Paleontological evidence for early exposure of deep oceanic crust on the Vema Fracture Zone southern wall (Atlantic Ocean, 10°45'N)
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We present the results of a paleontological study of samples collected during the Vemanaute cruise on the Vema Fracture Zone southern wall where an almost complete section of oceanic crust is exposed. The three studied samples are poorly lithified yellowish calcareous sediments lying horizontally over gabbros. They contain abundant, generally well-preserved, and relatively diverse tropical late Neogene calcareous nannofloras and planktonic foraminiferal faunas, and yield a few poorly preserved radiolarians. The estimated ages are 8.8-10 Ma; 5.6-6.4 Ma (late Miocene); 4.5-4.2 Ma (early Pliocene), derived from deep-sea correlations between microfossil zonations and magnetic stratigraphy. Our results are compared to theoretical ages proposed for the crust in the surveyed area. This leads us to discuss the timing and location of mechanisms responsible for the exposure of the observed section and allows us to emphasize that early morphologies and structures may be preserved during the transform walls migration.