Environments of Deposition and Petroleum Geology of Tuscaloosa ...

The Ainoiicyn Association of Petroleum Cicologi^l^ Biiilciin
V.-LNo. 10(Oaobci iy.S7|. P, li2S-ll42, I7i"i^s..2 Tables
Environments of Deposition and Petroleum Geology of
Tuscaloosa Group (Upper Cretaceous), South Carlton and
Pollard Fields, Southwestern Alabama^
ERNEST A. MANCINI/ ROBERT M. MINK/ J. WAYNE PAYTON;
and BENNETT L. BEARDEN'
ABSTRACT
INTRODUCTION
In southwestern Alabama, the lower Tuscaloosa
Group (Upper Cretaceous) consists of two informally
defined units, the Massive and Pilot sand intervals. The
Massive sand interval accumulated principally as sands
in a wave-dominated, high-destructive delta system.
These sandstones are structureless, well sorted, micaceous,
locally fossiliferous, calcareous, glauconitic, fine
grained, and quartz rich, containing angular to subangular
quartz grains. The Massive sand interval unconf ormably
overlies fluvial-deltaic sediments of Lower
Cretaceous strata.
The Pilot sand interval, which overlies the Massive
sand interval, accumulated as shelf sands and clays during
a marine transgression. The sandstones are well
sorted, micaceous, fossiliferous, calcareous, glauconitic,
very fine to fine grained, and quartz rich, containing subangular
to subrounded quartz grains. The sandstones
appear massive but may be structureless as a result of
extensive bioturbation. Marine bivalves, such as
inoceramids, are present in the sandstones and claystones.
The Pilot sand interval is overlain by a marine claystone
(Marine shale) containing a diverse faunal assemblage
of macroinvertebrates, including ammonites,
inoceramids and other bivalves, and a rich microfossil
assemblage of planktonic foraminifera and calcareous
nannofossils. The Marine shale accumulated in an openmarine
shelf environment.
Petroleum traps in the Tuscaloosa are structural traps
involving salt anticlines (South Carlton field) and extensional
fault traps associated with salt movement (Pollard
field). Reservoir-grade porosity occurs in the Massive
and Pilot sandstone units as primary intergranular
porosity. Although Ibscaloosa marine claystones contain
significant amounts of organic carbon, these rocks
are thermally too immature to be the petroleum source
rocks for the Tuscaloosa crude oils in South Carlton and
Pollard fields.
©Copyright 1987. The American Association of Petroleum Geologists. All
rights reserved.
''Manuscript received, May 12,1986; accepted, April 20,1987.
Geological Survey of Alabama and University of Alabama, Tuscaloosa, Alabama
35486.
•'state Oil and Gas Board of Alabama, Tuscaloosa, Alabama 35486.
*42 Mayfair, Tuscaloosa, Alabama 35404.
1128
The first hydrocarbon discovery in the Tuscaloosa
Group (Upper Cretaceous) in Alabama was made in 1950
at South Carlton field, Clarke and Baldwin Counties
(Figure 1). In 1952, the Tuscaloosa was proven productive
at Pollard field, Escambia County, Alabama. To
date. South CarUon and Pollard fields have had a cumulative
production of more than 18 million bbl (2.86 X 10**
m^) of oil. Renewed interest in drilling wells for Tuscaloosa
prospects in Alabama should occur as a result of a
recent discovery north of Pollard field in Escambia
County, Alabama (Figure 1).
A key to exploring for Tuscaloosa hydrocarbons is an
understanding of the stratigraphic, structural, and paleoenvironmental
relationships in which the sandstones and
claystones accumulated. We describe the stratigraphic
and structural relationships associated with the Tuscaloosa
in the South Carhon and Pollard fields and interpret
the depositional environments for the sandstones
and claystones in the area of these two fields. An understanding
of the geologic factors that make South Carlton
and Pollard fields productive will help geologists formulate
petroleum exploration strategies in southwestern
Alabama.
STRUCTURAL SETTING
The major structural features in southwestern Alabama
are numerous salt domes and anticlines, the Wiggins
arch, the Mobile graben, and the regional peripheral
fault trend (Figure 1). Some of the more important salt
domes and anticlines include the Mcintosh and Klepac
piercement domes; the Chatom, Citronelle, and South
Carlton domes (the petroleum trap at South Carlton
field) (Figure 2); and the Hatchetigbee anticline (Moore,
1971; Wilson, 1975). The Wiggins arch, which extends
westward into Mississippi, is a Paleozoic basement high.
The north-south-trending Mobile graben is associated
with the easternmost extent of thick saU in the eastcentral
part of the northern Gulf Coast basin (Murray,
1961).
The regional peripheral fault trend is associated with
the updip limit of Jurassic Louann Salt deposition in the
Gulf of Mexico region (Moore, 1971; Martin, 1978). In
southwestern Alabama, the fault trend consists of a

Ernest A. Mancini et al 1129
EXPLANATION
Normal Fault
(hachures on downthrown side)
Salt Anticline or Basement Arth
Salt Dome or Uplift
Fields
Gilbertown
Little Mill Ci
upper Creticeoui
Lower Cretaceous
Jurassic
Recent Tuscaloosa Discovery
Well Permit Number
Line of Cross Section
SCALE
ilometers
Figure 1—Major structural features and location of lower Ibscaloosa oil fields in soutliwestern Alabama.
group of related fault systems, including the Pickens-
Gilbertown, West Bend, and PoUard-Foshee fault systems.
These faults are extensional features having
variable throws and lengths (Wilson, 1975). Displacements
of 200-1,000 ft (61-305 m) are evident in the Tuscaloosa
at depths of around 4,000-6,000 ft (1,220-1,830 m)
along this fault trend (Moore, 1971). The petroleum trap
at Pollard field is a faulted salt anticline along the Pollard
fault system (Figure 3).
STRATIGRAPHY
In the subsurface of southwestern Alabama, the Tliscaloosa
Group unconformably overlies Lower Cretaceous
terrigenous clastic deposits. Lower Cretaceous sedimentation
was principally fluvial-deltaic (Eaves, 1976).
Smith and Johnson (1887) first used the term "Tuscaloosa"
to describe surface sediments occurring between
Paleozoic rocks and the Cretaceous Eutaw Formation.
The unit was named for exposures along the Black Warrior
River and near the town of Tbscaloosa in Tliscaloosa
County, Alabama (Stephenson, 1926). Monroe et al
(1946) introduced a fourfold division for the Tbscaloosa,
which they designated as the Tbscaloosa Group. In
ascending order, the Tbscaloosa Group consisted of the
Cottondale, Eoline, Coker, and Gordo formations.
Drcnnen (1953) divided the Tbscaloosa into two formations
using the names "Coker" and "Gordo." The lower
formation, the Coker, consists of glauconitic crossbedded
sand interbedded with carbonaceous, laminated
clay (Eoline Member), and micaceous, cross-bedded
sand and purple, carbonaceous clay. The Gordo Formation
is composed of gravelly, cross-bedded sand and red,
purple, and/or gray-mottled clay. The Tbscaloosa sediments
in western Alabama, northeastern Mississippi,
and western Tennessee accumulated in a fluvial-deltaiccoastal
marine complex (Russell et al, 1980). In eastern
Alabama, the Gordo is poorly sorted, kaolinitic, arkosic
sand and the Coker consists of interbedded red and
green, mottled, kaolinitic clay (Reinhardt and Gibson,
1980). These deposits represent meandering stream,

