The effects of mechanical stratigraphy on the origin of triangle zones in thrust belts /
Triangle zones are found in the frontal portions of some
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| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1997.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=736824221&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Triangle zones are found in the frontal portions of some thrust belts. Despite their economic importance, little is known concerning why these structures form only in some thrust belts and not others. In this study we examine the importance of mechanical stratigraphy in controlling the formation and location of a triangle zone or passive-roof duplex. The study involves four integrated parts: (1) Triangle zones are examined worldwide for common mechanical stratigraphy. Triangle zones are most commonly frontal and form where a weak shale-rich section delaminates from stronger rocks at depth. (2) The history and kinematics of the Alberta Foothills triangle zone are examined at the seismic and microscale. Like other triangle zones, the central Alberta Foothills has a shale-rich cover, but triangle zones are also preserved within the thrust belt. They formed by discontinuous, local delamination above each lower-story structure. 6-10% shortening is accommodated in front of the triangle zone in the cover rocks. (3) The shales of the roof decollement were examined for the location of the smectite-to-illite transition. In Alberta, the location of delamination is controlled by an overpressured horizon developed at the smectite-to-illite transition. (4) Physical modeling was used to investigate the role of shortening rates and/or decollement strength in triangle zone development. With a roof decollement that is only slightly weaker than the rocks beneath it, physical models develop similar structures to the Alberta Foothills. The structures develop sequentially towards the foreland. Deformation is concentrated in the frontal structure, while older structures lock up and are translated forward with continued shortening. |
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| Item Description: | Vita. "Major Subject: Geology". |
| Physical Description: | xiii, 211 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 187-205. |