Detrital Zircon in the South Rifean Corridor, Morocco and Implications for the Messinian Salinity Crisis
University of South Carolina, Department of Earth and Ocean Sciences Columbia, South Carolina, United States
The South Rifean Corridor (SRC) is a paleo-marine connection between the Mediterranean Sea and the Atlantic Ocean. The closure of this corridor at ~6 Ma led the initiation of the Messinian Salinity Crisis (MSC) by isolating the Mediterranean Sea from the world ocean. At present, the SRC consists of a several sedimentary basins located between the Rif and Middle Atlas mountains of Morocco. Several hypotheses have been proposed to explain the corridor closure in the context of convergence between the African and Eurasian plates including (1) uplift resulting from subduction related lithospheric delamination, (2) renewed convergence after cessation of slab-rollback related extension in the Mediterranean Sea and (3) domal uplift of the Middle Atlas mountains.
To distinguish between the proposed mechanisms, this study has analyzed 11 arenaceous sandstone samples from the Taza-Guercif Basin of the SRC and 3 samples from the Rif for detrital zircon U-Pb ages. Shifts in provenance throughout the basin stratigraphy should record changes in sediment provenance as a result of orogenic uplift. Probability density plots of the detrital zircon ages show a dominant age peak between 500-600 Ma in all samples, representing crystallization ages related to the Pan-African orogeny. This data indicates that sediment provenance was stable throughout the evolution of the SRC, favoring the second hypothesis. However, the dominance (~50% of all grains) of Pan- African grains may be obscuring the signal of provenance change. Further work applying the composition of the samples and robust statistical analysis of the zircon ages should yield clearer results.
AAPG Search and Discovery Article #90157©2012 AAPG Foundation 2012 Grants-in-Aid Projects