1130 Deposition and Petroleum Geology of Tuscaloosa Group, Southwestern Alabama
• oil WELL
EXPLANATION
+ ABANDONIDOILWELL
^
^
DRY HOLE
SALTWATERDISP05ALWELL
ORIGINAL OIL-WATERCONTACT
IN THE PILOT SANDSTOME UNIT
269 WELLPERMITNUMBER
* JURASSICTESTWELL
Figure 2—Structure map of top of lower Tuscaloosa, South
Carlton field, Clarke and Baldwin Counties, Alabama.
point-bar, channel, and flood-plain sedimentation
(Reinhardt, 1980).
In the subsurface, the Tuscaloosa of Mississippi and
western Alabama has been divided into two units by
McGlothlin (1944): the lower Tuscaloosa—including the
Massive sand, Marine, and shale and sand units—and the
upper Tuscaloosa. Winter (1954) recognized three distinct
subsurface Tuscaloosa units in Pollard field. In
ascending order, these units are the lower Tuscaloosa,
including the Massive sand and the Pilot (Moye) sand,
the Marine shale (marine Tuscaloosa), and the upper Tuscaloosa,
including the Miller sand. We use the subsurface
stratigraphic nomenclature of Winter (1954) in this paper
(Figure 4).
The Massive sand interval of the lower Tuscaloosa
unconformably overlies Lower Cretaceous strata in the
subsurface of the study area (Figure 5). The Massive sand
interval expands downdip in coastal and offshore Alabama
and thins updip in Choctaw and Butler Counties
(Figures 6, 7). The Massive is more than 450 ft (137 m)
thick and includes, in ascending order, a basal sandstone
unit, an interbedded sandstone and claystone unit, and
an upper unit consisting predominately of massive sandstone
in the South Carlton and Pollard field area (Figure
5). The upper sandstone unit (Massive sandstone unit) is
up to 270 ft (82 m) thick in South Carlton field and 240 ft
(73 m) in Pollard field and consists of light gray to greenbrown,
micaceous, calcareous, locally fossiliferous,
glauconitic, very fine to fine grained, quartz-rich sandstone.
The Pilot sand interval of the lower Tbscaloosa overlies
the Massive sand interval. The Pilot sand interval attains
maximum thickness in Washington County and in South
Carlton and Pollard fields (Figure 8). The Pilot sand
thins in Choctaw County (Figure 6) and pinches out in
Butler County (Figure 7). The Pilot is more than 150 ft
(46 m) thick and includes a claystone unit and an upper
EXPLANATION
• OIL WELL
• ABANDONEDOILWELL
• PLUGQED AND ABANDONED DRY HOLE
A SALTWATEROISPOSALWELL
^ ^ ^ FAULT {hachures on downthrown side)
~~ —-ORIGINAL OIL-WATERCONTACT
IN PILOT SANDSTONE UNIT
40O WELL PERMIT NUMBER
CONTOUR INTERVAL 20 FEET
1/2 MILE
1/2 KILOMETER
Figure 3—Structure map of top of lower Tuscaloosa, Pollard field, Escambia County, Alabama.

Ernest A. Mancini et al 1131
1/1
c
w
a
o
3
D
0
»
»
I
d
Maestrlchtian
Campanian
Santonian
Coniacian
Turonian
Cenomanian
Surface Lithostratigraphy
West-Centra! Alabama
Tuscaloosa
Group
Prairie Bluff Chalk
Ripley Formation
Demopolii Chalk
Mooreville Chalk
Eutaw Formation
Paleozoic rocks
Gordo
Formation
Coker
Formation
Subsurface Lithostratigraphy
Southwest Alabama
upper Tuscaloosa
marine Tuscaloosa
lower Tuscaloosa
Selma Group
Eutaw Formation
Miller sand
(Warine shale
Pilot sand
Massive sand
Lower Cretaceous undifferentiated
Figure 4—Upper Cretaceous surface and subsurface stratigraphy
in Alabama.
GEOLOGIC UNIT
SELMA CHALK
EUTAW SAND
UPPER TUSCALOOSA
ENVIRONMENT OF
SP RESISTIVITY DEPOSITION
Marginal Marine
and
Marine Stielf
unit consisting predominately of sandstone in South
Carlton and Pollard fields. The sandstone unit (Pilot) is
about 100 ft (30 m) thick in South Carlton field and about
110 ft (34 m) in Pollard field, and consists of greenish
gray to green-brown, micaceous, fossiliferous, glauconitic,
calcareous, very fine to fine grained quartz-rich
sandstone (Figure 9c-f).
The Marine shale conformably overlies the Pilot sand
interval. The Marine shale expands downdip in coastal
and offshore Alabama and thins updip in Choctaw and
Butler Counties (Figures 6, 7). The Marine shale consists
primarily of about 220 ft (67 m) of dark gray, silty, micaceous,
fossiliferous, calcareous, laminated claystone
interbedded with dark gray, silty, micaceous, fossiliferous,
glauconitic, calcareous siltstone and very finegrained
sandstone in South Carlton and Pollard fields
(Figure 9a). A gray, silty, oyster packstone is present at
the base of the Marine shale in parts of South Carlton
field (Figure 9b).
The upper Tuscaloosa overlies the Marine shale and
consistsof about 375 ft (114 m) of greenish gray, glauconitic,
fossiliferous, fine to medium grained sandstone
interbedded with gray and green shales in South Carlton
and Pollard fields. These sediments accumulated in marginal
marine and marine-shelf environments (Figure 5).
The Eutaw Formation conformably overlies the upper
Tuscaloosa. The Eutaw mainly consists of micaceous,
calcareous, glauconitic, fine-grained sandstone and fossiliferous,
calcareous claystone. The Eutaw and the overlying
Selma chalk deposits represent marine-shelf
deposition (Figure 5).
ENVIRONMENTS OF DEPOSITION
The age of the lower Tuscaloosa in the South Carlton
field is Cenomanian (Figure 4) with a late Cenomanian
planktonic foraminiferal assemblage being recovered
from the Marine shale beds immediately overlying the
Pilot sand interval (Mancini et al, 1980). A major rise in
sea level occurred worldwide during the Cenomanian
(Vail et al, 1977); therefore, the lower Tuscaloosa in the
eastern Gulf Coast region has been interpreted as transgressive
with upward gradation from fluvial and deltaic
MARINE TUSCALOOSA
(Marine Shalel
Piloi
Sand
Interval
Sard
Interval
LOWER CRETACEOUS
Pilot Sandstone
Unit
Claystone Unit
Massive
Sandstone
Intetbedded Sandstone ^
and Claystone Unit
Basal Sandstone Un
Transgresslve Shell Sand
(Composite Barrier—Shoal)
rStrand Plain-Shelf-LagoDna
Slacked
Coastal
Barrier
Strand Plain-Shelf
Deltaic-Fluvial
Fluvial-Deltaic
Figure 5—Well log for Belden and Blake Wall 3-9 (permit 2182),
South Carlton field, illustrating Tuscaloosa units in subsurface
of South Carlton and Pollard fields, southwestern Alabama,
and their respective depositional environments. See Figure 2 for
vfell location.
sedimentation to shelf deposition (Berg and Cook, 1968).
From the study of 12 cores from South Carlton and Pollard
fields, well logs from over 100 wells, and well cuttings
from 35 wells drilled in southwestern and offshore
Alabama, the following depositional environments, in
ascending order, have been identified in lower Tuscaloosa
strata in the study area: fluvial or fluvial-dominated deltaic
deposition (basal sandstone unit); strand-plain and
shelf deposition (interbedded sandstone and claystone
unit); stacked coastal barrier sands (Massive sandstone
unit); strand-plain, shelf, and lagoonal deposition (claystone
unit); and transgresslve shelf sands (Pilot sandstone
unit) (Figure 5).
The oyster packstone and claystone of the marine Tuscaloosa
(Marine shale) overlying the Pilot sand interval
contain a diverse faunal assemblage of macroinvertebrates,
which includes ammonites, gastropods,
inoceramids and other bivalves, and a rich micro fossil
assemblage of planktonic foraminifera (Figure lOf) and

