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COMMONWEALTH OF AUSTRALIA
3
DEPARTMENT OF NATIONAL DEVELOPMENT
BUREAU OF MINERAL RESOURCES, GEOLOGY AND GEOPHYSICS n - ,'I
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~ I
RECORD No. 1964/120
I"
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LAWRENCE VALE AND HOSPITAL AREAS BOREHOLE LOGGING. LAUNCESTON, TASMANIA
J• ..
1959·60
,"'10,
'
J '~!,
.
by
W;A. WIEBENGA
The information contained in this report has been obtained by the Department of National Development as part of the policy of the Commonwealth Government to assist in the exploration and development of mineral resources. It may not be published in any form or lIsed in a company prospectus or statement without the permission in writing of the Director, Bureau of Mineral Resources, Geology and Geophysics.
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RECORD No. 19641120
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LAWRENCE VALE AND HOSPITAL AREAS BOREHOLE LOGGING. LAUNCESTON, TASMANIA 1959-60
by
W.A. WIEBENGA
The information contained in this report has been obtained by the Department of National Development as part of the policy of the Commonwealth Government to assist in the exploration and development of mineral resources. It may not be published in any form or used in a company prospectus or statement without the permission in writing of the Director, Bureau of Mineral Resources, Geology and Geophysics.
CQIlTl!hI\TTS
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Page ...
SUMMARY
1•
INTRODUCTION
1
2.
METHODS
1
3.
GEOLOGY AND INTERPRE.;rATION
3
4.
LAHRENCE VALE A.BBA
4
5.
HOSPITAL AREA
8
6.
CONCLUSIONS
8
1·
REFERENCES
9
.,
""
ILJ~USTRATIONS
(Drawing No.K55/B5-54)
Plate 1 •
Location plan
Piata 2.
Location -pJ.an, Lawrence Vale area
Plate 3.
Correlation of boreholes 110. 12, 17
Plate 4·
Correlation of boreholes No. 1, 9, 3, 4A, 13, 10
(;'
6, 5, 16)
Pl?~;t:!
5.
Cr.:,ss-secti.ons, Lawrence Vale area
PICl.te
6.
Landslip area, Lavrrence Vale
1964/120
(K55/B5-66) (K55/:a5-67) (K55/B5-68) (K55/B5-¢9 ) 4 B (I{55/ 5-50)
•
SUMMARY
CSIRO Soil Mechanics Section carried out singlepoint resistance and radioactive logging on shallow boreholes as part of an investigation of landslip in the Lawrence Vale and Hospital areas, I'aunceston, Tasmania from December 1959 to May 1960, using equipment supplied by the Bureau of Mineral Resources, Geology and Geophysics. Clay, silt, sand, and carbonaceous sediments can be distinguished from the electrical resistance logs. The variations in salt content of the sediments could be j';.dged from the radioactive logs because the s:lH::: contain 8..'1. appreciable amount of potassium with its radioactive isotope, KLj.O. This makes it possible to distinguish leached-out clay and silt zones, and it is shown that these may probably be interpreted as potential slip zones.
'-'
In the Lawrence Vale area the beds dip about 1o-} degrees west, intersect the western slope of the hill, and can easily form slip planes. The lowest boundary of possible slip is indicated. The relation between bedding pla."les and topography also explains why the eastern slope of the hill
forms a stable zone.
