structural outline of a tertiary basement cored uplift inversion structure in western spitsbergen svalbard kinematics and controlling factors the tertiary fold and thrust belt of spitsbergen can be divided into a western basement involved fold thrust stack and a central eastern foreland fold and thrust belt in western nordenskiold land the first order structure is an ene verging basement cored fold and fault complex involving paleozoic to tertiary strata the northern part reveals an upright monocline geometry of east tilted sedimentary cover units with associated layer parallel to low angle thrusts and folds these structures consist of two populations oriented both parallel to nnw sse and oblique to wnw ese the general structural trend of the fold complex in the central and southern parts of west nordenskiold land the fold complex involves tilted basement cut by steep transverse faults and late normal faults the east limb of the fold complex displays repeated basement and paleozoic strata orustdalen formation in its core and mesozoic triassic strata influenced by map scale chevron folds and two decollement levels all located above an eastward rotated major detachment fault the kleivdalen thrust establishing fold fault relations includes a three stage structural history in the fold complex as follows 1 a phase of early nne ssw shortening associated with wnw ese folds and thrusts and 2 a dominant ene wsw basement involved shortening leading to the first order nnw sse striking fold complex followed by 3 approximately e w extension the resulting structures and structural variability along strike as well as across strike appear to have been controlled by basement and carboniferous basin structures underlying the permian cretaceous platform strata restored stratigraphic sections based on thrust repetition of basement and cover e g within a type section of the carboniferous orustdalen formation support such an interpretation a tentative inversion tectonic model reproduces the position s of local and major thrust ramps and associated folds as a result of inheritance from carboniferous basin structures

evolution of the central tertiary basin of spitsbergen towards a synthesis of sediment and plate tectonic history abstract the central tertiary basin of spitsbergen developed east of a strike slip boundary between the eurasian and greenland plates in response to the initiation of rifting and later seafloor spreading in the norwegian greenland sea using a new plate model for the opening of the north atlantic we attempt to relate the sediment history of the central tertiary basin to its plate tectonic framework and suggest a basin development in four phases the central tertiary basin was formed in the early paleocene during a right lateral strike slip phase after the plate boundary between greenland and svalbard had jumped eastward to the hornsund fault zone phase 1 the onset of seafloor spreading between greenland and eurasia and a drastic counterclockwise change in spreading direction between greenland and north america after chron 25 late paleocene induced compression dominated transpression between greenland and svalbard until chron 24 lower eocene phase 2 the first sedimentary evidence for tectonic uplift along the strike slip zone is found in a wedge shaped delta fan in the northwestern part of the basin strike slip dominated transpression prevailed from chron 24 to chron 21 lower middle eocene contemporaneous with successive basin narrowing and an eastward migration of the depocenter phase 3 after chron 21 lower middle eocene the relative motion between greenland and svalbard first changed to strike slip terminating the transpressional phase and then to transtension after chron 13 lower oligocene phase 4

a whiff of oxygen before the great oxidation event high resolution chemostratigraphy reveals an episode of enrichment of the redox sensitive transition metals molybdenum and rhenium in the late archean mount mcrae shale in western australia correlations with organic carbon indicate that these metals were derived from contemporaneous seawater rhenium osmium geochronology demonstrates that the enrichment is a primary sedimentary feature dating to 2501 8 million years ago ma molybdenum and rhenium were probably supplied to archean oceans by oxidative weathering of crustal sulfide minerals these findings point to the presence of small amounts of o 2 in the environment more than 50 million years before the start of the great oxidation event

present day stress orientations adjacent to active strike slip faults california and sumatra present day stress directions interpreted from well bore breakouts adjacent to two crastal scale active strike slip faults the san andreas fault in california and the great sumatran fault in sumatra indicate that the maximum horizontal stress direction sh is oriented at a high angle 70 90 to both faults the regionally defined stress fields spanning these faults show that adjacent young or actively growing folds have formed orthogonal to sh and are therefore in the thrust fault orientation these observations indicate a decoupling of the strike slip and compressional components of the deformation within these broadly transpressive zones borehole breakouts in 118 wells in western california indicate a regionally consistent stress pattern with sh generally oriented ne sw nearly perpendicular 80 90 to the strike of the san andreas fault the orientation of sh nearly perpendicular to the san andreas fault implies low shear stress on the fault and is consistent with geological interpretations of the coast and transverse ranges indicating active compressional deformation fault plane solutions for recent dip slip style earthquakes principal stress directions determined from inversion of earthquake focal mechanisms and induced hydraulic fracture orientations a stress trajectory map for western california is computed using an iterative statistical algorithm in which observed directional data such as breakout directions are used to obtain a model regional stress field analysis of well bore breakouts in 25 wells within the central and southern oil districts of sumatra indicates that the regionally defined sh adjacent to the active great sumatran strike slip fault is oriented at a high angle 70 80 to the fault this orientation of sh is consistent regionally with geologic stress indicators and focal mechanisms of dip slip earthquakes preliminary analysis of the stress field in the vicinity of the philippine and alpine faults suggests sh is also oriented at a high angle to these active strike slip faults similarly the minimum horizontal stress sh is oriented at a high angle to the the kane and dead sea transforms the observation of sh and sh in the vicinity of active strike slip faults being oriented nearly perpendicular and parallel to the faults suggests that large crustal scale strike slip faults may in general be inherently weak surfaces

