Table 4. Summary of biostratigraphic use, biochronology, occurrence in Leg 167 material, and reliability of late Miocene (5.33-11.20 Ma) calcareous nannofossil biohorizons.

Table 4. Summary of biostratigraphic use, biochronology, occurrence in Leg 167 material, and reliability of late Miocene (5.33-11.20 Ma) calcareous nannofossil biohorizons.

Code

Biohorizon

Previous use

Previous biochronology

Occurrence in sites

Reliability and biochronology in the study area

LM20
C. acutus FO Definition of the bottom of Subzone CN10b Within C3r, at an age of 5.37 Ma (7) 1010, 1011, 1014, 1016, 1021 Not reliable; the genus is underrepresented. Calibrated to C2Ar in Site 1010 and to the base of C2An.3n in Hole 1021B.

LM19
D. quinqueramus LO Definition of the bottom of Subzone CN10a Repeatedly calibrated in low to mid latitude to the mid C3r (4) at an age of 5.54 Ma (7) 1010, 1011, 1014, 1016, 1021 The marker is rare and discontinuous. At low-latitude Site 1010 it has been associated with mid C3r at an age of 5.55 ± 0.05 Ma, in agreement with previous evaluations.

LM18
N. amplificus LO Proposed as definition of the bottom of Subzone CN9bC (5) Associated with the top of C3An (4), at an age of 5.99 Ma (7) Undetected

LM17
N. amplificus FO Proposed as definition of the bottom of Subzone CN9bB (5) Associated with the base of C3An (4), at an age of 6.84 Ma (7) Undetected

LM16
R. pseudoumbilicus PE Used as useful event in Subzone CN9b (4) Associated with the lower part of C3Ar (4), at an age of 7.1 Ma (7) 1010, 1011, 1014, 1021? Fairly reliable; calibrated to C3Ar at low-latitude Site 1010 at an age of 7.11 ± 0.01 Ma, in agreement with previous evaluations.

LM15
A. primus FO Definition of the bottom of Subzone CN9b Associated with C3Br.2r (4), at an age of 7.39 Ma (7) 1010, 1011, 1021 Apparently reliable; see text.

LM14
M. convallis LO Event in Subzone CN9a (4) Associated with C4n.2n (equatorial Pacific) (4), at an age of 7.8 Ma (6) 1010, 1011 Regionally fairly good

LM13
D. berggrenii FO Definition of the bottom of Subzone CN9a
Associated with lowermost C4r (4), at an age of 8.28 Ma (7) 1010, 1011, 1021? Poor reliable: the marker is rare and discontinuous in the mid latitude Site 1021B.

LM12
D. loeblichii FO Definition of the bottom of Subzone CN9a Associated with lower part of C4r (4), at an age of 8.43 Ma (5)
Not reliable; the marker is very rare and discontinuous.

LM11
D. neorectus FO Definition of the bottom of Subzone CN9a
Undetected

LM10
R. pseudoumbilicus PB Definition of the bottom of Subzone CN8b Associated with upper part of C4An (4), at an age of 8.78 Ma (7) 1010, 1011, 1021 Moderately reliable, even if the marker is near barren intervals.

LM9
M. convallis FO Used as alternative event to define the bottom of Zone CN8 (1) Associated with the top of C5n for (3) and with C4Ar.2r for (4), at an age of 9.3/9.5 Ma (6) 1010, 1021 Regionally fairly reliable

LM8
D. hamatus LO Definition of the bottom of Zone CN8 Age 9.63 Ma (7), calibrated in low latitude to C4Ar.2r (4), in mid to high latitude in C4Ar.2 (2) and C5n/C4Ar (3) 1010 Poorly reliable; the marker is absent in the mid-latitude Site 1021B.

LM7
C. calyculus LO Useful event near the top of Zone CN7 Associated with the bottom of C4Ar, at an age of 9.694 Ma (7) 1010, 1021 Fairly reliable

LM6
C. coalitus LO Useful event near the top of Zone CN7 Associated with the top of C5n, at an age of 9.67 Ma (7) 1010, 1021 Moderately reliable; the marker is rare and discontinuous.

LM5
D. hamatus FO Definition of the bottom of Zone CN7 Repeatedly calibrated in low to mid latitude to the mid Cn.2n (4) at an age of 10.47 Ma (7) 1010 Undetected

LM4
C. calyculus FO Definition of the bottom of Subzone CN7b Associated with C5n.2n (6), at an age of 10.7 Ma (7) 1010 Undetected

LM3
C. miopelagicus LCO Useful event in Zone CN6 (4) Associated with the base of C5n.2n (4) at an age of 10.941 Ma (7) 1010, 1021 Undetected

LM2
D. bellus FO Useful event to approximate the bottom of Zone CN7 Associated with lower part of C5n.2n (4) 1010, 1021 Undetected

LM1
C. coalitus FO Definition of the bottom of Zone CN6 Repeatedly calibrated in low latitude to lowermost C5n.2n (4) at an age of 10.79 Ma (7) 1010 Undetected

