Plio-Pleistocene Benthic Foraminifera Stratigraphic Distribution in the Deep-Sea Record of the Tyrrhenian Sea (ODP Leg 107)

Abstract

Benthic foraminifers from Site 652, Site 653 (Hole 653A), and Site 654 of Leg 107 (Tyrrhenian Sea, Western Mediterranean), which penetrated with more or less good recovery the Plio-Pleistocene stratigraphic interval, were studied in a total of 699 close-spaced samples. A total number of 269 species have been classified and their quantitative distribution in each sample is reported. The benthic foraminifers assemblage is more diversified in Site 654, less diversified in Site 652. Less than a half of the benthic foraminifers species listed from Plio-Pleistocene Italian land sections are present in the coeval deep-sea Tyrrhenian record, in which shallow water species are missing and Nodosarids are poorly represented. A very few species have comparable stratigraphic distribution in the three deep-sea sequences and in Italian land sections when compared against calcareous plankton biostratigraphy. In the same three sites, the first appearance levels of several species are younger and younger, and last appearance levels are earlier and earlier from Site 654 to Site 653 and Site 652. Five biostratigraphic events, biochronologically evaluated and occurring at the same level in the deepsea Tyrrhenian record and in several land sections, have been selected as zonal boundaries of the proposed benthic foraminifers biostratigraphic scheme. The Plio-Pleistocene interval has been subdivided into four biozones and one subzone, recognizable both in the deep-sea and land-based sequences. The Cibicidoides^!) italicus assemblage zone stretches from the base of the Pliocene to the extinction level of the zonal marker, biochronologically evaluated at 2.9 Ma. The Cibicidoides robertsonianus interval zone stretches from the Cibicidoides^.) italicus extinction level to the Pliocene Mediterranean FO of Gyroidinoides altiformis, evaluated at 2.4 Ma. The Gyroidinoides altiformis interval zone stretches from the Mediterranean Pliocene FO of the zonal marker to the appearance level of Articulina tubulosa, evaluated at 1.62 Ma. The Articulina tubulosa assemblage zone stretches from the appearance level of the zonal marker to the Recent. In the Articulina tubulosa biozone, the Hyalinea baltica subzone is proposed. The appearance level of Hyalinea baltica is evaluated at 1.35 Ma, well above the Plio-Pleistocene boundary as defined in the Vrica stratotype section.

Molecular Phylogeny of Common Cibicidids and Related Rotaliida (Foraminifera) Based on Small Subunit Rdna Sequences

“…In the concept of the Utrecht school (e.g., van der Zwaan, 1982;van Hinsbergen and others, 2005), both species are morphologically close, and there are intermediate forms (see Schweizer, 2006 with descriptions and references therein). In addition, other authors have a different concept of C. kullenbergi (e.g., van Morkhoven and others, 1986;Sprovieri and Hasegawa, 1990;Corliss, 1991;Holbourn and Henderson, 2002), which is sometimes synonymized with Cibicidoides mundulus (van Morkhoven and others, 1986;Holbourn and Henderson, 2002). Specimens of C. kullenbergi from its type locality in the central part of the North Atlantic Ocean are therefore needed for molecular analyses to assess whether C. kullenbergi is a separate species or if it should be synonymized with C. pachyderma.…”

Vertically stacked Gilbert-type deltas of Ventimiglia (NW Italy): The Pliocene record of an overfilled Messinian incised valley

“…Palaeoenvironment could not be inferred for three samples because of the scarcity of specimens. On the basis of the literature on Mediterranean Pliocene benthic foraminifera (Wright, 1978;Katz and Thunell, 1984;Sprovieri and Hasegawa, 1990;Di Stefano et al, 1996;Sgarrella et al, 1997;Iaccarino et al, 1999a,b; and references therein), the three assemblages are linked to the following palaeoenvironments: bathyal (assemblage I in Table 1), outer-shelf/epibathyal (assemblage IIa in Table 1), middle/outer shelf (assemblage IIb) and inner shelf (assemblage III in Table 1). The results of the semiquantitative analysis with the age/biozones and the main stratigraphic markers are summarized in Table 2.…”

Late Pliocene climate variability on Milankovitch to millennial time scales: A high-resolution study of MIS100 from the Mediterranean

“…5b) probably confirms this mechanism. O. stellatus is an opportunistic benthic foraminifer and among the first taxa to re-colonise the benthic realm after the Messinian salinity crisis (Sprovieri and Hasegawa, 1990) and thought to be tolerant to salinity changes (Seidenkrantz et al, 2000). The development of a low-salinity surface water layer in contrast to severe winter mixing illustrates that different climate mechanisms interfere (a combination of Milankovitch and sub-Milankovitch related processes) making MIS100.3 an exceptional interval.…”