COMPARATIVE STRATIGRAPHY OF THE LOWER PART OF THE
CARBONIFEROUS-PERMIAN BIRD SPRING FORMATION,
SPRING MOUNTAINS, CLARK COUNTY, NEVADA
by
Janine
B. S.,
Massachusetts
EARTH,
Commerford
Institute
(1983)
of
Technology
SUBMITTED TO THE DEPARTMENT OF
ATMOSPHERIC, AND PLANETARY SCIENCES
IN PARTIAL FULFILLMENT OF THE
REQUIREMENTS FOR THE
DEGREE. OF
MASTER OF SCIENCE
at
MASSACHUSETTS
the
INSTITUTE
May
0
Massachusetts
Signature
of
Department
of
1984
Institute of
Author.........
Earth,
OF TECHNOLOGY
Atmos
v
h iic
.-
Technology
.
and
9--....,....
glanetary
29
Certified
Accepted
1984
Sciences
May 1984
by....... ...................................
John B. Southard
ST"y'eis $upervisor
by..........
Theodore
Chairman, Department
WM4IDRAWN
JUN FRm
MTLIt RARIES
R. Madden
Committee
Table
of
Contents
Page
Abstract............................................2
Acknowledgements.. ..
Introduction....
.
.
.
.
.
.
.
.
.
.
.
.
.
...... 3
...................................... 4
Location.................... ......................
....................... 8
Previous Work........................................7
Pa leogeo logic
Me thods
of
Se tting...............................12
Study..............................................16
Lithofacies..........................................17
Depositional
Synthesis
Environment. ..
.
.
.
.
.
..
.
.
.
.
.
.
30
and Discussion.............................32
Conclusions........
................................. .39
Bibliography..............
.
.
.
.
.
.
.
.
.
.
.
40
Appendix...............................................42
...
LOWER PART OF THE
COMPARATIVE STRATIGRAPHY OF THE
CARBONIFEROUS-PERMIAN BIRD SPRING FORMATION,
SPRING MOUNTAINS, CLARK COUNTY, NEVADA
by
Janine
Commerford
Submitted to the Department of
Earth, Atmospheric, and Planetary Sciences
in partial
fulfillment
of the requirements
for the degree of
Master of Science in Geology
ABSTRACT
Two stratigraphic sections of the lower 200 m of the
Carboniferous-Permian Bird Spring Formation were examined in the
Spring Mountains, Clark County, Nevada.
The Bird Spring Formation
was deposited in the late Paleozoic Bird Spring Basin.
Despite
subsequent large-scale east-directed thrust faulting of Bird
Spring basin, the two sections lie
in the same thrust
sheet and
have retained their
original
separation of 40 km.
Thin-section studies reveal five lithofacies
common to both
areas.
The five facies are characteristic of a shallow-marine
environment which was subjected to periodic sea-level
fluctuations.
Facies 1 is a carbonate-cemented siltstone,
Facies
2 is a lithified carbonate mud, Facies 3 is a matrix-supported
biomicrite, Facies 4 is a grain-supported biomicrite, and Facies 5
is
a biosparite.
Facies 1 and 2 were deposited in a quiet, anoxic
environment, below wave base. Facies 3 was deposited near wavebase
in an oxygenated environment, Facies 4 was deposited above wave
base in an agitated, well oxygenated environment, and Facies 5 was
deposited above wave base in a well agitated, well oxygenated
environment.
Facies 1 or 2 through 5 represent an ideal
regressive sequence.
Comparisons of stratigraphic columns, thin sections, gross
lithologic
features, and lithofacies
succession reveals that the
two sections are very similar.
Sea-level fluctuations and consequent changes in depositional
environments appear to have been felt equally at both locations.
Since age constraints
provided by fossil
dating are not exact,
such close similarity of two sections of Bird Spring located 40 km
apart could mean several things.
A very gently dipping basin
floor might cause an area 40 km farther
from shore to experience
the same environments as one closer to shore, or the two areas may
have been located roughly parallel
to the paleo-shoreline at
approximately the same depth. Given the poor age constraints,
the
sections may not be contemporaneous.
Similarities in facies types
and sequences may be due to facies shifts caused by sea-level
fluctuations and not by contemporaneous deposition in uniform seas.
Thesis
supervisor:
Department
Dr.
J.B.
Committee:
Southard
Dr.
T.R.
Madden
Acknowledgements
I
the
would
idea
for
enthusiastic
I
for
like
to
this
study,
thank
Prof.
J.B.
as well as
Southard
for his
am
indebted
to many
Wilcock, Roger Kuhnle,
Klepacki.
Thanks go
at
moments,
crucial
Bernward
of
the
denizens
to
finish
this
and
me
excellent and
sense
thesis
(by
get a job).
and Danny Orange
to
to
administrative
Finally,
go
to my
Peter
and Dave
the
comics
officemate
thoughtful comments.
own
the impetus
thesis)
time
with
friends.
(and
to
for
floor
I wish I had
them.
the Department
the 9th
red
Sheffels,
lending me
giving me
been wonderful
to
staff
for
who
financial
guided
me
aid
through
the
tape.
I would
long-suffering
hardships he
due
10th floor
Jim Danna, Matt Kohn, Larry McKenna,
spend more
Thanks are
and
have
thanks
finishing his
the
Doug Walker,
of humor and
for
of
Barb
Stein for
special
thank John Lambie
helping me
able
Donna Blackman,
to Judith
Hay for his
I want
granted,
giving
teaching.
providing encouragement and advice:
been
for
like
to
express my gratitude
field assistant for
endured on my
account.
the
to my
long hours and great
INTRODUCTION
This
study
environment of
examines
two
Spring Formation
located
their
in
the
sections
thrust
relative
of
the
of
revealing
comparison of
the
sheet
relative
depositional
Carboniferous-Permian Bird
Nevada.
and
separation
Knowledge
the
stratigraphy and depositional
in Clark County,
same
original
the
have
lower Bird
of
of
the
Spring
the
late
sections are
apparently
(Burchfiel
positions
environment
The
retained
et al.,
1963).
sections
permits
stratigraphy
Paleozoic
Bird
a
and of
Spring
basin.
Both sections
lowermost part of
one
in Lee
separated
Canyon,
by
the
delimited
and
the
by
the
The
the
overlying
measured
descriptions
other near
thrust
Pahrump,
done
steel
each bed
thrust
during
tape
the
and
to
were recorded
collected. Five
lithofacies
environments
of
deposition were
descriptions
and
km apart,
spine
they
the
Brunton
and
the
lie 40
thrust
summer
form
sections,
which
Canyon
and
The
trending
in
Lee
Pass
m thick
Formation.
sheet
underlying
Wheeler
with
of
Spring
180
northwest-southeast
Field work was
were
approximately
the Bird
Spring Mountains.
is
are
of
of
are
to
north
1983.
compass.
the
located
the
(Fig.
south
3).
Sections
Detailed
samples were
representing different
thin-section
distinguished using
analysis.
the
field
Vegas
Location of Section 1
3
Fig. 1
Lee Canyon Section
4
5 Kilometers
Jeep
trail
Location of Section 2
0
1
2
3
Kilometers
Fig. 2
Pahrump Section
4
5
Fig. 3
Spring Mountains
LOCATION
The
range
Spring Mountains
lying west
mainly of
is Mt.
are
upthrusted
the
with cactus,
Outcrop
generally
forests
may
Section
in Lee
Canyon
junction of
lat.
