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TRANSCRIPT
UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY
BOREHOLE-GRAVITY SURVEYS IN BASIN-FILL DEPOSITS OF
CENTRAL AND SOUTHERN ARIZONA
by
Patrick Tucci, James W. Schmoker, and Stephen L. Bobbins
Open-File Report 82-473
1982
This report is preliminary and has not been reviewed for conformity with
U.S. Geological Survey editorial standards. Any use of trade names is for
descriptive purposes only and does not imply endorsement by the USGS.
INTRODUCTION
The borehole-gravity surveys described here were undertaken as part of
the Southwest Alluvial Basins Study, which is one of a number of U.S.t
Geological Survey planned or ongoing regional aquifer studies. The
objective of the borehole-gravity surveys was to investigate general
relations between density and depth in the basin-fill deposits of central
and southern Arizona. Such deposits form the major aquifers of the region
and store large volumes of ground water.\
Basin-fill deposits penetrated by six wells in Butler Valley, Vekol
Valley, Avra Valley, and the Tucson basin (fig. 1), in central and southern
Arizona, were logged in January, 1980, with the U.S. Geological Survey-
LaCoste and Romberg borehole gravity meter. These cased wells were
originally drilled for water supplies or for aquifer tests.
Subsurface depths in this report are given in feet, in conformance with
common usage and understanding of well data. The multiplying factor to
convert feet to meters in 0.3048.
GEOLOGIC SETTING
The borehole-gravity data described here are .from intermontane basins
(grabens) in or adjacent to the Sonoran Desert section of the Basin and
Range physiographic province (Fenneman, 193D. Mountains (horsts) bounding
the basins consist of igneous, metamorphic, and sedimentary rocks ranging
from Precambrian through Cenozoic in age (Wilson and others, 1969).
31
115
31'108'
I I50 100 KILOMETERS
EXPLANATION
BOUNDARY OF SOUTHWEST ALLUVIAL BASINS STUDY
BUT-1 WELL BUT-1 is well designation
Figure 1.--Locations of wells logged in this study.
The basin-fill deposits, described by Scarborough and Peirce (1976, p.
253) as "the sedimentary group that was deposited in basins created by the
Basin and Range disturbance", are up to about 9,000 ft thick (Eberly andr
Stanley, 1978, p. 938). They consist of gravel, sand, silt, and clay, and
locally include interbedded volcanic rocks and evaporites (Scarborough and
Peirce, 1978). In general, the clastic sediments grade from coarse grained
at basin margins to fine grained in the centers. Basin-fill deposits in
the study area have not been formally named except in the Tucson basin,\
where Davidson (1973) subdivided them into the Tinaja beds of Miocene and
Pliocene age and the Fort Lowell Formation of Pleistocene age.
BOREHOLE-GRAVITY MEASUREMENTS
The U.S. Geological Survey-LaCoste and Romberg borehole gravity meter
(described by McCulloh, LaCoste, and others, 1967; McCulloh, Schoellhamer,
and others, 1967) was used to carry out borehole-gravity surveys in the six
wells located in Figure 1. The borehole gravity meter has a radius of
investigation of tens of feet. Density values derived from
borehole-gravity measurements are not significantly influenced by casing,
borehole rugosity, or formation damage caused by .drilling.
Fundamentals of borehole-gravity logging and data interpretation,
considerations of the effective radius of investigation, and applications
to geologic problems have been discussed by many authors, including Smith
(1950), Goodell and Fay (1964), Howell, Heintz, and Barry (1966), McCulloh
(1966), Healey (1970), Beyer (1971), Jageler (1976), Hearst and McKague
(1976), and Scnraoker (1977a, b, 1978, 1979).
Subsurface gravity stations were located where wire-line or drillers'
logs indicated variations in formation properties. Additional stations
were located between formation breaks to establish details of density
variations. Densities determined from borehole-gravity measurements become
more accurate as vertical station separation increases, so that station
selection involves a tradeoff between stratigraphic detail and density
accuracy (Schmoker, 1978).
Drift control for the borehole-gravity surveys was established by\
station reoccupations; tidal corrections and terrain corrections were
applied to the borehole-gravity data. Principal facts for the
borehole-gravity measurements of this study are tabulated in Tables 1-6.
In the absence of complicating structural factors, the relation between
formation density and measurements of gravity in a borehole is given by
(McCulloh, 1966):
f = 39.124CF- 4g/ ^z) (1)
where J * s t*16 average formation density between two vertically separated
points in the borehole (g/cnr), F is the free-air vertical gradient of
gravity (mgals/ft), Ag is the measured difference in gravity between the
vertically separated points (mgals), and Az is the vertical separation
(ft).
