INTRODUCTION

In 1996, Sites 1039 through 1043 were drilled on the lower continental slope and the bottom of the Middle American Trench off the Nicoya Peninsula, Costa Rica, in the East Pacific Ocean (Fig. F1). Planktonic foraminifers were obtained from 377 samples of the total 487 examined. In this article, biostratigraphic and chronostratigraphic analyses of these planktonic foraminifers are presented.