1132 Deposition and Petroleum Geology of Tuscaloosa Group, Southwestern Alabama
South
> A'
Permit No. 1535
Placid Oil Company
Permit No 1264-A
George H )ett Dnding Company
PermitNo 199
nbleOiland Refning Company
PermitNo 3309
Amoco Production Company
Permit No. 2069
Saga Petroleum US., Inc.
No 1 Tyson 9-14
H M Wilson No 1
J H. Wall Estate No '
No 1 Middle River Unit
No- 11-6 0thaO Dees el ux No 1
Sec.9,T 12N.R 2W
Sec 28, T 7N ,R
1 W
Sec. 15, T 3N .R 2E
Sec 13, T 2S,R IE
Sec.11,T 6S,R
2W
Choctaw County
Washington Count/
SoulhCarltoi Field
Baldwin County
Mobile County
Datum: Topof Marine Shale
Logs are Electrical with
SP on the left and
Resistivity on the right
r
VerlKal
100 X
Figure 6—Regional cross section AA' from Choctaw County to Mobile County, Alabama. See Figure 1 for line of cross section.
calcareous nannofossils. The fauna is dominated by macrofossil
and microfossil species that have been described
by Kauffman (1967), Mancini (1977), and Smith and
Mancini (1983) as being typical of a Cretaceous openmarine
shelf environment. Therefore, this claystone was
probably deposited on a shallow open-marine shelf.
The characteristics of the Massive sand interval indicate
these sediments principally accumulated as part of a
marine high-destructive delta system. In such deltaic settings,
both fluvial and marine processes are active but
marine processes dominate (Galloway, 1975). The Massive
sand interval is interpreted to represent primarily
deposition in a wave-dominated, high-destructive delta
system similar to the modern Rhone delta complex of
southern France described by Oomkens (1970) and the
ancient Gulf Coast deltas described by Fisher (1969),
Fisher et al (1970), and Ricoy and Brown (1977). The
major lithofacies recognized in these delta complexes
include fluvial sands; channel-mouth bar sands; strandplain,
lagoonal, and marsh sediments; coastal barrier
Hft (Jurassic)
PermitNo 308
Gulf Refining Company
K. Hooks No. 1
Set. 36, T 7N,R 13 E
PermitNo. 367
Stanolind Oil and Gas Company
Si Regis Paper Company "A'No 2
Set II,T 1N.R BE
PermitNo. 1777
Watson Oil Company
International Paper Company No 2
Sec. 17, T 4S,R 6E
PermitNo 2339
Phillip] Petroleum Company
International Paper Compeny "A" No. t
Sec 32,T 6S,R 6E
Permit No 4436
EMQH Company, USA.
State Lease 624 No. 1
Mobile Bay Slock 114
Butler County
Pollard Field
Baldwin County
Baldwin County
Offshore Alabama
Datum. Top of Marine Shale
Logs are Electrical with
SP on the left and
Resistivity on the right
Figure 7—Regional cross section BB ' from Butler County, Alabama, to offshore Alabama. See Figure 1 for line of cross section.

