Page 167 - Carbonate Platforms Facies, Sequences, and Evolution

are
ary
The
In
rates
have
highs
scarp
facies
basins
(1969)
to
quences
whereas
beneath
at
detected
and
more
aminifera,
deposition
Colacicchi
deposition.
intervening
Sinemurian
Sinemurian
by
may
the
the
the
&
was
noted
of
addition
explain
horizontal
to this question.
subtle
to
the
(seamounts)
the
that
Pialli
therefore
Calcare
basins
Calcare
Calcare
reduced
surface,
actually
Colacicchi
observing
the
these
deposited
Hettangian-Sinemurian.
&
and
Calcare
sudden
dimensions
the
there
in
prevent
have
differences
overlie
Massiccio.
Massiccio
Pialli
an
Massiccio,
and
the
in
producing sediment at rates of=
Calcare
lasted until the end of the Jurassic.
would
the
differences
of the Calcare Massiccio is a
According
the
Massiccio
formation
started
found
condensed
skeletal fragments of calcareous algae,
which
in
be
spatial
(1969)
thicknesses
of
to
can
Colacicchi
no
intertidal
the
Massiccio
(1969), Colacicchi et al.
to 250 m in height above the adjacent basins.
bachian through early Cretaceous sediments,
&
during
development
benthic
beneath
Jurassic
only
appears
wackestone
of
Hettangian­
Hettangian­
Dimensions and map-view pattern of the seamounts
Pliens­
Massiccio, synsedimentary normal faulting is necess­
20 m (Colacicchi et al., 1970). In general, the litho­
se­
for­
been deposited in water no deeper than 10-
(1970)
Pialli
setting,
complete sequences represents consistently subtidal
there
and lows in the basin floor that
structural
both overlie the shallow-water deposits of the Calcare
(1981), shallow platform carbonates are capable of
Schlager
the
1-10 m 1000 yr- 1 ,
to
which could outpace reasonable fault-displacement
grainstone that includes ooids, peloids, oncoids and
this difference as evidence that the synsedimentary
interpreted
Throughout the northern Appennines basin, these
side of the fault. Synsedimentary faulting during the
and Centamore et al. (1971) recognized that because
be
fault scarp at the surface. Without a substantial fault
a
found
difference between the sedimentary facies on either
obvious
basin, but the scarcity of exposures and well data on
around the
to
the base of the Calcare Massiccio prohibit an answer
the thin seamount facies and the thick basinal facies
the vertical relief of the seamounts was 250-1000 m.
distribution
The stratigraphic evidence cited above indicates that
different sequences representing the seamounts and
normal faulting that produced these seamounts and
the
gastropods, bryozoans and echinoderms.
of
be
that
been
reefs,
ments
The
vening
(which
6. •The
normal
20 km2•
Stewart
these
of offset
Marginal
irregular,
primarily
are
sediments.
seamounts
are
structurally
on
sizes
of
relatively
studied
basins
Some
faults,
of
are
Isolated carbonate seamounts, Italy
range from
in
of
the
are
these
perhaps
the
seamounts
Several
broad
(1985), the
seamounts
the
of
controlled
25° to
whereas
due
detail.
characterized
and
have
essentially
shown
to
faulting Jurassic sediments.
escarpments of the
these
As
by
fiat
in
ant factors in their drowning.
other
particularly
seamounts
faults. In a
seamount
features
clearly
on
Fig.
well
of
vary
6
tops
top
described
number
horsts). These escarpments
seamounts
the
seamounts
are
dissection by
60° and truncate
seamounts
are
because the shallow-water Calcare
sub-parallel
of
exposed
by
marginal escarpments
Hettangian-Sinemurian
(e.g.,
exposed
have
grooves or gullies that range in depth from =
and
of
in
throughout
Bice
appear
1-5
inter­
mentioned above, the northern Appennines are pre­
have been modified by submarine erosion from by­
of trends in thickness and facies changes in the post­
beds of the Calcare Massiccio. The marginal escarp­
(their size and upper surfaces) appear to be import­
the
of the seamounts are more difficult to determine. As
horizontal
cannot be localized carbonate buildups like pinnacle
seamounts are generally limited to the cores of large
anticlines where erosion has removed the overlying
Calcare
sently a complex fold and thrust belt that formed in
the Neogene. As a result, exposures of the Jurassic
map-view pattern of the normal faults and the timing
small (of the order of 2 km2 at Monte Rotondo) and
seamounts
(Figs 4 & 5), the original marginal escarpments that
Studies of these exposures provide an approximate
localities
to
Monte
secondary
Nerone and Monte Cucco). As discussed later, these
these
the
northern Apennines, but few have a surface area>
marginal
Sibillini Mountains (Fig. 4) and in the anticline that
extremely
bounded the seamounts have been located. Several
escarpments, other margins are located on the basis
of the seamounts and an intervening basin that has
erosional
m
composed
&
grooves that can be seen in the photographs of Fig.
Jurassic fault scarps that
passing sediments, producing a series of sub-parallel
runs from Monte Nerone to Monte Cucco (Fig. 5).
also occurs in the grabens· separating the seamounts
slopes
Massiccio
The generalized geological map in Fig. 4 shows two
Massiccio, but as mentioned above, these seamounts
153