Chemical characteristics of Gulf Coast lignites


Tewalt, S.J.

Gulf Coast Lignite Geology: 201-210

1987


CHEMICAL
CHARACTERISTICS
OF
GULF
COAST
LIGNITES
Susan
J.
Tewalt
Railroad
Commission
of
Texas
P.O.
Drawer
12967
Austin,
TX
78711
Abstract
Depositional
environments
for
Gulf
Coast
lignite-bearing
units
-
the
Wilcox,
Claiborne,
and
Jackson
Groups
-
hove
been
extensively
studied.
Chemical
characteristics
of
lignites
in
these
units
have
been
related
to
the
interpreted
depositional
environment.
Based
on
increases
in
moisture
contents,
a
decrease
in
lignite
rank
is
observed
from
west
to
east
in
the
Gulf
Coast
states.
Sulfur
contents
are
determined
by
nearness
to
marine
influences
and
ash
contents
reflect
proximity
to
sediment
sources.
Claiborne
Group
lignites
in
Arkansas
and
Mississippi
have
higher
hydrogen/carbon
ratios
than
lignites
in
Texas
and
Louisiana,
and
probably
contain
more
sapropelic
material.
Introduction
Lignite
seams
occur
in
the
Gulf
Coast
region
within
the
Wilcox,
Claiborne,
and
Jackson
Groups
of
Tertiary
age.
The
stratigrophic
relationships
between
these
units
are
shown
in
Figure
1.
Williamson
(this
volume)
depicts
the
areal
distribution
of
these
three
Groups
in
the
Gulf
Coast
region.
The
variable
chemical
characteristics
of
Gulf
Coast
lignites,
which
play
an
important
role
in
their
utilization
for
electric
power,
result
from
physicochemical
processes
ongoing
during
peat
deposition
and
subsequent
coalification.
Later
epigenetic
alteration
also
contributes
to
chemical
variability.
The
environments
of
deposition,
which
largely
determine
peat
formation
and
lignite
quality,
have
been
inferred
from
extensive
studies
of
these
stratigraphic
units
by
many
authors.
This
paper
addresses
the
general
chemical
characteristics
of
lignites
in
Texas
(TX),
Louisiana
(LA),
Arkansas
(AR),
and
Mississippi
(MS)
with
respect
to
depositional
environment.
A
brief
comparison
of
available
data
for
proximate,
ultimate,
forms
of
sulfur,
and
ash
analyses
is
presented.
Chemical
analyses
of
Gulf
Coast
lignites
outside
Texas
were
kindly
provided
to
the
author
by
Phillips
Coal
Company.
201
Depositional
Environments
Wilcox
Grou
The
Wilcox
Group
is
the
most
significant
lignite-bearing
unit
in
the
Gulf
Coast
region.
In
Texas,
lignites
of
the
Wilcox
were
deposited
in
fluvial,
deltaic,
and
lagoonal
environments,
with
deposition
becoming
less
fluvial
and
more
marine
from
northeast
to
southwest
Texas
(Kaiser
et
al,
1980).
Recent
studies (Kai
ser
et al,
1986;
Breyer,
this
volume)
provide
different
interpretations
of
sedimentation
for
Wilcox
lignites
in
the
Sabine
Uplift
area
of
East
Texas.
Kaiser
et
al
(1986)
believe
that
the
regional
setting is
fluvial,
whereas
Breyer
(this
volume)
infers
a
tidal
origin
for
sands
associated
with
lignites
currently
being
mined.
In
Louisiana.
most
investigations
have
emphasized
the
lower
Wilcox
Group
of
Paleocene-Eocene
age,
which
includes
the
Chemard
Lake
lignite
interval.
Lignite
seams
in
the
lower
Wilcox
are
thought
to
be
fluvial/deltaic,
whereas
upper
Wilcox
lignites
are
interpreted
to
be
more
lagoonal/deltaic
in origin
(Coates
et
al,
1980).
