geological circular 80-12 geology and geot)ydrology of
TRANSCRIPT
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Geological Circular 80-12
Geology and Geot)ydrology_ of . the East Texas Basin
A Report on the Progress of Nuclear Waste Isolation Feasibility Studies (1979]
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C. W. Kreitler, 0 . K. Agagu , J. M. Basciano, E. W. Collins, 0 . Dix, S. P. Dutton, G. E. Fogg, A. B. Giles, E. H. Guevara, D. W. Harris, D. K. Hobday, M. K. McGowen, D. Pass, and D. H. Wood
Bureau of Economic Geology0
W. L. Fisher, Director
1980 otSmBUTlOI Of ntiS POCUNEU IS U~liMITED
0 The University of Texas at Austin Austin, Texas 78712
DISCLAIMER
This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
DISCLAIMER
Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.
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Geological Circular 80-12
NOTICE PORTIONS OF THIS R~PORT ~RE ILLEGIBLE..
H has been reproduced irom the best available copy to per·mit ttte broadest possible avaiii:bilit)l.
GEOLOGY AND GEOHYDROLOGY OF THE EAST TEXAS BASIN
A Report on the Progress of Nuclear Waste Isolation Feasibility Studies (1979)
by
C. W. Kreitler, 0. K. Agagu, J. M. Basciano, E. W. Collins, 0. Dix, S. P. Dutton, G.·E. Fogg,
A. B. Giles, E. H. Guevara, D. W. Harris, D. K. Hobday, M. K. McGowen, D. Pass, and D. H. Wood
Bureau of Economic Geology W. L. Fisher, Director
The University of Texas at Austin University Station, P. 0. Box X
Austin, Texas 78712 >---------DISCLAIMER--------, k nsored bv an agency of tho United States Government.
Th~s book was ~repared as an :::~~'=an~encv thereof. nor any of thei~ .employees. makes any Nmthor the Un1ted Stat:S ~ r assumes any legal liability or responsib•htv lor the 8CC\lfllCV. warranty, express or •mphed, o n information, apparatus, product, or process disclosed,. ~r completeness, ~ usefulness of
8 i:lri privately owned rights. Reference herein to anv. spec•llc represent~ that 1ts use ....auld not , n: trade name, trademark, manufacturer, or otherwise, ~oes commerc•al ~roduct, ':"'ocess. 0~ serv•c.e :OOorsement, recommendation, or tSYOring by the Un•ted
not necesso:~~:n:•t~~: :~:P:~er~~t. The views and opinions of authOrs expressed herein do not
:::;~;:tate or reflect those of the Uniled States Government or anv agency thereof.
Prepared Ior the U.S. Department of Energy under Contract No. DE-AC97-79ET -~05
1980
DISTRIBUTIOR OF TillS OOCUMU~ IS UNLIMITHI ~
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THIS PAGE
WAS INTENTIO-NALLY.
LEFT BLANK
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CONTENTS
East Texas salt dome studies-- a summary of second-year research activities . 1
Purpose and scope 3
Stratigraphic framework and depositional sequences of the East Texas Basin lf
Regional tectonic framework of the East Texas Basin 11
Evolution of East Texas salt domes • 20
Hydrologic stability of Oakwood Dome . 30
Drilling and hydrogeologic monitoring at Oakwood Salt Dome . 33
Aquifer modeling at Oakwood Dome • . 35
Studies of cap rock on Gyp Hill Salt Dome . 41
Impacts of salt-brining on Palestine Salt Dome • . 46
Regional aquifer hydraulics, East Texas Basin . 55
Salinity of formation waters . 68
Geochemistry of ground water in the Wilcox aquifer . 73
Carbon-14 dating of Wilcox aquifer ground water 79
Petrography and diagenesis of Wilcox sandstones 83
Surface geology and shallow borehole investigations of Oakwood Dome --
preliminary studies .
Analysis of selected stream drainage systems in the East Texas Basin
Studies of lineaments in East Texas
The Qu~en City Formation .
Acknowledgments
References
FIGURES
• 88
• 93
. 101
• 105
. 108
. 109
1. Location map of salt dome province, East Texas Basin . 7
2. Stratigraphic succession and nomenclature in East Texas Basin 8
3. Dip structure cross section through Freestone, Leon, and Houston Counties . 9
4. Dip structure cross section through Van Zandt, Smith, and Rusk Counties . 10
5. Megatectonic elements around the East.Texas Basin • 14
iii
6. Isopach map of combined Eagle Ford, Woodbine, and Maness Formations . . 15
7. Main structural trends in the East Texas Basin 16
8. Seismic section through VanZandt County 17
9. Isopach map of Pecan Gap Member, Lower Taylor Formation, and Austin Group • • 18
10. Major depositional axes in East Texas Basin • 19
11. Schematic evolution of salt diapirs . 21
12. North-south structure section through Keechi Dome, Anderson County, Texas • . 22
13. West-east structure section through Bullard Dome, Smith County, Texas • . 23
14. North-south structure section through Whitehouse Dome and the cast flank of Bullard Dome, Smith County, Texas. 24·
15. Domal sections with no vertical exaggeration 25
16. Northwest-southeast structure section through Grand Saline Dome, Van Zandt County, Texas 26
17. Northwest..:.southeast structure section through Bethel Dome, Anderson County, Texas , • 27
18. Northwest-southeast structure section through Hainesville" Dome, Wood County, Texas • 28
19. Domal sections with no vertical exaggeration . 29
20. Ground-water salinity estimates in the Carrizo and major sands of the Wilcox • 32
21. Integrated finite difference (IFD) mesh for preliminary model of flow around Oakwood Dome . 38
22. Computed heads from preliminary model of flow around Oakwood Dome . . 39
23. Graphic correlation of Wilcox Group heterogeneities using electric logs from Oakwood and Keechi Dome areas . . 40
24. Percent gypsum versus depth in Gyp Hill cap rock • 42
25. Rectangular anhydrite crystals surrounded by poikilotopic gypsum cement 43
26. Rectangular anhydrite crystals surrounded by chaotic mass of· fine-grained anhydrite • 43
27. Porous anhydrite sand immediately above the salt • . 44
28. Rectangular anhydrite crystals in salt (black mineral) 44
29. Sketch map of surface features over Palestine Salt Dome . . 49
30. Photos of solution collapses at Palestine Salt Dome 50
31. Locations of sinkholes overlying Palestine Salt Dome 52
32 .. Potentiometric surface map of the Wilcox-Carrizo aquifer system . 58
iv
e
33. Detail of Wilcox-Carrizo ground-water flow in Anderson County • 59
34. Ground-water flow lines in the Wilcox-Carrizo aquifer system • 60
35. Structure contour map on top of Wilcox Group . . 61
36. Percent sand map of Wilcox Group . 62
37. Head differentials between Queen City and Wilcox-Carrizo aquifer systems • 63
38. Profiles showing elevations of Wilcox-Carrizo major streambeds
water 'levels above 64
39. Net clay thickness of Reklaw aquitard .• • 65
40. Basinward pressure-versus-depth relationship for the Wilcox-Carrizo aquifers 66
41. Potentiometric surface map for the Queen City aquifer . 67
42. Maximum salinity in the Woodbine Sand ; • 70
43. Relationship between formation resistivity (Ro) and TDS concentration of formation water . . 71
44. Percent of Wilcox thickness containing fresh water • 72
45. Correlation of sodium and bicarbonate in Wilcox ground water 75
46. Increase in pH values with depth • . 76
47. Decrease in silica concentrations with depth. 77
48. Sulfate reduction with depth • 78
49. Location of ground-water samples from Wilcox aquifer used for carbon-14 age dating • 81
50. Location of wells in the East Texas Basin . 84
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
61.
Classification of sandstones from the Wilcox Group . 85
Surface geology of Oakwood Dome showing borehole locations. 90
North-south cross section through Claiborne Group over Oakwood Dome. . 91
Cross section A-A' through Quaternary deposits • . 91
Cross section B-B' through Quaternary deposits . 92
Cross section C-C' through Quaternary deposits .
Relationship between relief and drainage density
Diagram showing source (S) and tributary-source (TS) links
. . .
Source and tributary-source link length distributions for drainage
• 92
96
96
basins overlying East Texas salt domes 97
Source and tributary-:-source link length distributions for non-dome drainage basins in East Texas . 99
Variation of source and tributary-:source links with drainage maturity . 100
.v
62. Inverse relationship between relief ratio and mean exterior link lengths .1 00
63. Location map of lineament study area . 103
64. Rose diagrams of lineaments using total lengths for each 10° sector • . 104
65. Outcrop area of the Queen City Formation in East Texas • . 106
66. Schematic paleogeographic reconstruction of major Queen City facies in the East Texas Embayment • • 107
TABLES
· 1. Physical characteristics of Gyp Hill cap rock • 45
2. List of black-and-white aerial photos used in this analysis . . 53
3. Water chemistry, Duggey's Lake area • . 54
4. Carbon-14 data on profile from Wilcox outcrop through Keechi Dome to southern edge of East Texas Basin . . 82
5. Wells sampled for cuttings of Wilcox sandstones . 86
vi
EAST TEXAS SALT DOME STUDIES -- A SUMMAK Y Uf SECOND-YEAR RESEARCH ACTIVTTIES
Research Staff
Analysis during the second year was highlighted by a historical characterization of East Texas Basin infilling, the development of a model to explain the growth history of the domes, the continued studies of the Quaternary in East Texas, and a better understanding of the near-dome and regional hydtology of the basin. Each advancement represents a part of the larger integrated program addressing the critical problems of geologic and hydrologic stabilities of salt domes in the East Texas Basin.
During the second year of the East Texas salt dome studies, significant advances
in understanding the hydrologic and geologic stabilities of salt domes were based on
the acquisition of much new data. Among these new sources of data are (1) 400 km
(250 mi) of seismic reflection data that are both regional and site specific, (2) gravity
data for the East Texas Basin, (3) 20 shallow boreholes over Oakwood Dome, (4) 1
hydrologic test hole downdip from Oakwood Dome, and (5) a complete core of the
anhydrite-gypsum cap rock over Gyp Hill Dome in South Texas.
The acquisition of seismic, gravity, and electric log data provided new under
standing of the sedimentary infilling of the East Texas Basin and how it caused salt
migration and dome growth. Deposition of the Travis Peak-Schuler sediments caused
the first differential loading of the underlying Louann Salt and the migration of the
salt into anticlinal ridges. Subsequent clastic depocenters occurred laterally to Travis
Peak depocenters and caused further migration of the salt into diapirs. The greater
the sediment loading, the further the salt anticline advanced through Trusheim's (1960)
growth sequence: pillow structure to immature diapir and finally to a mature diapir.
Most domes in the basin can be placed within this dome growth sequence.
Analysis of the Gyp Hill cap rock showed that the cap rock was the result of salt
dome dissolution and the accumulation of the insoluble residuum, anhydrite.
Work completed on the Carrizo-Wilcox aquifer, the major fresh-water aquifer in
the basin, shows that this aquifer has the greatest potential for causing dome
dissolution leading to radionuclide transport. Ground-water circulation is controlled
primarily by topography and structure. Fluid movement is generally downward
because of the structural dip and leakage from overlying units. Chemical composition
of the water evolves from a low-pH, oxidizing, calcium bicarbonate water in the
outcrop to a high-pH, reducing, sodium bicarbonate water deeper in the aquifer. This
chemical change has important implications for radionuclide transport.
1
The Palestine Salt Dome is no longer under consideration as a potential
reposi,tory for nuclear waste because of the occurrence of numerous collapse sinks that
resulted from an earlier brining operation.
To date, studies of Quaternary strata have not found evidence of salt dome
growth during the Pleistocene or Recent.
Drilling of hydrologic monitoring well south of Oakwood Dome.
2
PURPOSE AND SCOPE
Research Staff
The program to investigate the suitability of salt domes in the East Texas Basin for long-term nuclear waste repositories addresses the stability of specific domes for potential repositories and evaluates generically the geologic and hydrogeologic stability of all the domes in the region.
East Texas Basin studies are part of salt dome studies of those interior basins of
Texas, Louisiana, and Mississippi that compose the Gulf Coast Interior Salt Basin. The
East Texas Basin study is one regional element of the National Nuclear Waste Isolation
Program. The U.S. Department of Energy (DOE) intends to choose one salt dome from
the Gulf Coast Interior Basin for a nuclear waste repository. This report concerns the
salt dome program in East Texas and presents some preliminary conclusions reached
during 1979 on dome suitability.
The 1979 program to investigate the stability of salt domes in the East Texas
Basin was divided into three subprograms: (1) subsurfac~ geology; (2) surficial geology,
remote sensing, and geomorphology; and (3) hydrogeology. The integration of the
results of these three subprograms will (1) determine the general suitability of salt
domes in the East Texas Basin for a nuclear waste repository; and (2) identify candidate
salt domes for further, more detailed studies.
The subsurface program was designed to (1) identify pre-Pleistocene growth
histories for domes in the East Texas Basin; (2) explain the relationship of basin
infilling and. salt ~orne growth; (3) map detail~d subsurface geology around the salt
domes; and (4) delineate size and shape of salt domes, depth to cap rock, and depth to
salt.
The surficial geology and geomorphology program was designed to (1) determine
if -the domes have grown during the Quaternary; (2) describe detailed surface geology
over the domes; (3) evaluate the structure of the basin to discover whether any
structural activity has occurred during the Quaternary; and (4) map surface Tertiary
formations and ascertain how they relate to dome and tectonic history.
The primary purposes of the hydrogeology program were to (1) examine regional
ground-water flow paths and (2) assess the potential impacts of salt dissolution on
domes. Studies included regional hydrogeology in fresh-water aquifers, regional
hydrogeology in the deeper saline aquifers, and hydrogeology around domes.
This paper, . a summary progress report, reviews principal conclusions and
illustrates the methodologies used and the types of data and displays generated.
Several topical reports, presenting details of various geological aspects of salt domes
in the East Texas Basin, will be forthcoming as phases of the study are completed.
3
STRATIGRAPHIC FRAMEWORK AND DEPOSITIONAL SEQUENCES OF THE EAST TEXAS BASIN
0. K. Agagu, E. H. Guevara, and D. H. Wood
The stratigraphic succession in the East Texas Basin is composed of sequences of transgressive limestones, chalks, and shale, alternating with regressive fluvio-deltaic sandstones and shales. Six such sequences can be recognized regionally in the basin, but each may contain one or more minor sequences. The first transgressive episode also deposited a thick layer of salt, which was bur.ied beneath 5,547 m (18,200 ft) of sediments deposited in the five other sequences.
Regional subsurface stratigraphy of the East Texas Basin is being studied to
explain basin evolution, tectonic stability, depositional patterns, and local dome
growth and dome stability. The region includes approximately 43,570 km 2 (16,800 mi2)
extending from the Mexia-Talco Fault Zone in the north and west, to the Sabine Uplift
in the east, and to the vicinity of Angelina County in the south (fig, 1).
Stratigraphic analysis is based primarily on correlation of electric log strati
graphic markers in about 2,600 wells in the basin. Forty-nine cross sections were
constructed, and about 50 stratigraphic units were correlated. These cross sections
provide the basis for correlating other wells in the basin. Well log interpretation was
s1,.1pplemented by about 400 km (250 mi) of regional, sixfold, c;:onventional COP
reflection seismic data and both Bouguer and residual gravity maps, which cover the
entire basin.
About 5,791 m (19,000 ft) of Mesozoic and Tertiary strata are preserved in the
central parts of the East Texas Basin. These rocks overlie metamorphosed Paleozoic
Ouachita strata, which are probably a continuation of the Appalachian foldbelt (Lyons,
1957; Wood and Walper, 1974; McGookey, 1975). Stratigraphy of the Mesozoic and
Tertiary strata has been discussed by several authors, notably Waters and others
(1955), Eaton (1956), Nichols (1964), and Nichols and others (1968). A comprehensive
summary of basin stratigraphy is presented in figures 2, 3, and 4. The present
investigations involve six pairs of repetitive, regional depositional sequences in the
basin. Each couplet consists of a lower, dominantly fluvio-deltaic unit of sandstones
and shales that is overlain by shelf carbonates and shales.
The_ Eagle Mills-Louann sequence (Upper Triassic-Middle Jurassic).--This se
quence was initiated by deposition of the undated continental Eagle Mills red beds.
The Eagle Mills red beds are composed of red-brown shales, sandstones, and unfos
siliferous limestones, which are unconformably overlain by the Werner Formation.
4
Lower sections of the Werner consist of conglomerates and fine- to coarse-grained
sandstones that grade upwa_rd into finer clastics and ~vaporhes in the upper part of the
formation. Halite interbeds in the Werner progressively increase volumetrically
toward the top of the formation and are transitional into the conformably overlying
Louann Salt (Nichols and others, 1968).
The Louann Salt consists of white, gray to blue halite with minor amounts of
anhydrite. Upper parts of the formation exhibit some red plastic shales transitional
into the conformably overlying Norphlet Formation (Nichols and others, 1968). The
partially restricted nature of the East Texas Basin. during its initial stages of
formation (Wood and Walper, 1974) provided an ideal setting for large-scale evaporitic
processes, which have not been repeated in the basin.
Norphlet-Bossier sequence (Upper Jurassic).--The Norphlet Formation consists of
sandstones, siltstones, and red shales. The basal part contains halite, anhydrite, and
dolomite transitional into the subjacent Louann evaporites (Nichols and others, 1968).
The relatively thin Norphlet Formation. is conformably overlain by the Smackover
Formation, which documents a regressive phase between deposition of the Louann Salt
and the Smackover Limestone.
The Smackover Limestone here consists of a basal laminated micrite that grades
upward into a pelletal micrite and ultimately into a coated grainstone. The Smackover
Limestone is overlain by and is in part correlative with the Buckner Formation, which
contains red sandstones in the western and northern margins of th~ basin and grades
basinward into evaporites, shales, dolomites, and limestones (Nichols and others, 1968).
The Smackover-Buckner strata document a shoaling sequence from subtidal in the
lower Smackover Limestone to supratidal conditions in the Buckner Formation. The
Cotton Valley Limestone and Bossier Formation are deeper water, gray, micritic
limestones and gray to black shales (NichoJs and others, 1968) that onlap the Buckner
supratidal facies, an indication of a minor sequence boundary above the Smackover
F orma.tion.
Schuler-Glen Rose sequence (Upper Jurassic-Lower Cretaceous).--The Schuler
and Travis Peak Formations attest to the high rate of terrigenous clastic influx during.
Late Jurassic and the Early Cretaceous. They compose a thicksequence (900 m, 3,000
ft) predominantly of sandstones in~erbedded with dull red and green-gray shales
(Nichols and others, 1968). The Schuler-Travis Peak sequence onlaps the subjacent
marine units despite its strongly terrigenous character and is probably an example of
coastal onlap, which was most likely related to the globally rising sea level during the
Late Jurassic and the Early Cretaceous (Vail and others, 1977).