Table 1. Well WKF, Avra Valley
Logged January 19, 1980
Station
12345
6789
10
1112131415
1617181920
2122232425
2627282930
3132
Depth (feet)
19.950.075.1
100.1144.0
194.0245.0286.0326.0365.0
406.0420.0462.0505.0548.0
610.0674.0746.0815.1860.1
910.1970.0
1,030.01,088.01,145.0
1,224.11,285.0
970.0746.0462.0
245.019.9
Greenwich mean time
18:4319:0019:1419:2619:37
19:4920:0120:1520:2920:47
21:0021:1321:2621:3921:50
22:0222:1422:2022:3222:41
22:5022:5623:0823:1823:29
23:3823:4824:0724:2324:42
25:0125:21
Uncorrected g ra vity
(milligals)
2,651.1612,652.5682,653.5622,654.6112,656.493
2,658.5482,660.6962,662.3892,664.0302,665.474
2,666.9602,667.4652,669.0492,670.6142,672.231
2,674.5782,676.9962,679.4862,681.8792,683.432
2,685.1522,687.2242,689.3452,691.3692,693.383
2,696.1512,698.2882,687.2782,679.5552,669.157
2,660.8272,651.287
Tide correction (milligals)
-0.014-.004+ .004+ .010+ .015
+ .020+ .025+ .029+ .032+ .034
+ .035+ .034+ .032+ .030+ .027
+ .023+ .018+ .016+ .010+ .006
+.001-.003-.009-.015-.022-
-.028-.034-.046-.055-.066
-.075-.083
Terrain correction (milligals)
+0.030+ .033+.036+ .040
"' +.047
+ .054+\061+ .067+ .073+ .078
+ .083+ .085+ .090+ .095+ .100
+ .108+ .115+ .123+ .131+.136
+ .142+ .149+ .155+ .162+ .168
+.177+ .183+ .149+ .123+ .090
+.061+ .030
Corrected gravity
(milligals)
2,651.1772,652.5972,653.6022,654.6612,656.555
2,658.6222,660.7822,662.4852,664.1352,665.586
2,667.0782,667.5842,669.1712,670.7392,672.358
2,674.7092,677.1292,679.6252,682.0202,683.574
2,685.2952,687.3702,689.4912,691.5162,693.529
2,696.3002,698.4372,687.3812,679.6232,669.181
2,660.8132,651.234
Table 2. Well MW-2, Avra Valley
Logged January 21, 1980
Station
12345
6789
10
1112131415
1617181920
2122232425 '
262728
Depth (feet)
99.4140.0180.0220.0260.0
300.0333.0365.0408.0460.0
510.0560.0600.1650.0700.0
750.1800.0850.0900.0950.1
1,000.0750.1510.0300.099.4
49.719.999.4
Greenwich mean time
15:5416:1916:2816:3816:48
16:5917:1317:2617:4217:57
18:0818:2318:3218:4418:53
19:0119:1219:2019:2919:38
19:4820:0420:2120:3420:46
20:5421:0321:20
Uncorrected gravity
(milligals)
2,636.6732,638.3892,640.1622,641.8232,643.477
2,645.1472,646.5062,647.9022,649.5362,651.469
2,653.3632,655.2002,656.7262,658.5412,660.336
2,662.0902,663.8582,665.5832,667.2702,668.951
2,670.6132,662.0592,653.3202,645.0962,636.583
2,634.4082,633.0372,636.570
Tide correction (milligals)
-0.084-.090-.091-.091-.091
-.091-.089-.086-.082-.076
-.072-.065-.060-.054-.049
-.044-.037-.032-.027-.021
-.014-.005+ .006+ .013+ .020-
+ .024+ .028+ .036
Terrain correction (milligals)
+0.070+ .081+ .092+ .102+ .113
+ .123+M32+ .140+ .151+ .164
+ .177+ .189+ .199+ .210+ .222
+ .234+ .245+ .257+ .268+ .279
+ .290+ .234+ .177+ .123+ .070
+ .057+ .049+ .070
Corrected gravity
(milligals)
2,636.6592,638.3802,640.1632,641.8342,643.499
2,645.1792,646.5492,647.9572,649.6052,651.557
2,653.4682,655.3242,656.8652,658.6972,660.509
2,662.2802,664.0662,665.8082,667.5112,669.209
2,670.8892,662.2882,653.5032,645.2322,636.673
2,634.4892,633.1142,636.676
Table 3. Well IP-1, Tucson basin Logged January 23, 1980
Station
12345
6789
10
1112131415
1617181920
2122232425
26272829
Depth (feet)
99.9150.0195.0235.0275.0
314.0333.0365.0400.1445.0
489.0518.0560.0603.0650.0
702.0760.0800.0850.0890.1
930.0980.1760.0518.0333.0
99.950.020.099.9
Greenwich mean time
15:5516:0916:2016:2916:42
16:5717:0617:2417:3617:52
18:0818:3318:5319:0719:20
19:3019:4419:5920:0920:18
20:2520:3520:5821:1621:31
21:5022:0122:1622:26
Uncorrected gravity
(milligals)
2,542.7242,544.7942,546.6712,548.3022,549.844
2,551.4042,552.1652,553.3882,554.6452,556.357
2,558.0732,559.1622,560.6912,562.2462,564.078
2,565.9852,568.0322,569.5262,571.2872,572.692
2,574.1512,575.8872,567.9762,559.0822,552.206
