GEOSEJl '98 ProceeJillp, Geo /. So c. Jl1aLaYJ ia BilL!. 45, December 1999; pp . 481-489 Ninth Regional Congress on Geology, Mineral and GEOSEA '98 Energy Resources of Southeast - GEOSEA '98 17 - 19 August 1998 • Shangri-La Hotel, ,

Geophysical measurements for archaeological investigation: case studies in Malaysia

ABDUL RAHIM SAMSUDIN AND UMAR HAMZAH

Department of Geology Universiti Kebangsaan Malaysia Bangi, 43600, D.E. Malaysia

Abstract: Three archaeological sites containing different artifacts were investigated by geophysical methods. The first site is located at Sungai Mas village in of , north west of Malaysia. Since the beginning of the 1980 this site has produced a number of important and interesting archaeological finds relevant to the history of the ofKedah. The archaeological teams from Universiti Kebangsaan Malaysia and the Museum Department of Malaysia revealed that there were several remains of low mounds of laterite block and brick foundation for 'structures in the village. A geoelectrical profiling method using dipole-dipole array was used to study the artifacts and the preliminary survey was designed to see whether the technique would be useful for identifying and locating anomalies of archaeological significance in the area. Result of the study indicates that the geoelectrical resistivity method can be successfully used in detecting archaeological anomalies of shallow buried artifacts in the studied area. The second site is situated in a fisherman's village on the northern bank of Kedah River mouth and it lies in a coastal lowland area of Di strict. The site is located approximately 7 kilometres from Alor Star, northern Kedah. It covers an area of about 3.5 hectares along the river side. Remains of partly buried nineteenth century fort which belong to the former of Kedah was excavated by the Museum Department of Malaysia for future conservation plan. The area was gazetted as a museum reserve and planned to be developed as another historical tourist spot in Kedah. Geophysical measurements employing gvoelectric profiling (Wenner array) and magnetic surveys were conducted to locate structures of partly ) uried foundation of the fort as a guide for future conservation work. Both the geoelectrical and magnetic surveys have produced results showing several :m omalous areas which appear to coincide well with the locations of-the uncovered artifacts. The third archaeological site is located in the area of Pasir Salak historical complex in Kampong Gajah Di ~ trict, southern . The site which covers an area of 80 x 60 square metres lies about 200 metres from the Perak River. It was identified to be a site of a former fort built by a Malay warrior to fight the British in the late nineteenth century. The site was developed into a football field for the school nearby before the land was gazetted as a museum reserve. The department of muselJm has conducted four phases of excavation in December 1990, April 1991, June 1993 and July 1996 but no significant major artifact was found. Detailed geophysical study (geoelectric and magnetic) was carried out to look for artifact. The geoelectrical profiling survey employing dipole-dipole array revealed eight different locations of high resistivity zones whereas the magnetic measurement indicated two anomalous areas. These anomalous areas could probably be associated with the artifact of archaeological significance and they need to be confirmed by excavation.