5
The Glen Rose Group consists of a thick (750 m, 2,500 ft) sequence of shallow
marine, micritic, pelletal, oolitic, and shelly limestones interbedded with dark-gray
shales and anhydrites (Nichols and others, 1968). The predominantly calcareous units,
such as the Pettet, James, and Rodessa Members and much of the Upper Glen Rose
Formation, are deeper water facies. Sandy shale units, such as the Pine Island Shale,
and evaporites, such as the Massive Anhydrite, were.deposited during minor influxes of
fine, terrigenous sediment and deposition in supratidal environments, respectively.
Terrigenous facies dominate, espeCially along the north and northwestern flanks of the
basin.
Paluxy-Washita sequence (Lower Cretaceous).--The Paluxy Formation consists of
interbeds of sandstones and shales, and rare conglomerates lie in the northern half of
the East Texas Basin. Basinward, toward the south, the Paluxy gradually changes into
dark-gray shales and micritic limestones (Nichols and others, 1968). The volume of
terrigenous clastic sediment (up to 135 m, 450 ft) and the high rate of deposition
indicate that a major though short-lived phase of fluvial-deltaic clastic influx
occurred. Limestone and shales of the Fredericksburg and Washita Groups in East
Texas document the Early Cretaceous sea-level high that drowned the Paluxy deltas.
Woodbine-Midway sequence (Upper Cretaceous-Paleocene).--Spasmodic uplift of
the marginal areas of the East Texas Basin during Late Cretaceous to Paleocene
times, accompanied by lowering of relative sea level, resulted in the terrigenous
clastic influx mark.ed by the Woodbine and Eagle Ford Groups. The Woodbine Group,
composed mainly of fluvial and deltaic .sandstone and subordinate shales, marks the
peak of clastic sedimentation during this phase. The Eagle Ford Group, consisting
primarily of shelf and slope shales and minor sandstones, documents the waning phase
of clastic deposition.
The Austin Group initiated the transgressive and submergent phase that ter
minated in the Paleocene. During this depositional phase, up to 244 m (800 ft) of shelf
chalks, shales, and marls were deposited with rare clastic facies that define minor
variations in this sequence.
Tertiary clastics.--The Tertiary stratigraphic sequence in the East Texas Basin is
a complex unit mainly composed of fluvio-deltaic sandstones and shales. The Wilcox
Group is a thick (up to 900 m, 3,000 ft) unit of fluvial and deltaic sands, clays, lignites,
and marls that has not yet been regionally subdivided. The Claiborne Group is similar
to the Wilcox Group, but it displays some shaly, glauconitic, fossiliferous shelf/embay
ment units (Reklaw Formation, Weches Formation, and Cook Mountain) that alternate
regionally with more sandy fluvial-deltaic units (Carrizo, Queen City, Sparta, and
Yegua Formations). The entire Tertiary section constitutes the major regressive phase
of the sixth depositional sequence.
6
A SALT COME
SCALE tO IS 20 2SMiles
f---o--'-r---,-1----.--'r----l---' S 10 IS 20 2SKilometers
N
t ~~19 -v·v, DALLAS
ELLIS
R ANGELINA
CASS
( /
( /
I ~d
Figure 1. Location map of salt dome province, East Texas Basin. Stratigraphic cross sections are arranged parallel to regional strike and dip. Dashed sections are presented in this report.
7
ERA SYSTEM SERIES GROUP FORMATION MEMBER
YEGUA w
• z CLAIBORNE w u u - 0 0 >- w
a: N <t -0 - WILCOX UNDIFFERENTIATED
z t-- w a: z w w w u t-- u
0 w·
MIDWAY --' UNDIFFERENTIATED <t a.
UPPER NAVARRO CLAY
NAVARRO UPPfR NAVARRO MARL
NACATO(;H Si\ND
LOWER NAVARRO
il TAYLOR
PECAN GAP CHALK
a:: WOLF CITY SAND
(/) ~I :::> 0:0
' GOBER ww ' CHALK a.U \...-------a.<t
AU:i I" IN ' :::lt-- AC~~AT~~ \ _____ w a: '\~~X~~ u
SUBCLARKSVILLE SAND
EAGLE FORO EAGLE FORD
WOODBINE LEWISVILLE
(/) DEXTER :::> MANESS SHALE 0 r--- BUOA LIMESTONE w GRAYSON SHALE u
~ MAIN STREET LS
<t WASHITA
• t--
~ w u a: ::! - u
FREDERICKSBURG 0 . -~- ----N PALUXY
0 - -- ---(f) UPPER
w GLEN ROSE w (/) ~ :::>
MASSIVE ANHYDRITE ~ rYO z ww
,. RoDEsSA ~
:;:U " LOWER JAMES LIMESTONE o<t GLEN ROSE AND ALE _Jt--
w PETTET (SLIGO) a: u TRINITY
TRAVIS PEAK
SCHULER COTTON
u VALLEY
u a:- BOSSIER wCf> - a.(/) (/) a.<t COTTON '161.LLEY LS. (/) =>a: BUCKNER <t :::> a: ...,
SMACKOVER .:.J ..., NORPHLET
I 'j~ LOUANN
s~ SALT
~~ WERNER
Triassic! EAGLE MILLS
s~ ...JO OUACHITA 1f_N
Figure 2. Stratigraphic succession and nomenclature in East Texas Basin (adapted from Nichols and others, 1968).
8
2000
4000
6000
8000
10000
1200
N.W. Limestone Co. Freestone Co.
500
" "' """ ""-:::,_ "- c~o,k
}"~ " Of IS< 1000
" -~~ " ~- ~~' 'l"- ro ~
~~ .. G!e~
" ~ 1500
" " }(,D o, 'v~_,
1/(_~;.o'"~ ~ ~ 2000
2500
3000
--- ........
4000
" " "
Freestone Co
7 89 10
" \ " \
\ \ \ \ \,
\ \ \ \
'
\ \ ,,
'-__ ,, \ \
\ \ \ \ \
Leon Co
12 13 14 15
Leon Co. l
20 I 16 17 IS 19
Oul
Houston Co.
25 24
Cross Section 4
0 10 Miles
,_,...,....,_~~-'---:>:10:--,15::' Kilomelers
Salt
Coprock nol drown lo horizontal scale
Ver11col Exoggerolion 1:26
wacox
Figure 3. Dip structure cross section through Freestone, Leon, and Houston Counties.
9
S.E.
26
Kaufman I Ca. :
I N.W. I 2 3
500
2000
1000
4000
1500
,.._ 6000
0 2000
8000 2500
3000 10000
3500
12000
Van Zandt Ca. Van Zandt Co
I ', 1'--... ..... , I ~- ' I '--....' I ' I I I I I
t1 1\-..
I A '·, I I~' ',
I I 1 ,, ',..._ I I I ,
I I I , I I 1 '-
1 I I I I
/1 I I /I
I I I I
Smith Ca.
38
Smith Ca. Ru"sk Co.
40 42 39 41
Cross
0
D . Vertical
43 44 45 46 47
Section 17
10 Mites
10 15 Kilometers
Soli
Exaggeration 1:26
Figure 4. Dip structure cross section through VanZandt, Smith, and Rusk Counties.
S.E.
REGIONAL TECTONIC FRAME WORK OF THE EAST TEXAS BASIN
0. K. Agagu, M. K. McGowen, D. H. Wood, J. M. Basciano, and D. W. Harris
The East Texas Basin is framed by basement elements that have persisted since inception of the basin (Late Triassic). PreLouann strata in the· basin are only slightly deformed in contrast to post-Louann strata, which are complexly folded and faulted by salt tectonics. Salt diapirism in the central part of the basin was probably initiated during Late Jurassic by differential loading from Schuler-Travis Penk strata. Salt deformation appears to have started earlier near the basin margin. Structures created by salt movement remained active into the Tertiary. Salt-induced regional structures later influenced rates of deposition, thicknesses of strata, and volume of available salt.
Regional subsurface structures in the East Texas Basin are currently being
mapped to determine the tectonic evolution of the basin. Mapping covers. the southern
two-thirds of the basin from the Sabine River south to the Angelina flexure. From.
well data, structure-contour maps for 6 stratigraphic horizons and isopachous maps for
10 stratigraphic units have been constru~ted. Later, these maps will be extended to
depict the entire region, and, possibly, additional horizons will be mapped. Well log
information is supplemented by about 400 km (250 mi) of regional, sixfold, conven
tional CDP reflection seismic data; Bouguer gravity and residual ·gravity maps are
available for the entire region.
Tectonic elements.--The pre-Mesozoic record in the East Texas Basin is specu
lative. Available evidence, however, points to a Late Triassic or Early Jurassic origin
when the postulated rifting of Pangea separated North and South America to form the
Gulf of Mexico (Lyons, 1957; Wood and Walper, 1974; McGookey, 1975). The locus of
subsidence that produced the East Texas Basin may also be related to pre-rifting
lineaments associated with the Appalachian-Ouachita-Marathon orogeny.
Basement-related tectonic elements in and around the East Texas Basin were
formed early in basin history (fig. 5). Except for som~e speculated gentle downwarping
caused by sediment loading (Turk, Kehle, and Associates, 1978) and some uplift in the
Sabine area (Granata, 1963), the basement has remained fairly stable. Structural
complexity in the central parts of the basin is, therefore, due primarily to halokinetic
movements. Some tectonic elements peripheral to the basin exhibit both diastrophic
and halokinetic origins.
11
--- ------ ------ --- ------------
Boundary elements.--The Mexia-Talco Fault Zone (fig. 5) bounds the East Texas
Basin on the west and north. It is a series of en echelon faults and grabens that
coincide with the updip limits of the Louann Salt. The fault system extensively
displaces Mesozoic and lower Tertiary strata, is also coincident with a subdued scarp
in the basement, and has locally associated volcanism (Turk, Kehle, and Associates,
1978). These evidences suggest that the fault system probably originated as part of a
series of step faults bounding the northern frontiers of the Gulf of Mexico Basin.
Possible downdip flow of salt and subsidence resulting from sediment load accentuated
the Mexia-Talco Faults (more than others) in post-Louann times.
The Sabine Uplift (fig. 5) separates the East Texas Basin from the North
Louisiana Basin. The uplift has been a positive feature probably since the inception of
these basins, as indicated by thinning of the. Louann Salt (McGookey, 1975). The area
has also been spasmodically uplifted, especially during early Late Cretaceous times
(Granata, 1963). No direct relationship appears between activation of the Sabine
Uplift and salt tectonics. The isopachous map for the Maness, Woodbine, and Eagle
Ford sequence (fig. 6) suggests that the Sabine Uplift was not a source of clastics even
during development of the pronounced post-E.agle Ford erosional unconformity.
The Elkhart Graben-Mount Enterprise Fault System (fig. 5) is a zone of faulting
that bounds the East Texas Basin on the south. The fault zone trends northeast
southwest through Rusk, Cherokee, Anderson, and possibly Leon Counties. This trend
is coincident with a buried hinge line that is subparallel to and north of the Angelina
Caldwell flexure (Nichols, 1964) (figs. 5 and 7). This hinge line is the southern limit of
the East Texas Salt Dome Province. Pre-F.oc.~nP se-rliments are thickest north of the
hinge, whereas post-Eocene depocenters are thickest south of it.
The Elkhart Graben-Mount Enterprise hinge line probably is a structurally
elevated, relict shelf edge. Post-Louann sediments have squeezed mobile salt from
the East Texas Basin southward to produce a faulted uplift similar to the linear ridges
on the slope and rise in the Gulf of Mexico (Antoine and others, 1967). This view is
supported by the presence of a prominent gravity minimum along the graben. Two
deep-seated salt uplifts, Elkhart and Slocum Domes, also occur along the system,
probably as a result of second-order sediment thickness variations. ·
Basinal elements.--The entire East Texas Basin was underlain b.y the Louann Salt.
The original tabular salt layer was initially deformed into a complex array of salt
ridge~, troughs, pillows, and piercement features. All post-Louann sediments are
consequently affected; pre-Louann sediments are, however, relatively undeformed
(fig. 8).
12
--
The East Texas Basin can be subdivided regionally into a western subbasin
trending north-south and two eastern subbasins trending north-northeast - ·south
southwest (fig. 7). This basin structure is displayed on all the mapped horizons (Lower
Cretaceous to Upper Cretaceous). Subsidiary elements, principally salt domes in
Henderson and Anderson Counties, further subdivide the subbasins. Marginal areas of
the basin are characterized by relatively consistent and more gentle basinward dips
compared with the central parts of the basin, where the principal salt domes are
concentrated.
In the southern part of the basin, regional thickness trends of Upper Cretaceous
to Tertiary sedimentary units (figs. 7 and 9) conform closely to st~uctures developed
by salt movement. Generally, the main depocenters are the regional, halokinetic
synclines; the flanks of the depocenters, which received thinner sediments, are sites of
halokinetic anticlinal axes. As expected, the terrigenous clastic and chalk units
conform to this salt distribution pattern, but in some areas, thick sequences of . .
carbonates appear to . have developed on paleotopographic highs (overlying salt
anticlines) probably by reefal build-up and related processes (fig. 10). The western
syncline was somewhat less active in Late Jurassic and Early Cretaceous times.
Salt mobilization started early in the history of the basin. In the central parts of
the basin, salt-induced sedimentary thickness variations are noticeable only in the
Cotton Valley Group and the younger strata (fig. 8). Before that time, post-Louann
deposition in the central parts of the basin had been composed principally of marine
limestones and shales that would have exhibited planar stratal geometry because of
deposition on the undeformed substrate. Subsequent clastic influx during deposition of
the Schuler and Travis Peak Formations, on the contrary, would have exhibited thick
and sandy (denser) delta front facies -- a density imbalance that may have initiated
salt movement. Burial of the Louann Salt by about 1,524 m (5,000 ft) of Norphlet
Cotton Valley Limestone sediments would also have created higher temperatures and ·
pressures, which would have enhanced plastic deformation.
13
T E X A S
' \
~ I I
\ ' \
0
0
\ ' .....
50
80
I I
(
Figure 5. Megatectonic elements around the East Texas Basin.
14
100 mi
160 km
N
,-------· --· .. ----HUNT
wooo
Hainesville A
ELLIS
NAVARRO
HOUSTON
\ I
EXPLANATION
! ::: :11200'-1400' • > 1400'
• Salt dome • Well control
Datum: Sea level Contour interval: 200'
SCALE 10 15 20 25 Miles
0 5 10 15 20 25Kilometers
HARRISON
ANGELINA
Figure 6. Isopach map of combined Eagle Ford, Woodbine, and Maness Formations. Stratigraphic pinch-out around the Sabine Uplift is not accompanied by any major clastic influx of eroded sediment.
15
EXPLANATION
.a. Salt dome • Well control
Datum: Sea level Contour interval 250'
SCALE 10 15 20 25Miles
0 5 10 15 20 25Kilomerers
REO RIVER
BOWIE
CASS
I _j_ __ _
.. '..., . · .. (
ol ,........._
.I -,._ UPSHUR
I
~-1 . _i'. II
_./' • HARRISON ___.-- • • I
- GR~GG •••• I
.·
I
L, ELLIS
------r--;-:--· ____ ___,
/ ( l ' I I
L_
Figure 7. Main structural trends in the East Texas Basin, indicated by structural configuration on top of the Pecq.n Gap Member of Taylor Formation.
16
f
NW SE
Figure 8. Seismic section through Van Zandt County. Main depositional axes define persistent structural troughs owing to salt withdrawal into intervening anticlinal area(s). · Thickness variations indicating salt movement become evident in Schuler/ Travis Peak time (A) in the central parts of the basin. Movement could have been initiated earlier near the margin of the basin (B). Seismic line courtesy of Teledyne Exploration Company.
17
DALLAS
ELLIS
---~/~ ·. \: 0 ••
' ..
~\.
\ '
0 '
LIMESTONE O • :·\
\0 . \;-'y''
-~-'
HUNT
EXPLANATION
IY'i:iftl 14oo'-1soo' • 1soo'-1aoo'
& Salt dome • Well control
Datum: Sea level Contour interval: 200'
SCALE 10 15 20 2~ Miles
5 10 15 20 25Ki1omeTers
I -~-:r--1 I I "'--'- ' _../- I HARRISON
'-'\. ,j',..._..,., _..--- I
- ------·l.,.f-1 - I GREGG
I I
I L I '"'-----r-
1----~--~ / o'
'
6 e,ua,d o ! ( ',....C.-~:-0---'-r;--o •o o o -l OR~SK /
0 ° ). :< :-0
0 i \ :
000 0 0
:
0
0 ° 0r 00 0 L_ 0
1° 0 0
0 ~----, ~-----oj o •
0·~·.
· ... CHEROKEE
NACOGDOCHES
ANGELINA
Figure 9. Isopach map of Pecan Gap Member, Lower Taylor Formation, and Austin Group.
18
HUNT
ELLIS
LIMESTONE
\ \
EXPLANATION
WH///(#4 Chalk and Shale
:;;.'lJ/::;!:;;'0:'"-'2~ L1meslone and Shale ~''~~~ Sandslone and Shale
A Soli dome Dalum' Sea level
SCALE
i--,-.L.,--,ii0-,--'15:,..-_:2J:_O _ _jz~ Miles
10 15 20 25Kilometers
RUSK
( / ( I
) I I
L_
NACOGDOCHES
Figure 10. Major depositional axes in East Texas Basin. Depocenters coincide with positions of structural troughs in figure 7, especially in sand/shale and chalk/shale units.
19
EVOLUTION OF EAST TEXAS SALT DOMES
Alice B. Giles
Salt domes in various stages of maturity in the East Texas Basin can be recognized from analysis of the geometry of the domes and the strata surrounding them.
Salt dome evolution entails the domeward migration of the area of salt
withdrawal (fig. 11) (Trusheim, 1960; Kupfer, 1970). The area of salt. withdrawal is
made apparent on cross sections by the thickening of sediments deposited during the
time of withdrawal. The structure that accommodates the thickening is termed a rim
syncline.
Immature salt domes are characterized by rim synclines that are relatively
distant from the dome crest such that strata thin toward and dip away from the dome.
The rim synclines of mature salt domes have migrated to the dome edge; therefore,
younger strata thicken and dip toward the dome. Thickened beds adjacent to mature
domes indicate substantial flow of salt into the dome and possible pinch-out of the salt
source. Consequently, additional sediment loading should not promote further dome
growth.
Numerous deep, nonpierdng salt pillows occur in tbe East Texas Basin and
represent comparatively immature salt structures (fig. 9). Shallow salt domes in the
basin, however, exhibit various degrees of maturity.
Keechi, Bullard, and Whitehouse Domes are in an intermediate stage of maturity·.
Although these domes have risen to shallow depths, surroundmg strata thin tuwar Ll diiLi
dip away from the domes (figs. 12, 13, and 14), an indication that more pillow salt is
available for additional growth. The conical shape of these domes al.so indicates that
more sediment loading of the flanks of the domes would cause additional dome growth
(fig. 15).
Grand Saline, Bethel, and Hainesville Domes are more mature domes and are
isolated from an additional supply of salt. The rim syncline has migrated to the edge
of these domes, as indicated by the domeward thickening of strata (figs. 16, 17,
and 18). The early (pillow) stage of dome growth at Bethel and Hainesville Domes is
reflected in domeward thinning of Lower Cretaceous strata (figs. 17 and 18); the
pillow stage at Grand Saline Dome must have ended by Fort Worth-Paluxy time
(fig. 16). The cylindrical to mushroom shape of these domes also suggests that salt has
been withdrawn from the area around the bases of the domes (fig. 19).
