Page 105 - Carbonate Platforms Facies, Sequences, and Evolution

in
as
in
has
pale
grey
does
after
some
there
Unit.
the
peated
distinct
general,
is
deposits.
the
been
turbation
Rasquera
separated
colour,
a
This facies
deep ramp.
five
is
brown.
wackestones
the
proximal
Baix
order
is
Daonella Unit
microbuildups.
laminae.
and
Unit
not reach
wackestone
top
by thin
times
deep
(Calvet & Tucker,
The
contain
in
intepreted
progressive
more
forming
beds
mostly
as
surface
the
ramp.
interpreted
millimetre-scale
are
facies
than
Ebre-Priorat
filling
as
the madstone
This facies is
has
(5)
cycles,
is
a
consists
of
Marlstone with thin-interbedded
thin-shelled
an
paper
0· 5 m
generally absent and
marlstones and
beds
23-40 m
of
shallowest-water facies of the cycles.
the
in
Domain.
intermediate
are
towards the top of this facies package.
basinal
five
thick
interpreted
interpreted
bivalves,
irregular,
Bedding is poorly defined, but
The
deep
as
0· 2- 1· 0m thick.
lamination.
boundary is defined by a hardground surface.
as
facies.
inter-reef
1· 5-12m thick,
Rasquera limestones-dolomites and shales with
thickness.
pressions by the lower part of the Alcover Unit.
generally
varies from a bivalve-ammonoid coquina to an as­
echino­
Bio­
thickness of this facies varies from 0·3 to 6 m. Thin­
the
The Rasquera Unit facies constitute five principal
re­
de­
fossils are rare.
limestones facies.
are, in general, laminated lime mudstone, with scarce
few centimetres thick. The thin-bedded limestones
a
(2)
The five facies are: (1) Madstone-shale facies up
The thickness of this facies varies from 0·5 to 7 m.
to 7 m thick. The colour is generally grey-green to
locally
The limestone beds are 0· 01-0·05 m thick and grey
commonly, graded beds. The bioturbation increases
be distinguished: planar beds, nodular beds and less
ramp
This facies
dolomitic partings. Three types of limestone bed can
(3) Thin-bedded limestone facies. The
distal
millimetre-thick
bedded limestones dominate this facies but they are
(4) Thick-bedded wackestone facies. The
almost
In
semblage dominated by millimetre-scale Tubiphytes
scalloped morphology. The macrofauna! assemblage
facies. This facies occurs at the top of the cycles and
The
thickness of this facies varies from 0· 3 to 4 m and the
Packstone-coquina
derms and ostracods. This facies has been interpreted
thin-shelled bivalves ( Daonella) concentrated along
upper
The Rasquera Unit, 23-40 m thick, is located only
Rasquera
1988b). These facies occur in a
lithofacies
The
mite
from
bone
of all
stone
storm
shale;
1986).
Priorat
trends:
erosive
bedded
consists
Tucker,
25
intensity;
carbonate
(Markello
of
with
type;
(1)
beds
thin-bedded
towards the
to
intermediate
wackestone;
(4)
&
(6)
1988b).
(7)
five facies:
top.
thin-interbedded
Domain.
are
marlstone-shale,
and
dolomitized, with
bases and
50 m,
content;
dolosparite;
Read,
Middle Triassic carbonate ramp systems, Spain
preted as storm beds;
increasing
and
(5)
activity compared
limestones,
(3)
graded
massive
(3)
Capafons dolomites, marls,
generally dolomitized; and
1981;
proximal
the
increasing bed
limestones,
millimetre-scale
creasing shallow-water fauna.
Locally the
marlstone-shale,
thick-bedded
with
There is little
1-8 m thick;
0· 01-0· 08 m
oolitic
up
deep
main
grain-size;
madstone-shale,
lime
bedding;
Aigner,
dolomitic
increasing
other
thin-bedded
thick,
cycles. The ideal vertical sequence (Fig.
thickness;
(2)
The thickness of this
ramp
to 8 m
limestone
thick-bedded
marlstone
evidence
facies
lamination,
1984;
ramp
grainstone,
Tivissa limestones-dolomites and shales unit
they are
breccias
with
mudstone
thick.
outer ramp shallowing to inner ramp deposits.
are:
and (5)
(Calvet
The Tivissa Unit is located only in the Baix Ebre­
in­
shales and breccia unit
thin­
cross-bedding including herring­
inter­
interbedded limestones (this facies is poorly devel­
limestones-dolomites; (3) thin-bedded marly dolo­
evaporite mold casts and possible roots; (4) thick­
limestone beds are 0·02-0·1 m thick and the marl­
facies. The Tivissa Unit consists of these facies ar­
lime mud­
thick-bedded wackestones and packstone-coquina.
limestones,
These facies and cycles are interpreted as distal,
marlstone with
models
13) consists
decreasing
ranged into two cycles. The ideal vertical sequence
(1)
(2) marlstone with
stones and wackestones, 0· 2-2m thick, which are
95
of intense
( 4) bioclastic packstone
with
The
increasing
beds show
In general, each cycle shows the following upward
and
&
oped in the second cycle), and thick-bedded facies.
bioturbation
unit varies
it is present in all three sedimentological domains.
ripples,
Wright,
(2) marlstone interbedded with thin-bedded
These facies and their sequences are interpreted as
evaporitic facies and has a variety of lithofacies: (1)
The Capafons Unit grades into the overlying Keuper
mostly
The thickness of this unit varies from 25 to 45 m and