A much improved high-resolution integrated stratigraphy (calcareous plankton biostratigraphy, magnetostratigraphy,
cyclostratigraphy) is presented for the classic section of Oued Akrech (Atlantic Morocco) straddling the
Tortonian^Messinian boundary. Magnetobiostratigraphic correlations with time-equivalent and astronomically dated
sections in the Mediterranean indicate that cyclic alternations of indurated light beige coloured marls and softer, more
clayey and reddish coloured marls are dominantly precession-controlled. Characteristic sedimentary cycle patterns, in
particular those reflecting precession^obliquity interference, allow for one possible tuning, thus providing accurate
astronomical ages for cycles, calcareous plankton events and magnetic reversals. The tuning further indicates that the
reddish layers are the equivalent of sapropels in the Mediterranean. The Messinian Global boundary Stratotype Section
and Point (GSSP) has recently been formally defined at the base of the reddish layer of cycle No. 15 in section Oued
Akrech. This level coincides closely with the first regular occurrence of the Globorotalia miotumida group and is
astronomically dated at 7.251 Ma. The global correlation potential is guaranteed by the straightforward calibration of
the Oued Akrech magnetostratigraphy to the geomagnetic polarity time scale, locating the GSSP within C3Br.1r. In the
marine realm the calcareous nannofossil genus Amaurolithus provides a series of extremely useful events to delimit the
boundary on a global scale. The astronomical tuning guarantees a direct first-order calibration of the Messinian GSSP
to the standard geological time scale once, as anticipated, the late Miocene part of the astronomical time scale has been
incorporated
