AlecLeeSeniorThesis

1

Colorado
College

Department
of
Geology

Paleo
Fluid-‐Flow
in
Crystalline-‐Hosted
Sandstone
Injectites

from
the
Neoproterozoic
–
Evidence
for
the
Migration
of

Hydrocarbons
in
the
Colorado
Front
Range

A
Thesis

Submitted
to
the
Department
of
Geology
Faculty

In
Partial
Fulfillment
of
the
Requirements
for
the

Degree
of

Bachelor
of
Arts

By

Alec
Lee

Colorado
College

May
2015

2

A
C
K
N
O
W
L
E
D
G
E
M
E
N
T
S

I
would
like
to
thank
Christine
Siddoway
for
her
unwavering
support
and
guidance

throughout
this
thesis
project,
Monte
Swan
and
Stan
Keith
for
their
assistance
in
decoding

the
whole
rock
geochemical
and
diamondoid
hydrocarbon
data,
the
Patricia
Buster
Grant,

the
Creager
Award,
the
Colorado
College
Natural
Science
Division
Grant,
and
the
Colorado

College
Geology
Department
funds
that
collectively
funded
my
research,
the
entire

Colorado
College
Geology
Department
with
special
emphasis
on
Mandy
Sulfrian,
my

mother,
Aleisha,
and
Alex
Hager
and
Maggie
Bailey
for
believing
in
me
when
I
thought
I

would
never
finish.

3

T
A
B
L
E

O
F

C
O
N
T
E
N
T
S

ACKNOWLEDGEMENTS……………………….……………………………………………………...…………2

ABSTRACT……………………………………………………………………….……………………………………4

INTRODUCTION……………………………………………….……………………………………………………5

GEOLOGICAL
BACKGROUND……………………….…………………………………………………………7

Regional
Geology………………………………………………………………………………………….…………………7

Neoproterozoic
Setting…………………………………………………………………………………………….……11

Neoproterozoic
Sediment…………………………………………………………………………………….………...13

Global
Sandstone
Injectites…………………………………………………………………………….……………...14

Proterozoic
Petroleum
Sources…………………………………………………………………….………………..15

Regional
Petroleum
Sources………………………………………………………………………………….……….17

METHODS………………………………………………………………………………….……………..………...19

THIN
SECTION
PETROGRAPHY……………………………………………………………………………20

Grain
Sorting………………………………………………………………………………………………………….……..21

Cement……………………………………………………………………………………………………………….…………22

Deformation
Bands………………………………………………………………………….…………………………….22

Fluid
Inclusions……………………………………………………………………………………………….…………….22

Quartz
and
Calcite
Veins…………………………………………………………….………………………………….23

Fluid
Controls………………………………………………………………………….…………………………….………24

GEOCHEMICAL
RESULTS……………………………………………………………………………….…….25

Major
Oxides…………………………………………………………………….…………………………………………...25

Trace
Elements…………………………………………………………………………….………………………………..26

Hydrocarbons………………………………………………………………………………………….…………………….26

X-‐Ray
Diffraction…………………………………………………………………………….…………………………….29

DISCUSSION…………………………………………………………………………….…………………………..29

CONCLUSIONS……………………………………………………………………………….…………………….34

REFERENCES…………………………………………………………………………………….…………………38

TABLES
&
FIGURES……………………………………………………………………………….…………….42

4

A
B
S
T
R
A
C
T

In
the
Front
Range
of
Colorado,
an
array
of
basement-‐hosted
clastic
dikes,
sills,

and
parent
bodies
named
Tava
sandstone
(informal),
exhibit
strong

reduction/oxidation
(redox)
bleaching
from
the
migration
of
reducing
fluids.

Redox

within
Tava
sandstone
is
evident
by
the
bleaching
and/or
removal
of
primary
red

hematite
cement
that
formed
as
grain
coatings
during
early
diagenesis.

Petrographic

analyses
reveal
that
fluid
flow
within
Tava
sandstone
is
aided
by
crude
grain
sorting

and
calcite
veins,
while
structural
and
special
relationships
of
redox
patterns
indicate

that
has
been
more
than
one
influx
of
reducing
fluids
through
Tava
sandstone.

Detrital

zircon
dating
of
Tava
sandstone
yields
similar
zircon
ages
to
known
Neoproterozoic
Era

sediments
of
the
Southwestern
United
States,
and
places
the
age
of
Tava
sandstone
at

~750
Ma.

Bleaching
of
Tava
sandstone
may
have
occurred
at
any
time
throughout
the

Phanerozoic
and
possibly
even
as
far
back
as
the
Neoproterozoic.

It
is
reasonable
to

presume
that
Tava
sandstone’s
geochemistry
may
retain
a
biogeochemical
signature

from
the
Neoproterozoic
Era.

However,
Tava
sandstone
is
quartz
arenite
in

composition
(>90%
quartz),
and
is
therefore
not
an
ideal
repository
for
the

preservation
of
Neoproterozoic
Era
geochemical
fingerprints.

Hydrocarbon
screening

and
diamondoid
analyses
performed
on
a
grouping
of
Tava
samples
reveal
the
presence

of
several
n-‐alkane,
sterane,
and
terpane
hydrocarbon
species.

These
hydrocarbons

include
the
n-‐Alkanes
n-‐C10,
n-‐C12,
n-‐C15
and
n-‐C20-‐31
with
peaks
at
n-‐C23
and
n-‐C29,

as
well
as
species
of
steranes,
terpanes,
and
carotenoids.

Whole
rock
analysis
on
Tava

sandstone
reveals
reduced
ratios
(<0.5)
of
Fe2O3
to
FeO,
further
validating
the
reducing

nature
of
fluid
migration
through
Tava
sandstone.

These
compounds
may
not
only

uncover
the
source
of
hydrocarbons
found
in
Tava
sandstone,
but
may
also
reveal
the

evolution
of
hydrocarbon
generation
and
migration
in
the
Colorado
Front
Range,
which

is
a
continually
expanding
energy
resource
in
the
Rocky
Mountain
region.

Further

geochemical
analysis
on
Tava
sandstone
may
expose
the
true
source
of
hydrocarbons,

timing
of
migration,
and
shed
light
on
the
paleo-‐climate/geography
of
inland
Laurentia

following
the
breakup
of
Rodinia,
750
Ma,
a
region
that
is
poorly
known.

Figure
A.

Left,
partially
bleached
Tava
from
near
Woodland
Park,
Colorado;
middle,
primary
hematite

cemented
Tava
from
Williams
Fork
Range,
Colorado;
right,
mottled
bleached
Tava
from
Keeton
Ranch,

Colorado.

5

I
N
T
R
O
D
U
C
T
I
O
N

Along
the
Ute
Pass
Fault
of
the
Colorado
Front
Range
a
network
of
basement-‐
hosted
clastic
dikes
and
parent
bodies
exhibit
redox
patterns
from
the
migration
of

reducing
fluids
(Figure
A).

Tava
sandstone
(informal)
is
structureless,
composed
of

well-‐rounded
quartz
pebbles,
feldspar
fragments,
and
lithic
clasts
separated
and

suspended
within
a
matrix
of
mature,
fine
to
medium-‐grained
quartz
(Siddoway
et
al.,

2013).

Tava
sandstone
forms
tabular
bodies
and
dikes
at
intervals
along
the
entire
~80

km
length
of
the
Ute
Pass
Fault
zone
(Figure
1
and
2).

Dominant
ages
of
detrital
zircons

from
Tava
sandstone
are
1.7
Ga,
1.4
Ga,
and
1.33-‐0.97
Ga
(Siddoway
and
Gehrels,
2014),

a
distribution
that
correlates
with
other
Grenville-‐orogen-‐derived
sedimentary
units
of

the
American
Southwest
(Siddoway
and
Gehrels,
2014)
(Figure
3).

On
this
basis,
Tava

sandstone
is
Neoproterozoic
in
age.

The
source
of
sediment
that
formed
Tava

sandstone
may
have
been
deposited
in
rift
basins
that
formed
during
the
breakup
of
the

supercontinent,
Rodinia,

~750
Ma
(Dehler
et
al.,
2010;
Siddoway
et
al.,
2013;
Yonkee
et

al.,
2014).

Evidence
for
the
migration
of
reducing
fluids
in
Tava
sandstone
includes
redox

patterns
and
secondary
porosity.

The
potential
source
of
reducing
fluids
includes

hydrocarbon
source
rocks
of
Colorado
from
lithological
units
that
span
the
entire

Phanerozoic,
or
the
possibility
of
in
situ
generation
of
hydrocarbons
from
bacterial

matter
originally
deposited
within
Tava
sandstone
during
the
Neoproterozoic
Era

(Clayton
and
Swetland,
1980;
Craig
et
al.,
2013;
Johnson
and
Rice,
1990).

Primary
Tava
cement
is
deep
maroon
colored
from
the
breakdown
of
detrital

ferromagnesian
minerals,
precipitated
as
hematite
grain
coatings
during
early

diagenesis
(e.g.
Beitler
et
al.,
2003)
(Figure
4).