Lower
and
middle
Wilcox
lignites
are
also
important
in
Arkansas,
where
seams
are
lenticular
and
the
environment
of deposition
is
inferred
to
be
mostly
fluvial
(Prior
et
ol,
1985)•
The
stratigraphy
of the
Wilcox
Group
in
Mississippi
is
complex.
Sediments
are
mostly
non-marine
in the north,
but
become
more
marine
southward
and
interfinger with
marine
equivalents
in
Alabama.
Small,
stocked
lignite deposits are
characteristic of
the
Wilcox
in Mississippi
(Williamson,
this
volume).
Claiborne
Group
Claiborne
lignites in
Texas
occur
mainly
within
the
Yegua
Formation
(Fig.
1).
Lignites
ore
most
common
in
the
middle
two-thirds
of
the
Yegua
and
were
deposited
in
fluvial/deltaic
environments
(Kaiser
et
al,
1980).
In
Louisiana,
the
Claiborne
Group
is
void
of
significant
lignite
occurrence.
However,
lignites
do
occur
in
the
Cockfield
Formation
(a
Yegua
equivalent)
in
Arkansas
and
Mississippi
(Luppens,
1978).
Claiborne
lignite
seams
in
Arkansas
are
lenticular
and
are
thought
to
have
been
deposited
in
deltaic
to
near
shallow
marine
environments.
In
Mississippi,
Claiborne
lignites
were
similarly
deposited
and
are
not
considered
economically
attractive.
Jackson
Grou
T
exas
is
the
only
state with significant li
g
nite
resources
in
the
Jackson
G
roup
,
which
occur
primarily within the
Manning
and
Wellborn
Formations.
Sediments
from
deltaic,
strandplain/lagoonal,
and
fluvial
environments
for
ore
present
in
the
Jackson
Group.
In
Ea
st
Texas,
Jackson
lignites
m
extensively
on
foundered
delta
lobe
s. StrandPlain/lagoonal
sy
the
stems
were
sites
of
lignit
e
formation
in
South
Texas.
In
the
other
Gulf
Coast
s
t
ates,
Jackson
Gro
u
p
sediments
are
la
r
g
el
y
transgressive,
although
lignites
of
minor
importance
are
known
.
202
SYSTEM
GROUP
TX
SIGNIFICANT
LIGNITE-BEARING
UNITS
LA
AR
MS
MANNING
JACKSON
WELLBORN
YEGUA
COCKFIELD
--
KOSCUISKO
EOCENE
CLAIBORNE
CALVERT
BLUFF
SABINETOWN
PENDLETON
MARTHAVILLE
UNDIV.
HATCHETIGBEE
TUSCAHOMA
NANAFALIA
PALEOCENE
WILCOX
Figure
1.
Generalized
stratigraphic
column.
Chemical
Characteristics
Lignite
Quality
and
Rank
Chemical
data
for
Texas
lignite
presented
in
this
paper
may
represent
a
wider
geographic
sampling
than
data
for
other
Gulf
Coast
states
and
may
cover
a
more
heterogeneous
mix
of
depositional
environments.
Data
for
the
Texas
Wilcox
Group
include
both
fluvial
and
deltaic
depositional
environments,
but
no
representatives
of
the
lagoonal
environment.
The
Jackson
Group
data
encompass
lignites
of
deltaic
and
lagoonal
deposition
in
Texas.
Lower
Wilcox
(fluvial/deltaic)
and
upper
Wilcox
(lagoonal/deltaic)
lignites
are
combined
in
the
Louisiana
state
averages.
Most
chemical
constituents
exhibit
a
range
of
values
within
each
depositional
environment.
The
ability
to
discern
differences
in
chemical
composition
decreases
as
more
environments
are
combined,
however
regional
trends
can
still
be
observed.
Table
1
lists
proximate
analysis
parameters
on
an
as-received
basis
by
state
for
the
Wilcox,
Claiborne,
and
Jackson.
An
apparent
decrease
in
lignite
rank
is
evident
from
west
to
east
in
the
Gulf
Coast
states;
this
is
based
on
increases
in
moisture
content
in
both
the
Wilcox
and
Claiborne
Groups.