(Fig
US 95
36*26'10"
Quadrangle.
on
It
is
the NE
The base
of
and
remain pleasantly
sparsely
grasses,
and commonly
C at
height
the
east side
and Nevada
N in
tallest peak
the
of
covered
the
higher
summmer.
reaches
slopes.
the
1).
composed
The higher regions
regions are
superb, except in
the
The
trending
of
located
52,
at
quarter
Section
the
8 km
long.
of
the
1 lies
Spring
east
of
Mountains,
the
115*34'00"
W and
Charleston
Peak
at about
15'
1200 m above
level.
The
Bird
thickness
faults,
Spring
of more
but
gently and
is
km
east
Formation
than 2100 m.
truncated
by
in
this
It is
erosion
area
has
broken by
at
the
a measured
only minor
top.
Beds
dip
uniformly NW 30*.
Section 2 lies
11
Lower
of 45*
cover
1 lies
height.
pinon pine,
mesquite, and dry
temperatures
They are
carbonates.
in
and
summer.
experience
is
Nevada.
Paleozoic
Charleston, at 3574 m
even in
where
a northwest-southeast
of Las Vegas,
forested with spruce
cool
sea
are
of
the
on
town
highway
16,
section
is
at
quarter
of
the Pahrump
off an
long.
the west
side
of Pahrump.
unnamed jeep
115*51'30"
15'
of
It
trail
W,
lat.
Quadrangle.
is
the
Spring Mountains,
located
7.2
shown in Fig.
36*13'00" N
km NE of
2.
in
The
the NE
9
The
lower
part of
the
Bird
Spring
Formation
relatively
intact, but upper parts
faults
folds.
due
and
to
erosion.
The
top
of
the
in
this
area
is
are contorted by many
formation
is
again missing
PREVIOUS
The
by
Bird
Hewett
deposits
(1931)
of
the
assigned the
basis
The
of
located
sandstone.
Fossils
corals,
abundant.
The
form slopes.
This
slopes
from a
Longwell
in
is
including
the
thickens
of
Formation.
rugose
are
found
mainly
corals,
locally
components varies
shales
and
and
dolostones
siltstones
Spring
the
section.
and
and
makes
the
consists
pattern
Bird
of
easily
distance.
(1936)
noted
conspicuously
to
they
of
placed
the
the
They extended
the
lower
Bird
base
the
Permian,
that
the
80 km northwest of Las Vegas.
into
the
shale,
limestones
Springs,
Pennsylvanian
of
common and
terrigenous
ledges
ore
Hewett
Spring Range,
crinoids
resistant
and
characteristic weathering
m section
the Mississippian.
part
fusulinids,
a
study,
Nevada.
named
the Pennsylvanian on
fairly
and
and
geology
calcareous
measured
fusulinid
the
lower
Bird
The purer
less
and Dunbar
1575
described
of
to
the
the
Chert
to bed.
while
identifiable
from
brachiopods,
ledges,
Formation
survey
dolostone,
percentage
from bed
alternating
of a
collected
limestone,
as nodules.
colonial
part
first
Goodsprings Quadrangle,
section,
calcareous
Formation was
Bird Spring Formation
of 750 m of
form
as
fossils
type
greatly
Spring
WORK
the Bird Spring
northwest.
Spring
On
of
near
the
lie
Indian
the basis of
Bird
upper part
to
They
a
Spring
through
below
the
in
the
Supai
Spring
in
Mississippian,
in the
Pennsylvanian, and
the middle
the uppermost
Langenheim et al.
Spring
Formation
of Las
Vegas,
the
upper
Bird
in
Spring
(1972),
rocks
Las
the
this
basinal
area
750 m
the
is
the
Range,
m
80
Bird
km northeast
Spring Mountains.
through
30
the Permian.
1050 m of
truncated
extends
lowermost
A
the
in
1350 m in
Canyon
east of
section
including Ledbetter
done work
from cratonal
Formations
the
of
authors,
have
Vegas.
the Arrow
Bird
by
Although
erosion,
the
Permian
Early
age.
Wolfcampian
Other
in
place
to
the
Lee Canyon, Nevada.
measured
(1962)
and miles
part
led him
study
fusulinid
detailed
near
Spring Mountains,
the
m section of
measured a 2100
(1959)
Rich
and
on
the Bird
platform
(1970)
Spring and
sequences
and
correlative
found
The Pennsylvanian-Permian Callville
are
invariably
Bird Spring
much
thinner and more
sequence
to
the north.
Smith
southeast
of
and Pakoon
clastic
than
PALEOGEOLOGIC
The
Spring Mountains are
Paleozoic marine
deposited
In
the
on
Paleozoic
margin existed
in
geosyncline.
Near
shed
in
westward
center
of
Davis,
1972).
of
the
the
Late
an
Davis,
1972).
the
the
basin,
end
to
in
the
rocks
far
enough
The
which
any
of
of
the
sediment
in
to
The
while
plate
sequence of
sediments were
farther
west
formed
in
the
(Burchfiel
and
time
of
the
sequence
Basin was
the
appearance
craton
margin
(Burchfiel
portion of
the
Spring
the
and
Cordilleran
transformed
area
Antler
from
Mountains were
now
known
orogenic
the
belt
western
into a
into
as
the
formed near
Great
tectonic
thickness of
have
received
source
(Fig
4).
behavior,
type
depocenters
of
accumulated sediment
smaller basin,
Basin,
to
consisted of numerous
area was not a uniform belt,
differentiated
elements.
clastic
the west
Great
A
craton.
north-trending
Mississippian
the
duration,
sedimentation, and
1959).
in a broad
limestones
eastern Great Basin
varied
American
shelf.
composing
east
limestones, were
(Stewart, 1972).
belt
pile of
North-Atlantic- type
geosyncline,
purer
a thick
mostly
craton margin,
Eastern
southeast margin
if
passive
of
the North
the passive-margin
the
little
of
The miogeosynclinal
unstable
The
a
Devonian-Early
marked
mildly
rocks,
deposited
Antler orogenic
geosyncline
These
this area
sediments was
In
composed
the western margin
early
marine
rocks.
SETTING
but rather
platform, and
(Steele,
was
positive
Fig.4
Late Daleozoic Paleogeologic Map
(after Bissell, 1962)
These
uplift
and
as
the
area
1962).
(Bissell,
was
Formation
the
forces
Pioche
Basin,
The
more
Bird
Spring
than 2100 m of
It covered
(Steele,
has
roughly
1959).
been
southern
Basin
of
carbonate
sea,
transgressive-regressive
sea
line,
known as
sediments
level
platform-affinity rocks
Bird
Spring
and
platform
were
its
the
south
north
deposited
on
correlative basin deposits,
much
generally
and
contain
stable.