2,542.7462,540.6442,539.5242,542.744
Tide correction (milligals)
-0.040-.046-.051-.054-.059
-.064-.066-.070-.072-.074
-.074-.073-.070-.067-.063
-.060-.055-.049-.045-.040
-.037-.032-.020-.010-.001'
+ .010+ .016+ .024+ .030
Terrain correction (milligals)
+0.122+ .138+ .148
., +.154' +.158
+ .161+ .163+ .164+ .165+ .166
+ .167+ .167+ .167+ .167+ .166
+ .165+ .164+ .163+ .162+ .161
+ .161+ .160+ .164+ .167+ .163
+ .122+ .099+ .080+ .122
Corrected gravity
(milligals)
2,542.8062,544.8862,546.7682,548.4022,549.943
2,551.5012,552.2622,553.4822,554.7382,556.449
2,558.1662,559.2562,560.7882,562.3462,564.181
2,566.0902,568.1412,569.6402,571.4042,572.813
2,574.2752,576.0152,568.1202,559.2392,552.368
2,542.8782,540.7592,539.6282,542.896
Table A.~Well BUT-1, Butler Valley Logged January 25, 1980
Station
12345
6789
10
1112131415
1617181920
2122232425 '
2627282930
3132
Depth (feet)
213.9245.0290.0335.0384.0
426.0468.0532.0566.0604.0
651.0690.0740.0796.0847.0
914.0965.0
1,020.01,069.01,118.0
1,165.0914.0690.0651.0426.0
213.9172.0137.092.050.0
20.0213.9
Greenwich mean time
15:5216:0516:1716:2916:41
16:5217:0817:2017:3317:50
18:0118:1218:2018:3018:40
18:4918:5819:0719:1519:23
19:3119:4319:5820:0620:24
20:4120:5921:1321:2621:40
21:5222:05
Uncorrected gravity
(milligals)
2,867.0732,868.3762,870.2202,872.0442,874.003
2,875.6752,877.3062,879.5002,880.8072,882.237
2,883.8622,885.0472,886.8372,888.6862,890.308
2,892.4582,894.0672,895.7972,897.3582,899.010
2,900.7322,892.4592,885.0632,883.7842,875.700
2,867.0602,865.3102,863.9022,861.9252,860.308
2,858.9992,867.024
Tide correction (milligals)
-0.011-.014-.017-.020-.023
-.026-.030-.034-.037-.042
-.045-.048-.051-.053-.056
-.057-.059-.061-.063-.064
-.065-.066-.067-.067-.067-
-.066-.064-.061-.058-.055
-.051-.046
Terrain correction (milligals)
+0.231+ .251+ .279+ .307+ .338
+ .364+ '.389+ .427+ .447+ .469
+ .495+ .517+ .545+ .575+ .602
+ .637+ .664+ .692+ .716+ .740
+ .763+ .637+ .517+ .495+ .364
+ .231+ .204+ .182+ .155+ .132
+ .117+ .231
Corrected gravity
(milligals)
2,867.2932,868.6132,870.4822,872.3312,874.318
2,876.0132,877.6652,879.8932,881.2172,882.664
2,884.2122,885.5132,887.3312,889.2082,890.854
2,893.0382,894.6722,896.4282,898.0112,899.686
2,901.4302,893.0302,885.5132,884.2122,875.997
2,867.2252,865.4502,864.0232,862.0222,860.385
2,859.0652,867.209
Table 5.
Well VEK-5, Vekol Valley Logged January 28, 1980
Station
12345
6789
10
1112131415
1617181920
21222324
Depth (feet)
425.0475.0530.0590.0655.0
720.0760.0830.0900.1956.0
1,020.01,090.01,146.11,206.01,248.0
1,314.01,360.01,443.11,524.01,573.0
1,248.0956.0720.0425.0
Greenwich mean time
22:0022:1522:2722:3622:47
22:5523:0623:1723:2623:35
23:4723:5424:0324:1225:21
24:3324:4324:5125:0025:11
25:3826:0926:2826:56
Uncorrected gravity
(milligals)
2,749.3612,751.0422,752.8582,754.7912,756.916
2,759.0452,760.3412,762.6242,764.9132,766.748
2,768.8272,771.0782,772.8052,774.6552,776.105
2,778.3832,779.8922,782.4812,784.9142,786.532
2,776.1182,766.7072,758.9852,749.285
Tide correction (milligals)
-0.072-.075-.077-.079-.080
-.080-.080-.080-.079-.077
-.075-.073-.070-.067-.063
-.057-.052-.048-.042-.035
-.015+ .010+ .027+ .052
Terrain correction (milligals)
+0.162+ .174+ .189+ .204
"' +.221
+ .237+>. 248+ .265+ .283+ .297
+ .313+ .330+ .344+ .359+ .369
+ .385+ .395+ .415+ .434+ .445
+ .369+ .297+ .237+ .162
Corrected gravity
(milligals)
2,749.4512,751.1412,752.9702,754.9162,757.057
2,759.2022,760.5092,762.8092,765.1172,766.968
2,769.0652,771.3352,773.0792,774.9472,776.411
2,778.7112,780.2352,782.8482,785.3062,786.942
2,776.4722,767.0142,759.2222,749.499
Overnight January 29, 1980
252627282930
3132333435
425.0355.0300.0250.0195.0150.0
100.050.020.0
195.0425.0
16:0616:2216:3917:0417:1517:27
