geometric analysis of fold development in overthrust terranes abstract fault bend folding fault propagation folding and detachment or decollement folding are three distinct scenarios for fold thrust interaction in overthrust terranes simple kink hinge models are used to determine the geometric associations implicit in each scenario bedding maintains constant thickness in the models except in the forelimb of the fold the forelimb is allowed to thicken or thin without limit the models address individual folds and the calculated fold geometries are balanced structures each mode of fold thrust interaction has a distinct set of geometric relationships final fold geometry is adequate in itself to discern many fault bend folds this is not the case for fault propagation and detachment folds these two fold forms have very similar geometric relationships some knowledge of the nature of the underlying thrust or decollement zone is usually needed to distinguish between them the geometry of a fold is altered in a predictable fashion by transport through an upper ramp hinge and by fault parallel shearing of the structure the shearing results in a tighter fold whereas transport through the ramp hinge produces a broader fold the viability of the geometric analysis technique is demonstrated through its application to a pair of detachment folds from the canadian cordillera the geometric analysis is also used to evaluate cross sections through subsurface structures in an example from the turner valley oil field the analysis indicates how the interpretation should be altered so as to balance the cross section the analysis reveals hidden assumptions and specific inconsistencies in structural interpretations

analysis of folding by superposition of strain patterns abstract two methods have been developed in this paper to model the strain state and the layer geometry of folds these methods analyse the superposition of strain patterns due to layer shortening tangential longitudinal strain flexural flow and fold flattening the first method multiplies the deformation gradients of these strain patterns to model the successive superposition of mechanisms the second method is more general and is based on the transformation of points from the initial configuration to deformed points according to the geometrical properties of the folding mechanisms involved this method simulates the simultaneous and successive superposition of strain patterns both methods generate graphic outputs that describe the strain variation through the folded layer another application of these methods is to attempt to find theoretical folds that fit natural or experimental folds and to perform a geometric and kinematical analysis of these folds knowledge of the shape of the folded layer and the cleavage pattern is the most common basic information available in natural folds that can be used to perform the analysis additional strain data from the folded rocks are valuable for improving knowledge of the kinematical mechanisms involved in the folding

constraints on the depth and thermal vigor of melting in the martian mantle studies of rocks in gale crater and clasts within the martian meteorite breccia northwest africa nwa 7034 and paired stones have expanded our knowledge of the diversity of igneous rocks that make up the martian crust beyond those compositions exhibited in the meteorite collection or analyzed at any other landing site therefore the magmas that gave rise to these rocks may have been generated at significantly different conditions in the martian mantle than those derived from previously studied rocks here we build upon our previous models of basalt formation based on rocks analyzed in gusev crater and meridiani planum to the new models of basalt formation for compositions from gale crater and a clast in meteorite nwa 7034 estimates for the mantle potential temperature tp based on noachian age rock analyses in gale crater gusev crater and bounce rock in meridiani planum and a vitrophyre clast in nwa 7034 are within error which suggests that the calculated average tp of 1450 70 c may represent an average global mantle temperature during the noachian the tp estimates for the hesperian and amazonian based on orbital analyses of the chemistry of the crust are lower in temperature than our estimates for the noachian which is consistent with simple convective cooling of the interior of mars however the tp estimates from the young meteorites are significantly higher than the estimates based on surface chemistry and are consistent with localized hot spot melting and not heating up of the interior

temperature reconstructions from tree ring densities overestimate volcanic cooling the fidelity of inferences on volcanic cooling from tree ring density records has recently come into question with competing claims that temperature reconstructions based on tree ring records underestimate cooling due to an increased likelihood of missing rings or overestimate cooling due to reduced light availability accentuating the response here we test these competing hypotheses in the latitudes poleward of 45 n using the two eruptions occurring between 1850 and 1960 with large scale northern hemisphere climatic effects novarupta 1912 and krakatau 1883 we find that tree ring densities overestimate postvolcanic cooling with respect to instrumental data probability 0 99 with larger magnitudes of bias where growth is more limited by light availability prob 0 95 using a methodology that allows for direct comparisons with instrumental data our results confirm that high latitude tree ring densities record not only temperature but also variations in light availability

