A 368.0-mcd-thick (329.3 mbsf) Maastrichtian (~68 Ma) to Pleistocene pelagic sediment sequence was recovered at Site 1267. A total of 116 biostratigraphic datums and 29 magnetostratigraphic age-depth tie points (Table T13) were used to construct an age-depth model for this site (Table T14; Fig. F28). 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 1267 was to recover a complete and well-resolved Maastrichtian to lower Eocene section, and the site was chosen to yield this critical stratigraphic interval at a relatively shallow burial depth. The sediment section at Site 1267 is therefore characterized by significant condensed intervals and unconformities throughout the middle Eocene to upper Miocene section, with unconformities identified at 42–34 Ma (151–146 mcd), 30–23 Ma (126–125 mcd), ~22.8–10.5 Ma (113–108 mcd), and 10.5–7.4 Ma (108–113 mcd). The age-depth model relies primarily on paleomagnetic and nannofossil data. Planktonic foraminiferal data generally agree with the calcareous nannofossil data but show considerably more scatter in some intervals, particularly the upper Paleocene to lower Eocene. Discrepancies in the interval between ~100 and 150 mcd result from massive reworking and severe dissolution, resulting in a condensed section interrupted by unconformities. Discrepancies in the upper Paleocene–lower Eocene probably result from the low resolution of shipboard studies and lack of intercalibration.
LSRs range between <1 and 26 m/m.y., and total MARs range from <0.1 to 3.0 g/cm2/k.y. Both LSR and MAR show high values in the Maastrichtian (67–65 Ma), low to moderate values in the lower Paleocene (65–60 Ma), and a broad peak from 60 to 50 Ma. Two minor peaks in the middle Eocene (50–42 Ma) and in the lower Oligocene (43–31 Ma) are separated by an interval of very low LSR and MAR that comprise a middle and late Eocene condensed interval/unconformity. The upper Oligocene to upper Miocene interval (31–7 Ma) is condensed and comprises two major unconformities. The Pliocene–Pleistocene interval has moderately high LSRs and MARs, apparently peaking at 5–4 Ma.
Noncarbonate MARs averaged over 1-m.y. intervals are generally low (<0.3 g/cm2/k.y.) throughout the section, and total MAR fluctuations essentially represent variations in carbonate MAR. The moderately high noncarbonate MAR values in the P/E boundary interval (56–54 Ma) are an exception. They result from carbonate-poor intervals a few centimeters to several decimeters thick (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.