Faculté des sciences

Fold interference patterns in the Late Palaeozoic Anti-Atlas belt of Morocco

Burkhard, Martin ; Caritg, Séverine ; Ducommun, Romain ; Helg, Urs ; Kopp, Lionel ; Sue, Christian

In: Terra Nova, 2004, vol. 16, p. 27-37

We document two phases of folding within the central part of the Late Palaeozoic Anti-Atlas chain of Morocco. A first generation of SW-NE folds involve a horizontal shortening of 10-20%, accommodated by polyharmonic buckle folding of contrasting wavelengths in Ordovician Jbel Bani quartzites and Devonian Jbel Rich carbonates. A second generation of folds with similar style and wavelengths in an... More

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    Summary
    We document two phases of folding within the central part of the Late Palaeozoic Anti-Atlas chain of Morocco. A first generation of SW-NE folds involve a horizontal shortening of 10-20%, accommodated by polyharmonic buckle folding of contrasting wavelengths in Ordovician Jbel Bani quartzites and Devonian Jbel Rich carbonates. A second generation of folds with similar style and wavelengths in an E-W direction lead to complex interference patterns. Dome and basins are developed within the Jbel Rich and within Lower Cambrian dolomites. Both folding phases are related to thick-skinned uplift of Precambrian basement in a Laramide style. In contrast to the typical Rocky Mountain foreland style, however, cover deformation in the Anti-Atlas is mostly decoupled from the undying basement along thick incompetent horizons such as the Lower Cambrian Lie-de-Vin and Silurian shales.