Bleached
Tava
sandstone
is
often
more

6

friable
and
white-‐tan-‐pink
in
color
from
a
change
in
oxidation
state
and/or
the
removal

of
hematite.

In
sediment,
hematite
is
insoluble
(ferric
iron,
Fe3+)
and
must
be
reduced

to
ferrous
iron
(Fe2+)
in
order
to
become
soluble
in
solution
and
removed
(chemically

bleached)
(Surdham
et
al.,
1993)
(Figure
4).

Reducing
fluids,
such
as
hydrocarbons,
can

cause
the
reduction
and
removal
of
iron
from
sandstone
during
fluid
migration
(Beitler

et
al.,
2003;
Eichhubl
et
al.,
2004;
Levandowski
et
al.,
1973;
Moulton,
1922;
Parry
et
al.,

2003;
Rainoldi
et
al.,
2014;
Shebl
and
Surdam,
1996).

Early
investigations
on
sandstone
redox
reactions
were
carried
out
in
1922
on

the
petroleum-‐rich
Chugwater
redbeds
in
Montana
(Moulton,
1922).

Moulton

concluded
that
red
sandstone
could
be
bleached
by
hydrogen
sulfide,
a
known

byproduct
of
petroleum
generation
(Moulton,
1922).

Additionally,
in
pyrolysis
analyses

performed
Shebl
and
Surdam,
(1996)
a
mixture
of
red
rock,
water,
and
hydrocarbons

became
altered
to
light
pink,
white,
gray,
or
dark
gray.

Crude
grain
sorting
observed
within
Tava
sandstone
contributes
to
primary

porosity
and
may
serve
as
preferential
fluid
migration
pathways
in
the
absence
of

structural
conduits
(Figure
5).

Examination
of
outcrops,
hand
samples,
and
thin

sections
show
that
deformation
bands
and
calcite
veins
may
also
serve
as
fluid-‐flow

controls
within
Tava
sandstone
(Figure
6,
7,
8).

Cataclasis
and
deformation
bands
are

observed
in
a
majority
of
Tava
locations
and
are
found
in
both
primary
Tava
and
Tava

containing
redox.

Brittle
deformation
potentially
responsible
for
the
structural

overprinting
observed
in
Tava
sandstone
include
compaction
during
original

lithification
and
structural
overprinting
during
the
Ancestral
Rocky
Mountain
Orogeny,

and
the
Laramide
Orogeny.

The
aims
of
this
study
are:
1)
establish
fluid
flow
controls
within
Tava
sandstone,

2)
determine
the
characteristics
and
probable
source(s)
of
reducing
fluids
responsible

7

for
redox,
and
3)
infer
the
tectonic
event(s)
or
alternate
mechanisms
responsible
for
the

initiation
of
fluid
flow
within
Tava
sandstone.

The
significance
of
this
study
is
three-‐part.

First,
Tava
sandstone
is

Neoproterozoic
in
age,
and
therefore
has
the
potential
to
reveal
the
paleoenvironment

of
inland
Laurentia
during
the
breakup
of
Rodinia,
as
well
as
aspects
of
the

geobiochemistry
of
the
late
Proterozoic
Eon
prior
to
the
‘Cambrian
Explosion’.

Crystalline-‐hosted
sandstone
dike
complexes
are
an
extremely
rare
geological

occurrence.

Because
deep
marine
sandstone
dike
complexes
are
becoming
a
major
play

for
oil
exploration,
the
presence
of
hydrocarbons
in
Tava
sandstone
may
lead
to
other

crystalline-‐hosted
sandstone
dike
complexes
becoming
potential
targets
for
oil

exploration.

Tava
sandstone
contains
visible
redox
patterns
that
may
reveal
critical

information
about
the
evolution
and
migration
of
hydrocarbons
that
serve
as
energy

resources
in
Colorado,
for
example
insights
into
thermal
maturation
of
sub-‐thrust

Phanerozoic
strata
(Gries,
1983;
Wandrey
and
Barker,
1995)
within
the
Front
Range

basement
uplift
that
formed
during
the
Ancestral
Rockies
and
Laramide
Orogeny.

G
E
O
L
O
G
I
C
A
L

B
A
C
K
G
R
O
U
N
D

Regional
Geology

The
Front
Range
in
Colorado
has
a
long
and
complex
regional
geology
including:

1)
formation
of
Colorado
basement
rocks
in
an
accretionary
province
during
the

Proterozoic;
2)
Rodinia
rifting
and
formation
of
a
brittle
structural
framework
within

the
basement
rocks
of
Colorado
during
the
Neoproterozoic
Era;
3)
deposition
of
Tava

sandstone
despite
extensive
erosion
between
1.1
Ga
and
0.54
Ga
resulting
in
the
Great

Unconformity;
4)
deposition
of
Paleozoic
siliciclastics
and
carbonates
in
Laurentian

8

epeiric
seas;
5)
reactivation
of
basement
faults
at
the
time
of
the
Ancestral
Rocky

Mountain
Orogeny;
6)
deposition
of
Cretaceous
Interior
Seaway
deep
marine
and

carbonate
sediments;
7)
reactivation
of
basement
faults
during
the
Laramide
Orogeny.

Proterozoic
basement
rocks
in
Colorado
include
plutons
emplaced
within
the

Yavapai
(2.0-‐1.8
Ga)
and
Mazatzal
(1.8-‐1.6
Ga)
accretionary
provinces
as
well
as

subsequent
anorogenic
magmatism
at
the
time
of
the
Grenville
orogeny
(Pikes
Peak

Batholith,
1.1
Ga)
(Yonkee
et
al.,
2014).

In
Colorado,
these
accretionary
terranes

comprise
magmatic
and
metamorphic
complexes
at
about
1.78-‐1.75
Ga,
1.67
Ga,
and
1.4

Ga,
that
all
contain
evidence
of
tectonic
overprinting
(Tweto,
1980).

The
Pikes
Peak

batholith
(1.1
Ga)
does
not
display
dynamic
fabrics.

Rodinia
underwent
large
scale
rifting
~750
Ma,
culminating
in
the
breakup
of

Rodinia
and
the
eventual
isolation
of
Laurentia
(Dehler
et
al.,
2010;
Yonkee
et
al.,
2014).

The
evolutionary
history
of
the
ancient
rift
zone,
active
from
825-‐740
Ma,
has
been

reconstructed
from
Neoproterozoic
episodic
plume
events
as
well
as
from
the

arrangement
of
Neoproterozoic
marine
sediments
found
in
south
Australia,
south

China,
Namibia,
and
western
North
America
(Dehler
et
al.,
2010;
Li
et
al.,
2007).

The

onset
of
rifting
is
indicated
by
the
Gairdner-‐Amata
dike
swarm
in
Australia
at
825
Ma

and
the
Gunbarrel
dike
swarm
in
western
Laurentia
at
780
Ma
(Li
et
al.,
2007).

The
dike

swarms
are
a
result
of
a
super-‐plume
that
formed
below
Rodinia
due
to
enhanced

thermal
gradients
(Li
et
al.,
2007).

Following
the
onset
of
rifting,
the
Laurentian
passive

margin
and
accompanying
continental
rift
basins
became
depocenters
for
marine
and

coastal
sediment.

Rifting
caused
basement
rocks
to
undergo
crustal
thinning,
which
led

to
the
development
of
high
angle
normal
faults
aligned
parallel
to
the
rift
margin.

One

such
fault
may
be
the
ancestral
Ute
Pass
Fault
of
the
Colorado
Front
Range
(Siddoway
et

al.,
2013).

9

The
origin
of
the
Ute
Pass
Fault
may
be
tied
to
the
break
up
of
Rodinia
for
three

reasons:
1)
its
orientation
is
parallel
to
the
west
coast
Laurentian
rift
margin,
2)
there
is

a
probability
that
Tava
sandstone
was
emplaced
as
an
injectite
within
the
fault
zone,

and
3)
the
age
of
Tava
sandstone
places
it
within
the
time
frame
of
other
rifting

structures
(Dehler
et
al.,
2010;
Yonkee
et
al.,
2014).

The
Ute
Pass
Fault
may
have
been
the
control
upon
an
inland
rift
basin
that

formed
during
the
rifting
of
Rodinia.

In
the
continental
interior,
the
paleo-‐Ute
Pass

Fault
rift
basin
accumulated
far-‐traveled
sediment
transported
from
the
Grenville

orogen
(Figure
9).

In
this
tectonic
setting
Tava
sandstone
experienced
an
extreme
fluid

over-‐pressurization,
and
was
then
injected
into
crystalline
basement
rock
possibly
due

to
rupture(s)
and
seismicity
along
the
ancestral
Ute
Pass
Fault.

The
result
was
the

formation
of
the
Tava
sandstone
injectite
complex.

Prior
to
and
following
the
formation
of
Tava
sandstone
injectites,
the
Front

Range
underwent
large
scale
erosion
resulting
in
the
Great
Unconformity,
which
before

the
discovery
of
Tava
sandstone,
was
believed
to
have
erased
the
entire
geological

record
of
eastern
Colorado
between
1.1
Ga
and
0.54
Ga.

Therefore,
Tava
sandstone

serves
as
the
only
known
vestige
of
inland
Laurentia
(eastern
Colorado)
during
the

Neoproterozoic
Era.