linked thrust and strike slip faulting during late cretaceous terrane accretion in the san juan thrust system northwest cascades orogen washington the san juan thrust system makes up the western elements of the late cretaceous northwest cascades orogen of washington a stack of metamorphic nappes with terranes ranging in age from early paleozoic to middle cretaceous the tectonic development of the nappes is an unresolved issue important to understanding plate convergent processes operating in the north american cordillera in the creta ceous as well as at other times two terrane bounding fault zones were studied in this project the lopez and the rosario fault zones the fault zone rocks were affected by two cataclastic plastic late cretaceous deformational events d1 and d2 that included accretion and lateral motion during blueschist facies metamorphic conditions d1 produced upright folds and a subvertical axial planar s1 foliation fabric in the lopez fault zone and southwest vergent folds and gently northeast dipping axial planar s1 foliation in the rosario fault zone in the lopez fault zone d2 produced northwest striking and subvertical strike slip shear zones s2 with dominant sinistral displacements whereas in the rosario fault zone d2 generated low angle s2 shear zones and various slip crenulation fabrics formed by northwest directed thrust motion the d1 fabrics are inferred to be related to initiation of subduction related accretion of the nappes by orogen normal southwest northeast shortening and accretionary tectonics the subsequent d2 fabrics developed as temporally overlapping subduction related low angle thrusts in the rosario fault zone and high angle sinistral strike slip faults in the lopez fault zone in an overall transpressive setting due to oblique convergence this model suggests that the high angle lopez fault zone d2 was located above a gently northeast dipping thrust detachment s2 expressed by the rosario fault zone that allowed the accreted nappes to move parallel to the orogen the kinematic model cannot validate regional scale dextral terrane translation of the san juan thrust system as inferred by paleomagnetic data elsewhere in the western united states but addresses important tectonic processes caused by oblique subduction and changing plate conditions

chemical processes affecting the mobility of major minor and trace elements during weathering of granitic rocks abstract the behaviour of 38 major and trace elements as well as changes in the mineralogy have been examined in 10 weathering profiles developing on some portuguese granitic rocks element mobilities are calculated from geochemical data normalized with respect to ti in the fresh parent rock chemical elements are divided into two groups immobile and mobile on the basis of their geochemical distribution during weathering elements that are immobile during weathering are zr hf fe al th nb sc and the ree very mobile are ca na p k sr ba rb mg and si mobile elements are derived mainly from leachable minerals such as feldspars micas and apatites whereas immobile elements are either concentrated in resistate phases or strongly adsorbed by secondary minerals the geochemical behaviour of mn cr v fe and ce is very dependent on redox conditions redox transformations of these elements can be used to set limits on the oxidation state of a weathering suite the ree are mobilized or fractionated during late stages of weathering but not during moderate stages of weathering this fractionation is caused by selective leaching of rocks composed of both stable and unstable minerals containing ree

redox state of the archean atmosphere evidence from detrital heavy minerals in ca 3250 2750 ma sandstones from the pilbara craton australia the presence of detrital uraninite and pyrite in fluvial placers of the witwatersrand basin south africa has been used to infer low levels of atmospheric oxygen during the archean 2500 ma however recent studies advocate a hydrothermal origin for these minerals thereby limiting their value as constraints on the composition of the early atmosphere in contrast ca 3250 2750 ma fluvial siliciclastic sediments from the pilbara craton in australia have never undergone significant hydrothermal alteration and their heavy minerals are of unequivocal detrital origin these heavy minerals include the redox sensitive phases pyrite uraninite and gersdorffite along with more inert zircon rutile chromite and monazite locally siderite is a major constituent to 90 of the heavy mineral population with grains displaying evidence for several episodes of erosion rounding and subsequent authigenic overgrowth detrital siderite is very rare in post archean sandstones largely due to its instability in oxidizing environments however its frequent survival of prolonged transport in well mixed and therefore well aerated archean river waters that contained little organic matter strongly implies that the contemporary atmosphere was indeed much less oxidizing than at present moreover concentrations of reduced sulfur species must have been very low in surface fluids for siderite to survive repeated transportation events without pyritization

continent ocean transition at the western barents sea svalbard continental margin the change in crustal type at the western barents sea svalbard margin takes place over a narrow zone related to primary rift and shear structures reflecting the stepwise opening of the greenland sea regionally the margin is composed of two large shear zones and a central rifted margin segment local transtension and transpression at the plate boundary caused the early cenozoic tectonism in svalbard and the western barents sea and might explain the prominent marginal gravity and velocity anomalies

apatite weathering and the phanerozoic phosphorus cycle despite widespread debate in the literature there is still considerable uncertainty concerning which nutrient ultimately controls marine net ecosystem production nep over geologic time geochemical arguments suggest that phosphorus is the culprit the weathering of apatite the primary phosphorus sink in earth s exosphere controls long term phosphorus availability if phosphorus is the ultimate controlling nutrient over geologic time scales then long term marine nep is coupled to the release of phosphorus from apatite weathering the most abundant apatite compositions found in nature are igneous fluorapatite and marine sedimentary carbonate fluorapatite sparse data exist on how these compositions dissolve under earth s surface conditions to demonstrate a need for these data and their application we present a kinetic treatment of existing data augmented by new results we then use these results in a weathering model designed to illustrate the control exerted by temperature via activation energy and surface area on the phosphorus flux from apatite dissolution during the phanerozoic our conclusion is that activation energy and hence temperature and apatite surface area are important parameters governing the phosphorus flux from apatite weathering and therefore marine nep during phanerozoic time

the margin between senja and spitsbergen fracture zones implications from plate tectonics abstract analysis of multichannel seismic data from the continental margin off svalbard between the senja and spitsbergen fracture zones suggests that the transition between continental and oceanic crust is located at or close to the hornsund fault zone in the late paleocene early eoeene 57 m y the region between svalbard and northeast greenland was subjected to regional shear movements associated with a transform system between the young lofoten greenland basin and the arctic ocean approximately 50 m y ago the spreading axis migrated to the northeast creating a deep basin north of the greenland senja fracture zone forming the passive margin between bear island and 76 5 n north of 76 5 n the regional transform was maintained at the time of the main reorganization of relative plate motion 36 m y the northern margin evolved a continental fragment was possibly cut off from the svalbard margin forming a small microcontinent the microcontinent appears as the submarine ridge which has been associated with the hovgaard fracture zone it is suggested that the sediments west of the hornsund fault zone are not older than eocene in the south and mid oligocene in the north the position of the spreading axis has greatly influenced the margin sedimentation

