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Accueil du site → Doctorat → Allemagne → 2003 → A geologic model for the southern Altiplano at 21° S (Bolivia) elaborated using Remote Sensing and GIS methods

Freie Universität Berlin (2003)

A geologic model for the southern Altiplano at 21° S (Bolivia) elaborated using Remote Sensing and GIS methods

Goni, Patrick

Titre : Ein geologisches Modell für den südlichen Altiplano bei 21° S (Bolivien), erstellt mit Fernerkundungs- und GIS-Methoden

A geologic model for the southern Altiplano at 21° S (Bolivia) elaborated using Remote Sensing and GIS methods

Auteur : Goni, Patrick

Université de soutenance : Freie Universität Berlin

Grade : Doctoral thesis 2003

The Uyuni-Kehnayani Fault Zone (UKFZ) is a major Altiplano-internal structure of the Altiplano located in the Departamento Lipez of Southern Bolivia, it strikes NNE. During Paleocene and Eocene times in an extensional regime, a thick sequence of red siltstones was deposited as basinfill over marine Cretaceous sediments. Later, the UKFZ became a contractional structure and more fine clastic material was syntectonically deposited. The fault zone is marked by a system of thrust faults and branch thrusts that are dipping more and more steeply to the west. The entire structure overthrusts a Paleozoic ridge east of the UKF sensu strictu. In this contribution, a method is proposed that allows to build a conceptual geological model from surface geology, as well as strike and dip of bedding planes measured in the field and in aerial photographs. Additionally, a satellite image interpretation was performed for identification of major thrust and fold structures. The difficulties in this task consist in extending surface data into the subsurface. The chosen method uses the Discrete Smoothing Interpolation Algorithm for constructing surface models with a Triangulated irregular Network (TIN) structure. Also, bedding and additional information such as sequence thicknesses can be incorporated in this model as constraints for DSI. The resulting geometrical model clearly shows the main structures of the UKFZ and their subsurface geometry. The nonfolded, flat lying Cenozoic formations east of the UKFZ form a distinct contrast to the upright to overturned orientation of the same formations west of the UKFZ. These overthrusted sediments form the infill of an inverse halfgraben basin combined with a large anticline west of the UKFZ. The base of cenozoic sediments is plunging slightly to the north, which is consistent with regional structures. Problems arose in areas at the borders of the geological surface model with edge effects and crosscutting of bedding surfaces. These could be attributed to hidden subsurface structures. Areas where consistency of geological concepts is not yet sufficient could clearly be identified. The clues to the location of outcrops of significant importance are crucial for a successful field investigation. The geological model obtained with this approach is consistent with the overall regional geology. Numerical analyses of the model show a value of finite shortening along the UKFZ that is matching the values of previous works. Our method produces a consistent geological model, which can be used as constraint for other geological methods, such as balancing cross- sections. Values of finite shortening as derived from the geological model are fitting the previously observed data from other sources. Validation of the model can be performed in combination with independent data sets like seismic profiles. In this context, there the question arises what is the accuracy of a geometrical model. The assessment of confidence parameters for topology and geometry is still an unresolved problem. The elaborated geometrical model can be a starting point for studies on this problem. Moreover, conceptual errors that are invisible in geological maps, even combined with sections, are much more easier to detect using the proposed method.

Mots clés : Altiplano Bolivia Remote Sensing GIS 3D

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Page publiée le 15 octobre 2014, mise à jour le 2 novembre 2018