Vegas, and
1962).
facies
the
rocks are
Carboniferous and Permian
are
dividing
the
from
in basinal
Formations,
in
runs
(Bissell,
Pakoon
deposits
accumulated
resulting
sequences,
the
formed
sea.
thickest part.
fluctuated,
platform
the
time
through Las
to
Basin,
shallow marine waters
correlative
platform during
These
in
Their
environments.
Callville
rocks
to
Spring
Inyo-Panamint
Vegas hingeline,
rocks
basin-affinity
Basin
Bird Spring
the
remained relatively
northeast-southwest approximately
separates
the
Paleozoic
sedimentary
the Las
Great
time
Spring Basin."
late
line between platform and basin
This
and
km 2 with warm
200,000
Although
subsidence
of
the Bird
called
the name "Bird
author prefers
This
depocenter in which
The
the
the
the west affected
to
deposited
rates
Paleozoic and early Mesozoic
throughout late
tectonic
varying
experienced
depocenters
Callville
the
(Smith,
thinner
1972).
than
much more clastic
material.
The
Mountains
the
type section of
the Bird
(as defined by Hewett,
Las Vegas
hingeline;
these
Spring in
1931)
rocks
lies
have
the
to
Bird
the
a more
Spring
south of
platformal
character
than
Mountains.
the
The
Bird
Bird
Spring
clastic
components,
primary
dolomite, all
nearer
shore
the
Great Basin.
type
in
area
indicate
Bird
Spring
the
Spring
contains
more
more
a higher energy,
the
seas
Formation
and
yellow
silts
sands
the
deposition
of
in
the
Supai
belt
in
in
the
sedimentation
the
the
the
eastern
basins with silt,
of waters
of
the
redbeds.
the
of
Bird
the
red
Continued
uplift
Permian
eastern Great
from
deep-water
deposition
late
of
from normal marine
restricted
The withdrawal
resulted
orogenic
from most
separated
and became
ended
Spring
and
time a sustained period of
areas were
deposits.
Basin
the Antler
Permian
of
circulation
and gypsum
paleozoic
seen
cross-stratification, and
retreat
Several
mud,
of
the
of which
to Medial
caused
open-water
more
in
rocks
environment.
In Early
uplift
Spring
finally
Basin
and
ended
(Steele,
1959).
The
the end
rocks
of
affecting
eventually
southwest
with
later
of
Spring
the Paleozoic
the
Mountains
Era.
The
western margin of
caused east-directed
(Burchfiel
episodes
Basin and Range
part.
the
and
Davis,
complex
the
1972).
of which
all
deposited
tectonic
North American
thrusting
of extension,
Province,
were
led
the
to
forces
continent
throughout
This
the
by
the
thrusting,
formation
coupled
of
the
Spring Mountains are
a
Two
stratigraphic
Bird Spring
section
County, Nevada,
The
sections
the
lie
METHODS OF
STUDY
columns
the
lowermost
one
near
were
of
studied,
other near
Pahrump,
approximately
40
section was
described, detailing
grain
color,
and
size,
amount of
type
of
were
selectively
thickness,
visible
sedimentary
the
five
Standard
thin
types
of
of
extent
of
Five
of gross
Each
present
Clark
Nevada.
bed
in
each
characteristics,
characteristics,
type and amount of
lithofacies
sections were
(if
in
prepared
for
any).
type
chert, and
Both sections
grains,
cement,
preservation
grains,
presence
each
different
section.
Each
of major
types of
types and
sedimentary
amount
from each
each sample.
of grains,
texture,
and
of
several
relative amounts
character and amount of
non-bioclastic
types
bedding
samples were collected,
section was examined
bioclastic
of
main
thin
components,
km apart.
the
photographed.
Representative
of
structure
Canyon,
Clark County,
weathering
fossils,
Lee
180 m of
amounts
structure,
of micrite
matrix,
and
bioturbation.
major
lithologic
lithologic
units were
description and
stratigraphic columns were
drawn between
lithofacies
(see
thin-section
on
descriptions
fig.
17,18,19).
the
basis
study.
compared and correlations
them using field
succession
delineated
The
were
and patterns
of
LITHOFACIES
Permian
rocks
of
Pennsylvanian and
Indian Spring
and
finely
purple-weathering
locally abundant
limestone with
is
calcite, and of
cemented with
orange-weathering, green-weathering,
coarse-grained
and
in age,
reddish fine-grained
of dense
sandstones
laminated
hereafter
Formation,
Spring Formation.
the Bird
consist mainly
rocks
the
in character from
markedly different
the Morrowan Bird
Chesterian
is
Member,
Spring
Indian
the
called
Spring
Bird
the
m of
30
bottom
The
in
Spring Mountains.
Bird
the
in
examined
Spring rocks
identified
were
lithofacies
Five
fossil
remains.
environment and are
1 and
Sections
because
types
2,
they
they
are
before
deposited
proper.
Although
below.
Formation
disconformable
the
A discussion
the Depositional
of
formation
Indian
Environment
the
Cristo
Monte
rocks appear
in both
lithofacies
included as major
not basinal
of
with
Indian Spring
are not
nonbasinal
transitional,
in a
rocks were deposited
These
in character and were
the
Bird
Spring
Spring rocks
is
included in
thesis.
of
this
rocks
is
primary
matrix
is
a very
section
Basin
Matrix
Matrix
calcite
or
in
the Bird
dolomite.
carbonate mud
Spring
Primary
(micrite) which
often appears
or
secondary
fine-grained
to be
stained
reddish
or brownish.
In
constituent, whereas
between
larger
precipitation
grains,
or
by
crystalline
of
it
fills
or
dolomite
recrystallization of
or
calcite
micrite
sparite,
or
is
into
the
only
interstices
formed
voids
preexisting
forms
dolomite
is
the
Secondary cement
calcite
cement,
subhedral
facies
in others
grains.
of
some
by
between
the
micrite.
This
an interlocking mosaic
crystals.
Grains
Some examples
entirely
of micrite.
contained
at
are
especially
amoing
fossil
common
the
stronger
fusulinids.
contain at
quartz-rich
facies
siltstone, with
thin
for
grain
are
the
seen
both
major
silt-size quartz
grains
one)
angularity
than detrital
A few examples
each were
Ooliths
constituted
were
The
fragments.
scattered
examples of
contained no
of
the quartz
sparsely
each
quartz
grains
facies
at all.
suggest an
origin.
seen
were seen
a large
grains.
a micrite-cemented
throughout, but a few
size and
lithoclasts.
such as
fragments
forming
fossil
facies,
fossils,
some quartz
basically
quartz
the quartz-rich
eolian rather
and never
is
least
abundant angular
sections
and uniformly
(except
Crushed
of
examined
Uncrushed
matrix-supported
types
composed
grainstones.
Most facies
In most
fragments.
in
are
thin sections
through micrite matrix and
constituents of
The
quieter-water facies
However, most
fairly
brachiopods and
scattered
the
least some
fragments
most
of
in
of ooliths,
the
pellets,
and
higher-energy facies
proportion of
the grains.
Fecal
pellets
facies,
were
were
looking
observed
subangular
partially
occasionally
like
uniform
in only one
clasts are
redeposited,
atypically
lumps
case.
composed
consolidated
seen
the
These
had
quieter-water
of micrite.
large
of micrite,
micrite
possibly during
in
been
(2 cm by
formed
torn
a storm or
Lithoclasts
1 cm)
when
up and
then
other period
of
strong water movement.