Also,
moisture
values
increase
and
calorific
values
decrease
in
progressively
younger
lignites
with
similar
depositional
environments
(Luppens,
1978).
Ash
values
range
from
10
to
16
per
cent
in
the
Wilcox,
12
to
19
per
cent
in
the
Claiborne,
and
average
24
per
cent
in
the
Jackson.
Ash
contents
reflect
proximity
of
the
forming
peat
to
fluvial
sediment
sources.
Calorific
value
is
also
largely
controlled
by
ash
content
(Tewalt,
1986).
The
overage
calorific
values
in
Table
1
suggest
that
the
Jackson
Group
in
Texas
is
the
lowest
rank
lignite
in
the
Gulf
Coast
region.
However,
plotting
the
dry,
mineral-matter-free
hydrogen/carbon
and
oxygen/carbon
203
Table
1.
Proximate
anal
ses
as-received
basis
,
Gulf
Coast
li
nites.
WILCOX
GROUP
________
---CLAIBORNE
GROUP---
JK
TX
LA
AR
MS
TX
AR
MS
TX
Marx
s
$
r
C
n
32.51
3.47
29.23
0.10
684
35.06
2.30
11.18
0.07
67
35.85
3.79
28.45
0.11
108
43.16
2.89
13.68
0.07
122
35.62
5.66
29.03
0.16
32
36.13
2.74
14.39
0.08
38
41.46
2.86
20.43
0.07
108
35.46
8.41
43.88
0.24
328
VOL
MAT
%
x
s
r
c
n
27.77
3.25
25.70
0.12
647
27.08
1.63
11.23
0.06
67
24.95
2.36
16.08
0.09
108
23.24
1.82
11.82
0.08
122
26.06
3.23
16.60
0.12
32
30.61
3.26
17.25
0.11
38
28.99
2.77
18.50
0.10
108
23.31
4.16
41.36
0.18
252
FIXED
x
24.44
27.09
22.77
21.17
19.16
19.26
17.01
15.17
C
s
3.83
1.86
2.85
2.41
3.42
2.39
1.63
3.81
%
r
26.56
12.65
16.06
20.16
16.82
12.56
9.08
21.05
c
0.16
0.07
0.13
0.11
0.18
0.12
0.10
0.25
n
647
67
108
122
32
38
108
252
ASH
x
15.39
10.72
16.55
12.43
19.15
14.00
12.56
24.32
s
7.81
3.08
6.18
5.04
9.34
7.53
5.88
10.88
%
r
44.40
17.75
39.28
22.66
39.26
36.37
35.71
43.01
c
0.51
0.29
0.37
0.41
0.49
0.54
0.47
0.45
n
684
67
108
122
32
38
108
284
SULF
x
0.99
0.81
0.71
0.54
1.00
0.80
0.48
1.51
s
0.57
0.33
0.31
0.55
0.40
0.51
0.20
0.85
%
r
4.09
2.86
1.66
3.13
1.59
3.12
1.02
8.35
C
0.57
0.41
0.44
1.02
0.40
0.64
0.42
0.56
n
638
67
107
122
31
38
108
288
BTU
x
6460
6856
5786
5329
5753
6503
5806
4805
s
870
427
660
411
759
757
585
1060
r
7884
2947
4363
2192
3701
3676
3855
7515
C
0.13
0.06
0.11
0.08
0.13
0.12
0.10
0.22
n
644
67
108
122
31
38
108
288
x
=orithmetic
mean
s
=
standard
deviation
r
=
range
c
=coefficient
of
variation
(s/x)
n
=
number
of
analyses
r
atios
(Table
2)
on
a
graph
(Hunt, 19
79
)
in
dicates
that
the
Jackson
lignites
are
similar
to
the
Wilcox.
Claiborne
units
in
Arkansas
and
Mississippi
have
the
highest
h
ydrogen/carbon
ratios
(Table
2
and
Figure
2).
Coalification
increases
frrn
upper
right
to
lower
left
(following
the
arrows)
in
the
plot.
