Lithostratigraphy of the littoral deposits of the last one million years in the Casablanca area (Morocco)
Résumé
Littoral deposits of the Casablanca region have provided most of the stratotypes for the Quaternary marine "stages" of the Maghreb. A part of these deposits is the subject here of a new lithostratigraphic approach mainly based on the study of facies association, as well as diagenetic processes. This has permitted the identification of ten (may be twelve) high-resolution sequences. These units all probably accumulated over the last million years. The sequences are progradational and, most of the time, record a relatively straightforward history. They result from an abrupt rising followed by a gradual falling of the sea level. Sedimentary structures indicate upper shoreface (sometimes), foreshore, backshore and aeolian dune depositional environments. Runoff and mud- or debris-flow are probably the main processes involved in the deposition of the slope deposits intercalated in this stratigraphic series. Moreover, the results show that the classic chronostratigraphic framework so far used in the Maghreb is inadequate because of incorrect correlations and chronological attributions, previously unidentified formations and the definition of distinct "stages" from the same stratigraphic unit. In view of these problems, this classic framework must be abandoned.