Page 309 - Carbonate Platforms Facies, Sequences, and Evolution

286
sea
crust,
lation
The
Hines,
basins.
to
floor
organisms
with
conformities
a
1985).
this,
were
succession
testify
move
spreading.
of
Kent
Nevertheless,
the
imply other mechanisms
from
local
the
Upper
(1976)
Cooper
Synsedimentary
concentrated.
during sedimentation (Fig. 40).
(Keuper)
besides
Triassic
As
(1977)
a
development
taphrogenic
considered
were formed on those salt-induced hjghs.
to
halokinesis
unconformities
unconformities
tectorusm.
result,
J.
reported
in
that
In
ily attributed to tectonic pulses, a feature also recog­
re­
Urgonian of the Basque-Cantabrian Basin is primar­
In conti­
nental Urgonian environments, several angular un­
synsedimentary influence has been detected in de­
carbonate caps with mud mounds, local unconform­
genetic connection between unconformities and eu­
corre­
thermo­
et at., 1981; Reitner, 1982; Antigiiedad et at. , 1983;
the
static sea-level falls. Haq et at. (1987) identified two
supercycles and nine third-order cycles in the Aptian
posits of the Aptian and Albian (Garcfa-Mondejar,
in general, all the Aptian and Albian unconformities
nized in many sequences of similar age from different
(e.g. Brinkman & Logters, 1968). Nevertheless, its
1979; Badillo, 1982; Garcfa-Mondejar, 1982; Vadala
in many parts of the basin. Therefore they could also
the
distinguished, have little evidence of tectonic action
Vail et at. (1984) and Haq et at. (1987) have made a
ities (Fig. 39), radial slopes and other related features
global change in the rheology of the materials of the
created
that
thick
many of the probably eustatic Cretaceous falls in
sea-level were associated with unconformities, and
local relief on the seafloor, over which reef-building
of diapirism
tectonic subsidence and an increase in the rate 9f
Aptian-Albian interval was an important phase of
sponding to the Aptian and the Middle Albian and,
4Km
to
the
Wealden
level
(e.g.
these
cycles
SE
1987).
the
Garcia-Mondejar
eustatic
relative
graphy,
rise,
early
Cantabrian
western
and
o
would
sea-level fall,
Hallam,
curve
changes in the
the
�.J1Km
part
changes
of
there
Aptian
early-late
1984;
of
in
is
area, were
Haq
them can be established.
the
resultant
correspond
cases,
et
good
Aptian
at.
sea-level
basin.
more
and was followed
Kauffman,
certainly
equivalent in the eustatic curve.
in
by
The
(1987)
a
1986;
agreement
the
is
Pondra diapir (Ramales
transition,
in
early
Fig. 39. Urgonian angular
exclusively
Haq
and Garcia-Mondejar (1982).
not be represented in the example described.
has
to
et
Reciprocally,
influenced by
sedimentary sector). The lower
shown
Urgonian unit corresponds to the
sequence u2 (at least in part) and
the upper one is attributed to the
relative sea­
unconformities associated with the
falls and rises could be due to imprecise biostrati­
Bay of Biscay at this time. Nonetheless, the compari­
both regressive and transgressive eustatic episodes.
Basque­
.
Basque-Cantabrian Basin brought about a relative
As each of the proposed tectonic pulses for the
sequence U3. After Badillo (1982),
regressive-transgressive
the Basque-Cantabrian
For
the
in
Fig. 29. The relatively small differences observed in
no
Aptian
general
the timing of the late Aptian and Albian sea-level
sea-level fall of the eustatic curve at 112 Ma would
of global eustatic cycles, provided a correlation with
the
eustatic changes established in the Aptian and Albian
cycles could also be considered to be local reflections
A comparison between curves of relative sea-level
local tectonism, perhaps not yet fully associated to
the major phenomena that were taking place in the
at. ,
Basque-Cantabrian Basin and the
timing has more discrepancy, so that the sea-level
terms between the eustatic curve and the curve for
and Albian, each cycle consisting of a succession of
son made demonstrates that most of the Urgoruan
the
fall reported in the Basque-Cantabrian region close