Eocene-Oligocene planktonic foraminifera of ODP Hole 135-841B

A middle Eocene to lower Oligocene sedimentary sequence was drilled at Site 841 in the Tonga forearc region during Ocean Drilling Program Leg 135. A 56-m-thick sequence of volcanic sandstone, spanning from Cores 135-841B-4IR to -47R (549.1 to 605 mbsf), unconformably overlies rhyolitic volcanic basement. The middle Eocene planktonic foraminifer assemblages (P Zone?), which occur in association with larger benthic foraminifers, include spinose species of Acarinina, Morozovella, and Truncorotaloides, but their abundance is low. Late Eocene and early Oligocene faunas are abundant and show the highest diversity of the Paleogene sequence drilled at this site. They have been assigned to Zones P15-16 and P18, respectively. The Eocene/Oligocene boundary was not recognized because of a hiatus in which Zone P17 (37.2-36.6 Ma) was missing. Another hiatus is recorded in the interval between the middle and late Eocene, spanning at least 1.8 Ma. […]