Geoscience Reference
In-Depth Information
Mag.
Pol.
Stratigraphic
units
Nanno-
fossil
Plank.
Foram.
Biohorizons
Diatom
AGE
Chron
Radiolaria
Ma
Reworking
#148, R1-5-2
R1-5-5
R1-5-11
R1-5-12
#150, C-1
C-2
C-3
Ma
Primary
Secondary
NPD
0
0
CN15
N.23
12
B. aquilonaris
(Ma)
D120 (0.3)
Shimosa Group
b
Axoprunum
CN14
11
a
b
angelinum
C1
1
D110 (1.0)
1
N.22
Eucyrtidium
matuyamai
Kazusa Group
CN13
10
D105 (1.6)
a
d
b
2
D100 (2.0)
2
C2
9
D95 (2.4)
c
Cycladophora
sakaii
Dictyophimus
robustus
Spongurus
pylomaticus
S. acquilonium
Lithelius
barbatus
Lychnocanoma
N.21
D90 (2.6-2.7)
CN12
3
3
8
C2A
a
D80 (3.5-3.9)
4
b
a
c
N.19
F
A. ocu.
(4.0)
Anno
Formation
4
CN11
7Bb
L
T. jack
.p (4.8)
F
T. jack.
p (5.2)
5
C3
5
b
Kiyosumi
Formation
CN10
N.18
a
D77 (5.5)
L
T. temp.
(5.4)
d
7Ba
6
b
6
c
D75 (6.4)
C3A
D73 (6.8?)
b
7
N.17
7A
7
parallelipes
CN9
C3B
a
D70 (7.6)
Cycladophora
davisiana
cornutoides
D68 (7.8-7.9)
8
a
8
C4
6B
D66 (8.4)
D65 (8.5)
D60 (9.2)
b
a
6A
9
9
CN8
D59 (9.3)
C4A
Amatsu
Formation
D58 (9.4)
5D
N.16
D57 (9.5)
CN7
CN6
D56 (10.0)
10
10
D55.8 (10.1)
Lychnocanoma
magnacornuta
C5
5C
D55.5 (10.7)
11
11
N.15
D55.2 (11.1-11.4)
b
D55 (11.5)
N.14
N.13
12
D54 (11.8-12.0)
12
5B
b
CN5
N.12
D53 (12.3-12.5)
D52 (12.7-12.8)
C5A
C5AA
C5AB
C5AC
C5AD
N.11
D52.5 (12.6-12.8)
a
Eucyrtidium
inflatum
D51 (12.9)
5A
13
13
D50 (13.1)
a
N.10
4Bb
Kinone
Formation
14
14
D48 (14.5)
D47 (14.5-14.6)
CN4
4Ba
D44 (15.0)
Eucyrtidium
asanoi
D45 (14.9)
15
N.9
D43.2 (15.2)
15
D43 (15.4)
#151, R-1
C5B
4A
D42 (15.5)
N.8
D41.5 (15.6)
D40 (15.9)
D35 (16.3)
D30 (16.9)
16
16
3B
D41 (15.7)
Sakuma Group
Calocycletta
costata
D33 (16.5)
C5C
3A
N.7
17
CN3
17
Stichocorys
wolffii
2B
FO
M. splendida
(17.8)
C5D
18
N.6
18
D25 (18.4)
C5E
CN2
19
19
Stichocorys
delmontensis
2A
C6
20
20
Hota Group
20
N.5
D20 (20.3)
F
R. hota.
(20.5)
L
C. rect.
(20.7)
21
21
C6A
CN1
c
22
Cyrtocapsella
tetrapera
1
22
C6AA
C6B
b
N.4
23
23
a
a+b
24
F
K. ezo.
(24.0)
24
C6C
Lychnocanoma
elongata
D20 (24.0)
P.22
CP19
b
D. ateuchus
C7
25
25
225
Fig. 9
Chronostratigraphy of the Neogene sequence near the Boso triple junction (Magnetic
polarity time scale from Cande and Kent (
1995
) and Berggren et al. (
1995
); radiolarian zones from
Motoyama (
1996
) and Riedel and Sanfilippo (
1978
);
nannofossil
zones from Okada and Bukry
(
1980
); planktonic foraminiferal zonation from Blow (
1969
); diatom zones from Yanagisawa and
Akiba (
1998
))
The ages of all the other samples analyzed were 0-0.3 Ma, but they also
contained reworked Miocene and Pliocene species (Fig.
9
). The stratigraphic
range of the reworked Miocene diatoms was within the interval from the
D. lauta
Zone (NPD4A) to the
D. katayamae
Zone (NPD 6A); most were in
either the
D. lauta
Zone (NPD4A) or the
D. hyalina
Zone (NPD4B). No
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