13. PLEISTOCENE CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY AND THE WESTERN MEDITERRANEAN SAPROPELS, SITES 974 TO 977 AND 979 1

During Ocean Drilling Program Leg 161, six sites were drilled in the western Mediterranean. Pleistocene sediments were cored at Sites 974, 975, 976, 977, and 979. Occurrences of generally very abundant and well-preserved calcareous nannofossils provide a new Pleistocene biostratigraphic framework based on a succession of twenty biohorizons. Calibration of these datums with the orbital time scale, based on the average of June and July (summer) insolation time series at 65 °N of the astronomical solution La90(1,1), gives the following ages in Ma: (FO, first occurrence) Emiliania huxleyi >Gephyrocapsa spp. (0.070); (FcO, first consistent occurrence) E. huxleyi (0.218); (FO) E. huxleyi (0.270); (LO, last occurrence) Pseudoemiliania lacunosa (0.406); (LO) P. lacunosa lacunosa (>7 µm) (0.439); (LO acme) P. lacunosa (0.739); (LO) Crenalithus asanoi (cir.; >6.5 µm) (0.781); (FO) Gephyrocapsa omega (>4) (0.962); (FO) C. asanoi (circular; >6.5 µm) (1.122); (LO) Gephyrocapsa spp. (>6.5 µm) (1.235); (LO) Helicosphaera sellii (1.246); (LcO, last consistent occurrence) H. sellii (1.276); (FO acme) P. lacunosa (1.361); (FO) Gephyrocapsa oceanica (>6.5 µm) (1.494); (FO) Gephyrocapsa caribbeanica (>6.5 µm)-G. oceanica (>6.3 µm) (1.525); (FO) G. oceanica (>5.5 µm) (1.566); (FO) Gephyrocapsa spp. (>5 µm) (1.615); (LO) Calcidiscus macintyrei (cir.; >11 µm) (1.619); (FO) G. oceanica (>4) (1.719); FO G. caribbeanica (>4) (1.726). Sapropels (organic-rich layers) interlayered in pelagic and hemipelagic Pleistocene sediments recorded at each western Mediterranean site are calibrated with the orbital time scale and numbered following the codification of the insolation cycles. Sixty-eight insolation cycles were recognized in these Pleistocene sediments from a total of 88 insolation cycles for the Pleis tocene (= 176 insolation minima and maxima). The western Mediterranean Sites 974‐979 represent sections with continuous sapropel records that span the entire Pleistocene and indicate that the temporal sapropel pattern is not evenly distributed. Th e calibration of the western Mediterranean sapropels to the orbital time scale and to the oxygen isotope stratigraphy provides pr ecise stratigraphic correspondence that will be used to compare the timing of eastern and western Mediterranean sapropel cyclicity. Four new combinations are also introduced: Crenalithus asanoi, Crenalithus japonicus, Pseudoemiliania pacifica, and Pseudoemiliania lacunosa ovata.