drought reconstructions for the continental united states abstract the development of a 2 lat 3 long grid of summer drought reconstructions for the continental united states estimated from a dense network of annual tree ring chronologies is described the drought metric used is the palmer drought severity index pdsi the number of grid points is 154 and the reconstructions cover the common period 1700 1978 in producing this grid an automated gridpoint regression method called point by point regression was developed and tested in so doing a near optimal global solution was found for its implementation the reconstructions have been thoroughly tested for validity using pdsi data not used in regression modeling in general most of the gridpoint estimates of drought pass the verification tests used in addition the spatial features of drought in the united states have been faithfully recorded in the reconstructions even though the method of reconstruction is not explicitly spatial in its design the drought reconstructions show that the 1930s dust bow

estimating the detachment depth in cross sections involving detachment folds this paper evaluates four different methods that have been proposed for the estimation of the detachment depth beneath detachment folds guidelines are presented in order to use the most suitable method in a particular region deformed by detachment folds these guidelines are constructed considering the assumptions of each method the influence of different parameters on the estimation of the detachment depth folding mechanisms cross sectional area variations position and orientation of the regional datum number of stratigraphic horizons bed length and thickness dip and position of the bounding lines initial thickness of the ductile unit single anticlines or fold trains and the available data ductile unit thickness regional datum detachment depth moreover a new simple method based on two previous methods is presented the advantages of this new method are that the calculations are extremely simple and it uses information from more than one stratigraphic horizon therefore it does not depend strongly on the accuracy of the data at one level the precision of the proposed methods is tested by their application to a number of natural and experimental single anticlines and fold trains it appears that better predictions are obtained when analysing a complete detachment fold train than when dealing with a single detachment anticline the reason might be that ductile material flow beneath the folds along the cross sectional plane is taken into account when dealing with a long enough cross section we also suggest some hypotheses concerning what the shape and dimensions of the detachment folds indicate about the detachment depth in those cases where insufficient data are available to apply the methods proposed

strain paths of three small folds from the appalachian valley and ridge maryland structural analysis indicates that for a given set of conditions subtle differences in layer configuration and rheology can result in major differences in fold kinematics we studied three hand sample scale folds from the maryland valley and ridge province in an effort to understand the accommodation of folding on meso and microscopic scales and to constrain the deformation histories of the folds sampled two single layer folds and one multilayer fold were taken from two nearby outcrops of the wills mountain anticline and are therefore interpreted to have developed under virtually identical pressure and temperature conditions although all three folds are dominated by carbonate material structural fabrics are unique for each fold indicating rheological contributions to and local structural control of fabric development both single layer folds have asymmetric vein distributions that are consistent with strain directions expected from asymmetric flexural flow slickenlines on one sample and cleavage in an adjacent layer in the other sample support this interpretation the first of these folds appears to have undergone late stage hinge tightening as evidenced by the development of crosscutting bed normal stylolites in contrast veins stylolites and the intracrystalline deformation in the multilayer fold are suggestive of symmetric tangential longitudinal strain followed by heterogeneous sub horizontal flattening the three folds are interpreted to be buckle folds with differing mechanisms accommodating strain within the competent layers

palinspastic reconstruction of structure maps an automated finite element approach with heterogeneous strain existing methods for the palinspastic reconstruction of structure maps do not adequately account for heterogeneous rock strain and hence cannot accurately treat features such as fault terminations and non cylindrical folds we propose a new finite element formulation of the map reconstruction problem that treats such features explicitly in this approach a model of the map surface with internal openings that honor the topology of the fault gap network is constructed of triangular finite elements both model building and reconstruction algorithms are guided by rules relating fault gap topology to the kinematics of fault motion and are fully automated we represent the total strain as the sum of a prescribed component of locally homogeneous simple shear and a minimum amount of heterogeneous residual strain the region within which a particular orientation of simple shear is treated as homogenous can be as small as an individual element or as large as the entire map for residual strain calculations we treat the map surface as a hyperelastic membrane a globally optimum reconstruction is found that unfolds the map while faithfully honoring assigned strain mechanisms closes fault gaps without overlap or gap and imparts the least possible residual strain in the restored surface the amount and distribution of the residual strain serves as a diagnostic tool for identifying mapping errors the method can be used to reconstruct maps offset by any number of faults that terminate branch and offset each other in arbitrarily complex ways

