimentation rates hiatuses in plateau cores correlate with debris flows in base of slope cores both occurring during times of enhanced bottom circulation and submarine erosion related to low stands of sea level in cold periods

a mass wasting dominated quaternary mountain range the coastal range in eastern taiwan abstract fluvial bedrock incision which creates topographic relief and controls hillslope development has been considered the key medium linking denudation and tectonic uplift of unglaciated mountains this article however shows a different scenario from the coastal range in eastern taiwan this range with the steepness inherited from pre orogenic volcanoes has been subject to mass wasting even before its emergence above sea level no earlier than middle pleistocene numerous terraced alluvial fans fan deltas record the ancient mass movements of the range including rock avalanches multiple radiocarbon dates 1 km 2 alluvial terraces are typically exhibited close to the source ridges of mass movements and strath terraces along the downstream parts of rivers both were created when enormous sediment supply had exceeded or matched the prevailing river transport capacity this process along with the protection by giant boulders from mass movement disturbed the long term incision trend of rivers in response to tectonic uplift as a result the observed holocene bedrock incision at most sites has not kept pace with the tectonic uplift the spatial contrast in mass wasting histories further accounts for the great diversity of the terrace sequences even in areas with similar tectonic and base level conditions

late pliocene age for the atacama desert implications for the desertification of western south america the atacama desert forms one of the major hyperarid deserts of the world previous studies suggest that desertification commenced at 14 ma during global climate desiccation sedimentologic data from middle miocene to upper pliocene successions in the modern atacama desert indicate that a semiarid climate persisted from 8 to 3 ma punctuated by a phase of increased aridity at ca 6 ma as such hyperaridity did not commence until the late pliocene implications are 1 that the rain shadow generated by the andean cordillera has had a minor influence on climate change and 2 that the upwelling north flowing cold humboldt current although important in establishing the generally arid climate of western south america did not control the shift to hyperaridity the formation of the hyperarid atacama desert in the late pliocene accompanied the development of the current phase of aridification in the sahara and namib deserts and is attributed to a phase of global climate cooling

a geochemical study of long chain n aldehydes in washington coastal sediments a series of n aldehydes c20 to c32 with strong even to odd carbon preference was identified in the mixture of solvent extractable lipids isolated from various washington coastal sediments a limited survey of the lipid composition of surface waxes of foliage and cuticular waxes of pollen from several major plant species indigenous to the pacific northwest revealed that similar series of n aldehydes are intrinsic to regional vegetation debris from such plants discharged at the mouth of the columbia river represents a preformed source of the n aldehyde series accumulating in sediments from the washington coastal region although the evidence suggests n aldehydes are largely introduced erosionally to this region as a chemical component of land derived debris and are not formed in situ in the coastal sediments further study is warranted to establish the postdepositional stability of this series of compounds relative to other lipids of higher plantwax origin despite but few literature reports of the occurrence of these geochemicals long chain n aldehydes are very likely common in many sediments from environments that receive an input of detrital organic matter from higher plants

tectonic and climatic controls on the spatial distribution of denudation rates in northern chile 18 s to 23 s determined from cosmogenic nuclides in the arid region of northern chile the environmental conditions are favorable for measuring tectonic and climatic influences on catchment denudation rates in the absence of vegetation previous studies of denudation rates from cosmogenic 10be and 26al concentrations are limited to single drainages in this study we examine catchment to orogen scale spatial variation in denudation rates between 18 23 s in the coastal and western cordilleras of northern chile 10be and 26al data were obtained from 33 catchments to examine the relative roles of tectonics and climate on catchment averaged denudation rates at broader scales we examine whether denudation rates and orogen topography reflect the 3d plate geometry of the region cosmogenic nuclide derived denudation rates range from 0 4 0 5 to 20 6 1 5 m myr in the coastal cordillera and from 1 4 0 7 to 168 0 19 8 m myr in the western cordillera the controls on the denudation rates are evaluated using a statistical factor analysis of ten selected catchment parameters denudation rates indicate a strong linear relationship with channel steepness indices but insignificant correlations and covariation with mean annual precipitation rates drainage area stream order mean elevation mean local relief mean basin slope and analyzed grain size of the sampled sediments moreover denudation rates are better correlated with tectonic controls at catchment scale than orogen scale plate tectonics in the western and coastal cordillera

