I

0

.0

0

0C-,

mz-I

('1

.1 -

U

!'N A - � I � � I

, .'� '; �' ;: ;?- � r. " --i. .-

Open-File Report 82-1043 Open-File Report 82-1043

UNITED STATES DEPARTMENT OF THE INTERIOR

GEOLOGICAL SURVEY

Resistivity sounding investigation by the Schlumberger method

in the Yucca Mountain and Jackass Flats area,

Nevada Test Site, Nevada

by

R. M. Senterfitl, D. B. Hooverl, and M. Chornack2

This report is preliminary and has not beenedited or reviewed for conformity with U.S.Geological Survey standards.

1 U.S. Geological Survey, Denver, CO.

2Fenix and Scisson, Inc., Mercury, NV.

Contents

Page

Introductiono..&.* .* .* . ... * .* ........... ............ .... ......................................

Schlumberger Vertical Electrical Soundings.. .................... 1

Vertical Geoelectrical Sections..... ..... . . ................. 1

Conclusions....*..#.....*...... . .............. ..... o.....e......... * ............................ 3

References............................ .......... *0......... .......... ............................... 8

Appendix.*...................... .............................. ........ . ............................. 9

ii

Introduction

A Schlumberger resiativity survey was made in the west-central sector ofthe Nevada Test Site (fig. 1) as part of an extensive program to assess andidentify potential repositories for high-level nuclear waste. The survey areais located within the Topopah Spring 15-minute quadrangle, part of which isshown in plate 1. The intent of the survey was to determine the geoelectriccharacteristics of the area and to relate them to the thicknesses andhorizontal continuity of lithologic units in the Yucca Mountain and JackassFlats area, and to locate faulting within the survey area. A total of 29soundings is included in this report. The field data were interpreted interms of rock layer resistivity and thickness by computer methods (Zohdy,1973), and cross-sections were constructed to illustrate lateral resistivityvariations within the near-surface rock.

Schlumberger vertical electrical sounding

Vertical electrical soundings (VES) were made with a four electrodeconfiguration commonly referred to as the Schlumberger array (Keller andFrischknecht, 1966). The method uses four in-line electrodes; the inner pairfor recording electrical potential as a current is passed through the outerpair. Measurements are made in a series of readings involving successivelylarger current electrode separations. The data are plotted on a logarithmicscale (see Appendix) to produce a sounding curve representing apparentresistivity variations as a function of half current-electrode separation(AB/2). For Schlumberger soundings, the greater the current, or outerelectrode separation, the greater the depth of exploration. Sounding curvesnumbered YM-1 through IH-3, 24 through 27, 29 through 45, 47 through 50, and79-3 show the results of these measurements. All the soundings used'in thisreport are contained in the Appendix. The locations of the Schlumbergersoundings are shown on plate 1. Each sounding curve has been inverted by useof a computer program to give a'one-dimensional layered model (Zohdy, 1973).Interpretation of the sounding data assumes homogeneous, horizontal layering,therefore, where lateral heterogeneities in resistivity exist within theinfluence of the energizing current field, the sounding may exhibitdistortions which, when present, the computer will model as horizontallayering. Data distortion resulting from lateral variations in rockresistivity are not always recognizable from the shape of the field curve.

Vertical geoelectrical sections

Three geoelectric cross sections were prepared from the computer derivedone-dimensional layered models to illustrate resistivity variations within thesectors of the study area. The locations of the cross sections are shown onplate 1. The sections were compiled with a vertical exaggeration of 14.5 andcontoured with seven logarithmically scaled intervals per decade. Eachcross section includes at least one litholgoic log on-line with theSchlumberger soundings in that cross-section to provide comparison ofgeoelectric and lithologic data.'