1:'::', the Ho::,pi tal area the beds dip about 17 degrees contrary to the uncJ,e:r.lying dol0rit~ surface wh~.ch slopes upwru:d towards n01'th. Th:;.s le,rgely explains why the Hospital area. 2.p:p8a:CS to form a stable zo:,~.e. north~
1•
INTRODUC'l'ION
In recent years the LavJ'rence Vale hill in Launceston, Tasmania has been developed as a suburban residential area. According to local reports, evidence for landslip was noted more than 10 years ago. During the past few years landslips resulting in the destruction of houses and roads have reached such proportions that the Launceston City Council decided to ask the Soil Mechanics Section of the Commonwealth Scientific and Industrial Research Organisation (CSIRO), headed by Dr Aitchison, to make 3Jl investigat- _" ion. CSIRO drilled shallow boreholes in a restricted area but about one mile long and half-a-mile wide. The Lawrence Vale road is located on the steep western side of the hill, roughly in the centre of the area. Further, the Health Department of Tasmania proposed to build a new hospital adjoining the existing Queen Victoria Hospital on a site, referred to as the Hospital area, nearly one mile north of Lawrence Vale. Amongst other questions related to foundation problems, it was desired to investigate the local dip and strike of the surface sediments (Polak, 1962). To assist CSIRO in its investigation, the Bureau of Mineral Resources, Geology and Geophysi~s supplied a singlepoint resistance logger (500-ft Widco shot-hole logger), fitted with radioactive logging equipment. The logging was done between December 1959 and May 1960 by I1lIr P. Kerr of the City of Launces'~on Engineer's drawing office. The logs were interpreted by the Bureau. Concurrently with the drilling and logging investigation the Bureau did some geophysical survey work, mainly consisting of resistivity depth-probes (Polak, 1964). With the logs it is possible to distinguish clay from sand or silt layers, and to obtain information about the physical nature of the sediments. The logs make it possible to correlate between ooreholes end so deduce the strike and dip of the beds. Since only on.e geological core log (Bore 12) was received, the interpretation is largely based on the resistance and radioactive logs &~d gives some very interesting and useful results. Although it is expected that a marked improvement in the interpretation would rGsult from comparison with more geological core logs, the result~ show the value of logging as a tool ;~onsidE:..rable expem;e and time may be saved in certain cases by using geopl~sical logging instead of taking a core.
2.
METHODS
.Single-point resist?XlcE. logging. Single··:?oint resistance logging consi8ts of recording Y!:1,:ciations in the resistance betvleen the logging electrode, which :~;~ 'caised or lowered in the hole, and the ground electrode, which :i.n situated at the surface. Practically the whole of the resistance .~"',. tht~ circuit is in the immediate neighbourhood of the electrodes. ;,E' ·r.he ground electrode is stationary, the resistance in its neighbourhood may be assumed to be constant during the measurements, anQ the changes of resistance recorded are therefore due to -;;axiations in the resistivity of the materials around the moving electrode.
2.
The magr.,i tude and width of the resistance variation is controlled by the beds opposite the logging electrode, the thickness of the bed, the borehole diameter, and the resistivity of the IlILl.d. However, these factors are not linearly related to the recorded variations in resistance. Variations in the higher ranges of resistivity have a smaller effect than simjlar variations in the lower ranges. The effect is to compress the resistance log for the higher ranges, and make it impossible to estimate the true resistivity from the residtance log. The resistivity of a porous rock is inversely proportional to the porosity and the salinity of the pore solutions. Assuming that the salinity of the pora solutions remains about the same over large sections of rock, variations in the resistance log will indicate variations in porosity, and these can, with certain limi+''ttions, be translated into geological terms. For instance, clay and shale, with their high porosity, are indicated by low resistance; unsorted material of low porosity, as for instance gravel, unsorted s~~d, and unsorted fine sana and silt are indicated by a relatively high resistance. Radioactive logging Radioactive logs show variations of natural radioactivity emitted by the formations penetrated by the dxill. The following is a list of sedimentary rocks in decreasing order of radioactive intensity: organic clay and shale clay and shale shaly fine sand. and
sn t
shaly sandstone shaly
limf~stone
sandstone limestone dclomite salt coal Since day and shale are generally more radioactive than sand (incll H :,...i.ng fine !'land and silt), the radioactive log variations often corre;3T.j:.md to Ii tllo1ogi:Jal c~langes in a manner contrary to the variations in t~e resistance log. The response of the radioactive p:rube is also affected by absoJ.:-ption, and varies with tr..e uiamdter of the hele, thp. density of the drilling fluid, the caSing thickness, and the degree of saturation of the ground. These condi tions have to ·be t2.ken into account for interpretCl.tion; and 00rrections have tc. 1..Je applied for quantitative interpretation.
