Qualernary
upper
Pliocene
lower
Pliocene
upper
Miocene
middle
Miocene
'"
. .
J
<>
~
lower
Miocene
upper
Oligocene
lower
Oligocene
...
Eocene
' "
:!.
..
:f
0
10
20
30
40
50
Deep Sea Cherts
235
o 200 400 600 800 1000 1200 1400
Dissolved silica (~M)
Fig. 8.16. Acoustic refl ectors in pelagic sediments on Ontong Java Plateau (Site 805) (/eji) and
dissolved si licate in associated drilling sites (Site 805 : open triangles) (righ!) . Site 805 is just north
of the equator. Water depth is 3188 m. T he sed im ent down to the Ontong Java Series reflectors is
calcareous ooze and chalk. Tota l sedim ent thickness is abo ut 1 km. Chert beds first appear near the
top of the Ontong Java Series and are middl e to late Eocene in age . Dissolved silicate drops at that
horizon, indicating precipitation. [W. H. Berger, L. W. Kroenke , L. A. Mayer, et al. . 1991 . Proc.
Ocean Drilling Progr. Init. Rpts. 130: 497; si li cate measurements by M. Delane y]
upper
Pliocene
lower
Pliocene
upper
Miocene
middle
Miocene
'"
. .
J
<>
~
lower
Miocene
upper
Oligocene
lower
Oligocene
...
Eocene
' "
:!.
..
:f
0
10
20
30
40
50
Deep Sea Cherts
235
o 200 400 600 800 1000 1200 1400
Dissolved silica (~M)
Fig. 8.16. Acoustic refl ectors in pelagic sediments on Ontong Java Plateau (Site 805) (/eji) and
dissolved si licate in associated drilling sites (Site 805 : open triangles) (righ!) . Site 805 is just north
of the equator. Water depth is 3188 m. T he sed im ent down to the Ontong Java Series reflectors is
calcareous ooze and chalk. Tota l sedim ent thickness is abo ut 1 km. Chert beds first appear near the
top of the Ontong Java Series and are middl e to late Eocene in age . Dissolved silicate drops at that
horizon, indicating precipitation. [W. H. Berger, L. W. Kroenke , L. A. Mayer, et al. . 1991 . Proc.
Ocean Drilling Progr. Init. Rpts. 130: 497; si li cate measurements by M. Delane y]