Resistivity cross section A-A' is shown on figure 2. This cross sectionis constructed in a northwest-southeast direction across the northern part ofJackass Flats. Lithologic data from drillholes J-11 and J-13 are included.Resistivity values show a -general decrease with depth, beginning at about 250

1

meters, which indicates that more conductive rocks are being sensed atincreasing depths. Between VES 24 and 25, an abrupt change in depth to theconductive zone is shown. The Mine Mountain fault, mapped by Ekren andSargent (1965) as a left-lateral strike-slip fault, striking northeast anddown-dropped to the southeast, is mapped approximately 6 kilometers to thenortheast of VES 25 and 24 (Orkild, 1968) and is inferred to pass betweenthose two stations (D. L. Hoover, USGS, oral commun., 1981). From depths ofabout 150 meters and continuing downward through the section between VES 25and 27, the resistivity contours have an apparent dip to the northwest. AtVES 24, the apparent dip of the resistivity contours is more gradual to thesoutheast. .These changes in apparent dip of the resistivity contours from VES25 to the northwest and from VES 25 to the southeast support geologic evidenceplacing the Mine Mountain fault between VES 25 and 24 (Ekren and Sargent,1965). At VES 25, beginning at a depth of about 150 meters, the resistivitycontours show a gradient decreasing in value with depth, indicating thesensing of a more conductive zone. At VES 24, a similar gradient is seenbeginning at a depth of about 280 meters, which supports evidence that theMine Mountain fault is down-dropped to the southeast (Ekren and Sargent,1965).

The two areas of low resistivity seen on cross section A-A' at depthintervals of 50 to 150 meters are probably caused by an increase in amounts ofclay and other fine-grained material within alluvial fill (see lithologic datafor drillholes J-11 and J-13, cross section A-A'). The area of highresistivity seen at a depth interval of 100 to 160 meters beneath VES 26 maybe due to the presence of local basalts which occur throughout this area(McKay and Williams, 1964). The water table, at a depth of about 300 meters,does not appear to have been detected by the soundings in this area.

Cross section B-B' (fig. 3) runs from the top of Yucca Wash to FortymileWash. Lithologic information from drillhole J-13 is included. Geologicmapping of this area (Lipman and McKay, 1965; Christiansen and Lipman, 1965)indicates a thick section of volcanics dipping gently to the east. Thegeoelectrical data shows a general decrease in resistivity beginning at adepth of about 300 meters and continuing downward through the section, whichindicates the presence of a more conductive layer within the tuffs. Severalareas of high or low resistivity are seen along cross section B-B' from thesurface to a depth of about 200 meters, indicating significant lateralvariations in rock resistivity within this depth range. These lateral changesare attributed to differences in fracturing, faulting, and lithology of thetuffs throughout the area, and to varying amounts of clay and other fine-grained materials in the alluvium.

Cross section C-C' (fig. 4) runs from the northeast end of Drillhole Washto the north-south road along Fortymile Wash. Lithologic data from drillholeUe 25a-1 is included with the cross section. The deeper ranges sensed show adecrease in resistivity with depth, indicating the presence of more conductiverock in the lower part of the section. The variations in resistivity withinthe upper 100 meters of the section are associated with volcanic rocks,principally the Tiva formation mapped by Lipman and McKay as outcroppingthroughout the area. The area of high resistivity seen from VES 39 to VES 37,at a depth interval of 100 meters to about 450 meters, is probably areflection of the Topopah Spring member of the Paintbrush Tuff (Spengler andothers, 1979). In the vicinity of VES 37 and 36, sharp changes in resistivity

2

values are shown in the depth interval of 80 to about 350 meters. Thesechanges could be a reflection of vertical displacement caused by faultscrossing the line of the cross section.

Conclusions

The interpreted results of some of the 29 Schlumberger resistivitysoundings, as shown in the cross sections of figures 2, 3, and 4, indicatesome lateral discontinuities which appear to be caused by verticaldisplacement due to faulting. Because the lithologic section in this surveyarea is composed. primarily of ash-flow tuffs beneath alluvium (Lipman andMcKay, 1965), many of the lateral resistivity variations are probably causedby differences in amounts of clay and other fine-grained materials within thealluvium, variations of lithology within the volcanic rocks, and the effectsof fracturing within the rock types.

3

N 300 000 m

N 250 000.

N 200 000 .

t50 000. 200 '*O

Figure 1. Index map of the Nevada Test Site and vicinity showingthe location of the Topopah Spring quadrangle.

