Page 287 - Carbonate Platforms Facies, Sequences, and Evolution

268
slope
within
which,
consist
usually
bidites;
thonous
suggests
ganisms.
siliceous
calcareous
terrigenous
aprons
marls.
or
The
by Magniez &
mainly
contain
units
Terrigenous talus
according
of
All
were
deposition
izes other intervals.
of
to
shallow-water
the
absence
siliceous
grey
conglomerates.
these
talus
below
of
and
All
ferruginous
from the La Gandara mound
the
slope
Urgonian
bathymetric
black
preferential
units
(Fig.
sandstones,
sediments
local
nodules
but
sites
lack
light-dependent
include
estimates
and
photic
deposition.
J.
for
mudstones
some
reef-building
suggests connection with adjacent oceanic areas.
transport deposits, such as slumps, debrites or tur­
autoch­
reason for the lack of benthic fossils that character­
mass­
the basinal sediments indicate a reducing environ­
or­
thin-
marl
ment on the seafloor. This may also have been the
fossils
geochemical studies of these facies have been done
zone,
Rat (1972) and Pascal (1984). The
sandstones or grainstones were intercalated at times
12) as well as
others, may have been in at least 100m water depth.
Detailed palaeontological and
The characteristic dark or black colours of most of
both bioturbated or interlaminated with sands; they
and locally ammonites. Mudstones- and marls- are
all of them contain abundant plant debris
They
The upper part of the Urgonian Complex includes
made
and
presence of ammonites and other open-marine fossils
are
accumulation (Figs 3 & 20). Mudstones and turbiditic
are
12),
beds,
deep.
deltaic
deltas.
Garcia-Mondejar
currents,
(Fig. 18).
fan-deltas
and
there
The
locally
Sandstones
are
(Fig.
within
origin
distributaries
included
Conglomerates fill
appear
18;
has
bedded, sandy turbidites.
channels
DEPOSITIONAL
within
within
amalgamated
the
the
beds
Agirrezabala
connected
of
Fig. 17. Ortho and para­
been proposed
&
channels excavated
They are lenticular bodies lOOs to a few
limestone clasts and some
of the sandstones in this
SEQUENCES
mudstone
megabreccias with Urgonian
in
terrigenous
(Fig.
upslope
with black mudstones, from the
calcareous turbidites alternating
to either highly concentrated turbidity currents
case
distal slope apron adjacent to the
at the bottom of the cliff for scale.
The Urgonian of the western part of the Basque­
Garcfa­
Monctejar, in press). The formation of the terrigen­
mud­
of carbonates on Urgonian highs, so that some iso­
Northern Platform sector. Geologist
parts of the region (Soba Basin for instance, Fig.
thought to be intermittent deposition from turbidity
an origin of distal mouth bars of large
to
Cantabrian region has been shown to have a cyclic
organization and are attributed to a
Baquio area. They show no vertical
or
stones and other talus deposits. They are attributed
ous talus units was contemporaneous with deposition
metres wide and up to a few lOs of metres thick.
is
units.
fine-grained
turbidites, filling channels 100m wide and up to 15 m
lated limestone clasts or breccias from these highs
units
Agirrezabala & Garcfa-Mondejar, in press). In other
debris flows, developed in talus slopes close to feeder
18;
Sharp bases and turbidite features are rare in these
1000s of