Page 209 - Carbonate Platforms Facies, Sequences, and Evolution

1
ate
� 0
I'�
bution,
x>�'- \.. �,
On the
significant
t
0 �
ooid sands.
grainstones
buildups
LATE
salt structure
day
Recapitulation
of
east
Jurassic of the
North
resulting
Present
on flanks of rising
the
with
side
in
sequences deposited
influence
grai nstone dominated
CARB ONATE
POSSIBLE
the
on
OXFORDIAN
shelf
Lusitanian
of the
Amaral
PORTUGAL
Basin;
basin,
late Oxfordian and late Kimmeridgian.
carbonate
<0
CONTROLS
the
geometries
?
formation
development
�\
faults
?
their stratigraphical relationships in Fig. 4.
of
ON
DEVELOPMENT
facies
were
l? �ta
during
IN
exerted
Montejunto
carbon­
distri­
inter­
geographical
distribution of three of them is shown in Fig. 21, and
Four carbonate sequence types occur in the Upper
a
developed slightly downslope from the shelf break
formed at the shelf break of the southern prograding
Abadia formation slope system. To the south, in the
Arruda region, the coral biostromes appear to have
preted by Ellwood (1987) as an ooid bar system that
In the Torres Vedras-Montejunto area, the ooid
the
3
2
break
shales,
1500 m)
( = 1000 m)
Upper Jurassic carbonate buildups,
developed.
wackestones
Oxfordian -
facies
break facies.
uncertain
debris
-environment
The
or
LATE KIMMERIDGIAN
and
siliciclastic sands
Portugal
flows
top
of a rising salt pillow
and
significant
of the
Kimmeridgian.
low-
packstones
relatively low subsidence rates.
profile on seismic sections (Fig.
structure.
to
lateral
Oxfordian-Kimmeridgian
17).
buildup
Kimmeridgian-Tithonian
/
�
mixed
[22]
facies
developed
shows
siliciclastic
in
shelf
Sequence
m1xed carbonate
Ota rimmed shelf
seismic
buildups
D buildups
These developed dis­
progra­
structures as they were protected by a distinct shelf­
No distinct shelf­
Montejunto and Ota buildups were aggradationaL
Fig. 21. Sketch maps showing the occurence of carbonate buildups in the southern part of the Lusitanian Basin during the
anomalies
tinct lateral facies zonations, and in the case of the
Carbonate muds form a significant proportion of the
southwest of the basin. This sequence, which lacks
dational features and the development of a shelf-like
high-energy grainstones, developed as a prograding
zonation
of
moderate-energy
Following the Kimmeridgian rifting event a thick
the
ramp deposit and is interpreted as a passive basin fill
On the northwest side of the basin, a thick (up to
fault blocks (200-500m, Figs 7, 10 & 13) indicating
The buildups are relatively thin over
coarsening-up
grainstone-dominated buildup formed on the flank
195
grai nstone
carbonate ­
siliciclastic deposition