tertiary tectonism and basin inversion of the st jonsfjorden region svalbard abstract deformed basement and cover rocks of the st jonsfjorden area further define the character of spitsbergen s tertiary fold and thrust belt three major thrusts comprise a folded ca n060 e directed foreland propagating thust stack with likely additional subsurface thrust faults the folded vegardbreen robertsonfjellet thrust is the most significant fault in the complex and re emerges in the core of a disrupted synclinal structure in triassic strata shortening across the area indicated from line length restoration is of the order of 13 km differences in stratigraphy between and within thrust sheets indicate the thrust stack initiated along the edge of a westward deepening carbonbiferous basin with a fault step margin and represents basin inversion early structures related to basin formation had a major control on later thrust sheet evolution and the complexity of inversion structures reflects the initial complexity of the basin geometry such basin inversion could characterize the length of the fold and thrust belt the st jonsfjorden structures are primarily contractional and together with areas farther southeast in the fold thrust belt indicate shortening took place perpendicular to the fold belt across much of the length of the evolving margin

oligocene to lower pliocene deposits of the norwegian continental shelf norwegian sea svalbard denmark and their relation to the uplift of fennoscandia a synthesis abstract this study provides the results of the first integrated study of oligocene pliocene basins around norway within the study area three main depocentres have been identified where sandy sediments accumulated throughout the oligocene to early pliocene period the depocentre in the norwegian danish basin received sediments from the southern scandes mountains with a general progradation from north to south during the studied period the depocentre in the basinal areas of the uk and norwegian sectors of the north sea north of 58 n received sediments from the scotland shetland area because of the sedimentary infilling there was a gradual shallowing of the northern north sea basin in the oligocene and miocene a smaller depocentre is identified offshore northern nordland between ranafjorden approximately 66 n and vesteralen approximately 68 n where the northern scandes mountains were the source of the oligocene to early pliocene sediments in other local depocentres along the west coast of norway sandy sedimentation occurred in only parts of the period shifts in local depocentres are indicative of changes in the paleogeography in the source areas in the barents sea and south to approximately 68 n the oligocene to early pliocene section is eroded except for distal fine grained and biogenic deposits along the western margin and on the oceanic crust this margin was undergoing deformation in a strike slip regime until the eocene oligocene transition the early oligocene sediments dated in the vestbakken volcanic province and the forlandssundet basin represent the termination of this strike slip regime the change in the plate tectonic regime at the eocene oligocene transition affected mainly the northern part of the study area and was followed by a quiet tectonic period until the middle miocene when large compressional dome and basin structures were formed in the norwegian sea the middle miocene event is correlated with a relative fall in sea level in the main depocentres in the north sea formation of a large delta in the viking graben frigg area and uplift of the north and south scandes domes in the norwegian danish basin the sorgenfrei tornquist zone was reactivated in the early miocene possibly causing a shift in the deltaic progradation towards the east a late pliocene relative rise in sea level resulted in low sedimentation rates in the main depositional areas until the onset of glaciations at about 2 7 ma when the scandes mountains were strongly eroded and became a major source of sediments for the norwegian shelf whilst the frigg delta prograded farther to the northeast

tertiary or cretaceous age for spitsbergen s fold thrust belt on the barents shelf several publications propose that main phase fold thrust development on spitsbergen was late cretaceous and not tertiary as previously thought the question of timing is crucial to models for crustal response to transpressive plate motions involvement of tertiary strata in fold thrust structures the sedimentology of the tertiary basin strata and studies of paleo stress field evolution all indicate paleocene to eocene fold thrust development during opening of the norwegian greenland oceanic basin a regional angular unconformity of 1 between paleocene and early cretaceous strata is consistently disconformable to the eye and precludes any significant older deformation in the immediate area pre unconformity deformation was likely strike slip in character and concentrated in the west the proposal for late cretaceous fold thrust belt formation is inconsistent with the geology

weathering and sediment generation in the archean an integrated study of the evolution of siliciclastic sedimentary rocks of the 3 2ga moodies group barberton greenstone belt south africa abstract alluvial and braided fluvial deposits of the 3 2 ga moodies group in the barberton greenstone belt south africa are analyzed petrographically and geochemically to identify their source rocks provenance and assess the degree and type s of weathering required to produce the observed moodies sediment compositions conglomerate sandstone and shale data give somewhat differing pictures of provenance and weathering due to derivation from different components within the source terrane and size and compositional fractionation during transport the results suggest that shale geochemistry provides the most accurate estimate provenance although both rare earth element and trace element th sc zr cr and ti data must be used in combination to give the best results the source area for moodies group sediments was dominated by tonalite felsic volcanic rock komatiite basalt and granite based on mineralogical and major element divergence from estimated source area composition the moodies group sediments are remnants of an aggressive weathering environment labile materials such as komatiite basalt and coarse plagioclase grains decomposed almost entirely to clays and solutes and the chemical index of alteration for moodies shale is well above the global average an aggressive weathering environment in the archean may have been achieved by increased rainfall higher temperatures and or higher atmospheric p c o 2 more likely a combination of these conditions worked to offset the inhibitory weathering effects of a plant free environment

mobility and fluxes of major minor and trace metals during basalt weathering and groundwater transport at mt etna volcano sicily abstract the concentrations and fluxes of major minor and trace metals were determined in 53 samples of groundwaters from around mt etna in order to evaluate the conditions and extent of alkali basalt weathering by waters enriched in magma derived co 2 and the contribution of aqueous transport to the overall metal discharge of the volcano we show that gaseous input of magmatic volatile metals into the etnean aquifer is small or negligible being limited by cooling of the rising fluids basalt leaching by weakly acidic co 2 charged water is the overwhelming source of metals and appears to be more extensive in two sectors of the s sw paterno and e zafferana volcano flanks where out flowing groundwaters are the richest in metals and bicarbonate of magmatic origin thermodynamic modeling of the results allows to evaluate the relative mobility and chemical speciation of various elements during their partitioning between solid and liquid phases through the weathering process the facts that rock forming minerals and groundmass dissolve at different rates and secondary minerals are formed are taken into account at mt etna poorly mobile elements al th fe are preferentially retained in the solid residue of weathering while alkalis alkaline earth and oxo anion forming elements as se sb mo are more mobile and released to the aqueous system transition metals display an intermediate behavior and are strongly dependent on either the redox conditions mn cr v or solid surface related processes v zn cu the fluxes of metals discharged by the volcanic aquifer of etna range from 7 0 10 3 t a th to 7 3 10 4 t a na they are comparable in magnitude to the summit crater plume emissions for a series of elements na k ca mg u v li with lithophile affinity but are minor for volatile elements basalt weathering at mt etna also consumes about 2 1 10 5 t a of magma derived carbon dioxide equivalent to ca 7 of contemporaneous crater plume emissions the considerable transport of some metals in etna s aquifer reflects a particularly high chemical erosion rate evaluated at 2 3 10 5 t a enhanced by the initial acidity of magmatic co 2 rich groundwater