Ernest A. Mancini et al 1133
East
Permit No. 1643
Placid Oil Company
No 5-12McCI(jre
Sec 5, T 5N.R 2W
Washington County
Permit No. 199
Humble Oil and Refinmg Company
J. H. Wall Estate No 1
Sec 15, T 3N,R 2E
South Carlton fiefd
PermitNo 1742
Shell Oil Company
Wefel Estate No. 1
Sec 3, T 2 N , R 4 E
Baldwin County
PermitNo 367
5tanolind Oil and Gas Company
F. A. Stewart No. 1
Sec 11, T 1N,R 8E
Pollard Field
* "•'
Permit No, 286
Socony Mobil Oil Company
Mo. 1 St. Regis Paper Company and
Florida Oil andGasCompan/
Sec 35, T 4N,R 30W
Santa Rosa County, Florida
Datum; Top of Marine Shaie
Logs are Electrical with
SP on the left and
Resistivity on the right
v,n^csi
OTO
rt
Figure 8—Regional cross section CC' from Washington County, Alabama, to Santa Rosa County, Florida. See Figure 1 for line of
cross section.
sands; and strand-plain and shelf sediments (Fisher,
1969; Oomkens, 1970; Ricoy and Brown, 1977).
Only the basal sandstone unit of the Massive sand
interval lacks glauconite, marine shells, and bioturbation
in the South Carlton and Pollard fields. In addition, the
textural characteristics of this sandstone—medium
grained, moderately well sorted, argillaceous, and containing
angular quartz grains (Figure 10a)—-suggest fluvial
or fluvial-dominated deltaic deposition. Such
textural characteristics are typical of fluvial-dominated
delta systems (Potter, 1967; Berg, 1970; Fisher et al,
1970). The Lower Cretaceous strata underlying the Massive
sand interval have been interpreted as fluvial and
fluvial-dominated deltaic deposition (Eaves, 1976). The
basal sandstone unit probably represents a continuation
of such deposition. This unit is present both updip and
downdip in southwestern Alabama (Figures 6, 7). In outcrop
north and east of the study area, the Tuscaloosa is
characterized by fluvial and fluvial-dominated deltaic
deposition (Reinhardt, 1980; Russell et al, 1980).
The interbedded sandstone and claystone unit of the
Massive sand interval marks a change from fluvialdominated
deltaic deposition to marine-dominated
deposition. These sandstones are thinly bedded, discontinuous,
bioturbated, moderately well sorted, locally fossiliferous,
calcareous, slightly glauconitic, argillaceous,
and fine grained, containing angular to subangular
quartz grains (Figure 10b). Marine bivalves occur in the
sandstones and interbedded claystones. The interbedded
unit probably represents strand-plain and shelf deposition.
The presence of marine bivalves and glauconite
indicates marine depositional conditions. The textural
characteristics of the interbedded sandstones are similar
to the characteristics for strand-plain sands as described
by Oomkens (1970) for the Rhone delta and by Fisher
(1969) and Ricoy and Brown (1977) for ancient Gulf
Coast delta systems. The interbedded sandstone and
claystone unit becomes a more dominant lithofacies of
the Massive sand interval downdip in coastal and offshore
Alabama (Figures 6,7).
The sandstones of the Massive sand sandstone unit
probably accumulated as stacked coastal barrier sands.
The sandstones are well sorted, micaceous, locally fossiliferous,
calcareous, glauconitic, fine grained, and quartz
rich, containing angular to subangular quartz grains
(Figure 10c). These sandstones are thick, structureless,
and bioturbated with thin, silty, claystone interbeds. The
sandstones are principally quartzarenites, subarkoses,
and sublitharenites with an average composition of
60.0% quartz; 12.2% accessory minerals, including chlorite
and shell fragments; 9.7% clay matrix; 6.6% glauconite;
4.5% cement, primarily calcite; 3.9% potassium
and plagioclase feldspars; and 3.1% rock fragments, primarily
muscovite (Figure 10c). The presence of marine
bivalves and glauconite in the sandstones indicates
marine depositional conditions. The sedimentologic
characteristics of the upper sandstone unit are like those
described by Oomkens (1970) for modern coastal barrier
sands and by Fisher (1969), Fisher et al (1970), and Ricoy
and Brown (1977) for ancient coastal barrier sands. Typically,
coastal barrier sands are thick, massive units that
contain marine organisms and glauconite (Fisher, 1969;
Oomkens, 1970; Ricoy and Brown, 1977). These sands
are usually fine grained and well sorted and contain subangular
quartz grains (Fisher et al, 1970; Oomkens,
1970). Also, they have a characteristic spontaneous
potential pattern. The spontaneous potential pattern of
the Massive sandstone unit (Figure 5) compares favorably
with that pattern described by Fisher (1969) for
stacked coastal barrier sands associated with wave-

1134 Deposition and Petroleum Geology of Tuscaloosa Group, Southwestern Alabama
Figure 9—Core slabs of lower Tuscaloosa from Belden and
Blake Wall 3-9 core (permit 2182): (A) Marine shale, 5,272 ft
(1,606.9 m); (B) oyster packstone, 5,281 ft (1,609.6 m); (C)
structureless sandstone in Pilot sandstone unit, 5,285 ft
(1,610.8 m); (D) oil-saturated sandstone in Pilot sandstone
unit, 5,295 ft (1,613.9 m); (E) fossiliferous sandstone in Pilot
sandstone unit, 5,300 ft (1,615.4 m); and (F) bioturbated sandstone
in Pilot sandstone unit, 5,316 ft (1,620.3 m). See Figure 2
for well location and Figure 11 for location of core slabs.
dominated, high-destructive ancient Gulf Coast deltas.
The Massive sandstone unit attains maximum thickness
in Washington County and near South Carlton and Pollard
fields (Figures 6-8).
The claystone unit of the Pilot sand interval marks a
return to strand-plain and shelf deposition downdip in
coastal and offshore Alabama, and represents strandplain,
shelf, and lagoonal deposition throughout most of
southwestern Alabama. This unit pinches out updip in
Butler County (Figure 7). These sandstones are fossiliferous,
calcareous, and very fine to fine grained in the South
Carlton and Pollard fields. Marine bivalves, such as
inoceramids, are present in the sandstones and interbedded
claystones.
The Pilot sandstone unit of the Pilot sand interval
accumulated as shelf sands during a marine transgression.
This unit consists of well-sorted, micaceous, fossiliferous,
calcareous, glauconitic, very fine to fine grained,
quartz-rich sandstones, containing subangular to subrounded
quartz grains (Figure lOd, e). These sandstones
generally appear massive, but may be structureless as a
result of extensive bioturbation and/or oil saturation
(Figure 9c-f). The sandstones are principally quartzarenites
and subarkoses with an average composition of
61.0% quartz; 14.5% cement, primarily calcite; 9.4%
clay matrix; 5.2% glauconite; 3.1% potassium and
plagioclase feldspars; 2.9% rock fragments, primarily
sedimentary and metamorphic; 2.9% accessory minerals,
including chlorite and shell fragments; and 1% muscovite
(Figure lOd, e). The mean and maximum quartz
grain sizes decrease upward within individual bed sets
(Figure 11). Marine bivalves, such as inoceramids, are
present in the sandstones. The characteristics of these
sandstones are similar to those sands associated with the
modern transgressive barrier shorelines of the Mississippi
River delta plain as described by Penland et al
(1981), Penland and Suter (1983), Moslow (1984),
Penland (1985), and Penland et al (1985). These transgressive
barrier shorelines, which are a result of delta
abandonment, have a complex history consisting of three
stages: stage 1, an erosional headland with flanking barriers;
stage 2, a transgressive barrier island arc; and stage
3, a subaqueous inner shelf shoal (Penland et al, 1981;
Penland and Suter, 1983). The sands of the transgressive
barrier island arcs and inner shelf shoals are fine grained,
well sorted, quartz rich, calcareous, glauconitic, bioturbated,
exhibit good quartz roundness, and are associated
with a marine fauna (Krawiec, 1966; Moslow, 1984;
Penland, 1985).
The transgressive barrier island arcs are 20-47 mi (32.1-
75.6 km) long, 1-1.5 mi (1.6-2.4 km) wide, and 7-16 ft
(2.1-4.9 m) high (Penland, 1985; Penland et al, 1985).
The inner shelf shoals are 20-22 mi (32.1-35.4 km) long,
1-6 mi (1.6-9.7 km) wide, and 7-23 ft (2.1-7.0 m) high
(Moslow, 1984). These shelf sands are a function of a
sediment supply and dispersal pattern associated with
reworking of delta plain deposits and sea level rise
(Penland and Suter, 1983). Long-term relative sea level
rise and erosional shoreface retreat leads to the barrier
shoreline detaching from the mainland, forming a barrier
island arc (Penland et al, 1985). With continued
transgression, the morphology of the barrier shoreline
can be further modified or destroyed, resulting in a
seaward-extending sand sheet upon which inner shelf
shoals or ridges can develop (Penland, 1985). Storms
erode the seaward slope and crest of those shoals and
transport the sediment landward; as the shoal migrates
landward, the seaward extent of the shoal is reworked
and deposited as a seaward-extending sand sheet
(Penland, 1985).

