Search

In the Honalilar area (Denizli Basin, Turkey), the occurrence of banded Ca-carbonate veins and travertine deposits, represented by a dismantled fissure ridge-type depositional system, are the evidence of a middle-late Pleistocene exhumed, shallow, hydrothermal system. Their occurrence offers the best opportunity to: (i) reconstruct the fluid paths from the underground to the palaeo-surface, and (ii) analyse the role of fault zones in controlling the permeability and fluids circulation. Permeability developed in overstepping regional scale normal faults, with a slight left-lateral oblique-slip component. At the surface, faults favored the localization and development of a fissure ridge-type travertine deposit. At depth, the root of the hydrothermal system consists of W-E oriented fractures filled of up to 6.5 m thick Ca-carbonate veins, developed in a high dilatation zone. It corresponds to the step-over determined by the oblique-slip kinematics of the NW-striking main faults. The high dilatation step-over zone contrasted the progressive sealing induced by the concomitant Ca-carbonate deposition within the fractures, thus favoring permeability maintenance and fluids circulation for at least 200 ka. This evidence adds key inputs for predicting permeable volumes during geothermal exploration in areas affected by extensional tectonics. The main NW-oriented faults remained active even after the hydrothermal fluid flow, causing the dismantlement and progressive exhumation of the upper part of the hydrothermal system. © 2020 Elsevier Ltd

Normal faults, when observed in detail, are commonly seen to consist of arrays of segments. The geometry of the boundaries between these segments has been extensively studied in outcrop and in subsurface geophysical datasets. Existing models generally consider that at low displacements the segments interact by deformation of the intervening rock volume, and become progressively linked as the displacement increases. The interaction and linkage of these segments is important in the formation and development of fault zones. The recent increase in availability of high quality 3-D seismic reflection data has allowed the detailed geometry of faults to be better imaged. While there are some studies focused on the geometry of segment boundaries, few have focused on the detailed small scale features of these structures and very few studies have focused on the kinematics of these structures. In this project a highly detailed analysis of the geometry and kinematics of segmented normal faults imaged in high quality 3-D seismic reflection data has been carried out. This analysis has revealed substantial departures from the relatively simple geometries and evolutionary models which are generally inferred from 2-D or lower resolution 3-D mapping. These departures include:- the formation of an array of parallel faults which become an array of interacting segments by the localisation of displacement onto shorter lengths of the established fault surfaces; the formation of a segment boundary by the propagation of a splay from a preexisting through going fault; the removal of large scale asperities and also stepping during lateral propagation of a fault giving rise to a segmented geometry. Adjustments to the existing models and a classification scheme for segment boundaries based on their 3-D geometry are proposed. Despite the observed variability in the nature of segment boundaries, all of the structures examined in this thesis formed in a way which was geometrically and kinematically coherent throughout their development and evidence for the development of segment boundaries by the coalescence of initially isolated faults has not been found. In each case, combining displacements accommodated by discontinuous (faulting) and continuous (folding) deformation yielded simple overall displacement distributions associated with a single structure. Kinematic analysis demonstrates that faulting and folding show, not only spatially complementary variations, but also, that these components are complementary in time. During the development of a segmented fault array segment boundaries are the areas where continuous deformation is most prevalent.

