Constraining Passive Margin Escarpment Evolution by Low-Temperature Thermochronology
Abstract
Passive margin escarpments are major geomorphic features that separate low-relief, high elevation plateaux from near sea-level coastal plains. Their initial development is often linked to a base level drop associated with the episode of continental rifting that leads to the opening of an adjacent oceanic basin. How they migrate from their original coastal position to their present-day location sometimes several hundred kilometers inland, remains a matter of debate. Do escarpments retreat while maintaining their shape, or do they evolve from their original position to the location of a pre-existing inland divide by downwearing of the continental plateau. Recent thermo-chronological studies across the Great Escarpment of Southeastern Australia and the escarpment flanking the southern margins of the African continent have provided some constraints on the rate and nature of escarpment migration. Here, we use a complex three-dimensional thermal model of the crust coupled to a surface processes model to demonstrate under which circumstances thermochronological data can be used to provide meaningful information on the evolution of the escarpment. Furthermore, we define specific sampling strategies to optimize the information that can be extracted from thermochronological datasets on the rate of escarpment migration, the nature of its retreat as well as the value of poorly constrained parameters such as the local geothermal gradient and the flexural thickness of the lithosphere. In this context, we re-analyze published datasets on the Great Escarpment of Southeastern Australia and demonstrate that they contain incomplete information on the evolution of the escarpment. We define new potential targets that might provide more constraining information.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2003
- Bibcode:
- 2003AGUFM.H51D1087V
- Keywords:
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- 1824 Geomorphology (1625)