2014
73.9
1.67
6.8
0.02
15
74.8
72.7
75.0
2.28
1.49
1.86
13.1
8.8
23.7
0.03
0.02
0.02
37
92
225
6.1
6.7
6.8
6.2
0.50
0.31
0.42
0.42
2.0
1.4
3.8
2.9
0.09
0.05
0.06
0.07
15
37
92
201
Table
2.
Dry,
mineral-matter-free
parameters,
ratios
on
atomic
basis.
--CLAIBORNE
GROUP---
JK
TX
LA
AR
MS
TX
AR
MS
TX
WILCOX
GROUP
DMMF
x
73.6
74.6
74.0
72.9
C
s
3.13
1.53
4.24
2.00
%
r
36.7
6.3
21.8
13.5
c
0.04
0.02
0.06
0.03
n
223
41
39
102
DMMF
x
5.9
5.3
5.3
5.4
H
s
0.39
0.41
1.04
0.76
%
r
4.0
2.6
4.8
8.9
c
0.07
0.08
0.20
0.14
n
143
41
39
102
DMMF
x
20.6
18.5
19.4
20.3
21.1
17.2
21.3
20.6
0
s
2.97
1.46
4.69
2.09
3.2
2.48
1.74
2.24
%
r
25.3
7.5
25.5
15.9
16.3
14.8
11.3
31.8
c
0.14
0.08
0.24
0.10
0.15
0.14
0.08
0.11
n
222
41
39
102
15
37
92
225
H/C
x
1.00
0.89
0.89
0.92
1.03
1.12
1.16
1.03
0/C
x
0.21
0.19
0.20
0.21
0.21
0.17
0.22
0.21
x
=
arithmetic
mean
s
=
standard
deviation
r
=
range
c
=
coefficient
of
variation
(s/x)
n
=
number
of
analyses
1.4
1.2
H/C_
1.0
9
f
Ae
e
dh
c
ab
0.8
-
0.6
-
_
0.02
0.04
0.06
0.08
0.1
0.2
0.4
0.6
_
_
-0/C-1
.
.
1
.
Figure
2.
Atomic
H/C
and
0/C
plot
(after
Hunt,
1979);
a
=
LA
Wilcox,
b
=
AR
Wilcox,
c
=
MS
Wilcox,
d
=
TX
Wilcox,
e
=
TX
Claiborne,
f
=
AR
Claiborne,
g
=
MS
Claiborne,
h
.
TX
Jackson.
205
Concentrations
of
P205
are
low
in
all
states
and
units,
although
Wilcox
lignites
in
Arkansas
average
higher
because
nearly
20
per
cent
of
the
samples
hove
concentrations
of
P205
exceeding
one
per
cent.
The
Wilcox
Group
in
Texas
and
Louisiana
have
the
lowest
Si02
concentrations
(about
44
per
cent)
while
the
Jackson
Group
has
the
highest.
High
Si02
values
in
the
Jackson
are
attributed
to
volcanic
ash
constituents.
Jackson
lignites
also
have
the
lowest
Fe203,
CaO,
Mg0,
and
S03
averages.
High
Na20
concentrations
are
usually
indicative
of
more
marine
conditions
during
deposition.
The
Claiborne
and
Jackson
lignites
in
Texas
and
the
Wilcox
in
Louisiana
average
over
one
per
cent
Na20,
but
this
is
not
an
excessively
large
value.
Lagoonal
Jackson
Group
lignites
in
Texas
average
nearly
four
per
cent
Na20
(Tewalt,
1986).
Table
4.
Ash-oxide
analyses,
Gulf
Coast
lignites.
