Abstract: The middle liassic inner platform carbonate deposits of Morocco are characterised by a succession of metric regressive sedimentary cycles. An autochtonous unicellular microfauna (foraminifera, orbitopsellids s. l. and hauraniids) and macrofauna (mollusca, lithiotid etc.) are associated with the lower part of the cycles, subtidal lagoon; whereas an allochtonous assemblage of orbitopsellids s. l ., displaced on the supratidal zone by high energy waves or tidal currents or tempestites is present on top of the cycles. The bioclastic and reef deposits of the outer platform do not contain orbitopsellids s.l.

The cycles are interpreted as autocyclic, resulting from succesive filling of the lagoon by carbonate mud in a context of progressive subsidence. The hypothesis of an astronomic control (precession etc) does not fit with field observations.