20
---------------------------- -----------------------------
~··~other'' salt~
Figure 11. Schematic evolution of salt diapirs (modified from Trusheim, 1960).
21
N N
400
200
MSL feet
-200
-400
-600
-soo
-1000
-2000
-4000
-5000
100
meters
-100
-200
-300
-400
-500
-1000
-1500
N
/oCC)~'OR~ t'SALT DOME\
I • • • · · · • \
Figure 12. Texas.
CLAiBORNE --
• SAM='LE LOG
0 l--~--'25=00.::,.._..:5.::.0001t 0 500 IOOOm
VERTICAL E (AGGERATION 5.9•
NAVARRO • II GREENWOOD PRODUCERS
NAVARRO II BARPETT AND 12 • PRODUCERS
I ~~g~~
~
'I \ :::::::::::::::::::::::::::::: ~: ~: ~: ~: ~: ~: ~: ~:: \ \\\ .·.·.·.·.·.·.·.·.·.·.·.·.·.·.·.·.·.·.·.·.·.·.··\ \
FARISH m #I WAITS
····••••••••••••••••••••••••••••••••••••••••••••••••• \ \\\" L: <::::::::: :::::::::::::::::::::::::: <::::: ::::::::1 \\\ ·~ '----- ---
TOP OF MIDWAY
s
OLSAN II JOROAN
EXPLANATION ' '---._ ---- ----
~ CAP ROCK '-."-._ , -..___ ~USTIN CHAL;;--
D SALT "--.._ ---- -
Ground-water total dissolved solids (ppm) estimated from electrical logs
~Jill] <1000
~ 1000-3000
lillili]] •3000
---- ---- £AGlf;: FORo . -
North-south structure section through Keechi Dome, Anderson County,
w
500
400 100
200
MSL
200
100
I 400
600 . 200 :::::
800 <::: :::::
1000 300 ::::: ..
if, #
500~ 2000
N I.N
3000
1000 <
4000
-=-\
5000 1500 ~
~ ~ . ~-~ .... ....
~ ~
''' ,, '"''~ TOP OF EAGLE fOI'-O
TOP oF woooel~'-~t.
Figure 13. West-east structure section through Bullard Dome, Smith County, Texas.
E ~
~ -~
"'" "" :::~ i
N -@- -¢- -¢-·S ·:>- ~ -¢- -¢- !:!
~ -¢- ~
~~ ! ~ :;: .,:;. z~ ~ ~~ ::a z..;:: w::, zl:
i~ o::! ~i
~· .,,
~i z" :r~ ::> " ::>
/~::::::::::::::::::::
lil----!lll-- __ !PE. Qf ~C_AN~/ll' _- - --fl!.------l!l.----------:---{jf
:;:>sAJi:io~~:;:;::\ 1 I
:::::::.u:.u:·u::u.·:l \\ , UU:HHHHHH A~t---~--~~~~B!L--:J----JL--------==:I~
.:::::::::::::::::::::::::::::::::,
k---.ji!F=::=:::jjf,-;-:_K,_::I~':MlC~~' 1
\:::::::::::::::::::::::: ·:::::::::.: i ·,:::::::::::::::::::::::::::::::::::
f~\ BULLARD s~~1}·~~E
~:.:.:.:.:.: ·\
EXPLANATION
Ground-water to;ol dissolved solids (ppm) estimated from electriool log•
1 m :1 < 1000
l&f~ 1ooo-30oo
H@tW.@~~~~ > 30oo
Dome shapes fr-Jr"' 'lletherland , S3well and Aosociotes ( 1976)
j:::::::::<:l Salt
- Coprock
Vertical exaggeration • 5.9
• Sample log
rf Normal fault
2500 5000 fl
0 500 1000 1500 m
-¢- Ory well -@-Water well e Oil well ' -!:)-Gas well
Figure 14. North-south structure section through Whitehouse Dome and the east flank of Bullard Dome, Smith County, Texas.
Ft
MSL
4000
8000
t2POO
t€,000
20,000
•
-----------------------
M s N
1000
2000
3000 KEECH I
4000
5000
t Modified from Exploration Techniques ,Inc., 1979)
------------------- -
w
( Mnrlifif!rt frnm t\latharl('lnd , Sewell and Associotes,l976)
E w
{Modified from Netherland, Sewell and Associates, 1976)
(J bUUUI-t
0 1500M
Figure 15. Domal sections with no vertical exaggeration. Black area indicates approximate cap rock. Cap rock on Whitehouse Dome is relatively thin .
25
E
NW
~ ~
?i~ ~~ ~"" u
fl m 400
200
MSL
200
400 100
600 200 BOO 1000 300
400
500
2000
3000
1000
4000
1500 5000
6000
2000
TOP OF
TOP OF
~ ~ s ... II\ 'II
WILCOX ---
UPPER NAVARRO MARL
PECAN GAP CHALK
* ... ~ -!l
* "" (/)~ § ~ ...J~ _,§
~~ ...J~ !z~ i>:'< ...JC::. ,__, 2' w, <l'
8"" ~"" """ >-'II !!J a::
~ u ID
-¢·
................ 1
~ }- -~0,w~c:~~~---- ______ _ \.·.·.·.·.·.·.·.·.·.·.·.·.·.·.·.·.·\
~ <••<>•••II --~:·:.::::::·:::::::::::::::.-.::::.r-
\:::::::::::::::::::::::::::::::::::1
--\ ••••• GRAND. SALINE ••• ·~ :::::::::::: :6~~~::::::::::::: 1 ·.·.·.·.·.·.·.·.·.·.·.·.·.·.·.·.·1
:::::::::::::::::::::::::::::::::::1
t[·::[[[:[[::_·.:::· __ ::_:·:::::::l -- j::::::::::::::::::::::::::::::::: l C)Af>-~----
--='---L.'ll...... \<:<:<:<:::::::::::::<:::\ '---..Q.~ o= p..~Jl-.:.--
~))))):///1 EX::ION _..._..._... . \:::::::::::::::::::::::: :>::::::1 '·'·\'~ (............................... ~~1r4~1t~ Cap rock
r,///):///:~ [J Soli
t \ :~:;:,, \ · · · · · · · · · · · · · · · · Ground· water total dissolved solids ::::::::::::::::::::::::::::::::) (ppm) estimated from electric logs
:::::::::::::::::::::::::::::::1 m:m;::::::l < 1000
\1 ::::::::::::::::::::::::::::::: j ..Q- Dry well
e Oil well
\~Normal Foul!
1
:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.: 'I J!!!ll\\lm:.'!l~ooo- 3ooo
::::::::::::::::::::::::::::::::1 lillTITIB
1:<<<<<::<:::::, • >3000 o.__.,.:2::5;::.oo:.,_...:5:.:;ooo 11 0 500 1000 1500 m
Figure 16. Northwest-southeast structure section through Grand Saline Dome, Van Zandt County, Texas.
SE
I; ~·~ ~ -~
"' Ill(; "' <tl!! ii; ::0' z,
a:: 'II "'"" w ~ {>
()'"
11
0
.....
c:()'
Q
::l
c:
.-+
..,
'<
(l)
~ -!!:
:;
(l) ><
Pl
VI
z 0 .., .-+
:T
~
(l)
VI
.-+
I VI 0 c:
.-+
:T
(l
) Pl
VI
.-+
VI
.-+
.., c:
()
.-+
c:
N
..,
'-I
(l)
VI
(l)
()
.-+
c;·
::l
.-+
:T
.., 0 c:
()'Q
:T
0'
(l)
.-+
:T
(l
) .......
0 0 3 (l) >
::l
0.
(l) .., VI 0 ::l
6 b 8
~!jj~
1< ~ ~
~ ~
~ 0 1>
.
"' "'
g
I g ~
~ • !!,
+
-¢- 3 ~
I I
I I
I I
I I
I I
<
I I
!~l:
l/
s"' g
I I
u ~ /I
"'
-I
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I I
\ ""' ~ \~ ~~ ~ \ \
\
N §
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§ 8§
8 N
;:
N
0<
1>
0
0 ..
. 0
8=
~
* TID
EW
ATE
R
NO
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ltJm
py
TID
EW
ATE
R
• #
10
Lul
lerl
oh
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ATE
R
#9
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lerl
oh
RIC
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Y
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de
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rren
tine
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EN
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s
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iam
s
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E
0 #2
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i-St
one
0 FE
NIX
6
SCIS
SON
S #
3 T
exas
Util
itie
s F:
.~e/
ca
·
HU
MB
LE
#I
Link
CO
NTI
NE
NTA
L Il
l R
uyol
Nal
iono
l B
onk
MA
GN
OLI
A
#I
Pug
h
()"T
T
0 ...
.. cO
Q
:::l
c r+
..,
'<
(b
-l;x
; (b
•
><
Ill z
~
0 .., r+
:r
~
(b
Vl
r+
I Vl
0 c r+
:r
(b
Ill
Vl
r+
Vl
r+ .., c ()
r+
c !'
..)
.., 0
0
(b
Vl
(b
()
r+ a· :::
l
r+
:r
.., 0 c ()Q
:r
:c Ill .....
:::
l (b
V
l < ..... - -(b 0 0 3 (b
~
0 0 0..
I \ \ \
§~§8§~88::
1 I
I I !I
1 I
I 'I'' I
I
(/)
fTl
Ft MSL
2000
4000
6000
w E w E w M
"00 \ ) BETHEL GRAND SALINE
HAINESVILLE
0 2000 4000Ft 2000
I I I t I ' / \
0 500 tOOOM \ I
Figure 19. Domal sections with no vertical exaggeration. Black area indicates approximate cap rock. Grand Saline and Hainesville Domes have relatively thin cap rocks.
29
E
HYDROLOGIC STABILITY OF OAK WOOD DOME
Graham E. Fogg, Charles W. Kreitler, and Shirley P. Dutton
Oakwood Salt Dome apparently is in direct contact with the Wilcox aquifer. However, salinities observed around the dome do not indicate significant" dome solution. Programs to evaluate dome solution include drilling, ground-water modeling, and petrographic studies of cap rock.
Oakwood Dome apparently is in direct contact with the Wilcox Group, a major
fresh-water aquifer. The dome is probably vulnerable to salt dissolution, as suggested
by Kreitler anq others 0978, fig. 6), who noted that maxill)um salinities in the Wilcox
aquifer increase from 2,000 to 8,000 ppm toward the dome. In every case, however,
salinity anomalies occur in a thin, f"':lUddy sand layer near the base of the Wilcox Group.
Because of low permeability and transr:nissivity in this muddy layer and its separation
from upper, clean aquifer sands by 30 to 90 m (100 to 300 ft) of laterally continuous
mudstone, the salinity values probably do not indicate significant dissolution rates.
Aquifers composed of clean sands higher in the Wilcox should have the greatest
potential for dissolving salt, yet salinity values estimated from electric logs (fig. 20)
and measured in water well samples from these sands document a general absence of
salt dissolution. Figure 20 shows anomalously high salinities near the updip flanks of
the dome and in an elongate plume that extends to the northeast and contains 2,000 to
4,000 ppm dissolved solids. If these sands are in contact with the dome, then the
observed salinities are unexpectedly low, since water in such sands should be almost
saturated with sodium and chloride (approximately 300,000 ppm) near the flank of the
dome. Furthermore, according to the regional hydraulic gradient, any saline plume
should extend down gradient to the southeast of the dome. Here, however, the Wilcox
aquifer does contain such saline anomalies (fig. 20).
Three conditions may be responsible for the apparent lack of· salt dissolution at
Oakwood Dome. First, the cap rock may protect the salt from circulating ground
water. Second, near-dome facies changes in the Wilcox may cause permeabilities to
decrease toward the dome. Third, high salinities around Oakwood may be diluted by
abundant recharge of fresh water over the dome and by subsequent mixing and solute
dispersion.
If the dome formed a topographic high during Wilcox deposition (Agagu, 1979,
personal communication), Wilcox facies may have become muddier near the flank of
the dome, as several electric logs near the dome indicate. Although geophysical logs
recently obtained from the drilling program in hole 2A (located about 610 m, 2,000 ft,
30
southeast oi the dome flank) reinforce this idea by showing .that the Wilcox is
relatively muddy, the evidence is inconclusive.
Recharge directly over Oakwood Dome may be greater than in surrounding areas,
as suggested by hydraulic heads that appear to increase toward t~e dome in both the
Wilcox and the Carrizo aquifers. Such an increase in recharge could be caused by a
combination of three factors: (1) the area over the dome is a regional, topographic
high; (2) the Wilcox and Carrizo are uplifted slightly over the dome so that the aquifer
crops out in a small recharge area over the dome; and (3) the uplift. has produced faults
and disrupted aquitards.
Three ongoing prograJ1lS are designed to evaluate the causes for the absence of
salinity anomalies around salt domes and Oakwood Dome in particular: (1) a drilling
program at Oakwood Dome to evaiuate distribution of hydraulic head, water chemis
try, and aquifer/aquitard lithology and permeability; (2) a numerical ground-water
modeling program to analyze the complexities of ground-water flow and solute
dispersion induced by dome geometry and uplift, recharge over the dome, topograph
ically controlled recharge and discharge, and aquifer/aquitard lithologies; and (3) cap
rock evolution studies to determine characteristics of dome dissolution through
geologic time and the ability of the cap rock to isolate the salt from circulating
ground water.
31
e9Ci0t~oo 980/700
EXPLANATION
• 7501300 1060/500
G20/400
100/150 • 750/400
1060/400
280/500 • 660/500
1140/600
320/700' ... ---- ........ 930/600& .....
13~0/1700 ~JQ';~g(i', , &1100/600 ',
I 1540/3500 '
I ' I ' I • 4601700 I 1580/1300
N
I ' 1100/600• I 95°30' I
' . 14801600 .
"ot
~ v. "0',
G70/600 •12301700
1650/1000
"" 01'~,.. 11,"'
96°00' +31°35'
I + 31°35' I I CZ/300 1
I & 5301800 I 130011700 /
I CZ/200 1800/3500 Aoot900 I 8201600 I , ~ •13801900
1 130012200 ,' / 15001900 I CZ/200 & 1710/1200 c,O/
I G00/100 & ~«./ ' I 1380/2000 ·e;,'l.~·
1750/1000 1880/4000 ~~o/o~ v· I 1550/1300 ~ "',y
I 178013500& Q5 /'/' I CZ115o' ~o',1~~
I -{6901700 •1150/700 CZ/150--TDS in Carrizo
650/800 1600/600•
2060/700 I OAKWOOD/ 138011200 18001600
1160/400 195011500 1460t5oo• DOME "
I 90011200 / ~ ,
• 460/500} Depths and TDS respectively 1350/500 for Wilcox Sands 1900/600
CZ/200 & Indicates presence of anomalously high TDS I ~ 1330/600
1700/600• 1990/900
~~~g~~gg.
lmi
0 Deep hydrologic drill site
I ~ 2 CZ/60 ~ 0 1950/600
1050/700& ~~ 170011500 CZ/150
2330/10,000 ~ ,
/ / ~~ CZ/250
• 7001700 1600/600 2000/900
~'f/;~88•
y~ ,' /i ~'
CZ/150/ -' , 53ot5oo 96° 'bo·
/ 1480/300 ., + 310 30' / • 1900/700 ,
CZ/700 , 6501700 ., CZ/400 1410/1000& ,
1750113.20.,, ·~~g:~gg 1710/400
CZ/300 13~6~s~8 • 1850/300 730/400
el600/400 2080/600
CZ/300
CZ/150
·~~~~~~ 1950/900
CZ/240
·~~~~~<£ 1830/700
• 700/600 1160/700 1920/600
cz 1150 700/150
.1490/500 20201700
9201700 •1700/800
2070/1000
CZ/400 970/600 1370/600 CZ/300
450/700 760/500
•1560/400
•1970/700 CZ/300 • 710/600
1670/400 1960/600
1190/900 95° 30' •1430/500 + 310 30'
1900/600 • CZ/I50
CZ/180
CVIiQ
~~~'f/;~88· 19101700
~~5~~88• 1390/500 18501500
cz 1150 • 500/600
1050/800 1770/600
CZ/190
l~gg:~gg.
l~g~~~· 1850/600
2060/500
CZ/240 • 560/600
1400/700 1770/500
ft<Po' i28o 1890/800
CZ/150
·~~~g~;ss 1900/600
CZ/200
·~~~gjj~~ 1990/800
680/400 ·I~IUI<\00
2060/600
2030/600 CZ/150 630/600e
1340/800 1960/700
CZ/1~0 •520/700
1450/600 2000/600
CZ/<150 •930/c;lOO
P.>BlJijUU 1900/900
CZ/150 • G00/400 1420/400 18001700
CZ/150
~~g~'j88• 1980/600
CZ/500
7301700 • el030/700 1480/600 1480/600 1800/900 1800/900
880/1100 1500/1100& 2100/600
Figure 20. Ground-water salinity estimates in the Carrizo and major sands of the Wilcox. Anomalous salinities are found close to the updip flanks of the dome and in an elongate plume extending to the northeast.
32
DRILLING AND HYDROGEOLOGIC MONITORING AT OAKWOOD SALT DOME
Graham E. Fogg
A hydrogeologic drilling program at Oakwood Dome was designed . to evaluate the three-dimensional distribution of salinity and other chemical parameters, hydraulic gradient, aquifer/aquitard framework and permeability, and salt/cap rock characteristics.
On the basis of preliminary hydrogeologic studies at Oakwood Dome, a drilling
program has been designed to provide the following information:
(1) Distribution of ground-water chemistry, including carbon-14 age dates;
(2) Hydraulic gradients and aquifer permeabilities needed to calculate ground
water velocity fields;
(3) Geologic framework, including distributions of aquifer heterogeneities and
their associated heterogeneous permeabilities to provide an understanding of mass
transport phenomena;
(4) Values of radionuclide adsorptive coefficients;
(5) Salt/cap rock characteristics;
(6} Fluctuation of long-term ground-water levels in response to recharge and
vertical leakage across aquitards.
The drilling program was originally designed to include four well clusters located
in each quadrant flanking the dome (sites 2, 3, 4, and 5) and a salt/cap rock core hole
located directly over the dome (site 1) (see fig. 20). Sites 2 and 4 are located nearly
parallel to the regional hydraulic gradient. Consequently, because of the regional
hydraulic gradient, site 2 is located for sampling salinities immediately downdip of the
dome. Well 2A, at site 2, which was completed in 1979, verifies existing electric log
data. documenting that, contrary to the regional hydraulic gradient, salinities im
mediately down-gradient from Oakwood Dome do not increase noticeably as a result of
any salt dissolution. Site 4 is located so that it will provide background data that are
unaffected by the dome. Site 3 is situated off the west' flank of the dome where
hydrologic data are sparse. Site 5 is positioned for an investigation of the
saline/brackish ground-water plume that extends northeastward from the dome.