a geophysical interpretation of the secular displacement and gravity rates observed at ny alesund svalbard in the arctic effects of post glacial rebound and present day ice melting summary we have analysed the ny alesund very long baseline interferometry vlbi data over the period 1994 august to 2004 may and we obtain secular displacement rates relative to a nnr nuvel 1a reference frame of 0 2 0 5 mm yr 1 1 7 0 5 mm yr 1 and 4 8 1 1 mm yr 1 for the north east and vertical directions respectively the corresponding global positioning system gps station displacement rates relative to the same reference frame for the north east and vertical directions are 0 2 0 6 mm yr 1 2 3 0 6 mm yr 1 and 6 4 1 5 mm yr 1 at nya1 and 0 1 0 5 mm yr 1 1 6 0 5 mm yr 1 and 6 9 0 9 mm yr 1 at nall where these gps rates were derived from the itrf2000 velocity solution of heflin from the comparison at 25 globally distributed collocated sites we found that the difference in uplift rate between vlbi and gps at ny alesund is mainly due to a gps reference frame scale rate error corresponding to 1 6 mm yr 1 in the gps vertical rates the uplift rate was estimated to be 5 2 0 3 mm yr 1 from the analysis of the tide gauge data at ny alesund hence the uplift rates obtained from three different kinds of data are very consistent each other the absolute gravity ag measurements at ny alesund which were carried out four times period 1998 2002 by three different fg5 absolute gravimeters lead to a decreasing secular rate of 2 5 0 9 gal yr 1 1 gal 10 8 ms 2 in this analysis the actual data obtained from a superconducting gravimeter at ny alesund were used in the corrections for the gravity tide including the ocean tide effect and for the air pressure effect we have

analysis of fault populations in western spitsbergen implications for deformation partitioning along transform margins mesoscale faults expressed in the paleogene central basin and cretaceous basement along the west spitsbergen orogenic belt are used to define the history of continental deformation associated with the development of the transform system that accompanied the opening of the eurasian basin and the norwegian greenland sea a fundamental change in the orientation of faults from dominantly north south in the basal part of the basin to northeast striking in the upper units broadly correlates with a major shift in plate motion during late paleocene early eocene time the two main populations of faults are interpreted as extension fractures that were variably reactivated as shear fractures and formed in response to north south compression followed by northeast southwest compression paleostress stratigraphy or the analysis of striated faults measured in successive stratigraphic units of the central basin corroborates this interpretation and allows a time sequence of paleostress tensors to be defined results show that a late cretaceous early paleocene north south compression consistent with plate motion was followed by three relatively short lived and regionally limited faulting events leading up to a change in plate motion during late paleocene time post chron 25 major transpressive tectonism followed producing northeast trending fractures that were reactivated as dextral and sinistral faults defining a prolate shape paleostress ellipsoid with a horizontal 1 this regionally reproducible tensor consistent with the prediction of dextral transpression along the paleotransform was probably initiated at approximately the paleocene eocene boundary finally a post early eocene deformation pervasively recorded in the study area by an oblate shape paleostress ellipsoid with horizontal 3 is tentatively correlated with the dextral transtension that characterized the post chron 13 opening of the norwegian greenland sea and eurasian basin this study offers documentation of deformation partitioning during the evolution of a transform margin the late cretaceousearliest paleocene compression associated with the prototransform did not involve substantial partitioning and a north south maximum principal stress pervaded the continental crust away from the transform in contrast the late paleocene eocene transpression reflects total partitioning of deformation along the evolved mature transform margin oblique plate motion was presumably partitioned into a strikeslip zone s offshore whereas the onshore central basin recorded only the orthogonal component of oblique convergence and divergence a pattern similar to modern orogenic belts developed in zones of oblique plate motion

eurekan transpressive deformation in the wandel hav mobile belt northeast greenland 1 besides the w e trending kap cannon thrust zone and harder fjord fault zone the 300 km long and nw se striking wandel hav mobile belt represents the third major fault zone in north greenland structural analyses in several areas of this belt suggest that compressive deformation is characterized by transpressive dextral strike slip kinematics this is demonstrated by a combination of folding around w e axes approximately north and south directed reverse faulting and dextral strike slip displacements along nw se trending fault lines the initial formation of the long linear faults is interpreted to be related to deformational events in late paleozoic triassic jurassic and late cretaceous times due to the lack of structural evidence we assume that deformations led to the generation of extension faults which probably were reactivated during dextral strike slip tectonism it is suggested that dextral transpressive deformation was coeval with n s compression at the harder fjord fault zone and cap cannon thrust zone and took place during eocene eurekan times dextral strike slip tectonism in the wandel hav mobile belt was the result of n s compression due to a general northward movement of the greenland plate as a zone of crustal weakness the belt can be interpreted as the onshore equivalent of the main transcurrent fault zone de geer fault which caused the intracontinental dextral slip of svalbard barents shelf relative to north greenland during early tertiary eurekan times and prior to their separation in this configuration it represents one part of the belt of eurekan deformation which extends from the canadian arctic islands over north greenland to the barents shelf where compressive deformation is recorded in the west spitsbergen fold and thrust belt