3.
Geolog.y It was reported by the Curator of Fossils, National Museum of Victoria (Gill, pers. comm.), who examined the drill cores, that the top of the Lawrence Vale hill is capped by 30 to 40 ft of weathered greywacke sandstone, overlying a. !'ormation of clay, silt, and fine sand. The latter formation consists of alternate layers of carbonaceous and non-carbonaceous sediments. At the base of the sediments is dolerite. Faults ~~d slip ~ones are COIIlIllon. A brief statement of the geology is given by Gill (1962) • The groundwater is partly saliile (salinity up to 6000 p.p.m.) and contains, apart from magnesium and sodium,
up to 20 p.p.m. of potassium and traces of nickel. ~he potassium -40 isotope is radioactive. As clay is a good absorber of ~otassium ions (and other metal ions), it seems likely, or at least possible, that the radioactivity of the Lawrence Vale clay is caused by potassium which is also present in the groundwater. The traces of nickel in the groundwater suggest that part of the water may comp. from or through dolerite, or weathered products of dolerite~. the greywackes. The saline and fresh groundwaters are irregularly distributed through the whole vertical section. This pattern of intermingled fresh and saline waters suggests that: (a)
Either the original sediments were deposited in a saline or bracl~ish water environment, or the salinity of the groundwatera increased by progressive weathering.
(b)
Saline waters ascending from the dolerite are superimposed on thE; original groundwA.ter (indicated by the pre3ence of 'nickel' trac8s).
(c)
i?r~sh rain-water soaking ~.nto the hill
intermingles with saline water, and probably leac:les out the sediments, including the salt (;')ntai'1.dd. in clay and silt, by a process of ion-'ex'JJ'ange.
..
Baver (1940) shov:ed that the hydration characteri.stics (and also the viscosity) of clay are dependent on the metal ions, including pv'i:;assium, c.ommonly found in salt water. Bjerrum (1954) has conclusively- proved that the shear strength 0f saline clay is considerably lmlered by leaching; he uses his data and exper~ments for the E-::r.pla.'1ation of landslips in Norway.
4. The aGove 8hc.y .{3 thaJ(j the salt content of the clay may give an indication of tt8 probable occurrence of landslips, whatever the original source of the salt in the clay may be. It seems posl?ible that leach~d-out cl~v zones at Lawrence Vale hill could be identified as major (potential) slip zones. At least, this possibility could be used as a working hypothesis. On the ).ogs, clay shows a low resistance because of its high porosity, and a relatively high radioactivity because of its capacity to absorb potassium. However, if during long time intervals the clay is leachGd out by fresh rain-water, the radioacti vi ty could be appreciably lowered. Although the resisti vi ty of the clay would increase with leaching, it would remain lower than that of unsorted sands because of the high porosity of clay. Hence, leached-out dlay zones, possibly corresponding to slip zones or potential slip zones, are indicated on the logs by low resistances and low radioactivity. Carbonaceous clay and silt usually show a much higher 'radioactivity than corresponding non-carbonaceous clay. Sand, and to a lesser degTee silt, becanse they usually consist of less-sorted material and contain less potassium; show a higher resistance and a low radioactivity. Dense rocks of low porosi ty (~.g. coal or crystallised limestone) usually are recognised. by resist3.!lce peaks.
•
4.
f.AWRENCE VALE ARF.A
Ple.te 2 show:J the layout of the bores, Plates 3 and 4 an interpretation of the logs a8 cross-sections throug:,. bores,
Plate 5 tte relation of bedding planes to topography, ~~d Plate 6 the rp.sults and their relation to the slip areas in the form of a plan. The vertical depth scales of the logs are S!10wn as a1 ti tudes ab~ to a common datum, :yi~. mean sea level. These altj.tndes are used in the following discussion. The sed..i.me!1.ts consi3t of th.inly inte:rbeddod layers of clay, s~.l t, and. f,a.~r5.. O~1 the cross-sections the predominant rock types as i.rde~·preted from the logs are indica.ted.