4

BEa-0*4-HV S

A'

0 '

ISO

U200 .

MA~

300

400:

0.

6

700

Figure 2.- Oeoelectric cross section A-A" (PI. 1) compiled

from interpreted resistivity sounding data.

Contours Increase in logarithmic progression from

a value of 14 ohm-eters to 1000 ohn-meters.

Vertical exaggeration I 14.5.

200

~SMo

contout values(In 8ro~ammersl

120

310210

14010012323127I:

Ceoilectric crouj section B-B'(Pf. I) coMpi1e

from Interpreted resiativitX aoui#llog data.

Contours Increase In logarithmic progression

from a value of 14 olm-meters to 1000 ohm-we~

Vertical exaggeration X 14.5.

141)"

-4-N BE -*.

(IE 2!

N M

$&-I

Alluvium

Tuft ,welded

C

I00.1 Fl Tuft fnon-welded'

Tuff ,wlded200

-4

V.

300

400

5 O

6 01

7 0

Faults shown on this cross sectionare mapped by Llpman and McKay, 1965.

scalee-*

I'm

1 schuree indicate

C52): low refi~tttvity.

(3m Ohm-pete)

low0720320310IN190140too

21

I u2tf'vitrophyra

---Vater Table

TO f

Tuft 1non-weldeA

Tort

Figure 4.- seoelectric cross eetton6-C1 IM(l.1) compiled from interpreted resistivity

sounding data. Contours increase In logarithmic progression from a value of14 ohm-meters to 1000 ohm-metere. Vertical exaggeration X 14.5.

TD 762 I

References

Anderson, W. L., 1971, Application of bicubic spline functions to twodimensional gridded data: NTIS (National Technical Information Service),PB-203 579, available only from NTIS, Springfield, Va., 22161.

Christiansen, R. L., and Lipman, P. W., -1965, Geologic map of the TopopahSpring NW quadrangle, Nye County, Nevada: U.S. Geological Survey GQ-444,1 p.

Classen, H. C., 1973, Water quality and physical characteristics of NevadaTest Site water-supply wells: U.S. Geological Survey NTS Report 474-158.

Ekren, E. B., and Sargent, K. A., 1965, Geologic map of the Skull MountainQuadrangle, Nye County, Nevada: U.S. Geological Survey GQ-389, 1 p.

Keller, G. V., and Frischknecht, F. C., 1966, Electrical methods ingeophysical prospecting: Pergamon Press, London, New York Toronto, 517 p.

Lipman, P. W., and McKay, E. J., 1965, Geologic map of the Topopah Spring SWQuadrangle, Nye County, Nevada: U.S. Geological Survey GQ-439, 1 p.

McKay, E. J., and Williams, W. P., 1964, Geologic map of the Jackass FlatsQuadrangle, Nye County, Nevada, U.S. Geological Survey GQ-368, 1 p.

Orkild, P. P., 1968, Geologic map of the Mine Mountain Quadrangle, Nye County,Nevada, U.S. Geological Survey GQ-746, 1 p. ,

Spengler, R. W., and Rosenbaum, J. G., 1980, Preliminary interpretatons ofgeologic results obtained from boreholes UE 25a-4, -5, -6 and -7, YuccaMountain, Nevada Test Site: U.S. Geological Survey Open-File Report 80-929, 33 p.

Spengler, R. W., Muller, D. C., Livermore, R. B., 1979, Preliminary report onthe geology and geophysics of drillhole UE 25a-1, Yucca Mountain, NevadaTest Site: U.S. Geological Survey Open-File Report 79-1244, 43 p.

Young, R. A., 1972, Water supply for the Nuclear Rocket Development Station atthe U.S. Atomic Energy Commission's Nevada Test Site, Nevada: U.S.Geological Survey Water-Supply Paper 1938 19 p.

Zohdy, A. A. R., 1973, A computer program for the-automatic interpretation ofSchlumberger sounding curves over horizontally layered media: NTIS(National Technical Information Service), PB-232 703/AS, 25 p., availablefrom NTIS, Springfield, Va., 22161.