FACIES
Facies
angular
to
1 is
a siltstone or
subangular
cryptocrystalline
generally
often
poorly
partly
have
pink,
or no
or
of
The
few
the
fossils,
Biogenic
presence
producing
10
of
composed
quartz
grains
(micrite).
weathering.
hidden;
beds
are
cemented
Beds
This
often
or
thick,
locally
They
abundant,
elongated
fine grain
size,
facies
carbonate production was
abundant
silt,
which
to
contain
rocks
contain
is
often
little
seen
to
in
gray
bedding.
lack of
below wave
probably
tends
is
weathered
parallel
and
by
are
fine-grained
green casts.
Chert,
cm
These
indicate a quiet environment,
organisms.
of abundant
where -float may or may not
tan,
debris.
nodules,
to
beds beneath.
orange,
cross-lamination
base.
resistant
slopes,
the
fossil
black
calcareous mud
or wholly
scree-covered
examples
silt-size
shale,
to
retarded by
stunt
ca-rbonate-
Fig.
5
Facies 1:
Siltstone.
Lee Canyon.
with well sorted subangular quartz
Crossed nicols.
Fig.
6
Facies 1:
Siltstone.
Pahrump.
Micrite
with well sorted sub-angular quartz grains.
Crossed nicols.
Micrite
grains.
Fig.
7
Facies 2: Micrite.
Lee Canyon.
Rare quartz
grains.
Note large uncrushed shell fragment.
Crossed nicols.
Fig.
8
Pahrump.
Facies 2: Micrite.
grains, no fossil fragments.
Crossed nicols.
Few quartz
Fig.
9
Facies 3: Matrix-supported biomocrite.
Lee
Canyon.
Reworked fossil fragments (crinoids,
echinoids).
Crossed nicols.
Fig.
10
Facies 3: Matrix-supported biomicrite.
Pahrump.
Few quartz fragments, reworked fossil fragments.
Crossed nicols.
I
Facies
2 is
a micrite,
cryptocrystalline
relatively
rare,
rugose
or
carbonate mud.
though
colonial
small
in
some
amounts,
locally
odor.
expense
micrite
In
of
the
field
medium-gray
do
nodules
and
than
but occupy
these
rocks
fine-grained
very
are
ledges.
unbroken
present
in small
fragments
slide
to
are
pieces
crystals
little
area
Chert
Pyrite
often
grow
unbedded,
present
area.
bedding.
broken
dolomite
large
nearly
are
parallel
are
otherwise
5% of
freshly
fragments
contain
by
pellets
less
Euhedral
sulphurous
beds
Angular quartz
covering
present,
almost entirely of
Fossil
blanketed
Fecal
beds.
abundant in
occasionally
some
corals
fossil-free micrite.
amounts
composed
at
in
in
is
is
emit
a
the
the
slide.
light-gray
to
Cross-lamination is
not
present.
The
of
few
micrite
fossils,
lack
indicate
and
3 is
fine-grained
both whole
Angular
and
the
area
pellets
In
the
medium-grained
be visible
and
fossil
It
fragments
Dolomite
are present
these
form impressive
is
fossil
matrix-supported, and
make
make
up
up
rhombs
fragments
present.
less
than
between 10%
growing
common as
in
at
5% of
and
the
Facies
30%
of
expense
2.
in small amounts.
rocks
and medium-gray
on weathered
presence
anoxic
fragments are
present but not as
field
quiet,
composed of
Fossil fragments
are
a
carbonate mud.
on a slide.
of micrite
Fecal
a biomicrite,
quartz
constituents.
in
and
base.
uncrushed
silt-size
cross-lamination,
deposition
environment, below wave
Facies
of
are
in
surfaces.
cliffs.
fine-grained
color.
Beds
are
to
Fossil
fragments
may
generally massive
Fig.
11
Facies 4: Grain-supported biomicrite.
Canyon. Reworked fossils.
Crossed nicols.
Fig.
12
Facies 4: Grain-supported biomicrite.
Pahrump.
Reworked fossils (crinoids and fusulinids).
Crossed nicols.
Lee
Fig.
13
Facies 5: Biosparite.
Crossed nicols.
Lee
Canyon.
I
Fig.
14
Facies 5: Biosparite.
Crossed nicols.
Pahrump.
MA
Gray
and black chert 'pods and nodules
Cross-lamination is
The
presence
environment,
Facies
both
whole
Fossils
in
and
zone,
fossils
with a
fragments are
medium-gray
on weathered
3
to
5
cm
in a moderately active
close
scant
thick
and up
to
to wave
base.
composed of
micrite
trilobites,
medium-grained
limestone with
surfaces.
often
matrix.
and
rare.
is massive,
Chert
Large-scale cross-lamination is
beds
abundant.
fragments,
probably
crinoids, brachiopods,
Field appearence
visible
fossil
a grain-supported biomicrite,
Quartz
coarse-grained
abundant
photic
crushed
include
gastropods.
fairly
indicates deposition
the
4 is
locally
absent.
of
somewhat reworked,
are
is
present
several
to
fossils
present
in some
meters
easily
locally.
beds,
in
with
lateral
extent.
The well-washed and
reworked
fossils
cross-lamination indicate deposition
oxygenated environment, above wave
Facies 5 is a biosparite,
and
an
was
sparry
cement.
Both whole
equigranular mosaic of
probably
micrite
formed
matrix.
Field
The
to
sparkle
secondary
obliterated
the
presence
of
energetic, well
base.
of
crushed
crystalline
is
grains
are
fossil
fragments
fossils
calcite.
the
absent
a very massive
coarse-grained
in
the
are
bound
Sparry
by
cement
recrystallization of a preexisting
Quartz
appearence
medium-grained
surfaces
by
in an
composed
and
and
in
this
unbedded
limestone
whose
facies.
medium-gray,
fresh
sun.
recrystallization
of
this
facies
original grain/matrix composition.
has
However,
1 /-
/
,--- --i
Facies
1
Siltstone
or shale: angular silt-size
quartz grains in micrite.
Fossils rare.
Chert locally abundant.
Below wave base.
Facies
2
.Micrite: cryptocrystalline
Fossils rare. Little
or no
Below wave base.
Facies
carbonate
quartz.
3
Matrix supported-biomicrite: fossils
somewhat reworked.
Near wave base.
Facies
1:1
4(y
Z
4(
mud.
are
4
Grain-supported biomicrite: fossils
are
reworked.
Ooliths and cross-lamination
sometimes present.
Above wave base.
MR
Facies
5
Biosparite: recrystallized fossil
Above wave base.
and micrite.
Fig.
15
Lithofacies
fragments
the presence
of
fossils
indicates
oxygenated environment.
deposition
Reworked
fossils
in
a well
suggest
an agitated
environment, above wave base.
The
five
sedimentary
lithofacies
cycle
fluctuation.
the
An
described above
deposited
ideal
in
response
regressive
quieter-water, deeper-water
through
increasingly
conditions
(Facies
(Facies
4
contain
the
and 5).
