Page 290 - Carbonate Platforms Facies, Sequences, and Evolution

the
AGES
The
same
faces,
of u2.
limestone
third
can
Its
regression.
DEPOSE-
OUENCES
u3 sequence
break
by
sw
be
in
Vert1cal lh1ckness not to scale
sequence,
Another
Garcfa-Mondejar (1979).
dolomite
four Urgonian depositional
mobile zone. Modified from
attributed,
U3,
referred to in the text (1- 10).
upper boundary
at
and active flanks of a tectonically
of the Ebro sedimentary sector in
the area of Santa Gadea, showing
is
sedimentation.
region, in association with
that area (Garcfa-Mondejar &
several unconformities (A-D), the
Fig. 22. NW-SE geological section
sequences (U1-U4), and the passive
is shown
regressive
in
least
An
D Sandstones
in
local
NE,W
Pujalte,
some
Fig.
N300E
period,
of early-middle
partially,
27,
example
Unconformities
places
tensive dolomitization in the northwestern part
C] Mudstones
erosional sur­
1983). Ex­
Gorbea, a sharp contact between Urgonian carbon­
used to differentiate the sub-sequences U2 1 and U2 2 .
irregular replacement of great masses of Urgonian
like
characterized by an erosional surface, appears in the
age, is limited at its base by the unconformity on top
ates below and regressive sandstones above. In the
of
of an
to the
taken
locally
from Matienzo. The whole U2 sequence records the
history of at least one transgression followed by one
sedimentary sector of Ramales (Figs 23 & 24) and is
Albian
or correlative
U3,
areas
C: Post-tectonic unconformity
stone
0: Post-tectonic unconformity
region,
appears
(Fig. 24,
0 Limestones
At the
Urgonian
when
fig. 2.23).
it
that
separating
conformities
megabreccias
ary of U3 (Fig.
B: Syn-tectonic (passive flank) unconformity
locally
E,SE
In the
fluvial
Aptian-Albian carbonate episode, Spain
as
0 Marls
appears
A: Post-tectonic halokinetic angular unconformities
18).
a
megabreccias
8
previously
limestones
as
from
a
had
and
beginning of the
subtle
Mudstones
fluvial
been
sharp
angular
6: Turonian limestones
u1-u4: Urgonian sequences
formation
regressive
NW
northeast part of the
contact
sediments
(Garcia-Monctejar,
emergent,
sedimentation was re-established
Fig. 23. Schematic and composite cross-section of the Basque-Cantabrian Urgonian Complex, showing the general
in
region,
5: Supra-Urgonian sandstones rutrillas·)
N120E
mudstones of the U4, laterally associated with lime­
(Garcfa­
coarse-
organization in platforms and basins, the depositional sequences distinguished (U 1-U4) and the main sedimentary sectors
environment, is attributed to the same upper bound­
between
unconformity
sandstones
Mondejar, 1979). In the western central part of the
top of Picon del Fraile Limestones Formation). The
271
Portillo de las Escalerucas Formation on
and siliceous conglomerates of talus
erosional contact in the area of Ea between limestone
boundary in this platform area can be followed into
an
the sequence U3 are replaced by prodelta sands and
the adjacent basin, where autochthonous marls of
1985a,
southwestern part of the region, the upper boundary
the
of sequence .