Sedimentation in the latest Messinian at Capo Rossello.

Ten samples from a Late Messinian section measured at Capo Rossello, a few hundred metres laterally from and stratigraphically, immediately below the Miocene Pliocene boundary stratotype, have been invesitigated by various techniques: carbonate content, grain-size analysis, loss on ignition, clay mineral composition, frequency of euryhaline ostracods, Two lithological sub-units, with different palaeoenvironmental implications, are recognized. Both sub-units were deposited after the termination of evaporitic conditions, and immediately after deposition of an ash fall tuff. The lower unit is the Congeria marl which yields the lago-mare' faunal assemblage, the autochthony of which is supported by biometrical analysis of Cyprides agrigentina, indicating brackish, shallow-water conditions with Paratethyan affinities, and the upper, the Arenazzolo, a thin sandy unit indicating a higher' energy environment whose duration is estimated at some thousand years. Marine faunas yielded by the Arenazzolo are interpreted as allochthonous, Sedimentary slructures suggest a littoral setting at the edge of the lake, or a delta lobe. The main environmental change occurs at the base of the immediately overlying Trubi Formation. where open marine condilions indicative of oceanic depths mark the termination of the Messinian salinity crisis. [ABSTRACT FROM AUTHOR]