Each well cluster was designed to consist of eight wells: · four production wells
and four corresponding observation wells screened in various parts of the Wilcox
Carrizo system. The sequence of drilling at each site was as follows: (1) drill one e deep-pilot hole through the Nacatoch Sand (at about 900 m or 3,000 ft), and core 30 m
(100 ft) of Nacatoch Sand; (2) plug back to the Wilcox, and complete as a production or
33
observation well in a lower Wilcox Sand; and (3) drill the other seven wells at short
spacings from the pilot hole, and complete in zones determined from geophysical logs,
cores, and cuttings collected in the pilot hole.
Pumping tests lasting at least 24 hours were programmed to provide water
samples and measurements of aquifer permeability and storativity in each production
well. Maximum testing efficiency can be achieved by high-quality well construction,
fully penetrating wells, and draw down measurements in both production wells· and
observation wells.
The Wi.lcox aquifer was cored at site_ 2 in 1979. Analysis of the Wilcox core is
intended to provide the following information: (1) nature of depositional environments
and permeability of respective facies as related to dome growth history, (2) values of
radionuclide adsorption coefficients, (3) sedimentary geochemistry and mineralogy, ·
and (4) resource potential of deep lignite-bearing strata.
At site 2, monitoring wells at three diiferent depths and the Wilcox core were
completed. At site 5 and at the salt core site, wells in· the Carrizo aquifer were
completed. In addition to these wells, 10 shallow piezometers have been installed in
the Carrizo and Queen City Formations.
Because of funding cutbacks from the Office of Nuclear Waste Isolation (ONWI),
the number of wells in the monitoring program was significantly reduced. Funding
cuts will greatly reduce the capability to interpret the hydrology around Oakwood
Dome, or around any dome in the East Texas Basin. Available· information will be used
to develop the best, but an incomplete, picture of salt dome dissolution. Hydraulic
heads ln all welb, i11duJit'1g tho3e containing !ihnllow piezometer5 in thl;' Ql.!f;-Pn \.ity
and Carrizo aquifers, will be measured continuously over a 2-year period to provide
boundary conditions needed to develop numerical ground-water models with which
most of the hydrogeological data will be analyzed.
34
AQUIFER MODELING AT OAKWOOD DOME
Graham E. Fogg
Aquifer modeling by numerical methods is being used to analyze hydrogeologic conditions around Oakwood Salt Dome. A preliminary test model that considers only the effects of the dome itself on a three-dimer;sional flow field shows very local deflections of ground-water flow lines.
Aquifer modeling by f}Umerical methods is being used to analyze the hydrogeo
logic system near Oakwood Salt Dome. Current efforts are addressed to construction
of a detailed ground-water flow model. TERZAGI, the flow modeling program being
used, employs. an integrated finite difference, mixed explicit-implicit numerical
scheme for solving problems of one-, two-, or three-dimensional fluid movement in
fully or partially saturated porous media with vertical consolidation in the saturated
zone. The theory behind TERZAGI, a description of its algorithm, and its applications
to problems can be found in literature describing its two related programs, TRUST and
FLUMP. TRUST, described by Narasimhan and Witherspoon (1977 and 1978) and
Narasimhan and others (1978), is identical to TERZAGI, except that it includes
vertical consolidation in both the fully and partially saturated zones. FLU MP,
described by Fogg and others 0979), Narasimhan and others (1977), Neuman and
Narasimhan (1977), and Narasimhan and others (1978), was developed from a version of
TRUST by replacing the integrated finite difference matrix generator with a "finite
element matrix generator. TERZAGI was chosen because it is a flexible program
which yields accurate answers to complex problems.
A preliminary simulation of flow through the Wilcox-Carrizo system, including
the effects of the dome geometry on the three-dimensional flow field, has been
completed. The purpose of this exercise was to discover how the dome itself affects
flow patterns; consequently, it is a greatly simplified analysis. The three-dimensional,
integrated finite difference (IFD) mesh is shown in figure 21. The radial node
arrangement was chosen because it is an efficient, easy means of closely spacing nodes
near the dome, where greater accuracy may be required because of abrupt changes in
hydraulic gradient. Only half the dome area was modeled because the simple
formulation of the problem makes it geometrically symmetric. The three layers used
in the mesh do not represent lithologic layers, but are included to represent the
vertical arrangement of the Wilco"x-Carrizo aquifers around the dome and to allow
vertical fluid movement. Transmissivity of each layer is one-third the total
transmissivity of the Wilcox-Carrizo system, ·as estimated from pumping test esti-
35
mates of hydraulic conductivities in the East Texas Basin and average sand thicknesses
estimated from electric logs located in the Oakwood Dome area. Regional dip of the
aquifers is taken into account by tilting the mesh at an angle determined from electric
log correlations. Boundary conditions are prescribed head on the updip and downdip
margins and prescribed (zero) flux on the lateral boundaries.
Hydraulic heads computed by the model (fig. 22) show that the dome causes only
a local deflection of ground-water flow lines, both vertically and horizontally. The
general absence of vertical movement is shown by the fact that heads in each layer
plot directly on top of one another except against the downdip flank of the dome,
where heads in the upper layer (shown as dashed contours) are slightly higher than
those in the lower two layers. Finer contour spacing would show a similar vertical
gradient directed upward on the updip flank. Nevertheless, vertical flow rates
computed by the model show vertical upward flow from the lower two layers to the
upper layer along the northwestern flank of the dome to be 181 m3 per day (53 acre-ft
per year), or twice the value for the entire northern flank. Flow magnitude is exactly
the same along the southern flank, but flow direction is reversed. Values are virtually
unaffected by truncation errors induced by the numerical scheme, since the maximum
error in mass balance at nodes surrounding the dome was only 0.5 m3 per day (0.15
acre-ft per year).
Vertical flow rates are a small fraction of the lateral flow rates; however, they
may be significant to solute transport. On the other hand, vertical upward movement
may be nullified or reversed by recharge occurring over the dome and/or by permeabili
ties t~at are anisotropic with the maximum permeabilities oriented along the
horizontal plane. The Wilcox aquifer, because of its mode of deposition, is most likely
anisotropic on both lithologic and pore scales. Despite its lack of detail, the model
provides information with which to plan test drilling and subsequent modeling.
The next step of the modeling program will incorporate all relevant aspects of
the flow systems in the Oakwood Dome area. These aspects will be determined as the
model is built and tested and more data are collected through drilling, testing, and
· monitoring. The following factors of potentially major importance will be included in
the model:
(1) Three-dimensional permeability distributions, including effects of sedimen
tary facies patterns anq the structural fabric;
(2) Variations in recharge and discharge caused by effects of topography; and
(3) Vertical fluid movement within aquifers and across aquitards.
Boundaries of the model will be extended to potentially important recharge and
discharge areas in the region around Oakwood Dome.
36
Heterogeneous permeability distributions around Oakwood and Keechi Domes are
being studied through graphic correlation of electric logs, as shown in figure 23. Sand
body distribution in the Wilcox Group is being used to subdivide the unit into
hydrogeologic facies. On the basis of this work, maps of net sand, muddy sand, and
clay/shale have been completed for three separate layers· in the Wilcox within a 16-km
(10-mi) radius of Oakwood Dome. Existing data provide the geologic framework, but
can only be valid input into the model with good permeability estimates of the various
facies. The drilling program is designed to provide this information through pumping
tests and analysis of core samples. Core samples are also necessary for validating
interpretations now being made solely from resistivity logs.
Macroscopic solute dispersion in the Wilcox aquifer is caused by the types of
heterogeneities shown in figure 23. For years, hydrologists, through the use of a
coefficient of dispersivity in a solute transport equation, have been attempting to
describe the effects of aquifer heterogeneities on ground-water flow. However, the
dispersivity is scale dependent and can seldom be measured on a scale that is
representative of most solute transport problems. Existing methods for predicting
dispersion are inadequate. Currently, research is being conducted to study ways of
analyzing the dispersive qualities of the Wilcox by a statistical characterization of its
heterogeneities as indicated by hydrogeological borehole data and depositional sys
tems. Much of this effort is based on the work of Schwartz 0977), who uses
deterministic flow models to analyze the effects of hypothetical aquifer hetero
geneities on dispersivity, and Neuman (in press), who discusses the work of many
authors on characterization of aquifer heterogeneities.
37
' . • •
•
•
•
]Dome
• •
•
180m
6095.4 ft. 548.6 fl
Plan Cross- Sect1on
0 Nodal point ond associated nodal volume
Figure 21. Integrated finite difference (IFD) mesh for preliminary model of flow around Oakwood Dome. One advantage of the IFD method is that it allow~ one to deform nodes into arbitrary shapes.
38
90
-
II ' ' II L I DOME
~
-.
80
I ~ II II
EXPLANATION
- 90 - Hydraulic head in lower two layers 2000m
-------- Hydraulic heod in upper layer 6095.4 II
Figure 22. Computed heads from pr~liminary model of flow around Oakwood Dome. The model indicates only a local perturbation of flow lines by the dome.
39
-----------------------
-Top of log
To,
-Top of log
1---17 mi-----l
EXPLANATION
Clean sand
D Muddy sand
~~~~-~~Cloy or shale
Transmissivity: T4 < T2 < T, < T3
Hydraulic conductivity values: ?
Dispersivity values·: ?
Vertical scale= 1"=100 ft or 30.5m
f---10.5 mi------1
Figure 23. Graphic correlation of Wilcox Group heterogeneities using electric logs from Oakwood and Keechi Dome areas (left andright, respectively). Around Oakwood, the muddy layer labelled "T 2" may be an important aquitard, partially separating more transmissive zones above ana below.
~0
STUDIES OF CAP ROCK ON GYP HILL SALT DOME
Shirley P. Dutton and Charles W. Kreitler
The cap rock on Gyp Hill Salt Dome consists of gypsum near the surface (0 to 90 m, 0 to 300 ft) and gypsum-cemented anhydrite above the salt (90 to 27 3 m, 300 to 895 ft). The cap rock formed by concentration of insoluble anhydrite grains as the dome salt dissolved.
At Gyp Hill, located in Brooks County, Texas, a continuous core was taken from
the surface through the cap rock and about 6 m (20 ft) into underlying salt. The upper
90 m (300 ft) of the core consist of bladed and equigranular gypsum crystals; common
solution-enlarged fracture and vug porosity occur between crystals. Minor amounts
(<1 percent) of anhydrite and carbonate are present as inclusions in the gypsum.
About 90 m (300 ft) deep, there is a transition downward from coarsely
crystalline gypsum to gypsum-cemented anhydrite (fig. 24). The lower part of the cap
rock (90 m to 273 · m, 300 to 895 ft) consists of anhydrite crystals surrounded by
varying amounts of poikilotopic gypsum cement (fig. 25) and chaotic masses of fine
grained anhydrite (fig. 26). Porosity and permeability are low throughout most of this
interval (table 1). However, immediately above the salt (268 to 273m, 880 to 895ft)
there is very little gypsum cement, and porosity is as high as 20 percent (fig. 27).
Cap rock formation at Gyp Hill apparently occurs by dissolution of salt and
accumulation of insoluble material. Salt samples contain 13 to 42 percent anhydrite
crystals (fig. 28) and less than 1 percent carbonate. Salt dissolution at the salt-cap
rock boundary concentrates this residue into a porous sandstone composed of anhydrite
crystals. Porosity is occluded a short distance above the salt (table 1) by precipitation
of gypsum cement and by compaction and crushing of some anhydrite crystals caused
by overburden pressure (fig. 26). The interface between cap rock and salt at Gyp Hill
Dome exhibits moderate permeability (45 md); therefore, salt solution can continue to
occur. The fact that the cap rock represents an accumulation of anhydrite indicates
that there has been significant dissolution of the dome.
41
0.----------------------------------------------------------. 0
0
100
200 0
0 0
0 0
300 0 0 0
0 00 0 0 0 0
0 0 0 Ci 0
0 0 0 0 oo 0 0
'b 0 0 0
400 00 0 0 8
..... 0
.c 0 c. "' a
500
0
600
0
0
0 0
700 0
0
0 0 00
0
BOO 0
0 0 0 0 0
0 0 0 0
0 0
0
900 0 0 20 40 60 80 100
Percent Gypsum
Figure 24. Percent gypsum versus depth in Gyp Hill cap rock. The non-gypsum fraction of the cap rock consists of anhydrite and rare calcite and pyrite.
42
Figure 25. Rectangular anhydrite crystals surrounded by poikilotopic gypsum cement from 262.7 m (862 ft). Scale bar = 0.3 mm.
Figure 26. Rectangular anhydrite crystals surrounded by chaotic mass of fine- grained anhydrite. Depth is 160.0 m (525ft). Scale bar= 0.3 mm.
43
Figure 27. Porous anhydrite sand immediately above the salt at a depth of 272.8 m (895ft). Porosity (black patches) is 20 percent in this sample. Scale bar = 0.3 mm.
Figure 28. Rectangular anhydrite crystals in salt (black mineral). Depth is 278.9 m (915 ft), which is 6.1 m (20 ft) into the salt. Scale bar = 0.3 mm.
44
Depth
(ft)
50
123
152
171
230
272
284
310
340
370
400
428
500
600
690
740
794
815
835
855
875
890
Table 1. Physical characteristics of Gyp Hill cGp rock.
Permeability
(md)
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
CL01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
45.00
45
Porosity
'(%)
1.6
3.0
1.4
2.0
2.5
1.2
3.4
1.3
1.5
1.3
2.6
1.6
5.1
2.6
3.1
3.3
1.6
2.2
1.6
3.6
4.4
20.0
Density
(g/cm 3)
2.35
2.35
2.58
2.34
2.33
2.43
2.81
2.35
2.81
2. 77
2.50
2 .. 65
3.00
2.97
2.97
2.92
2.78
2.95
2.82
2.97
2.88
2.99
IMPACTS OF SALT -BRINING ON PALESTINE SALT DOME
Graham E. Fogg and Charles W. Kreitler
Fifteen karstic collapse structures over the Palestine Salt Dome have been attributed to extensive brine production during the period 1904 to "1937. Three collapses have formed since 1937, one as recently as 1978. Palestine Dome is considered unsuitable as a nuclear waste repository because of the potential for additional collapses and because of the long-term impairment of the hydrologic security of the dome.
The Palestine Salt and Coal Company used brine wells to mine salt from
Palestine Salt Dome during the· period 1904 to 1937 (Powers, 1926; Avera, 1976).
Hopkins (1917) mapped topography over the dome and locations of 16 brine wells
drilled between 1900 and 1917 (fig. 29). Powers (1926) described the procedure used to
mine salt:·
Wells are drilled to the caprock at 120 to 160 feet, casing is set, and then the well is deepened 100 to 250 feet in the salt. Water from a water sand under the caprock flows into the wells, dissolves the salt, and the brine is forced by compressed air to the plant.
Hopkins (1917) states:
The main factor controlling the location of salt wells is the presence of a good caprock which serves as a seat for the casing and also holds up the overlying strata until a large cavity is dissolved out underneath it. When the supporting salt is sufficiently removed this rock, being undermined, caves in, with the overlying formations forming a large sink hole.
As of October 1979, 16 collapse structures had been found. Several of thP.se are
circular (in many cases water-filled) depressions that exhibit diameters of 8 to 32 m
(27 to 105 ft) and depths of 0.6 to 4.5 m (2 to more than 15 ft) (fig. 30). Hightower
(19 58) mapped 13 sinks (fig. 31) and assumed that each marked the location of a
former brine well. Sink 8 does not appear on Hightower's map but nonetheless must
have occurred during the brining operations because it can be identified on aerial
photographs dating as far back as 1932.
At least three collapses have occurred since brining ceased in 1937. Comparison
of aerial photos of Palestine Dome in 1932, 1940, 19?6, 1960, and 1976 (table 2) to the
surface geology map of Hightower (1958) indicates that sink 14 (fig. 31) formed
between 1956 and 1958, and sink 5 formed between 1960 and 1976. Mrs. Morris, the
landowner, states that sink 5 occurred within minutes after her daughter drove an
automobile over the site in 1972. Additionally, in 1978 the land surface suddenly
46
collapsed underneath a foundation support of Mrs. Morris' trailer home (see fig. 31) and
left a depression measuring approximately 1.2 m (4 ft) wide and 0.6 m (2 ft) deep. It is
not known whether these collapses mark brine well locations, because no record exists
of all such locations and because dissolution caused by brining could occur both near
the well bore and randomly at some distance.
Locations of actual brine wells drilled before 1917 were mapped by Hopkins
(1917) (fig. 29) and further demonstrate the potential for the occurrence of additional
collapses. Hopkins mapped nine productive brine wells on the northeast side of
Duggey's Lake in the vicinity of sink 14, yet there are only three sinks in this area
(fig. 31). Thus, at least six more collapses could occur in this area. Similarly, Hopkins
found three wells just east of the southwestern neck of the lake, where no sinks have
been found. This area is characterized by rapid erosion upslope and sedimentation
along the lakeshore. Therefore, any collapse features that may have occurred could
have been obliterated by these processes. Similarly_, erosion may have been precipi
tated by land surface collapse and consequent lowering of the base level of the local
stream.
Some brine wells were drilled into the present lakebed. Aerial photographs
indicate that at least one sinkhole was engulfed by the lake when, in the 1940's, the
lake level was raised by the construction of a concrete spillway at its outlet. In a
search for additional collapses in the lakebed, several bathymetric and shallow seismic
reflection surveys were run across the lake in conjunction with the U.S. Geological
Survey. The bathymetry showed the lakebed to be fairly uniform and to reach a
maximum depth of 1.8 or 2.1 m (6 or 7 ft). Although no depressions were observed,
they may be present underneath a thick muck layer that covers the lakebed. The
seismic survey was unable to penetrate the muck layer.
Chemical analyses (table 3) of water samples from water-filled sinkholes, Mrs.
Morris shallow dug well, and .Duggey's Lake show some general trends in ground-water
chemistry and flow over the Palestine Dome. Mrs. Morris' well and most of the
sinkholes contain low-TDS water typical of shallow ground water in the region.
Duggey's Lake and sinks relatively near the lake contain brackish water. The implied
hydrologic picture is that of recharge in the hills that surround the lake, downward
movement of water to the dome, dissolution, and then discharge of saline waters into
the, lake and into some of the sinks near the lake.
Duggey's Lake contains brackish water derived apparently from upward discharge
from aquifers overlying the dome. Evidence that such upward discharge exists is
provided by local residents and by Dumble (1891 ), who state that (before lake
47
-------------------- --
impoundment in the early 1900's) the lake basin was often swampy and contained salt
incrustations. The brining operations could be an additional cause of the high lake
salinity, since salt from brine previously discharged into the soil may still be washing
into the lake via surface runoff.
Most sinkholes contain fresh water, an indication that they either are isolated
from or supply recharge to deeper aquifers (table 3). It is plausible that many
sinkholes are isolated (or perched) ponds because they all contain a 0.6 to 1.2 m (2 to _4
ft) thickness of muck. Water from sites 1, 3, 6, and 8 contains relatively high
salinities. The high salinity at site 1 is probably caused by its proximity to a salt flat
adjacent to the lake spillway. The salt flat apparently is sustained by occasional
brackish water discharge over the spillway and possibly by seepage of lake water
underneath the spillway.