The main d.iscontinuity is at about 209 ft. The resistance loe; indicates sand. and silt above this lelTal and cl:;W below th~. 5 level.
5. The radioactive log is irregular below 209 ft and this may be caused by carbonaceous sand and silt. A highresistance feature between 236 and 252 ft, partly overlapping a radi.oacti ve feature, suggests the presence of carbonaceous sand or silt. Between 252 and 279 ft the radioactivity is low, as is normal for sand and silt; but in the clay close to the surface the radioactivity is high •
•
The clay formation below 209 ft shows a jagged resistance curve, indicative either of alternating layers of carbone.ceous and non .. carbonaceous materiel, or of alternating thin layers of clay ~~d silt. From 209 to 119 ft the low radioacti vi ty inclicates a leached-out clay, possibly a major slip zone; below 179 ft the radioactivity is greater. YVl-J.en the drill pipe was pul1 ed out, clay was extruded into the hole just below 179 ft, preventing the logging probe from passing unhindered. This conclusively proved that the clay was plastic. Bore 6 The resistance log of Bore 6 shows essentially the same features as the one of Bore 5; below 234 ft there is only clay, but above 234 ft there are sand, silt, and clay. The zone of low resistivity between 252 and 268 ft in Bore 5 has been correlated with a zone in Bore 6 between 282 and 296 ft. The clay of low resistivity lying above the 277-ft level in Bore 5 is correlated with thet above 305 ft in Bore
6. The rRdioactive log of Bore 6 does not show the same !lS ths log of Bore 5, ~:cobably te<;ause of leac!l:'ng by fresh rain-v/d.ter. le.rge r?dioacti ve featu:::-es
The top clay formc~tion above 305 ft shows a large radioactive feature. B'stween 305 and 236 ft the radioactive features probably correspond to silt and clay layeI'3 which may be carbonaceous. Below 236 ft t:f1.9 lower radioactivHy suggects a lE.::.c}'led clay zone, wru.ch may represent a slip zone. Excent for the clay near the Surface, the sediments :;~em +'0 have been leached out far more than at B01_'e 5. '.;:~1is suggests i;hat potential sli:;,; zones are more l:l~:e:.y to be found near Bore 6 than near Bore 5. at .Bo::.e 6
The resistance log of Bore 1 is recorded cj.ose to the side of the rpcording paper, and so shows the features at a compressed scale. Although the correlation of resistance features with Bore 6 is difficult, an approximate correlatiGn was made -oy using radioactive featv.-res. 'rhe correlation is shown in Plate 3.
6. Resistance pe:l.l{s at 305 and. 313 ft are accompanied by radioactive anomalies which suggest that they are due to carbonaceous silt or clayey sand. From about 309 ft to the surfac3 the logs suggest the presence of radioactive clay.
•
Compar'ed with Bore 9 the resistance log indicates veJ.:y l i ttl e carbonaceous material. The radioactive anomalies are well-defined, and 31lggest practically no leaching except from the bottom (169 ft) to 186 ft, and possibly between 271 and 284 ft. Field evidence shows that Bore 7 is located in a reJatively stable area.
Although the correlation betwAen Bores 9 anQ 7 is hardly possible the correlation between Bores 9 and 6 is easie.c~ resistance features above 218 ft in Bore 6 resemble resistanc'9 features above 232 ft in Bore 9. 'l'he resistance curve of the portions of the bore between 225 and 273 ft, and between 125 and 177 fi: f:lhows a very jagged form, probably caused by alternating layers of carbonaceous and non-carboliaceous material.
•
The radioadi ve log is featureless in the p.pper part of the bore; the first small features appear below 210 ft. As explained in Section 3 this indicates that the top portion is completely leached out, and the lOVIer portion is partl~" leached out. The core is therefore probably located in a bad slip zone. Field evidence shows that Bore 9 is in or close to the worot landslip zone in the area. It i'3 not known whether carbonaceous la.~'ers promote landslip, bi.lt the presence of many thin layers of carbonaceous material in the worst part of the area rather suggests '~hL~ possibility.
l~dslip
From 240 fL dovm 10120 r-t the resistance log shows a gradual increase, v!hich il1dica-G es an inc:.cease in Ail ty or sHndy materia}.. Be}.c,"" 60 ft the resistance drops again, :p:::-.)c<>..cl.y becau.se of !;l.Vl increase in clay.