INTRODUCTION it provides three dimensional information about potential archaeological targets without disturbing Geophysical techniques have been successfully them. Information on archaeological site location used to investigate archaeological sites in many and content should be obtained in the least parts ofthe world. Archaeologists using geophysical expensive and least destructive manner possible. methods now routinely map hearths as well as soil Archaeologists are very well aware that excavation materials magnetically altered by campfires. The destroys the site being studied. The need for use of geophysical techniques for this type of study nondestructive methods increased lately for two is classified as 'nondestructive archaeology' because reasons. First, our environmental legislation now 482 ABDUL RAHIM SAMSUDIN AND UMAR HAMZAH requires that historic places or structures need to and mounds. Besides the dependence on soil be mitigated on land to be developed or altered. properties, soil resistivity contrast depends upon Secondly, there is an increasing movement to assess the recent weather history of the site. Historic and preserve our archaeological heritage on public architectural features such as foundations or house lands not in immediate danger of destruction. floors and walls usually provide good resistivity The geophysical technique. is very useful to contrast. archaeologist who wish to preserve the cultural For archaeological sites 1 and 3, a conventional heritage as well as to study it. The early history resistivity profiling method employing dipole-dipole and development of the techniques for array was conducted using ABEM SAS300 archaeological investigation are described by terrameter with four- in-line metal electrodes. The Weymouth and Huggins (1985), Aitken (1974) and meter reads resistance directly in ohm and values' Weymouth (1985). Archaeogeophysical are converted to apparent resistivity by multiplying investigation case studies discussed in this paper the resistance by the appropriate geometry factor can be classified as 'intrasite mapping' because for the array (Zohdy et al., 1974). The resistivity they were used to guide excavation programmes meter was connected to two potential and two within already discovered sites. This paper will current electrodes. The electrode spacing of 1 m highlight results of geophysical investigation at was used with transmitter-receiver separation (N) three archaeological sites containing different ranging from 1 to 6 m. Different electrode spacings artifacts in north west Malaysia. The first site (site (N) reflect different depths of investigation. The 1) is located at Sungai Mas village in Kuala Muda electrode configuration used is shown in Figure 2. District of Kedah and the second site (site 2) lies in For data plotting, each measured value was plotted the vicinity of the Kedah river side in the Kuala at the intersection of two 45° lines through the Kedah area. Whereas the third site (site 3) is centres of the dipoles. The measurements resulted . situated in Pasir Salak district in Perak (Fig. 1). in the resistivity pseudo section. Isoresistivity maps which indicates areal distribution of the resistivity GEOPHYSICAL METHODS were also prepared to determine which N or depth value would shows the best correspondence with These case studies illustrate the applicability known or suspected archaeologioal features. of geophysica1 methods in archae~lqgical Archeological site 2 was investigated using a investigation in Malaysia. Geophysical methods new electrical imaging method (Griffiths and that are widely used for this type of study. are Barker, 1993) which is now frequently used for geoelectrical resistivity ineasurements, ground­ environmental studies. . The electrical imaging penetrating radar and magnetometry. However survey was carried out with a multi-electrode for these case studies, only two of the above resistivity meter system (Fig. -a). In this particular geophysical techniques (geoelectrical resistivity and study, a total of fifty electrodes were laid out in a magnetic) were used. Brief description of the straight line with a constant spacing. Each of the techniques and their .field procedures are discussed electrode is connected to Ii multi-core cable and a in the following sections. switch box system which was used to manually select the active electrodes used for each i) Geoelectrical resistivity method measurement. The data collected was interpreted The resistivity method appears to be very useful using a rapid 2-D resistivity inversion programme in detecting building materials such as bricks and (RES2DINV) which automatically determines a two­ lateritic blocks because these objects are expected dimensional (2-D) resistivity model for the to have high resistivity and excavations may be subsurface using the data obtained from electrical resistivity highs or resistivity lows depending on imaging survey (Griffiths and Barker, 1993). the water content and degree of compaction of the materials compared to the surrounding medium (ii) Magnetic method (Umar Hamzah and Abdul Rahim Samsudin, 1995). Magnetic survey is the geophysical technique However the success of the resistivity method in most frequently used by the archaeologist. It is determining the archaeological features would routinely used to map buried stone foundations depend on the resistivity contrast between the and to determine the locations of forges and kilns, objects and the surrounding rocks or soils. Soils hearths, and campfire sites (Gibson, 1986). Most having similar resistivity would tend to hide the burned features and bricks produce strong magnetic anomaly produced by the archaeological object anomalies as a result of the conversion of iron within it. Resistivity contrasts can occur in some oxides to a more magnetic state, and because of earthen features, such as storage pits, filled ditches thermoremanent magnetisation. The response to

CEOSEA '98 ProceeiJingJ (CSM Bull. 43) ~ R ;a <::-. N= I N=2 N=3 N=4 .," ..... rB--l ~--®--r-@-T-@--! ~ IQ , 7 7 7 7 , / / / / , / / / / G) / / / ,/ ~ -0 ~/ ~/ ~/ N=I :::I: • • X • Ci3 / '.J/ / / ,. :11 ., " N=2 ~ • / //, / / • s:: N=3 c~ • • • ::c / " / ,. X / .-/ It ., ,./' J( ~ • • N=4 m / / / / , ~ CS ::c > Figure 2. The presentation of dipole-dipole resistivity results on a pseudosection. 'N' ~ represents the relative spacing between the current and potential electrode pairs. ~ ~ 8 ~ ~ Station 32 , m C P P C II 30 II 30 12 30 ,2 o~ ;;; Stotion 18 + Archaeological site ,------..., ~m ~I 20 PII 20 PI2 20 ~2