17:3617:4717:5918:1418:28
2,749.4362,747.1032,745.0852,743.2282,741.0862,739.231
2,737.2042,735.2012,734.1422,741.0732,749.391
-.029-.022-.015 .-.006-.002+ .001
+ .003+ .005+ .007+ .008+ .009
+ .162+ .144+ .130+ .117+ .104+ .094
+ .083+ .073+ .067+ .104+ .162
2,749.5692,747.2252,745.2002,743.3392,741.1882,739.326
2,737.2902,735.2792,734.2162,741.1852,749.562
Table 6. Well VEK-2, Vekol ValleyLogged January 30, 1980
Station
12345
6789
10
1112131415
1617181920
2122232425 '
2627282930
3132333435
3637
Depth (feet)
475.0520.0560.0625.0690.0
760.0850.0928,0
1,012.01,100.0
1,154.01,210.01,270.01,325.01,400.0
1,475.01,550.01,620.01,695.01,765.0
1,840.01,900.01,960.01,550.01,210.0
850.0475.0430.5365.0296.0
226.0160.0110.062.020.0
226.0475.0
Greenwich mean time
19:3819:5320:0020:1320:20
20:3120:3920:4920:5621:05
21:1421 : 2221:3121:4021:49
21:5822:0822:1722:2422:30
22:3922:4622:5423:1623:32
23:5124:0624:1824:2924:38
24:4624:5525:0525:1625:24
25:3625:53
Uncorrected gravity
(milligals)
2,690.0462,691.7382,693.2872,695.7662,698.196
2,700.7872,704.2272,707.1902,710.3432,713.729
2,715.8392,718.0292,720.2962,722.3822,725.346
2,728.2072,731.1242,733.8222,736.7102,739.368
2,742.3632,744.6982,747.0742,731.1732,718.082
2,704.3152,690.0912,688.3372,685.5772,682.556
2,679.3642,676.2472,673.8312,671.6272,669.578
2,679.3602,690.116
Tide correction (miliigals)
+0.015+ .011+ .010+ .006+ .004
-.001-.004-.008-.011-.015
-.020-.024-.028-.033-.038
-.042-.048-.052-.056-.059
-.063-.066-.069-.078-.083-
-.087-.089-.090-.090-.089
-.088-.087-.085-.081-.078
-.073-.064
Terrain correction (milligals)
+0.143+ .151+ .158+ .170+ .181
+ .193+'. 208+ .220+ .234+ .247
+ .256+ .264+ .273+ .281+ .293
+ .303+ .314+ .324+ .335+ .345
+ .356+ .364+ .372+ .314+ .264
+ .208+ .143+ .134+ .121+ .107
+ .092+ .077+ .065+ .052+ .041
+ .092+ .143
Corrected gravity
(milligals)
2,690.2042,691.9002,693.4552,695.9422,698.381
2,700.9792,704.4312,707.4022,710.5662,713.961
2,716.0752,718.2692,720.5412,722.6302,725.601
2,728.4682,731.3902,734.0942,736.9892,739.654
2,742.6562,744.9962,747.3772,731.4092,718.263
2,704.4362,690.1952,688.3812,685.6082,682.574
2,679.3682,676.2372,673.8112,671.5982,669.541
2,679.3792,690.195
10
In the study area, the free-air gradient of gravity is slightly
distorted by regional mass anomalies associated with horst (high density)
and graben (low density) structure. In each well surveyed, the theoreticalr
free-air gradient of 0.09406 mgals/ft was corrected for such structure by
modeling the gravity effect of a two-dimensional polygon representing the
estimated regional configuration of the graben in which the well was
located. The magnitude of this correction varied witfr- estimated graben
structure, location of the well within the graben, and well depth, but was\
generally small. The correction lowered the theoretical free-air gradient
by 0.00015 to 0.00079 mgals/ft, resulting in a lowering of calculated
densities (equation 1) of 0.006 to 0.031 g/cm.
DENSITIES OF BASIN-FILL DEPOSITS
Densities of the basin-fill deposits logged in this study, calculated
from borehole-gravity data, are listed in Table 7 and plotted in Figure 2.
3 Densities above the water table range from 1.73 to 2.26 g/cm , and
densities below the water table range from 2.01 to 2.46 g/cm . The
depth-density plots (fig. 2) show density layers, reflecting individual
depositional sequences. In general, densities of the basin fill increase
with depth from the surface to about 800 ft and then remain constant or
even decrease with additional depth, as shown by the plot of average
density versus depth (fig. 3) and the plots of individual wells (fig. 2).
11
.Table 7. Densities of
basin
fill
calculated fr
om borehole-gravity data.