High salinities at sites 3, 6, and 8 suggest that these sinks receive upward
discharge of saline water. In sink 8, a brine well, its casing intact, is open to a depth
of at least 30.5 m (100 ft). Since the top of the cap rock is approximately 37 to 49 m
(120 to 160ft) deep at site 8, the well provides a conduit for direct hydraulic exchange
between the cap rock and the sink. It is reasonable to assume that this has caused the
water in the sinkhole to be even higher in dissolved solids than water in the lake
(table 3). Mixing along the well bore is apparently enhanced by seasonal fluctuations
in the water level in the sinkhole. During wet periods, the well casing in the sink is
completely submerged, thus permitting recharge of fresh water. During dry periods,
on the other hand, the water level in the sink drops below the top of the casing,
continuc3 to drop below the watPr IPvP.I in the well, and thus provides a potential for
vertical, upward discharge of saline water.
The continued occurrence of sudden land subsidence over Palestine Dome
appears to be the result of continued salt dissolution caused by (1) efficient pathways
for ground-water flow created by abandoned brine wells and solution cavities and (2) a
hydrologic scenario that provides for re.charge and salt dissolution and discharge over
the dome. Moreover, it is impossible to predict where future land collapses and
accelerated rates of salt dissolution will occur. Hydrologic considerations indicate
that Palestine Dome is an unsuitable candidate for a nuclear waste repository.
As a result of these· findings, the Office of Nuclear Waste Isolation, has
officially recommended -that Palestine Dome- be eliminated from consideration as a
potential repository (Patchick, 1980).
48
_l
0 I Mile
~·
N
\.Prominent out crop '{ Strike a nd dip of beds
----Fault X Prospect pit sunk fo r coal
• Prod uctive and abandoned s alt well:s o Unproductive well
Figure 29. Sketch map of surface features over Palestine Salt Dome with locations of brine wells drilled between 1900 and 1917 (from Hopkins, 1917).
49
\Jo 0
A
Figure 30. Photos of solution collapses at Palestine Salt Dome: (A) collapses ;. ard 6; (B) :::>llapse 15.
B
0
0
Mrs. Morris' Residence '
SCALE
DUGGEY'S
LAKE
I ·~ I \
\ • •11 10
• 14
EXPLANATION
• Collapse feature from Hightower ( 1958)
o Collapse feature mapped in May 1978
Base from Hightower ( 1958)
Figure 31. Locations of sinkholes overlying Palestine Salt Dome in October 1979.
52
Date
1932
1940
1956
1960
1976
Table L.. L1st of black-and-white aerial photos used in analysis of sinkholes on Palestine Salt Dome.
Identification Scale Source Holding code agency agency
1:18,000 Tobin Surveys, Inc. Tobin Surveys, Inc.
* CKQ-3-101 1:20,000 Texas Highway Dept. TNRIS
1:25~000 Tobin Surveys, Inc. Tobin Surveys, Inc.
CKQ-GAA-169 1:20,000 Texas Highway Dept. TNRIS CKQ-GAA-170 1:20,000 Texas Highway Dept. TNRIS
4-252 GS-VEBT 1:25,500 USGS USGS 4-253 GS-VEBT 1:25,500 USGS USGS
* Texas Natural Resource Information System
53
------------------- ----------------
Table 3. Water chemistry, Duggey's Lake area (Palestine Salt Dome) (mg/1).
Samples were collected between May 31, 1978, and June 2, 1978.
ION 1 6 5 3 7 8 9 15 13 14 12 Duggey's Morris Lake Well
HC03- 204.0 202.0 106.0 172.0 78.0 114.0 78.0 58.0 68.0 44.0 66.0 116.0 66.0 -Cl 425.0 68.0 28.6 343.0 31.4 1450.0 23.0 10.6 13 .4. 9.5 44.3 1347.0 22.8
so -4 104.0 13.5 13.2 42.0 1.5 30.0 1.5 7.2 4.5 18.0 78.0 37.8 13.5
Na+ 377.0 152.0 35.8 307.0 31.4 757.0 38.4 24.7 27.3 18.4 55.9 842.0 31.4
K+ 14.6 69.0 20.7 5.4 41.7 7.3 8.3 5.5 7.0 9.5 11.6 13.2 4.5
VI ca+2 90.5 31.4 25.0 59.5 15.2 342.0 23.4 21.8 17.0 12.2 24.7 160.0 24.2 .j::"
Mg+2 9.0 4.8 2.8 4.5 2.2 46.0 2.4 1.7 1.8 1.9 4.7 9.9 2.4
Mn+ 2 0.01 0.01 0.05 0.01 0.08 l. 93 0.02 0.01 0.01 0.02 0.29 0.39 0.06
L/ 0.06 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01
B 1.25 1.05 1.10 1.10 1.20 1.00 0.95 1.10 0.5 0.5 0.5 0.5
Si02 5.27 5.66 3.01 1. 76 4.45 l. 76 2.58 3.01 0.47 3.71 5.08 3.36 89.84
Sr+2 0.5 0.2 0.1 0.3 0.1 1.4 0.2 0.1 0.1 0.1 0.1 0.8 0.1
F na 0.13 0.0 na na na 0.1 0.1. na na na na 0.1
TDS 1231.2 547.8 236.3 936.6 206.7 2752.4 178.6 133.7 139.6 134.6 290.8 2530.5 254.8 (total dissolvec! solids)
pH 8.2 7.9 7.4 8.1 8.2 8.2 7.7 7.0 7.0 7.0 7.0 8.65 6.3
REGIONAL AQUIFER HYDRAULICS, EAST TEXAS BASIN
Graham E. Fogg
Ground-water circulation in the Carrizo-Wilcox aquifer is controlled predominantly by topography and structure. Fluid movement is generally downward, because of the structural dip and the leakage from overlying formations. Discharge to the Trinity and Sabine Rivers occurs via upward leakage across the Reklaw aquitard.
The regional aquifer hydraulics defines basinwide ground-water circulation
patterns and provides an appropriate perspective for site-specific work. Geologic
units considered to be potentially important to salt dome dissolution and transport of
contaminants away from the domes are (upward) the Woodbine Group, Nacatoch Sand,
Wilcox Group, Carrizo Formation, and Queen City Formation (see "Stratigraphic
Framework"). Formations below the Woodbine are considered to be too deep and too
low in permeability to threaten a repository shallower than 900 m (3,000 ft). The
Wilcox and Carrizo units, both major fresh-water aquifers, are the shallowe~st aquifers
in contact with the domes and are cons~quently the most critical. Work in regional
hydraulics has focused on the Wilcox-Carrizo system and its fluid interactions with the
overlying Queen City Formation, which is also an important aquifer.
The Woodbine and Nacatoch units are separated from the Wilcox Group by from
1 ft to several thousand feet of aquitards (and possibly aquicludes), and thus they are
not easily recharged and discharged. This, together with the low permeability and
transmissivity of these deeper units (relative to the Wilcox); imposes ground-water flow
rates that are much lower than those for the Wilcox Group. The net result is that the
Woodbine and Nacatoch aquifers have limited capacity to dissolve the domes or to
transport dissolved solids into the biosphere. The Nacatoch Sand, in fact, probably
poses no threat since it is thin and apparently low in permeability over most of th.e
basin. The hydrogeology of these units (geology, pressure, and salinity data) is,
nevertheless, being studied (see "Salinity of Formation Water").
On a regional scale, according to hydraulic head and geologic data, the Wilcox
and Carrizo aquifers are hydraulically connected. Consequently, they have been
combined as the Wilcox-Carrizo system for mapping of potentiometric surfaces (figs.
32, 33, and 34). The regional structural configuration of the Wilcox-Carrizo aquifer is
complicated by the Sabine Uplift, which caused local counter-regional dips (fig. 35).
Variations in lateral transmissivity in the Wilcox-Carrizo aquifer. are governed by
distributions of fluvial-deltaic sands and muds, which were deposited by a dendritic
system of north-south oriented, high-percent-sand channels (fig. 36).
55
Ground-water circulation patterns in the Wilcox-Carrizo are controlled prin
cipally by topography and structure. In outcrop areas, flow lines closely follow
topographic gradients as water moves away from watershed divides, which are major
recharge areas, and toward stream valleys, which are major discharge areas (figs. 32,
33, and 35). Ground water leaves the outcrop area by discharge to streams and wells,
evapotranspiration, and downdip subsurface movement, where the systern is confined
by the overlying Reklaw aquitard. Lateral, subsurface discharge from the confined
part of the basin (figs. 32 and 34) follows the structural dip (fig. 35) as ground water
moves toward the Texas-Louisiana border in the northern half of the basin and toward
the Gulf of Mexico in the southern half of the basin. The ground-water divide is
located in southern Smith County.
Natural recharge and discharge occur into and out of the confined part of the
Wilcox-Carrizo aquifer by vertical leakage across the Reklaw aquitard between the
Wilcox-Carrizo and the overlying Queen City aquifer. Evidence to document the
leakage between the systems is as follows:
(1) Ground-water flow lines in the confined Wilcox-Carrizo aquifer tend to veer
away from watershed divides toward stream valleys and thus imply recharge along the
divides and discharge along the valleys. This is especially evident in Anderson County,
where heads indicate an extensive recharge mound underlying the Trinity-Neches
watershed divide (figs. 32, 33, and 34).
(2) Vertical head gradients indicate downward leakage (recharge) over all areas
of the basin (fig. 31), except along the Trinity and Sabine river valleys, .where presence
of flowing wells (fig. 34) and Wilcox-Carrizo heads above streambed elevations
(fig. 38) indicate upward leakage (discharge). In figure 34, the head differentials
between the Queen City and Wilcox-Carrizo aquifers generally increase in magnitude
toward watershed divides; this indicates that downward leakage increases accordingly
and probably causes Wilcox-Carrizo heads to be higher underneath the divides.
Figure 35 shows that the Wilcox-Carrizo does not discharge to the Neches River,
'which is the reason that heads and flow lines in figures 32 and 34 appear relatively
unaffected by the river.
(3) In the Reklaw Formation, many silt and clay beds, which make the unit low in
permeability, are lenticular but may become sandy in many areas, an indication that
the Reklaw could leak significantly. In the northern half of the basin, net clay was not
mapped~because of limited success in distinguishing the Reklaw from the lenticular
sands, silts, and clays of the Carrizo and Queen City aquifers (fig. 39).
56
Vertical movement within the Wilcox-Carrizo aquifer has been studied using
pressure-versus-depth plots constructed from well-construction and water-level data.
A plot of data for the entire basin (fig. 40) shows that the vertical flow component
·generally is directed downward. This is the result of leakage from above and/or flow
parallel to (downward) the structural dip. Similar plots of data taken exclusively near
streambeds should show upward movement in areas where heads are above streambeds
(fig. 40 ).
Wilcox sand-filled channels do not appear to affect regional flow significantly,
except I?erhaps in the northern half of the basin where flow lines converge on two
relatively isolated channels trending through Gregg County (figs. 32, 34, and 35). This
convergence also may be caused by historically high levels of pumpage in the Gregg
County area. Other areas in figure 32 · where .Pumpage has caused noticeable
drawdowns are the City of Henderson (in Rusk County) and Nc:lcogdoc~es and Angelina
Counties.
Hydraulic head values for the Queen City aquifer follow closely the rolling .
topography above this unit, and the values are, therefore, irregular. As a result, it was
not practical to produce a contour map of potentiometric surface from the data
available; therefore, the heads ar~ displayed as rnean values in figure 41. The figure
demonstrates a nearly random scattering of localized recharge and discharge areas
over the aquifer.
57
EXPLANATION
-200- Potentiometric contour
C Wilcox- Carrizo outcrop
----· --- Watershed divide
-Fault
A Salt dome
0 cenlerville
LEON co
0Crockell
/ N
f 0 10
10
/ olulkin /
ANGELINA co
20 30 40. 50 Ml
20 30 40 50 KM
Figure 32. Potentiometric surface map of the Wilcox-Carrizo aquifer system. The water-level data are from 1936-1976; however, most of the data are selected from measurements made during 1962-1971 on the basis of historical water-level changes.
58
·~
[eckqy 'J.feek /,
/ j '
ANDERSON CO.
0 2 4 6 8 IOmi
0 2 4 6 8 10 km
· Figure 33. Detail of Wilcox-Carrizo ground-we3:ter flow in Anderson County.
59
EXPLANATION
-::# Wilcox-Corrizo ground-woter _../' flowline
0 Wilcox-Corrizo outcrop
.. - .... _ Wotershed divide
• Flowing well
t:;. Solt dome
1 I
I 1 ..... ......
I
I
RIVER
' - ~\
44-+--- F3)\"" NACOGOOCHE~,,.~
~~~ f I
0 50 mi
0 .50 km
Figure 34. Ground-water flow lines in the Wilcox-Carrizo aquifer system drawn from figure 32. In both the outcrop and the confined parts, ground water tends to flow away from watershed divides and toward rivers. •
60
•,
'
I I
I ,r_l_
RAINS CO
VAN V. .. NOT CO
HOPKINS CO
I
N
f
A ---""lotum Marlin '\
,f~Jieckville
---PANOLA CO
SHELBY CO
CONTOUR INTERVAL= IOOFEET
10 15 20 Miles
SCALE
Figure 35. Structure contour map on top of Wilcox Group (from Kaiser, personal communication, 1979).
61
HOPKINS
w.N.Bcch and W.R.Kaiser r977
0 10 20 30 40 SOmiles
~I~·~·~·~·~· ~·~·~·~·~·~I 0 10 20 30 40 50 60 70 eo kilomeie"
.Daco
)"·---·\. ___ .:...---·1 ; ·-·
~rn .Beckville • Lake + I o .c:alhoge ' v I i
D >60%
. [§j[J 50· 60%
Cill40-50%
D <40%
v ~'- PANOLA
Figure 36. Percent sand map of Wilcox Group (from Kaiser and others, 1978).
62
--l I I
- 1- -67i-~0 rTo5 SCALE I _L
0 5 10 15 20 25 Miles
[o 1- - -"I '-
0 5 10 15 20 25 Kilometers 55 140 15 76 I I I
\ 80 100 116, ~5 l
65 10 65 >4
I
~5\ '· J. 70 115 25 55 40 120 150 80 io _l
"\ I
' 135 110\ N 35 '~ 100 >54 110 50 I ,130 90 tL_-~
" I \. I I
75 20 30~ - ... ..;--'"""" ~
29 10 75' 85 ~ ~
~ ' 1'-'46- '\.._ P-1
1.........-- r' r--3~ 25 140 95 90 / ---- -.... ( I~
f' 110/
, I "\55 95. 165 125
I "- \ I - /
l 85 125 l\~0 100 105 60 160 .... /~ -
\ --r-- r- -- -, \ / '· :
' 100 50 105 \ 85 145- no' 110/ I \ ,
I 8~ ',L 180 125 80 125 100 120 115 195 I )
\ ) ! 165, 155 110 105 65 85 135 95 115 \, I
-rl \ -iTS - 'iiO -- -t 17~1 230 110 225
I l-f26-~--- I 1-8.,?_ 15qi. 120- 105 ' 145 130 -- I
I 75{ I 55 1751 80 35 90
' \
_\ 82 110/ 190 125 ll160 160 I ( l
~
ANDERSON I L \ 160 110 140 r-, 155 COUNTY ,
'""--- ' \_ ~
I"' 25 160 145 140 145 105 140 185 p \
"' ~<. ( 135 175 105 160 130 170 75 hi'> \ ~"' 1 ("'\ 55 150 75 80 80 P,
!',_ ~ __j_ ,/ lr-~
, 105-f-- '\__ rl ,,.,
90 ~~ 4 ~-I -..::: ~---- l
I 25' ~( ~_. I ~ t
10 6 3 \ ,,. \,
"' / -~ /{ -15 125 / '
-, ' \ \ '-~ 80 110
.... __ -, I
I r' 80 ,r' I
EXPLANATION \ I
1\ 80 35 ( 225 Mean head differential between
I Queen City and Wilcox-Carrizo
t , > Systems (negative values indi--35 I cote upward movement) \ I f
I, 1 v--- 1--- 1---l ---- Watershed divide -"'---
\ I v--- \ \
Figure 37. Head differentials between Queen City and Wilcox-Carrizo aquifer systems. Widespread positive values indicate downward leakage from the Queen City to the Wilcox-Carrizo everywhere except along stream valleys, where data are insufficient. In many areas, differentials increase toward watershed divides owing to topographic effects.
63
1i . i . ~ 200 w
0 10
500 Wilcox- Carrizo Outcrop
~ 300
15 20 25 30
'-- Streambed elevation
9 Ground- water level within 2 mi of the river
• Ground· water level within 1 miofriver
35
• 6 Land surface elev. of flowing well within 2 or I mi of river
0 • 0
b) Neches River
40 45
1-Wilcox-Carrizo Outcrop _____ _
o) Sabine Ri11er
so 55 60 65 70 Distance I river miles)
75 80 85
r------ Wilcox - Corrizo Cutcrop
90 100 105 110 15 120 125
! .8 2 "' ~ j;j
I . ~0 ---~--------"""----"----
.. .....
c) Trin.tty Rirer
200o~-~5-~I~C-~15--720~~2~5-~3~0~~35~~4~0--445~~5~C-~5~!-~60~~6~5-~7;~8J~L0--3+5--430--2~5--2*0-~Ie~-~IC--4--0~-4--~10-~+15--420--2~5--*30-~3~5-~40 Distance ( river miles) Distance I river miles)
Figure 38. Profiles showing elevations of Wilcox-Carrizo water levels above major streambeds. Heads above :he streambeds indicate the presence of vertical upward leakage through the Reklaw aquitard. Heads along the Neches River document that it receives no discharge from the Wilcox-Carrizo system.
I
l 62 !8 SCALE ..
0 5 10 15 20Mile<a r' 73 42
' 0 5 10 15 20 Kilomelers 83 89 ."62
~ls5.;: f-88- -71- >.57 '>93 . '-- -) 7G 00 >"i1 •00 --- )
------ .so :83 118 ~8. 110 - -- .,
~55 • . .
-"\. 50 43 90 '94 165 .. 107• 125
104
' 82 ' ..
·~· ( ... 44 102• ·8:3 ~2 130
' -"'In I 9,8' I
( 92 ·.82 67 (_ !'-,ANDERSON COUNTY
) "'--
60' t~ ·83 • 68
I -~.,
88 108 67 115 "7, ~
', .r-,, 190 \
\ ') ;114 136 131
,\) \45 II~ 141 143 162 ~ J • /
( J59 J46. _:.154
_____ ;;;;.--l' .r-· 97- ... 60 139
.~ -~ -·· -·- ----· -----·~---
... -,; 91'' I 78. '67 90 >12il 167 .153 N
~· I 1---'-
f •85 60 70 • 1011' ~165 • 155 172
r--:. 'I -·-\
64· 76 \ 162 164 ,_j
52 77 159 J
Figure 39. Net clay thickness of Reklaw aquitard. Leakage across the unit may be enhanced where it thins or becomes discontinuous. The clays tend to be discontinuous in the area of the map and become even more so in the northern half of the basin.
