At Site 1198, 13 calcareous nannofossil and 8 planktonic foraminifer datums were established for the 523-m-thick lower Miocene to Pleistocene sequence (Fig. F16; Table T6) (see "Biostratigraphy and Paleoenvironments"). Mechanical problems and poor recovery prevented the construction of a magnetostratigraphy (see "Paleomagnetism"). The age model is therefore based on the biostratigraphy.
As at other Leg 194 sites, recovery of Megasequence D at Site 1198 (0-201 mbsf) was excellent and biostratigraphic resolution good. The interval sedimentation rates range from 9 to 110 m/m.y. (average 53 m/m.y.) and are the highest rates for this Pliocene-Pleistocene sequence among all Leg 194 sites. A major hiatus separates Megasequence C from Megasequence D at 203 mbsf and lasted from 7.6 to 3.8 Ma (±0.5 m.y.). As at Site 1197, recovery of Megasequence C and the upper part of the underlying sequences is very poor and microfossils are rare and poorly preserved. The error bars associated with the biostratigraphic datums are accordingly large (Fig. F16). Miocene interval sedimentation rates range from 15 to 48 m/m.y. (average 28 m/m.y.).
Age picks for lithologic and seismic unit boundaries are summarized in Table T7.