Above
the
Great
Unconformity
lies
Early
Cambrian
mature
Sawatch
Sandstone

deposited
directly
atop
Pikes
Peak
Granite.
Next
are
shallow
marine
carbonates

(Manitou,
Williams
Canyon,
and
Hardscrabble
Limestones)
that
were
deposited
within

epeiric
seas
of
Laurentia
(Figure
10).

The
epeiric
seas
covering
western
Laurentia

served
as
a
catalyst
for
the
explosion
of
vast
marine
ecosystems.

Cambrian
through

Devonian
siliciclastics
and
carbonates
record
a
great
diversification
of
metazoan

invertebrates,
as
well
as
the
establishment
of
aerobic
life
forms
capable
of
inhabiting

10

the
continents
(Levin,
2003
p.337).

The
shallow
seas
of
Colorado
during
the
early

Paleozoic
were
drained
by
tectonism
associated
with
the
Ancestral
Rocky
Mountain

Orogen
(ARMO).

To
accommodate
stress,
the
Ute
Pass
Fault
reactivated,
causing
uplift

and
erosion
of
Pikes
Peak
Granite
and
older
basement
rocks.

Erosion
of
exposed

basement
led
to
the
deposition
the
arkosic
Pennsylvanian
Fountain
Formation

unconformably
atop
sediments
of
the
early
Paleozoic
siliciclastics
and
carbonates

(Figure
10).

Following
the
ARMO,
terrestrial
sedimentation
took
place
during
the
Permian,

Triassic
and
Jurassic,
while
the
Cretaceous
Interior
Seaway
laid
down
deep
marine

shales
and
shallow
carbonate
facies.

The
Laramide
Orogeny
caused
reactivation
of
the

Ute
Pass
Fault
again
during
the
late
Cretaceous-‐Paleocene
Period
boundary
resulting
in

the
formation
of
monoclinal
structures
along
the
Front
Range.

Today,
the
Ute
Pass
Fault
runs
from
Turkey
Creek
to
north
of
Woodland
Park

separating
two
Laramide
basement
uplifts,
the
Rampart
Range
and
the
Front
Range.

Near
its
southern
end,
the
fault
has
reverse
motion,
trends
N-‐S,
and
dips
between
0-‐70

degrees
to
the
west,
while
its
central
and
northern
segments
trend
northwest,
dip
very

steeply,
and
have
left
lateral
displacement
(Keller
et
al.,
2003).

Following
cementation,
Tava
sandstone
remained
hosted
within
crystalline

basement
rocks
along
the
Ute
Pass
Fault
for
~750
million
years,
and
during
its
long

history
has
been
subjected
to
all
events
associated
with
the
Ute
Pass
Fault
including

tectonism,
diagenetic
alteration,
and
fluid
migration.

Despite
tectonic
overprints
from

the
Phanerozoic
Eon,
there
are
pristine
exposures
that
retain
primary
characteristics

capable
of
illuminating
Neoproterozoic
biogeochemical
signatures.

11

Neoproterozoic
Setting

During
the
Neoproterozoic
Era
(1.0
Ga.
–
0.54
Ga.),
the
supercontinent
Rodinia

was
both
created
and
fragmented.

Furthermore,
the
entire
globe
fell
into
icehouse

conditions
during
the
Cryogenian
Period
(850
Ma
–
635
Ma)
appropriately
named

‘Snowball
Earth’.

The
interplay
of
paleogeography,
biological
diversification,
and

atmospheric
oxygenation
during
global
continental
reconfiguration
of
the

Neoproterozoic
is
of
great
importance
in
understanding
the
evolution
of
life
on
Earth.

Research
into
the
geochemistry
of
Tava
sandstone
may
reveal
geochemical
fingerprints

from
the
Neoproterozoic.

Although
oxygen
is
highly
abundant
in
today’s
atmosphere,
before
the
advent
of

oxygen-‐producing
(photosynthesizing)
organisms,
the
atmosphere
was
anoxic,

comprised
of
methane,
ammonia,
hydrogen,
and
water
vapor
(Levin,
2003
p.
215).

High

atmospheric
oxygen
concentrations
formed
in
two
great
oxygenation
events
prior
to
the

Precambrian-‐Phanerozoic
boundary

(i.e.
Cambrian
explosion)
(Och
and
Shields-‐Zhou,

2012).

Atmospheric
oxygenation
levels
have
been
estimated
by
the
rise
and
fall
of

banded
iron
formations
(BIF)
deposited
mainly
between
3.5
Ga
-‐
1.8
Ga.

Banded
iron

formations
were
deposited
in
oceans
of
the
Precambrian
and
formed
during
the

reaction
of
iron,
supplied
at
mid
oceanic
ridges
and
from
continental
weathering,
with

oxygen
produced
by
photoautotrophs
such
as
stromatolites
(Levin,
2003
p.
236).

Deposition
continued
globally
for
~1.7
Ga
and
constitutes
a
majority
of
today’s
iron
ore

deposits.

Banded
iron
formations
ceased
to
form
once
oxygen
production
exceeded

iron
replenishment
leading
to
the
first
oxygenated
atmosphere
by
~2.2
Ga
(i.e.
Great

Oxygenation
Event).

The
foundation
of
life
on
Earth
began
with
prokaryotes
at
~3.5
Ga
during
the

Archean.

The
first
diversification
of
life
took
place
at
2.2
Ga
with
the
emergence
of

12

eukaryotes,
such
as
cyanobacteria.

Life
on
Earth
remained
unchanged
until
the

development
of
metazoans
at
~640
Ma,
marked
by
thin
fleshy
marine
invertebrates
of

the
Ediacaran
Fauna
uncovered
in
southern
Australia
(Narbonne
and
Gehling,
2003).

These
first
two
biological
advancements
correspond
to
the
first
two
atmospheric

oxygenation
events:
the
Great
Oxygenation
Event
(GOE)
between
2.4-‐2.0
Ga
and
the

Neoproterozoic
Oxygenation
Event
(NOE)
between
0.8-‐0.5
Ga.

The
Neoproterozoic
Oxygenation
Event
can
be
partially
explained
by
two

geological
processes:
1)
the
formation
of
numerous
passive
margins
following
the

fragmentation
of
Rodinia,
and
2)
the
East
African-‐Antarctic
orogeny
(Transgondwanan

Supermountains).

During
the
early
Neoproterozoic
Era,
passive
margin
shallow
seas
were
scarce

due
to
the
loss
of
coastal
platforms
during
the
formation
of
Rodinia.

However,
after
the

rifting
of
Rodinia
(~750
Ma),
passive
margin
shallow
seas
became
abundant
as
more

coastlines
were
created
along
rift
margins.

Passive
margins
are
known
to
be
zones
of

organic
material
burial,
which
allows
for
the
accumulation
of
atmospheric
oxygen.

Additionally,
the
burial
of
organic
material
led
to
the
development
of
hydrocarbon

source
rocks
along
continental
margins
during
this
time
(LeHeron
and
Craig,
2012).

Further
elevation
of
atmospheric
oxygen
was
caused
by
the
East
African-‐Antarctic

orogeny
(EAO)
(650-‐515
Ma).

The
EAO
was
caused
by
the
closure
of
the
Mozambique

Ocean,
which
led
to
the
convergence
of
East
and
West
Gondwana
in
the
greatest

mountain
building
episode
in
Earth’s
history
(Och
and
Shields-‐Zhou,
2012).

Large
scale

continental
collision
led
to
greater
atmospheric
oxygenation
by
increased
erosion
rates,

which
in
turn
sent
an
abundance
of
nutrients
to
the
oceans,
therefore
increasing

photosynthesizing
organisms
that
respired
oxygen
into
the
atmosphere
(Och
and

Shields-‐Zhou,
2012;
Squire
et
al.,
2006).

13

The
snowball
earth
theory
is
substantiated
by
the
discovery
of
globally
extensive

diamictite
formations
capped
by
carbonate
formations.

Diamictite-‐cap
carbonate
series

record
two
global
glaciations,
the
Sturtian
(715
Ma)
and
the
Marinoan
(635
Ma),
as
well

as
one
regional
glaciation
in
Laurentia
(680
Ma)
(Craig
et
al.
2013;
Halverson
et
al.

2005).

Theories
concerning
how
Snowball
Earth
formed
include
the
congregation
of

the
continents
in
the
tropics
during
the
Cryogenian
Period
(Eyles
and
Januszczak,

2004).

Landmasses
are
much
more
reflective
than
oceans,
and
it
is
believed
that
much

of
the
sun’s
radiation
was
reflected
by
landmasses
back
into
space
rather
than
being

absorbed
by
the
oceans
therefore
leading
to
global
cooling
(Levin,
2003
p.
250).

Other

theories
include
a
change
in
Earth’s
obliquity
(Williams,
2008),
Earth
passing
through
a

‘rare
space-‐cloud’
(Cook-‐Anderson
et
al.,
2005),
and
a
lowering
in
Earth’s
greenhouse

gases
(Hoffman,
2002).