TX
WILCOX
LA
AR
GROUP
MS
--CLAIBORNE
TX
AR
GROUP--
MS
JK
TX
P205
x
0.07
0.09
0.35
0.07
0.06
0.08
0.07
0.05
s
0,04
0.07
0.67
0.09
0.02
0.07
0.04
0.03
r
0.71
0.33
2.09
0.55
0.05
0.25
0.18
0.29
c
0.57
0.78
1.91
1.29
0.33
0.88
0.57
0.60
n
274
36
69
102
17
35
77
213
S102
x
44.10
44.42
54.53
50.39
54.46
55.43
53.86
59.22
s
13.17
7.75
8.21
10.49
9.06
9.33
11.10
6.24
r
68.64
33.30
36.59
55.20
27.75
39.62
55.51
46.89
c
0.30
0.17
0.15
0.21
0.17
0.17
0.21
0.10
n
335
41
76
102
17
36
91
213
FE203
x
8.96
5.53
6.48
7.02
6.39
5.74
7.16
3.39
s
5.37
2.36
2.88
7.68
2.43
2.84
3.21
2.00
r
38.01
10.81
17.93
45.33
8.04
14.24
16.50
43.78
c
0.60
0.45
0.44
1.09
0.38
0.49
0.45
0.59
n
337
41
76
102
17
36
91
213
AL203
x
15.03
19.11
16.08
13.34
15.08
13.92
16.46
19.08
s
4.43
5.67
3.48
3.03
2.80
3.44
4.55
3.21
oe
r
25.22
22.32
20.94
15.64
10.25
15.46
21.15
20.59
c
0.29
0.30
0.22
0.23
0.18
0.25
0.28
0.17
n
337
41
76
102
17
36
91
213
T102
x
1.03
0.80
0.89
0.75
0.78
0.93
0.93
0.79
s
0.34
0.23
0.30
0.30
0.17
0.31
0.34
0.15
%
r
2,30
1.23
1.87
1.39
0.57
1.14
2.29
0.87
c
0
33
0.29
0.34
0.40
0.22
0.33
0.37
0.19
n
333
41
76
102
17
36
91
213
(table
continued
next
page)
Ash-oxide
concentrations
affect
ash-fusion
temperatures,
which
in
turn
determine
the
formation
of
slag
and
viscosity
of
ash
during
combustion.
Ash
fusion
temperatures
can
be
lowered
as
a
result
of:
1)
increase
in
the
silica/alumina
ratio,
2)
increases
in
Fe203
or
S03
content,
and
3)
compounds
formed
from
sodium,
potassium,
magnesium,
or
sulfur.
Table
5
207
Table
4.
Ash-oxide
anal
ses,
Gulf
Coast
li
nites
continued
.
WILCOX
GROUP
--CLAIBORNE
GROUP
--
JK
TX
LA
AR
MS
OW
x
11.91
12.95
8.73
14.34
s
6.12
4.41
4.20
5.91
%
r
45.50
20.86
16.62
25.02
c
0.51
0.34
0.48
0.41
n
337
41
76
102
MO
x
2.67
3.06
1.63
2.90
s
1.12
0.79
0.47
0.96
%
r
8.39
4.02
2.74
4.48
c
0.42
0.26
0.29
0.33
n
337
41
76
102
S03
x
11.77
9.58
6.96
7.91
s
6.14
3.00
3.35
4.17
%
r
30.82
13.86
20.05
21.42
c
0.52
0.31
0.48
0.53
n
336
41
76
102
K20
x
0.78
0.52
0.68
0.83
s
0.50
0.48
0.38
0.33
%
r
3.17
4.35
1.54
2.06
c
0.64
0.92
0.55
0.40
n
332
41
76
102
NA20
x
0.70
1.06
0.82
0.26
s
0.54
0.55
0.39
0.14
3.18
4.68
2.73
0.88
c
0.77
0.52
0.48
0.54
n
337
41
76
102
TX
AR
9.50
10.52
4.23
4.86
14.03
19.90
0.44
0.46
17
36
1.75
1.60
1.98
0.98
0.52
0.56
0.66
0.46
1.89
2.75
3.50
3.00
0.30
0.35
0.33
0.47
17
36
91
213
8.53
8.77
7.15
6.45
3.79
3.47
3.98
3.23
13.60
13.72
20.98
25.22
0.44
0.40
0.56
0.50
17
36
91
213
1.14
0.39
0.35
1.17
0.61
0.20
0.21
0.64
1.82
0.68
1.43
2.29
0.53
0.51
0.60
0.55
17
36
91
213
1.22
0.30
0.34
1.72
0.39
0.11
0.29
1.54
1.43
0.46
3.00
6.00
0.32
0.37
0.85
0.89
17
36
91
213
MS
TX
9.97
6.54
3.74
2.64
16.86
21.83
0.37
0.40
91
213
x=orithmetic
mean
s
=
standard
deviation
r
=
range
c=coefficient
of
variation
(s/x)
n
=
number
of
analyses
presents
fusion
temperatures
(measured
in
a
reducing
atmosphere),
silic
a
/
a
lumina
and
base/acid
ratios,
plus
Hardgrove
grindability
indices
for
Gulf
Coast
lignites.
