The mio-plio-pleistocene sequence at Casablanca covers the last six millions years. The age estimates for different phases of this sequence have been established by various methods : lithostratigraphy, biostratigraphy, absolute dating (OSL, ESR), palaeomagnetism and aminochronology. Mio-pliocene environments are characterized at extremely rich palaeontological sites (Lissasfa, Ahl-Al-Oughlam) but these have not yet yielded hominids remains.
The oldest lithic assemblages are found in Late Lower Pleistocene deposits, circa 1 Ma, in unit L of Thomas Quarry 1, and consist of Acheulian artefacts made from quartzite and flint. The first human remains discovered in this area were found in younger Middle Pleistocene deposits and cover an important period of human evolution between Homo erectus and modern Homo. They are associated with Acheulian artefacts and rich faunas in caves (Littorines Cave at Sidi Abderrahmane, caves at Thomas Quarries 1 and 3). The variability of Acheulian assemblages is well documented following recent excavations in various sites around the well known locality of Sidi Abderrahmane (Ours Cave, Cap Chatelier, Unit L and Hominid Cave at Thomas Quarry 1, Rhinoceros Cave at Oulad Hamida Quarry 1, Sidi Abderrahmane Extension and Sidi Al Khadir open-air sites). The Casablanca sequence thus offers useful data for comparison with those from other African areas where hominids appeared and developed and should be considered in the debate on the earliest occupation of Europe.