sequential restoration and unstraining of structural cross sections applications to extensional terranes we restore cross sections using a strain minimization strategy that concentrates displacement on known faults and on slip systems within fault blocks growth strata are used to sequentially restore cross sections and the misfit of rigidly restored fault blocks is used to determine the internal strain within each fault block texture mapping allows data e g seismic profile photograph of an analog model or outcrop to be imaged onto the restored state and the image is translated rotated and unstrained during the restoration growth strata are stripped layer by layer to sequentially restore a cross section this approach determines the history of deformation including the activity of faults and the internal strain accumulated during each growth increment during each increment of growth a cross section is initially restored to a horizontal datum assuming that deformation is by rigid body translations and rotations of fault blocks fault blocks are unstrained by dividing them into smaller triangular elements that accommodate the internal deformation within each fault block translations and rotations of the smaller rigid elements within each fault block produce a least squares minimized best fit after attaining a best fit of rigid elements continuity is regained by moving initially coincident triangle vertices to a common centroid the change in shape of the triangular elements in regaining continuity is a measure of strain at that location assuming homogeneous strain within each triangular element sequential restoration and unstraining determines the spatial variation and temporal evolution of strain orientations and magnitudes calculated at each vertex during each increment of restoration the method is tested on an analog sandbox model of deformation in the hanging wall of a listric normal fault and on two seismic profiles a listric normal fault system from the gulf of mexico and a graben developed over salt from the north sea the sequential restoration accurately determines the sequence of faulting in the analog model and provides insights into the development of the natural examples the restoration method determines the orientations and magnitudes of strain which can be used to predict the orientation intensity and timing of small scale deformation features

what have we learnt from palaeoclimate simulations there has been a gradual evolution in the way that palaeoclimate modelling and palaeoenvironmental data are used together to understand how the earth system works from an initial and largely descriptive phase through explicit hypothesis testing to diagnosis of underlying mechanisms analyses of past climate states are now regarded as integral to the evaluation of climate models and have become part of the toolkit used to assess the likely realism of future projections palaeoclimate assessment has demonstrated that changes in large scale features of climate that are governed by the energy and water balance show consistent responses to changes in forcing in different climate states and these consistent responses are reproduced by climate models however state of the art models are still largely unable to reproduce observed changes in climate at a regional scale reliably while palaeoclimate analyses of state of the art climate models suggest an urgent need for model improvement much work is also needed on extending and improving palaeoclimate reconstructions and quantifying and reducing both numerical and interpretative uncertainties

internal structure and kinematics of variscan thrust sheets in the valley of the trubia river cantabrian zone nw spain regional tectonic implications the variscan belt in western europe shows an arcuate geometry that is usually named ibero armorican arc the nucleus of this arc known as the asturian arc comprises the cantabrian zone which is a foreland fold and thrust belt the trubia river area is located in the inflexion zone of the asturian arc which is a strategic structural position for unraveling the geometry and kinematics of the variscan thrust sheets and related folds geological mapping construction of stratigraphic and structural cross sections analysis of kinematic indicators and estimate of shortening for each cross section have been carried out this area consists of two major antiform synform pairs related to two imbricate thrust systems these folds are asymmetric tight and their axial traces follow the trend of the asturian arc they have been interpreted as fault propagation folds the emplacement directions measured in the trubia river area change from north to south and converge towards the core of the asturian arc the minimum shortening estimated ranges between 16 4 and 17 6 km which corresponds to 56 9 and 59 4 the complex cross cutting relationships between folds and thrusts suggest that in general the different structural units followed a forward breaking sequence of emplacement with some breaching and a few out of sequence thrusts the analysis of the transport vectors together with the disposition of the fold axes and post thrusting faults that deform the thrust stack are evidence of a late deformation event that is partially or totally responsible for the arcuate form of the asturian arc the timing of the asturian arc amount of shortening and sequence of emplacement of the structures are in accordance with previous regional studies of the cantabrian zone