All
of
the
initial
deformation
temperatures
exceed
2,100
degrees
F,
which
is significantl
y
hi
g
her
than
deformation
tem
peratures
of
lignites
from
North
Dakota
(Luppens,
1978).
Base/acid
ratios
are
generally
similar,
although
lowest
in
the
Jackson
Group
because
of
the
high
Si02
contents
(Dixon
et
al,
this
volume).
Hardgrove
grindobility
indices
ore
variable,
with
the
greatest
values
and
greatest
variability
in
the
Mississippi
Claiborne
lignites.
208
Table
5.
Ash-fusion
temperatures
(reducing
atmosphere,
degrees
F),
and
physical
characteristics,
Gulf
Coast
lignites.
----
WILCOX
GROUP
---CLAIBORNE
GROUP---
JK
TX
LA
AR
MS
TX
AR
MS
TX
INIT
x
2,138
2,182
2,284
2,204
2,149
2,273
2,321
2,116
DEF
s
131
80
151
97
64
150
168
123
min
1,742
2,039
1,920
1,940
2,039
2,110
2,048
1,870
max
2,910
2,444
2,732
2,732
2,282
2,650
2,732
2,560
n
268
41
74
103
14
37
93
25
SOFT
x
2,232
2,214
2,318
2,228
2,200
2,310
2,348
2,294
TEMP
s
130
78
145
98
68
151
161
173
min
1,746
2,057
1,950
1,949
2,093
2,138
2,084
1,950
max
2,800
2,462
2,732
2,732
2,363
2.700
2,732
2,660
n
265
41
74
103
14
37
93
25
HEMI
x
2,255
2,256
2,365
2,264
2,256
2,335
2,402
2,352
TEMP
s
145
82
144
105
73
147
150
183
min
1,751
2,075
2,000
2,012
2,183
2,156
2,120
1,980
max
2,700
2,516
2,732
2,732
2,426
2,700
2,732
2,600
n
201
41
74
103
14
37
93
25
FLUID
x
2,360
2,344
2,442
2,321
2,475
2,395
2,468
2,494
TEMP
s
183
105
151
119
96
173
141
158
min
1,778
2,156
2,060
2,093
2,372
2,192
2,183
2,150
max
2,800
2,588
2,932
2,732
2,687
2,700
2,732
2,750
n
262
41
74
103
14
37
93
25
SI/AL
x
3.19
2.59
3.64
3.94
3.78
4.26
3.77
3.35
s
1.44
0.90
0.97
1.22
1.16
1.47
2.08
0.57
min
0.90
1.05
2.07
2.04
2.20
2.44
1.44
1.84
max
27.44
5.20
8.45
9.43
6.67
9.62
9.12
5.83
n
335
41
76
103
17
37
89
213
B/A
x
0.48
0.39
0.29
0.43
0.29
0.28
0.30
0.18
s
0.29
0.17
0.14
0.25
0.08
0.12
0.15
0.07
min
0.11
0.16
0.06
0.11
0.17
0.04
0.04
0.07
max
2.88
1.06
0.75
1.59
0.47
0.43
0.88
1.12
n
330
41
76
102
17
37
91
213
HGI
x
59.9
70.8
64.6
85.2
86.8
79.2
91.6
78.1
s
11.3
11.9
14.9
17.2
18.0
12.0
27.9
18.9
n
70
40
66
103
14
36
101
27
INIT
DEF
=
initial
deformation
SOFT
TEMP
=
softening
temperature
HEMI
TEMP
=
hemispherical
temperature
FLUID
TEMP
=
fluid
temperature
SI/AL
=
silica/alumina
ratio
B/A
=
base/acid
ratio
HGI
=
Hardgrove
grindability
index
x
=
arithmetic
mean
s
=
standard
deviation
min
=
minimum
value
max
=
maximum
value
n
=
number
of
analyses
209
Chemical
characteristics
of
Gulf
Coast
lignites
can
be
related
to
the
interpreted
depositional
environments
of
the
Wilcox,
Claiborne,
and
Jackson
Groups.