Although
3)
to
ideal
Bird
through
level
is
often not
did not
1."
but
in
the
ideal
transgress
of
or
the
been preserved.
This
regressive
sequences, where
the
conditions
following
previously
finer-grained
sediment.
on depositional
from
the beds
facies
from
2)
sequence
would
order.
"Facies
are
as
is
1
of
facies
through Facies
common;
far as
it
when
had
especially
shallower,
more
the
Another
that not all elements
is
sea
in
deposited.
5
true
of each
for
agitated
tended
deposited unconsolidated
that are
in an area.
environment,
bed analysis.
1 and
quieter, deeper-water conditions
to obliterate
of
progress
environments
sequence
cycle were
cycle have
succession
the
recede
incomplete cycles
of
(Facies
opposite
cycles
reason for
Analysis
facies
transgressive
Incomplete
past, not all members
sequence would
most agitated
cycles,
Facies
sea-level
Spring Basin experienced many
transgressive-regressive
deposited
the
elements
the
to
elements of a
shallower water and more agitated
The
same
are
preserved
Since
will
facies
are
water depth can also
reveal
the
dependent
be
inferred
DEPOSITIONAL ENVIRONMENT
Before
the
the
Bird
Spring
end of Chesterian
parts
of
the
same
area.
Spring Formation was
Spring
time,
Indian
deposited
constituents.
reached
a smaller,
The
Member contains a
clastic
Basin
at
Spring
this
time.
deposited
occurred
Spring Member,
the end
sandstone and
of
the
marine
transgression,
of
Paleozoic,
the
Spring Member
Spring
ended
marine
of
The
the
Bird
Indian
terrigenous
Minor
beds
of
of
sea-level
the
Indian
fine-grained
coarse-grained biosparite.
was
to
Period,
last
a
large-scale
to
essentially
the
deposition
of
the
shallow-water
and began deposition
of
the
deeper-water Bird
the
Bird Spring basin
Pennsylvanian Period, water
m;
covered
in a shallow,
deposition
Mississippian
which
sea
end
Indian
Formation.
Although
100
the
producing alternating
cross-laminated
At
during
extent at
Member
large proportion of
It was
full
shallower
energetic, above-wave-base environment.
fluctuations
its
Bird
Spring
deepened
depth probably
lithofacies
are
in
the
never
exceeded
characteristic
of
shallow
deposited
broad,
seas.
The
Bird
relatively
Spring
Formation was
shallow, warm marine basin.
provided nearly ideal
conditions
carbonate
warm
water, and
sediments:
for
the
temperatures,
slightly agitated
conditions.
The
in
Bird
a
Spring Basin
deposition of
light,
silt-free
Wavebase5
1 and 2
Increasing Energy
Fig. 16
Horizontal Interpretation of Facies Type
These
thousands
basin.
late
favorable
of
meters
Although
for
to
They
bed.
debris,
The
five
slightly
in
lithofacies
in
sea
caused
environment
in
in
are
any
the
entirely
uniform
percent
of
and many
above
were
that are
the
from bed
clastic
other
deposited
produced
factors.
in
the
by
the
deposition
in
the
of
cyclic
basin
location changed as
examined
in
this
environments varied with
time
terrigenous
the
well.
great
while
and
basins.
the
some
sedimentary
between
study;
restricted
Indian Spring Member,
cross-stratification.
induced by
fluctuated,
area
few
seas,
climatologicical variation, or
depth
given
of
fluctuated
Formation contains
were not
means
not have
the
throughout
type and amount of biogenic
structures
characteristic of
exception of
no
of
subsiding
continued
could
the
depositional
slowly
size,
regression
rate,
As water
facies
grains,
deposition
level.
subsidence
level
the
the
by
grain
described
sequences.
extremes
are
differing environments
factor,
Sea
rocks
sedimentary
Transgression and
other
in
deposition
color,
shape of
of
fluctuations
variable
carbonate
Spring
vary
type
allowed
environmental conditions
Bird
constituents,
of
carbonate
Paleozoic,
static,
conditions
sea
level,
With
the
Bird
Spring
clastics and
little
all
SYNTHESIS
The
of
cyclic
this
facies
record
study
is
thick column
of
useful
but
is necessarily
that
occur
sections
time.
and Tertiary
complicated
is
were
cut
same
the
not uplifted
in
original
The
faults
as
a
the
the
basin.
the
and
extent of
thrust
areas
Those
basin has
in
of each
the
proved
same
of
tieir
separation.
Spring
Mountains
well
as numerous
are
cut by
minor
faults
several major
and
folds,
that
by
other may
nothing
retain
been
faults,
now covered
are
original
thus
km 2
stratigraphic
Spring Basin has
low-angle
within a few kilometers
200,000
resulting deformation
The Bird
the
in
Unfortunately,
sections measured
sheets
column
variations
lateral
into mountain ranges
thrust
The
basin.
by normal faults.
stratigraphic
different
in
east-directed
difficult;
on
the horizontal
tectonism and
Reconstruction of
level;
stratigraphic
of a great many
problem.
sea
time-dependent.
covered approximately
alluvium.
mountain range
in
a record
environments occurred when,
to discover
places
in many
preserves
changes
vertical
time
Study
environments
greatly shortened by
and
one
of
Basin
to
vertical and
in
the
is necessary
depositional
Mesozoic
at
rocks
response
little
Spring
Bird
in Carboniferous
have
beds
the worker
The
in
DISCUSSION
Spring
in determining which
tells
facies
of Bird
changes
succeeding
AND
thrust
but
lie
Sections
1 and
et
Deformation within
al.)
2 lie
in
the
same
the
thrust
Lee
Canyon Thrust to
the north
the
south
be minimal.
position
1 and
2
appears
of
this
seem
separation
of
overall
about
of
found
both
is
identical.
Chert is
Indian
and
cross-laminated
the
made
but
Springs
30
sandstone,
the
Sections
Indian
many
similarities.
The
the
is
same
percentage
appear
the
five
of
to be
each
nearly
in both sections.
of
m thick,
and
reveals
the
Member,
Bird
very
more
Spring
is
present
it
is
reddish
in
both
composed
of
the
fine-grained
coarse-grained
or purple-tinted biosparite.
Spring Member
a bed-by-bed comparison with
impossible,
to
relative
rocks:
faunas
types--dense
the
the
original
in both sections
lowermost part
orange-tinted, green-tinted
preservation of
by
Thrust
constrained,
columns
Approximately
lithologic
the
2 reveals
areas.
stratigraphic
Formation,
two
delimited
original
similar
abundant
The
same
in
similar,
similarities.
locations.
their
the beds
of
lithofacies
the
(Burchfiel
the Wheeler Pass
Although
1 and
composed
the
sheet
is poorly
retained
Sections
are
of
and
sheet
40 km.
lithofacies
Study
sheet
character of
They are
same.
thrust
to have
Comparison
The
to
thrust
overall
the
character
in
Lee
of
the
Pahrump
Poor
area
Canyon area
this
member
is
the
same.
The 60 m of Bird
Member
Many of
alternate between
the
ledges
recrystallized
fossils
to
see.