martian water stored underground why did mars lose so much of its surface water whereas earth retained its models of the evolution of minerals on the two planets suggest one explanation the martian water was drawn into the planetary interior why did mars lose so much of its surface water whereas earth retained its models of the evolution of minerals on the two planets suggest one explanation the martian water was drawn into the planetary interior

predicting strain using forward modelling of restored cross sections application to rollover anticlines over listric normal faults a strategy to predict strain across geological structures based on previous techniques is modified and evaluated and a practical application is shown the technique which employs cross section restoration combined with kinematic forward modelling consists of restoring a section placing circular strain markers on different domains of the restoration and forward modelling the restored section with strain markers until the present day stage is reached the restoration algorithm employed must be also used to forward model the structure the ellipses in the forward modelled section allow determining the strain state of the structure and may indirectly predict orientation and distribution of minor structures such as small scale fractures the forward model may be frozen at different time steps different growth stages allowing prediction of both spatial and temporal variation of strain the method is evaluated through its application to two stages of a clay experiment that includes strain markers and its geometry and deformation history are well documented providing a strong control on the results to demonstrate the method s potential it is successfully applied to a depth converted seismic profile in the central sumatra basin indonesia this allowed us to gain insight into the deformation undergone by rollover anticlines over listric normal faults

regional tree growth and inferred summer climate in the winnipeg river basin canada since ad 1783 a network of 54 ring width chronologies is used to estimate changes in summer climate within the winnipeg river basin canada since ad 1783 the basin drains parts of northwestern ontario northern minnesota and southeastern manitoba and is a key area for hydroelectric power production most chronologies were developed from pinus resinosa and p strobus with a limited number of thuja occidentalis picea glauca and pinus banksiana the dominant pattern of regional tree growth can be recovered using only the nine longest chronologies and is not affected by the method used to remove variability related to age or stand dynamics from individual trees tree growth is significantly but weakly correlated with both temperature negatively and precipitation positively during summer simulated ring width chronologies produced by a process model of tree ring growth exhibit similar relationships with summer climate high and low growth across the region is associated with cool wet and warm dry summers respectively this relationship is supported by comparisons with archival records from early 19th century fur trading posts the tree ring record indicates that summer droughts were more persistent in the 19th and late 18th century but there is no evidence that drought was more extreme prior to the onset of direct monitoring

low frequency temperature variations from a northern tree ring density network we describe new reconstructions of northern extratropical summer temperatures for nine subcontinental scale regions and a composite series representing quasi northern hemisphere temperature change over the last 600 years these series are based on tree ring density data that have been processed using a novel statistical technique age band decomposition designed to preserve greater long timescale variability than in previous analyses we provide time dependent and timescale dependent uncertainty estimates for all of the reconstructions the new regional estimates are generally cooler in almost all precalibration periods compared to estimates obtained using earlier processing methods particularly during the 17th century one exception is the reconstruction for northern siberia where 15th century summers are now estimated to be warmer than those observed in the 20th century in producing a new northern hemisphere series we demonstrate the sensitivity of the results to the methodology used once the number of regions with data and the reliability of each regional series begins to decrease we compare our new hemisphere series to other published large regional temperature histories most of which lie within the 1 confidence band of our estimates over most of the last 600 years the 20th century is clearly shown by all of the palaeoseries composites to be the warmest during this period

