Page 47 - Carbonate Platforms Facies, Sequences, and Evolution

a
42
NE
the
ping
ward
sequence
shelf
boundary
asymmetric
vertical
is
of
dipping
-
sub-sequence.
sub-sequences.
margin
Pin Dale (Fig. 4)
the
lateral distance
The
marked
of
stacking
clinoforms have
mounded
a
=
shoal
of
by
clinoforms.
lower
shelf
form
opment of multiple paleokarsts
The
500 m.
in
-
downlap
A
sequence
successive
interior
(Fig.
base
is
and
5).
of
R.L.
shoal
lower sub-sequence boundary. The basin
sub-sequence
the
the
cross-section
concave-up geometry
has
marked
clinoforms
....,..
sequence boundaries are associated with the devel­
some 10m thick contains both shelfward and basin­
The higher sub-sequence is characterized by well­
ward dip­
in­
and
shelfward direction. They are interpreted as the lee
Onlap occurs on to the shelfward (stoss) side of the
dicates mainly vertical accretion of the shoal, with
shoal
developed clinoforms dipping basinwards at 25-30°.
almost no progadation during the deposition of the
(15-30°) in a bas inward direction and (10-15°) in a
shelfward and basinward direction. Clinoforms dip
and stoss side of a bedform respectively. Internally,
shelf break into the shelf-margin shoal complex over
erosional truncation and onlap. The upper and lower
by
downlap at the base of the shoal sequence in both
Pin Dale is oriented approximately perpendicular to
upper
the shelf margin and shows the transition from the
with
The shoal sequence can be divided into two main
sequence
an
top
of
Logged
Covered
Sequence
the
Gawthorpe and P.
face
Sub-sequence
scribed
marked
Section
shelf
Section
two main
sequences
by
clinoforms;
Boundary
(Fig.
Gutteridge
in detail
5)
Boundary
shoal
margin,
as
a
the shoal complex and
paleokarstic
this
sub-sequences.
=
10m
sequence
are characterized
evolution of the sand bodies.
distance
2
The
most
sequence boundary (paleokarst A) can be mapped into Hope Cement Works Quarry (see Fig. 6).
by
of
surfaces.
northeast from the bedform crest.
on to the stoss side of the bedform.
(Fig.
=
Hope Cement Works Quarry (Fig. 6)
Paleokarst
clearly
The
6)
No
20m
A
will
100m
@ ------
three
to
displays
be
Fig. 4. Line drawing of part of the quarry at Pin Dale (SK159822) illustrating the main bedding plane configurations,
and onlap onto the shelfward side of the lower strata. Sub-sequence 3 onlaps the stoss side of the bedform. The upper
sequence boundaries and sub-sequence boundaries. Note the mound-like form of sub-sequence 1 and downlap onto the
de­
600 m in length perpen­
is masked by the development of a paleokarstic sur­
(Figs 6 & 7a) is characterized by sigmoidal, convex­
second sub-sequence is interpreted as a change from
face at the top of the shoal. The development of this
lower sub-sequence boundary. The beds underlying
sw
vertical accretion to basinward progradation of the
however, the exact geometry of the top of the foresets
pass basinward into bottomsets which extend over
lower sequence boundary. Sub-sequence 2 is characterized by well-developed clinoforms dipping towards the shelf margin
the
observed. The foresets attain at least 10m in height;
downlap is
basinward-dipping
shoal
here (Fig. 6), with several of the sequence boundaries
lower sub-sequence
As at Pin Dale, the shoal sequence is divisible into
the
This quarry provides a section = 100m thick through
foresets downlap at a high angle (up to 30°) on to the
bedform. A third minor sub-sequence displays onlap
can be recognized within the exposed shoal complex
dicular to the shelf margin. Three shoal sequences
up clinoforms. No bottomsets are developed and the