El Subandino Sur de Bolivia es una típica faja plegada y corrida de lámina delgada,con una notable regularidad en la geometría de las estructuras. Esta es una característicatípica de las fajas plegadas en las que no se involucra el basamento en la deformación. Sin embargo, cuando se analiza en detalle la geometría y evolución de la deformacióndel Subandino Sur, se verifica que existen numerosas desviaciones de dicha regularidad. En el presente trabajo se estudiaron los diferentes procesos que habrían condicionado eldesarrollo de las estructuras del Subandino Sur, y se puso especial énfasis en el análisisde aquellos factores que podrían explicar las irregularidades que se identifican en lageometría y evolución de la deformación de las diferentes estructuras. Del análisis realizado se destaca la relevancia que tienen los niveles de despegueinvolucrados en la deformación. En particular, se analiza la importancia que habríatenido el nivel de despegue superior en el desarrollo de los diferentes estilosestructurales que se observan en el Subandino Sur. Este análisis se enfocó en eldesarrollo de sobrepresiones, factor determinante para el funcionamiento del nivel dedespegue en las pelitas devónicas de la Formación Los Monos. Para esto se realizaronuna serie de modelos de sistemas petroleros 1D, mediante los cuales se pudo modelar lageneración primaria de gas y el craqueo secundario, procesos que se relacionan con laexistencia de sobrepresiones y, por lo tanto, con la eficiencia del nivel de despeguesuperior. Los modelos permitieron relacionar la evolución térmica de la cuenca deantepaís y la generación de gas, con los diferentes estilos estructurales que se observanen la actualidad en el frente de deformación. De esta manera se pudo dividir al frente dedeformación del Subandino Sur en dos segmentos bien diferenciados. Por un lado, en elsegmento norte, donde los modelos indican que la generación de gas y lassobrepresiones de la Formación Los Monos estarían bien desarrolladas, se verifica laexistencia de estructuras de dúplex de techo compuesto en las cuales el nivel dedespegue superior se encuentra activo. Por el contrario, en el segmento sur del frente dedeformación, donde los modelos sugieren que la generación de gas en las pelitasdevónicas de la Formación Los Monos sería escasa, se desarrollan estructuras depliegues de flexión de falla donde el despegue superior no estaría involucrado en ladeformación. Con un abordaje similar al que se describe en el párrafo anterior, se realiza elanálisis de los distintos estilos estructurales que se observan en los diferentes trenes deestructuras. Este análisis permite relacionar las diferentes historias térmicas que habríanexistido en la cuenca de antepaís durante la evolución de la deformación, con los estilosestructurales desarrollados en los distintos trenes de la faja plegada y corrida del Subandino Sur. Se proponen tres situaciones en las que se habrían desarrollado lasdiferentes estructuras del Subandino Sur. Una primera situación donde el despeguesuperior no estaría bien desarrollado, y donde se generarían estructuras de pliegues deflexión de falla; una segunda situación donde el despegue superior estaría limitado a unaestrecha franja cercana al frente de deformación, y donde las estructuras favorecidasserían dúplex de techo pasivo; y una tercera situación donde el despegue superior estaríaampliamente desarrollado, y donde se favorecerían las estructuras de dúplex de techoactivo. Para complementar el análisis de los estilos estructurales, se realizaron diferentesmodelos análogos con los que se logró reproducir algunas de las características que seobservan en la deformación interna de los niveles pelíticos de la Formación Los Monosen los núcleos de los anticlinales típicos del Subandino Sur de Bolivia y Argentina. Otro de los rasgos que llama la atención cuando se analiza la geometría en plantade la faja plegada del Subandino Sur es la existencia de zonas de transferencia einflexiones que se alinean en sucesivos trenes estructurales. Para analizar este fenómeno,en el presente trabajo se estudiaron los factores que condicionan el espaciamiento entreestructuras y se realizó una medición del espaciamiento actual que se observa entre losdiferentes trenes estructurales del Subandino Sur. Se propone un modelo de evoluciónen el que las zonas de transferencia e inflexiones que se replican en trenes estructuralessucesivos se generarían de forma tal de mantener un espaciamiento regular entre lasdiferentes estructuras. Particularmente se analiza el caso de la estructura de La Vertiente, que es unpliegue de flexión de falla relativamente pequeño y de escaso rechazo. De acuerdo a lainterpretación de líneas sísmicas 2D, el comienzo de la deformación de esta estructurafue datado por diferentes autores en 6 Ma. La restitución de las secciones estructuralesindicaría que la misma fue generada a un espaciamiento de alrededor de 65 km, lo cualrepresenta entre 2 y 3 veces el espaciamiento máximo que se verifica en el resto de lasestructuras del Subandino Sur. Para explicar esta “anomalía”, se analizaron losdiferentes factores que podrían generar un aumento del espaciamiento de este orden. Se presenta un modelo en el que el aumento en la capacidad de erosión del Rio Pilcomayo,producto de la captura de una vasta región que previamente habría drenado al Río Parapetí, habría generado una drástica disminución del coeficiente de fricción basalefectivo en las pelitas silúricas de la Formación Kirusillas. Este cambio, a su vez, seríaresponsable del aumento en el espaciamiento entre estructuras que se verifica para laestructura de La Vertiente. The Southern Subandean Zone of Bolivia is a typical thin-skinned fold and thrustbelt with a remarkable regularity in the geometry of the structures. This is a typicalcharacteristic of fold and thrust belts where the basement is not involved intodeformation. However, when the structural geometry and evolution are analyzed indetail, it is verified that there are many deviations from such regularity. In this paper ithas been studied the processes that might have affected the development of thestructures