Page 206 - Carbonate Platforms Facies, Sequences, and Evolution

of
the
the
the
192
into
Fig.
and
The
blocks
consist
similar
Ranging
19a.
limestone
Mem
limestone
pure
of
other
of
mudstones
transported
breccias
limestone
from
presence
carbonate-shale
shales
and
to Read's
Martins
corals
breccias
of
bioclasts
lithoclasts
limestones
contemporaneous
0.2m
limestone
Transported
and
breccias
were
(175-207 m,
(1980,
to
passing
within
(Fig.
sequence,
are
The Mem Martins formation
largely
up
corals
formation
abundant
the
over
1982)
18).
(Ramalho,
and
into
deposited
which
containing large
4m
clasts
karstification.
280-355m
The
lithified limestones in the source area.
as
indicate
composed
in
of
composed
in
pers.
breccias,
stromatoporoids,
passes
of
base
of
that
deep-water
ammonitic
Fig.
of
it
P.M. Ellis, R. C.L.
suggest that the source area lay to the northwest.
sedimentary boudinage structures and other slope­
water caps of both the Barreiro and Ramalhal build­
the Tojeira member at Montejunto and the deep­
297m in Fig. 18) does not contain Tojeira-like lime­
stone breccias. Ammonitic lime mudstones continue
but is probably virtually contemporaneous with the
Thin-bedded
were deposited as sheet or lobate debris flows (Ellis,
formation is marked by the first appearance of thick
however,
allochthonous
1984). None of the clasts show conclusive evidence
this
ribbon
area consisting of a reef bypass margin must be ruled
lime
stromatoporoids
arranged
not a significant component of the breccias, a source
debris or turbidity flows. The background sediments
thin-bedded
18),
chaotically within a matrix of calcareous shale. They
packstones and grainstones occur in association with
background sediments. As lithified reefal debris is
wackestones (facies association 4), as well as some
previously
thickness,
angular
The Mem Martins formation is formed of a mixed
upwards
comm.).
a change in inclination at the toe of slope (Fig. 19a
& 20). Tool marks at the base of one debris flow,
to 355m, and they contain thrombolitic bindstones
The lack of breccias in the inland exposures to the
east suggests that their disappearance was caused by
ups. The age of the lithified limestones is not known
indicate that small patch-reefs were growing on the
and flute marks at the bases of carbonate turbidites
marine
was
The top part of the Mem Martins formation (above
out, and a fault scarp origin favoured as depicted in
carbonates. Ellis (1984) concluded that the lack of
lithified limestone member is similar to that found in
related structures in the breccia-dominated part of
deposited on a slope inclined at less than one degree.
in
up
part
ramp
which
stones
The
1984).
vealed
the
solenid
a
Summary
the
Wilson and R.R.
lithologies
formation,
Berriasian.
formations
deep-water
of the
wackestones
conditions
ramp
are
and
coral biostromes.
faunal
which
basin
Mem
similar
into
top part of
bindstones
Leinfelder
to
to
was
lateral
the
from the
and coraliferous
shallowing-up
The Farta Pao formation
the
Martins
diversity
fully
packstones
prograded
shallower
Mem
of
upper
equivalents
carbonate
marine
progressively
waters.
formation
Martins
part
coral-chaetitid
of
bioherms
and
southwards
(association
Mem
the
(Fig.
Small
system developed represented by the
of the
sequence
6),
scars and debris flows also occurred (Fig. 19b).
20).
during
rubble beds which have
limited lateral extent. These are overlain by fossi­
by shales and allochthonous packstones and wacke­
con­
from thrombolitic bindstones, through algal-micro­
ammonitic lime mudstones on the coast is overlain
annulata, Campbelliella striata) (facies association 8)
east beneath Lisbon, where the Monsanto well re­
slump
coastal sequences. An erosional surface above the
a
framestones
miliolid foraminifera and dasyclads (Salpingoporella
are the main constituent of this formation. The top
of cyclinid foraminifera Anchispirocyclina lusitanica,
of the formation contains condensed horizons, minor
Nodular lime mudstones containing a restricted biota
taining coral-chaetitid framestone patch-reefs and
by the Farta Pao formations marks an abrupt change
The restricted lagoonal environment represented
formation and heralds the platform conditions of the
phaceloid coral bushes which pass up into nerineid
Martins
interpreted as a prograding carbonate ramp, across
formation is
increased
sandstones and oyster-encrusted firmgrounds (Ellis,
liferous Tubiphytes wackestones (association 4) with
and algal microsolenid bindstones to the east of the
The Ramalhao and lower part of the Mem Martins
Abadia
upper
20). Once the basin had almost filled, a carbonate
A
with
similar pattern of sedimentation occurs 25 km to the
postulated fault scarp to the northwest (Figs 19 &
relative sea-level stillstand. In the Sintra area, the
a
passively
Mem
filled by shales and debris flows originating from a