Spring
tend
ledges
in both
calcite
to weather
directly above
and
the
Indian Spring
debris-covered
sections contain
slopes.
uncrushed
or silica-replaced brachiopods.
out of
the
bed,
which
makes
them
These
easy
60
60
30
30
4
a)
1
2
3
4
5
0
Pahrump
Fig-. 17
1
2
3
4
Lee Canyon
Lithofacies Succession
Lithofacies types are represented by horizontal
scale. Vertical scale represents distance above
top of Indian Spring Member.
5
120
120
1
90
90
60
60
1
2
3
4
5
1
Pahrump
Fig. 18
2
345
Lee Canyon
Lithofacies Succession
150
150
a)
a)
a)
4-i
4-J)
0)
120
120
1
2
3
4
1
5
Pahrump
Fig.
2
3
4
Lee Canyon
19
Lithofacies Succession
5
Chert
nodules and
Between
resistant
90
to
layers
and
weathering and
are very
thickness and
lying
In
fossils
the
common in both
125 m from
chert nodules
megascopic
are
the
from 0.3
ranging
to
present
interval between
in Section
some
125
first
the
bottom.
165
10
to
part of
180
m,
in both
15
cm
are
of
in
few
the
beds
section.
in
the
Bird
and
sections.
and both
beds
Layers
Very
slope-formers
common
the
Some beds
sections contain
corals.
The
found
is
and
1 contain brachiopods,
rugose
from
Chert
from
this
of
cliffs.
1 m apart.
in
Spring again alternate between
ledge-formers.
most
form massive
common,
are
base,
sections.
fusulinids
m from
In
in Section
Section
2,
the bottom.
the
1 were
first
found
120 m
fusulinids
Both were
were
identified
as
Millerella marblensis.
Study
of
lithofacies
another basis
covered
for comparison.
intervals
unless
Poor
preservation of
made
comparative
impossible;
Facies
the
to
and
be
150 m,
similar.
covered
of
of
the
Indian
provides
extrapolated
interval exceeds
lithofacies
in
have
across
3 m.
in Section
2
Spring Member
starts
the
initially
12 m.
high
interval from
although bed-to-bed
little
Curves are
17,18,19)
Indian Spring Member
analysis
sections
lowermost
(figs.
at
the
top
of
the
Member.
changes
similar,
the
the
comparison
Indian Spring
Both
succession
In
similarity
lithofacies
the
energies
0 to
60
correlations
interval 60
between
the
successions
two
to
of
m are
can be
115
m
sections.
again appear
deposition.
roughly
drawn only
in
there ap'pears
Between
to be
very
115
Although
the
two
Bird
few
Spring
character and
them
is
the
sections
beds,
appearence.
they do not
silt-size
quartz
uniformly
and
Eolian
enough and
the
and
the
same
fan
such
carry
not
form
to
distributed
that
The
they were
and
deposited
inner basin.
but winds
large amounts
indeeed
50%
layers.
the
such
levels.
angular
suspension,
create
siltstone
than
are
suggests
transport was
strong
of
silt for at
localized
the mechanism
locations 40 km apart would
likely
for
receive
time.
carried in
deposit
as
to
of
are
They
possible,
overall
Both
stratigraphic
quiet waters of
is
beds.
number
do not
in
in
between
difference between
fragments
carried
probably
If eolian
Detrital silt
deposits
particles
enough
would
deposition,
submarine
these
drawn
similar
of more
sorted.
bed and
reached
steady
deposits.
The
transportation
160 km
silt at
of
same
composed
the
currents
they
are
be
1 siltstone
equivalent
extremely well
sorting
up by
at
the
very
real
Facies
fragments.
throughout
only when
silt
the
can
are
The only
lie
1 siltstones
subangular and
least
of
they
contain approximately
but
picked
correlations
sections,
placement
Facies
size
bed-to-bed
those
would
seen
suspension
tend
in
to
form
Sections
from
a river
relatively
1 and
2.
or
localized
CONCLUSIONS
its
Despite
great
than
probably never more
the
basin
about
160
The
to
km
the
gentle
responsive
to
be due
floor
might
experience
the
two
to
an
cause
same
the
not
A small
that
rule
drop
been
as
one
located
the
the age
out
the
depth.
same
were
silts
to
the
sea-level
km apart
to
shore,
or
the
to
the
These
deposited
provided
that
by
fossil
similar
the
caused by
detrital
level
parallel
roughly
constraints
possibility
to
closer
facies
of
water
in
shore
from
sections
but
in
lay
gently dipping basin
deposited non-contemporaneously
Differences
of
basin very
located 40
farther
40 km
the
the
sections were
shifts
it probably
affected
and
A very
things.
area
distance
large area.
approximately
at
contemporaneously,
do
of a
environment
assume
explanations
floor made
regression
may have
sections
the
of
1970).
(Ledbetter,
basin
was
shallow dip
The
estimate
Spring sections
several
paleo-shoreline
dating
large
Bird
Similarity of
could
the
environment
depositional
deep.
paleo-shoreline, but
level changes.
sea
Basin
Spring
to
difficult
the
dip of
Bird
meters
southeast
a relatively
caused
the
100
it
2 from
1 and
Sections
makes
floor
size,
in
large-scale
fluctuation.
due
to
silt
deposition
are
form
relatively
localized
the
tendency
deposits.
BIBLIOGRAPHY
Bathurst, R.G.C.,
diagenesis.
1971, Carbonate
Elsevier.
sediments
and
their
Bissell, H.J., 1962, Pennsylvanian and Permian rocks of the
Cordilleran area, p 188-262 in Pennsylvanian System of
the United States---a
symposium: Amer. Assoc. of
Petroleum Geologists, 508 p.
Bissell, H.J., 1970, Realms of Permian Tectonism and
Sedimentation in Western Utah and Eastern Nevada: Amer.
Assoc.
of Petroleum Geologists Bull., v 54, p 285-312.
Burchfiel, B.C.
Mountains,
et al, 1964,
Nevada.
Geologic Map
of
the
Spring
Burchfiel, B.C. and Davis, G.A., 1972, Structural Framework
and Evolution of the Southern part of the Cordilleran
Orogen, Western United States: Amer. Jour. of Science
v 272, p 97-118.
Cook,
H.E. and Mullins, H.T., 1983, "Basin Margin
Environment" in Carbonate Depositional
Environments.
Ed. by P.A. Scholle, D.G. Bebout, C.H. Moore.
Amer.
Assoc. of Petrolem Geologists, Memoir #33.
Friedman, G.M. ed. 1969, Depositional Environments in
Carbonate Rocks: Society of Economic Paleotologists
Mineralogists, Special Publication #14, 207 p.
and
Langenheim, R.L., et al, 1962, Paleozoic section in Arrow
Canyon Range, Clark County, Nevada: Amer. Assoc. of
Petroleum Geologists Bull. v.46, p 592-609.
Ledbetter, M.T., 1970, A Pennsylvanian-Permian Shelf to Craton
Transition, Azure Ridge, Clark County, Nevada: Unpub.
Masters thesis, Memphis State University, 96 p.
Longwell, C.R. and Dunbar, C.O., 1936, Problems of
Pennsylvanian-Permian Boundary in Southern Nevada: Amer.
Assoc. of Petroleum Geologists Bull. v 20, p 1198-1207.