..
The near-surface clay is highly radioactive, but J:'8.dicactivHy decreases below tha 200-ft lev~l; a sudden cl:':'op at 15? ft sugc;asts the preSarIce cf a leac~ed-out zene. B(~t"v eE::n 116 B.nd 144 n the radio1::l.cti ve log is not satisfacto:t:ily rGc()rl1.ed. Below 116 ft the re,dioc,ctivity is higher again and 1ihen inCrFJo.s6s fux-ther in the lower clay formation below 32 ft. In some places local increases in radioactivity co~relate with local increases in resistrulce, ~. at 168, This suggests the presence of 156, 52, 24, and 8 ft. carbunaceous silts at these levels.
7:'he resistar.ce cur.ve of Bore 3 shows a rena:.ck<:J.ble resemblance to that of BJre 4A.
7. Por instance, the resistance increases gradually from 229 to 149 ft, indicating an increase in silty or sandy material. Small resistance features at 207, 187, 147, and 108 ft can be correlated with features of the log of Bore 4A at 180, 158, 119, and 80 ft indicating that the sediments at Bore 3 are about 28 ft higher in level than at Bore 4A. It is noteworthy that the surface elevation at Bore 3 is also about the same amount (29 ft) higher than at Bo~e 4A, suggesting that the sediments in this area are approximately parallel to the land surface.
•
A comparison between the radioactive logs at Bore 3 and Bore 4 A shows one remarkable difference, yiz.• between 234 and 187 ft the radioactivity in Bore 3 is verJ Luch lower than on the corresponding place in Bore 4A, suggesting a larg~ leached-out slip zone in Bore 3. The pattern of logs of Bores 3 and 4A is quite different from those of Bores 5, 6, 7, and 9. Only a rough correlation could be made batween these two groups. Bore 13 A strongly radioactive clay layer is located between the surface and 182 ft.
The resistance log indicates sand or silt layers interbeo.d8d vri th radioactive clay layers. Two zones at 122 and ';76 ft, distinguish8d both by bw resistances and low radioactivity, are interpreted as leached-out zones •
•
High-resistance P8MS, vrhich may possibly be caused by carbonaceous layers, are com..l10n throug...1.out thE: crosssection. An
appro:~imate
cor:::'elation with Bore 4A was made.
BorG 10 The resistance ::'og sho'ws alternating layers of clay and silt or sand above 24 ft. Possibly quite a number of the high-resistance peaks represe:::~t c8.1.'bonaceous material. Balow the ran~.;G 24-39 .f.~. 'uelow sea level, the form&. tion cOl1&ists mainly of clay. Tbe g8JDma-ray log suggests the pre~ence of !.eached zo.aeG. The correlation with neighbouring BOTe 13 is 'lI.!'.. certaill. Bore 8.. ---_ This bore was not legged. R8sults Plates 3 and 4 show the interpretation and correlation of the logs in diagrammatic cross-section. Plate 6 shows the location of a fictitious bp,o::ding plcme through d8pth zero of Bore 7, indicated by dashed cc·ntour :U l1e~-.;, and constructed fr:>m the cross-section of Plates 3 und 4.
8.
Plate 5 shoWR the relation of bedding planes to topography, illustrated by cross~sections. The bedding planes appear to be sub-parallel to parts of the western slope of Lawrenoe Vale hill. The average dip is about 1~~ degrees towards west. If the bedding planes serve as slip planes, which seems possible considering the nature of the clay beds, parts of Lawrenoe Vale hill may slip towards the west. On Plate 5 the lowest boundar.y of possible slip is indicated by lines through X1, ••• , X5. This is taken as the place where the dipping layers are approximately tangential to the surfaoe. On Plate 6 the interseotion of the above-ment~oned fictitious bedding plane through surfaoe at Bore 7 with the ground surface is indicated by a dash-dot line. Also, a shaded broken line through the plotted points X1, ••• , X5 (obtained from Plate 5) indioates the lowest boundar.y of possible slip along a bedding plane.