Ernest A. Mancini et al
.10 mm T nwn
Figure 10—Photomicrographs of lower Tuscaloosa strata: (A) moderately well-sorted sandstone in basal sandstone unit in Massive
sand interval, 5,837 ft (1,779.1 m), from Clarkwin J. H. Wall Estate 1 core (permit 199); (B) sandstone with calcite cement in
the interbedded sandstone and claystone unit in Massive sand interval, 5,770 ft (1,758.6 m), from Clarkwin J. H. Wall Estate 1 core
(permit 199); (C) well-sorted sandstone in Massive sandstone unit in Massive sand interval, 5,540 ft (1,688.5 m), from Clarkwin J.
H. Wall Estate 1 core (permit 199); (D) well-sorted sandstone in Pilot sandstone unit in Pilot sand interval, 5,330 ft (1,624.5 m),
from Clarkwin J. H. Wall Estate 1 core (permit 199); (E) sandstone with calcite cement in Pilot sandstone unit in Pilot sand interval,
5,298 ft (1,614.8 m), from Humble Wall 6 core (permit 275); and (F) oyster packstone above the Pilot sand interval, 5,281 ft
(1,609.6 m), from Belden and Blake Wall 3-9 core (permit 2182). See Figure 2 for well locations.

1136 Deposition and Petroleum Geology of Tuscaloosa Group, Southwestern Alabama
Quartz grain size (mm)
DM 0.66 0.46 0.36 0.26 0.16 0.06
I I - 1
0.5
medium 0.26^1 0.1251
fine' veryfine
Permit No. 2182
Belden and Blake
WalI.etal 3-9
Sec. 3, T 3 N, R 2 E
Clarke County, Alabama
SP
Rosiitivity
Sandstone composition (.%)
0 20 40 60 80 10O
•y •y -r
Feldspir, Rock Fraginenti,
and others
Quartz
Glauconite
r.-..:l Sandstone I ° I Glauconitic
I—I Silty Claystone I " I Micaceous
l-'-rl Limestone I ^ I Fossiliferous
EZI Oil CT] Biotjrbated
A, B, C,D, E, F Key to core photographs
Figure 11—Vertical change in quartz grain size and sandstone composition in Pilot sandstone unit in Belden and Blake Wall 3-9
well (permit 2182). See Figure 2 for well location.
The composite barrier and shoal lithofacies of the
Pilot sandstone unit at South Carlton field are oriented
northeast to southwest and are at least 3 mi (4.8 km) long,
1.5 mi (2.4 km) wide, and 40-70 ft (12.2-21.3 m) high
(Figure 12). The Pilot sandstone unit overlies strandplain,
shelf, and lagoonal sediments and is overlain by
marine shelf deposits (Figure 5). At South Carlton field,
the Pilot represents a fining-upward sequence (Figure 11)
that developed over a salt dome. The Pilot sandstone unit
penetrated in the South Carlton field principally represents
the transgressive barrier island arc and inner shelf
shoal environments of Penland (1985) and Penland et al
(1985). Stratigraphic cross section DD' indicates the
composite barrier and shoal lithofacies are in the central
portion of South Carlton field and the back-barrier and
back-shoal lithofacies are probably west of the field (Figure
13). Although the transgressive barrier island arcs
and inner shelf shoals described by Penland (1985) represent
coarsening-upward sequences. Potter (1967) and
Bourgeois (1980) report fining-upwardsequences as typical
for transgressive shelf sands. The Pilot sandstone unit
is present throughout most of southwestern Alabama,
but is thickest in Washington County and in South
Carlton and Pollard fields (Figures 6,8). The Pilot sandstone
unit thins updip in Choctaw County, downdip in
coastal and offshore Alabama (Figures 6,7), and pinches
out in Butler County (Figure 7). The Pilot sandstone unit
probably accumulated as transgressive sand bodies on a
storm-traversed, shallow marine shelf.
PETROLEUM GEOLOGY
Petroleum traps involving Tuscaloosa strata in southwestern
Alabama are structural traps involving salt anticlines
and extensional fault traps associated with salt
movement. The South Carlton structure is a low-relief
feature (Figures 2, 14) overlying a deep-seated Jurassic
Louann Salt dome, which had structural growth in the
latest Cretaceous. The Getty Barbour 2-12 (permit 2149)
drilled as a Jurassic wildcat in the field penetrated the
Louann Salt below 16,000 ft (4,876.8 m) subsea (Figure
2). The feature encompasses approximately 4,500 acres
(1,822.5 ha.) and has about 80 ft (24.3 m) of structural
closure on top of the lower Tuscaloosa (Figure 2).
The structure in Pollard field includes a westnorthwest-trending
graben system associated with the
PoUard-Foshee fault systems (Figures 1,15). These fault
systems are part of the regional peripheral fault trend
associated with Louann Sah movement. Faulting along
this trend began in the Jurassic and continued in the Miocene,
with maximum movement observed in Cretaceous
strata (Murray, 1961; Martin, 1978). The Pollard fault,
which is downthrown to the north, is the main fault
forming the petroleum trap at Pollard field (Figures 3,
15). The Exxon Loper 1 (permit 1459A) drilled as a Jurassic
wildcat south of the fieldpenetrated the Louann Salt
below 15,300 ft (4,633.4 m) subsea (Figure 15). Displacements
of up to 50 ft (15.2 m) are evident in Eocene strata
at Pollard field,indicating that faulting was active in the
Tertiary. The Pollard feature encompasses approximately
4,700 acres (1,903.5 ha.) and has up to 80 ft (24.4
m) of structural closure on top of the lower Tuscaloosa
(Figure 3).
The recent Tuscaloosa discovery by Hughes Eastern
Corporation in the Pilot sandstone unit is located about
1.5mi (2.4 km)northofPollard field (Figure 1). This discovery
is along the Pollard-Foshee fault trend, and the
petroleum trap is interpreted to be similar to the trap at
Pollard field.
At South Carlton and Pollard fields,the major petroleum
reservoirs are the stacked coastal barrier sandstones