Diamictite
and
cap-‐carbonate
sequences
indicate
a
change
in
the
Earth’s
carbon

cycle
during
glaciation
periods.

Global
ice
sheets
restrict
CO2
from
entering
the
oceans,

leading
to
the
buildup
of
CO2
in
the
atmosphere.

Upon
the
melting
of
ice
sheets,
the

oceans
are
once
again
able
to
absorb
CO2
and
precipitate
thick
carbonate
units

(LeHeron
and
Craig,
2012).

Because
life
survived
the
proposed
Snowball
Earth
periods,

an
alternate
hypothesis
named
‘Slushball
Earth’
has
been
proposed
(Micheels
and

Montenari,
2008).

Slushball
Earth
states
that
little
to
no
ice
must
have
covered

equatorial
oceans
in
order
to
allow
photosynthesizing
algae
to
survive
the
deep
freeze

and
maintain
oxygen
in
the
atmosphere.

Neoproterozoic
Sediment

Neoproterozoic
sediments
akin
to
Tava
sandstone
are
much
less
abundant
than

Phanerozoic
sediments,
but
have
not
completely
been
erased
from
the
geological

14

record.

Grenville-‐orogen-‐derived
sediments
deposited
in
association
with
the
break
up

of
Rodinia
are
found
in
intervals
along
the
west
coast
of
Laurentia.

Neoproterozoic
in

age,
these
formations
include
the
Mackenzie
Mountains
Supergroup
(Northwest

Territories,
Canada),
Windermere
Supergroup
(British
Columbia,
Canada),
Chuar
Group

(Arizona/Utah),
Big
Cottonwood
and
Uinta
Mountain
Groups
(Utah/Colorado)
(Dehler

et
al.,
2010;
Fanning
and
Link,
2004;
Yonkee
et
al.,
2014).

A
majority
of
the
sites
were

marginal
marine
at
the
time
of
deposition.

Therefore,
a
new
contribution
to

understanding
of
Rodinia
paleoenvironments
comes
from
Tava
sandstone
(eastern

Colorado),
which
is
representative
of
an
intracontinental
setting
(Dehler
et
al.,
2010;

Siddoway
and
Gehrels,
2014).

Global
Sandstone
Injectites

Tava
sandstone
appears
to
have
served
as
a
fluid
migration
pathway
for

reducing
fluids
as
evidenced
by
its
strong
redox
patterning.

Sandstone
injectite

complexes
are
known
to
serve
as
permeable
petroleum
migration
pathways
and

reservoirs
(Hurst
et
al.,
2003;
Jonk
et
al.,
2005).

Therefore,
redox
in
Tava
sandstone

may
be
due
to
the
migration
of
hydrocarbons.

Petroleum
bearing
sandstone
injectite
complexes
are
commonly
found
in
marine

sediments
and
form
due
to
variable
pore-‐fluid
pressures
within
marine
basins
that

undergo
rapid
sedimentation
(Hurst
et
al.,
2011;
Jonk
et
al.,
2005).

The
North
Sea

graben
complexes
(Viking
and
Central
grabens)
and
California
marine
basins
(Santa

Barbara
and
Santa
Maria
basins)
are
some
of
the
world’s
leading
petroleum
producing

reservoirs,
and
they
all
contain
vast
networks
of
sandstone
injectites
(Hurst
et
al.,
2003;

Jonk
et
al.,
2005).

15

Sandstone
injectite
complexes
form
an
intricate
association
of
parent
bodies,

dikes,
and
sills
(Hurst
et
al.,
2011).

Although
sandstone
bodies
can
possess
internal

fabric
such
as
thin
laminations
and
grain
sorting,
they
are
mostly
structureless
due
to

liquefaction,
turbulent
remobilization,
and
rapid,
non-‐uniform
emplacement
(Jonk
et
al.,

2005).

Cementation
within
sandstone
dikes
is
dependent
upon
diagenetic
alteration

and
varies
among
silica,
carbonate,
and
hematite.

Due
to
variable
dike
sizes,
fluid
flow

within
sandstone
dikes
can
be
easily
controlled
by
structural
overprints
such
as

deformation
bands
or
veining.

Within
clastic
dikes
of
the
Viking
Graben,
conjugate

deformation
bands
were
formed
quickly
after
emplacement
due
to
rapid

depressurization
and
contraction
of
the
dike
margins
(Jonk
et
al.,
2005).

Deformation

bands
observed
in
the
North
Sea
contain
zones
of
authigenic
silica
precipitation
that

developed
during
deformation
band
formation
(Jonk
et
al.,
2005).

clastic
dikes
are
also
found
globally,
however
they
have
never

been
observed
as
hydrocarbon
migration
pathways.

sandstone
dike

examples
are
found
within
Precambrian
basement
rocks
at
three
known
locations

including
the
Baltic
Shield
(Friese
et
al.,
2011;
Bergman,
1982),
the
Sinai
Peninsula

(Eyal,
1988),
and
the
Colorado
Front
Range
(this
study)
(Siddoway
et
al.,
2013;

Siddoway
and
Gehrels,
2014).

Proterozoic
Petroleum
Sources

Because
Tava
sandstone
may
have
served
as
a
migration
pathway
for

hydrocarbons,
it
is
prudent
to
explore
all
potential
hydrocarbon
sources
near
the
Front

Range,
including
in
situ
hydrocarbon
generation
within
Tava
sandstone
itself.

Proterozoic
hydrocarbon
source
rocks,
although
rare,
are
not
completely
unheard
of.

Neoproterozoic
source
rocks
are
found
in
the
Chuar
Group
of
the
Grand
Canyon,
the

16

Officer,
Amadeus,
and
Georgina
basins
of
Australia,
the
eastern
Siberian
platform,
the

Huqf
basin
of
Oman,
and
the
Nonesuch
Formation
in
Michigan
(Belperio,
2007;
Craig
et

al.,
2013;
Kelly
et
al.,
2011).

Proterozoic
hydrocarbon
source
rocks
were
first
deposited
due
to
increased
life

on
Earth
during
great
oxygenation
events.

During
this
time
the
carbon
cycle
was

enriched
allowing
unoxidized
carbon
to
be
preserved
in
the
sedimentary
record
at

unprecedented
rates.

Subsequent
thermal
maturation
of
buried
organic
materials
in

these
formations
led
to
the
production
of
hydrocarbons.

One
such
Neoproterozoic

hydrocarbon
source
rock
is
the
Awatubi
Member
and
Walcott
Member
of
the
Chuar

Group
(~770
Ma)
in
northern
Arizona
and
southern
Utah
containing
total
organic

carbon
(TOC)
concentrations
between
3-‐10%
(Craig
et
al.,
2013).

The
Chuar
Group
is

believed
to
be
the
source
of
kerogen
found
in
the
Cambrian
Tapeats
sandstone
reservoir

at
the
Circle
Cliffs
in
Utah
(Craig
et
al.,
2013).

Furthermore,
Le
Heron
and
Craig
(2012)
show
that
despite
extreme
icehouse

conditions
during
the
Cryogenian,
restricted
basins
may
have
served
as
prime
locations

for
the
accumulation
and
preservation
of
organic
carbon
during
periods
of
deglaciation.

Deglaciation
periods
formed
large
isolated
water
bodies
within
intracontinental
rift

zones
of
Laurentia,
potentially
including
the
rift
basin
associated
with
the
ancestral
Ute

Pass
Fault.

Stratification
of
the
water
column
may
have
led
to
anoxic
bottoms
and

therefore
the
preservation
of
organic
carbon
from
dying
bacteria
and
algae.

Neoproterozoic
deglacial
and
post-‐glacial
sediments
serve
as
hydrocarbon
source
rocks

in
the
Centralian
Superbasin
of
Australia
(Le
Heron
and
Craig,
2012).

Neoproterozoic
hydrocarbons
have
characteristically
high
concentrations
of

hopanes
and
high
sulfur
content
from
globally
extensive
euxinic
water
conditions
that

produced
cyanobacteria
as
the
main
organic
carbon
constituent
during
that
time
(Kelly

17

et
al.,
2011).

Additionally,
they
do
not
contain
terrestrial
plant
waxes,
for
life
on
land

had
not
yet
evolved,
and
therefore
possess
higher
quantities
of
smaller
n-‐alkane

molecules.

Regional
Petroleum
Sources

No
Proterozoic
hydrocarbons
have
been
found
in
Colorado.
However,
there
are
a

plethora
of
Phanerozoic
hydrocarbon
source
rocks
in
the
Front
Range.
Petroleum

production
in
Colorado
dates
back
to
1881
with
the
discovery
of
the
Florence
Oil
Field

near
Cañon
City,
Colorado.

The
Florence
Oil
Field
is
the
second
oldest
oil
field
in
the

Unites
States,
and
although
much
of
its
resources
have
been
depleted,
there
are
many

wells
still
in
production
(Lillis
et
al.,
1998).

The
close
proximity
of
the
Florence
Oil
Field

to
the
Ute
Pass
Fault
and
Tava
sandstone
cannot
be
ignored.

