New Micropaleontological Investigations Deciphering Shallow and Deep Environments in the Alboran Basin around the Miocene – Pliocene Boundary

Speranta - Maria Popescu, Nadia Barhoun, Mihaela Carmen Melinte- Dobrinescu, Frédéric Quilévéré, Damien Do Couto, Jean-Pierre Suc, Christian Gorini, and Laurent Jolivet

Between 6 and 5 Ma (Late Miocene – Early Pliocene), the Alboran Sea area was affected by important events relative to regional tectonics and huge changes in sea-level (Messinian Salinity Crisis). Peripheral shallow basins (Sorbas, Níjar, Malaga) and the deep Alboran Basin (ODP Sites 976, 977 and 978) display peculiar deposits enriched in fossils originated from the former Paratethys (bivalvia: dreissenids and lymnocardiids; ostracods; dinoflagellate cysts), the northeastern sea adjacent to the Mediterranean; including the Black Sea. Such deposits have been grouped within a single chronostratigraphic unit correlative to the Miocene – Pliocene (i.e. Messinian – Zanclean) boundary, the so-called “Lago Mare” Unit, which is supposed to represent temporary low salinity conditions.

New micropaleontological investigations at high chronological resolution, using dinoflagellate cysts, calcareous nannoplankton and foraminifers, were performed on such deposits in order to characterize their environmental conditions.

It appears that such facies from the peripheral basins illustrate high sea-level conditions with a temporary connection between the Mediterranean and Paratethys and mark exclusively the marine reflooding ending the Messinian Salinity Crisis.

In addition, some sediments from these basins yielded dinoflagellates under their cellulosic form (i.e. theca: generally unpreserved at the difference of cyst). The occurrence of these exceptionally well-preserved dinoflagellates indicate a very fast sedimentary burying that we interpret as the signature of instantaneous floods such as tsunamis in relation with the intense seismic activity of the region.

AAPG Search and Discovery Article #90161©2013 AAPG European Regional Conference, Barcelona, Spain, 8-10 April 2013