Deformation mechanisms associated with mesoscopic kinkbands, Jura Mountains (Switzerland) and Chaines Subalpines (France).
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1984.
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| Online Access: | Link to ProQuest Copy Link to OAKTrust copy |
| Abstract: | 18 mesoscopic kinkbands have been studied in the Jura Mountains and the Chaines Subalpines (Switzerland and France). The kinkbands have formed in well-bedded, micritic limestones (5 to 50 cm bedding thickness) with interbedded marls or shales (.2 to 2 cm bedding thickness), under low P-T conditions (no metamorphism). The geometry of the kinkbands was determined by stereophotogrammetric analysis (3-d digitization and computer evaluation); the state of deformation in and next to the kinkbands by detail study of microscopic and mesoscopic deformation mechanisms. On the basis of the observed state of deformation, two types of kinkbands were distinguished, for which two different kinematic models were inferred. (1) The rotation kinkbands are characterized by intensive deformation at the hinges (i.e., brecciation, intrabed thrusting and wedging of limestone layers) and absence of deformation within the limestone layers inside and outside the kinkband. Calcite infill in the intensely deformed interbeds indicates dilation. Typical deformation features are thin extension cracks, calcite veins, and tectonic stylolites. Kinkband formation is inferred to be by rigid body rotation of the limestone layers between fixed hinges. (2) The shear kinkbands are characterized by pervasive deformation of both the limestone layers and the interbeds inside the kinkband. Typical deformation features are pervasive normal faulting and thrusting. Kinkband formation is inferred to be by simple shear parallel to the kinkband boundaries. Since there is no obvious concentration of deformation at the hinges, there is no evidence against hinge migration as part of the kinematics. Analysis of the gross geometry of the kinkbands shows that the orientation of the kinkband boundaries with respect to bedding, (alpha)(,1), ranges between 30(DEGREES) and 80(DEGREES); the angle between the kinkband boundaries and the rotated layers, (alpha)(,2), ranges between 30(DEGREES) and 110(DEGREES). Generally, (alpha)(,2) is larger than (alpha)(,1), accordingly, the distance between bedding surfaces inside the kinkband, t(,2), is larger than the corresponding distance, t(,1), outside the kinkband. However, neither the angular relations, sin((alpha)(,2))/sin((alpha)(,1)), nor the ratio between bedding thickness inside and outside the kinkband, t(,2)/t(,1), provide a criterion by which the two types of kinkbands could be distinguished unequivocally. The distinction rests solely on the different states of deformation. Stereophotogrammetric results of 18 kinkbands are presented, and one outcrop of each type of kinkband is discussed in detail. |
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| Item Description: | "Major subject: Geology." Typescript (photocopy). Vita. |
| Physical Description: | xix, 327 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references (leaves 171-175). |