a well verified multiproxy reconstruction of the winter north atlantic oscillation index since a d 1400 abstract a new well verified multiproxy reconstruction of the winter north atlantic oscillation nao index is described that can be used to examine the variability of the nao prior to twentieth century greenhouse forcing it covers the period a d 1400 1979 and successfully verifies against independent estimates of the winter nao index from european instrumental and noninstrumental data as far back as 1500 the best validation occurs at interannual timescales and the weakest at multidecadal periods this result is a significant improvement over previous proxy based estimates which often failed to verify prior to 1850 and is related to the use of an extended reconstruction model calibration period that reduced an apparent bias in selected proxies associated with the impact of anomalous twentieth century winter nao variability on climate teleconnections over north atlantic sector land areas although twentieth century nao variability is somewhat unusual comparable periods of persistent positive phase

cross section restoration a tool to simulate deformation application to a fault propagation fold from the cantabrian fold and thrust belt nw iberian peninsula simulation of deformation in sections across tectonic structures can provide important information about the present day state of such structures a technique for simulation of deformation based on cross section restoration is presented the deformation parameters are calculated through a model that provides information in numerical format and the results are illustrated overlapping gridded images and diagrams on top of the sections across the structures in order to visualize their geological significance the validity of this method has been proved through its application to a structure formed in a contractional regime the structure analyzed is located in the cantabrian mountains nw iberian peninsula and consists of a fault propagation fold made up of carboniferous limestones the excellent outcrop of this structure allowed a complete geological cross section reconstruction and a detailed structural and kinematic analysis in order to obtain an accurate restoration the results furnished by the restoration technique about the deformation values and patterns are in agreement with small scale structures observed in the field as well as with the geometry and kinematics of the structure

chronologic modeling of faulted and fractured reservoirs using geomechanically based restoration technique and industry applications we have developed a geomechanically based restoration method to model reservoir deformation the approach founded on the finite element method simulates the physical behavior of the rock mass and considers heterogeneous material properties bedding slip and the mechanical interaction of faults to demonstrate the method s potential we analyze the deformation and fault growth in the hanging wall of a synsedimentary listric normal fault from a sand box model which provides an analog for evaluating complex faulted reservoirs the numerical model results are then analyzed to investigate the chronology of faulting the numerical model corresponds well to the physical model and provides additional insights about reservoir evolution and deformation the approach is also tested on a natural example of folding using outcrop data to study contractional deformation these examples illustrate how undetected faults and fractures reservoir compartmentalization hydrocarbon migration pathways and hydrocarbon traps can be understood in the context of tectonic processes and how this understanding can be exploited in decision making and reducing risk we conclude that the geomechanically based restoration of faulted and fractured reservoirs has significant potential for industry applications compared to common geometric restoration techniques which lack a mechanical basis

underestimation of volcanic cooling in tree ring based reconstructions of hemispheric temperatures a large volcanic eruption in ad 1258 1259 is expected to have caused substantial climate cooling but evidence for this effect is absent from tree ring based temperature reconstructions numerical modelling of tree growth shows that the lack of cooling is probably an artefact caused by low sensitivity to cooling in trees growing near the treeline

meteoritic evidence for a previously unrecognized hydrogen reservoir on mars abstract fluvial landforms on mars suggest that it was once warm enough to maintain persistent liquid water on its surface the transition to the present cold and dry mars is closely linked to the history of surface water yet the evolution of surficial water is poorly constrained based on in situ hydrogen isotope d h analyses of quenched and impact glasses in martian meteorites we provide evidence for the existence of a distinct but ubiquitous water ice reservoir d h 2 3 times earth s ocean water that lasted from at least the time when the meteorites crystallized 173 472 million years ago to the time they were ejected by impacts 0 7 3 3 million years ago but possibly much longer the origin of this reservoir appears to predate the current martian atmospheric water d h 5 6 times earth s ocean water and is unlikely to be a simple mixture of atmospheric and primordial water retained in the martian mantle d h earth s ocean water this reservoir could represent hydrated crust and or ground ice interbedded within sediments our results corroborate the hypothesis that a buried cryosphere accounts for a large part of the initial water budget of mars