lineament domain of regional strike slip corridor insight from the neogene transtensional de geer transform fault in nw spitsbergen lineaments on regional scale images represent controversial features in tectonic studies published models explain the presence of the lineament domains in most geodynamic environments as resulting from the enhanced erosion along strikes normal to the upper crustal regional extension despite their success in many tectonic frameworks these models fail to explain the existing lineament domains in the regional strike slip corridors that separate regional blocks including the transform faults the present paper investigates the lineament distribution in such environments and specifically presents the results from a study along the shear corridor of the de geer transform fault in the north atlantic responsible for the separation and drifting away between northern greenland and the svalbard archipelago since oligocene times the study spans from satellite image analysis and outcrop scale investigations to a more regional analysis on a digital bathymetric model of the north atlantic arctic ocean lineaments were automatically detected in the spectral band 8 0 52 0 9 m of a landsat 7 image 15 m pixel resolution a total of 320 image lineaments were extracted from both the regional and the local scale investigations and statistically analyzed results from the multi scalar lineament analyses revealed the existence of a main n s lineament domain regionally persistent from the de geer corridor to the western margin of northern spitsbergen where it relates to the youngest post oligocene tectonics observed onshore this is confirmed by field observations showing that the n s faults represent the youngest brittle deformation system and systematically cut the deformations associated with the building of the tertiary west spitsbergen fold and thrust belt the n s lineament domain is the result of the activity of a larger regional scale tectonic feature nw se oriented and responsible for the localized extension within its deformation corridor the de geer transform fault a model is presented that involves the presence of a thin upper crust with brittle behavior lying above a deeper crustal layer characterized by a more ductile deformation the lower layer suffers more diffuse homogeneous strain this strain is transmitted to the upper brittle layer forming clusters of enhanced fracturing zones aligned following the induced stress trajectories lineaments develop along these weaker fractured zones preferentially etched by erosional processes and align perpendicular to the least horizontal compression sigma3 which in turn forms an angle to the shear kinematics in the western part of spitsbergen this angle is smaller than 45 due to the transtensional tectonic regime the proposed model for lineament domain origin in strike slip environments well integrates the existing models in literature and could be applied to other similar geodynamic contests

weathering and transport of chromium and nickel from serpentinite in the coast range ophiolite to the sacramento valley california usa abstract a soil geochemical study in northern california was done to investigate the role that weathering and transport play in the regional distribution and mobility of geogenic cr and ni which are both potentially toxic and carcinogenic these elements are enriched in ultramafic rocks primarily serpentinite and the soils derived from them 1700 10 000 mg cr per kg soil and 1300 3900 mg ni per kg soil in the coast range ophiolite chromium and ni have been transported eastward from the coast range into the western sacramento valley and as a result valley soil is enriched in cr 80 1420 mg kg 1 and ni 65 224 mg kg 1 compared to median values of u s soils of 50 and 15 mg kg 1 respectively nickel in ultramafic source rocks and soils is present in serpentine minerals lizardite antigorite and chrysotile and is more easily weathered compared to cr which primarily resides in highly refractory chromite mg fe2 cr3 al fe3 2o4 although the majority of cr and ni in soils are in refractory chromite and serpentine minerals the etching and dissolution of these minerals presence of cr and ni enriched clay minerals and development of nanocrystalline fe hydr oxides is evidence that a significant fractions of these elements have been transferred to potentially more labile phases

the eurekan deformation in the arctic an outline the evolution of the eurekan deformation zones in the arctic is closely related to the development of the circum greenland plate boundaries in early cenozoic times 53 34 ma mostly the eurekan orogeny or deformation has been interpreted as a predominantly compressive tectonic event but the eurekan deformational history in the arctic was not the result of a single tectonic episode it rather represents a complex sequence of successive tectonic stages which produced a number of intra continental deformation zones with changing sometimes opposing lateral oblique and convergent kinematics in the canadian arctic archipelago north and ne greenland and svalbard the interaction between the continental plates especially in combination with the development of transform faults resulted onshore in the formation of several complex deformation zones and areas of eurekan deformation the eurekan deformation can be divided into two major tectonic stages the first phase in the early eocene was dominated by orthogonal compression in the west spitsbergen fold and thrust belt along the west margin of the barents shelf and contemporaneous sinistral strike slip tectonics along the wegener fault and on ellesmere island whereas the second phase in the late eocene was characterized by dextral strike slip and compression on ellesmere island and contemporaneous dextral transpression and transtension along the de geer fracture zone or hornsund fault complex between ne greenland and spitsbergen

mineralogical constraints on precambrian pco2 arising from m t rosing d k bird n h sleep c j bjerrum 744 747 2010 10 1038 nature08955 rosing and others1 recently proposed a new model for the early earth s atmospheric composition they suggest on the basis of mineral assemblages in sedimentary rocks that atmospheric co2 and ch4 concentrations have been consistently overestimated this proposal is intriguing given that high concentrations of these gases are traditionally considered to be the solution to the faint young sun paradox of why the earth did not freeze over in our sun s youth when solar luminosity was greatly decreased rosing and others1 instead invoke a decreased planetary albedo during the earth s early history new insights into this problem which has long captivated those interested in the earth s early climate and biological history are welcome however we believe that the arguments presented by rosing and others1 for roughly modern values of the partial pressure of co2 are not robust

tertiary west spitsbergen fold and thrust belt on broggerhalvoya svalbard structural evolution and kinematics the tertiary fold and thrust belt on broggerhalvoya is characterized by a ne vergent pile of nine thrust sheets the basal sole thrust of the pile is located in precambrian phyllites and climbs up section to the ne the lower thrust sheets consist predominantly of post caledonian cover sediments two thrust sheets in the central part of the pile contain a syncline and anticline on a kilometer scale the kilometer scale fold is cut by juxtaposed thrusts giving rise to the formation of four structurally higher basement dominated thrust sheets a five stage kinematic model is proposed 1 in sequence foreland propagating formation of the lower thrust sheets with ramp flat geometries in response to n s subhorizontal bedding parallel movements 2 change in tectonic transport to more east northeasterly directions and first out of sequence thrusting inversion and uplift of the basement in the hinterland formation of the kilometer scale fold structure 3 truncation of the kilometer scale fold by a thrust fault and stacking of the highest basement dominated thrust sheets by hindward propagating mode of thrust generation 4 n s extension due to extensional collaps of the stack 5 w e extension the strain of the thrust sheets is predominantly compressive with the exception of the structurally highest thrust sheet reflecting a temporal change to a more transpressive regime ramping of some thrust faults is suggested to be in part controlled by reactivated carboniferous normal faults the basal sole thrust of the thrust sheet stack also follows the trend of the kongsvegen fault which showed enhanced activity during late mesozoic early tertiary extension the curvature of the west spitsbergen fold and thrust belt on broggerhalvoya is interpreted to be controlled mainly by oblique ramping on the kongsvegen fault associated with pinning on the nordfjorden block as well as by along strike lithological and thickness variations of the post caledonian strata in addition this suggests that pre existing structures have controlled the tertiary geometry the temporal change in the kinematics during thrust tectonics can be linked with the plate tectonic framework in the arctic during tertiary times

