Page 200 - Carbonate Platforms Facies, Sequences, and Evolution

ate
the
186
was
Fig.
nate
slight
extends
3).
anomaly
Discussion
facies to
anomaly,
over
shallowing-up
Setting and age
penetrated
Compactional
shown
water carbonate
throughout
an
the
progradation
by
in
the
east
to
area
thicknesses of at least
drape
the
sequence
of
Fig.
the
of
At both locations,
tar-impregnated sands (Fig.
=
of the
11
sequence
sedimentation
SALT-CONTROLLED
and outcrops at Cabo Espichel
west
12).
is
only a few hundred metres thick.
tated with siliciclastic fluvial sands.
Lourinha,
consisting
was
(Fig.
200 km 2 •
Tithonian
Barreiro
It
12).
Barreiro #1 and 2 also show
and
up formed a trap in which an oil column >
composed
has
have been derived from the Barreiro buildup.
BUILDUPS
Campelos
(for locations,
principally
The
of
P.M. Ellis, R. C. L.
that cap the Barreiro buildup suggest that shallow­
in­
stones of facies association 8 and 9 occur interdigi­
Cretaceous siliciclastic sands over the Barreiro build­
mudstones and wacke­
Speculation concerning the nature of the carbon­
deeper-water facies associations 1, 2 and 3 predomi­
a shal­
drowning and the partial break-up of the buildup.
Ramalhal wells (see Fig. 3 for locations). The wells
terminated by
see
200m
high accumulated, but was later oxidized to produce
Breccias of equivalent age encountered in Monsanto
#1, 15 km across the Tagus estuary in Lisbon, may
the Caldas da Rainha- Vimeiro salt structure, which
A large buildup developed on the southeast side of
a
of
facies associations 4, 5 and 7, which is capped by a
1500 m, but at outcrop it is
lowing trend overlain by a deep-water cap, but the
Core data from Barreiro #4 indicates that the seismic
conclusion consistent with the shallowing trends seen
in the wells. The deep-water limestones and breccias
deep-water sequence of associations 1, 2 and 3. In
the more basinal areas to the west and northwest of
and northwest- a
clined reflectors at the margin of the anomaly suggest
Bombarral Sub-basin, which was subsiding due to
and
Lower
been
only be based on data available from Montijo #1
brought to the surface around the salt structure, and
buildup can
the Cabac;;os Formation, showed the buildup reached
show that the buildup thickens eastwards into the
salt withdrawal. Ramalhal #1, which did not reach
&
c
lime
tors,
down
(facies
quence
clastics
part of
the
to
Core data
uncertain.
consisting
Wilson and R.R.
mentation
represents
the
are
The 1500m
? Solenopora
Biohermal
microsolenid
Ramalhal #1
of
the Ramalhal
whereas
from
Kimmeridgian.
Kimmeridgian.
in
Seismic features
the
mudstones
a
thinner
more
2460 m)
a
the
upper part of the
fossiliferous packs
association
At
buildup
limestones (Fig. 15).
corals,
Leinfelder
4,
buildup
zone
extremely
of the
lower
The presence
limestones
relatively
thickest
of
generally
consists
core
of
probably
thin
shows
part
of
outcrop,
and these
the overlying Tojeira member.
1),
a
the
occur
and
parallel
does
Montejunto
has not been substantiated by drilling.
consist
fine-grained
stromatoporoids
within
passing
continued
high
shallow-water buildup
development
three-fold
fine-grained wackestone
the
and
into
carbonate
higher-energy
not show
into
of
order of 200 m, and beyond this on both Figs
shallowing-upwards
sequence penetrated by Ramalhal
of heads
sedi­
strong reflectors. In Figs 14a & b, mounded reflec­
se­
is characterized by high amplitude mounded reflec­
fossi-
age limit with precision, which may extend into the
certainly Oxfordian in age, though no detailed faunal
Abadia formation
Dating of the Ramalhal-Serra d'el Rei buildup is
and floral information is available to state its upper
over the buildup in the subsurface means that it is
amplitude
near Ramalhal #1. Both sections show that the top
Figure 14 shows two seismic lines through the buildup
Montejunto formation in the Basin. As at Barreiro,
relief on the apparent slope into the basin is of the
tors also show a progradational pattern. The positive
14a
such
reflectors may be caused by deep-water ammonitic
the
Abadia-equivalent
matrix.
#1
This interpretation
the
formation and
Numerous types of encrusters are present, including
division
some
tones and grainstones (association
more
lower
(represented by core 7 starting at 2057 m, to core 18
5 and 7), which in turn are capped by deeper-water
and bryozoa. The biohermal facies shows little vuggy
of
thrombolitic crusts, skeletal algae, stromatoporoids
sequence
limestones
porosity, but is cut by numerous small fractures. The