65
~-
1
I
"T-~---- ------------------- --------------------------------------------------------------------""[ 1200
1050
~ 900 ... <I)
0 ~ -0
-c 750
g I .c !
~ I .t 600 L
I
J I
300 f-I i i
150 ~
0 0 15()
0
300 450
Hydrostatic -(slope= I)
0
0
0
600 750 .
Depth ( ft)
0
900 1050 1200 1350
Figure 40. Basin ward pressure-versus-depth relationship for the Wilcox-Carrizo aquifers~ The less-than-hydrostatic slope (.83) indicates a component of downward flow over most of the region. This relationship should be reversed beneath the Sabine and Trinity Rivers, an indication of upward movement.
66
1500
0 5
0 G
SCALE 10 15 20 25Miles
(
----1-L-F-7-:- ~-470 540 415
i 'P ,I
10 15 20 25 Kilometers 0 330
280 0
370 385 0 a,.,
N -·.- -
I'
,., " /-, r
O I .435 395 0
I 495 480 0 0
' 480 ' 0 I
' 0
' ot\'b w''o
460 48,.,5 1445 395 ~400 445 435 ~...... 0 0 ..........
=---c ocr=.: ""1 --f~ vorf'-0 t-=---=/:;IL--,--\:-;1 i-1!'--/---0 450 ,: p4005 44~- 410 0390
ln395 0 P \ 1
!
455 1...----~-- 0 f----·-+--1-----+--11 I~Q ~ .. ~15+1V405 °370 ' 400 385 I
-- 0 I -~\--- 0
355 1'>46~ 410+ 35"( 370 0 285 Ol 0 0
) a 385, I
J \
_I
\ 0 460 h. 0 00 (_ 345 38tts> o 395 V370 420 410 !
L.
~p
1'7 ANDERSON I 0
\) COUNTY 120' 37o
390 t--, -t---H,f-~-lh'-__ -r2-6-0-r-4-9, __ 0_f~ o39~ ~85 )
I ._...... ' '-
0410! 40~! 0 . +-. +-----+---+.
350 ! 3~0 !o420 I
0 0 400 285
0 0 ) 375 410 _ 34,5 1 lJ~~ '
0
380 350
' 275 p290 %2o~ ! (\ 280 3 ~5 255o \
0 0 ( ~_.-1 } ' 0 \ ' 0 0 400 ./ ( 0 O
1 300 -_-0-"\. I - O \,._.,
345 0
0
320 0
0 0 345 c..---- -~ 225 ~~:-------~ 340' 270,... ·,, 255 .' t-J -+--+-----b-"<>.--.--_r--+---11'.---_ o ~ . - ' B · ,.,..--o---t---'-"'k---t--:--t--'-1=-
, r).-2~ 2~5 265+ ~25' 225 \ 270 280 --;45 \ 2~5 O'o l--- 31~ b25; ------t--+· -'~-"1:1---
1 a '
-~,v
~---+./1_ .... ' +-·-+---'a"+----_. \., 380 28~
I
435
t---+--+:i'r--1---- ~·-+---+-·-:~35 305
I 0
EXPLANATION
250~
235 0
220 l) Well tapping Queen City aquifer
265 a a 270
290 0
325 " ,-· ~ v-
---- 175+ \..,
Figure 41. Potentiometric surface map for heads are caused by irregular topography. areas are sea ttered throughout the aquifer.
67
250 Mean Queen City water level
---- Watershed divide
+ Indicates presence of flowing wells
the Queen City aquifer. The irregular Close! y spaced recharge and discharge
-------------------------
SALINITY OF FORMATION WATERS
·Graham E. Fogg
Estimates of the salinities of formation water in the Woodbine, Nacatoch, and Wilcox stratigraphic units have been accomplished using electric log interpretation (SP and resistivity). These estimates provide general information on 8alt dome dissolution in the East Texas Basin.
Estimates of salinities of formation water in the Woodbine, Nacatoch, and
Wilcox units were made from electric logs (SP and resistivity). These estimates
provide general information on the occurrence of salt dome dissolution in the East
Texas Basin.
Maximum salinity in sands of the Woodbine Formation was mapped from SP
vaJ ues using methods outlined by Keys and MacCary ( 1971) (fig. 42). The map
demonstrates a variable distribution of maximum salinity values ranging from 30,000
to 300,000 ppm. A vague trend of increasing salinities toward the central axis of the
basin corresponds to a salinity map in figure 42 of the Woodbine constructed by Core
Laboratories (1972). Because of the scatter and the sparsity of laboratory water
analyses, no means exists of detecting salt dome dissolution by the Woodbine aquifer
system. A similar analysis of the Nacatoch Formation showed the unit to be either
m1ssmg, very thin, or tightly cemented everywhere except in the northern part of the
basin. The thin Nacatoch aquifer poses a relatively minor threat to the stability of the
domes under study.
Salinity estimates ±or the Wllcox Group were made using an e•Y•pirical relation
ship between electric log resistivity and total dissolved solids (TDS). A graph (fig. 43)
displays formation resistivities (Ro) in sands tapped by water wells versus correspond
ing TDS values determined in the lab from the well discharge waters. Although the
graph is thought to be ·fairly accurate (+500 mg/1), it should be considered preliminary
until further calibrated and verified by geophysical logs and water samples obtained
from the current drilling program.
A map of percent thickness of fresh water (less than 1,000 mg/1) in the Wilcox
aquifer (fig. 44) indicates three sources of salinity: (1} upward leakage of deep, saline
water along faults, (2) incomplete flushing of saline water in muddy areas of the
Wilcox Group, and (3) salt dome dissolution. Upward leakage along faults may be
occurring in the Mount Enterprise-Elkhart Graben ir:t southern Anderson and Cherokee
and northern Houston Counties, where salinities increase abruptly. High salinities from
salt dome dissolution could be confused with high salinities resulting from upward flow
68
along numerous faults associated with the domes. The lack of high salinities around
domes depicted in figure 4-~, however, suggests that the domes are neither dissolving
significantly nor creating pathways for upward leakage.
Incomplete flushing of saline water in muddy areas of the Wilcox Group is
suggested by a good correlation between saline zones (fig. 4-4-) and muddy zones on the
sand-percent map (fig. 36; see "Regional Aquifer Hydraulics, East Texas Basin") such
as in Upshur County, southeast of Mount Sylvan Dome and east of Whitehouse and
Bullard Domes. The saline intervals near the three domes are not caused solely by
dome dissolution, because salinities decrease and fresh-water thicknesses increase
toward the domes. The original sources of saline water in the muddy sediments may
be from salt dome dissolution during the geologic past (such dissolution could be slower
today owing to cap rock development) or from marine waters that submerged the
Wilcox at least twice since it was deposited 4-0 million years ago. The continued
presence of saline water in and around the muddy facies is possibly enhanced by
ground-water velocities that are probably as low as 15 to 9,150 em/million years (0.5
to 200 it/million years). These rates were calculated using maximum and minimum
hydraulic gradients of 6.3 x 10-3 and 1.0 x 10-3 measured in sands surrounding the
muds (fig. 32; see "Regional Aquifer Hydraulics, East Texas Basins"), and estimated
clay hydraulic conductivities of 3 x 10-5 and 3 x 10-3 em/day (10-4- and 10-6 ft/day).
There is little evidence of past or present salt dome dissolution in figure 4-6.
Only around Oakwood Dome, a distinct plume appears directly related to dissolution.
However, this plume contains mostly brackish water ( <3,000 ppm) and does not seem
to indicate a significant rate of salt removal (see "Hydrologic Stability of Oakwood
Dome''). Without exception, the maximum concentrations of dissolved solids in the
Wilcox were found in muddy sands at the bottom of the aquifer. In nearly every case
these concentrations are around 5,000 ppm (:t_l,OOO ppm), and in a few isolated areas
appear to reach 10,000 ppm. Additional details of salinity distributions around the salt
domes are shown in cross section in "Evolution of East Texas Salt Domes" (figs. 12, 13,
14, 16, 17, and 18). The sections indicate a general lack of anomalous salinities around
. the domes, in agreement with figure 4-4-.
Although salinities in the Carrizo and Queen City aquifers were not mapped,
none of the electric logs observed throughout the basin indicated brackish or saline
water in these units, except near the Mount Enterprise-Elkhart Graben Fault Zone.
This agrees with the regional aquifer hydraulics, which indicates predominantly
vertical downward movement in the Eocene aquifer units.
69
----------------- -----
r--1 --- f, ''-,I j I -l--e-------T ___ _j, '\ I
I ,\ e • , \...._ I (\ I • • l----------:-1
------r---~.~ \ ~oem•n I ~
eo e -.,____.___, I I, ~,--......... ~"-......, I. 69 0
ffi ffi S ~S "'--·C:~ Hornesville• 0 ,
1
1 e E6 .Grand I'. I
• ~Saline ~ ffi s• ,,-..... e e e EB e mffi , ~----___,-, EB • o I' I I
ffi 0 (").... E£(} ,I O :e Hawkins ,.......--' I • ~ ess e ~~lnl~ ~~ ''--\,)'"""-~-') _ _;,-,........--, j
N
If 8 0 ~-EB 8'- -_;' · ·~ I
EA 0 ffi~~- ~ Sltt.'IA ED,&') • rl . I
lo •- e • ffi • ffi u~EB •et .... l -.....,_ _ ____ _r __ _§_ffi.._-~____[) _ _g?~,~~· ffi • Chopel~lli(> S~~----------
0 .,_ ffi • .,_ &Opelrko e e. Eosl El:l 0 ~ 0 go - ' Tyler • 0 S 8 o c9 o 0 EB EB m~0 \ •od+l ...4'+1 d
e e • • f e o-- v-@ EB l 8 8 S ffi ~· • t;J .Whllehouse 8 1 MAXIMUM SALINITY IN
"vi e 8 fi se \ EB g A\ • I wooDBINE sAND (PPMl ~ 8 • ~ 8 • Bullard Q 8:. r<l I
~-p ""' .. 0 .,_ Larue- ~~oks ,MB I::)-'~ 0 IJ] go - ,...._ __._e--..._ 30,000 - 99,000 O • 0 • s \: -'d--• ... Q__ffi C/,-.. - I
\.-~ m .en o s • '-t s ecm Oe:J e I e roolooo -149,ooo
• ffi --~--~"(,~ s (D \ 0 ffi @ 0 • ffi 1501000-1991000
~-sa- ~ • f ar!'. • · m- e m I . s 2001000- 2491ooo
...........--/~ SO Brushy ~S • ~- c::e O•EB ~S ffi i e 250000-300000 , ffi"""', e s~ee~ ~ 'Boggy S':E s El I I
0 0 •b S c9~ •e Po...-.. Creeke 93 - 1 L-. ~ Concord • -~ .,. ffi • e Oj N .e ? Bethel 8e e•e.. I • •• • • • I D Average of 2 or e '\ e8 - ffi tl., s• • • e ~, more data pornts e a:.... l MKeechl m..• '? n •• s s c)
"'tt! ~-~ cf67 \\.J. • I s • -- • e s~. Salt dome
• EB e -1 • 1..... s o , e._ e ('n sffi .Poleslone I o""'. ·0.~ o• \
• ._ - t'liL e'*' ' •f <;),_ EBe Bullei"'·~ 'U ~ e ...... ___. ffi .) 8ee• 8 ~ (~... ...Slocum S > ffi. • \
EBe • • _.........--v / • EB • -. ~ • • •• ~ ffio/ Elkhort,Jt ffi --.---.- U../' \....-1
coffi ,ko;wood ss:;:etJt-·::c---· ffi ~~ \ • • \. _.........- ~ )-e-- s ffi tj "'\ ''-..
...........--...........- s:SC • e ~ ~ 8 • • e I '(_\. _/ '""--,...._ ___ _ ' 1 .,_ • ffi -,_/ s I go (
( ( I
\ -\ '-,. ~ ' r'-'
0
0
/' _/, L_
30mi
30km
Figure 42. Maximum salinity in the Woodbine Sand as estimated from SP curves. The broad scattering of data could be due to limited circulation in the unit, fluid injection, and/or errors induced by the method of estimation. I
70
~
' "' E
"' ~ ~
103 .., ., ~
0 "' .!!! .., 0
0 1-
102
10°
EXPLANATION
• Wi I cox aquifer
0 Carrizo aquifer
•
•
•
•
10 1
Ro: resistivity
•
• • •
0
from electric
•
•
0
•
log
Fresh (TDS< IOOOmg/1): Ro>20
Brackish ( 1000 < TDS < 3000) : 5< Ro < 20
Saline ( TDS > 3000): Ro < 5
•
• • ••
0
•
10 2
(ohm/m)
Figure 43. Relationship between formation resistivity (Ro) and TDS concentration of formation water. The straight line was eye-fit rather than calculated by linear regression, since several values of Ro were of uncertain accuracy and had to be weighed. sut;>jectively.
71
10 3
, ___ , ----- f. ''-,I ,I
I \--------o--q;----'-1 . "-, I
( \ ~ eoe ·~----------~ ! -----, __ '"·-_, i ,,; .... ~ e<lleoe~ ~s s sJl • e<JJ !1.,.
PERCENT FRESH WATER '----') \ t/5 9 8 e 8 ,ffi ffi • • ffi ffi eS :-'-.... IN wiLcox GRouP ~'----, 1
88 E$ ~ J s e e e•e EB 1
• o -19 -:::"--\\ e s e A EB • ~ • EB 8 EB se e e I
,&Saline I e e • Hainesville • I Q E9 e e e I s 20-39 Qt-, ES I ~ • E:::J s ,,-.,.-€9 40-59 9 0 o"er_...___jL·~~ Ho~~. ! • s • _,....,I i ~ ::~~~~ VonAii $1:~~ ""\.-\,.J~--L~~.A-_.......-- i
A_ ~8 Q ~ Sleen e I , ~-8 g E9 I
D Average of 2 or e e ".,.Q tB E9 . II -
mare data pamts e Wt' fi e EB Chapel s . .......... ---~- --e- MISylvon e A s AHoll 1 _________ _
A Salt dame OpellkOA-----e e e-- ~~~;r E9 I o \ EB s• I
8 ffie EB8 /Jct:J ~ • ~~ El I - 8 ~ \. Whlleho"l!l s E9 II
\./ 0 8 9 8 8 ·1Brooks ~ 8 ' ~ . ·-- e g'''Jaee e~ft!=f e '
( e 8 ~~- e-----~ ' o 9 e ~ ~ ~ · \--~ o e ~) EB EB tl I
· 3---e-~-- ·,_~ ~ EB ffiffi~ I· \_ --_@- 'a.? ffi s s m 1 _..--·' - @ EIE8 0 8 Boggy'ffi A-8E $ ffi
/ • ~ Brushy 8 Creek !0::::) ffi S 8 ffi I - --", e Creek G ~ ~ E9 E9 ~ I J Concordi9 ~ e ffi ffi ffi ffi ffi 1
~ ~ EB e 8 ~e efi!j ~€9 • 8 I
N
J
?selhel :1 Et:.e-Jf~ e 8€9 ffi' E9 _A • E9 '! ::e_ ~~:? 1m e(;!j'Efo EB EB I ~~-· -------
, W:;'Keethl E9 0 ~ ffi 8 8 E9 E9 I ) "---:. . . tt , . ffi ED e # • '-....., ~ ~ 8 ~ol<;l;n~ - 8 E9 $ ~8 ffi. E9 f Buller~ M E9 8 ffi fiE .,..., • ')
J ; (' EB •,.,... Jil.l•cum 8 '• EBB , , \8 <J:7 • • 8 L 8 ' e II:>~ _..--•IJ $Eikhorl ~ 0 9 / 8 \
Ook~d.t~~ ._; .~1 EB__.~· ---•;;-'---/'( • \...., ...-o-., 8 ) $!>'' 8 • • ... '') • \ _
_,./- 8 '-0 1B EB,-; ~~ \... ,/''--,-"--_. 8 e e- 1 s • \._\.:/ '--...._ ___ _
e 8 o \ • 8 ', 8 8 , • \ cl ,/ L_
8 8 8 o /'' -/ I"' ,
8 8 8 8 ( 0 30mi
( 0 30 km I
Figure 44. Percent of Wilcox thickness containing fresh water (<1.000 mg/1) as estimated from the resistivity curve of electric logs.
72
GEOCHEMISTRY OF GROUND WATER IN THE WILCOX AQUIFER
Charles W. Kreitler and Graham E. Fogg
Ground-water chemistry trends in the Wilcox aquifer clarify the potential for the transport of radionuclides, the general flow paths, and the significance of carbon-14 age dates of the ground waters.
The Wilcox aquifer is the most continuous geologic unit containing fresh ground
water in the East Texas Basin. If a breach occurred in a salt dome repository and
radionuclides leaked to an aquifer, it would be in the Wilcox system. The geochemis
try of the ground water in the Wilcox aquifer indicates the ability of the aquifer to
retard radionuclide migration. Anomalous geochemical zones in the aquifer, which
may represent recharge and discharge or relative flow rates, support interpretations of.
regional flow of ground water. Absolute age dating of Wilcox ground waters is
complemented by regional geochemical data.
The results of over 800 complete water chemistry analyses were obtained from
the Texas Natural Resource Information System (TNRIS). These data were evaluated
by means of a computer program, WATEQ, which analyzes the cation-anion balances.
Next, the interrelationships between different chemical and aquifer parameters were
evaluated by a statistical program (SPSS). The following correlations were observed:
(1) Sh?llow ground waters in the recharge zone exhibit lower pH, higher··calcium,
higher magnesium, higher silica, higher sulfate, and lower bicarbonate content relative
to deeper artesian waters.
(2) Deeper artesian ground waters have high pH, low calcium, low magnesium, low
silica, low sulfate, and high bicarbonate values.
(3). A sodium bicarbonate-rich water is generated as ground water moves farther
from the recharge zone (fig. 4.5). Sodium replaces calcium and magnesium by cation
exchange on clays. This continual displacement of calcium permits undersaturation of
calcite and, therefore, subsequent dissolution of more calcite. Calcite dissolution
operates predominantly in a closed system; no external source of acidity causes the
dissolution. This is indicated by the continual rise in pH away from the recharge area.
(4) The pH of ground water changes from 5 to 7 in the recharge zone to 8 to 9 in
downdip sections (fig. 46).
(5) Silica concentration decreases with depth. The source of the silica in the
shallow ground waters and the mechanism for silica loss are not known (fig. 47).
73
(6) Sulfate concentration decreases with depth (fig. 48). Loss of sulfate is prob
ably by reduction. Sulfate reduction indicates low Eh values in the ground water.
Ground-water chemistry indicates a trend from an oxidizing, low-pH ground
water in .the recharge zone to a reducing, high-pH ground water in the artesian
section. Migration of radionuclides is dependent on pH and Eh conditions (Bondietti,
1978; Relyea ·and others, 1978).
The outcropping Wilcox aquifer generally contains neutral to acid water (fig. 46).
These low-pH waters also are found at the ground-water divide in the Tyler area and in
the Keechi Dome area. Regional ground-water flow studies have postulated that these
sites are recharge areas, an interpretation substantiated in part by the water
chemistry.