Wel
l IP
-1W
ell
de
pth
, 1,
000
feet
Depth
to
w
ate
r,
316
fee
t
Depth
in
terv
al
(feet)
20-
505
0-
100
10
0-
150
150-
19
51
95
- 23
52
35
- 27
52
75
- 31
43
14
- 33
33
33
- 36
53
65
- 40
0400-
445
445-
489
489-
518
51
8-
560
56
0-
603
60
3-
650
65
0-
702
70
2-
760
76
0-
800
80
0-
850
85
0-
890
89
0-
930
93
0-
980
De
nsity
(gra
ms
pe
r cubic
ce
ntim
ete
r)
2.1
74
1.9
88
2.0
24
2.0
13
2.0
51
2.1
42
2.0
86
2.0
82
2.1
57
2.2
49
2.1
58
2.1
22
2.1
79
2.2
22
2.2
32
2.1
22
2.2
13
2.2
66
2.1
83
2.2
69
2.2
74
2.2
16
2.2
90
Wel
l W
KF
Wel
l d
ep
th,
1,3
02
fee
tD
epth
to
w
ate
r,
365
feet
Depth
in
terv
al
(feet)
20-
505
0-
7575-
100
100-
14
41
44
- 19
41
94
- 24
52
45
- 28
62
86
- 32
63
26
- 36
53
65
- 40
64
06
- 42
0420-
462
462-
505
505-
548
54
8-
610
61
0-
674
67
4-
746
74
6-
815
81
5-
860
86
0-
910
91
0-
970
97
0-1
,03
0-
1,0
30-1
,088
1,0
88-1
,145
1,1
45-1
,224
1,2
24-1
,285
Density
(gra
ms
pe
r cu
bic
centim
ete
r)
1.8
28
2.1
08
2.0
17
1.9
86
2.0
57
2.0
17
2.0
49
2.0
60
2.2
19
2.2
50
2.2
60
2.1
96
2.2
47
2.2
01
2.19
.12.1
95
2.3
18
2.3
18
2.3
23
2.3
27
2.3
19
2.2
91
2.3
08
2.2
92
2.3
04
2.3
01
Wel
l M
W-2
Wel
l d
ep
th,
un
kn
ow
nD
epth
to
w
ate
r,
364
feet
Wel
l obstr
ucte
dat
1,1
00 fe
et
De
pth
in
terv
al
(feet)
20
- 50
50
- 99
99
- 14
01
40
- 18
01
80
- 22
02
20
- 26
02
60
- 30
03
00
- 33
33
33
- 36
53
65
- 40
84
08
- 46
04
60
- 51
05
10
- 56
05
60
- 60
06
00
- 65
06
50
- 70
07
00
- 75
07
50
- 80
08
00
- 85
08
50
- 90
09
00
- 95
0950-1
,000
Density
(gra
ms
pe
r cu
bic
centim
ete
r)
1.8
58
1.9
44
2.0
04
1.9
19
2.0
29
2.0
35
2.0
20
2.0
39
1.9
43
2.1
63
2.1
95
2.1
68
2.2
11
2.1
60
2.2
27
2.2
45
2.2
80
2.2
63
2.3
00
2.3
31
2.3
37
2.3
46
We
ll V
EK
-2W
ell
de
pth
, 2
,04
5 fe
et
Depth
to
w
ate
r,
440
feet
De
pth
in
terv
al
(feet)
20
- 62
62
- 11
01
10
- 16
01
60
- 22
62
26
- 29
62
96
- 36
53
65
- 43
04
30
- 47
54
75
- 52
05
20
- 56
05
60
- 62
56
25
- 69
06
90
- 76
07
60
- 85
08
50
- 92
8928-1
,012
1,0
12-1
,100
1,1
00-1
,154
1,1
54
-1,2
10
1,2
10
-1,2
70
1,2
70
-1,3
25
1,3
25-1
,400
1,4
00-1
,475
1,4
75-1
,550
1,5
50
-1,6
20
1,6
20-1
,695
1,6
95-1
,765
1,7
65-1
,840
1,8
40
-1,9
00
1,9
00
-1,9
60
Density
(gra
ms
pe
r cu
bic
ce
ntim
ete
r)
1.7
34
1.8
46
1.7
52
1.7
94
1.8
58
1.9
30
1.9
94
2.0
55
2.1
75
.2.1
29
2.1
53
2.1
82
2.1
98
2.1
49
2.1
60
2.1
76
2.1
40
2.1
18
2.1
17
2.1
68
2.1
64 '
2.1
00
2.1
54
2.1
26
2.1
39
2.1
40
2.1
60
2.0
84
2.1
24
2.0
97
We
ll V
EK
-5W
ell
de
pth
, 1,9
95
feet
Depth
to
w
ate
r,
345
feet
Wel
l o
bstr
ucte
da
t 1,5
73
feet
De
pth
in
terv
al
(feet)
20
- 50
50
- 10
01
00
- 15
01
50
- 19
51
95
- 25
02
50
- 30
0300-
355
355-
425
425-
475
47
5-
530
53
0-
590
59
0-
655
65
5-
720
72
0-
760
76
0-
830
83
0-
900
90
0-
956
