The chronostratigraphy of Site 1146 is derived from a combination of calcareous nannofossil and planktonic foraminiferal events and paleomagnetic polarity stratigraphy. The Neogene section at Site 1146 yielded 32 calcareous nannofossil events, 27 planktonic and one benthic foraminiferal events, and three paleomagnetic datums (see "Biostratigraphy" and "Paleomagnetism").
Figure F15 (also given as Synergy Software KaleidaGraph plots and Microsoft Excel data files [see the "Supplementary Materials" contents list]) shows the linear sedimentation rate and mass accumulation rate curves based on calculations described in "Sedimentation and Accumulation Rates" in the "Explanatory Notes" chapter. The sedimentation rates generally decrease downhole from a maximum of 350 m/m.y. over the uppermost 20 mcd to a minimum of ~30 m/m.y. in the lower Miocene (587-643 mcd) (Fig. F15; Table T11). Sedimentation rates in the Pleistocene average ~110 m/m.y.; in the Pliocene, ~38 m/m.y.; and in the Miocene, ~27 m/m.y. When converted to mass accumulation rates and partitioned into carbonate and noncarbonate components, extremely high total accumulation rates (>19 g/cm2/k.y.) are observed over the past 0.26 Ma (Fig. F15). Accumulation rates over the entire Pleistocene average 9.5 g/cm2/k.y., with noncarbonate components dominant. Pliocene and Miocene total accumulation rates are relatively constant and average 7 and 4 g/cm2/k.y., respectively; carbonate accounts for about half of the accumulation. An increase in rates occurs near the early/middle Miocene boundary at ~17 Ma. The carbonate accumulation rates at Site 1146 are high for a midslope basin, which should accumulate mostly terrigenous sediments. The reasonably high sedimentation and carbonate accumulation make Site 1146 an excellent record for the identification of orbital-scale variability well into the Miocene.