Hewett, D.F., 1931, Geology and Ore Deposits in the
United States
Goodsprings Quandrangle, Nevada:
Geological Survey Prof. Paper 162.
Rich,
M., 1963, Petrographic Analysis of Bird Spring Group
(Carboniferous-Permian) near Lee Canyon, Clark County,
Nevada:
Amer.
Assoc. of Petroleum Geologists Bull. v 47,
p 1657-1681
Rich, M., 1964, Petrographic Classification and Method of
Description of Carbonate Rocks of the Bird Spring Group
in Southern Nevada: Journal of Sed. Pet. v 34,
p 365-378.
Smith, G.T., 1972, Sedimentary Petrology of the Callville
Limestone and Pakoon Formation (Pennsylvanian-Permian) at
Iceberg Canyon, Clark County, Nevada: Unpub. Masters
thesis, Memphis State University, 104 p.
Steele, G., 1959, Stratigraphic Interpretation of the
Pennsylvanian-Permian Systems of the Eastern Great
PhD thesis, University of Washington, 294 p.
Basin:
Stewart, J.H.,
1972,
Initial
Deposits in the Cordilleran
Geosyncline: Evide.nce of a Late Precambrian (850 m.y.)
Continental Separation: Geol. Soc. of Amer. Bulletin,
v. 83, p 1345-1360.
Wilson, J., 1975, Carbonate Facies
Springer-Verlag.
in Geologic History.
APPENDIX:
DETAILED
I Lee
Bed #
DESCRIPTION OF SECTIONS
Canyon
Section
Thickness
in meters
Cumulative
thickness
in meters
Description
5.0
5.0
Massive coarse-grained mediumgray-weathering limestone with
many crushed fossil fragments.
Chertified brachiopods in some
layers. One 2.5 cm layer of
rusty brown chert.
Ledgy.
1.0
6.0
Covered
0.3
6.3
Fine-grained reddish siltstone
with some whole fossils.
0.5
6.8
Dense medium-grained, mediumgray limestone. Few large
fossil fragments.
5.0
11.8
Covered
1.0
12.8
Fine-grained light-gray to
medium-gray Limestone with few
large whole fossils
and
scattered
fragments.
5.0
17.8
Covered
1.5
19.3
Dense fine-grained medium-gray
limestone.
Some chertified
brachiopods. Chert nodules,
15 by 30 cm.
Dense 8 cm black
chert layer at top.
3.5
22.8
Covered
2.7
25.5
Fine-grained medium-gray silty
limestone.
Abundant chert
pods in layers 8 cm thick.
A few brachiopods present.
0.5
26.0
Medium-grained medium-gray
limestone with one bed of
brown chert nodules,
30 cm
diameter.
interval
interval
interval
interval
in
2.7
28.7
Covered
interval
2.0
30.7
Medium-grained medium-gray
limestone with layers of black
chert nodules.
Bed #
ABS
7
Thickness
in meters
Cumulative
thickness
in meters
Description
2.7
33.4
Covered
2.5
35.9
Fine-grained and mediumgrained light-gray to
medium-gray limestone. Some
layers are coarser grained
fragments.
fossil
with visible
Brownish chert nodules
Ledgy.
present.
3.5
39.4
Fine-grained to medium-grained
light-gray, peach-weathering
siltstone.
1.5
40.9
Medium-grained medium-gray
limestone.
3.0
43.9
Covered
1.0
44.9
Medium-grained medium-gray
limestone with abundant gray
and black chert nodules and
beds.
2.1
47.0
Covered
2.4
49.4
Fine-grained light-gray silty
limestone. Weathers tan.
2.1
51.5
Medium-grained medium gray
limestone with rust-brown
chert nodules and beds. Some
chert-replaced brachiopods.
2.7
54.2
Covered
1.0
55.2
Fine-grained pinkish siltstone
with one layer of dense black
chert, 8 cm thick.
5.4
60.6
Covered
3.0
63.6
Medium-grained medium-gray
Coarsens near top
limestone.
Some chert-replaced
brachiopods,some dark-gray
chert nodules.
5.0
68.6
Covered
interval
interval
interval
interval
interval
interval
Bed #
Thickness
in meters
Cumulative
thickness
in meters
Description
ABS
6.5
75.1
Bottom 2 m is fine-grained to
medium-grained crystalline
limestone with chert layers,
8 to 20 cm thick, and approx.
0.5 m apart.
Middle 3 m is
massive featureless
finegrained medium-gray limestone.
Top 1.5 m is composed of
medium-grained medium-gray
limestone containing crossstratified
1 cm thick chert
layers.
Cliff former.
2.1
77. 2
Covered
3.0
80.2
Fine-grained medium-gray to
dark-gray limestone.
Some
beds of densely packed crinoid
fragments.
Chert nodules in
beds 8 to 30 cm thick.
Cliff former.
3.0
83.2
Medium-grained medium-gray to
light-gray limestone.
Some
contain 1 cm diameter
crinoid fragments.
Chert
nodules and beds present.
Cliff former.
2.5
85.7
Covered
8
interval
interval
ABS
9
1.5
87.2
Medium-grained medium-gray
limestone, some layers of
coarse fossil hash.
Some
chert beds and chert-replaced
rugose coral present.
Cliff former.
ABS
10
3.0
90.2
Fine-grained to medium-grained
medium-gray limestone.
Chertreplaced rugose coral present
in two .5 m thick beds.
Forms slopes and ledges.
4.0
94.2
Fine-grained medium-gray
limestone.
Weathers into
layers 20 to 45 cm thick. Some
orange chert layers present.
Rough and craggy at top.
Forms cliffs and ledges.
Bed
ABS
#
11
Thickness
in meters
Cumulative
Thickness
in meters
Description
10.0
104.2
Fine-grained to mediumgrained light-gray silty limeSome beds contain
stone.
coarse crinoid and brachiopod
Black chert
fragments.
nodules are abundant.
Forms slopes and ledges.
3.0
107.2
Covered
5.5
112.7
Fine-grained to medium-grained
to medium-gray
light-gray
limestone with abundant
silty
black chert nodules in beds
Weathers shaley.
15 cm apart.
ledges.
and
Forms slopes
2.0
114.7
Medium-grained medium-gray
Concentrically
limestone.
layered chert nodules 8 cm in
diam. present in lower 1 m.
Top 1 m contains dense orange
Forms a ledge.
chert layers.
2.0
116.7
Covered
2.0
118.7
interval
interval
Coarse-grained
crystalline
medium-gray to light-gray
Several
massive limestone.
15 cm thick.
chert beds,
Forms a ledge.
ABS
12
12 .5
131.2
Fine-grained to medium-grained
medium-gray to light-gray
silty limestone with abundant
Some beds of
chert nodules.
coarse fossil fragments.
Forms slopes and ledges.
2.4
133.6
Coarse-grained medium-gray
Thin chert beds
limestone.
accentuate large-scale
cross-stratification.
Forms a ledge.
7.5
3.5
141.1
144.6
Covered interval
Fine-grained to medium-grained
light-gray silty limestone
with orange-brown chert beds.
