Page 185 - Carbonate Platforms Facies, Sequences, and Evolution

by
by
the
can
The
The
The
by the
be
uplift
formation
slope
Abadia
of
fluvial
diagonal ruling.
traced
Jurassic strata.
Abadia
rests
sandstones of the
and
equivalents
deposits
seismic sections, the
marginal
informal lithostratigraphic
of
formation.
of
(as the scheme is informal,
Fig. 2. Summary chart of an
formation
In
nomenclature currently under
southwards
letters. Hiatuses are shown by
the
from the base of the Oxfordian
marginal
dipping clinoforms (see Fig.
the
is
the vertical time scale from Kent
and Gradstein, (1985) is doubled
they were penetrated by the
'formation' and 'member' are not
capitalized in the text). Note that
discussion for the Triassic-Lower
tinued into the Kimmeridgian.
in capitals, members in lower case
upwards in order to accommodate
the Upper Jurassic units described
the
Cretaceous of the Lusitanian Basin
=
in the paper. Formations are shown
unconformably
basement
a sudden influx of siliciclastics,
towards
on
Abadia
marine
upper
230
190
220
170
160
210
200
140
150
180
central
highs
1000 m
part
Lisbon
earlier
part
clastics
14; and Wilson,
of
thick
Monsanto well),
during
formation
of
of
NORIAN
represented
BAJOCIAN
TOARCIAN
BATHONIAN
CALLOVIAN
BERRIASIAN
SINEMURIAN
VALANGINIAN
PLEINSBACHIAN
some structural highs, carbonate sedimentation con­
and
early Kimmeridgian, ended carbonate deposition in
many parts of the Lusitanian Basin and was followed
to the Upper Jurassic Smackover Formation of the
the
the
An abrupt rise in relative sea-lev e l, accompanied
the base of this prograding slope (Ellwood, 1987).
and limestone breccias of the Tojeira member at the
base of the clastic Abadia formation. However, on
basin, this event is marked by a sequence of shales
Gulf Coast (Crevello & Harris, 1982) and is overlain
contains up to 80 m of high-energy carbonates similar
and
capped by the Amaral Limestone formation, which
consists predominantly of shales and siltstones. On
Montejunto formation, and the Abadia formation,
1988,
fig. 7) indicating a prograding slope deposit. Coarse
the
Cabrito member accumulated at
the
(where
by
upper 550 m show southward
are
Upper
Lourinha formation. Around salt structures, and on
the eastern margin of the basin (Fig. 2), the Lourinha
the
ite,
San
slope
region
ing an
C
==
Rapid
and Mem
diapir-like
dated
�
sequences
Upper Jurassic carbonate buildups,
A
formation.
(Ramalho,
formation.
Pedro
halokinetic
B
2
as
N
southwest
deposits,
R
D
1971)
important
of
and
Martins
granitic
E
Portugal
is
--------
with
3
Mauffret et al., 1989)
formation
the
Elsewhere
N
E
is
movements
are
Oxfordian
�-"----'--..t----<--J.... _
in
Berriasian-Lower Aptian
H
a
Basin
component
intrusion
A
heralded a pre-Aptian phase
���������A
the
overlain,
formations
R
_,__._ ....__.
0
are
___
(the
.
developed
of the
sequence
basin
(Mouterde
(Wilson
(200-BOOm)
carbonate debris
. .
in
of ocean
characteristic
of
et
probably
et
Sintra
�����
of
where
al.,
flows
==
al.,
_.__._� "---------
subsidence and synsedimentary fault
D
--'-�
· s 7,oo:6�·oniJ-:- �a:
without
�
a:
<
mega­
metamorphozed marbles exposed around the gran­
form­
thermally­
mega­
.·: => �
9:::>
1971;
granite)
dated at 76-80Ma (i.e., very late Cretaceous). The
�g �
. .. . & �
Ramalho, 1971) and probably a lateral equivalent of
1989;
southwestwards towards Sintra (Fig. 3). In the latter
they are brought to the surface by a small
·------�----!<�;...,
the Montejunto formation. The overlying Ramalhao
suggested to be
Mem Martins
break, by a series of carbonate units described by
dominantly
The generalized facies pattern of siliciclastics being
replaced southwards by carbonates seen at the end
and
opening to
sequence 2 suggest a rifting episode that may have
brackish faunal elements of Tithonian age at its top
(Fig. 2). The Farta Pao formation, which contains
a
of megasequence 2 continues into megasequence 3
171
Rey (1972) which are grouped here into the Cascais ·