Table 2. Summary of biostratigraphic use, biochronology, occurrence in Leg 167 material, and reliability of Pleistocene (0-1.80 Ma) calcareous nannofossil biohorizons.

Table 2. Summary of biostratigraphic use, biochronology, occurrence in Leg 167 material, and reliability of Pleistocene (0-1.80 Ma) calcareous nannofossil biohorizons.

Code

Biohorizon

Previous use

Previous biochronology

Occurrence in sites

Reliability and biochronology in the study area

P8
P. lacunosa LO Definition of the bottom of Zone NN20 and Subzone CN14b Late MIS 12, at an age of 0.46 Ma (2) 1010, 1011, 1012, 1013, 1014, 1016, 1017, 1018, 1019, 1020, 1021B Good; calibrated to middle part of C1n. Most probably synchronous with previous evaluation

P7
R. asanoi LO Proposed first as useful event in the Pleistocene by (6) and proved useful on global scale (7) MIS 22 (7), at an age of 0.88 Ma (9) 1014 Not sufficiently tested; at Site 1014 calibrated in middle part of C1r; age = 0.88 Ma

P6
Gephyrocapsa sp.3 FO = Gephyrocapsa spp. C-D FO (2) = medium Gephyrocapsa spp. re-entrance (4) Proposed as useful event in the Mediterranean early Pleistocene (4) and proved useful on global scale although diachronous in different water masses (7, 8). Most probably corresponds to the G. oceanica FO of Bukry (1973), and hence, defines the base of CN14 Diachronous. MIS 27, at an age of 1.00 Ma (10); MIS 29 (eastern equatorial Pacific), lower part of MIS 25 (Atlantic, mid latitudes) (8) 1010, 1011, 1012, 1013, 1014, 1016, 1017, 1018, 1019, 1020, 1021, 1022 The species is rare and discontinuous; the first rare occurrence was detected at base of C1r.1r (Sites 1010 [0.885 ± 0.115 Ma], 1014 [0.940 ± 0.003 Ma], 1020 [0.975 ± 0.005 Ma], and 1021 [0.995 ± 0.015 Ma]) in agreement with age estimated in mid- to high-

P5
large Gephyrocapsa LO = Gephyrocapsa spp. A-B (2) LO Proposed first as useful event in the Mediterranean early Pleistocene (4) and proved useful on global scale (8) MIS 37, at an age of 1.24 Ma (8) 1010, 1012, 1014, 1017, 1018, 1020 Good and apparently synchronous with previous evaluations; calibrated to the upper part of C1r.2r (Sites 1010 (1.34 ± 0.05 Ma) and 1020 (1.232 ± 0.002 Ma)

P4
H. sellii LO First proposed by (3) as useful early Pleistocene event, it has been shown to be time transgressive (5, 7, 8) Diachronous. MIS 37/38 transition, at an age of 1.25 Ma; MIS 49 (eastern equatorial Pacific) (8) 1011, 1012, 1016, 1017, 1018, 1022 Not reliable; the species is rare and discontinuous

P3
large Gephyrocapsa FO = Gephyrocapsa spp. A-B > 5.5 (2) FO Proposed first as useful event in the Mediterranean early Pleistocene (4) and proved useful on global scale, although diachronous in different water masses (7, 8) Diachronous. MIS 55/56 transition, at an age of 1.58 Ma (11); MIS 48 (eastern equatorial Pacific) (8) 1010, 1012, 1013, 1014, 1017, 1018, 1020 Fairly good; calibrated to the lower part of C1r.2r at an age of 1.46 ± 0.06 Ma (Site 1010)

P2
G. oceanica s.l. FO = medium Gephyrocapsa FO (4) = Gephyrocapsa A-B FO (2) First proposed by (1) as useful early Pleistocene event, proved useful on global scale and isochronous (7, 8) MIS 59/60 transition, at an age of 1.69 Ma (8) 1010, 1011, 1012, 1013, 1014, 1016, 1018, 1020, 1021, 1022 Fairly good; calibrated to the lower part of Cr1r.2r (Sites 1010 [1.635 ± 0.115 Ma] and 1021 [1.765 ± 0.045 Ma])

P1
C. macintyrei LO First proposed by (3) as earliest Pleistocene event, it has been show to be time transgressive (7, 8) Diachronous. MIS 57/58 transition, at an age of 1.67 Ma; MIS 55 (western equatorial Atlantic) (8) 1010, 1011, 1012, 1013, 1014, 1016, 1020, 1021, 1022 Not reliable: it occurs consistently just below or with G. oceanica s.l. FO. Calibrated to the base of C2n (Site 1021 [1.915 ± 0.015 Ma]) or in the lower part of C1r.2r (Site 1010 [1.635 ± 0.115 Ma])

Notes: MIS = marine isotopic stage. FO = first occurrence, LO = last occurrence. Underline = site with magnetostratigraphy, bold = reference site. References: (1) = Boudreaux and Hay in Hay et al., 1967; (2) = Thierstein et al., 1977; (3) = Gartner, 1977; (4) = Rio, 1982; (5) = Backman and Shackleton, 1983; (6) = Takayma and Sato, 1987; (7) = Wei, 1993; (8) = Raffi et al., 1993; (9) = Bassinot et al., 1994; (10) = I. Raffi (unpubl. data); (11) = L.J. Lourens et al. (unpubl. data).

