Integrated stratigraphy and astrochronology of the Messinian GSSP at Oued Akrech (Atlantic Morocco)

Abstract

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. ß

Tectonic control for evaporite formation in the Eastern Betics (Tortonian; Spain)

“…2). The First Regular Occurrence (FRO) of this species closely corresponds to the Tortonian-Messinian boundary (Hilgen et al, 2000). Specimens of the G. miotumida group are abundant to the top of the VV2 section and become intermittent from 115 to 130 m in section VV3.…”

Obliquity forcing of low-latitude climate

“…For instance, dust flux records from both the (sub)tropical Atlantic and the Arabian Sea concur with obliquity-paced global climate cycles, suggesting a close link between changes in low-latitude aridity and glacial variability (Bloemendal and deMenocal, 1989;deMenocal et al, 1993;Tiedemann et al, 1994;deMenocal, 1995). Several other proxy studies, however, find lowlatitude obliquity signals at times when glacial cycles were much smaller or even absent (Lourens et al, 1996(Lourens et al, , 2001Hilgen et al, 1995Hilgen et al, , 2000Sierro et al, 2000). In particular, obliquity-controlled interference patterns in Mediterranean sapropels are present not only in the Pleistocene (Lourens et al, 1996) but also in the warmer Pliocene and Miocene (Hilgen et al, 1995Zeeden et al, 2014).…”

Introductory Chapter: An Introduction to the Seismic and Sequence Stratigraphy and to the Integrated Stratigraphy: Concepts and Meanings

“…The Messinian GSSP has been individuated at the base of the red layer of the cycle n. 15 in the section Oued Akrech. It coincides with the irst occurrence of Globorotalia mitumida and is dated back at 7.251 My [80]. For the upper part of the Miocene, the Messinian is the standard chronostratigraphic unit, whose knowledge is due to the corresponding salinity crisis occurring in the Mediterranean Sea.…”

“…In my opinion, another main research topic in the integrated stratigraphy is represented by the Messinian Global Stratotype Section and Point (GSSP) [80]. High-resolution integrated stratigraphy has been presented by Hilgen et al [80], based on the integration of diferent stratigraphic methodologies, including the calcareous plankton biostratigraphy, the magnetic stratigraphy and the cyclic stratigraphy.…”

“…High-resolution integrated stratigraphy has been presented by Hilgen et al [80], based on the integration of diferent stratigraphic methodologies, including the calcareous plankton biostratigraphy, the magnetic stratigraphy and the cyclic stratigraphy. The Messinian GSSP has been individuated at the base of the red layer of the cycle n. 15 in the section Oued Akrech.…”