74
35 800
30
600 25
20
15
10
200
5
•
Slope= 1.3
• Data point 9 9 Data points
at same location
2
•
• •
..
.. •
. . • •
• •
• 3• 3
•222 4•
• 2 ..
• • ... 2722••
• • • • 2 3 7 3• • 3 3 39 2 5 •
• 2 24•27 5 • • ••2•574975
3399995•· • 2 899993•
• 69999 3 2• • 36 59 9 9 8 52 ••• 358999464• •
0 999994••2•
0
2
• •
•
2 •
• • • •
• • • ..
1200 20
Figure 45. Correlation of sodium and bicarbonate in Wilcox ground-water concentration increases downdip from recharge zone.
75
--" .....
1.00
222.70
444.40
666.10
887.80
~1109.50 ~
a. Q)
0
1331.20
1552.90
ITN.60
1996.30
2218.00
3.00 3.70 pH
4.40 5.10 5.80 6.50 7.20 7.90 8.60
* 2* 3 22 •3• 33 *3 433 *9 2 • * •• 4.52.5 9 ••••
* * • 2 2 2• • 2•• 3 • * •• •• •2 • • • 2.. • •
• * • 22 • 3 2 •3 64. 22 42 •• • 3 22* 23 23 34 2 42
•• ..2 •• 2 •2 2 25 422 33 2 • 2
* ~· ••• 5 32 762 34 2 • •• *** ~ * ~22 2~ 22 *44 25 ~G 2*
•• • 2• 2 •2 32 454 •6 22 3 • • • 2 •4 2* 524 jj jj 2*5
2 •. 2 24 •• 252 52 52 64 3 ?3??.442 4.
• • •••• 7 4 2 44 4. 2 *
* Data point
2 2 data points at some location
• •J 4.2 24 44 .• 22 • •• •• 25 4 23 23 .3
• •• • 4 3 • 23 2• • 2 •• 3 3. •
• • • •• • •
•
• • • •• •• • • • •
• • •• • • •• • • • • • •• 2 • .2 •
• • .. • •• • • • • • •• 2 • •• • •
• •• •
• • • 2 • •
2
• •
9.30
Figure 46. Increase in pH values with depth, resulting from calcite dissolution and cation exchange in a predominantly closed system.
76
10.00
1.00
222.70 •
•
444.40
666.10
887.80
g·II09.50
.s::. Q. "' 0
1331.20
1552.90 •
1774.60
1996.30
2218.00
0.2 0.4 0.6
2 • 2 •2 3•.. • • ••2 •• 3 3 2 3
• ••2• •••• ••• 2 • • 3
2553236 •2• ... •64442 •2• 958334•• •
•5348452 •2 •2999745 ••••
2
• ••857364• 22 •••
•965542. • •769339 •••
• •
•2
•
•
235644 •4273•22 •
2G83•23 46 •732 • 8422 3
2•••252 2 2• •
2 . • •• 2 ••
•3 .•
•• 3 •• .... • •••• •• . .
•• •2•• 2 ••
•
• • • •••
• •
2 •
• 3
•
• 2• • •
• 2 •
•• • • • 4
•
Si02 (mmoles/liter)
0.8 1.0 1.2
• 5 • 32• •• ••
• • • • • 2 . • • •
• •
•• • • • • •
• • .. •
• • •
•
1.4 1.6
• •
•
• data point
9 9 data points at same location
Figure 47. Decrease in silica concentrations with depth.
77
1.8 2.0
------------------------------ ----------------
1.00
222.70
444.40
666.10
887.80
~ 1109.50 .t::. a. Q)
0
1331.20
1552.90
1774.60
1996.30
2218.00
1.5 4.5
9998654522 3 2 58665• 22 2•• • 35•2 • • • •• 342•• ••2 • 6863823•• • 7976•• • • 596772•• • 97983 •• 999•35 • 799633 • ~998• • • • 99342••• • 7933 2• 2 2994.•• 5944• • 7963• 3944 464•• • 242 •22 •
232 •• • ••2 27•
2 2• 22• •
3 • • 2• • • •• 2 • • •
• 2 •
2• 3 • 2
• •
•
•
•
7.5
• •• •
••
• 2
10.5
•
S04 (epm)
13.5
• •
•
16.5 19.5
• • • •
22.5 25.5
• data point
9 9 dolo points at same location
28.5
•
Figure 48. Sulfate reduction with depth. Loss of sulfate implies greater reducing conditions at greater depths.
78
•
.e
CARBON-14 DATING OF WILCOX AQUIFER, GROUND WATER
Charles W. Kreitler and David Pass
Ground-water age dating in the Wilcox aquifers by carbon-14 indicates progressively older waters down the structural and potentiometric dip. Uncorrected ages vary from approximately 10,000 to 30,000 years old.
Specific questions involving ground-water flow in the Wilcox aquifer are as
follows: (1) Are flow velocities in the shallow part of the aquifer significantly higher
than in the deeper aquifer? (2) Is there significant leakage from the overlying Queen
City Formation into the Wilcox aquifer? (3) Because strata are uplifted around many
salt domes, are dome areas recharge zones within the artesian part of the aquifer?·
(4) Does saline water leak upward from deeper formations along the flank of the
domes? These questions can be resolved partly by using carbon-14 absolute age dating
of the bicarbonate ion in ground waters.
Maximum measurable age of a carbon sample by conventional carbon-14 tech
niques is approximately 50,000 years. Bicarbonate ion in ground-water samples results
from (1) the generation of carbon dioxide in the soil zone of the recharge area, and
(2) the dissolution of carbonate ·minerals or the decomposition of organics in the
aquifer. Carbon-14 is added to the ground-water bicarbonate ions only by carbon
dioxide from the soil zone. Other potential sources are probably significantly older
than several half lives of carbon-14 and, therefore, represent "dead" carbon. In
·calculating the age of bicarbonate in ground water by carbon-14, a correction factor
must be included to account for dead carbon. Carbon-14 dates presented in the
following section are uncorrected values.· A correction factor has yet to be
determined; corrected values will be presented at a later time.
Nine water samples from the western outcrop of the Wilcox Group to the Elkhart
"Graben have been analyzed (fig. 49). Wells along the Wilcox outcrop are relatively
shallow, whereas wells in the artesian section are the deepest wells penetrating the
Wilcox. Samples were collected from approximately the same stratigraphic horizon
from outcrop to the deepest part of the Wilcox aquifer. Table 4 lists information
about the wells sampled for these analyses.
From the recharge zone into the deepest part of the basin, the waters become
progressively older from approximately 10,000 years in outcrop (locations 1 and 2) to
approximately 28,000 years south of the Elkhart Graben (location 9). The water
sample from the Keechi Dome area (location 5), where the Wilcox Group crops out
79
because of doming and where evidence exists of substantial leakage through the
Rekla~ aquitard, is significantly younger than shallow ground waters near the regional
Wilcox outcrop belt.
Shallow ground- waters sampled in the outcrop of the Wilcox aquifer are older
(approximately 10,000 years) than expected. Sample locations probably represent
discharge zones rather than recharge zones of the outcrop (locations 1 and 2). These
"old" ages are additional evidence for topographic control of ground-water flow in the
Wilcox system.
80
--------------------------------------------------------------------------
EXPLANATION
,:;# Wilcox-Corrizo ground-woter __...,, flowline
0 Wilcox-Corrizo outcrop
.. - ..... Watershed divide
• Flowing well
t:. Salt dome
1 I
I 1 ..... .....
I
I
0
0
Figure 49. Location of ground-water samples from Wilcox carbon-14 age dating. Numbers 1 through 9 indicate locations. additional information on samples.
81
50 mi
50 km
aquifer used for Table 4 provides
Number on map
1
2
3
4
00 N
5
6
7
8
9
Table 4. Carbon-14 data on profile from Wilcox outcrop through Keechi Dome to southern edge of East Texas Basin · (sample locations on figure 4-9).
Screened interval 14 C age State well no. Aquifer (below land surface) (uncorrected) Comments
34-49-103 Wilcox 196-260 11 '030~290 Shallow outcrop, but may be in discharge zone
34-49-806 Wilcox 395-445 9' 120~100 Shallow outcrop, but may be in discharge zone
38-02-302 Wilcox 1 ' 154-1 ' 192 21 '260~340 Near a gas field
38-03-701 Wilcox 1,070-1,085 17 ,860~190 Upgradient from 1 '1 05-1 '141 Keechi Dome
38-11-102 Wilcox 746-756 11 '230~ 480 Flank of Keechi 819-829 Dome
38-11-603 Wilcox 1,485-1,540 18,840~290 Downgradient from Keechi Dome
38-19-303 Wilcox· 1,614-1,700 19' 100±_ 600 South of Palestine, Texas
38-20-604 Wilcox 1,675-1,720 23~420~1,050 Just north of 1,753-1,822 Elkhart Graben
38-21-705 Wilcox 1,695-1;795 27 '890~2,890 Just south of Elkhart Graben
PETROGRAPHY AND Dlf..GENESIS OF WILCOX SANDSTONES
Shirley Dutton
Drill cuttings of Wilcox sandstones from 40 wells show a wide variation in mineral composition. Diagenetic features include calcite cement and rare clay rims and leached feldspars.
Drill cuttings of Wilcox sandstones from depths of 15 to 849 m (50 to 2,875 ft)
were sampled from 40 wells in the East Texas Basin (table 5, fig. 50). Porosity,
texture, and grain relationships are difficult to observe in cuttings, but· mineralogic
composition can be determined. Cements can often be recognized in larger fragments.
Wilcox sandstones exhibit a wide variation in composition, ranging between
quartzarenite, litharenite, and arkose (fig. 51). Most samples contain about 75 percent
quartz and more rock fragments than feldspar. Orthoclase feldspars are more
abundant than plagioclase. Some samples contain abundant shale clasts, which may be
Wilcox shale that was mixed with the sand during drilling. Carbonate rock fragments
and glauconite are locally abundant. Metamorphic and igneous rock fr~gments
constitute about 3 percent of the framework grains.
Minor diagenesis has occurred in these shallow sandstones. Micritic and sparry
calcite cements are present in several cutting samples. One indurated sample was
available from the Navarro no. 1 Greenwood well in Anderson County. Sand grains are
cemented by clay rims, and glauconite composes up to 28 percent of the framework
composition. Leached feldspars are_ present in this sample and in several samples from
cuttings.
Similar diagenetic changes have been observed in shallow Frio (Oligocene)
sandstones of the Gulf Coast (Bebout, Loucks, and Gregory, 1978). Leached feldspars,
clay rims, and sparry calcite cement all formed near the surface and in the shallow
subsurface.
83
---------~~~-~~
EXPLANATION
o Well control 0
0
20 30 Miles
10 20 30 40 Kilometers
-~
Figure 50. Location of wells in the East Texas Basin sampled for cuttings of Wilcox sandstones. Location numbers refer to table 5.
84
Arkose
FELDSPAR
0 0
QUARTZ
0 oco
0 0 0
0 0
0
0
Lithic Arkose Feldspothic Lithorenite
0
0 8 ° 0
co 0 0
0
Lithorenite
ROCK FRAGMENTS
Figure 51. Classification of sandstones from the Wilcox Group using Folk's (1974)' classification system.
85
Table 5. Wells sampled for cuttings of Wilcox sandstones.
BEG County number- Operator Well name
Anderson 1 Humble · Ill Lucy Ruff 2 Layne-Texas 113 City of Palestine Water Well 3 Navarro Ill Greenwood 4 Texas Co. Ill Durden 5 Tidewater-Seaboard Ill Rampy
Camp 1 Tidewater Ill Roberts 2 Stephens & Peveto Ill Smith
Cherokee 1 American Liberty Ill Cobb-Holman 2 Grelling Ill Batton. 3 Humble lllB Stephens 4 Humble Ill Carter 5 Humble Ill New Birmingham
Freestone 1 Byars & Peveto Ill Riley 2 Humble Ill Bonner
Henderson 1 LaRue Ill Robbins 2 Stano lind Ill Dupree 3 Lone Star Prod. Ill Allyn Est. "B" 4 Edson Petr. Ill Miller
Hopkins 1 Donnie Petr. Co. Ill Welborn
Houston 1 Jack Frost Ill Adams 2 American Liberty Ill J. A. Bean 3 Shell Ill G. E. Dorsey
Hunt 1 Stano lind Ill Bickley 2 Humble Ill Norman
Leon 1 Lone Star Prod. 111-C Shell-Page
Morris 1 B. Fields Ill Pruitt 2 Selby Ill Browne 3 C. B. Zuber et al. Ill G. A. Conner
Nacogdoches 1 Fain et al. Ill Yates Douglas Explor.a tion Ill Hayter
Navarro 1 Bateman et al. 1/lS.P.Love
Rains 1 Humble Ill Mainard
Smith 1 Humble Ill Shamburger 2 Skelly Ill Chisum
Titus 1 W. M. Coates Ill Ben Lackey 2 Humble Ill Stevens 3 Humble Ill Searcy
86
County
Upshur
VanZandt
BEG number
1
1
Table- 5 (continued).
Operator Well name
Carpenter 111 White
Ellison 111 Furrh
87
SURFACE GEOLOGY AND SHALLOW BOREHOLE INVESTIGATIONS OF OAKWOOD DOME--PRELIMINARY STUDIES
Edward W. Collins and David K. Hobday
On Oakwood Dome, Claiborne (Eocene) strata constitute a complex facies association that may indicate that structural uplift was contemporaneous with sedimentation over the dome. Quaternary deposits apparently were not displaced by dome movement, but data are limited. Geomorphic anomalies may reflect recent differential movement.
Claiborne strata are exposed in typical domal configuration over Oakwood Dome
(fig. 52). Structural dips of Claiborne units are up to 20 degrees. Superimposed
Quaternary terrace deposits appear unaffected by dornal structure. A representative
north-south cross section of the Claiborne Group (fig. 53) displays about 80 m (262 ft)
of domal uplift on the top of the Carrizo Formation. Core descriptions from borehole
OK-115 (fig. 55) were summarized on the illustration for lithologic characterization,
and paleoenvironmental interpretations were based on studies of cores and local
outcrops, on correlation with exposures studied in adjacent areas of Leon, Freestone,
and Anderson Counties, and on regional subsurface mapping by Guevara and Garcia
(1972).
The Carrizo Formation crops out in stream channels over the central Oakwood
Dome area. Sands ·in the lower part of the formation are interpreted to be upper . .·
alluvial plain deposits, whereas the finer grained upper part reflects a lower alluvial
plain environment with extensive floodbasins. Thinning of approximately 10 m (30 ft)
from borehole OK-115 to borehole OK-102 may indicate domal uplift concurrent with
deposition.
The Newby Member of the overlying Reklaw Formation contains abundant
glauconite and an open shelf fauna, but a trace fossils assemblage is characteristic of
shallow water. Preliminary indications are that the shallowest water may have been
situated directly over the dome. The Marquez Member of the Reklaw Formation
represents restricted marginal marine conditions. Crevasse splays and small bayhead
deltas were sites of coarser grained clastic sedimentation.. .
The Queen City Formation comprises coarsening-upward, shoal-water,
Guadalupe-type delta sequences and polymodally crossbedded marginal marine sand
shoals. The basal sand unit thins toward the dome and is a possible indication of the
effects of positive topographic expression on sedimentation.
88
Quaternary terrace deposits crop out over the southern half of Oakwood Dome.
They vary from silty clay to poorly sorted sand and gravel. A series of shallow
boreholes permits delineation of thickness and lateral extent of these deposits.
Although the erosional base of the Quaternary displays minor variations in elevation,
the resulting cross sections (figs. 54, 55, and 56) indicate that there is no discernible
warping or faulting of the Quaternary deposits.
Three normal faults are visible in outcrop, but these cut only Claiborne strata,
which are downthrown away from the dome. Additional fracture zones are common,
and a prominent pattern of radial.lineaments is probably fault controlled. None of the '
faults can be shown to displace Quaternary strata, but because of poor exposures and
erosional modification of the terrace surface, displacement cannot be entirely
discounted.
Certain parts of the dome have been subjected to modern incision; elsewhere on
the dome are small, asymmetrical Holocene t~rraces. These patterns of trenching and·
aggradation could be a response to minor dome movement. Borehole OK-105 in a
floodplain area encountered 10.7 m (35ft) of modern alluvium. Three hundred meters
(1,000 ft) upstream from this locality, Eocene bedrock is exposed. Approximately
1 km (3,400 ft).south of borehole OK-105, ground level resistivity showed that the
modern alluvium is 3 m (10 ft) thick. These data suggest thicker sediment accumula
tiqn over the dome, which may be explained by climatic variations influencing
drainage or change of base level related .to solution and collapse of the dome.
89
EXPLANATION
b';~~i; I Modern alluvium
g; ~ Quaternary terrace 0
~ li/~Ej Queen City Formation
~ l:::::ii(:l Reklaw Formation ~ · ........... . <l j';';';;;;;;;r;;;;;;;;;l • . d :rrstmm Carma Format1on
0
0
} QUATERNARY
}TERTIARY
19_y Strike and dip
~- .... Fault, dashed where inferred or covered
~~ Fractures
OK-IOI• Borehole
--1000- -1000 ft contour of salt
lmi
lkm
Figure 52. Surface geology of Oakwood Dome showing borehole locations.
90
Fl FVATION 450
D OK-101 OK-102
130 G.L.• +410' G.L.•+370
00
110 350
100
300 90
:: E 80
250
70
200 60
50 150
40
100
0 100 200 300m
0 500 1000 It
WILcox GRoup·
~~~ .~3
ie «8
OK-107 G.L..,375'
OK-108 G.L.•+370'
OK-119 OK-115 G.L.=•355' G.L.:~:+315'
o'
OK-115 Core Descriptions
;' ~~~1e/~~~~•'"'~tab~:d~dw:!'; o bedding~ cross laminated; n· low·ongle foresets; lignilic;
-g;-fn~~icf3ecisrrtYCTOvtlg~ ~!~~~~~~dr; ~~dn;i·n~~vy, a ; = ripple cross laminations; N~ burrowed; starved ripples; g n li~~ltlc; slightly gtouco-
_CD __ .!!!,I~-------fine sand with few thin
(1)3:g? cloy beds; homogeneous ;,r~!:!,. to low angle foresets; ::i'O cloy drapes on foresets;
€ c:loy clotts common.
shale, silly to sandy; thinly laminated to plane, wavy, and lenticular bedding; glouconllic; bioturbated; shell froQments; carbonaceous.
:E~~ medium to fine sand, ~- ~ "O some coarse sand; well :;, §: ~ sorted; slightly lignitic.
Figure 53. North-south cross section throl,.!gh Claiborne Group over Oakwood Dome.
elevation A OK-113 ft
+360
+350
+340
+330
+320
+310
m +110
+105
+100
+ 95
0 I 0
25 I
100
50 75 I
200
Quaternary Soil z?ne at t?P.i terroce matenal cons1stmg of sandy ~lay to medium
e sancf w1th .fe~ pebbles of metamorphiC rock, chert, ironstone.
OK-118
m I
300ft
Claiborne Interbedded very fine sand, silty clay, and clay (m m-size layer~); planar and wavy beddmg.