956-1
,020
1,0
20-1
,090
1,0
90
-1,1
46
1,1
46-1
,206
1,2
06
-1,2
48
1,2
48-1
,314
1,3
14-1
,360
1,3
60-1
,443
1,4
43
-1,5
24
1,5
24-1
,573
De
nsity
(gra
ms
pe
r cu
bic
ce
ntim
ete
r)
2.2
64
2.0
76
2.0
57
2.0
31
2.1
20
2.1
94
2.2
09
2.3
40
2.3
25
2.3
49
2.3
81
2.3
61
2.3
59
2.3
71
2.3
64
2.3
62
2.3
54
2.3
68
2.3
81
2.4
34
2.4
30
2.2
86
2.2
86
2.3
54
2.4
20
2.4
61
2.3
44
We
ll B
UT
-1W
ell
depth
, 1,5
20
feet
Depth
to
w
ate
r,
215
feet
Wel
l o
bstr
ucte
dat
1,1
67
fe
et
De
pth
in
terv
al
(feet)
20-
505
0-
9292-
137
13
7-
172
17
2-
214
21
4-
245
245-
290
290-
335
335-
384
384-
426
42
6-
468
46
8-
532
53
2-
566
56
6-
604
604-
651
651-
690
69
0-
' 74
07
40
- 79
6796-
847
847-
914
914-
965
96
5-1
,02
01,0
20-1
,069
1,0
69
-1,1
18
1,1
18-1
,165
De
nsity
(gra
ms
per
cubic
centim
ete
r)
1.9
44
2.1
41
1.9
26
2.0
71
2.0
08
2.0
05
2.0
41
2.0
58
2.0
79
2.0
87
2.1
27
2.3
04
2.1
42
2.1
76
2.3
77
2.3
61
2.2
43
2.3
55
2.4
03
2.3
91
2.4
12
2.4
17
2.4
02
2.3
28
2.2
14
VE
K-2
V
ekol
V
alle
yDE
NSIT
Y LA
YER
u
200
400
UJ
0 9J
600
CO o <
800
uJ
1000
\
K
1200
2T
1 4
nr"
14
0°
r a.
UJ
/"""
"\
1600
1800
2000
i 1
1 1
1 1
11
1|
'-
1',
WAT
ER
1 -
ICV
EI
1 ~
~
',' 1
-
\ 1 -
- ,»
DE
PT
H
1 IN
TE
RV
AL
1
"
r ii ~ i -
- - i1 - i i
i i
i i
i i
Mea
n density
Is
1.8
7
gram
s
cla
y
and
silt,
san
d,
and
gra
ve
l
Mea
n density
Is
2.1
4
gram
sper
cu
bic
ce
ntim
ete
r.
San
dyg
rave
l an
d so
me
silt
VE
K-5
V
ekol
V
alle
y
WAT
ER
LEV
EL
DEPT
INTERVALH
1 I
L
1 _ 1
DE
NS
ITY
LA
YE
R
ANO
D
ES
CR
IPTI
ON
Mea
n density
Is
2.1
4
gram
s p
er
cu
bic
centim
ete
r.
Cle
an
g
rave
lly
sand
Mea
n density
Is
2.3
7
gram
s p
er
cubic
centim
ete
r.
Cle
an
gra
velly
sand
Mea
n density
Is
2.3
6
gram
s p
er
cu
bic
centim
ete
r.
Sllty
sa
nd
, 1
,20
8
to
1,3
50
fe
et;
cem
en
ted
sa
nd
and
gra
vel,
I,.IS
O
to
l,b<
:b fe
et; silly
sa
nd
. 1,5
25
to
1.7
28
feet
BU
T-1
Butler
Va
lley
I 1
1 1
1 1
1
EHPT
M | i
INTERVAL
1 I.
DENS
ITY
LAYIR
ANO
DESCRIPIION
Mean density
is 2.02 grams
per
cubic
cent
imet
er.
Inte
r bedded (.lay
and
grav
elly
silty
sand
Mean density
Is 2.11 gram
per mbic centimeter.
In
sill
y sand
Mean density
Is 2.37 grams
per
cubic
cent
imet
er.
Leme
nted
gravelly,
sllt
y,
and
clay
ey JJ
nd
Mean
de
nsit
y It 2.27 grams
per
cub\c
cent
imet
er.
Grav
elly
sand
?
1.6
1.8
2.0
2.2
1.9
2.1
2.3
2.5
1.9
2.1
2.3
2.5
DENS
ITY,
IN GR
AMS
PER
CUBI
C CE
NTIM
ETER
Figure 2.--Densities of basin fill calculated from borehole-gravity da
ta.
IP-1
Tucs
on basin
DENSITY
LAYE
R
u
UJ <
200
u_ en in o
400
=c |
600
UJ
CO S
800
UJ
u_ 5 10
00rs
zc
f 2i
1200
Q
1400
1111,11
l| j_
1
| _
WAT
ER
|ItV
FL
|
j 1
_
1
DIP
TM! 1
*
INTE
RVAL
! _ 1
1 . 1
1 _
1 1
1 1
1 1
1 I
Mea
n densi
ty
Is
2.07
gr
ams
per
cubi
c ce
ntim
ete
r.
