CONCLUSION

The Eocene sediments from Holes 1051A and 1052A contain abundant to common calcareous nannofossil assemblages, which are moderately to well preserved in the upper to middle Eocene and moderately to poorly preserved in the lower Eocene. These holes contain nannofossil sequences that range from Zone CP8 to Subzone CP15a. The sedimentation rate curves for Hole 1051A and 1052A suggest a hiatus at Sample 171B-1051A-41X-CC, 16-18 cm, through 42X-1, 81-83 cm, and Sample 171B-1052A-19X-4, 63-65 cm, through 19X-5, 64-66 cm. These breaks span 2 m.y. and 17 m.y., respectively.

My examination of coccolith size for genus Coccolithus, Reticulofenestra, Cribrocentrum, and Cribrocentrum may suggest a trend of increasing size upward in the sedimentary sequence; however, Dictyococcites does not exhibit a similar simple trend. The major nannofossil assemblage changes dramatically from Toweius to Reticulofenestra at the early middle Eocene (nannofossil Subzone CP12a), but no major change in nannoflora was observed across the Eocene/Paleocene boundary. Toweius crassus, which is the marker species for the Zone CP10/CP11 boundary, made a gradational change to Toweius callosus; they are difficult to distinguish from each other in Hole 1051A. Therefore, this report could not identify the nannofossil Zone CP10/CP11 boundary. According to Bralower and Mutterlose (1995), the LO of Sphenolithus furcatolithoides is close to the FO of Dictyococcites bisectus. However, the LO of S. furcatolithoides seems to be present at the bottom of D. bisectus acme in Hole 1051A. Discoaster sublodoensis occurs together with Tribrachiatus orthostylus in Sample 171B-1151A-42X-1 through 44X-2, possibly suggesting reworking in this interval.