discussion on pre ocean opening compression of the northwestern atlantic margin evidence from eastern greenland journal vol 157 2000 707 710 scientific editing by nick rogers h d maher jr s bergh alvar braathen write manby lyberis 2000 argue for a cretaceous palaeocene age and a convergent setting for both the fold structures of the wandel sea basin and for the west spitsbergen fold thrust belt as an alternative to models of decoupling during palaeocene eocene transpressive motions between greenland and the barents shelf in this context we discuss evidence on the timing and kinematics of the west spitsbergen fold thrust belt and constraints on the timing of deformation in the wandel sea basin multiple lines of evidence constraining the timing of fold thrust formation in spitsbergen are discussed in maher et al 1995 and clearly indicate major fold thrust development in the palaeocene eocene space limitations prevent their description here the nature of additional late cretaceous deformation on spitsbergen is another question it is partly constrained by the unconformity at the base of the tertiary sequence which is well exposed in many places and is consistently disconformable to the eye this unconformity involves differential uplift to the north with a regional tilt of a degree or less has a character inconsistent with previous fold thrust development along the islands western margin and can be related to a second pulse within the high arctic large igneous province maher 2001 more recent work confirms a palaeocene eocene age for the spitsbergen contractional structures manby lyberis refer to blythe kleinspehn 1998 as indicating a late cretaceous age for spitsbergen fold thrust belt uplift in their summary figure blythe kleinspehn indicate uplift and erosion of source terranes initiating at 70 ma and continuing until c 43 ma six detailed thermal histories generated from track length modelling of samples taken from the tertiary foreland basin sediments provide particular insight as the authors note three samples with depositional ages of

chromium geochemistry in serpentinized ultramafic rocks and serpentine soils from the franciscan complex of california weathering of ultramafic rocks and serpentinites in the franciscan complex of california produces serpentine soils containing high concentrations of cr as well as other potentially toxic elements including ni co and mn chromium concentrations in serpentine soils from jasper ridge biological preserve in the central coast range are as high as 4 760 mg kg 1 nearly three times greater than the serpentinite protolith 1800 mg kg 1 chromium containing minerals within the bedrock include chlorite 0 3 cr wt enstatite 0 4 cr wt augite 0 7 cr wt chromite 10 8 cr wt magnetite 8 2 10 3 cr wt and an ultra fine grained mixture of spinel and a silicate phase containing 13 3 cr weight percent chromium concentrations in serpentine soil profiles fluctuate between 1 725 to 4 760 mg kg 1 and do not correspond to variations in soil ph organic carbon or electrical conductivity the enrichment and variability of soil cr is directly related to the modal abundance and weathering of chromite cr magnetite and the spinel silicate mixture by comparison cr silicates account for

tectonic inversion in the wandel sea basin a new structural model of kilen eastern north greenland the seminunatak kilen in eastern north greenland with its complexly deformed carboniferous cretaceous strata is a key area to understand the tectonic history of the transform plate boundary between eastern north greenland and svalbard detailed 3 d geological mapping from oblique photogrammetry along with limited ground fieldwork and interpretation of previously published data forms the basis for a new structural model of kilen previous structural models interpreted rhombic shaped fault patterns as the evidence for strike slip tectonics these structures are here interpreted to be the result of a post coniacian ne sw extension with nw se trending normal faults followed by later n s compression of presumable paleocene eocene age folding the faults passively and suggesting the presence of a basal detachment furthermore two thrust sheets have been distinguished on kilen a lower kilen thrust sheet and an upper hondal elv thrust sheet separated by a subhorizontal fault the central detachment the style of deformation and the structures described are interpreted as the result of paleocene eocene n s directed compression resulting in basin inversion with strike slip faults only having minor status this indicates that the greenland margin as exposed on kilen and the conjugate svalbard margin in the west spitsbergen fold and thrust belt are more similar than previously anticipated

svartfjella eidembukta and daudmannsodden lineament tertiary orogen parallel motion in the crystalline hinterland of spitsbergen s fold thrust belt within metamorphic basement rocks of the hinterland of spitsbergen s tertiary fold thrust belt a 35 km long zone of notably deformed carboniferous strata and cretaceous intrusives forms a major orogen parallel lineament from svartfjella to eidembukta to daudmannsodden sedl orientations and geometries of map scale fault duplexes and associated fault plane striae populations of folds and associated cleavage and of tension gashes all indicate orogen parallel motion occurred along the sedl structural analyses indicates three phases 1 ene directed overthrusting 2 sinistral motion with a backthrust component and 3 dextral strike slip motion this history indicates a change from orogen perpendicular to orogen parallel movements orogen parallel movement was likely coeval with orogen perpendicular fold thrust transport to the ene in the foreland a model where dextral transpressive motion between greenland and svalbard was decoupled explains the hinterland foreland difference basement fabric aligned with carboniferous carbonates on the steep foreland face of an antiformal stack provided a through going weak surface a prerequisite for decoupling sinistral orogen parallel motion is explicable by short lived episode of sinistral plate motion or by local wedge extrusion during dextral transpression the evolution of decoupling patterns has significant implications for deducing plate motions from local kinematic and paleostress studies