Ernest A. Mancini et a! 1137
of the Massive sandstone unit and the transgressive shelf
sandstones of the Pilot sandstone unit. Although reservoir
geometry is principally structurally controlled in
these fields, lithofacies distribution in the Pilot sand
interval affects reservoir quality. Stratigraphic cross sections
(Figures 13, 16) indicate that maximum sandstone
and reservoir development is in the composite barrier and
shoal lithofacies in the central parts of South Carlton and
Pollard fields. In the Belden and Blake Wall 3-9 well (Figure
11), located in the north-central portion of South
CarUon field, at least 17 ft (5.2 m) of sandstone is oil
bearing (Figure 9d).
Core analyses from 12 wells indicate that porosities in
the stacked coastal barrier sandstones of the Massive
sandstone unit average 28.5% at Pollard field with permeabilities
of 100-900 md; they average 21% at South
Carlton field with permeabilities of 50-600 md. Porosities
in the transgressive shelf sandstones of the Pilot
sandstone unit average 29.5% at Pollard field with permeabilities
of 250-1,000 md; they average 25% at South
CarUon field with permeabilities of 150-500 md. Porosity
is primarily intergranular (Figure 10c, d). A reduction in
porosity in the Pilot sandstone unit at South Carlton field
is a result of compaction and calcite cementation (Figure
lOe).
ORGANIC GEOCHEMISTRY
EXPLANATION
• OIL WELL
>- AaANDONEOOILWELL
^
DRY HOLE
- • SALTWATERDISPOSALWELL
2182 WELLPERMIT NUMBER
CONTOUBINTERVAl . 6
Figure 12—Isolith map of net sand in Pilot sandstone unit,
South Carlton field, Clarke and Baldwin Counties, Alabama.
Htl
The Upper Cretaceous crude oils in southwestern Alabama
are considered heavy oils for the most part (Table
1). The Tuscaloosa crude oils have hydrocarbon compositions
of 91.1-94.9% C|5+ hydrocarbons. The low percentage
of light hydrocarbons may be attributed, in part,
to the maturation state. In addition, at South Carlton
field the light hydrocarbons (normal paraffins) that
migrated into the reservoir probably were destroyed by
biodegradation or removed through water washing as a
result of the reservoir being invaded by an influx of
freshwater-containing bacteria (Figure 17b). Microbial
alteration (biodegradation) and removal of water-
PermitNo 3262
Betd«n and Blake Ccvporalion
Barbour I«-1S
S«c 16, T 3 N , R 2 E
Permit No 1023
Ctark«in Oil Corporation
State olAlabamatnit No I
Sec 10, T JN .R 3E
Permit No 3332
Selden and Blake Corporation
Uo 1 Wall 11-3
Se( 11, T 3 N , fl 2 E
Permit No 1531
Houston Oil and Minerals Corporation
No S Oanner
Sec 11,1 3N .R 2E
Datum: Topof Marine Shale
LogtareElectncal witli
SRontheleftand
Resistivity on tile right
Figure 13—Stratigraphic cross section DD' across South Carlton field, Clarke and Baldwin Counties, Alabama.

1138 Deposition and Petroleum Geology of Tuscaloosa Group, Southwestern Alabanna
North
E
Permit No 3331
Belden and Blake Corporation
No 1 Wall n-4
Sec. n,T 3N , R 2E
Sojth
E'
Permit No. 2025
Canton Oil and Gas Company
Wall 35-9 No. 1
Sec 35,T 4N,P 2E
Permit No 1023
Clarkwin Oil Corporation
Staleof Alabama Unit No •
Sec 10, T 3N ,R 2E
Permit No 3252
Belden and Blake Corporati
Barbour 16-15
Sec 15, T 3 N ,R 2 E
Permit No 3510
Belden and Blake Corporation
Ferguson 5-10 No. 1
Sec 5,T 2rJ ,R 2E
Figure 14—Structural cross section E£' across South Carlton field, Clarke and Baldwin Counties, Alabama.
soluble compounds (water washing) from crude oils are
common in areas invaded by surface-derived meteoric
formation waters (Tissot and Welte, 1984).
The compositions of the C15+ extracts from the Tuscaloosa
crude oils consist of 69.2-69.3% hydrocarbons.
The C15+ composition of these oils is comprised of 35.7-
43.1% saturates, 26.2-33.5% aromatics, 20.9-23.3%
asphaltenes, and 7.5-9.8% nitrogen-sulfur-oxygen
(NSO) compounds. The carbon isotope (5C^^) values
based on PDB standard for the saturate fraction are from
-24.7 to -25.4 %o, and the aromatic fractions are
from -23.9 to -25.2 0/00. These geochemical and carbon
isotope values are consistent with the C15+ compositional
data (40-47% naphthenes, 5-12% paraffins, and
22-33% aromatics) and carbon isotope (from -25.7 to
-25.8 Voo for the saturate fraction and from -24.6 to
- 25.2%o for the aromatic fraction) values published by
Koons et al (1974) for Tbscaloosa crude oils from South
Carlton and Pollard fields. Crude oils from the Selma
and Eutaw reservoirs at Gilbertown field have composi-
Permit No. 3B4
GuH Refining Company
T F Miller Mill Company No 4
Se