Geochemical
analysis
has

determined
that
the
source
of
the
Florence
Oil
Field
is
the
Sharon
Springs
member
of

the
Cretaceous
Pierre
Shale
(Lillis
et
al.,
1998),
a
formation
that
was
thrust
beneath
the

Wet
Mountains
during
the
Laramide
Orogeny.

The
Wet
Mountain
Fault
occupies
a

structural
setting
similar
to
that
of
the
Ute
Pass
Fault
(Keller
et
al.,
2005).

In
Colorado
Springs,
another
hydrocarbon
source
rock
is
the
Upper
Cretaceous

Laramie
Formation,
the
main
horizon
in
the
Colorado
Springs
Coalfield.

The
Colorado

Springs
Coalfield
is
situated
in
north
and
northeast
Colorado
Springs
and
was

productive
between
1900-‐1950
(Morgan
et
al.,
2003).

Possible
evidence
for

hydrocarbon
migration
in
Colorado
Springs
includes
the
bleached,
porous
upper

member
of
the
Lyons
sandstone
in
the
Garden
of
the
Gods
(Siddoway
et
al.,
2013).

The
three
other
potential
sources
of
hydrocarbons
in
the
vicinity
of
the
Front

Range
are
carbonates
of
the
Upper
Paleozoic
Era
(Manitou
and
Hardscrabble
Devonian

limestones),
dark
marine
shales
of
the
Pennsylvanian
Period
(Glen
Eyrie
shale),
and

18

Cretaceous
Interior
Seaway
shales
and
limestones
(Niobrara
Formation,
Benton
Group,

and
Pierre
Shale).

These
formations
are
source
rocks
for
economically
significant

petroleum
reservoirs
in
Colorado,
such
as
the
Denver
and
Piceance
basins
(Figure
11).

The
hydrocarbon
source
rocks
feeding
these
basins
are
Graneros
Shale,
Greenhorn

Limestone,
Carlisle
Shale,
and
Pierre
Shale,
deposited
in
the
Cretaceous
Interior
Seaway

(Clayton
and
Swetland,
1980)
and
the
Pennsylvanian
Minturn
and
Phosphoria

Formations
(Glen
Eyrie
shale
and
Fountain
Formation
correlatives)
that
accumulated
in

tectonic
basins
and
marginal
marine
settings
during
the
ARMO
(Lillis
et
al.,
2003).

Within
Laramide
structures
of
the
broader
region,
evidence
of
large-‐scale

hydrocarbon
migration
comes
from
patterns
of
bleaching/discoloration
of
sandstones

involved
in
Laramide-‐derived
monoclines.

In
Utah,
bleaching
is
so
great
that
it
suggests

the
development
of
‘supergiant’
hydrocarbon
reservoirs
during
the
Paleogene
Period

(Beitler
et
al.,
2003).

This
claim
is
based
on
extensive
bleaching
in
the
Jurassic
Navajo

Sandstone
found
at
the
crest
of
monoclines
in
Utah.

Beitler
et
al.
(2003)
proposed
that

hydrocarbons
preferentially
migrated
through
inclined
bedding
of
the
aeolian

sandstone,
and
accumulated
in
the
crests
of
Laramide
monoclines
in
Utah.

When
the

crests
of
these
anticlines
were
eroded
during
the
Miocene,
the
reservoirs
were
breached

causing
hydrocarbons
to
seep
to
the
surface
and
into
the
atmosphere.

The
correlation

between
the
time
of
incision
into
the
reservoir
and
a
spike
in
Miocene
global
warming

suggests
that
these
reservoirs
were
so
large
that
they
may
have
greatly
affected
the

atmospheric
CO2
concentrations
contributing
to
Miocene
global
warming
(Beitler
et
al.,

2003).

19

M
E
T
H
O
D
S

Petrographic
analysis
of
Tava
sandstone
was
employed
to
determine
cement

variations,
deformation
banding,
veining,
grain
sorting,
and
fluid
inclusions.

Additionally,
gas
chromatography/mass
spectrometry
(GC/MS)
analyses
were

performed
on
four
samples
(KRCD-‐3,
PEA-‐1,
DUPLX
and
SLT-‐6)
to
establish
the

presence
of
hydrocarbons
and
to
characterize
the
geochemical
fingerprints
of

hydrocarbons
within
Tava
sandstone
samples.

These
four
samples
were
all
cobble
size

specimens
collected
directly
from
outcrop.

Duplicate
GC/MS
runs
were
performed
on

KRCD-‐3
and
SLT-‐6.

All
hand
samples
of
Tava
sandstone
were
collected
at
selected
sites

along
the
~80
km
of
the
Ute
Pass
Fault
and
were
processed
into
27mm
X
46mm
thin

sections
by
Texas
Petrographic
Services
INC.

A
small
number
of
samples
were
selected

for
polished
thin
sections
for
identification
of
opaque
phases
under
reflected
light.

Thin

sections
were
viewed
with
a
Leitz
Laborlux
12
Pol
and
a
Nikon
SMZ
1500
microscope

under
10X
–
400X
magnification.

Thin
sections
were
viewed
under
plane
and
cross-‐
polarized
light.

Thin
sections
were
also
viewed
under
surface
illumination
only
to

better
view
cement
variations.
This
mode
renders
grains
transparent
while
revealing

cements
in
their
authentic
color.

A
Mightex
LED
attached
to
the
Leitz
microscope

provided
reflected
light
used
to
view
polished
thin
sections.
Photomicrographs
were

taken
with
a
mounted
Nikon
EOS
Rebel
T4i
and
processed
with
Nikon
Rebel
Utility
on

an
iMac.

Activation
Laboratories
Ltd.
in
Ontario
Canada
performed
GC/MS
analyses
of

eleven
Tava
sandstone
samples
and
one
claystone
sample
(Figure
12).

The
eleven

samples
were
selected
based
on
degree
of
alteration
(redox),
the
two
end
members

being
PW611
(oxidized)
and
DUPLX
(reduced).

One
sample
of
Glen
Eyrie
shale
was
also

20

analyzed
to
create
a
baseline
hydrocarbon
concentration/composition
with
respect
to

Tava
sandstone.

These
tests
were
performed
using
an
Olympic-‐02
GC/MS
instrument

with
an
Agilent
7890A
GC
model
and
an
Agilent
5975C
MS
model.

All
samples

underwent
hydrocarbon
screening
capable
of
identifying
hydrocarbon
molecules
in

abundances
<
1ppm.

Geochemical
analysis
for
Whole
Rock
Oxides,
Minor
and
Trace

Elements
was
also
performed,
with
acquisition
of
64
trace
elements
as
well
as
oxides

versus
reduced
graphite.

On
the
basis
of
hydrocarbon
screen
results,
four
samples
were

selected
for
Diamondoid
Testing
with
a
High
Resolution
GC/MS
capable
of
identifying

hydrocarbon
classes
in
the
C12-‐C44
Carbon
Number
range
(Figure
13).

For
these

samples,
0.5g
of
crushed
rock
was
weighed
into
a
test
tube
and
1mL
of
2:1

hexane:methylene
chloride
was
added
at
a
weight
of
~0.835g.

The
samples
were
then

sonificated
for
30
minutes
and
then
centrifuged
for
1
minute
before
testing.

Geochemical
data
was
plotted
and
analyzed
using
Microsoft
Excel
and
IgPet
software

(RockWare,
INC.).

Samples
of
clay
minerals
were
analyzed
and
identified
using
X-‐ray
diffraction

(XRD),
using
the
X’pert
PRO
PANalytical
diffractometer
at
Colorado
College.

Six
Tava

samples
were
ground
into
fine
power
and
analyzed.

T
H
I
N

S
E
C
T
I
O
N

P
E
T
R
O
G
A
P
H
Y

Tava
sandstone
is
composed
of
fine
to
medium-‐grained
quartz
sandstone
hosting

infrequent
groupings
of
coarse
grain
to
pebble
size
quartz
clasts.

Fine
to
medium

grained
matrix
grains
range
from
0.20
–
0.33
mm,
while
coarse
gains
and
pebbles
range

from
1.0
–
4.0
mm.

Grain
sorting
is
very
unorganized,
but
there
are
zones
of
crude
grain

sorting
with
a
strand-‐like
pattern
appear
throughout
multiple
Tava
samples.

These

21

grain-‐sorting
patterns
may
have
formed
during
rapid
fluidized
injection
of
Tava

sandstone
during
seismicity
along
the
Ute
Pass
Fault
zone
associated
with
tectonism.

Hematite
cement
in
Tava
sandstone
formed
as
grain
coatings
from
the
chemical

breakdown
of
ferromagnesian
minerals
such
as
biotite,
which
is
found
as
clasts
in

multiple
Tava
samples.

Hematite
cement
gives
Tava
its
characteristic
red/maroon
hue

(Figure
4).

Alteration
of
Tava
sandstone
cement
is
observed
in
samples
containing

redox
patterns.

Redox
patterns
share
a
relationship
with
structural
overprinting
within

Tava
sandstone.

Redox
is
controlled
by
calcite
veins,
which
may
indicate
that
calcite

veins
formed
during
depressurization
of
Tava
dikes
following
rapid
injection
and
were

then
utilized
as
a
structural
conduit
for
fluid
migration.