46
Bed
#
-
Thickness
in meters
Cumulative
thickness
in meters
1.0
145.6
Medium-grained medium-gray
limestone.
Massive.
Little
chert, few fossils.
Forms a ledge.
0.5
146.1
Covered
0.5
146.6
Medium-grained to coarsegrained medium-gray limestone.
Massive. Ledge former.
2.5
149.1
Covered
Description
interval
interval
Pahrump
Section
Bed #
Thickness
in meters
Cumulative
thickness
in meters
Description
BS
1.8
1.8
Coarse-grained crystalline
medium-gray limestone with
some large calcite-replaced
fossils.
Ledge former.
0.6
2.4
Covered
0.6
3.0
Fine-grained to medium-grained
medium-gray crystalline limestone.
Forms a ledge.
0.6
3.6
Covered
0.6
4.2
Fine-grained to medium-grained
medium-gray crystalline
limestone.
Forms a ledge.
1.0
5.2
Covered
0.3
5.5
Fine-grained to medium-grained
medium-gray crystalline limestone.
Forms a ledge.
0.6
6.1
Covered
0.3
6.4
Fine-grained crystalline limestone at bottom, coarsegrained crystalline
limestone
at top.
Medium-gray.
Some coarse fossil fragments.
Forms a ledge.
3.0
9.4
Covered
1.5
10.9
Fine-grained light-gray
silty
limestone,
grading up to
fine-grained medium-gray to
dark-gray unsilty limestone.
Forms a prominent ledge.
1.0
11.9
Covered
0.6
12. 5
Fine-grained medium gray to
light-gray
limestone,
slightly
silty.
Few large fossil
fragments, some chert nodules.
Forms a ledge.
BS
BS
8
9
12
interval
interval
interval
interval
interval
interval
Bed #
BS
BS
BS
13
14
15
Thickness
in meters
Cumulative
thickness
in meters
Description
0.5
13.0
Fine-grained dark-gray limeOne dense black chert
stone.
bed, 15 cm thick.
Forms a ledge.
1.5
14.5
Covered
1.8
16.3
Fine-grained to medium-grained
pinkish-weathering silts tone.
Forms a ledge.
0.6
16.9
Medium-grained
limestone.
Forms a ledge.
0.6
17 .5
Covered
0.6
18. 1
Fine-grained slightly
light-gray limestone.
Forms a small ledge.
1.5
19 .6
Covered
1.2
20.8
Fine-grained slightly silty
dark-gray limestone with some
chert nodules and beds.
One
15 cm layer of calcite
replaced brachiopods, 15 cm from
top of bed.
Ledge former.
3.6
24.4
Fine-grained pink-brown
weathering siltstone.
Slope former.
4.2
28.6
Covered
1.0
29 .6
Fine-grained to medium-grained
light-gray
to medium-gray
limestone.
Dense black chert
layer at top, one bed of
brachiopods present in center
of bed.
Forms a small ledge.
1.5
31.1
Covered interval
0.3
31.4
Fine-grained medium-gray
limestone.
Forms small ledge.
6.0
37.4
Medium-grained medium-gray
limestone with chert. Ledge.
interval
dark-gray
interval
silty
interval
interval
Bed
BS
BS
#
16
17
Thickness
in meters
Cumulative
thickness
in meters
Description
3.0
40.4
Covered
2.4
42.8
Fine-grained light-gray
limestone. Some chert nodules,
a few layers of brachiopods.
Ledge and slope former.
3.0
45.8
Fine-grained to medium-grained
dark-gray to medium-gray limestone.
Chert is common.
Forms slopes and ledges.
1.5
47 .3
Covered
4.5
51.8
Fine-grained to medium-grained
dark-gray to medium-gray limestone.
Contains some concentrically layered chert and a
few layers of coarse fossil
fragments, including
Brachiopods.
Forms ledges.
3.0
54.8
Covered
6.0
60.8
Alternating layers of brown
chert and light-gray to
medium-gray limestone.
Chert
seen both as beds and as
hollow balls,
5 cm diam.
Brachiopod fragments are
present. Forms a cliff.
1.2
62.0
Covered
1.0
63.0
Fine-grained light-gray silty
limestone with some beds of
brachiopods and crinoid stems.
Forms a small ledge.
5.4
68.4
Covered
4.5
72.9
Fine-grained blue-gray
limestone with many layers of
dark-gray dense chert pods.
Very pure, semi-crystalline.
Cliff former.
3.0
75.9
Fine-grained pink and orangeweathering siltstone.
Few
Chert nodules. Fresh surface
is dark-gray.
Forms slopes.
interval
interval
interval
interval
interval
Bed
#
Thickness
in meters
Cumulative
thickness
in meters
Description
22.5
98.4
Fine-grained to medium-grained
blue-gray very cherty semicrystalline limestone. No
silt. Forms massive cliffs.
2.4
100.8
Fine-grained to medium-grained
medium-gray limestone with
several beds of orange-brown
chert balls.
Smells of
sulphur when freshly broken.
1.5
102.3
Covered
Fine-grained light-gray to
medium-gray slightly silty
limestone with 3 cm thick
chert beds accentuating largescale cross-stratification.
Cliff former.
Fine-grained semi-crys talline
blue-gray limestone.
Few
beds of chert nodules. Some
beds contain coarse fossil
hash. Forms Ledges and slopes.
interval
BS
20,
21
4.5
106.8
BS
19
9.0
115.8
BS
22
3.0
118.8
Medium-grained medium-gray
limestone with abundant chert
nodules and beds.
Some layers
contain coarse fossil
hash.
Forms cliffs.
1.5
120.3
Covered
1.8
122.1
BS
23
interval
Fine-grained
semi-crystalline
medium-gray limestone with
large chert-replaced colonial
corals.
Ledge former.
BS
24
1.5
123.6
Covered
1.5
129.2
Fine-grained medium-gray
limestone, weathers rough and
craggy.
One brown chert bed
in middle, 0.5 m thick.
Forms a small cliff.
1.5
126.6
Covered
2.1
128.7
Fine-grained light-blue-gray
limestone, few fossil hash.
Dark gray chert in beds and
nodules. Some chert replaced
colonial coral. Forms a ledge.
interval
interval
Bed #
BS
25
Thickness
in meters
Cumulative
thickness
in meters
Description
6.0
134.7
Fine-grained light-gray
limestone with dark-gray chert
Slope former.
nodules.
1.0
135.7
to
Medium-grained light-gray
medium-gray limestone with
several beds of dense brown
chert.
1.5
137.2
Fine-grained
orange-brown-
with
weathering siltstone
Slope former.
chert nodules.
BS
26
0.3
137.5
Coarse-grained tan-weathering
semi-crystalline fossil hash.
Ledge former.
BS
27
4.5
142.0
Fine-grained light-gray siltyweathering limestone with many
chert nodules.
Ledge former.
BS
28
4.5
146.5
Medium-grained medium-gray
limestone with several beds of
coarse grainstone. Some chertreplaced fossil
fragments.
a
cliff.
Forms
1.5
148.0
Covered
4.0
152.0
Coarse-grained medium-gray
limestone with beds of fossil
hash.
Chert nodules and beds
are common.
Forms a cliff.
3.0
155.0
Covered
interval
interval