All the principal biostratigraphies, plus a good set of paleomagnetic reversals, are defined in Holes 1219A and 1219B (Tables T11, T12). Paleomagnetic reversals are used to calculate the average linear sedimentation rates (LSRs) for Site 1219 through most of the section. An unusually good set of magnetic reversals were obtained in the slowly accumulating near-surface sediments, and these extend through the section recovered by APC methods (Table T11). The age of the base of the hole is based on the top of the planktonic foraminifer M. acuta datum (54.25 Ma) (Table T12).
Calcareous nannofossils and radiolarians are present in the uppermost part of the section; however, reworking of the radiolarians make their biostratigraphic events less reliable (Fig. F22). The two uppermost nannofossil events lie close to the uppermost paleomagnetic reversal sequence. From the middle Miocene-middle Oligocene, all three fossil groups were useful in establishing age control. In most of the Eocene, both radiolarians and nannofossils are present (Fig. F22), although the occurrence of nannofossils is spotty through the radiolarian ooze of lithologic Unit III (see "Biostratigraphy").
The siliceous clays of lithologic Unit I (see "Lithostratigraphy") have an LSR of ~1 m/m.y. The LSR in the alternating siliceous and calcareous clays of lithologic Unit II reaches nearly 6 m/m.y. in the lower Miocene-upper Oligocene part of the section (Tables T11, T12; Fig. F22). Piston Core EW9709-12P (Lyle, 2000), taken in the survey area, can be correlated to the density records of Hole 1219A (Fig. F23). The lower part of the site survey piston core (from ~7 to 13 m) closely approximates variations in sediment density at Site 1219 (22-32 mcd; Fig. F23). This correlation is constrained by radiolarian events in both Site 1219 and piston Core EW9709-12P.
Through the remainder of the carbonate-rich Oligocene, the LSR is near 16 m/m.y. Below the E/O boundary, there is a sharp drop in LSRs along with the abrupt disappearance of carbonate from the sediments. A second maximum in LSRs of ~8.6 m/m.y. is present in the silica-rich middle Eocene radiolarian ooze of lithologic Unit III (Fig. F22). The LSR is low near the base of the middle Eocene near the appearance of the first significant chert layers (see "Lithostratigraphy").
LSR values may be combined with the dry bulk density (DBD) data from porosity measurements on individual samples (see "Physical Properties") (Table T17) to determine the bulk MARs of the sediments (Table T13). Sediment with an LSR of 1.0 cm/k.y. and a DBD of 1.0 g/cm3 will have a MAR value of 1.0 g/cm2/k.y. The observed values are rarely this high, so we report the data in milligrams per square centimeter per thousand years (mg/cm2/k.y.). MAR flux values are low in lithologic Unit I, generally <75 mg/cm2/k.y. (Fig. F24). Lithologic Unit II, dominated by calcareous material, accumulates at 500-1500 mg/cm2/k.y., with the maximum flux rates in the very light brown to white nannofossil ooze of early Oligocene age. Unit III, dominated by radiolarian ooze and radiolarite, has much lower MARs of ~200-400 mg/cm2/k.y. The basal chalk of lithologic Unit IV accumulated at rates of ~200-400 mg/cm2/k.y.