Evolution of a highly dilatant fault zone in the grabens of Canyonlands National Park, Utah, USA - Integrating fieldwork, ground-penetrating radar and airborne imagery analysis

Abstract. The grabens of Canyonlands National Park are a young and active system of sub-parallel, arcuate grabens, whose evolution is the result of salt movement in the subsurface and a slight regional tilt of the faulted strata. We present results of ground-penetrating radar (GPR) surveys in combination with field observations and analysis of high-resolution airborne imagery. GPR data show intense faulting of the Quaternary sediments at the flat graben floors, implying a more complex fault structure than visible at the surface. Direct measurements of heave and throw at several locations to infer fault dips at depth, combined with observations of primary joint surfaces in the upper 100 m, suggest a highly dilatant fault geometry. Sinkholes observed in the field as well as in airborne imagery give insights in local dilatancy and show where water and sediments are transported underground. Based on correlations of paleosols observed in outcrops and GPR profiles, we argue that either the grabens in Canyonlands National Park are older than previously assumed or that sedimentation rates were much higher in the Pleistocene. This is the final version of the article. It first appeared from Copernicus Publications via http://dx.doi.org/10.5194/se-6-839-2015 The supplement related to this article is available online at http://dx.doi.org/10.5194/se-6-839-2015-supplemen

Dilatant normal faulting in jointed cohesive rocks: a physical model study

Dilatant faults often form in rocks containing pre-existing joints, but the effects of joints on fault segment linkage and fracture connectivity are not well understood. We present an analogue modeling study using cohesive powder with pre-formed joint sets in the upper layer, varying the angle between joints and a rigid basement fault. We analyze interpreted map-view photographs at maximum displacement for damage zone width, number of connected joints, number of secondary fractures, degree of segmentation and area fraction of massively dilatant fractures. Particle imaging velocimetry provides insight into the deformation history of the experiments and illustrates the localization pattern of fault segments. Results show that with increasing angle between joint-set and basement-fault strike the number of secondary fractures and the number of connected joints increase, while the area fraction of massively dilatant fractures shows only a minor increase. Models without pre-existing joints show far lower area fractions of massively dilatant fractures while forming distinctly more secondary fractures

Sustainable development of production in Russia: an informative aspect

This paper is devoted to the study of the problems of introduction of the concept of sustainable development of production at modern enterprises. The paper substantiates the necessity of application of this concept at enterprises, gives reasons hindering this process. In addition, the analysis of the notion of sustainable development of production, wherein this process is represented as development of production by means of rational and economical use of resources oriented to provision of a long-term competitive advantage, was conducted in the paper. Moreover, the paper presents the basic principles of successful introduction of the concept of sustainable development of production. By the example of Toyota Company the benefits, which can be derived by an enterprise from application of this concept, were shown

SEM observation of grain boundary structures in quartz-iron oxide rocks deformed at intermediate metamorphic conditions

