Unit II is Paleocene to middle Eocene limestone. Bulk density increases sharply in the lowest part of Subunit IIB, and both the water content and porosity decrease. Cretaceous limestone Unit III is subdivided on the basis of color, with the change from a white Subunit IIIA to a mottled gray and pinkish white Subunit IIIB at 1088.8 mbsf, corresponding approximately to a hiatus and condensation of the Cenomanian through upper Coniacian portion of the sequence. The main component of the tuff intervals is basaltic ash consisting of partly glassy to tachylitic fragments with abundant plagioclase microlites. Texturally, many of the fragments are similar to aphanitic pillow margins in the underlying basalts.
Most fragments are nonvesicular, but some have vesicles or scalloped margins.
The tuff is composed of at least eight normally graded beds, several of which have scoured bases. The uppermost layer grades up through parallel-laminated to cross laminated beds, indicating deposition by turbidity currents or reworking by currents. The minor moderately vesicular basaltic glass shards in these tuff beds indicate formation by relatively shallow submarine eruptions, whereas the partly glassy basaltic ash that constitutes the dominant component could have been derived from shallow-water to subaerial hydroclastic eruptions, or by erosion of a volcanic source somewhere in the summit region of the main Ontong Java Plateau. Microfossils in the interbeds indicate an age no greater than early Aptian. All eight units contain pillow basalt, defined by quenched glassy rims, grain-size variations from aphanitic near pillow margins to fine grained in the interiors, and vesicle patterns.