Redox
patterns
appear
in
three
forms:
1)
linear
bands
controlled
by
veins,
2)

spherical
interruptions
nucleating
around
shale
clasts
or
at
the
termination/origin
of

calcite
veins,
3)
brecciated
angular
blocks
from
secondary
structural
overprinting
of

past
redox.

In
addition
to
redox
patterns,
further
evidence
for
hydrocarbons
within

Tava
sandstone
may
include
yellow
fluid
inclusions
containing
black
solid
centers.

Grain
Sorting

Multiple
Tava
samples
contain
sinuous
grain
flow
boundaries
that
separate

strands
of
coarse-‐grained
sandstone
from
strands
of
fine-‐grained
sandstone
(e.g.
DUPLX

and
MS-‐109)
(Figure
5).

These
strands
display
an
inter-‐penetrating
configuration
at
the

transition
between
grain
sizes
and
possess
crude
grain
sorting.

In
thin
section,
strands

vary
in
width
from
0.5-‐2.0
mm
and
are
observed
to
be
up
to
47
mm
long,
the
length
of
a

thin
section.

Strands
observed
in
thin
section
are
interpreted
to
mimic
larger
strands

observed
in
hand
samples.

Larger
strands
are
up
to
10
cm
long.

All
strands
possess

characteristic
tails
where
the
boundaries
taper
to
an
end.

22

One
particular
grain
sorting
fabric
is
substantiated
by
cement
variations
in
the

form
of
hematite
cement
‘flow
shadow.’

Sample
CRY-‐8
contains
a
quartz
pebble
floating

among
medium-‐grained
sand
matrix.

On
one
side
of
the
pebble
there
is
an
elongated

zone
of
hematite
cement
that
tapers
to
a
point.

Accompanying
the
tapered
hematite

cement
patch
is
a
parallel
funnel
shaped
grain
sorting
pattern
20
mm
away,
also

containing
hematite
cement.

All
other
cement
in
the
vicinity
is
quartz.

This
sample

suggests
that
fluid
migration
preferentially
followed
crude
grain
sorting.

Cement

Tava
sandstone
cement
varies
between
hematite,
quartz,
and
carbonate
(Dockal,

2005;
Harms,
1965;
Kost,
1984)
(Figure
4).

Distinctive
red
and
white
redox
patterns

within
Tava
sandstone
arise
from
variations
in
cement
(red=hematite,
clear=quartz)

and
accompanying
grain
sorting
and/or
fracture
networks.

Furthermore,
limonite

(FeO[OH]ŸH2O)
is
observed
primarily
in
conjunction
with
bleached
zones.

Deformation
Bands
at
Microscopic
Scale

Brittle
deformation
differs
from
veining
due
to
the
presence
of
cataclasite
and

brecciation.

Deformation
bands
contain
angular
clasts
within
a
matrix
of
clay.

Deformation
bands
are
most
prevalent
in
sample
SLT-‐2
where
they
reach
widths
of
3

mm
and
offset
redox
patterns
(Figure
6).

The
offsetting
of
redox
patterns
indicates
that

deformation
banding
post-‐dates
the
formation
of
redox
patterning.

Fluid
Inclusions

Tava
thin
sections
show
an
abundance
of
yellow
colored
fluid
inclusions.

Fluid

inclusions
appear
to
be
secondary
in
nature,
as
they
follow
linear
curvo-‐planar
healed

23

fractures
within
quartz
grains.

Fluid
inclusions
are
primarily
limited
to
one
single
grain

but
are
sometimes
observed
bridging
multiple
grains.

Tava
fluid
inclusions
are

observed
in
many
shapes
and
sizes,
but
are
primarily
found
as
spheres
ranging
between

1-‐2
μm
in
diameter.

Other
forms
include
ellipsoidal,
cylindrical,
and
a
highly
intricate

snowflake-‐like
pattern
that
can
be
up
to
10
μm
in
size.

Quartz
and
Calcite
Veins

Quartz
and
calcite
veins
are
observed
among
samples
along
the
~80
km
of
the

Ute
Pass
Fault.

Veins
are
observed
in
Tava
sandstone
samples
with
and
without
redox

patterns.

Veins
follow
inter-‐grain
interstices
and
are
discontinuous
along
their
length

(Figure
8).

In
many
instances,
veins
control
the
shape
and
distribution
of
redox

patterns.

From
this,
it
is
interpreted
that
veins
formed
within
preferential
low-‐pressure

dilation
bands
and
in
close
association
with
the
migration
of
reducing
fluids.

Reducing

fluids
preferentially
flowed
through
the
veins,
which
served
as
structural
conduits.

• Sample
CHR-‐9
contains
spherical
patterning
controlled
by
multiple
crosscutting

veins.

Spherical
red
hematite
cement
is
only
present
at
vein
intersections,
while
the

remaining
cement
is
clear
to
white.

Assuming
that
hematite
cement
is
primary,
vein

intersections
became
seals
to
fluid
migration,
therefore
allowing
for
the

preservation
of
hematite
(Figure
8).

• Sample
CHR-‐1
contains
spherical
cement
patterning,
but
unlike
CHR-‐9,
there
is
only

one
solitary
calcite
vein.

The
one
bleached
sphere
in
sample
CHR-‐1
occurs
at
the

termination/origin
of
the
calcite
vein
and
exhibits
a
teardrop
shape
following
the

trend
of
the
vein
(Figure
8).

• Sample
PINE-‐1
exhibits
angular
redox
patterning,
and
contains
multiple
crosscutting

vein
relationships,
however,
unlike
in
Sample
CHR-‐9,
red
hematite
cement
exists

24

only
in
areas
without
veining;
that
is,
veins
contain
clear-‐white-‐tan
cement,
while

the
surrounding,
vein-‐free
cement
is
pink-‐red
(Figure
8).

• Sample
110-‐5A
contains
one
calcite
vein
with
a
5
mm
wide
bleached
zone
on
either

side.

The
calcite
vein
is
up
to
2
mm
wide
and
pops
in
and
out
of
existence.

Limonite

is
closely
associated
with
the
bleached
zone
and
calcite
vein.

From
this,
calcite
and

limonite
may
be
reconstituted
calcium
and
iron
that
were
precipitated
out
of

solution
during
the
migration
of
reducing
fluids.

Furthermore,
the
calcite
vein

clearly
crosscuts
crude
grain
sorting
in
this
sample
indicating
that
calcite
veins
take

precedence
over
grain
sorting
as
a
fluid
conduit
when
observed
together
(Figure
8).

• Sample
SLT-‐3
contains
two
quartz
veins
that
run
parallel
to
one
another,
although

one
of
the
veins
has
an
indention
towards
the
opposite
vein.

The
vein
indention

correlates
precisely
with
the
separation
of
two
zones
of
hematite
cement,
which

appear
to
have
been
molded
matching
the
quartz
veins.

This
indicates
that
the
veins

serve
as
structural
conduits
for
the
migration
of
reducing
fluids
(Figure
8).

Fluid
Flow
Controls

• While
grain
sorting
in
sample
CRY-‐8
serves
as
the
main
fluid
migration
conduit,

sample
110-‐5A
suggests
that
calcite
veins
are
more
permeable
fluid
pathways

than
grain
sorting.

• Sample
PINE-‐1
shows
that
deformation
bands
offset
redox
patterns
indicating

that
deformation
banding
post-‐dates
the
migration
of
reducing
fluids.

Therefore

deformation
bands
have
not
served
as
a
structural
conduit
for
the
migration
of

reducing
fluids
within
Tava
sandstone.

• The
calcite
vein
in
sample
110-‐5A
proves
that
veins
are
the
most
prominent
fluid

migration
pathways
in
Tava
sandstone.

25

G
E
O
C
H
E
M
I
C
A
L

R
E
S
U
L
T
S

Major
Oxides

Other
than
one
shale
sample,
Tava
sandstone
is
mature
quartz
arenite
with

quartz
contents
ranging
from
90-‐97%
and
Fe2O3

(hematite)
compositions
ranging
from

<0.01
-‐
6.36%.

To
determine
the
oxidation
state
of
Tava
sandstone
samples,
ratios
of

ferric
iron
(Fe2O3)
to
ferrous
iron
(FeO)
were
determined.

Ratios
less
than
0.5
are

reduced
(SLT-‐6,
CHR-‐1,
KRCD-‐3,
DUPLX),
while
ratios
above
0.5
are
oxidized
(PW611,

TC-‐1,
PEA-‐1,
SLT-‐5,
SH
324-‐VE,
IM-‐126)
(Figure
14).

Reduced
samples
contain
lower

total
iron
concentrations
than
oxidized
samples,
with
averages
of
0.71%
(reduced)
and

2.07%
(oxidized).

Furthermore,
reduced
samples
contain
positive
anomalies
of
boron

compared
to
oxidized
samples
with
averages
of
33.25
ppm
boron
(reduced)
and
16.6

ppm
boron
(oxidized)
(Table
1).

For
closer
examination,
Tava
sandstone
samples
are
divided
into
four
categories:

red
(PW611,
PEA-‐1,
TC-‐1),
mottled
(SLT-‐5,
CHR-‐1,
KRCD-‐3),
bleached
(SLT-‐6,
DUPLX,

SH
324-‐VE),
and
shale
(IM-‐126).