stratigraphy and sedimentation in the mediterranean ridge diapiric belt abstract two basic sediment types are recorded in the mediterranean ridge diapiric belt the host sediment and the mud breccia the host sediment consists of hemipelagic marl as dominant lithology associated with sapropels and tephras as minor isochronous lithologies a high resolution stratigraphy which allows much more detailed and precise correlations than those based on biostratigraphy essentially calcareous nannofossils is applicable to the over 20 cores considered in this study that were obtained during cruise ttr3 leg 2 in 1993 the mud breccia is matrix supported and contains submillimetric to pluricentimetric clasts in various amounts staffini et al 1993 this lithology is consistently related to doming physiographic features of different size and shape camerlenghi et al 1992 and to high reflectivity patches recorded on long range side scan sonar the mud breccia can be intruded or extruded the massive course nature of the mud breccia recorded in the large majority of the 16 cores that contain this lithology may suggest intrusion cores from napoli dome which is typically an active mud volcano cita et al 1994 are fine grained and very gaseous contacts between the mud breccia and the host sediment are mostly distinct but may be gradational two cores document interlayering of the mud breccia with pelagic sediments but not turbidites were ever recovered among the main results of the study we mention the strong slope instability documented by the pelagic host sediments from the ridge diaperic belt hiatuses microfaults hardgrounds the wide distribution of diapiric features across the ridge axis from the inner deformation front to the toronto dome some 50 km to the south the age of the mud breccia matrix essentially which is consistently early middle miocene with some older elements but strictly middle to late cretaneous for the southernmost toronto dome

paleoenvironmental significance of compound specific δ13c variations in n alkanes in the hongyuan peat sequence from southwest china over the last 13 ka abstract compound specific 13c 12c ratios of the c23 c25 c27 c29 and c31 n alkanes in the hongyuan peat sequence from southwest china were measured to decipher paleoenvironmental information recorded in the 13c variations over the last 13 ka the 13c values of the n alkanes range between 35 4 and 30 5 falling within the range of those from modern c3 peat forming vegetation however the vertical trends do not match with those of the 13c value for the c3 peat forming plant cellulose such a discrepancy between the 13c profiles implies that the n alkane 13c values are unlikely to reflect signals from emerged aquatic plants in the bog because submerged floating aquatic plants are major contributors of mid chain c23 and c25 n alkanes in the sequence the decoupling between the c23 and c25 n alkanes and the peat cellulose likely reflects the situation that these mid chain homologues primarily record the isotopic signals of submerged floating aquatic plants the stratigraphic profile of 13c values of submerged floating aquatic plant n alkanes c23 and c25 reveals two prominent positive excursions 0 8 2 4 during the early to middle holocene the excursions coincide with peat accumulation maxima and stronger indian monsoon activity in southwest china indicating that the 13c variations in submerged floating aquatic plants are closely related to changes in bog primary productivity controlled by the asian monsoon activity

biomarker and 16s rdna evidence for anaerobic oxidation of methane and related carbonate precipitation in deep sea mud volcanoes of the sorokin trough black sea many mud volcanoes were recently discovered in the euxinic bottom waters of the sorokin trough ne black sea three of them i e nioz odessa and kazakov were selected for a detailed biogeochemical investigation four methane related carbonate crusts covered with microbial mats and sediments dmud brecciat from these mud volcanoes were collected during the 11th training through research cruise ttr 11 in 2001 the first finding of methanotrophic microbial mats associated with authigenic carbonates in the deep black sea we measured the concentrations and 13c values of methane and specific archaeal and bacterial lipids and determined archaeal and bacterial 16s rrna gene sequences the 13c of the microbial lipids reflected the carbon isotopic values of the methane indicating that methane was the main carbon source for microorganisms inducing carbonate formation anaerobic oxidation of methane aom in these settings was performed by archaea affiliated with the so called anme 1 group none of the identified archaeal sequences were closely related to known methanogens the combined 16s rrna gene sequence and biomarker data revealed a distinct difference in archaeal assemblage between the carbonate crusts and mud breccias besides gene sequences of sulfate reducing bacteria dna analysis of bacterial communities revealed a diversity of bacteria with apparent contrasting metabolic properties the methane utilization via aom processes was detected in the uppermost sediments where it subsequently induces authigenic carbonate precipitation most probably below seafloor the results of integrated biomarker and 16s rrna gene study reveal a crucial role of aom processes in formation of authigenic carbonates in methane seep environments

