Page 104 - Carbonate Platforms Facies, Sequences, and Evolution

in
94
reef!
The
(1974)
the
Above
metres
Alcover
dasyclad
localities
offshore,
The
cumulated
southwest.
the
(Hemleben
undulating,
flank
from
has
A
on
&
at this surface.
reef
the
slope sediments,
include
and
the
laminated
locally
been
reef-top
Feels,
beds with clinoforms
of laminated,
grainstones
former
Silurian
margins
complexes
with
1977).
erosive,
dolomites
framework
described
grainstone
are
isopachous fibrous calcite crusts.
of the
by
F.
Unit
BEN IFALLET UNIT
stromatolitic,
similar arrangement
Michigan
aragonite
facies
reef complexes of the Austrian Alps.
facies
of
Diploporia
and
above
Grainstones
onlapped
are
Basin,
a
unconformity,
and metre-scale patch
Mesolella
at
fenestral
reefal
botryoids
by
also
and
Calve!, M.E.
Tucker, 1988a), peloidal cementstone and skeletal­
ac­
dolo­
mites, locally with columnar stromatolites, floe cal­
inter­
reefs.
com­
and at the margins of the buildups they form a thin,
the
and
brecciated and slumped facies. The inter-reef facies
buildups as thin
are a flat-bedded cap to the reef-mound complexes,
Reef-top facies consist of planar and cross-bedded
annulata
cite (now dolomite), intraclast horizons and vadose
LADINIAN REEF MOUNDS
pisoids associated with tepees structures. These rocks
some
several
sharp,
peloidal grainstone. Marine cements are prominent
consists solely of a 0·1 m-thick, bioclastic-peloidal
but locally there are thick slope
preted as a paleokarstic surface (Calvet & Tucker,
plexes in the outer shallow ramp, decreasing in size
into distal ramp facies (Rasquera Unit) towards the
et al.
Brandner & Resch (198 i ) in the Ladinian-Carnian
by
La Riba Unit probably passt:s laterally into
1988a). Some ferruginization and silicification occur
wackestone-packstone, equivalent to up to 60 m of
the Querol stromatolites unit towards the north and
is
at
This
isms
ment
1977;
Feels
thick,
The
1987).
The
Prades
scribed
locally.
mitized
of
unit
outcrop
thin-bedded
(1977)
The
lower
principally
consists
to
Domain,
and insects
Via et al.,
ferruginous level.
and
According
Tucker and J.M. Henton
of
part
extensive
1966, 1975; Beltan,
but grey
to
of
located
1977;
filling
shear-wrinkles,
in
massive
the
Esteban
with rare density currents.
thin-bedded
oolitic-bioclastic
the
shallow
at several
Via,
et
on fresh
the
Esteban
thin-bedded
Alcover laminated dolomites unit
al.
grooves,
water
consists of thin-bedded,
levels
1987;
Alcover
et al.
eastern
inter-reef
dolomites
tool
surfaces.
(Via
over
the La Riba Reef Unit.
Unit,
(1977b)
&
part
the
dolowackestones,
dolomicrites.
marks
of
contain
(1977b),
have
de­
and stromatolites. These facies represent the develop­
quisitely preserved fish, reptiles, soft-bodied organ­
ex­
dolo­
finely-laminated
depressions.
15-20 m
This unit directly overlies the Benifallet Unit in the
Fig. 16. Sedimentological model for
The
separated by millimetre-thick dolomitic marlstones.
the
of bedded facies in the upper part. The Alcover Unit
chevron structures. Silicified evaporite nodules occur
and
and intraformational folds and slides. Hemleben &
Villalta,
region
packstone-grainstone
1972, 1975; Hemleben & Feels,
contains millimetre-thick laminae, convoluted beds
La Riba Reef Unit. The upper boundary below the
dolomicrites in the lower part, passing into a variety
inter-reef areas, and onlaps and then overlaps the
Capafons Unit is represented by a centimetre-thick
This facies
The colour of the dolomicrite facies is ochre-yellow
dolomicrite beds are 0· 04-0·1 m thick and they are
upper part of the Alcover Unit consists of
Via & Calzada,
this
facies was deposited in quiet and anoxic conditions