Red
Tava
samples
contain
the
most
hematite;

especially
sample
PW611
with
6.36%,
while
mottled
and
bleached
samples
contain

much
less
between
0.92
-‐
<0.01%.

The
shale
rich
Tava
sample,
IM-‐126,
contains

53.57%
quartz,
15.75%
Al2O3,
and
2.09%
Fe2O3,
and
is
a
rare
occurrence
in
Tava

sandstone
outcrops.

All
other
major
oxides
in
Tava
sandstone
samples,
including
FeO,

MnO,
MgO,
CaO,
Na2O,
K2O,
TiO2,
and
P2O5,
remain
quite
constant
throughout
all

categories.

IM-‐126,
however,
has
much
more
major
oxide
concentrations
than
all
other

Tava
sandstone
samples.

26

Trace
Elements

Barium
is
the
most
abundant
trace
element
in
Tava
sandstone,
ranging
between

73
to
421
ppm
(Table
2).

Bleached
Tava
samples
contain
the
most
barium
with
207,

193,
and
116
ppm.

Sample
PW611
(oxidized)
contains
the
least
barium
with
only
73

ppm.

Red
Tava
samples
are
enriched
in
chromium
and
zirconium
compared
to
mottled

and
white
Tava
samples.

Sample
IM-‐126,
the
shale
rich
sample,
contains
the
most
trace

elements
in
general,
especially
Rubidium
(261ppm),
Vanadium
(83ppm),
Chromium

(89ppm),
Zirconium
(86ppm),
and
Barium
(90ppm).

Hydrocarbons

Preliminary
hydrocarbon
screening
revealed
the
qualitative
presence
of

hydrocarbons
in
samples
PEA-‐1,
SLT-‐5,
SLT-‐6,
DUPLX,
and
GE700
(Glen
Eyrie
shale)

(Table
1).

From
this,
samples
PEA-‐1
(qualitative),
KRCD-‐3
(quantitative),
SLT-‐6

(quantitative),
and
DUPLX
(quantitative)
were
selected
for
gas
chromatography
and

mass
spectrometry
diamondoid
analysis
(Table
3).

These
four
samples
collectively

span
the
full
spectrum
of
oxidation
states
for
Tava
sandstone
with
ferric/ferrous
ratios:

PEA-‐1
=
1.09,
SLT-‐6
=
0.46,
KRCD-‐3
=
<0.01,
and
DUPLX
=
<0.01.

Furthermore,
PEA-‐1

does
not
possess
any
redox
bleaching
patterns,
while
all
other
samples
do,
and
KRCD-‐3

did
not
register
on
the
preliminary
hydrocarbon
screening
but
proved
positive
for

hydrocarbons
with
diamondoid
analysis.

Along
with
Tava
sandstone,
a
sample
of
Glen
Eyrie
shale
(qualitative)
from

Colorado
Springs
was
also
selected
for
Diamondoid
Analysis
to
serve
as
a
hydrocarbon

baseline
control
to
Tava
sandstone
results.

The
Glen
Eyrie
shale
is
made
up
of
a
series

of
incomplete
cyclotherms
composed
of
alternating
coaly
black
shales,
black-‐grey

sandstones,
and
marly
limestones.

Glen
Eyrie
shale
has
been
dated
to
the
early

27

Pennsylvanian
Period
from
its
location
beneath
the
arkose
Fountain
Formation
and

index
fossils
including
conodonts,
brachiopods,
and
bryozoans
(Chronic
and
Williams,

1978).

Currently,
no
known
studies
have
tested
the
hydrocarbon
potential
of
Glen
Eyrie

shale.

Diamondoid
analysis
confirmed
the
qualitative
presence
of
hydrocarbons
in
all

Tava
samples
as
well
as
Glen
Eyrie
shale.

All
samples
contain
n-‐alkanes,
but
only

samples
DUPLX,
and
SLT-‐6
revealed
hopanes,
steranes,
and
diamondoids
(Table
2).

All

hydrocarbons
are
composed
of
hydrogen
and
carbon
atoms,
but
are
categorized

depending
on
their
structure
and
bonds.

N-‐alkanes
are
simple
carbon
chains
with

single
bonds
to
hydrogen.

The
carbon
number
of
an
n-‐alkane
identifies
how
many

carbon
atoms
make
up
the
carbon
chain.

Hopanes
and
steranes
are
comprised
of

carbon
rings
with
both
single
and
double
bonds
to
hydrogen.

Carotenoids
are
chains
of

40
carbon
atoms
that
are
produced
by
plants
and
cannot
be
made
by
animals.

• Glen
Eyrie
shale
is
composed
of
n-‐alkanes
between
n-‐C12
through
n-‐C27
with

one
peak
at
n-‐C16
that
tails
off
to
n-‐C24.

• Sample
KRCD-‐3
contains
n-‐alkanes
n-‐C15,
n-‐C17,
and
n-‐C18
-‐
C28.

KRCD-‐3

shows
a
much
smaller
peak
than
Glen
Eyrie
at
n-‐C21
that
tails
off
on
either
side

to
n-‐C19
and
n-‐C23.

Sample
KRCD-‐3
did
not
register
on
the
initial
hydrocarbon

screening,
and
yet
it
revealed
minor
traces
of
hydrocarbons
upon
diamondoid

analysis.

• Sample
PEA-‐1
contains
n-‐alkanes
n-‐C13
–
C16,
n-‐C18,
and
n-‐C22
–
C26.
Sample

PEA-‐1
does
not
exhibit
redox
patterns.

SLT-‐6
and
DUPLX
were
sampled
for
quantitative
Diamondoid
analysis,
which
revealed

the
presence
of
more
complex
and
stable
hydrocarbon
molecules.

28

• Sample
SLT-‐6
contains
n-‐C10,
n-‐C12,
n-‐C15,
and
n-‐C21
–
C26
with
a
peak
at
n-‐
C22
that
tails
down
to
n-‐C26.

Maximum
abundances
of
n-‐alkanes
are
n-‐C21,
C22,

and
C23
with
28,600
ppb,
32,900
ppb,
and
29,600
ppb
respectively.

Sample
SLT-‐
6
also
revealed
one
carotenoid,
trimethylpentadecane
(125
ppb).

• Sample
DUPLX
revealed
the
highest
quantity
of
hydrocarbons
out
of
any
sample.

DUPLX
contains
n-‐alkanes
n-‐C10,
n-‐C12,
and
n-‐C20
–
C31
with
a
lone
peak
at
n-‐
C20
and
an
asymmetrical
peak
at
n-‐C29
that
tails
off
at
n-‐C31.

DUPLX
contains

the
most
abundance
of
n-‐alkanes
at
n-‐C20
(223,500
ppb),
n-‐C29
(431,000
ppb),

n-‐C30
(379,000
ppb)
and
n-‐C31
(138,000
ppb).

Furthermore,
DUPLX
contains

an
abundance
of
hopanes,
steranes,
and
carotenoids.

Two
species
of
triaromatic

steranes
were
revealed,
both
chlorestane
(706
ppb)
and
ergostane
(2,860
ppb).

Two
species
of
hopanes
were
also
observed,
both
trisnorhopane
(302
ppb)
and

norhopane
(150
ppb).

Three
carotenoids
were
recorded
including

trimethylpentadecane
(137
ppb),
tetramethylnonadecane
(69.9
ppb),
and

squalane
(113
ppb).

X-‐Ray
Diffraction
(XRD)

Samples
IM-‐126
and
SH
324-‐VE
were
selected
for
x-‐ray
diffraction
analysis

because
they
contain
visible
green
shale
clasts
(Figure
15).

Sample
SP313
(relative
to

PEA-‐1)
was
also
selected.

Green-‐grey
in
color,
these
shale
clasts
are
dispersed

sporadically
and
can
be
up
to
1.0
cm
long
and
0.25
cm
wide.

Sample
IM-‐126
yielded

XRD
peaks
correlating
to
quartz,
illite,
and
dolomite,
while
sample
SH
324-‐VE
revealed

quartz,
montmorillonite,
and
graphite.

Sample
SP313
contains
quartz,
albite,
and

chlorite.

The
presence
of
graphite
in
sample
SH
324-‐VE
indicates
strong
carbon
content

within
the
shale.

29

D
I
S
C
U
S
S
I
O
N

The
presence
of
hydrocarbons
in
Tava
sandstone
indicates
that
the
Tava
dike

complex
has
served
as
a
fluid
migration
pathway
for
hydrocarbons.

For
this
to
occur

there
must
be
a
source
of
mature
hydrocarbons
in
the
Front
Range
as
well
as
tectonism

to
initiate
hydrocarbon
migration.

Tava
sandstone
is
Neoproterozoic
in
age
(~750
Ma),

and
because
of
this,
Tava
hydrocarbons
may
be
as
old
as
Neoproterozoic,
or
as
young
as

Cenozoic.