odp leg 107 in the tyrrhenian sea insights into passive margin and back arc basin evolution leg 107 of the ocean drilling program drilled a west northwest east southeast transect of seven sites across the tyrrhenian sea the youngest of the sub basins of the mediterranean sea sites 654 653 652 and 656 document the rifting and subsidence of the sardinia passive continental margin on the upper margin site 654 we cored a classic transgressive sequence subaerial conglomerates overlain by oyster bearing sands overlain by marine marl comparison between the recovered lithologies and seismic reflection profiles suggests that the synrift sediments on the upper margin are tortonian late miocene to messinian latest miocene in age whereas synrift sediments on the lower margin are messinian to pliocene in age during the messinian desiccation of the mediterranean sites 654 and 653 now on the upper sardinian margin apparently occupied a basinal setting where they received nannoplankton bearing clays interbedded with laminated gypsum sites 656 and 652 now on the lower sardinia margin were apparently higher standing during the desiccation event their messinian facies are subaerial and lacustrine respectively we infer from these lines of evidence that tilting and subsidence occurred more than a million years earlier on the upper margin than on the lower margin such diachroneity can be interpreted in terms of migration of the zone of maximum extension above a rolling back subduction zone or in terms of extension of continental crust by shear along a deep detachment fault sites 655 651 and 650 were drilled into two small basalt floored basins of the central and eastern tyrrhenian emplacement of basaltic crust in the central tyrrhenian vavilov basin apparently began more than a million years before emplacement of basaltic crust in the eastern tyrrhenian marsili basin this observation is compatible with previous suggestions that the tyrrhenian has grown southeastward in response to rollback of the down going slab that currently dips northwestward under the toe of italy at the easternmost site high vesicularity of the basalt and benthic foram assemblages in the oldest sediments imply that the basalt erupted in water shallower than 2 500 m it has apparently subsequently subsided to its present depth of 4 100 m below sea level nearly three times as fast as normal subsidence of crust formed at a mid ocean ridge

middle miocene climatic change in the atacama desert northern chile evidence from supergene mineralization at la escondida geochronology and paleotopographic reconstruction of the porphyry copper deposit at la escondida chile are used to calculate long term erosion rates and to deduce the timing of tertiary climatic change for a portion of the atacama desert region hypogene hydrothermal alteration and protore mineralization at la escondida took place between 33 7 1 4 and 31 0 1 4 ma based on k ar dating of hydrothermal biotite and sericite supergene weathering and copper sulfide en richment processes were active from 18 0 0 7 to 14 7 0 6 ma based on k ar dating of supergene alunite distinguished from hypogene alunite by grain size color and sulfur isotopic composition reworked lenses of volcanic ash in the vicinity of la escondida provide useful time stratigraphic markers at 8 7 0 4 6 5 0 2 and 4 2 0 2 ma within present soil profiles long term average rates of erosion are determined by these age dates and quantitative calculation of eroded leached capping thickness at la escondida using mass balance analysis of geochemical profiles coupled with an estimate of unmineralized lithocap thickness based on alteration petrology and fluid inclusion geobarometry at similar deposits the observed trend of decreasing long term average erosion rates with time is consistent with arid to semiarid conditions in the early miocene changing to hyperarid conditions during the middle miocene this climatic desiccation caused termination of significant supergene copper suffide enrichment at la escondida and elsewhere in the atacama region and preservation of surficial features including the ash horizons and the leached capping middle miocene climatic desiccation in northern chile and southern peru was probably related to a pronounced decrease in temperature of coastal waters supplied by an ancestral humboldt current and an increase in upwelling intensity as the antarctic ice cap became established at approximately 15 to 13 ma the central andes cordillera which now provides a rain shadow protecting the atacama region from precipitation from the east must have attained at least half its present elevation prior to about 15 ma to have played a similar role in the middle miocene