sequences of thrusts and displacement transfer in the superposed duplexes of the esla nappe region cantabrian zone nw spain abstract in a cross section through the southern arm of the cantabrian zone several duplexes have been identified below the esla nappe which is the uppermost and main thrust sheet of the area the folds deforming the esla nappe are culmination walls linked to frontal and lateral ramps belonging to the lower thrust sheets the thrust sequence can be established on the basis of quantitative analysis of displacement transfer and out of sequence thrusting the primitive footwall ramps of the esla nappe region were often subsequently broken by decollements developed in successively lower stratigraphic levels of these footwalls the kinematics of the lowest duplex are more complicated than those of typical duplexes described elsewhere some thrusts transfer only part of their displacement to the roof thrust while the remaining part is accommodated along the higher thrusts of previously emplaced duplexes cutting out of sequence one or more floor or roof thrusts cumulative displacement of the thrusts in this region is about 90 km giving a present thickness 3 times that of the original pre orogenic sequence together with a translation of at least 60 km for the synorogenic basin

dielectric map of the martian northern hemisphere and the nature of plain filling materials 1 a number of observations suggest that an extended ocean once covered a significant part of the martian northern hemisphere by probing the physical properties of the subsurface to unprecedented depth the marsis mars express provides new geophysical evidences for the former existence of a late hesperian ocean the vastitas borealis formation located inside a putative shoreline of the ancient ocean has a low dielectric constant compared with that of typical volcanic materials we show that the measured value is only consistent with low density sedimentary deposits massive deposits of ground ice or a combination of the two in contrast radar observations indicate a distribution of shallow ground ice in equilibrium with the atmosphere in the south polar region we conclude that the northern plains are filled with remnants of a late hesperian ocean fed by water and sediments from the outflow channels about 3 gy ago

representation of flora and vegetation in quaternary fossil assemblages known and unknown knowns and unknowns paleoecological inference rests on a foundation of processes and relationships that lie between the target variables of interest and the proxy data extracted from the fossil record inattention to these processes can lead to overconfidence reification of proxies and ignorance creep a process by which assumptions become taken for granted and ultimately hidden or forgotten paleoecological inference can be strengthened and its uncertainties identified and quantified by developing forward conceptual models that incorporate the processes and relationships known to lie between target variables and proxy data these may fall into four general categories source vector diagenesis and analysis the uncertainties within each of these categories are somewhat unique although interactions often arise among processes in different categories i use inference of regional species occurrence from macrofossil assemblages in woodrat neotoma middens to illustrate the effects of various processes and interactions on strength of inference and origin of uncertainties and to identify how uncertainties can be characterized reduced or quantified the kinds of issues discussed in the woodrat midden example are pervasive in paleoenvironmental and paleoecological inference and should be examined thoroughly for all proxies and archives on a regular basis

global surface temperatures over the past two millennia 1 we present reconstructions of northern and southern hemisphere mean surface temperature over the past two millennia based on high resolution proxy temperature data which retain millennial scale variability these reconstructions indicate that late 20th century warmth is unprecedented for at least roughly the past two millennia for the northern hemisphere conclusions for the southern hemisphere and global mean temperature are limited by the sparseness of available proxy data in the southern hemisphere at present

