The Eocene/Oligocene boundary and the Latdorfian (Lower Oligocene) A statement by the German Subcommission on Tertiary Stratigraphy
Martini, E.; Fahlbusch, V.; Hagn, H.
published: Jul 12, 1986
ArtNo. ESP026001701009, Price: 29.00 €
The Eocene/Oligocene boundary as identified by calcareous nannoplankton is commonly placed at the last occurrence of the rosetteshaped discoasters which dominate in the Eocene, especially the last occurrence of Discoaster saipanensis (top of Zone NP 20; Martini 1971) in deep-sea sediments and land-based sections of low and middle latitudes. It has been employed in this way in the international Deep Sea Drilling Project (DSDP) since 1969. Several authors that have discussed the dating of the Eocene/Oligocene boundary by calcareous nannoplankton and planktonic foraminifera (e.g. Bombita & Rusu, 1981, Snyder et al. 1984) have shown that the boundary determined using planktonic foraminifera (commonly the last occurrence of Globorotalia cerroazulensis) is slightly younger than that determined using calcareous nannoplankton and occurs in the lower part of nannoplankton Zone NP 21. The time-span between the two boundary " events " is about 0.4 m.y. as determined from the sedimentation rate at Site 592 (DSDP Leg 90, Martini 1986). In high latitudes, discoasters are generally rare or missing and thus not so reliable for indicating the position of the Eocene/Oligocene boundary. However, Cribrocentrum reticulatum last occurs just below the Eocene/Oligocene boundary (top of Zone NP 20, last occurrence of D. saipanensis) in low and middle latitudes and can also be used as a reliable substitute species at high latitudes (Müller 1978).