8

Appendix

Vertical electrical soundings YM-1 through YM-3, 24 through 27, 29through 45, 47 through 50, and 79-3. On each curve the measured field dataare represented by the symbol X, connected by straight line segments; thecircles portray a shifted field curve obtained by vertical adjustment ofindividual segments relative to the last segment on the right-hand side of thesounding curve (Zohdy, 1973); the resistivity model is represented by thecolumnar graph wherein the. width of a particular column designates thethickness of an individual layer and its vertical position corresponds to theresistivity of that layer.

- 9

____ jili ~~~~~~~~~~IJ ii l

T.l '~1

X~~~~~~~~~~~~~I I'~hI~l~r~~

. ~~~~~ f~~i1'Ii: - illi 'I; ii Ii ~~~~~~~~~~~~~~~~ IIL

3 ~ ~ ~~~~~~~~~~~~~~~~~~~~: 111WlIW1iIIllhhBiii.[J111IIW~IjhJiIIJ~' ;III-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~I

10 100WOAB/2. DEPTH IN METERS

)j

I-o

-;

- 0

-

'J-

*F ,

- . L

II-

0

no0u

Note: On this vertical electrical sounding, data for the

shifted field curve (represented by circles on other

soundings in this report) is not available.

gN3J2 L llSllllU~IUIllI1I[JPI U IIU 'U WkllUIWllIDN a gjg0I-

101 I 100

AB/2. DEPTH IN METERS.1000

C I I a1 I I fl tE I S F 3 5U55 I a U I U U I v U

1 10 100 -100oAR/9 DFPTH IN METERS

P T M M,T TU

111 ofli WV:1:wI

1W kiif

Ih

7 7

IWCO

CD

LL

IUHIUH 0 100010

rs #es r-ti--r,)-rt.J WI KAI=T[=Pq

- III !i~~~~~~~. .I~~~~I~~ti~~~iI~~tI!p I T. !l I q

- I *I ~~~~~~~~~~~~~ 1111 if*~~~~~~~~~~~~~~~~~~~~~~~~~~~~i II I,, IV.i'.II

I ~ ~I I I Iii' I ItilJI i

AB/2, DEPTH IN METERS

I-

I.

J

Ict

.0IJ

-"

O'.

0:

li-cr c

* a

;

I1 .,

* I.:

.i:!L4

3-..

'I.

I.

-1'

I..l. .1..

I,. 1.3,Iiei ...

i'I.

,.4I.

I.j.

,,j!

i;IP'...

jii jII

I.I .1. .

:t. .. i.., i j',.I3..

.1I

li i1 !I:-I:I .

i...... j

.;.

13 .I 'i

,....

11.1

I IIII,'

1'i

II

* I.3 I

I...

.21.�I �

:' I

I g�1

�ill-'K-f

[I. Iiii LiI I�

It!

.1 �

j�I

I.,

I II *'

.It

.II'

ViI

, .

0I,,..

iiIIi ll

.11

II

Ill~ir''II1

3-,If Y-' L I I L, WUIJWIJj L 4w ,UU, Uu4m I'z' -''a

80B/2, DEPTH IN METERS

jit'I

1 'Am

F.

LLJ .?; -p I:4 L:

wY:,I i9"

L1j fill :I .1"2

V I! P.

i ;I I 7 .,.i A 4

T .!iM i

T!C T !I.: I Ip

w j-,l .1rv;

;0T WI

41TV: T

U) J%Ill Jill

;i .,i Fuji

W T14

!JJ

Alvin

I LiO

AB/2, DEPTH N N1 Efi E R S

W II ~~~ IlLT 'I IloIi I u'

111 11 ;. aII i I lA i I.:6

W~~~~~~~~~~~~~~~~~~~i ~ ~ ~ ~ ~ ~ ~ ~ .

* ' I i' .1!.~~~~~~~ :i.'11jXwI , u L

'I *~~~~* .1~ V* *. **IIIII.1~~S '~ii' T F'.... .. , To

.4 1 11~~~~~~~~W 1i .