Ernest A. Mancini et al 1139
Permit No 406
Stanolind Oil ary] Qn Comp^n^
St. RegrsPaperCompany No 7
Sfc.n.T IN.R 8E
Permit No. 403
Stanolind Oil and Gas Company
Gra/UnilNo 2
Sec 12, T I N,R 8E
Permit No 422
Gulf Refining Company
T R Miller Mill Company No 5
Sec 12, T 1 N, R 8E
PermilNo 357
Humble Oil and Refining Company
G A Carter No 1
Sec 1B,T 1 N,R 9E
Datum: Top of Marine Shale
Logsar«EI«ctrical with
SPon the left and
Kesiitivity on the right
Figure 16—Stratigraphic cross section GG' across Pollard field, Escambia County, Alabama.
tion and isotope values similar to the Tuscaloosa crude
oils (Table 1).
The organic geochemical composition, C,5+ saturate
distributions (Figure 17c), and carbon isotope data for
the crude oils from the Tuscaloosa reservoirs indicate the
origin of the oil was more likely from organic matter
formed in normal saline water of an open ocean than
from organic matter from brackish-water or terrestrial
environments. Marine organic matter usually generates
crude oils consisting of 30-70% saturated (paraffins and
naphthenes) hydrocarbons (Tissot and Welte, 1984).
Most land plants have carbon isotope values that range
from -24 to -34 %o, and marine organisms usually
have 6C" values heavier than -24 %o (Waples, 1981).
Eckelmann et al (1962) suggests that the more negative
6C" values indicate a greater contribution to oil generation
from organic matter formed in terrestrial or
brackish-water environments.
From their analysis of Tuscaloosa crude oils from Alabama
and Mississippi, Koons et al (1974) conclude that
the Tuscaloosa crude oils originated from two distinct
sources. Ibscaloosa claystones were one source rock,
while the second source was unidentified. The crude oils,
including those at South Carlton and Pollard fields that
were derived from the unidentified source (which was
probably older geologically than the Tuscaloosa crude
oils), were believed to have migrated into the Thscaloosa
reservoirs along faults (Koons et al, 1974). Such a
hypothesis is plausible for Pollard field because of the
nature of the faulting; however, to date, no faults have
been mapped at South Cariton field. To test this hypothesis
further, source rock analyses were performed on the
Ibscaloosa claystones in the South Carlton and Pollard
fields and on other crude oils in southwestern Alabama.
Although the Tuscaloosa marine claystones contain
significant amounts of organic carbon, these claystones
are thermally too immature to be the petroleum source
rocks for the Ibscaloosa crude oils in South Carlton and
Pollard fields. The total organic carbon content for these
claystones ranges up to 2.91% (Table 2). The dominant
kerogen type is amorphous (algal) and herbaceous. However,
these rocks have been only moderately thermally
altered, as evidenced by their thermal alteration indices
of 1 -I- to 2 +; therefore, any hydrocarbons generated from
these claystones should be immature. The C15+ paraffinnaphthene
distributions (Figure 17a) from the Marine
shale illustrate an immature state for hydrocarbon generation.
On the other hand, the carbon isotope values for
the saturate fraction (- 26.3 %o) and the aromatic fraction
(-24.5 %o) and the hydrocarbon composition
(22.3% saturates, 27.8% aromatics, 33.1% asphahenes,
and 16.8% NSO compounds) compare favorably with
the characteristics of the Tuscaloosa crude oils. With
increased burial depth, these marine claystones, with
their mixture of marine and terrestrial organic matter,
could be a source for the crude oils of the Tuscaloosa reservoirs.
However, regional cross sections (Figures 6-8)
indicate that Tuscaloosa deep basinal fades have not
been identified in southwestern and offshore Alabama.
Koons et al (1974) indicate the Tuscaloosa claystones in
the deeper portions of the Mississippi interior salt basin
had seen sufficient burial depth and thermal maturation
to generate crude oil; however, the hydrocarbon composition
(27% paraffins as compared to 5-12% paraffins
for South Carlton and Pollard crude oils) and carbon isotopic
values (- 27.9 ± 0.6 %o as compared to - 25.4 to
- 24.7 %o for South Carlton and Pollard crude oils) for
the saturate fraction of these crude oils differ from the
South Carlton and Pollard crude oils.
Analysis of the other crude oils in southwestern Alabama
indicate that Lower Cretaceous and Upper Jurassic
crude oils are similar in some respects to the Upper Cretaceous
crude oils (Table 1). Lower Cretaceous crude oil
(Figure 17d) from Citronelle field (a salt dome without
faulting) has a saturated hydrocarbon content of 56.3%
and carbon isotope values of - 25.6 %o for the saturate
fraction and - 25.0 %o for the aromatic fraction. Upper
Jurassic crude oils from fields (Little Mill Creek and Lit-