Clearer
relationships
between
lignite
quality
and
depositional
setting
can
be
observed
on
less
regional
scales
and
further
studies
of
individual
lignite
deposits
may
provide
insight
to
the
patterns
of
chemical
variation
in
Gulf
Coast
lignites.
References
Breyer,
J.
A.
,
this
volume;
and
in
press,
A
tidal
origin
for
coarsening-upward
sequences
above
two
Wilcox
lignites
in
East
Texas:
Journal
of
the
Geological
Society
of
London,
v.
144.
Coates,
E.
J.,
Groat,
C.
G.
,
and
Hart,
G.
F.
,
1980,
Subsurface
Wilcox
lignite
in
west-central
Louisiana:
in
Gulf
Coast
Association
of
Geological
Societies
Transactions,
v.
30,
p.
309-332.
Dixon,
J.
B.,
Senkayi,
A.
L.
,
and
Hossner,
L.
R.
,
this
volume,
Mineralogy
of
surface-mined
lands
in
the
Gulf
Coast,
p.
198-208.
Hunt,
J.
M.,
1979,
Petroleum
geochemistry
and
geology:
San
Francisco,
W.
H.
Freeman,
617
p.
Kaiser,
W.
R.,
Ambrose,
M.
L.
,
Ayers,
W.
B.,
Jr.,
Blanchard,
P.
E.
Collins,
G.
F.,
Fogg,
G.
E.
,
Gower,
D.
L.
,
Ho,
C.
L.
,
Holland,
C.
S.,
Jackson,
M.
L.
W.,
Jones,
C.
M.,
Lewis,
A.
H.,
Macpherson,
G.
L.,
Mohan,
C.
A.
,
Mullin,
A.
H.
,
Prouty,
D.
A.,
Tewalt,
S.
J.,
and
Tweedy,
S.
W.,
1986,
Geology
and
ground-water
hydrology
of
deep-basin
lignite
in
the
Wilcox
Group
of
East
Texas:
The
University
of
Texas
of
Austin,
Bureau
of
Economic
Geology
Special
Publication,
182
p.
Kaiser,
W.
R.,
Ayers,
W.
B.
,
Jr.
,
and
La
Brie,
L.
W.
,
1980,
Lignite
resources
in
Texas:
The
University
of
Texas
at
Austin,
Bureau
of
Economic
Geology
Report
of
Investigations
No.
104,
52
p.
Luppens,
J.
A.,
1978,
Exploration
for
Gulf
Coast
U.S.
lignite
deposits:
their
distribution,
quality,
and
reserves,
in
Transactions,
Second
International
Coal
Exploration
Symposium:
Denver,
Colorado,
p.
195-210.
prior,
W.
L.,
Clardy,
B.
F.
,
and
Bober.
Q.
M.
,
1985,
Arkansas
lignite
investigations:
Arkansas
Geological
Commission
Information
Circular
28-C,
214
p.
Tewalt,
S.
J.,
1986,
Chemical
characterization
of
Texas
lignite:
The
University
of
Texas
at
Austin,
Bureau
of
Economic
Geology
Geological
Circular
86-1,
52
p.
Williamson,
D.
R.
,
this
volume;
and
also
1986,
Lignites
in
Alabama,
Arkansas,
and
Mississippi,
in
Finkelman,
R.
B.
and
Casagrande,
D.
J.,
ed.,
Geology
of
Gulf
Coast
lignites:
Environmental
and
Coal
Associates,
p.
115-125.
210