Page 180 - Carbonate Platforms Facies, Sequences, and Evolution

in
the
166
less
open
The
warm,
faults,
the
related
organic
disabled
sediment
so
evolution
facilitated
to
saline
history
high
ocean,
rate
of
accumulation.
reefs,
the
the
of
(1) the system
In summary,
they
than
of
to the drowning.
removal
this
these
are
the
salinity
which
The basinal water was
removal
the system of
and
preventing
basin.
of
sediment
water
the
normally
seamounts
The
structurally
that
pre-existing
carbonate
decreased
is
form
sediment,
normal faults in that
from
water
seamounts (Heckel, 1974; James, 1983).
the
drowning
accumulation
they
development
typical
small sizes of these seamounts, the
controlled.
of
elevated
sediment
production
on
reducing
of
above
of
important effects: it contributed to the ease of sedi­
were no effective reef-building communities in resi­
dence. Perhaps to some extent, the absence of effec­
pro­
probably much colder and
the
appear to have been connected to the open ocean.
interiors of healthy carbonate platforms. The deep,
rapidly formed basins that surrounded the seamounts
healthy Calcare Massiccio seamount, and the mixing
sudden
These
the rates of carbonate production, thus contributing
of this basinal water with the water of the seamount
tops may have been an important factor in lowering
the
rate of sediment accumulation. The lack of fringing
rims
the important causal factors appear to be those that
and
The small sizes of these seamounts
around the margins of seamounts, probably had two
of the seamount tops to the water and waves of the
the
the
ment removal since elevated rims commonly act as
efficient sediment traps, and it exposed the interiors
lack of elevated rims around the seamounts is also
isolated
of such organisms at the time of formation of the
tive reef-builders is related to a world-wide scarcity
fragments of a former platform interior where there
history of the Italian Peninsula. To some extent, the
subsidence that eventually drowned these seamounts
incursion of cold, less saline water and the crustal
the sediment budget and the eventual drowning are:
structures are in turn related to the plate tectonic
duction. The underlying causes of these changes in
are all closely related to the system of extensional
the northern Apennines represents a critical stage in
the
these
seamounts is mainly the result of a dramatic decrease
northern
opening of the Liguride Ocean; and (2) the general
seamount tops, which is the net result of increased
Jurassic, when these seamounts were created. The
scarcity of reef-building organisms during the Lower
of extensional faults related to the
the drowning of the seamounts of
and
BtcE,
close
up,
and
Am.
BoND,
plate
R.H.,
forms:
Alpine
BATHURST,
tectonic
and
benefitted
565-568.
BERNOULLI,
Abs.
D.M.
155-173.
Jr.
mentation
Montanari,
G.C.
ALVAREZ, W.
D.M. Bice and K. G. Stewart
Buou-DuvAL,
retrograding
&
Ancient
miogeocline,
of
&
&
tectonic
D.
Mediterraneens
system.
B.,
crustal
the
Examples
Lung
greatly
&
collaboration
subsidence
In:
Prog. , vol.
model
(Eds
Shaver,
STEWART,
southern
carbonate
from
KOMINZ,
of
from
Chan
Alpine
with
thinning.
Geosynclinal
L.) Editions Technip, Paris,
curves
the
the
K.G.
R.H.)
Elsevier, Amsterdam, p. 658.
JENKYNS,
Histoire
M.A.
and
dispersal. Nature 248, 309-314.
for
platform
authors are especially indebted
Geol.
Canadian
Walter
Geol. Soc. Am. Bull. 87, 891-896.
orogenic
Bijou-Duval,
18, no. 6, pp.
Spec.
(1985)
REFERENCES
thorough
H.C.
the
(1984)
Mark
Soc.
Paleont. Mineral. no. 19, pp. 129- 160.
evolution
B.
belt
port; Carolee Bice for field assistance.
Implications for subsidence mechanisms,
Apennines.
Structurale
pp. 143-164.
of
Sedimentation
Rocky
Pub! .
&
margins.
ACKNOWLEDGEMENTS
by
early
Am.
Ancient
(1974)
540-541 .
Alvarez,
reviews
the
Des
Soc.
(Eds
over the development of a sedimentary basin.
Anders.
Geol.
by
Bull.
Geology
Construction
From the Tethys ocean to the Mediterranean seas:
diagenesis. Developments in Sedimentology 12, 2nd edn.
Grants awarded to Kevin Stewart and David Bice.
ALVAREZ, W., CocozzA, T. & WEZEL, F.C. (1974) Frag­
Chapter and the Comune di Piobbico for field sup­
Alpine,
(1976) A former continuation of the Alps.
grooves on exhumed bypass margins of carbonate plat­
Soc.
Pialli, J.F. Read, M. Santantonio and J.L. Wilson.
age of break­
Apennines demonstrates the powerful controls that
Econ.
for his enthusiasm and encouragement. This paper
plate tectonics and the history of organisms can have
Mountaiqs:
erosional
DERCOURT, J. & LE PtCHON, X. (1977)
to Walter Alvarez
Mediterranean, and central Atlantic Mesozoic facies in
Dott,
relation to the early evolution of the Tethys. In: Modern
BtcE, D.M. (1986) Computer simulation of prograding and
of
Sandra
A
western
The
The authors
acknowledge support from NSF grants EAR80-22846
Many of the ideas in this paper are the products of
microplate
R.G.C. (1975) Carbonate sediments and their
G.
Montadert,
EAR83-18660, grants from Chevron Overseas
Petroleum, Inc., and Geol. Soc. America Research
We thank the Club Alpino Italiano, San Severino
95,
13,
Bassins
Paleozoic