42. PALEOENVIRONMENT OF UPPERMOST MESSINIAN SEQUENCES IN THE WESTERN MEDITERRANEAN
(SITES 974, 975, AND 978)¹

Silvia M. Iaccarino² and Alessandro Bossio³

ABSTRACT

The uppermost Messinian sediments show different patterns in Holes 974B, 975B, and 978A. Hole 974B from the central Tyrrhenian Sea is characterized by rhythmically bedded claystone that is dominantly brownish and almost barren of fossil content. A transitional interval a few decimeters thick has been recorded at the top of the Lago Mare sequence at Hole 975B from the Balearic Basin. The interval is characterized by whitish-gray, finely laminated micrite and micritic silty clay yielding a Loxochonca djaffarovi (ostracode) assemblage typical of the Paratethys, interbedded with planktonic foraminifers. This transitional interval might indicate temporary incursions of marine waters.

The Messinian sequence retrieved at Hole 978A from the Alboran Sea is characterized by sandy turbidites interbedded with fine-laminated sediments.The fossil content (foraminifers, calcareous nannofossils, and ostracodes) is contradictory, because both marine and lacustrine forms occur. According to the model proposed here, the sequence was deposited in a basin fed by continental waters. Temporary incursions from the Atlantic Ocean are not documented in any part of the cores investigated.

¹Zahn, R., Comas, M.C., and Klaus, A. (Eds.), 1999. Proc. ODP, Sci. Results, 161: College Station, TX (Ocean Drilling Program).
²Department of Earth Science, University of Parma, Viale delle Scienze 78, V43100 Parma, Italy. iaccarin@ipruniv.cce.unipr.it
³Department of Earth Science, University of Pisa, via S. Maria 53, 56100 Pisa, Italy.