Code	Biohorizon	Previous use	Previous biochronology	Occurrence in sites	Reliability and biochronology in the study area
LM20	C. acutus FO	Definition of the bottom of Subzone CN10b	Within C3r, at an age of 5.37 Ma (7)	1010, 1011, 1014, 1016, 1021	Not reliable; the genus is underrepresented. Calibrated to C2Ar in Site 1010 and to the base of C2An.3n in Hole 1021B.
LM19	D. quinqueramus LO	Definition of the bottom of Subzone CN10a	Repeatedly calibrated in low to mid latitude to the mid C3r (4) at an age of 5.54 Ma (7)	1010, 1011, 1014, 1016, 1021	The marker is rare and discontinuous. At low-latitude Site 1010 it has been associated with mid C3r at an age of 5.55 ± 0.05 Ma, in agreement with previous evaluations.
LM18	N. amplificus LO	Proposed as definition of the bottom of Subzone CN9bC (5)	Associated with the top of C3An (4), at an age of 5.99 Ma (7)	Undetected
LM17	N. amplificus FO	Proposed as definition of the bottom of Subzone CN9bB (5)	Associated with the base of C3An (4), at an age of 6.84 Ma (7)	Undetected
LM16	R. pseudoumbilicus PE	Used as useful event in Subzone CN9b (4)	Associated with the lower part of C3Ar (4), at an age of 7.1 Ma (7)	1010, 1011, 1014, 1021?	Fairly reliable; calibrated to C3Ar at low-latitude Site 1010 at an age of 7.11 ± 0.01 Ma, in agreement with previous evaluations.
LM15	A. primus FO	Definition of the bottom of Subzone CN9b	Associated with C3Br.2r (4), at an age of 7.39 Ma (7)	1010, 1011, 1021	Apparently reliable; see text.
LM14	M. convallis LO	Event in Subzone CN9a (4)	Associated with C4n.2n (equatorial Pacific) (4), at an age of 7.8 Ma (6)	1010, 1011	Regionally fairly good
LM13	D. berggrenii FO	Definition of the bottom of Subzone CN9a	Associated with lowermost C4r (4), at an age of 8.28 Ma (7)	1010, 1011, 1021?	Poor reliable: the marker is rare and discontinuous in the mid latitude Site 1021B.
LM12	D. loeblichii FO	Definition of the bottom of Subzone CN9a	Associated with lower part of C4r (4), at an age of 8.43 Ma (5)		Not reliable; the marker is very rare and discontinuous.
LM11	D. neorectus FO	Definition of the bottom of Subzone CN9a		Undetected
LM10	R. pseudoumbilicus PB	Definition of the bottom of Subzone CN8b	Associated with upper part of C4An (4), at an age of 8.78 Ma (7)	1010, 1011, 1021	Moderately reliable, even if the marker is near barren intervals.
LM9	M. convallis FO	Used as alternative event to define the bottom of Zone CN8 (1)	Associated with the top of C5n for (3) and with C4Ar.2r for (4), at an age of 9.3/9.5 Ma (6)	1010, 1021	Regionally fairly reliable
LM8	D. hamatus LO	Definition of the bottom of Zone CN8	Age 9.63 Ma (7), calibrated in low latitude to C4Ar.2r (4), in mid to high latitude in C4Ar.2 (2) and C5n/C4Ar (3)	1010	Poorly reliable; the marker is absent in the mid-latitude Site 1021B.
LM7	C. calyculus LO	Useful event near the top of Zone CN7	Associated with the bottom of C4Ar, at an age of 9.694 Ma (7)	1010, 1021	Fairly reliable
LM6	C. coalitus LO	Useful event near the top of Zone CN7	Associated with the top of C5n, at an age of 9.67 Ma (7)	1010, 1021	Moderately reliable; the marker is rare and discontinuous.
LM5	D. hamatus FO	Definition of the bottom of Zone CN7	Repeatedly calibrated in low to mid latitude to the mid Cn.2n (4) at an age of 10.47 Ma (7)	1010	Undetected
LM4	C. calyculus FO	Definition of the bottom of Subzone CN7b	Associated with C5n.2n (6), at an age of 10.7 Ma (7)	1010	Undetected
LM3	C. miopelagicus LCO	Useful event in Zone CN6 (4)	Associated with the base of C5n.2n (4) at an age of 10.941 Ma (7)	1010, 1021	Undetected
LM2	D. bellus FO	Useful event to approximate the bottom of Zone CN7	Associated with lower part of C5n.2n (4)	1010, 1021	Undetected
LM1	C. coalitus FO	Definition of the bottom of Zone CN6	Repeatedly calibrated in low latitude to lowermost C5n.2n (4) at an age of 10.79 Ma (7)	1010	Undetected

Notes: FO = first occurrence, LO = last occurrence, LCO = last common and continuous occurrence. PB = paracme beginning, PE = paracme end. Underline = site with magnetostratigraphy, bold = reference site. References: (1) = Rio, Fornaciari, et al., 1990; (2) = Olafsson, 1991, (3) = Gartner, 1992; (4) = Raffi et al., 1995; (5) = Raffi and Flores, 1995; (6) = Berggren, Kent, et al., 1995; (7) = Backman and Raffi, 1997.