late pleistocene fans and terraces in the majes valley southern peru and their relation to climatic variations this study investigates the connection between sediment aggradation erosion and climate in a desert environment of the majes valley southern peru luminescence dating of terraces and fans shows that sediment aggradation correlates with wet time intervals on the altiplano suggesting a climatic influence on the aggradation degradation cycles major periods of aggradation occurred between 110 100 60 50 and 12 8 ka more precipitation in the majes catchment resulted in increased erosion and transportation of sediment from the hillslopes into the trunk river as a result the sediment loads exceeded the transport capacity of the majes river and aggradation started in the lower reaches where the river gradient is less depletion of the hillslope sediment reservoirs caused a relative increase in the capacity of the trunk river to entrain and transport sediment resulting in erosion of the previously deposited sediment consequently although climate change may initiate a phase of sediment accumulation degradation can be triggered by an autocyclic negative feedback and does not have to be driven by climatic change

groundwater sapping origin for the giant quebradas of northern chile northernmost chile is home to a well preserved disequilibrium landscape of great antiquity contrasting drainage patterns are developed on the western slope of the altiplano plateau the oldest of these patterns is a now relict parallel patterned drainage network in places a younger pattern comprising a series of deeply incised canyons or quebradas crosscuts the older parallel patterned network these canyons show strong evidence of a groundwater sapping origin we hypothesize that the initiation of the canyon network resulted from changes in the hydrological regime related to a drying out of climate of the forearc and to the uplift of the altiplano plateau

extreme efficiency of mud volcanism in dewatering accretionary prisms drilling results from two mud volcanoes on the mediterranean ridge accretionary complex as well as bottom sampling and the wealth of geophysical data acquired recently have provided fundamental knowledge of the 3d geometry of mud extrusions mud volcanism is generally related to buoyancy density inversion and is triggered by the collision of the african and eurasian blocks forcing undercompacted clayey sediments to extrude along faults in the central and hinterlandward parts of the prism volumetric estimates of extruded mud in several well studied areas were based on pre stack depth migrated seismic profiles across the entire up to 150 km wide prism the resulting volumes of mud were combined with ages from mud dome drilling so that rates of mud extrusion were obtained subtracting the solid rock mass from the bulk mud volume using physical property data fluid flux as a function of mud volcanism alone has been quantified for the first time the volume of fluid extruding with the mud is found to be variable but reaches up to 15 km3 fluid per km trench length and ma along cross sections with abundant mud volcanoes such large fluid quantities in a region some 50 150 km behind the deformation front exceed estimates from those elsewhere where undoubtedly the majority of the interstitial fluid is lost due to compaction such fluids near the backstop are likely to result predominantly from mineral dehydration and diagenetic reactions at depth and consequently provide a window to understand deeper processes along the deep decollement more importantly the enormous rates with which such fluids and liquified mud escape along the out of sequence faults alter fluid budget calculations in subduction zones drastically

the largest prehistoric landslide in northwestern slovakia chronological constraints of the kykula long runout landslide and related dammed lakes abstract this study deals with the chronology of the largest long runout landslide in the northwesterrn part of the western flysch carpathians kysucke beskydy mts slovakia despite the impossibility of using direct radiocarbon dating method time constraints for the evolution of the landslide were determined on the basis of the dating of various sedimentological geomorphological elements situated on and adjacent to the landslide body the results show that the landslide evolved between 10 3 and 9 0 ka 14 c bp i e in the wider transitional phase between the late glacial lg and the holocene the main mass movement activity took place at the turn of the younger dryas preboreal chronozones whereas retrogressive activity continued up to the preboreal boreal transition radiocarbon dating together with pollen analysis and sedimentology of landslide dammed palaeolakes and colluvial peat bogs revealed almost continuous holocene palaeogeographical records between 10 3 and 3 3 ka 14 c bp periods of enhanced sediment supply to the reservoirs in 9 9 9 0 8 4 8 2 6 9 6 5 and 4 5 ka 14 c bp correlate well with palaeogeomorphic and palaeohydrological records from nearby polish carpathians the study confirms that the lg holocene transition represented a favourable period for the evolution of large landslides not only in glaciated high mountain areas but also in medium high mountains of central europe