along the Southern Subandean Zone, and special emphasis was placed onanalyzing those processes that could explain the irregularities identified in the geometryand evolution of the deformation of the different structures. The analysis highlights the relevance of the detachment levels involved in thedeformation. Particularly, it is analyzed the role that may have played the upperdetachment level in the development of the different structural styles observedthroughout the Southern Subandean Zone of Bolivia. This analysis is focused on thedevelopment of overpressures, which may have been essential for the activation of thedetachment level at the Devonian shales of the Los Monos Formation. To do this, aseries of 1D petroleum system models were done at different positions along the presentdeformation front. This analysis allows to model primary gas generation and secondarycracking, processes that are related to the overpressure development, and therefore, withthe efficiency of the upper detachment level. The models suggest a relationship betweenthermal evolution of the foreland basin and generation of gas, with different structuralstyles observed in the present deformation front. In this way, it was possible to dividethe deformation front of Southern Subandean Zone in two distinct segments. In thenorthern segment, where models suggest that gas generation and overpressure of the Los Monos Formation would be well developed, it is verified the existence of structuresof composite roof duplex where the upper detachment level has been active. On theother hand, in the southern segment of the deformation front, where the models suggeststhat generation of gas in the Devonian shales of Los Monos Formation would be limited,it is verified the existence of structures of fault bend folds where upper detachment levelis not involved in the deformation. Using a similar approach to that described in the previous paragraph, an analysiswas performed at the different structural styles observed throughout the study area. This analysis allows relating the thermal evolution of the foreland basin during developmentof the deformation, with the different structural styles defined throughout the entire foldand thrust belt of Southern Subandean Zone of Bolivia. The results suggest threescenarios under which may have been developed the different structural styles observedat the Southern Subandean Zone. A first scenario is defined where the upper detachmentlevel would not be well developed, and where fault bend folds were generated. Asecond scenario is defined where the upper detachment level would be limited to anarrow strip near the deformation front, and where the favored structures would havebeen passive roof duplex. And a third situation is defined where the upper detachmentlevel would be widely developed. Under this scenario active roof duplex structures arepreferentially generated. In order to complement the structural style analysis, different analogue modelswere done to reproduce some of the features related to the internal deformation of thepelitic intervals of the Los Monos Formation at the cores of several anticlines developedalong the Southern Subandean Zone of Bolivia and northern Argentina. Another feature that highlights when analyzing the plan view geometry of thestructures of the Southern Subandean Zone is the existence of relay zones andinflections that align at successive structures. To analyze this feature, it have beenstudied the different factors that define the spacing between structures, and ameasurement of the existing spacing between structures were performed throughout thedifferent structures of the Southern Subandean Zone. It is proposed a model ofevolution which considers that relay zones and inflections that are replicated atsuccessive structures would have been generated in order to maintain regular spacingbetween the structures. Special attention is given to La Vertiente structure, a small fault bend fold withlow relief developed at Rio Pilcomayo latitude. According to 2D seismic interpretation,the beginning of the deformation of this structure has been dated by several authorsaround 6 Ma. A structural reconstruction of cross sections suggest that La Vertientestructure was generated at a spacing of 65 km, which represents between 2 and 3 timesthe maximum spacing that characterize the rest of the structures of the Southern Subandean Zone. With the aim of explaining this "anomaly", different factors that couldlead to an increase in the maximum spacing of this order have been analyzed. It ispresented a model in which increased capacity of erosion of the Rio Pilcomayo, as aresult of the drainage basin capture of some of the area that previously was part of the Río Parapetí drainage network, would have generated a dramatic decrease of theeffective basal friction coefficient of the Kirusillas Formation. This change, in turn,would be responsible for the increased spacing between structures which holds for thestructure of La Vertiente. Fil: Rocha, Emilio. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

The aim of this study is to improve our understanding on the mechanical interaction and linkage process between normal fault segments. Faults grow by the process of radial propagation and the linkage of segments, as strain increases, evolving to large fault systems. For this purpose we conducted a combined field and photogeological study on two major segmented fault zones in Central Greece, the Atalanti and Arkitsa fault zones. This approach includes effects of fault size and spatial distribution, scaling laws and footwall-hanginwall topography. Throw distribution and the geometry of the segmented fault arrays were analyzed in order to investigate the complexity of fault zones, the fault linkage process and the geometric characteristics of the relay zones formed between individual segments. The correlation of fault throw with fault length (D-L) and the ratios of overlap-separation (OL-S), separation-fault segment length (S-L) and relay displacement vs. separation (Dr-S) were examined in order to give an insight for fault segment interaction and linkage .