Sand
and
grav
el
and
som
e cl
ay
(Fo
rt l
ow
ell
For
mat
ion)
Mea
n densi
ty
Is
2.17
gr
ams
per
cubi
c ce
ntim
ete
r.
Sand
an
d qr
avel
an
d so
me
clay
(Tln
aja
be
ds)
Mea
n densi
ty
is
2.23
gra
ms
per
cubi
c ce
ntim
ete
r.
Cla
yan
d le
nses
of
sand
and
gr
avel
(T
inaja
be
ds)
?
__
_? ?
1.7
1
.9
2.1
2
.3
WKF
Avra Va
lley
DEPTH
INTE
RVAL :C
I
1 1
1
MW-2
Avra Va
lley
DE
NS
ITY
LA
YE
R
AMD
DE
SC
RIP
TIO
N
Mea
n densi
ty
Is
2.0?
gr
ams
per
cubi
c ce
ntim
ete
r,
inte
rbed
ded
sand
, gra
vel,
cla
y,
and
siH
Mea
n densi
ty
is
2.22
gr
ams
per
cubi
c ce
ntim
ete
r.
Mai
nly
sand
an
d gra
vel,
wea
kly
cem
ente
d
Mea
n densi
ty
is
2.31
gr
ams
per
cubi
c ce
ntim
ete
r.
Mai
nly
sand
an
d gra
vel,
mod
erat
ely
to
stro
ng
ly
cem
ente
d
_ _
_ O
__
O
»J
I i
f
TT
i '
WA
TIR
LE
VE
L
DEPT
H I 1
TERV
AL
1 1
OtNS
ITY
LAYER
AND
DESCRIPTION
Mean
density
Is
I .W gr
a*
per
cubic
centimeter.
Inte
rbed
ded
sand
, gravel,
clay,
and
silt
Mean
de
nsit
y Is
?.IB qr«r
per
rubic
cent
imet
er.
Intorbedded
sand
, grave! ,
clay,
and
SiH; we
akly
cemented.
Clay an
d si It
Incr
ease
wi
th increasing
dept
h
Mean
de
nsit
y is
2.29 gr
ams
per
cubic
cent
imet
er.
Inte
rbed
ded
sand
, gravel,
clay,
and
silt
; moderately
to St
rong
ly ce
ment
ed
_7 7 7
1.7
1.9
2.1
2.3
1.7
1.9
2.1
2.3
DENS
ITY,
IN
GRAMS
PER
CUBIC
CENTIMETER
Figu
re 2. Continued.
UJou_ o:ooQ
_»
3:0
UJCO
1 UJ UJu_
1 1
nrh-
UJ Q
U
100
200
300
400
500
600
700
800
900
1000
1100
1 9nn
J ___ 0 ' 6 I 1 1 1
6
7
_ * 7 ' _
~~ -10 ~
9
- "~^~^ -
-7
- -6
~
-6
Q 6
4
1 1 1 1 1 *\ 3 |
1.7 1.9 2.1 2.3
DENSITY, IN GRAMS PER CUBIC CENTIMETER
2.5
EXPLANATION
7 MEAN DENSITY Numeral, 7, is number of data points used to calculate the mean density. Half the length of the line is the standard error of the sample mean
Figure 3. Mean density of the upper 1,200 feet of basin-fill deposits,
15
Figure 4 compares basin-fill densities measured in this study with
depth-density curves given by other investigators. Curve A is from
borehole-gravity measurements reported by Healey (1970) for the upper 2,000
ft of basin fill in Hot Creek Valley, Nevada. Curve B, modified from Eaton
and others (1972), is based on conventional density-log data from central
Arizona. Curve C is based on well-sample data reported by Mattick and
others (1973) for Cenozoic deposits in the Colorado River delta. Curves A,
B, and C are within the range of densities measured in this study.\
Lateral and vertical changes in grain density, porosity, and water
saturation, which produce changes in the density of basin fill, are a
function of the local geologic history of an area and do not necessarily
correlate from basin to basin or even within a basin (i.e., Avra Valley,
fig. 2). Lacking knowledge of subsurface density in a given basin in the
region, however, curve D of Figure 4 could be used as a first approximation
of the depth-density relation.
16
UJo
O
LU UJ
I
LU Q
200
400
2§ 600 toQ
< 800
1000
1200
1400
1600
1800
2000 j_ _L
1.7 1.9 2.1 2.3
DENSITY, IN GRAMS PER CUBIC CENTIMETER
2.5
EXPLANATION
DENSITY AT MIDPOINT OF INTERVAL -
Well IP-1 o Well VEK-2
Well WKF * well VEK-5
Well MW-2 Well BUT-1
Figure 4. Comparison of the density of basin-fill deposits in parts of Arizona and Nevada. Data for curve A from Healey (1970). Curve B modified from Eaton and others (1972, fig. 11). Data for curve C from Mattick and others (1973, fig. 4). Data for curve D from Figure 3<of this study.
