Abstract

Extensive geological, geophysical, structural, and geochronological data suggest that the locations of great escarpments bordering passive margins are exceptionally stable and are probably determined by crustal structure. Together, the data do not support the established paradigm of ongoing, significant, and parallel escarpment retreat. Rather, thermochronologic data and sedimentary sequences in ocean basins suggest that initial, tectonically controlled rift escarpments undergo rapid and significant erosion only during the earliest stages of seafloor spreading. Development of stable passive margin escarpments follows this period of intense erosion. Escarpments increase in sinuosity as embayments retreat more rapidly than interfluves. Measurements of 24 escarpments suggest that sinuosity, and the rate at which it increases, depends upon the location of maximum uplift, the geometry of the preescarpment drainage system, and margin age. All data suggest that the location of passive margin escarpments does not change significantly over time.

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