Table 5. Summary of biostratigraphic use, biochronology, occurrence in Leg 167 material, and reliability of middle Miocene (11.20-13.52 Ma) calcareous nannofossil biohorizons.

Table 5. Summary of biostratigraphic use, biochronology, occurrence in Leg 167 material, and reliability of middle Miocene (11.20-13.52 Ma) calcareous nannofossil biohorizons.

Code

Biohorizon

Previous use

Previous biochronology

Occurrence in sites

Reliability and biochronology in the study area

MM6
D. kugleri LO Used as alternative event to define the bottom of Zone CN6 Associated with C5r.2n (6), at an age of 11.55 Ma (8)
1010
Not sufficiently tested; at Hole 1021B the marker is probably in a barren interval.

MM5
D. kugleri FO Definition of the bottom of Subzone CN5b Associated with lower part of C5r (6), at an age of 11.79 Ma (8)
1010
Not sufficiently tested; at Hole 1021B the marker is probably in a barren interval.

MM4
C. macintyrei >11 mm FO Event within Subzone CN5b (2) Associated with C5An.2n at Site 845 (6), at an age of 12.38 (7)
1010
Probably reliable; at Hole 1021B the marker is near a barren interval.

MM3
C. floridanus LO Used as alternative event to define the bottom of Subzone CN5b Age 13.24 Ma (7), associated with C5AAr for (7) and with the lower part of C5r for (3)
1010
Not sufficiently tested; the marker is present only at Site 1010, but apparently its stratigraphic position is similar to in the North Atlantic Ocean.

MM2
C. premacintyrei LO Useful event to subdivide Zone CN5 (1, 5) Age 12.22 Ma (7), associated with C5An.2n for (6) and C5An.1n for (5)
1010
Not sufficiently tested; the marker is present only at Site 1010.

MM1
S. heteromorphus LO Definition of the bottom of Subzone CN5a Associated with C5ABr (4) (6), at an age of 13.52 Ma (8)
1010
The marker is present only at Site 1010.

Code	Biohorizon	Previous use	Previous biochronology	Occurrence in sites	Reliability and biochronology in the study area
MM6	D. kugleri LO	Used as alternative event to define the bottom of Zone CN6	Associated with C5r.2n (6), at an age of 11.55 Ma (8)	1010	Not sufficiently tested; at Hole 1021B the marker is probably in a barren interval.
MM5	D. kugleri FO	Definition of the bottom of Subzone CN5b	Associated with lower part of C5r (6), at an age of 11.79 Ma (8)	1010	Not sufficiently tested; at Hole 1021B the marker is probably in a barren interval.
MM4	C. macintyrei >11 mm FO	Event within Subzone CN5b (2)	Associated with C5An.2n at Site 845 (6), at an age of 12.38 (7)	1010	Probably reliable; at Hole 1021B the marker is near a barren interval.
MM3	C. floridanus LO	Used as alternative event to define the bottom of Subzone CN5b	Age 13.24 Ma (7), associated with C5AAr for (7) and with the lower part of C5r for (3)	1010	Not sufficiently tested; the marker is present only at Site 1010, but apparently its stratigraphic position is similar to in the North Atlantic Ocean.
MM2	C. premacintyrei LO	Useful event to subdivide Zone CN5 (1, 5)	Age 12.22 Ma (7), associated with C5An.2n for (6) and C5An.1n for (5)	1010	Not sufficiently tested; the marker is present only at Site 1010.
MM1	S. heteromorphus LO	Definition of the bottom of Subzone CN5a	Associated with C5ABr (4) (6), at an age of 13.52 Ma (8)	1010	The marker is present only at Site 1010.

Notes: FO = first occurrence; LO = last occurrence. References: (1) = Theodoridis, 1984; (2) = Rio, Fornaciari, et al., 1990; (3) = Olafsson, 1991; (4) = Miller et al, 1991; (5) = Gartner, 1992; (6) = Raffi et al., 1995; (7) = Raffi and Flores, 1995; (8) = Backman and Raffi, 1997.