Page 204 - Carbonate Platforms Facies, Sequences, and Evolution

190
1979,
clastics.
1988;
slope angle
�
shallow-water
in
coarn
Setting and age
se
I
POSTRIFT
feldspathic
sandstones
Wilson
distal
et
carbonate
PASSIVE
locations
SEQUENCE
al., 1989)
JDJI��������
BASIN
sedimentation
halted
with a rifting event in the Kimmeridgian
drowned towards the end of the Oxfordian.
_=_
FILL
ramp
===;= = _= _;
appears to have developed initially on a ramp pro­
of mounded, slightly progradational seismic reflec­
break-up of the older Montejunto formation build­
develop, and this may have prevented the develop­
sedimentation throughout much of the basin, though
Dramatically increased subsidence rates associated
(Wilson,
duced as the Vimeiro-Caldas da Rainha structure
continued
ups (of which the major examples have already been
The southern part of the basin, however, remained
described) and was followed by the influx of Abadia
tors at the top of the buildup, and the increase in
rose to produce a broad salt pillow. The development
ment of a distinct lateral facies zonation. The buildup
suggest that it was
beginning to develop a shelf profile before it was
on palaeohighs into the Middle Kimmeridgian. This
event was accompanied by the drowning and partial
carbonate
�
Caba<;:os fm.
�
'-�--
�
is
an
�
by
>
posit
a
-.
of the
consists
stones (j) with reefal framestones
. - ._. a � --: 7;\� :::- --:;;; �=== = =�"'" �===��=+=:i""' ;;;= ===== =;; :;::; ;:;;:;; � t== �r - :;:: ;:-: �==� sea -level and boundstones 5 2o oo and pack I 0 0 intraclastic/bioclastic grainstones 400 ]metreS I I I #1 #1 BOLHOS-PO SE NW CAMPELOS P.M. Ellis, R. C. L.
discerned
�-�--�=---.- •. _- _-- -
:.-
.
Oxfordian
wackestones and
of
limestones.
-:
1
�
to
but
oncolitic wackestones
Jurassic.
prograded
Ramalho (1971)
:,.._:--- ,
: -- - -
equivalence
Tubiphites wackestones,
@
its
lowermost Upper
1000m thick
seismic
to
Wilson and R.R. Leinfelder
Farta Pao formation:
The
Ramalhao formation:
into
�
in which characteristic
side of the basin, showing the distribution of the facies associations described in Table 1.
and
reflectors :::
Mem Martins formation:
shallowing-upwards
Berriasian.
the
implied
RAMALHAL
It
is
age
Monsanto
newly
formations above the San Pedro:
lithofacies
Lower to Middle Kimmeridgian
',_:- ���s--'�
Tithonian -lowermost Berriasian
Middle Kimmeridgian-Tithonian
limestone
and
shallow-water
ranges in age
thermally-metamorphozed
types
divided
borehole
basin
deepened
from
purity
into
'
sequence.
(Fig.
Fig. 17. Interpretative cross-section across the Oxfordian-Kimmeridgian salt structure related buildup on the northwest
the west, near Sintra, a carbonate-shale slope de­
The sequence was studied in detail by Ellis (1984).
3)
To
starved of coarse clastics throughout the remainder
basin.
On the basis of studies of foraminifera and algae,
The sequence exposed on the coast at Praia Abano
four
Upper
cannot be
These Upper Jurassic carbonates are now exposed
around the diapir-like late Cretaceous Sintra granite.
limestones
shows the basin filled with shales which are capped
assigned the following ages to the
which are shown on the summary log of Fig. 18. The
lithostratigraphic units (see Fig. 2), the top three of
Oxfordian San Pedro formation
Montejunto
imply