Page 199 - Carbonate Platforms Facies, Sequences, and Evolution

a)
b)
bedded
buildup,
NW
Barreiro #3
and
block
?major
fault to
boundary
bioclastic
tilted fault
reveals a
=
NW
very
limestone lithoclasts (core 2).
wackestones,
different
possibly
BARREIRO #2
sequence
part, the clasts are set in a matrix of light and inter­
those encountered in the other wells. Here the lime­
to
composed largely of limestone breccias. In the lower
Barreiro #3 is located to the southwest of the main
stones are much thinner (just over 160m thick) and
deposited
which are overlain by argillaceous wackestones with
in Barreiro #4
slope
location of cores •
21)
under
pyritic
and
Upper Jurassic carbonate buildups,
so
the
relatively
ammonitic
Portugal
shelf
interior
Barreiro #1, #2 and #4 and the distribution of facies associations described in Table 1.
lime
SE
sequence
0 0
100�
derived from a nearby buildup.
with
with
shallow-water
could
1km approx.
seismic anomaly (not shown in Fig.
mudstones,
metres
be
dolomite
�
bioclastic
a
Montijo# 1
(offset from NE)
breccia beds become more argillaceous up
CD-®
SE
talus
conditions.
I
petroleum exploration as follows: (1) dolomitized porous zone within buildup; (2) dead oil shows in porosity within
other stratigraphic units, and the location of cores in Barreiro #4. The circled numbers refer to features relevant to
reef framework
suggesting
the
1000
oncolitic wackestones
®
limestone breccias; (3) tar sands within the Upper Jurassic and Lower Cretaceous that accumulated in a trap formed by
deep -water li mestones
se­
Fig. 13. Interpretative cross-sections of the Barreiro buildup. (a) Sketch section showing the relationship of the buildup to
some reef knolls ®
compactional drape over the buildup. (b) Interpretative cross-sections across the buildup showing position of cores within
slope
The
increase in depth of deposition. As no major faults
are revealed on seismic sections, a fault scarp talus
quence, and are interbedded with argillaceous and
an
origin for the Barreiro #3 sequence seems unlikely.
11, but see Fig.
However, the well is located very close to another
185
grai nstones(V
@