The
three
most
likely
sources
of
hydrocarbons
to
migrate
through
Tava

sandstone
include
in
situ
thermal
maturation
of
microbial
material
deposited
in
Tava

sandstone
during
original
deposition,
Paleozoic
limestones
and
shales
including
the

Manitou
Limestone
and
Glen
Eyrie
Shale,
or
Cretaceous
Interior
Seaway
limestones
and

shales
such
as
the
Niobrara
Formation
and
Pierre
Shale.

Tava
sandstone
has
been

subjected
to
~750
million
years
of
tectonism
and
alteration
from
movement
along
the

Ute
Pass
Fault
zone.

The
three
known
phases
of
tectonism
to
affect
the
Front
Range
are

extensional
rifting
during
the
Neoproterozoic
(~750
Ma),
Ancestral
Rocky
Mountain

Orogeny
(~300
Ma),
and
the
Laramide
Orogeny
(~60
Ma).

Processes
such
as
faulting,

erosion,
and
temperature
change
related
to
tectonic
exhumation
or
burial
could
have

caused
migration
or
leakage
of
hydrocarbons
during
any
of
these
stages.

Calcite
and
quartz
veins
are
the
primary
fluid
conduits
within
Tava
sandstone.

In
areas
of
strong
redox,
conjugate
veins
are
visibly
enhanced
by
redox
patterns.

The

formation
of
conjugate
veins
may
be
due
to
a
decompression
of
the
dike
margins

following
rapid,
pressurized
injection.

This
process
is
well
documented
in
sandstone

injectites
of
the
Viking
Graben
in
the
North
Sea
where
silica
has
been
precipitated
in

conjugate
veins
(Jonk
et
al.,
2005).

In
Tava
however,
calcite
vein
filling
may
have

formed
by
chemical
reactions
between
CO2
and
calcium
during
secondary
migration
of

30

reducing
fluids
through
primary
conjugate
deformation
bands
(Ehrlich
and
Newman,

2009).

Cross
cutting
relationships
in
sample
PINE-‐1
indicate
that
a
secondary
phase
of

deformation
bands
formed
within
Tava
sandstone
following
the
migration
of
reducing

fluids.

Since
the
last
tectonism
to
affect
Tava
sandstone
was
the
Laramide
Orogeny,
this

implies
that
redox,
and
therefore
hydrocarbon
migration,
must
have
occurred
prior
to

the
Laramide
Orogeny
(~60
Ma).

This
also
rules
out
all
hydrocarbon
source
rocks

younger
than
~60
Ma
as
the
source
of
hydrocarbons
in
Tava
sandstone.

The
presence
of
n-‐alkanes
in
the
ten
Tava
sandstone
samples
offers
possible

evidence
that
regional
hydrocarbon
migration
has
occurred
along
the
Front
Range
prior

to
the
Laramide
Orogeny
according
to
the
following
rationale.

N-‐alkanes
are
highly

susceptible
to
biodegradation,
so
n-‐alkanes
in
Tava
sandstone
are
likely
from
a

Paleozoic-‐Mesozoic
regional
hydrocarbon
source
rock.

The
highest
amounts
of
n-‐
alkanes
observed
in
Tava
sandstone
are
n-‐C29-‐31
at
431,000,
379,000,
and
138,000

ppb,
respectively,
within
sample
DUPLX.

The
abundance
of
these
larger
n-‐alkanes
is

indicative
of
terrestrial
plant
wax
input.

However,
it
should
be
noted
that

biodegradation
would
preferentially
attenuate
smaller
n-‐alkanes,
which
is
noticed
in

Tava
samples.

Disregarding
a
strong
influence
from
biodegradation,
the
abundance
of

large
n-‐alkanes
further
narrows
the
source
of
Tava
hydrocarbons
to
post
Ordovician

(~450
Ma).

This
is
based
on
the
fact
that
terrestrial
plants
did
not
exist
until
the
Late

Ordovician.

This
further
limits
the
remaining
hydrocarbon
source
rocks
in
the
Front

Range
to
Hardscrabble
Limestone,
Glen
Eyrie
Shale,
Niobrara
Formation,
and
Pierre

Shale.

GC/MS
on
oil
samples
from
the
Florence
Oil
Field
in
Cañon
City,
Colorado

indicate
that
the
Sharon
Springs
member
of
the
Pierre
Shale
is
the
source
for
the

31

Florence
field
(Lillis
et
al.,
1998).

N-‐alkanes
within
a
sample
directly
taken
from
the
oil

field
indicate
a
peak
at
n-‐C15
that
trails
to
n-‐C31.

Tava
sandstone
and
the
Sharon

Springs
member
of
the
Pierre
Shale
share
mutual
maximum
n-‐alkanes
at
n-‐C31

potentially
indicating
a
relationship.

Tava
and
Glen
Eyrie
hydrocarbons
share
similar
maximum
n-‐Alkanes
(n-‐C27
for

Glen
Eyrie
and
n-‐C31
for
Tava).

The
minimum
n-‐Alkanes
are
n-‐C10
for
Tava
and
n-‐C12

for
Glen
Eyrie.

This
difference
in
minimum
n-‐Alkanes
can
be
explained
by
preferential

biodegradation
patterns
due
to
different
surface
exposure
periods
for
the
two
samples.

Furthermore,
biodegradation
can
explain
the
attenuated
peaks
shown
in
the

chromatogram
for
Tava
sandstone.

The
high
abundances
of
boron
and
barium
in
Tava
samples
containing
redox
are

presumably
caused
by
hydrocarbon-‐bearing
reservoir
brines.

Brines
are
known
to

carry
in
solution
excess
amounts
of
boron
and
incompatible
elements
such
as
barium.

I

propose
that
reservoir
brine
from
either
the
Denver
Basin
or
the
Florence
Oil
Field
has

introduced
hydrocarbons
into
Tava
sandstone,
therefore
leading
to
redox,
as
well
as
an

increase
in
boron
and
barium.

Brines
carrying
hydrocarbons
have
low
density
and

therefore
rise
to
the
surface
through
any
structural
or
stratigraphic
conduit
available.

These
brines
presumably
flowed
through
the
Ute
Pass
Fault
zone
and
came
into
contact

with
Tava
sandstone
during
their
upward
migration.

Sample
PEA-‐1
(dark
brown
in
color)
contains
hydrocarbons
but
has
no
redox

indicating
that
hydrocarbons
and
redox
are
not
necessarily
associated.

Because
of
this,

no
less
than
two
sources
of
hydrocarbons
must
be
contained
within
Tava
sandstone.

For
PEA-‐1
to
contain
hydrocarbons
but
lack
redox
implies
that
no
secondary
migration

of
hydrocarbons
has
occurred
within
PEA-‐1
to
initiate
redox.

From
this,
I
propose
that

PEA-‐1
contains
original
Neoproterozoic
hydrocarbons
that
matured
in
situ
within
Tava

32

sandstone
during
down-‐faulting
of
Pikes
Peak
Granite
following
the
formation
of
Tava

sandstone
injectites.

A
potential
source
of
in
situ
hydrocarbon
maturation
within
Tava
sandstone
is

randomly
dispersed
green
shale
clasts
(Figure
15).

X-‐ray
diffraction
on
the
shale
clasts

reveals
the
presence
of
graphite
(SH
324-‐VE),
indicating
carbon
content
within
the

shale.

Most
shale
clasts
are
green
in
color,
however
black
shale
clasts
are
observed
as

well.

A
bleached
sphere
commonly
surrounds
black
shale
clasts.

This
may
indicate
that

black
shale
clasts
have
thermally
generated
hydrocarbons
that
are
responsible
for
the

reducing
conditions
that
arose
in
the
surrounding
halo.

One
outcrop
of
green
shale
(IM-‐
126)
hosted
in
Pikes
Peak
Granite
is
located
near
sample
SLT-‐6.

This
may
explain
the

abundance
of
shale
clasts
and
hydrocarbons
within
SLT-‐6.

Aside
from
thermal
maturation,
green
shale
clasts
may
have
produced

hydrocarbons
by
a
process
known
as
microbial
methanogenesis.

The
origins
of
calcite

veins
in
Tava
sandstone
may
be
associated
with
this
same
process.

Microbial

methanogenesis
is
a
process
by
which
microbes,
known
as
methanogens,
convert

carbon
dioxide
and
hydrogen
into
methane
and
water
(Budai
et
al.,
2002).

Methane/water
fluids
created
during
microbial
methanogenesis
are
reducing
fluids

capable
of
bleaching
sandstone.

Microbial
methanogenesis
requires
the
infiltration
of

microbial
bearing
fluids
into
an
organic
carbon-‐rich
formation.

Possible
sources
of

carbon
within
Tava
sandstone
are
the
green
shale
clasts,
determined
in
one
sample
to

contain
graphite.

Potential
times
of
fluid
infiltration
that
could
have
provided

methanogens
into
Tava
sandstone
coincide
with
tectonism
along
the
Front
Range
(i.e.

Neoproterozoic
rifting,
Pennsylvanian
ARMO,
or
Cretaceous-‐Paleogene
Laramide

orogeny).

AlecLeeSeniorThesis

Recommended

Recommended

More Related Content

Similar to AlecLeeSeniorThesis

Similar to AlecLeeSeniorThesis (20)

AlecLeeSeniorThesis