Code	Biohorizon	Previous use	Previous biochronology	Occurrence in sites	Reliability and biochronology in the study area
P8	P. lacunosa LO	Definition of the bottom of Zone NN20 and Subzone CN14b	Late MIS 12, at an age of 0.46 Ma (2)	1010, 1011, 1012, 1013, 1014, 1016, 1017, 1018, 1019, 1020, 1021B	Good; calibrated to middle part of C1n. Most probably synchronous with previous evaluation
P7	R. asanoi LO	Proposed first as useful event in the Pleistocene by (6) and proved useful on global scale (7)	MIS 22 (7), at an age of 0.88 Ma (9)	1014	Not sufficiently tested; at Site 1014 calibrated in middle part of C1r; age = 0.88 Ma
P6	Gephyrocapsa sp.3 FO = Gephyrocapsa spp. C-D FO (2) = medium Gephyrocapsa spp. re-entrance (4)	Proposed as useful event in the Mediterranean early Pleistocene (4) and proved useful on global scale although diachronous in different water masses (7, 8). Most probably corresponds to the G. oceanica FO of Bukry (1973), and hence, defines the base of CN14	Diachronous. MIS 27, at an age of 1.00 Ma (10); MIS 29 (eastern equatorial Pacific), lower part of MIS 25 (Atlantic, mid latitudes) (8)	1010, 1011, 1012, 1013, 1014, 1016, 1017, 1018, 1019, 1020, 1021, 1022	The species is rare and discontinuous; the first rare occurrence was detected at base of C1r.1r (Sites 1010 [0.885 ± 0.115 Ma], 1014 [0.940 ± 0.003 Ma], 1020 [0.975 ± 0.005 Ma], and 1021 [0.995 ± 0.015 Ma]) in agreement with age estimated in mid- to high-
P5	large Gephyrocapsa LO = Gephyrocapsa spp. A-B (2) LO	Proposed first as useful event in the Mediterranean early Pleistocene (4) and proved useful on global scale (8)	MIS 37, at an age of 1.24 Ma (8)	1010, 1012, 1014, 1017, 1018, 1020	Good and apparently synchronous with previous evaluations; calibrated to the upper part of C1r.2r (Sites 1010 (1.34 ± 0.05 Ma) and 1020 (1.232 ± 0.002 Ma)
P4	H. sellii LO	First proposed by (3) as useful early Pleistocene event, it has been shown to be time transgressive (5, 7, 8)	Diachronous. MIS 37/38 transition, at an age of 1.25 Ma; MIS 49 (eastern equatorial Pacific) (8)	1011, 1012, 1016, 1017, 1018, 1022	Not reliable; the species is rare and discontinuous
P3	large Gephyrocapsa FO = Gephyrocapsa spp. A-B > 5.5 (2) FO	Proposed first as useful event in the Mediterranean early Pleistocene (4) and proved useful on global scale, although diachronous in different water masses (7, 8)	Diachronous. MIS 55/56 transition, at an age of 1.58 Ma (11); MIS 48 (eastern equatorial Pacific) (8)	1010, 1012, 1013, 1014, 1017, 1018, 1020	Fairly good; calibrated to the lower part of C1r.2r at an age of 1.46 ± 0.06 Ma (Site 1010)
P2	G. oceanica s.l. FO = medium Gephyrocapsa FO (4) = Gephyrocapsa A-B FO (2)	First proposed by (1) as useful early Pleistocene event, proved useful on global scale and isochronous (7, 8)	MIS 59/60 transition, at an age of 1.69 Ma (8)	1010, 1011, 1012, 1013, 1014, 1016, 1018, 1020, 1021, 1022	Fairly good; calibrated to the lower part of Cr1r.2r (Sites 1010 [1.635 ± 0.115 Ma] and 1021 [1.765 ± 0.045 Ma])
P1	C. macintyrei LO	First proposed by (3) as earliest Pleistocene event, it has been show to be time transgressive (7, 8)	Diachronous. MIS 57/58 transition, at an age of 1.67 Ma; MIS 55 (western equatorial Atlantic) (8)	1010, 1011, 1012, 1013, 1014, 1016, 1020, 1021, 1022	Not reliable: it occurs consistently just below or with G. oceanica s.l. FO. Calibrated to the base of C2n (Site 1021 [1.915 ± 0.015 Ma]) or in the lower part of C1r.2r (Site 1010 [1.635 ± 0.115 Ma])