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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 64 (1980)

Issue: 5. (May)

First Page: 704

Last Page: 704

Title: How do Thrust Belts Form?: ABSTRACT

Author(s): David Elliott

Article Type: Meeting abstract

Abstract:

Thrust belts form at converging plate margins and straddle both sides of a hinterland occupied by a calc-alkaline arc. There are two competing theories for thrust belts and each implies a distinctly different behavior at the plate margins. The two theories, stated in oversimplified form, claim that thrust belts are created by either a horizontal push, or by the gravity-driven spreading of an elevated hinterland. In response to modern geometrically based structural interpretations the two theories have changed and developed over the past decade. Thrust toes are clearly dominated by a compressive push from the rear, but for larger parts of a thrust the gravitational terms are more significant. However, on the scale of an entire thrust belt, are rocks sufficiently weak for t e gravitational terms to dominate? One of the principal differences between the two theories boils down to the question of rock strength. Certain simple structures provide a key to this impasse. One is listric normal and growth faults which develop without any push from the rear. Because of their high degree of symmetry, opposed-dip thrust complexes, such as triangle zones and pop-ups, also provide information. By working on these structures with limit analysis, a method recently developed in soil mechanics, we can estimate upper and lower bounds which bracket rock strengths under long term geological conditions. These bounds to rock strength can be directly applied to the two theories for the formation of thrust belts.

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Copyright 1997 American Association of Petroleum Geologists