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In-Depth Information
Table 11.3
Stratigraphic data of the Dekese section
Base
depth
(km)
Top
depth
(km)
Surface
porosity
(%)
Density of
deposit fluid
(km/m
3
)
Age
(Ma)
Porosity-depth
coeff. (km
-1
)
Dry sediment
density (km/m
3
)
Bathymetry
(km)
Eustasy
(km)
Elevation
(km)
Unit
Hiatus
318.1 1.677
1.677
0.270
0.490
2,650
0.000
0.000
1
0.200
D9
298
1.677
1.554
0.342
0.532
2,680
0.020
0.080
1,000
0.120
D7 + D8
251
1.554
0.755
0.486
0.616
2,740
0.100
0.040
1,000
0.240
D6
199.6 0.755
0.715
0.510
0.630
2,750
0.020
0.000
1,000
0.460
Overburden 183
0.715
0.715
0.318
0.518
2,670
0.020
0.060
1,000
0.400
D5
149
0.715
0.705
0.294
0.504
2,660
0.010
0.160
1,000
0.000
D4
143
0.705
0.398
0.282
0.497
2,655
0.000
0.120
1
0.040
Hiatus
112
0.398
0.398
0.270
0.490
2,650
0.000
0.180
1
0.120
D3
100
0.398
0.318
0.294
0.504
2,660
0.020
0.260
1,000
0.040
D2
93.6
0.318
0.037
0.330
0.525
2,675
0.010
0.280
1,000
0.020
Overburden 65.5
0.037
0.037
0.342
0.532
2,680
0.010
0.230
1,000
0.070
D1
33.9
0.037
0.001
0.270
0.490
2,650
0.000
0.220
1
0.150
Hiatus
0
0.001
0.001
0.270
0.490
2,650
0.000
0.000
1
0.370
Table 11.4
Eroded units in the Dekese section
Overburden unit age (Ma)
Erosion age (Ma)
Eroded thickness (km)
Eustasy (km)
183
158
0.700
0.330
65.5
55.8
0.300
0.070
Table 11.5
Stratigraphic data of the Gilson section
Base
depth
(km)
Top
depth
(km)
Surface
porosity
(%)
Density of
deposit fluid
(km/m
3
)
Age
(Ma)
Porosity-depth
coeff. (km
1
)
Dry sediment
density (km/m
3
)
Bathymetry
(km)
Eustasy
(km)
Elevation
(km)
Unit
Hiatus
350
3.107
3.107
0.270
0.490
2,650
0.000
0.120
1
0.080
G9
318.1 3.107
2.889
0.342
0.532
2,680
0.020
0.000
1,000
0.200
G8
298
2.889
2.646
0.366
0.546
2,690
0.050
0.080
1,000
0.120
G7
251
2.646
1.536
0.462
0.602
2,730
0.080
0.040
1,000
0.240
G6
199.6 1.536
0.998
0.294
0.504
2,660
0.020
0.000
1,000
0.460
Overburden 183
0.998
0.998
0.318
0.518
2,670
0.020
0.060
1,000
0.400
G5
149
0.998
0.890
0.342
0.532
2,680
0.010
0.160
1,000
0.000
G4
143
0.890
0.728
0.282
0.497
2,655
0.000
0.120
1
0.040
Hiatus
112
0.728
0.728
0.270
0.490
2,650
0.000
0.180
1
0.120
G3
100
0.728
0.567
0.390
0.560
2,700
0.100
0.260
1,000
0.040
G2
93.6
0.567
0.234
0.366
0.546
2,690
0.020
0.280
1,000
0.020
Overburden 65.5
0.234
0.234
0.342
0.532
2,680
0.010
0.230
1,000
0.070
G1
33.9
0.234
0.001
0.474
0.609
2,735
0.000
0.220
1
0.150
Hiatus
0
0.001
0.001
0.270
0.490
2,650
0.000
0.000
1
0.370
Kwango Groups) there is strong biostratigraphic and sedi-
mentological evidence for a short Kimmeridgian marine
incursion (Taverne
1975
; Chap.
8
, this Topic). Thus, at that
time, the basin surface is considered to have remained just
below this local paleo-eustatic maximum (i.e. 160 m above
present day sea-level; Fig.
11.4
) during deposition of the
Upper Jurassic to Lower Cretaceous shallow marine to
continental Stanleyville Group and Dekese Formation. The
paleo-elevation of the CB is then again increased by about
100 m to account for the overlying middle and Upper Creta-
ceous fluvial-lacustrine sequences (the Loia, Bokungu and
Upper Kwango Groups) and to remain just above the high
Table 11.6
Eroded units in the Gilson section
Overburden unit age
(Ma)
Erosion age
(Ma)
Eroded thickness
(km)
Eustasy
(km)
183
158
0.7
0.33
65.5
55.8
0.3
0.07
marks a regional unconformity near the Permian-Triassic
boundary (e.g. Turner
1999
; Catuneanu et al.
2005
; Johnson
et al.
2006
).
At the base of the overlying Jurassic-Cretaceous
sequences of the CB (the Stanleyville, Loia, Bokungu and
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