A 379.4-mcd-thick (333.1 mbsf) upper Paleocene (~59 Ma) to Pleistocene pelagic sediment sequence was recovered at Site 1266. Ninety-three biostratigraphic datums and twenty-five magnetostratigraphic datums (Table T13) were used to construct an age-depth model for this site (Table T14; Fig. F31). Linear sedimentation rates (LSRs), total mass accumulation rates (MARs), and carbonate MARs were calculated at 1-m.y. intervals (see "Age Model and Mass Accumulation Rates" in the "Explanatory Notes" chapter).
The main objective of Site 1266 was to recover a complete and well-resolved upper Paleocene to lower Eocene section, and the site was chosen to yield this critical stratigraphic interval at a relatively shallow burial depth. The sediment section from Site 1266 is therefore characterized by significant condensed intervals and unconformities in the younger section, particularly the middle Eocene interval (47–37 Ma; 259–251 mcd) and the upper Miocene (9.9–8.7 Ma; 79–76 mcd). Biostratigraphic and magnetic reversal datums are generally in good agreement, the exception being a lower to upper Oligocene interval where magnetic tie points agree better with planktonic foraminifers than with calcareous nannoplankton datums.
LSRs range between <1 and 26 m/m.y., and total MARs range from <0.1 to 3.4 g/cm2/k.y. Total MAR fluctuations essentially represent variations in carbonate MAR. LSRs and carbonate MARs were highest from 57 to 52 Ma (late Paleocene–early Eocene). The interval corresponding to 51–37 Ma has very low accumulation rates and comprises a major condensed interval/unconformity. It is followed by the upper Eocene to lower Miocene section with moderately high LSRs and MARs. Distinctly low accumulation rates are indicated for the middle Miocene (18–11 Ma) and for the upper Miocene interval that comprises an unconformity (10–6 Ma). The Pliocene–Pleistocene rates are of moderate magnitude (~1 g/cm2/k.y.).
Noncarbonate MARs averaged over 1-m.y. intervals are generally low (<0.3 g/cm2/k.y.), and the small fluctuations are probably within the analytical uncertainty of the data. The highest values in the interval from 57 to 52 Ma are an exception and might be related to the occurrence of carbonate-poor intervals of a few centimeters to several decimeters in length (see "Lithostratigraphy" and "Geochemistry"). These short-term carbonate dissolution events are smoothed out in the MAR record as a result of our 1-m.y. sampling of the age-depth model, dictated by the limited resolution of the shipboard age-depth control points and density and carbonate data.