17
POROSITIES OF BASIN-FILL DEPOSITS
Porosity, <£> , was computed for intervals below the water table from the
borehole-gravity density, J , using the equation:
» ioo( - )/( - > (2)
where j5 is the estimated average grain density and J _ is the pore-fluid
density (g/cm ). Pores were assumed to be filled with water of density
3 3 1.00 g/cm ; grain densities of 2.50, 2.65, and 2.80 g/cm were used. The
porosity calculation is quite sensitive to grain density and error in this\
parameter is a major source of porosity uncertainty. A grain density of
3 2.65 g/cm probably best represents the basin fill. Grain densities ofo
2.50 and 2.80 g/cnr are thought to represent upper and lower limits.
Table 8 lists average porosities, calculated from the borehole-gravity
data, of the water-saturated density layers shown in Figure 2. Such data
can be used to estimate volumes of ground water in place.
In some instances, porosity also shows a positive correlation with
hydraulic conductivity and so is related to potential aquifer production.
In Avra Valley (well WKF) , for example, preliminary results of a
three-dimensional mathematical model of the ground-water system indicate
that the density layer between 326 and 67^ ft, with a mean porosity of
about 26 percent, is from two to four times more permeable than the
underlying density layer (67^-1,285 ft) with a mean porosity of about 21
percent (D. R. Pool, U.S. Geological Survey, oral commun., 1980).
18
Table 8. Porosities of basin-fill deposits calculated fromborehole-gravity data.
Well
IP-1
MW-2
WrCF
VEK-2
VEK-5
BUT-1
Depth interval Mean
ft
333-518 518-980
365-600 600-1,000
326-674 674-1,285
475-1,960
355-1,206 1,206-1,573
214-604 604-1,069 1,069-1,165
density g/cm
2.17 2.23
2.18 2.29
2.22 2.31
2.14
2.37 2.36
2.11 2.37 2.27
Average
Grain density
2.50 g/cm3
22 18
21 14
19 13
24
9 9
26 9
15
porosity, percent
Grain density
2.65 g/cm3
\
29 25
28 22
26 21
31
17 18
. 33 17 23
Grain density
3 2.80 g/cm
35 32
34 28
3227
37
24 24
38 24 29
19
Vekol Valley is divided into two parts by a buried ridge of
consolidated rock (Wilson, 1979, p. 8). The mean porosity of the saturated
basin fill is about 18 percent in the northern part (VEK-5) and about 31
percent in the southern part (VEK-2). Aquifer tests and results of a
preliminary model of the ground-water system indicate that basin-fill
deposits in the southern part are two to four times more permeable than
those in the northern part (R. P. Wilson, U.S. Geological Survey, oral
commun., 1980) .\
It must be strongly emphasized that there can be many exceptions to the
positive correlation between porosity and hydraulic conductivity.
Hydraulic conductivity depends on factors such as grain size and grain-size
distribution, pore-throat geometry, fracture density, etc. It is only when
such factors remain approximately constant that increasing porosity
correlates with increasing capacity of the rock to transmit fluid.
20
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vertical boreholes: Palo Alto, Stanford Univ., Ph.D. thesis, 217 p.r
Davidson, E. S., 1973* Geohydrology and water resources of the Tucson
basin, Arizona: U.S. Geological Survey Water-Supply Paper 1939-E, 81
P.
Eaton, G. P., Peterson, D. L. , and Schumann, H. H., 1972, Geophysical,
geohydrological, and geochemical reconnaissance of the Luke salt body,*
central Arizona: U.S. Geological Survey Professional Paper 753, 28 p.
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Goodell, R. R., and Fay, C. H., 1964, Borehole gravity meter and its
application: Geophysics, v. 29, no. 5, p. 774-782.
Healey, D. L., 1970, Calculated in situ bulk densities from subsurface
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Hearst, J. R., and McKague, H. L., 1976, Structure elucidation with
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Howell, L. G., Heintz, K. 0., and Barry, A., 1966, The development and use
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p. 764-772.
21
Jageler, A. H., 1976, Improved hydrocarbon reservoir evaluation through use
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Arizona, in New Mexico Geological Society 29th Field Conference, 1978,
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Schmoker, J. W., 1977a, Density variations in a quartz diorite determined
from borehole gravity measurements, San Benito County, California: The
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____ 1977b, A borehole gravity survey to determine density variations in
the Devonian shale sequence of Lincoln County, West Virginia: U.S.
Dept. of Energy, Morgantown Energy Res. Center MERC/CR-77/7, 15 p.
22
__ 1978, Accuracy of borehole gravity data: Geophysics, v. 43, no. 3,
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1979, Interpretation of borehole gravity surveys in a native-sulfur
deposit, Culberson County, Texas: Economic Geology, v. 74, p.
1462-1470.
Smith, N. J., 1950, The case for gravity data from boreholes: Geophysics,
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Wilson, E. D., Moore, R. T., and Cooper, J. R., 1969, Geologic map of\
Arizona: Arizona Bureau of Mines map, scale 1:500,000.
Wilson, R. P., 1979, Availability of ground water on Federal land near the
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Geological Survey Open-File Report 79-1165, 36 p.
23