the role of landslides in mountain range evolution abstract we review the role of landslides in current concepts of the topographic development of mountain ranges we find that many studies in this field address basin or orogen scale competition between rock uplift and fluvial bedrock erosion hillslopes in general and bedrock landslides in particular are often assumed to respond rapidly to incision and development of the fluvial drainage network this leads to a one sided view of the geomorphic coupling between hillslopes and rivers that emphasizes the fluvial control of hillslopes but ignores the alternative view that landslides can affect the fluvial network there is growing evidence that landslides are a dominant source of sediment in mountain belts and that they exert a direct geomorphic control on fluvial processes landslides can influence the river network in a variety of ways from determining basin area and drainage divide positions to setting streamwise variations in sediment load and calibre the geomorphic legacy of large landslides on hillslope and channel morphologies may persist for up to 104 yr adding considerable variability to fluvial erosion and sedimentation patterns over these timescales we identify a number of questions for future research and conclude that a better understanding and quantification of the geomorphic feedbacks between landslides and river channels builds an important link between short term 105 yr landscape evolution models

gigantic paleolandslide associated with active faulting along the bogd fault gobi altay mongolia on the basis of analyses of satellite imagery aerial photographs and field observations we describe the occurrence of one of the largest paleolandslides 50 km3 ever recognized in an intracontinental domain the slide occurred along the active bogd fault in the gobi altay mountain range in mongolia morphological and structural analyses of the relationships between the landslide and the area affected by active tectonics suggest that this gigantic mass movement was associated with surface faulting during a strong earthquake

rock avalanches clusters along the northern chile coastal scarp abstract rock avalanche clusters can be relevant indicators of the evolution of specific regions they can be used to define the type and intensity of triggering events their recurrence and potential probability of occurrence the progressive damage of the rock mass the mechanisms of transport and deposition as well as the environmental conditions at the time of occurrence this paper tackles these subjects by analyzing two main clusters of rock avalanches each event between 0 6 and 30 mm 3 separated by few kilometers and located along the coastal scarp of northern chile south of iquique it lies hence within a seismic area characterized by a long seismic gap that ended on april 1st 2014 with a m w 8 2 earthquake the scar position high along the coastal cliff supports seismic triggering for these clusters the deposits relative positions are used to obtain the sequence of rock avalanching events for each cluster the progressive decrease of volume in the sequence of rock avalanches forming each cluster fits well the theoretical models for successive slope failures these sequences seem to agree with those derived by dating the deposits with ages spanning between 4 kyr and 60 kyr an average uplift rate of 0 2 mm yr in the last 40 kyr is estimated for the coastal plain giving a further constraint to the rock avalanche deposition considering the absence of reworking of the deposits volume estimates and datings allow the estimation of an erosion rate contribution of about 0 098 0 112 mm km 2 yr 1 which is well comparable to values presented in the literature for earthquake induced landslides we have carried out numerical modeling in order to analyze the mobility of the rock avalanches and examine the environmental conditions that controlled the runout in doing so we have considered the sequence of individual rock avalanches within the specific clusters thus including in the models the confining effect caused by the presence of previous deposits bingham rheology was the most successful at explaining both the distance and the geometry of the observed events