5. HOSPITAL AREA A group of five bores logs'were correlated in a similar logs. A geological oore log was shows the correlation of three of
(see Plate 1) w~s logged and the way to the Lawrence Vale bore reoeived for Bore 12. Plate 3 the five bore logs.
To compute the dip of the surface sediments a sketoh plan was made and the position of a marker bed (68-ft elevation at Bore 12) was indioated by elevation contours. It was found that the sediments dip about 17 degrees in the direction six degrees east of north. topo~aphioal
•
A seismic survey (Polak, 1962) showed that near Bore 12 the dolerite is about 30 ft below sea level. The logs of Bore 12 show generally higher resistance values and very low radioactivity below 34 ft below sea level, possibly confirming the presence of weathered dolerite. The seismic survey also showed that the dolerite surface slopes upward towards north. This explains why the overlying sediments with a downward slope towards north show no evidence of landslip, and indicates that they probably will not slip under load. Although the distance between the Hospital area bores and the Lawrenoe Vale bores is nearly one mile, it was possible to correlate between the two groups. A high-resistanoe marker at 210 ft in Bore 5 overlying a leached-out plastic clay, oorresponds with a similar feature at 114 ft in Bore 16, and at 91 ft in Bore12.
6.
CONCLUSIONS
The combination of radioactive logging and singlepoint resistance logging was found to be effeotive in the stu~ of the landslip problem.
9. The radioactive log indicates the variation in salt (potassium) content of the sediments. The results of the survey show that in the known landslip zones the salt content of the clay sediments has been largely or entirely leached out, ~. the log of Bore 9, which is located in or close to the worst landslip zone of the area, shows a conspicuous lack of radioactive anomalies from the surface down to a reduced level of 210 ft.
...
Therefore, it is considered that any place where the salt content has been leached out of the clay sediments should be regarded as a potential landslip zone. In Plates 3 and 4 corresponding features of resistance logs of the different bores are connected by dashed lines. In the Lawrence Vale area the leached zones form a regular pattern, which is also illustrated by Cross-section A-B of Plate 5.
In the Lawrence Vale area the smoothness of the contours of a fictitious bedding plane (Plate 6) suggests that no important faults are present in the upper beds, and that the beds dip about 10i degrees westwards. The dipping clay beds may easily serve as slip planes where they intersect the ground surface. The lowest boundary of possible slip (Plate 6) is indicated. It is significant that the worst landslip places are located east of and above this boundary am the western slope of the hill. The relation between bedding planes and topographY (Plate 5) also explains why the eastern side of Lawrence Vale hill forms a stable zone.
In the Hospital area the contours on a marker bed showed that the sediments dip about 17 degrees northwards. A seismic survey has shown that the dolerite surface at a depth of about 30 ft below sea level showed locally an upward slope towards north. This relation between dolerite surface and dipp~ilglC: bedding planes largely explains why this area appears to form a stable zone.
7.
REFERENCES
BAVER, L.D.
1940
SOIL PHYSICS New York, John Wiley & Sons p.87.
BJERRUM, L.
1954
Geotechnical properties of Norwegian marine clays. Geotechnigue Lond. 4 (2), 49-60.
.
10. GILL, E.D.
1962
The geology of Tasmania Cainozoic non-marine succession. J. geol. Soc. Aust. 9 (2), 236-
237. POLAK, E.J.
POLAK,
J~.J.
1962
Queen Victoria Hospital site seismic survey, Launceston, Bur. 1li.n. Tasmania 1961. Resour. Rec. 19627180 (unpubl.) Lawrence Vale geophysical survey, Launeeston, Tasmania 1960. Bur. Min., Resour. Aust. Ree. 1964/121 (unpubi:l
.'
,4
PLATE I
TASMANIA
REFERENCE TO AUSTRALIA STANDARD MAP SERIES: LAUNCESTON .
