The effects of mechanical stratigraphy on ramp spacing and ramp initiation in foreland fold and thrust belts /
This study investigates the effect of mechanical stratigraphy, a fundamental characteristic of many fold and thrust belts, on ramp initiation and spacing. The causes for the sequential decrease in ramp spacing observed in some foreland fold and thrusts are examined. We present a finite element wed...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2002.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=765105801&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | This study investigates the effect of mechanical stratigraphy, a fundamental characteristic of many fold and thrust belts, on ramp initiation and spacing. The causes for the sequential decrease in ramp spacing observed in some foreland fold and thrusts are examined. We present a finite element wedge model with stratigraphic heterogeneity that incorporates a pressure-dependent, elastic-perfectly plastic rheology. The study has two parts. A mechanically homogeneous standard model is used to assess the effects of variations in yield stress, dilation angle and basal friction in ramp initiation and spacing. The results from this homogeneous study are analyzed to form a basis with which to evaluate the effects of mechanical layering on ramp initiation and spacing. We found that thrust ramp development always begins at the topographic inflection produced by the previous ramp but is preferentially localized in a forethrust after a sufficient amount of backstop displacement. Ramps initiate at different horizontal distances for different basal strengths in the layered models. The strongest member in a layered wedge controls ramp location and ramp spacing. Plastic strain accumulation is noticeably diminished in existing ramps when new ramps are formed towards the foreland. However, for the 3-layer models, thrust ramps in the hinterland may be reactivated. Plastic strain accumulation is always present in the hinterland for the homogeneous models, even after more ramps are formed towards the foreland. Ramp spacing in both homogeneous and layered models always decreases towards the foreland, predominantly a result of the wedge geometry. A plot of the spacing of the frontal ramps in layered models was is in good agreement with observed data of ramp spacing in some fold and thrust belts. |
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| Item Description: | Vita. "Major Subject: Geology". |
| Physical Description: | xviii, 154 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 130-134). |