OK-117 AI·
OK-120
... ;
··~· . . ... ·.·• --. ·, .. .. . . ..•\, . .-• .. ·· .
. -~·· .. -.- 'o-.-.--.... ,
. : ·. ·-. -. -·.-.--~· ·. ·-~: .:: .:·~ .· ... J: ·. ~. ·-· -· _·_·: :: ~.· ~· .... -.:.....:....:.· ·'.
: ·'·· .... ·· ..... . ...-----···:· ..... :.:::·2 .· ·'' . •: . . , .
·.· ... · ..
-Interbedded fine sand, slightly clayey, and laminated clay to silty clay; burrowed; lignit1c; low-angle foresets.; gypsum.
Figure 54. Cross section A-A' through Quaternary deposits.
91
8 elevation ft m
+360 +110 OK-I09
+350 OK-110
+340
+300
+90
+290
0 25 50 75 m +280 I 'I I I I I
0 100 200 300 ft
Quaternary Soil zone at top; terrace material consisting of sandy c;loy to meaium sand woth few pebbles of metomorphoc rock, chert, ironstone.
Claiborne Interbedded very fine sand, s!lty cloy, and cloy (m m- soze Ioyer~); planar and wavy beddmg.
OK-III
OK-112
gl
OK-1' 7
Interbedded fine' sand, slightly clay·ey, and laminated cloy to silly cloy; burrowed; lignitic; low-angle foresets; gypsum.
Figure 55. Cross section B-B' through Quaternary deposits.
elevation ft m
+360 +110
+350
+105 +340
+330 +100
+320
+95
c OK-109
• • • •• 0 --· .. . , , ..
0 I 0
25 I I
100
' ... · .. · ... .--.-~·
50 75 m I I I I
200 300ft
Quaternary Soil Z?ne at t?P~; terrace matenal consrstmg of sandy ~loy to medium sand w1th few pebbles of metamorphic rock, chert, ironstone_
Claiborne Interbedded very fine sand, silty clay, and clay (mm-size layers); planar and wavy bedding.
Interbedded fine sand, slightly clayey, and laminated clay to silty clay; burrowed; lignitic; low-angle foresets·, gypsum.
Figure 56. Cross section C-C' through Quaternary deposits.
92
ANALYSIS OF SELECTED STREAM DRAINAGE SYSTEMS IN THE EAST TEXAS BASIN
Owen Dix
The study of link length distributions from drainage basins in the East Texas Salt Dome Basin indicates that four of six salt domes studied are overlain by mature drainage. Two of the domes (Oakwood and Grand Saline) display anomalous link length distributions, an indication that surface movement above these domes has been more recent.
This study was designed to determine whether stream drainage patterns above
selected salt domes have been affected by recent movement involving either uplift,
graben formation, or solution collapse. East Texas is geologically and structurally
suitable for stream drainage analysis since the sediments are flat-lying, the relief is
subdued, and the Tertiary formations are similarly resistant to erosion. A number of
characteristic drainage patterns are directly related to relief, which is in turn
determined by structure, litho logy, and vertical movements. These character is tics
include drainage density and various link length and link frequency distributions. A
link is the fundamental unit of a channel network, and was defined by Shreve (1966) as
a section of channel between a source and a junctio.n (exterior link) or between two
junctions (interior link).
With a mirror stereoscope, active stream channels were traced from low-altitude
aerial photographs (scales ranging from 1:16,900 to 1:25,500). Oakwood, Palestine,
Keechi, Grand Saline, Hainesville, and Van Salt Domes were selected for this study.
For comparative purposes, 10 non-dome drainage basins were also selected. Each of
the non-dome basins is developed on a single stratigraphic unit (either the Wilcox
Group, the Queen City Formation, or the Sparta Formation). Drainage patterns over
the six domes range from centripetal-annular (Oakwood and Palestine Domes) to
subdendritic (Keechi, Hainesville, and Van Domes). Grand Saline displays a centripetal
pattern, and the non-dome basins all have dendritic drainage.
Drainage densities over the six salt domes vary from 2.9 km/km2 (Van Dome) to
5.7 km/km 2 (Oakwood Dome) and generally increase with increasing relief (fig. 57).
Mean drainage density for the 10 non-dome basins is 4.1 km/km 2; those basins located
on the Queen City Formation tend to have a higher density (4.5 km/km2) than basins
located on the Wilcox Group (4.1 km/km 2) and the Sparta Formation (3.5 km/km 2).
Emphasis was placed on exterior links since these are the most sensitive to
variations in the environment (Abrahams and Campbell, 1976). Exterior links have
93
been subdivided into source (S) and tributary-source (TS) links (Mock, 1971). An S link
is an exterior link that combines with a second exterior link, and a TS link is an
exterior link that joins an interior link (fig. 58). Abrahams and Campbell (1976) have
concluded that these two link types have significantly different length distributions in
natural drainage systems. Application of the Chi-square and the Kolmogorov non
parametric statistical tests to the East Texas data indicates that S and TS link
distributions are statistically different (at the 0.05 level of significance) over some of
the domes studied, and that these link· distributions vary according to relief and
drainage density as follows:
(1) S and TS links from drainage basins with high drainage densities and relief
ratios tend to have the same length distributions. Drainage over Grand Saline and
Oakwood Domes falls into this category (fig. 59), as does drainage from one of the
non-dome basins. Short links are abundant, and both distributions exhibit high kurtosis.
Drainage of this type is thought to be relatively youthful and has yet to undergo
extensive stream abstraction. Composition of drainage over Grand Saline Dome may
have been affected by the destruction of natural vegetation over a large proportion of
the area. Over Oakwood Dome, oil field activities also may have influenced stream
drainage.
(2) As relief is reduced, exterior links are abstracted (Abrahams, 1977), and
drainage density decreases. This process generally commences at the center of the
basin (Schumm, 1977, p. 64-66) and leads to unequal Sand TS length distributions (figs.
59 and 60). This difference in length distributions has been attributed to a tendency
tor TS llnks to increase in length downstream in association with increased vailey size
(Abrahams and Campbell, 1976), but may also be controlled by the different topologi
cal positions occupied by S and TS links. The S link distribution is essentially the. same
as that for S links of type (1 ), but longer TS links are more abundant. Palestine,
Keechi, and Hainesville Domes, together with 9 of the 10 non-dome basins fall into
this category, which is typical of mature drainage basins.
(3) Where relief is very low, S and TS links again tend to have the same length
distributions, but with a considerably greater mean length than type (1) above. This is
because of maximum stream abstraction and the uniform size of stream valleys. Van
Dome falls into this category (fig. 59). Progression from type (1) to type (3) is shown
in figure 61. Figure 62 shows the inverse relationship between relief ratio and mean
exterior link length.
These data, therefore, suggest that drainage over Oakwood and Grand Saline
Domes is younger than that over the remaining four inland domes. Because of the low
resistance to erosion of the East Texas Tertiary sediments, lithology and structure are
94
not thought to have controlled the nature of these drainage patterns (that is, the
drainage is not superposed). This implies more recent surface movement above these
two domes. Of the remaining inland domes, link distribution .of the Palestine is most
similar to. the Oakwood type (fig. 59). Evidence of pre-existing topographic highs over
Keechi and Hainesville Domes includes the drainage patterns and the presence of
encircling areas of higher relief.
95
6
• OAKWOOD
C\1 0
E 5 • ~ GRAND SALINE 0 ......... E ~
0 0
>-!::: CJ)
4 z w 00
0 • G
w PALESTINE
(!) <l • 00 ue KEECH! z HAINESVILLE -<l 0:: 3 0 •
VAN
2 ~--------~----------~--------~----------._--------~ 0 .010 .020 .030 .040 .050
RELIEF RATIO
Figure 57. Relationship between relief and drainage density. Solid dots represent domes, and circles represent non-domes.
s s
L,
TS
Figure 58. Diagram showing source (S) and tributary-source (TS) links.
96
.300
>-~ .200
"' ::> fil a: ... "' ;;>
!;i ~ .100
"' a:
OAKWOOD DOME
SOURCE LINKS
(82)
0 U---L---L---L-~~~
.300
>-~.200 "' ::> 0
"' a: ... "' > !;i iiJ.IOO a:
0 100 201!) 300 400 500
GRAND SALINE DOME
SOURCE L1 NKS
(100)
0 U---L---L---L---~~
.300
>-~.200 "' ::> 0
"' a: ... "' > ~ ~ .100
"' a:
0 100 200 300 400 500
PALESTINE DOME
SOURCE L1 NKS
(158)
LINK LEN.GTH (METERS)
TRIBUTARY- SOURCE LINKS
(64)
0 100 200 300 400 500
TRIBUTARY- SOURCE LINKS
(Ill)
0 100 200 300 400 500
TRIBUTARY -SOURCE LINKS
(186)
LINK LENGTH (METERS)
Figure 59. Source and tributary-source link length distributions for drainage basins overlying East Texas salt domes. Numbers in parentheses indicate population size.
97
.300 KEECHI DOME
>-SOURCE LINKS TRIBUTARY-: SOURCE LIN~S u
.200 z .... (204) (165) :::;)
0 .... 0:: .... .... > i= <( .100
. ...J .... 0::
0 JJ j] 0 100 200 ;,oo 400 :500 >:500 0 100 200 300 400 500 >500
.300 HAINESVIL~E DOME
>-TRIBUTARY- SOURCE u SOURCE LINKS LINKS z .200 ....
(188) (180) :::;)
0 .... 0:: .... .... > i= <( .100 _. IIJ: 0::
0 rllJ j] 0 100 200 300 400 500 >500 0 100 200 300 400 500 >500
.300 VAN DOME
>-u SOURCE LINKS TRIBUTARY-SOURCE LINKS z .200 .... :::;) (198) (146). 0 .... 0:: .... .... > i= <(
.100 ...J ....
j 0::
0 JJ 0 100 200 300 400 500 >500 0 100 200 300 400 500 >500
LINK LENGTH (METERS) LINK LENGTH (METERS)
Figure 59 (continued).
98
.400
.300
,... u z .., ;j
0 .., a:: .... 200 .., ~ ,_ -t ....1 .., a::
.100
.300
,... u z .., ;j
~.200 a:: ... .., > !;i ....1 .., a::.IOO
0
.200
,... u z .., ;j
0 .., a:: .... 100 .., > ~ <l ....1 .., a::
0
COW SLASH CREEK
SOURCE LINKS
(132)
HAYS BRANCH
SOURCE LINKS
(54)
0 100 200 300 400 500 > 500
0
LINK LENGTH (METERS)
GILADON CREEK
SOURCE LINKS
(82)
TRIBUTARY-SOURCE LINKS
(125)
L.l...--....l.-~~r-IJ 0 100 200 300 400 500 >500
TRIBUTARY-SOURCE LINKS
(50)
0 100 200 300 400 500 > 500
TRIBUTARY-SOURCE LINKS
(71)
LINK LENGTH (METERS)
Figure 60. Source and tributary-source link length distributions for non-dome drainage basins in East Texas. ·
99
JOO I c I
r r r u u u ~.~
z z ~·~ ~~
~ 0 0 0 w w w ~ ~ ~ ~ ~ ~
w w w > > >
~ ~ ~JOO ~ ~JOO ~@ w ~
w w ~ ~
o~~---L--~--~~~~--~ o~~--~---L--~--~~~~ o' f I I I I 1 -::r:=--1
0 200 400 600 0 200 400 600 0 200 400 600 LINK LENGTH (M) LINK LENGTH (M) LINK LENGTH (M)
Figure 61. Variation of source and tributary-source links with drainage maturity: (A) high-relief; (B) moderate-relief; and (C) low-relief drainage.
300
U> IL. w
25o I ..
1- VAN w ~ ...... I 1-
Lao~ 0
PALESTINE • 0 • KEECHI
HAINESVILLE • 0 0
0 _J
11: 0
I 0 11: w 1-X w 150
1 0
z GRAND SALINE • <(
0 w :!!: OAKWOOD •
'I
0
0 I .
100 0 .010 .020 .030 .040 .050
RELIEF RATIO
Figure 62. Inverse relationship between relief ratio and mean exterior link lengths.
100
STUDIES OF LINEAMENTS IN EAST TEXAS
Owen Dix
Low-altitude aerial photographs are being used to identify lineaments in the East Texas Salt Dome Basin. Regional lineament trends are inferred to be related to basement tectonics, whereas modifications to these trends in the vicinity of salt domes probably relate to salt dome structures. The age of such structures is critical.
Lineaments have ·been defined as rectilinear or curvilinear mappable surface
features that reflect subsurface phenomena (O'Leary and others, 1976). Recent
studies indicate a close. relationship between basement tectonics and superficial
structural patterns (Gay, 1973, p. 4; Frost, 1977). To investigate this relationship
further, an area of approximately 15,400 km 2 (6,000 mi2) in East Texas is being
studied to determine regional lineament trends and the effects of salt dome tectonics
on these trends (fig.· 63).
Lineaments are marked on stereoscopically viewed, low-altitude, black-and
white aerial photographs. The lineaments are marked by features such as straight
stream channels, changes in topography, and tonal changes. To date, 95 percent of the
photographs have been marked and double checked; triple checking is nearing
completion. Ultimately each lineament will be giyen a set of coordinates, and the
data will be computerized. As this will be done only on completion of triple checking,
an area covered by sixteen 2.3 m by 2.3 m (7 .5 ft by 7.5 ft) quadrangles was selected
for initial analysis (fig. 63). This study area was divided into a northern subarea
containing no salt domes and a southern subarea containing Keechi, Palestine,
Oakwood, Bethel, and Butler Domes.
Lineaments range in length from 0.4 to 4.9 km (1,360 to 16,660 ft), the mean
being 0.9 km (3,060 ft). Since lineament length is considered important (Frost, 1977),
the total length of lineaments within each 10° angular interval has been plotted on
rose diagrams (fig. 64A). Mean length of lineaments tends to increase with the total
number of linea"ments in each 10° interval, which results in an enhancement of peaks
when total lengths are plotted (Haman and Jurgens, 1976). Application of the Chi
square one-sample test (Siegel, 1956, p. 42-47) in the northern subarea revealed four
statistically significant peaks located on bearings of 030°, 055°, 295°, and 330°
(fig. 64B). These four peaks constitute two orthogonal sets (Gay, 1973, p. 3-6), which
may represent the regional lineament pattern of the Northeast Texas Salt Dome Basin.
The 055° trend, which is better represented here than in the southern subarea, may
101
have been enhanced by the Mexia-Talco Fault System located approximately 30 km
(18.7 mi) to the northwest (fig. 63). It is interesting to note that these peaks agree
well with lineament peaks in Precambrian and Paleozoic sediments of the San Saba
area (020°, 060°, 295°, 330°) and the Palo Pinto area (030°, 060°, 295°, 345°), Central
Texas (Brown, 1961).
A rose diagram for the southern subarea also shows four statistically significant 0 0 0 0 . . .
peaks at azimuths of 025 , 060 , 295 , and 325 (fig. 64B). These peaks correspond
well ·to those in the northern subarea, although they are not as pronounced. This is
probably the ·result of interference by randomly and radially" oriented boundary
lineaments around the salt domes. Furthermore, east-west lineaments are noticeably
more abundant .in the southern subarea, the quadrangle containing Oakwood Dome
having a pronounced peak at 085°. This may be related to the trend of the Elkhart
Mount Enterprise Fault Zone, which has a west-southwest trend east of Oakwood
Dome. There "is an increase in the number of lineaments around p'alestine, Oakwood,
and to a lesser extent Keechi Domes. . Lineaments over Oakwood Dome tend to be
oriented east-west, and the frequency of lineament intersections increases. Over
Palestine Dome, the lineaments tend to be radially oriented. However, until data from
the entire study area are available for analysis, no additional conclusions can be
drawn.
102
ODALLAS
N
OKLAHOMA
TEXAS
1/
/Limits of entire study area
~--------~~----~
subarea
oTyler
ARKANSAS
r 0 c (f)
l> z l>
/..,.....- ...... ~
e Salt dome
_/Fault
0
outhern subar~a
BOkm
// MOUNT ENTERPRISE FAULT ZONE
Figure 63. Location map of lineament study area.
103
A. N
484 LINEAMENTS
B. N
60km 40 20 0 20 40 60km
874 LINEAMENTS
Figure 64. Rose diagrams of lineaments using total lengths for each 10° sector: (A) northern subarea; (B) southern subarea. Asterisks represent peak significance; ** = 0.05 level of significance, * = 0.10 level of significance.
104
THE QUEEN CITY FORMATION
David K. Hobday and Edward W. Collins
The Queen City Formation of the East Texas Basin includes five distinct sedimentary facies: fluvial, deltaic, barrier, tidal delta, and tidal flat. Oakwood Dome may have had topographic expression during deposition and thereby influenced facies characteristics and distribution on a local scale.
Regional patterns of facies distribution were established for the Queen City
Formation (figs. 65 and 66) to determine the extent to which salt domes may have
influenced the depositional environment and thereby provided information concerning
dome growth history. Previous facies studies of the Queen City Formation in the
region were carried out by Guevara and Garcia (1972).
Five facies are characterized by distinct assemblages of physical and biogenic
structures. In the northwest, an alluvial plain was traversed by rivers of fluctuating
discharge and seasonally changing channel geometry, which included both braided and
meandering components. Small fluvially dominated deltas developed along the western
half of the embayment, prograding across the shallow Weches shelf. Eastward of the
area of active deltaic sedimentation were low coastal barriers, which may have
formed contemporaneously as strike-fed features, or by subsequent processes of delta
destruction. Flood-tidal deltas were deposited on the landward sides of barrier inlets
and were particularly widespread during initial phases of marine transgression near the
end of Queen City deposition. Inner parts of the Queen City embayment experienced
subdued wave activity and enhanced tidal processes and were c.overed by shallow
subtidal sand shoals and broad tidal flats comprising alternating layers of sand and
mud.
Although sufficient data are currently unavailable for a definite conclusion, local
facies characteristics suggest that Oakwood Dome may have existed as a positive
topographic feature during Queen City deposition. This pattern is also emerging in
ongoing studies of the underlying Reklaw Formation.
105
0 5 10 15 20 25km.
0 10 15mi.
;- .. ! OTHER CLAIBORNE FMS. PLL S QUATERNARY ~JTI1\~)\ QUEEN CITY WILCOX f - f FAULT n ~ SAMPLE NUMBER
Figure 65. Outcrop area of the Queen City Formation in East Texas; paleocurrent patterns measured at major outcrops.
. \ .. ~
/ Major tidal flow patterns
·\ TIDAL
EMBAYMENT
SABINE
UPLIFT
I
'
"
0 50 Mi ~~-r~~~--~--~
0 80 Km
' ' \
Figure 66. Schematic paleogeographic reconstruction of major Queen City facies in the East Texas Embayment.
107
\
' \ \ \
ACKNOWLEDGMENTS
This research was supported by the U.S. Department of Energy under contract
number DE-AC97-79ET -44605. The writers would like to acknowledge the staff of
Law Engineering and Testing Co. for their help in collection of data. Permission from
Teledyne Exploration Co. to publish seismic data is greatly appreciated.
108
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