Page 94 - Carbonate Platforms Facies, Sequences, and Evolution

of
as
The
The
with
(Fig.
mites,
posed
stone.
order:
the
Middle
5)
deduced
no
Gaetani,
of
(Schmidt,
theirgartii
grey
supratidal
laminated
madstone
and
lower part
The
Olesa
(1)
wackestone
towards the
stromatolites.
to
and
from
1932;
consists
Anisian
top,
cycles
Unit,
with
grey,
upper
Voltziaceaesporites
passing
the
1977). The
intraclasts.
carbonate-evaporite
on
marlstone,
limestones
evaporite mold casts;
sedimentary
are
shallowing-upward
up
Virgili,
This unit, 6- 14 m thick,
terrestrial
sparse
of three
Intraclasts,
the
and
4-12m
unit
into
These
may be covered
Praecirculina
boundary
cycles
where there
and (3)
subtidal to supratidal deposits.
Olesa bioclastic limestones unit
Colldejou
is
mud
occurrence
bioturbated
1958).
by
of
0·1-0.5 m
basis
of
thick,
structures.
a
heteromorpha
fauna;
are
El Broil laminated carbonates unit
deposits
interpreted
cycles
of
The
Unit
thin
of
in
lithofacies,
the
lime
dolomites.
(2)
as
are
The
cracks
thick,
granifer in
sharp
with
muddy,
consists
the
is
undulating and
and
Vilella
the
hypersaline waters and a strong clastic input.
grey
of
There
brachiopod Mentzelia mentzeli (Calzada
is
lutite­
dolomite­
mudstone­
rippled oolites occur towards the top of the dolo­
basically consists of well­
part of the Middle Muschelkalk (Soh! et al., 1987).
bioclastic limestones, from lime mudstone to grain­
change from these bioclastic limestones to the bio-
probably cor­
intertidal­
shallow­
wave­
local breccias, com­
cycles. The ochre-brown dolomites (0·2-2 m thick)
thick, consists of two or three dolomite-marlstone
stromatolites.
rapid transition up from the Buntsandstein into this
massive
The upper part of the El Brull Unit varies from 3
uppermost
Unit is also Middle Anisian, dated by the presence
Paraceratites
Buntsandstein (Rot equivalent). The Olesa Unit is
Baixa
&
lower
a
Stellapollenites
responds to the lower part of the Upper Anisian, as
intraclasts, ripples and some millimetre-size lensoid
lithofacies
unit and its upper boundary is marked by an erosion
interpreted
have flat, smooth millimetre-scale lamination in the
grey
domal
mudstone-wackestone with planar millimetre-scale
relatively
also mudcracks,
lamination to centrimetre-scale domal stromatolites
to 13 m, and contains two to three cycles. Each cycle
in ascending
lime
surface. The lower part of the El Brull Unit, 1-6m
1
2
(2)
the
are
lime
lime
beds,
With
massive
bivalves,
the
two main
Mentzelia
sequence,
packstone,
specimens.
with
Vilella
movement.
grainstones.
bioturbated
base
massive,
in
a
mudstone,
The
mudstones,
The
Baixa
absence
upward sequences;
mentzeli
Middle Triassic carbonate ramp systems, Spain
passing
Shallowing-upward
with
Olesa facies
marine
echinoderms,
upper
upper
Unit.
skeletal
are:
occurs
part
packstones-wackestones
up into
fauna
The
( 4) dasyclad-capped sequences.
as
is
peloids,
parallel-laminated
pseudonodular lime
sequences.
in
of emergence
subordinate
boundary
(1) lime
lower
is
(small
Unit mostly consists of six lithofacies:
parallel,
whole
wackestones
a
Vilella Baixa bioturbated limestones unit
turbated limestones of the Vilella Baixa
These
facies are interpreted as lagoonal deposits.
part
composed
and
0·2-0.3 m
indicators,
1-10m thick, consists of grey to
mudstones,
of
foraminifera
of
Unit.
sharp
wackestone
(3) mud-shoal sequences;
mudstones
wackestones with scarce fauna (bivalves and ostra­
millimetre­
pack­
of sequence: (1) muddy sequences; (2) shallowing­
structure. They are interpreted as mud banks, per­
inter­
stones, oolitic-skeletal grainstones and packstones,
This unit is 20-90 m thick (increasing towards the
and
The
cods). The beds are 0·4-1 m thick, with a generally
these
85
ostracods) and locally oncoids (10-20 mm in size).
thick
gastropods,
to
and
and dasyclad packstones. These occur in four types
wackestones, bioturbated lime mudstones, massive
thin-bedded
scale laminated and rare wave-rippled carbonates;
and
haps similar to those of the inner Florida Shelf (e.g.
Bosence et al., 1985). The mud banks were located
preted as shallow-subtidal deposits. The brachiopod
(Figs 5 & 6) are located in the intermediate part of
important regional disconformity. The Vilella Baixa
1-3m thick lenticular bodies. They
(centimetre-scale)
part of the Vilella Baixa Unit and consist of massive
and
reach 200 m across and have no discernible internal
sequences
Muddy sequences. These are located in the lower
southeast) and varies from lime mudstones to oolitic
each
grey
in a very shallow, inner lagoon with restricted water
unabraded
The thickness of each shallowing-upward sequence
fragments, echinoderm debris, ostracods, dasyclads,
part is very shallow-subtidal to intertidal in origin.
foraminifera, peloids and quartz grains. The upper
wackestone-packstone beds, 0·5-1·0 m thick, which
beige
and wave-rippled. This upper part contains bivalve