Cretaceous planktonic foraminifera in sediments of the Ontong Java Plateau

Age assignments are made difficult by pervasive dissolution and resedimentation that extends into the Paleogene. Deposition of the Aptian limestone at Site 807 took place at lower bathyal depths beneath the foraminiferal lysocline but above the calcite compensation depth (CCD). Deposition then continued beneath the CCD until the late Campanian or Maastrichtian when carbonate sedimentation resumed.

Within the Maastrichtian, deposition again took place at lower bathyal depths at or above the rapidly dropping CCD until the Cretaceous/Tertiary boundary when the CCD apparently rose. Small planktonic foraminifers accumulated in winnowed and redeposited fine-grained sediments whereas larger planktonic foraminifers were deposited largely in mass-flow deposits that increase in number upsection through the Maastrichtian. The increased pulses of larger planktonic foraminifers followed by the abrupt occurrence of laminated sediments, an abundance of small, globular planktonic foraminifers, and an increase in radiolarians in the latest Maastrichtian likely were the result of northward plate motion into more productive waters and different current systems.

At Site 803, deposition beneath the CCD continued from the earliest sediments above the basalt until the Eocene. Carbonate sedimentation during the late Albian to early Santonian, however, is recorded atop the plateau at Site 288. The extensive hiatuses in the Cretaceous sequence from the Ontong Java Plateau correlate in part with times of widespread hiatuses in the Pacific Basin.

Evidence of pervasive mechanical erosion during the Cenomanian to Santonian and the Campanian to Maastrichtian on the top of the plateau perhaps were caused by the longitudinal position of the plateau relative to western boundary currents and eddy effects above the plateau.