AB/2. DEPTH IN METERS

I II

Is jj-g |.t~l 4& ." l.;...iltlui~ I 'm. a ' . i- F i I 'Ill , . X- -- A -I-- I" W- I r1 10 100 -1O00

AnP) ngFPTH IN APTFRAS

III

I)~~~~~~~~~~~~~~~~~~~~~N

3::~~pi~~~~~~~~~~~~~~~~~~~~~~~y~~~~~~~~~I

10AB2vDET.I

1 10 I100 -1000Atin , E r%EflF- lid MI kr-rfzlQ

fi ll I' X .V

A:it: i t

10f,I,;: Pr a,!VA. J!

anT

Pi;a

(no Ni'l TITIAt �1:1 -ti t

ilu7 7 .1 N . Iitit O r-IT

all!:10 1,ql

it;10 100 -1000

AB/2, DEPTH IN METERS

I

I. if:I

.1;IF..

1)

iiiiX

--;

I .

0z

LUiF

CO

(D3W-wc

.i-'

:.I'

1'.1.' 1.:p ..

2

i,

I .*

!. 1

. Iv.:

I

I

i

:.11

* II

0

J

..

: ':I

.iI!

: II ~ I*.1-

II!!!ii

I.'

*1,.

iii'

I'll

�ij�* I

It

III

g I,

"IAili1 I ti

'..*.

I

I'.;;ii...

1'..

:, ;'i'1i.'11i '''i

i il

, I.

.'1

Ij.. .1 .

I

. I

, .

. -

;I ! I

I X. lj

'' I

.i'! I, . I

I I!;I.,

i

I

I.

:. l

.i1

i:!il

' '.tl

'._. .

1s

§ *i&1;:!1:.:'4

a

I.:

iiiI 1. . I

,iI,.

i.j

Iii!. .;..

I ii,

:1.1i' J

; i I.

: ii].I

!.i;, II 1. I :,i

.11I i 1

o if*1r- I A l

1 10

AB/2,

a I 4 5 J a 1 a a 41 1 4 1J,6 4I1

100 .1000

DEPTH ,N METERS

__ i11~~~~ I. I -pl'

-. I , ' I' I I ' Iil. 1

I~~~~~r: r :r Ii' MIT1~ T

An ri in nfDTI4 MI RAPTPPR

t 1!~~~~~~~~~~ !rII

I-t ~~~~~~~~~~~ I ~~~~~~~~~ 4 I II,. 1.. hit~~~~~~~~~~~~~~~~~~~~~~~~~~~..T

w~~~~~~~1 0 10

ddoz 0~B2,DET i ETR

III i! ~t

wi~~~~~~~~~~~~~~~~~~~~~~~~~~~~~i

.11 iiII~'i'i I I1141 l'

10 ~~~~~100 JO0oA Pl9 nlFPT11 IN METERS

Ii" '~~~~~~~~~~I

20 ji~~R2.DPHINMTRI I

h

:20 ~~ ~~~Iiif I I ii i ilHI III H iI

'1 :~~~~~~~~..~~~~~;ti1 tilt~~~ ...... .

liii ~ ~ ~ ~ ~~~~~ h I~~~[~~~I:J 1,

CO~~~~~~010 10

P~~AI)fFT NMTR

bill'

2 %O :AI 4:r 0

s.

IN id,

loll Ti

.41.II.T,idoLLI val

lit,

f

111111 J11

I 10 100 -1000

AB/2, DEPTH IN METERS

LU'H i r . J 1!

Ii t'i~~~~: iii I ~~~ hLI

w'- :111

10 100 -1000Anflh) ngltTU IKI RAPTPI~

I is

I

i I i

w

I-

1 1010I10

AB/2 DEPT INIETER

. .. I . .. I I . .. . . . . " , , 1, . .,- . : I --t, ,

. 1 -.4.: m .. . .� .I . - � ...... :..: ..-,,. . : , .I : .- .. ... -:. .: ... : . ...: , . . I % -, I

I I

i I71)DCH-iLU

I .