thrust tectonics on broggerhalvoya and their relationship to the tertiary west spitsbergen fold and thrust belt the tertiary fold and thrust belt on broggerhalvoya is characterized by a ne vergent pile of nine thrust sheets the sole thrust of the pile is located in precambrian phyllites and climbs up section to the northeast four lower thrust sheets consisting predominantly of upper palaeozoic sediments are overlain by two thrust sheets in the central part of the stack which contain a kilometre scale syncline and anticline the fold is cut by juxtaposed thrusts giving rise to the formation of three structurally higher basement dominated thrust sheets a multiple stage kinematic model is proposed including 1 in sequence foreland propagating formation of the lower thrust sheets in response to n s subhorizontal bedding parallel movements 2 a change in tectonic transport to ene and out of sequence thrusting and formation of the kilometre scale fold structure followed by 3 truncation of the kilometre scale fold and stacking of the highest basement dominated thrust sheets by hind ward propagating out of sequence thrusting the strain of the thrust sheets is predominantly compressive with the exception of the structurally highest thrust sheets reflecting a temporal change to a more transpressive regime thrusting was followed by 4 n s extension and 5 w e extension comparison of the structural geometry and kinematic evolution of broggerhalvoya with the data reported for the fold belt further south allows us to assume a coeval evolution with the fold belt a latest paleocene early eocene age for the main phase of thrusting is suggested for the west spitsbergen fold and thrust belt the main phases therefore pre date the separation of svalbard and greenland due to right lateral movements along the hornsund fault zone the fold belt s temporal evolution followed by the formation of the forlandsundet graben can be linked with the plate kinematic framework in the span between latest paleocene and middle eocene times

lateral asthenospheric viscosity variations and postglacial rebound a case study for the barents sea the effect of lateral asthenospheric viscosity variations on observable signatures related to postglacial rebound in the barents sea is studied using a finite element approach to discretize the problem a comparison between a laterally homogeneous reference earth model and a laterally heterogeneous earth model is performed the results indicate that a change in asthenospheric viscosity of about three orders of magnitude influences predictions of land uplift up to 10 20 m present day velocities up to 0 5 1 5 mm a and present day gravity anomalies up to 0 4 0 8 mgal in the northwestern part of the barents sea region

faint young sun problem more severe due to ice albedo feedback and higher rotation rate of the early earth 1 during the archean 3 8 2 5 billion years ago the sun was up to 25 less luminous than today yet there is strong evidence that the earth s ocean surface was not completely frozen the most obvious solutions to this faint young sun problem demand high concentrations of greenhouse gases such as carbon dioxide here we present the first comprehensive 3 dimensional simulations of the archean climate that include processes as the sea ice albedo feedback and the higher rotation rate of the earth these effects lead to co2 partial pressures required to prevent the earth from freezing that are significantly higher than previously thought for the early archean we find a critical co2partial pressure of 0 4 bar in contrast to 0 06 bar estimated in previous studies with 1 dimensional radiative convective models our results suggest that currently favored greenhouse solutions could be in conflict with constraints emerging for the middle and late archean

geologic framework of the northern north carolina usa inner continental shelf and its influence on coastal evolution abstract the inner continental shelf off the northern outer banks of north carolina was mapped using sidescan sonar interferometric swath bathymetry and high resolution chirp and boomer subbottom profiling systems we use this information to describe the shallow stratigraphy reinterpret formation mechanisms of some shoal features evaluate local relative sea levels during the late pleistocene and provide new constraints via recent bedform evolution on regional sediment transport patterns the study area is approximately 290 km long by 11 km wide extending from false cape virginia to cape lookout north carolina in water depths ranging from 6 to 34 m late pleistocene sedimentary units comprise the shallow geologic framework of this region and determine both the morphology of the inner shelf and the distribution of sediment sources and sinks we identify pleistocene sedimentary units beneath diamond shoals that may have provided a geologic template for the location of modern cape hatteras and earlier paleo capes during the late pleistocene these units indicate shallow marine deposition 15 25 m below present sea level the uppermost pleistocene unit may have been deposited as recently as marine isotope stage 3 although some apparent ages for this timing may be suspect paleofluvial valleys incised during the last glacial maximum traverse the inner shelf throughout the study area and dissect the late pleistocene units sediments deposited in the valleys record the holocene transgression and provide insight into the evolutionary history of the barrier estuary system in this region the relationship between these valleys and adjacent shoal complexes suggests that the paleo roanoke river did not form the albemarle shelf valley complex as previously proposed a major fluvial system is absent and thus makes the formation of this feature enigmatic major shoal features in the study area show mobility at decadal to centennial timescales including nearly a kilometer of shoal migration over the past 134 yr sorted bedforms occupy 1000 km 2 of seafloor in raleigh bay and indicate regional sediment transport patterns between capes hatteras and lookout that help explain long term sediment accumulation and morphologic development portions of the inner continental shelf with relatively high sediment abundance are characterized by shoals and shoreface attached ridges and where sediment is less abundant the seafloor is dominated by sorted bedforms these relationships are also observed in other passive margin settings suggesting a continuum of shelf morphology that may have broad application for interpreting inner shelf sedimentation patterns

a transpressional origin for the west spitsbergen fold and thrust belt insight from analog modeling 1 the west spitsbergen fold and thrust belt formed along the transform plate boundary between greenland and the western barents sea during paleocene eocene breakup in the northern north atlantic approximately 20 40 km margin perpendicular shortening accumulated in the belt has been attributed to transpression and strain partitioning in a restraining bend but also to head on collision we have applied scaled analog tectonic modeling to test the former hypothesis a pack of brittle quartz sand with a shallow thin layer of silicon putty was deformed by transpression at a 15 convergence angle by movement of a basal plate the kinematics was quantified by means of digital particle image velocimetry the result was a doubly vergent transpressional wedge consisting of a steeply tapered retrowedge and a strongly internally deformed steeply tapered prowedge separated by a central strike slip zone and an adjacent low taper thin skinned fold and thrust belt the doubly vergent wedge evolved through several kinematic phases three main stages were identified namely 1 initial distributed deformation 2 development of an oblique doubly vergent wedge with progressive evolution of local strain partitioning along the marginal shear zones and finally 3 a stage of full strain partitioning between a central strike slip zone and reverse displacement along marginal shear zones with folding and thrusting in a thin skinned belt on the proside the analog model convincingly reproduced the geometry and the kinematic evolution of the west spitsbergen fold and thrust belt supporting the hypothesis of its formation by strain partitioning in transpression with a small angle of convergence and significant lateral displacement