/ / LEGEN D
•
Bore hole loco Ii on
VALE, LAUNCESTON, TASMANIA
LOGGING SURVEY LOCATION PLAN 1000
P
a
!lOO
SCALE
IN FEET
1000 !iiOI.....;
Based
on
Lounceston
and
2000
3000
I
Environs Mop N02429. GEOPHYSICAL BRANCH. BUREAU OF MINERAL RESOURCES. GEO OGY AND TO ACCOMPAN Y RECORD No. 1964/120
PLATE 2
BORE 8 • R L. 36~'43 BORE 13
RL 2267
~
seA LE IN IOU
50
~---..,.
o,
100 !
I
FE ET 200
,
300
400 j
LAWRENCE VALE HILL
Contour Interval 50ft
LOCALITY MAP Oeoph!/siCdi Brdncn, Bureau Of Mineral /I. 990urce3,
r;,%!l!/ and Cl'oph!lslC'S.
K55-B5-66 TO ACCOMPANY RECORD No 1964/120
PLATE :3 BORE 7
360Q-
LAWRENCE VALE AREA
360 I t -
BORE 6
" --+--~
300fl-
300 f t -
• •
•• Leached
t-- 1--
I" -
---
I
•• •• Leach~d
••
• • f-----' •• ••
--
I" • • -
200fl
200fl -
•• •• •• ••
!~
plas/lc clay rn bore hole
-~ ~ ~
"
; :_J •• ••
~
~---
--
"
......
-
200 I t - -
----
g •• 2," • •
--
j
c
~
Leached
HOSPITAL AREA Bearing Bore 5 / Bore 7 Local dip 17° to the North
r---------- ----- - -
Olstance 1190 ft (appro x ) ____________________~'+I~,---------------
____
"0:..'0:$"IO"n"c,,e:::.:14""'2--'0'--'-1'-'-'lo=-p"-p"-r"o:..,,,I'---______________________-1
BORE 16
BORE 12 BORE 17 oXldised R greywocke
~--Pl
clay =::j:::=:::j
/'
/'
Leached
/' -IOOfl
100ft -
oK!d/sed sl/fstone
,,~
"
r
Leached
"1:'; ~"
,,~
(;)
---'
• • carbonaceous • • slllstone
~ ~
~ IRf-_-+----,
I
Leached
j
1---+-;
"
I"
j
?
Leached
J '" SlIp plone
j
DI s fane e 1 - - - - - - - - - - - - - ----
45 OO_f - c::'-'Io"p"'p"'r-'o'-',,,I'---_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ____
0'
o
o c
•
LEGEND
NORTH
SDUTH
[1~ I· ·1 H I
R
Leached zOf"le
High-resistance layer Interpreted
as corbonaceoJs layer Radioactive
zO"'le
Correla"lon line
• -+- --+--- -+-
Probable slip l(\ne through leached zone
GAMMA- RAY AND SINGLE-POINT RESISTIVITY LOGGING
CORRELATION OF BORE HOLES
No. 7,6,5,16,12, 17
Distance 150ft (o;lprox 1
-
-60f'
-t--GEQPHY$ICA.L
BRANC H ,BURE AU OF MINERA L RE SOURCE S,GEOLOG'1' AND GEOPHYSICS
K 55/ B 5 -67
TO ACCCMPANY RECORD No.1964/120
PLATE 4 BORE 9 BORE 7
~R
" --
----
•• ••
clay
300ft -
- 300 It
---
silt
LAWRENCE VALE AREA
R
-
BORE 3
clay
/
-
••
Silt
--- --f-
••
-
••
Leer:hed
·· .,.'
I t
R
"-
I
clay
CJ ~
"
R
R
- - 200ft
200ft -
/' /
~-
~
~
~
f-- -
<3, '--
"0;
-••
--
/ eoched
----
••
IR
•
-
, I
'""
"tJ QJ
, ,
/'
./
C>
;4::.
QJ
"t,
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"" ...