1140 Deposition and Petroleum Geology of Tuscaloosa Group, Southwestern Alabama
Table 1. Analyses of Crude Oils from Fields in Southwestern Alabama'
Field2
Gilbert own
County
Choctaw
Formation
Selma
Age
Late
Cretaceous
"API
gravity
18.7
Asphal
-tene
(%)
28.6
Saturate
(%)
23.8
Aroma
-tic
(%)
34.3
NSO
compounds
(%)
13.3
513C
Saturates
(%o)
-25.0
813C
Aroma
-tic3
(%•)
-25.1
Gilbertown
South Carlton
Choctaw
Clarke &
Baldwin
Eutaw
Lower
Tuscaloosa
Late
Cretaceous
Late
Cretaceous
15.3
15.6
28.1
23.3
21.9
35.7
37.7
335
12.2
7.5
-25.0
-25.4
-25.0
-25.2
Pollard
Esambia
Lower
Tuscaloosa
Late
Cretaceous
29.0
20.9
43.1
26.2
9.8
-24.7
-23.9
Citronelle
Mobile
Rodessa
Donovan
Early
Cretaceous
42.0
19.1
56.3
15.6
9.0
-25.6
-250
Little Mill Creek
Choctaw
Smackover
Late
Jurassic
46.2
33.2
37.8
17.9
11.1
-23.3
-23.0
Little Escambia
Creek
Escambia
Smackover
Late
Jurassic
48.5
21.2
50.5
12.8
15.5
-24.1
-22.9
Oil composition analyses by ARCO Oil and Gas Company and carbon isotope analyses by U.S. Geological Survey.
'See Figure 1 for field locations
3PDB standard
tie Escambia Creek) along the regional peripheral fault
trend have saturated hydrocarbon contents from 37.8-
50.5% and carbon isotope values that range from -23.3
to - 24.1 %o for the saturate fraction and from -22.9
to -23.0 %o for the aromatic fraction. These Jurassic
crude oils are similar in saturate composition but isotopically
are somewhat heavier than the crude oil from Pollard
field. The organic geochemical (Figure lie, f) and
carbon isotope data (Ikble 1) for the Upper Jurassic
crude oils indicate these oils were probably generated
from organic matter that formed in normal saline waters
similar to the environment in which the organic matter
that generated the Tuscaloosa crude oils accumulated.
Other authors (Mancini and Benson, 1980; Oehler, 1984)
have proposed that the Smackover Formation is the
source for the Upper Jurassic hydrocarbons. The Smackover
algal mudstones also have the potential to be the
unidentified older source rocks of Koons et al (1974) that
generated the Upper Cretaceous crude oils that migrated
up the faults along the regional peripheral fault trend,
including the Tuscaloosa crude oil at Pollard field. The
source of the Tliscaloosa crude oil at South CarUon field
remains problematic. Perhaps the Smackover is the
source for this crude oil or perhaps the Tuscaloosa claystones
to the west in the deeper portions of the Mississippi
interior salt basin are the source rocks. Because the
crude oil at South Carhon field has been altered through
biodegradation and/or water washing, the task of tracing
its origin is difficult.
EXPLORATION STRATEGY
Although the Tuscaloosa is productive at both South
Carlton and Pollard fields, the results of this study indicate
that exploring for Tliscaloosa prospects similar to
Pollard field holds the most promise. The petroleum trap
at Pollard fieldis structural and involves salt movement
along the Pollard fault system. Recent Jurassic Smackover
and Norphlet and Cretaceous Tuscaloosa discoveries
along the regional peripheral fault trend, of which
the Pollard fault system is a part, also support the strategy
of exploring for Tuscaloosa oil along this fault trend.
The Tuscaloosa oils encountered are anticipated to be
intermediate gravity oils (30°-40° API), unlike the
degraded heavy oils associated with the salt dome at
South Carlton field. If indeed the oil trapped at Pollard
had as its source the Smackover carbonate mudstones,
Jurassic oil had the opportunity to migrate up the fault
planes of the Pickens-Gilbertown, West Bend, and
Foshee fault systems in addition to the Pollard fault system
because displacement in Tertiary strata is evident in
all of these fault systems. Reservoir grade porosities and
permeabilities should be preserved in stacked coastal barrier
sandstones and transgressive shelf sandstones.
REFERENCES CITED
Berg.R. L., 1970, Identification of sedimentary environments in reservoir
sandstones: Gulf Coast Association of Geological Societies
Transactions, v. 20, p. 137-143.
and B. C. Cook, 1968, Petrography and origin of lower Tliscaloosa
sandstones, Mallalieu field, Lincoln County, Mississippi:
Gulf Coast Association of Geological Societies Transactions, v. 18,
p. 242-255.
Bourgeois, J., 1980, A transgressive shelf sequence exhibiting hummocky
stratification: the Cape Sebastian Sandstone (Upper Cretaceous),
southwestern Oregon: Journal of Sedimentary Petrology, v.
50, p. 681-702.
Drennen, C. W., 1953, Reclassification of outcropping Tliscaloosa
Group in Alabama: AAPG Bulletin, v. 37, p. 522-538.
Eaves, E., 1976, Citronelle oil field, Mobile County, Alabama: AAPG
Memoir 24, p. 259-275.
Eckelmann, W. R., W. S. Broecker, D. W. Whitlock, and J. R. AUsup,
1962, Implications of carbon isotopic composition of total organic

Ernest A. Mancini et a! 1141
Figure 17—C,5 ^ saturate gas chromatograms for (A) Upper Cretaceous Marine shale sample, 5,265 ft (1,604.7 m), from Clarkwin
J. H. Wall Estate 4 core (permit 245); (B) Upper Cretaceous lower lUscaloosa (Pilot sand) oil sample from Belden and Blake Wall 3-
9 well (permit 2182); (C) Upper Cretaceous lower Itascaloosa (Pilot sand) oil sample from Tidewater A. W. Moye 4 well (permit
400), Pollard field, Escambia County; (D) Lower Cretaceous Rodessa (Donovan) oil sample from Citronelle Unit Harry Fisher 18-
4 well (permit 933), Citronelle field. Mobile County; (E) Upper Jurassic Smackover oO sample from Midroc Tims 8-21 well (permit
2463), Little Mill Creek field, Choctaw County; and (F) Upper Jurassic Smackover oil sample from Exxon McDavid Lands 30-2B
well (permit 2533), Little Escambia Creek field, Escambia County. See Figures 1-3 for well and field locations.

1142 Deposition and Petroleum Geology of Tuscaloosa Group, Southwestern Alabama
Table 2. Organic Carbon and Kerogen Analyses from
Ibscaloosa Clay stones'
Well 2
Clarkwin Oil
J. H. Wall Estate No. t
Sec. 15,T3N, R2E
ClarkeCo. (Permit 199)
Clarkwin Oil
J.H. WallNo. 1-D
Sec. 10,T3N, R2E
Clarke Co. (Permit 243)
Clarkwin Oil
J. H. Wall Estate No. 4
Sec. 11,T3N,R2E
Clarke Co. (Permit 245)
Humble Oil
J.H. Wall Estate No. 5
Sec.15,T3N,R2E
Clarke Co. (Permit 257)
Clarkwin Oil
J.H. Wall Estate No. 1-B
Sec. 10, T3N,R2E
Clarke Co.(Permit 269)
Belden & Blake
Wall No 3-9
Sec. 3,T3N,R2E
ClarkeCo. (Permit 2182)
(ft)
5223
5275
5256
5400
5420
5250
5255
5265
5305
5345
5420
6562
5450
5290
5410
5270
5273
Sample
depth
(m)
1593.0
1608.9
1603.1
1647.0
1653.1
1601.2
1602.8
1605.8
1618.0
1630.2
1653.1
2001.4
1662.2
1613.4
1650.0
1607.4
1608.3
0rgani<
carbon
I'M,)
0.76
2.90
1.79
1.10
0.79
0.8a
1.85
2.91
1.34
0.44
0.54
0.08
0.92
1.14
0.44
1.63
1.35
type
Herbaceous
Amorphous (Algal)
Amorphous
Woody
Herbaceous
Herbaceous
Amorphous (Algal)
Amorphous (Algal)
Amorphous (Algal)
Amorphous
Woody
Woody
Herbaceous
Herbaceous
Herbaceous
Amorphous
Amorphous (Algal)
''Analyses were done by Geochem Laboratories, Houston, Texas.
^see Figure 2 for well locations.
Thermal
alteration
(1-5 scale)
1+to2-
1 +to2-
l•^to2-
l•^to2-
1+to2-
1+to2-
1+to2-
1tto2-
1tto2-
1 +to2-
1 + to 2-
1