Page 95 - Carbonate Platforms Facies, Sequences, and Evolution

3
4
in
86
the
are
eral
rent
plain
Fig. 6.
Unit.
small
cycles
0·1-0·
the
bivalve
at
the lagoon.
lagoonal
ripples.
lagoons
each
developed
mud
and
located in the
shallowing-upward
transgressive
Dasyclad-capped
They
intermediate
when
locality.
also
lakes
and
banks
stones are present at the
units.
fragments, corals,
the
part,
commonly oolitic and have
sand belt of a shallow ramp.
of
The
top.
upon
as
the
composed of wackestone-packstone.
contain
In general they consist of
sedimentary
F.
The
Dasyclad
lateral
intraclasts
mud-shoal
lower
a coastal
mud-shoal sequences became subaerial.
described
and
part
package
bioturbated
echinoderm
shallowing-upward
for
bioturbated lime mudstone (b), and the upper part is
to
persistence
packstones
Calvet, M.E.
Detail of shallowing-upward sequence in Vilella
shallowing-upward sequences, but in addition grain­
each sequence is at least a kilometre. The shallowing­
cross-bedding and cur­
Overall, the Vilella Baixa Unit represents a gen­
lime
Mud-shoal sequences. These sequences (Fig. 5)
varies from 2 to 25 m, and there are five to seven
mudstone in the lower part, wackestone-packstone
upward sequences were deposited in a shallow-ramp
peloids.
grainstones are
from
Baixa Unit, Lower Muschelkalk. The lower part is made of
carbonate
the
3m thick beds are located at the top of some
sequences.
These mud-shoal sequences are 4-8 m thick, and
of
setting, probably in the outer more seaward part of
shallowing-upward sequences of the middle part and
upper part of the Vilella Baixa
in
and
there are up to three cycles developed. The oolitic
and
the
Thjs restricted facies is interpreted as the deposit of
grainstone is interpreted as a shoal deposit of the
the
and
The
to a
part.
local
local
beige
white
Baixa
finally
mites'
The
The
formity
towards
morphs
(1977a).
between
to
Tucker and J.M.
Colldejou
dolomites'
interpreted
locally
the
Unit
grey
sabkha-type
the
occur
the
vary
after
The
breccias
a
as
Dolomitization
Colldejou
laminated
in
Unit,
dolomites
a
following
consequence
(Fig.
Henton
dolomicrites
and
is
(Calvet
below
as
Lower
Unit
of
crust,
in
7).
dolomites
dolowackestones
&
is
gypsum;
southwest)
desiccated stromatolites.
the
the
caliche
In
paleokarst,
features
thickness
environment:
(2)
and
disconformity
and
the
Colldejou white dolomites unit
below
of
pervasive
lack
intraclasts;
described
crust
(1)
dolomicrites-dolomicrosparites
0·1 -0·4 m
Ramon,
20-40 m
0·1-0·5 m
of
Muschelkalk
some
the
the
from 5
and
by
and
marks
supratidal
to
Prades
consists
above.
with
thick
thick
disconformity
scarce
(5)
truck
1987)
the
suggest that it was deposited in an inter-
of
there
a
stromatolites;
with bivalves, dasyclads, peloids and ooids.
and
regional
with
80 m.
Esteban
is
mud-shoal sequences of the
carbonate
'Grey
Colldejou
beds.
form
a
fauna;
Domain
and
bioturbation;
et
In
white
The main facies of the unit are: (1) white-beige­
preservation of small-scale sedimentary structures.
dolo­
The Lower Muschelkalk contains two principal dolo­
to-supra­
cracks, and lensoids and rosettes of calcite pseudo­
discon­
(increasing
The
to
boundary
and collapse breccias. The laminated crust has been
and the Middle Muschelkalk clastics and evaporites.
facies
stromatolites
tepees
upper boundary is a regional disconformity related
parallel
pseudomorphs after gypsum; (3) parallel-lamination,
fine
millimetre-scale lamination, small wave-ripples, mud
suggest depositions in an intertidal-supratidal and
dolopackstones,
Unit
upper
(3)
(2)
( 4)
to bedding on an outcrop and regional scale (Fig. 7).
the
at.
mite types. Above the regional disconformity, 'white
planar and
extend
down to a dolomitization front which is discordant
the
upper and locally the intermediate part of the Vilella
the
tidal and sabkha-type setting. Dolomitization of the
Gaia-Montseny Domain grey dolomites replace the
The sedimentological features of the Colldejou Unit