graben inversion in nature and experiments the inversion of crustal scale basement grabens is studied here through laboratory experiments on small scale models and available oil industry seismic lines from the southern north sea two basic configurations are considered first both the basement and the sedimentary cover are brittle and inversion does not involve any potential decollement between them second the basement and sedimentary cover are separated by a weak ductile layer e g salt which can allow decollement of the cover during both extension and later compression and inversion the second configuration is more complicated and can lead to a large variety of geological structures laboratory experiments were carried out on brittle ductile models built with sand to represent brittle layers basement and sedimentary cover and silicone putty to simulate the decollement layer between basement and cover a mechanically based classification of inversion structures is proposed the effects of some crucial parameters are investigated including obliquity between the direction of shortening and normal faults as well as strength profiles and the presence or absence of salt diapirs the experimental investigation leads to the following conclusions 1 the inversion of the graben by reactivation of normal faults implies that the angle between the direction of compression and the graben is less than 45 2 if there is a superficial decollement e g basement cover interface inversion initiates low dipping thrust faults in the cover localized at graben borders 3 salt diapirs or salt walls localized along the graben borders in the cover are preferential sites for the development of thrust faults and 4 when the cover is decoupled from the basement by a decollement layer inversion induced deformation in the cover which is partitioned between thrust faults along the graben borders and strike slip faults within the graben trending oblique to the graben borders experimental results are compared with field examples in particular from the southern north sea

tectonic wedges geometry and kinematic interpretation abstract the geometry of several tectonic wedge combinations was studied in an outcrop in the basque basin western pyrenees three types of tectonic wedges were distinguished simple double and triple wedge on the surface the geometry of the observed tectonic wedges is always highly elemental emergent thrust horse or klippe the final stage in the evolution of a tectonic wedge is its delamination this can occur by the spreading of the thrusts which conform the wedge or by the development of back thrusts associated to them the relative age of the back thrust with respect to the thrust indicates whether the original structure was a simple thrust or a tectonic wedge if this criterion is applied to the pyrenean orogen this range corresponds to a tectonic wedge

mobility of nutrients and trace metals during weathering in the late archean abstract the evolution of the geosphere and biosphere depends on the availability of bio essential nutrients and trace metals consequently the chemical and isotopic variability of trace elements in the sedimentary record have been widely used to infer the existence of early life and fluctuations in the near surface environment on the early earth particularly fluctuations in the redox state of the atmosphere in this study we applied late archean weathering models hao et al 2017 developed to estimate the behavior of major elements and the composition of late archean world average river water to explore the behavior of nutrient and trace metals and their potential for riverine transport we focused on p mn cr and cu during the weathering of olivine basalt in our standard late archean weathering model pco2 g 10 1 5 bars ph2 g 10 5 0 bars crustal apatite was totally dissolved by the acidic rainwater during weathering our model quantitatively links the pco2 g of the atmosphere to phosphate levels transported by rivers the development of late archean river water ph 6 4 resulted in riverine phosphate of at least 1 7 molar much higher than at the present day at the end of the early proterozoic snowball earth event when pco2 g could be 0 01 0 10 bars river water may have transported up to 70 molar phosphate depending on the availability of apatite thereby stimulating high levels of oxygenic photosynthesis in the marine environment crustal levels of mn in olivine dissolved completely during weathering except at large extents of weathering where mn was stored as a component of a secondary carbonate mineral the corresponding mn content of river water about 1 2 molar is higher than in modern river water whiffs of 10 5 mole o2 gas or hno3 kg 1 h2o resulted in the formation of pyrolusite mno2 and abundant hematite and simultaneous dramatic decreases in the concentration of mn ii in the river water chromite dissolution resulted in negligible dissolved cr in archean river water however amorphous cr oh 3 representing easily weatherable cr bearing minerals dissolved totally during the weathering simulations resulting in concentrations of cr iii in the river water of up to 0 14 molar higher than at the present day late archean weathering of accessory chalcopyrite produced chalcocite and bornite and extremely low concentrations of cu 10 15 molar because of the low solubilities of the copper sulfides however pulses of either o2 g or hno3 produced native copper chalcocite and bornite much more hematite and river water containing levels of dissolved cu comparable to the present day copper mineralogy predicted by weathering models might provide a new correlation with evidence from studies of copper mineral evolution overall our results implied that the redox state of the atmosphere the ph of surface waters and the availability of easily weatherable minerals are all important factors controlling the dissolution of trace elements in river water interpretation of the sedimentary signatures of trace elements should consider not only the redox state but also the ph and availability of accessory minerals

transform normal extension and asymmetric basins an alternative to pull apart models continental transforms are commonly associated with relatively small scale pull apart basins however much larger scale basins which are not consistent with the pull apart model commonly exist adjacent to transforms structures associated with several basins along the dead sea rift and el pilar fault illustrate this these basins are remarkably asymmetric bounded by essentially linear transform segments on one side and subparallel normal faults on the other suggesting simultaneous strike slip motion and transform normal extension this observation which is incompatible with classical faulting theory can be explained along divergent plate boundaries if the transform fault is much weaker than the adjacent crust analysis of the orientation of the horizontal principal stress direction near a weak transform fault embedded in an otherwise strong crust shows that convergent and divergent plate motion results in a stress field characterized by nearly fault normal compression and extension respectively structural styles along the san andreas dead sea and el pilar transform systems show that predictable changes between these two states have occurred through time along strike of the transforms

element mobility patterns record organic ligands in soils on early earth considerable mobilization of fe without mobilization of al in precambrian paleosols has been documented and attributed to either anoxic or ligand promoted dissolution to elucidate these mechanisms basalt was dissolved under oxic and anoxic conditions with and without citrate and the mobility of several elements was analyzed the extent of release of fe and p was minor in citrate free conditions or considerable with citrate regardless of oxygen pressure release of al was minor in all cases whereas release of cu was minor in anoxic conditions or considerable in oxic conditions release of cu was enhanced by citrate in comparison in the weathered surface of two of the oldest known basalt derived paleosols the mount roe 2 76 ga and the hekpoort 2 25 ga fe and p were considerably depleted and al retained consistent with the presence of organic ligands cu retained in the mount roe paleosol but considerably mobilized in the hekpoort paleosol documents formation under an anoxic atmosphere and an oxic atmosphere respectively as inferred by others on the basis of fe mobility the immobility of al in both paleosols is consistent with formation under conditions in which the annual volume of rainwater was lower than the topsoil pore volume mobilization of p in such paleosols developed under low rainfall conditions provides a new proxy for identification of ligands secreted by terrestrial organisms on early earth