Page 25 - Carbonate Platforms Facies, Sequences, and Evolution

(
a
&
in
of
22
9).
the
2 &
free
was
The
with
In
mixed
9).
neritic
quence
lagoon.
(Tocchi
the
the
humid
Massiccio
later
sediments.
Elsewhere
Formation
Anhydrite).
cavernoso),
Tuscany
Limestone).
a
Rare
In
or
as
carbonates
Palaeozoic
deposits
evaporites
The
climate
Internal
and
the
drowned
Boccheggiano
deposition
overlies
Limestone
deposits (Verrucano),
and
Formation),
with
MESOZOIC
and
of
the
poorly
Tuscan
basement
Tocchi Formation (Carnian)
transition
Cavernoso
OF
thin
External
(Massiccio
the
or
Boccheggiano
(Ammonitico
to
is marked
followed
covered
carbonate platform
Anhydrite
on
Tocchi
carbonates
Domain
-shale
the
Upper Triassic-Middle Liassic
along an arid shoreline (Costantini et
Tuscan
preserved
by
Rosso
This formation consists of alternating
Ferriera
by the
Limestone
Limestone)
carbonate-siliciclastic-evaporitic
T.
TUSCANY
Middle
Anhydrite,
Lower
and
Boccheggiano Anhydrite (Carnian to Norian)
developed
(Apuane
Formation
(Anidriti
Domain
and
carbonate
a!., 1980).
Dolomite), locally directly on the basement. It inter­
se­
Glomospira cf. kuthani, Diplotremina sp. and Glom­
siliciclastic­
12) starting during the Carnian with lagoonal,
(Boccheggiano
Formation.
Triassic
underlies the Rhaetavicula contorta beds (Figs 2 &
this
which lie unconformably on
(= 2000 m thick) is underlain by continental
Formation) which persisted through Lower Liassic
Alps
Liassic
(Rhaetavicula contorta beds) in a wide metahaline
intercalations
deposition
deposits
fingers to the west with a calcareous marly sequence
laid down in a deepening-upward basin (La Spezia
sequence records a major marine transgression (Figs
and Massa Zone), a carbonate platform developed
during the Norian under an arid climate (Grezzoni
passing upward to evaporite solution breccias (Figs 2
foraminifera
ospirella spp.) suggest a Carnian age (Costantini et
Cherty
sericitic and
chloritic shales and thin dolomites (up to 40 m thick)
(Calcare
and
di
a!., 1980). They formed in restricted lagoons located
A thick evaporitic sequence (up to 1000 m), known
Burano
this
by open-marine
to the Triassic anhydrite-carbonate unit that in the
under
Boccheggiano) is an informal name commonly given
et
Cocozza and A.
the
tion
refer
La
search
Burano
Burano
overlies
to
suggests
indicate
comm.).
different
are
Grezzoni
anhydrite
anhydrite
Limestone
(Martini et
subsurface
on
Formation
Gandin
Triadodiscus
an
the
Norian
a!., 1989).
environment
Spezia
the
is
age
of
Umbrian unit.
assemblages to
and
a
arid
(Costantini et a!.,
different
Grezzoni Dolomite
changes
Formation
Formation
Monte
Dolomite
range
a!., 1989).
early
respectively
(Ciarapica
S.
evapor i tic
and
Palaeozoic
foraminiferal
Formation
1 9 80).
dolomitic
&
corresponding
induced
low-energy
(Martini
Boccheggiano
(Norian
In Tuscany the
Croce
microfauna!
to
consists
dolomite.
et
by
are better preserved (Costantini et
interfingers
Burano
sequence
a
to
breccia
superposed
Passeri,
assemblages
a!.,
as
Formation when found sheared off at
The
Boccheggiano
Boccheggiano
with
Grezzoni Dolomite (Carnian to Rhaetian)
with
of two
(southern
over
of
eomesozoicus-Glomospirella
Alpine
Member
the
provinces
sabkha
La
1980).
Formation
1989).
Rhaetian)
both
and
and
Dolomite and La Spezia Formation (Figs 2 & 9).
calcite cements. It resulted from anhydrite-gypsum­
Norian with Glomospirella rosetta­
locally enclosed in the Ligurian nappes. Recent re­
The carbonate facies are stromatolites and mud­
Jurassic Massiccio Limestone and Ferriera Forma­
Gandinella apenninica assemblages (Zaninetti, pers.
Anhydrite,
It grades upward to the Massiccio Limestone. West­
authors commonly
is an
Formation
Tuscany)
directly on the Palaeozoic basement (Apuane Alps).
abundant
Boccheggiano Anhydrite ranges from Carnian with
stresses, and subsequent dissolution of the sulphates
tectonic
This unit consists of alternating layers of
Cavernoso
wackestone with faecal pellets and skeletal grains,
stone with anhydrite rosettes and nodules (Fig. 6c,d),
capellinii
subsurface the sulphates and the stratigraphic order
the
a!., 1983; Martini
Burano
the base or
for
The
during exposure and weathering. It mostly represents
the evaporitic sequence in outcrop whereas in the
a
and fine-grained intraclast or oolitic grainstone. They
Early
Spezia
the
members:
Gr e zzoni
system
intertidal-supratidal
This is a dolomite unit up to 300 m thick that overlies
ward of the Apuane Alps, in the La Spezia region,
the Tocchi Formation (Montagnola Senese) or lies