206
Chapter 5 Oceanic Sediments
SHELF OFF NAMIBIA
a
o
YOUNG PHOSPHORITE
SHELL SAND
NODULES
100
<:I
0
0
~
"\iI'~" ••• :.::'!~:':'"
0
<:;)
.
' . , . : . '
~.:"~,:",, /" " ' : ', : ~:, ",; ', ',' ,:~'.:' : ,',',' OLD PHOSPHORITES
200
C~ASTIC SANDS
DIATOMACEOUS
(EARLY QUATERNARY
AND SILTS
OOZE OR MUD
OR PRE-QUATERNARY)
EROSION AL UNCONFORMITY I - - .-v20 km --;
300
WATER DEPTH
I'V 400 m
CATHAM RISE OFF NEW ZEALAND
POST -MIOCENE EROSION
AND REDEPOSITION
m
SEVERAL EPISODES OF LATE MIOCENE
b 2
PHOSPHATIZATION (NODULES AND
C BLAKE PLATEAU, OFF FLORIDA
CALCARENITE
PHOSPHORITE,
Fe-Mn-IMPREG :
T
SOm
1
NATED
_~i*f0il®iMWji;;'_j
SILTY LIMESTONE
1-------- 2 km - - - - - - - - l
Fig. 5.9. a Schematic cross-section of continental
margin demonstrating zones of different sedimentation rates, condensation, and phosphorite ages. This
situation resembles that of the present-day shelves
off Namibia and Peru. (After Baturin 1982),
b Phosphorites on the Chatham Rise to the east of
N ew Zealand, in two stages of development (b 1 and
b2), concentrated at the ridge crest by pronounced
erosion and reworking, The primary phosphate-bearHARDGROUND)
d SENONIAN, PARIS BASIN
PHOSPHATIC
TERTIARY
CHALK
CHALK (SENONIAN)
HARDGROUND
I
1 km
I
ing strata (Late Miocene) can only be observed at the
ridge flanks. (After von Rad and Kudrass 1984),
c Model of phosphorite lag deposits of the inner
Blake Plateau, derived from Miocene strata and exhumed by the Gulf Stream, (After Manheim et al.
1980), d Senonian phosphorites of the Anglo-Paris
Basin, concentrated on top of hardgrounds in
current-eroded channels and troughs, (After Jarvis
1980)
Chapter 5 Oceanic Sediments
SHELF OFF NAMIBIA
a
o
YOUNG PHOSPHORITE
SHELL SAND
NODULES
100
<:I
0
0
~
"\iI'~" ••• :.::'!~:':'"
0
<:;)
.
' . , . : . '
~.:"~,:",, /" " ' : ', : ~:, ",; ', ',' ,:~'.:' : ,',',' OLD PHOSPHORITES
200
C~ASTIC SANDS
DIATOMACEOUS
(EARLY QUATERNARY
AND SILTS
OOZE OR MUD
OR PRE-QUATERNARY)
EROSION AL UNCONFORMITY I - - .-v20 km --;
300
WATER DEPTH
I'V 400 m
CATHAM RISE OFF NEW ZEALAND
POST -MIOCENE EROSION
AND REDEPOSITION
m
SEVERAL EPISODES OF LATE MIOCENE
b 2
PHOSPHATIZATION (NODULES AND
C BLAKE PLATEAU, OFF FLORIDA
CALCARENITE
PHOSPHORITE,
Fe-Mn-IMPREG :
T
SOm
1
NATED
_~i*f0il®iMWji;;'_j
SILTY LIMESTONE
1-------- 2 km - - - - - - - - l
Fig. 5.9. a Schematic cross-section of continental
margin demonstrating zones of different sedimentation rates, condensation, and phosphorite ages. This
situation resembles that of the present-day shelves
off Namibia and Peru. (After Baturin 1982),
b Phosphorites on the Chatham Rise to the east of
N ew Zealand, in two stages of development (b 1 and
b2), concentrated at the ridge crest by pronounced
erosion and reworking, The primary phosphate-bearHARDGROUND)
d SENONIAN, PARIS BASIN
PHOSPHATIC
TERTIARY
CHALK
CHALK (SENONIAN)
HARDGROUND
I
1 km
I
ing strata (Late Miocene) can only be observed at the
ridge flanks. (After von Rad and Kudrass 1984),
c Model of phosphorite lag deposits of the inner
Blake Plateau, derived from Miocene strata and exhumed by the Gulf Stream, (After Manheim et al.
1980), d Senonian phosphorites of the Anglo-Paris
Basin, concentrated on top of hardgrounds in
current-eroded channels and troughs, (After Jarvis
1980)