STRATIGRAPHY AND EVOLUTION OF UPPER CRETACEOUS-PALEOGENE SEDIMENTARY SYSTEMS IN THE MARRAKESH HIGH-ATLAS (MOROCCO)

The Maastrichtian and Palaeogene deposits of the northern side of the High Atlas of Marrakesh have been subdivided into two sedimentary syst ems, separated by a regional disconformity. The former is of Maastrich tian age, even partially Campanian at its base. Their third order depo sition sequences are more developed going from W (proximal deposits) t o E (distal deposits) and constitute a carbonate ramp of this epoch. T hey are interpreted as the end of a filling sequence in a second order regressive period after the Lower Senonian. The latter (Upper Palaeoc ene to Lutetian) is composed of several sequences of third order which constitute a sedimentary hiatus to the West. These sequences represen t successive ingressions followed by the withdrawal of the sea. The la tter system corresponds to the aggradation or retrogressive sequence o f the transgressive period of the second order of a transgressive/regr essive cycle (according to Jacquin et al., 1992). From the Upper Eocen e to Oligocene, the sector functions as Atlasic chain foreland basin.