structural setting and tectonic control of mud volcanoes from the central mediterranean ridge eastern mediterranean based on a recent marine geophysical data set including swath bathymetry acoustic imagery and six channel seismics recorded over a large area of the mediterranean ridge mr in early 1998 during the prismed 2 survey this paper presents a study of the various relationships observed between tectonic features cutting across the central mediterranean ridge accretionary wedge and massive mud expulsions known as mud volcanoes identified over large areas of the ridge regional mapping of two of the mud volcano fields previously only partly investigated olimpi and united nations rise revealed the presence of many new mud expulsion centres and a third new mud volcano field has been identified all the mud features show great variability in morphology size and backscatter strength of their surrounding mud flows based on their contrasting morpho acoustic characteristics we propose a classification into three main groups of mud construction 1 mud volcanoes these consist of subcircular and prominent reliefs often associated with high backscatter mud flows 2 mud domes similar to mud volcano but smaller these occurrences correspond to weakly reflective mud constructions 3 mud plateaus represent a third category which appears as wide often highly reflective and rather flat mud extrusions from all available data an attempt to explain the different mud ascent processes and driving forces is discussed in relation to the initial collision structural setting of the central mediterranean ridge within this area most of the mud constructions have been observed to be associated with tectonic features and in particular with strike slip faulting for the first time as a hypothesis we propose in this paper two different ascent processes to explain the contrasting mud constructions 1 extrusion for the mud volcanoes and plateaus and 2 intrusion for the mud domes connected to two different mud levels controlled by the crustal geometry of this pre collision area and especially the southwards extension of the cretan continental crust below the mediterranean ridge accreted sediments

characterization of debris avalanche deposits in japan abstract seventy one debris avalanche deposits are identified from 52 japanese quaternary volcanoes the structures of these volcanoes are mostly stratovolcanoes and lava domes no avalanche deposit is found in calderas pyroclastic cones or maar volcanoes debris avalanche deposits are found in 18 of all quaternary volcanoes or 25 of quaternary stratovolcanoes and lava domes the ratio rises to 49 when considering only active stratovolcanoes and lava domes at least five debris avalanche deposits have formed since 9th century the maximum height difference of sliding h for each debris avalanche ranges from 200 to 2400 meters and the maximum runout distance of sliding l ranges from 1 6 to 32 km the ratio h l ranges from 0 2 to 0 06 and becomes smaller in larger debris avalanches they are more mobile than landslides in non volcanic areas volume is within a range of 0 03 and 9 km 3 there is no relation between the direction of sliding and the regional horizontal compressional stress axis at the site of a volcano two dimensional computer simulations of avalanches using a simplified physical model are made the maximum velocity is mainly controlled by the length of steep slope

hopanoid hydrocarbon maturation by an igneous intrusion abstract the thermal effects of an igneous intrusion 0 9 m thick dyke upon the abundance and composition of hopanes and hopenes are reported for a suite of samples within a single sedimentary horizon a carbonate concretion 1 6 m in diameter from the jurassic dun caan shale member bearreraig bay isle of skye scotland the conventional hopane maturity parameters show normal trends towards the dyke and through the oil window approximately 22 45 cm from the dyke i e 25 50 dyke thickness with the exception of the ts ts tm parameter which shows a progressive fall with increasing maturity until the middle of the oil window when it increases markedly molecular abundances demonstrate that the observed changes in the hopane maturity parameters result from the combined effects of generation presumed to be from kerogen and degradation of individual compounds with isomerization in the free phase being minimal or unimportant the unexpected behaviour of ts ts tm results from the minimal generation of ts compared with tm our data indicate that the ts skeleton is not present in the kerogen and at least under the elevated heating associated with an igneous intrusion may be derived from 18 h 22 29 30 trisnorneohop 13 18 ene in the bitumen thermally induced modifications to hopane carbon number distributions are also reported and show that oil source rock correlations between samples of different maturity must consider the effects of generation degradation of kerogen bound hopanes

erosion rates and erosion patterns of neogene to quaternary stratovolcanoes in the western cordillera of the central andes an srtm dem based analysis abstract erosion patterns and rates of 33 stratovolcanoes in the arid to hyperarid central andean volcanic zone 14 s to 27 s have been constrained by morphometric modelling all selected volcanoes belong to the short lived symmetrical circular andesitic stratocone type with ages spanning 14 ma to recent starting from the initial youthful volcano morphology of this type represented in our study by parinacota volcano and comparing reconstructed volumes of progressively eroded volcanoes such a time span allows us to infer long term erosion rates typical erosion rates of