pairwise comparisons to reconstruct mean temperature in the arctic atlantic region over the last 2 000 years existing multi proxy climate reconstruction methods assume the suitably transformed proxy time series are linearly related to the target climate variable which is likely a simplifying assumption for many proxy records furthermore with a single exception these methods face problems with varying temporal resolutions of the proxy data here we introduce a new reconstruction method that uses the ordering of all pairs of proxy observations within each record to arrive at a consensus time series that best agrees with all proxy records the resulting unitless composite time series is subsequently calibrated to the instrumental record to provide an estimate of past climate by considering only pairwise comparisons this method which we call paico facilitates the inclusion of records with differing temporal resolutions and relaxes the assumption of linearity to the more general assumption of a monotonically increasing relationship between each proxy series and the target climate variable we apply paico to a newly assembled collection of high quality proxy data to reconstruct the mean temperature of the northernmost atlantic region which we call arctic atlantic over the last 2 000 years the arctic atlantic is a dynamically important region known to feature substantial temperature variability over recent millennia and paico allows for a more thorough investigation of the arctic atlantic regional climate as we include a diverse array of terrestrial and marine proxies with annual to multidecadal temporal resolutions comparisons of the paico reconstruction to recent reconstructions covering larger areas indicate greater climatic variability in the arctic atlantic than for the arctic as a whole the arctic atlantic reconstruction features temperatures during the roman warm period and medieval climate anomaly that are comparable or even warmer than those of the twentieth century and coldest temperatures in the middle of the nineteenth century just prior to the onset of the recent warming trend

kinematic structural restorations and discrete fracture modeling of a thrust trap a case study from the tarija basin argentina the integration between kinematic structural restorations and discrete fracture simulation is applied to a thrusted and fractured fault block in the tarija basin northern argentina the emphasis is on the influence of the factor time on the deformation history and fracture growth the structural evolution of the gas bearing santa rosa reservoir forms the basis for understanding the development of the 3d fracture system as simulated with 3d kinematic restorations during the restoration the cumulative dilatational strain was calculated and mapped and compared to traditional curvature analyses the strain maps are subsequently used to simulate geologically realistic discrete fracture networks that form the basis for further exploration and development of the field

a forward modeling approach to paleoclimatic interpretation of tree ring data 1 we investigate the interpretation of tree ring data using the vaganov shashkin forward model of tree ring formation this model is derived from principles of conifer wood growth and explicitly incorporates a nonlinear daily timescale model of the multivariate environmental controls on tree ring growth the model results are shown to be robust with respect to primary moisture and temperature parameter choices when applied to the simulation of tree ring widths from north america and russia from the mann et al 1998 and vaganov et al 2006 data sets the forward model produces skill on annual and decadal timescales which is about the same as that achieved using classical dendrochronological statistical modeling techniques the forward model achieves this without site by site tuning as is performed in statistical modeling the results support the interpretation of this broad scale network of tree ring width chronologies primarily as climate proxies for use in statistical paleoclimatic field reconstructions and point to further applications in climate science

characterizing decadal to centennial variability in the equatorial pacific during the last millennium 1 the magnitude of sea surface temperature variability in the nino3 4 region of the equatorial pacific on decadal and longer timescales is assessed in observational data state of the art coupled model intercomparison project 5 climate model simulations and a new ensemble of paleoclimate reconstructions on decadal to multidecadal timescales variability in these records is consistent with the null hypothesis that it arises from multivariate red noise a multivariate ornstein uhlenbeck process generated from a linear inverse model of tropical ocean atmosphere dynamics on centennial and longer timescales both a last millennium simulation performed using the community climate system model 4 ccsm4 and the paleoclimate reconstructions have variability that is significantly stronger than the null hypothesis however the time series of the model and the reconstruction do not agree with each other in the model variability primarily reflects a thermodynamic response to reconstructed solar and volcanic activity whereas in the reconstruction variability arises from either internal climate processes forced responses that differ from those in ccsm4 or nonclimatic proxy processes that are not yet understood these findings imply that the response of the tropical pacific to future forcings may be even more uncertain than portrayed by state of the art models because there are potentially important sources of century scale variability that these models do not simulate

distribution of fault slip in outcrop scale fault related folds appalachian mountains abstract current kinematic models of ramp related folds predict a direct relationship between ramp angle and fold shape and imply specific sequences of deformation analyses of outcrop scale structures in the valley and ridge province of the appalachians reveal configurations that depart from model predictions the models fail to account for the presence of footwall synclines and are inconsistent with measured displacement distributions on some natural faults observations support the interpretation that faults can grow by propagation both up and down dip from a nucleation point fault propagation in either direction may result in the formation of folds primarily on the side of the fault that is displaced in the direction of fault propagation