Muitos estudos t?m demonstrado o efeito de uma segunda fase sobre a distribui??o de fase fluida e dissolu??o de gr?os de quartzo. Entretanto, como a maioria das observa??es v?m de agregados deformados sob condi??es de tens?o hidrost?tica e em rochas quartzosas ricas em mica, a distribui??o 3D de poros em bordas quartzo-quartzo (BQQ) e quartzo-hematita (BQH) tem sido estudada. V?rias superf?cies de fraturas orientadas segundo o elips?ide de deforma??o finita foram analisadas. A distribui??o dos poros caracteriza a porosidade e a forma dos gr?os como altamente anisotr?picas, o que resulta da natureza e orienta??o das bordas. BQH t?m propriedades f?sico/qu?micas muito diferentes de BQQ, uma vez que as plaquetas de hematita t?m forte efeito no comportamento do fluido, de maneira similar ?s micas em quartzitos. Elas s?o superf?cies planas, livres de poros, normais ? dire??o de m?ximo encurtamento, sugerindo que estiveram, em um momento, cobertas por um filme cont?nuo de fluido agindo como um caminho mais r?pido de difus?o. Nas BQQ, os poros s?o facetados, isolados, concentrados nos limites das mesmas refletindo o controle cristalogr?fico e uma rede interconectada de fluido ao longo das jun??es dos gr?os. As BQQ normais ? dire??o de m?xima extens?o s?o s?tios de concentra??o de flui crescimento de gr?os foram respons?veis pela forma??o de plaquetas de hematita e gr?os de quartzo tabulares contribuindo significativamente para a gera??o da folia??o observada nas rochas estudadas.Several studies have demonstrated the effect of a second phase on the distribution of fluid phase and dissolution of quartz grains. However, as most observations came from aggregates deformed under hydrostatic stress conditions and mica-bearing quartz rocks, 3-D distribution of pores on quartz-quartz (QQB) and quartz-hematite boundaries (QHB) has been studied. Several fracture surfaces oriented according to finite strain ellipsoid were analyzed. The pore distribution characterizes the porosity and grain shape as highly anisotropic, which results from the nature and orientation of boundaries. QHB have physical/chemical properties very different from QQB, once the hematite plates have Strong effect on wetting behavior of fluid, likewise micas in quartzites. They are pore-free flat surfaces, normal to compression direction, suggesting that they were once wetted with a continuous fluid film acting as faster diffusion pathway. At QQB, the pores are faceted, isolated, close to its edges reflecting the crystallographic control and an interconnected network of fluid along grain junctions. The QQB facing the extension direction are sites of fluid concentration. As consequence, the anisotropic dissolution and grain growth were responsible for the formation of hematite plates and tabular quartz grains significantly contributing for the generation of the foliation observed in the studied rocks

Late burial to early tectonic quartz veins in the periphery of the High-Ardenne slate belt (Rursee, North Eifel, Germany)

A detailed structural mapping and geometrical analysis of distinct bedding-(sub)perpendicular and bedding-parallel quartz veins has been performed in the northeastern part of the High-Ardenne slate belt (Rursee, North Eifel, Germany), with the aim to reconstruct the local fracturing/veining history. The structural relationship of these two types of veins as well as their relationship with cleavage, folds and faults allows attributing a pre- to early-Variscan age to these veins. The first type of veins is oriented (sub)perpendicular to bedding and consists of several, mutual cross-cutting generations, which clearly predate Variscan deformation. The second type of veins, bedding-parallel veins, post-dates the bedding-(sub)perpendicular veins and reflects bedding-parallel thrusting at the onset of Variscan deformation, predating folding. Subsequently, during progressive Variscan compression both types of veins were passively folded within characteristic, NW-vergent, overturned folds. Locally, due to flexural slip folding, reactivation along the bedding-parallel veins may have taken place.status: publishe

Mullions in the High-Ardenne Slate Belt (Belgium): numerical model and parameter sensitivity analysis

In the High-Ardenne Slate Belt (Belgium), pre-existing layer-perpendicular quartz veins in psammite layers acted as mechanical boundaries due to the difference in competence between vein quartz and psammite. This caused the formation of mullions during layer-parallel shortening. In this paper, the process of mullion formation is modelled using finite-element techniques. A parameter sensitivity analysis of the mullion model demonstrates that the stress exponent of psammite, the total horizontal shortening of the psammite layers, the initial aspect ratio of the psammite segments between the veins and the competence contrast between psammite and vein quartz are the controlling parameters for the shape of the mullions. Our results suggest that the morphology of the mullions can be used to constrain the rheology of psammite deforming in the middle crust. Moreover, the parameter sensitivity analysis illustrates the range of layer-parallel shortening/extension structures associated with layer-perpendicular quartz veins that can be expected in nature (e.g. dogbones, inverted mullions) and creates future perspective for the use of the model as a paleorheological gauge for these structures. (C) 2004 Elsevier Ltd. All rights reserved.status: publishe

Early vein generations in the High-Ardenne slate belt (Belgium, Germany): the earliest manifestations of the Variscan orogeny?

status: publishe