--J
-
CJ
J
"
""-
";;;
R
•• •• •• ••
-
--
-----
R
t/'"
-
----
Leacherj R
~
'> 100 f t -
"tJ
-IOOfl
"
CJ
:::: ;;; "--
()
''-" '"-"
~
+ __+-----=B'-'ec::a~r_-'.n:-=-g~1 ' 34 W __ _
"" '~
Distance 300 feet
Bearing N 84W
-
- - -------------------
---------...
Distance 380 feet
R CJ <::
.,'-
:::: CJ
R
Leached
_J
Bearing
••
N 36 W ------ ------1
01 stance 570 feet R
•• Approximate M S L
Approximate M S L
LEGEND
r
[1 I- -I H I
Leached lone
High -resistance layer Interpreted as Car bonaceou5 layer Radioactive lone
Correlation line Probable slip lone through leached lone
GAMMA-RAY AND SINGLE-POINT RESISTIVITY LOGGING
CORRELA TION OF BORE HOLES No.7 ,9,3,4A, 13, 10
GEOPHYSICAL BRANCH,BUREAU OF
MINERAL
RESOURCES,GEOLOGY AND GEOPHYSICS
K 55/85-68
TO ACCOMPANY RECORD No 1964/120
PLATE 5 BORE 7
BORE 9
300
----- - - -
IlJJ lJJ
"-
- -
'!:
A s>""
- 200
I-
<:
------
-------- --- --BORE 3
.-_.----- _. .
..----
x,
BORE 10
>
lJJ
--'
lJJ
-_.-_ . -_.--' - - ' - - .-_' . - _ . - - . -_.--
--:;:.
--
.... ~.
.~
..-----
.-.~
B
...,. Leached zones
-_.--' -_.---
100
r- 300
IlJJ lJJ
I
"-
C
~
""s>
I-
i
D
~ 200 !
<:
>
lJJ
--'
lJJ
100
300
I-
w w
"-
;;;:
E
z 2
200
I-
<:
>
-------- --
F
lJJ ..J W
-
100
I
300
--------~
IW lJJ
"-
;;;:
G
z
H
200
s>
100
I
-----------
300
I lW W
II I
"~
K
z
s>
L
200
100
FEET 100
50
a
100
300
200
LEGEND
/ I
I
/
/'
Bedding plane GAMMA-RAY AND SINGLE-POINT RESISTIVITY LOGGING
I
I
I
Lowest boundary of possible slip along bedding plane
CROSS-SECTIONS SHOWING RELATION BETWEEN BEDDING PLANES AND TOPOGRAPHY, LAWRENCE VALE AREA GEOPHYSICAL BRANCH,BUREAU OF MINERAL RESOURCES,GEOLOGY AND
GEOPHYSICsK55/85-49
TO ACCOMPANY RECORD No 1964/120
PLATE 6
·BORE 5
~o
o
\ BORE 6
•
G
''""
<::>
'-c.."
\
\
I
\
\
\
'"'"
<::>
C>
'"
<1\ C>
H
\ \
I
I
\
\ \
E
C
~
"
I I
\ yo
yO
'--
,"~ "" "-.
'-.
~
:~1'
"---~
BORE 10
/.
\
"',,,t; "
I
~\
A
I
I
r '",
"',
'"
I
-\--\
\ \
\
\ BORE 3
\
\
K 150
\
\
\ BORE 4 and 4A
i
FEET 100
50
a
100
200
300
LEGEND --/50 -
- - 3§O -
Topographical contours, Interval 50 feet -
-0--0--0-
TTTTTTT K------L
Contours on bedding plane (through surface at Bore71,lnterval 10 feet Intersection of above-mentioned bedding plane with ground surface Lowest boundary of possible slip along bedding plane Cross-sectton line
GAMMA-RAY AND SINGLE-POINT RESISTIVITY LOGGING
LAND SLIP AREA,LAWRENCE VALE
Area where bUildings are affected by landslip GEOPHYSICAL
BRANCH, BUREAU OF MINERAL RESOURCES,GEOLOGY AND GEOPHYSICS
K55/85 -50
TO ACCOMPANY RECORO No. 1964/120