00

z(I)w

wo

0I-

T

ArI AI51I.10001 10 100

AB/2. DEPTH IN METERS

T-ii

1J

I,

20:co

z

(C)w

F-

()88

0

US-

cc

10 100 .1001

An InI ng=DTI-I INM FTFRS;

#I

Lu1

LuI

I .

.0z

Icoc

0

I-

iri

I ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ I~~~~. pJili ~~~~II II~~~~~:I~~~~~~~~~~~!~ ~ ~

44 ;~4'

. I :V

I

i

I

10 1001 10 ~~~~~~~~.- . .- V- O - e S a A I B%0 a r-r gi E" r%

.1000

i

I

C)

a:s

wI-W:.

0z.c)

W

CO)Co 0

0i'WV,

4

1

it~ i

IT.~~~~~~.

A I .j;44 i

J ..

I,;,

irt.

I I;

.1 1

I:,

IIl

III.

2.

* . I,.1.0.'':.

.0

I ':�; ;

111011 IIill � �

.i..

II liii*�4* ..0 *�3

311: I0? 1,144.; *J 91

.0.

�

�

10 j*II .11 3*10 I

11

I � ll�

0I*i.*aI 0*

0;.; �01:1 � I

I ja;� �

III 00

*.*. 31* jI

E.g 0I. Ill I.2 .:'. U..

* It.-.

*t..' ij 0g

* I!'' '1* .1"I �i

!rhI j�'�' ;r*

� '� ijf

I !

II'.

.I 1!It~llHit

V.

juil

[ii

: ' v Ii

~~' ~~I Fi

A1 :* I !j ' JJ I:..j, 4

,IH.

i

3*j1

iI

J.-

i11 i F

II'

I..I*1

.1.0I0�

UII

II lI�

a

i:

4..

: I

I . .

m r .

: 7:.. ii,

ii

l ! l l l l l ! l l. 1g .. . .. .-1 I1111111111111111111111 ..I.."~l~iilitW .. 1. l.ll.ll.ll.

IFI

a

. _- . . 1111 I_ 1 -1 11 tt41 I t -II i

w Iij : Ihj I ~~~~~~~I I

.1i! * I

I lI * II ILb II

hi i4I-- ........... n_._-b__'._nr .' i i- I i..%1..1''

1 lIj . IIA i1IfI,,II Il

~ ~~~ll r'~~~~~~~~~~~~~~ imn lI ji': .II I

10, I

�i 'hi �i*

I jiloll 12

��

i:: ;IllI

.ll

:I14-f4H-4-+4 Ill01 W 11N llllIFFIi0~lllf E|ffll W|1X 11 14Z

:1 m~~~~~~~~~gE |~~~~~~

O S J I S S I 5SI a a I I I I I

100 .1000

I I S I

1

AR/I. DEPTH IN METERS

-

sTI,V

IN EJ

IIq.

Ip. j'9 1 It

10:

fill V; 11

COw

pejTf

WV, a�c

r, 10 100 -1000

A13/2. -DEPTH IN METERS

(I I

3:t iii!.: ii* $Lr~~1'A 4i' r ~H**[

1 I ,~~jp nd

0

3. Vi I0 100I 1000hA1U9 flPPTI-I IIJMFTFRS~~i

I

V X VA V,

:::Iui 1: N

IT 4.,

.... .... .. V;iT IN

MO

j i 21 ;;I

T7: '71"

T-1d.-Sh

I

CO

JillUJI

lac

p wq

Is Hu

10 100 1000

AB/2, DEPTH IN METERS

l

I II I

;

w 0 |0 0-0: 0- f; ~~~~~~~~~~~~~~~~~;T1j | ;A; Ii ;

F~~~~~~~~~~~~~ V.,xi2 i|1 hftd iedcuve(tpesntd ycicls noter| 1111f1 ll M1111119491||ffi |||| sundings in tis report) i not availabe. i 11|1n! 1[1 1111 1111111111090

w i ll m I J | ._ .li*illlti ,1@llwiull, p

1 0 0 -oLU ~ ~ ~ ~ A/ J FT NMF.

- - - t f-: - . - I -

't