Because of the moderate to good preservation of calcareous microfossils and the lessened magnetic overprint of the APC cores, both micropaleontological and paleomagnetic data can be used for chronostratigraphy. A total of 20 datum levels were found at Site 1145: six magnetic, seven calcareous nannofossil, six planktonic foraminifer, and one benthic foraminifer event (see Table T7; Fig. F12).
Figure F14 (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 resultant average sedimentation rates decrease from 227 m/m.y. in the upper ~60 m to some 40 m/m.y. down to the bottom (Fig. F14B), a difference of almost one order of magnitude. When converted to mass accumulation rates, both carbonate and noncarbonate accumulations show the same decreasing trend downhole, with a small increase in the middle part of the sequence. Variations in accumulation rate are much more significant in the noncarbonate fraction. The rate was low in the Pliocene, averaging 4 g/cm2/k.y., and then rose to 6 g/cm2/k.y. in the early Pleistocene. After 0.8 Ma, the noncarbonate accumulation exhibited an almost threefold increase to 13 g/cm2/k.y. in the last 0.26 Ma (Fig. F14; Table T11). Because this pattern of accumulation rate changes is common to other sites (e.g., Sites 1144 and 1146), its interpretation must involve basinwide, if not regional, events.