~ __201cm ~ Station I o I ' I rn CI PI P2 C2 E lee trode Number z Data 5 6 7 8 9 10 II 12 13 s: Level > N= I I- § N=2 18------J> N=3 - - N=4 32- 43 N=5 - 51- N=6 56- Figure 1. Map of showing location of archaeological sites. Figure 3. The arrangement of electrodes for 2-D electrical imaging survey and the ~ ex> sequence of measurements used to build up a pseudosection. U) 484 ABDUL RAHIM SAMSUDIN AND UMAR HAMZAH foundations and floors depends upon the magnetic Based on results of geoelectrical sounding contrast of the construction material with respect surveys, three categories of soil resistivities were to the surrounding soils. Earthen features, such as observed for the study site: storage pits with humic content, can produce i) soil with resistivity less than 20 ohm-m observable anomalies because of the conversion of ii) soil with resistivity ranges from 20 to 200 ohm-m iron oxides (reduction of hematite to magnetite) iii) soil with resistivity greater than 200 ohm-m that takes place in an organic environment. The first category of the low resistivity is Concentrations offerrous metal give good magnetic interpreted to be related to marine sediment or response. Low magnetic contrasts between objects sandy soil with salt water content. The second and the surrounding soil, varying soil composition, category of resistivity reading is referred to alluvium and an increased depth of burial can obscure or sandy soil with brackish to fresh water contents. magnetic anomalies. Whereas the third category of relatively high The magnetic survey was carried out using resistivity values could be related to the soil material proton precession magnetometer for sites 2 and 3. associated with considerable amount of buried The measurements were made at heights of 0.5 m archaeological objects. and 1.0 m above ground, at 2 to 3 m interval along A total of six isoresistivity maps for different the same traverses used in the resistivity survey. values ofN and ten resistivity pseudo sections were At each position, three magnetometer readings were obtained from the resistivity measurements. The taken and averaged. The magnetic field gradient isoresistivity maps for different value ofN indicate was found by subtracting the 1.5 m field strength the variation of resistivity at different horizon below from that found at 0.5 m. Contour map ofthe field surface. The plots of isoresistivity maps for N = 1, gradient will shows the shallow sources which 2, 3 and 4 consistently reveal the presence of four probably associated with the artifacts of distinct anomalies of high resistivity. These archaeological significance and reduces regional anomalies are relatively large in term of size area gradients and removes drift. and illustrated as anomalies A, B, C and D in Figure 4. Location of these anomalies coincide well CASE STUDIES with the artifacts which were revealed from the earlier excavation programme in the study area. Depths of the artifacts interpreted from the (i) Sungai Mas, Kuala Muda, Kedah resistivity pseudosection range from 0.1 to 2.5 m Since the beginning of the 1980 Sungai Mas below surface. area of Kuala Muda, Kedah has produced a number Two or possibly five more. anomalies were of important and interesting archaeological finds observed in the isoresistivity maps for N = 5 and 6. relevant to the history of the Bujang Valley of Their pseudosection plots suggest that these Kedah (Nik Hassan Nik Shuhaimi Bin Nik Abd. anomalies could be produced by the artifacts buried Rahman and Kamaruddin bin Zakaria, 1993. The at much deeper level (greater than 3 metres). If archaeological teams from Universiti Kebangsaan this information is true, deep excavation is therefore Malaysia and the Museum Department of Malaysia necessary for this site and it would involves revealed that there were several remains of low excavation work below water table. However these mounds of laterite block and brick foundation for results need to be confirmed by conducting more structures in the village. . detailed geoelectrical investigation or other A geoelectrical profiling survey using dipole­ geophysical methods such as magnetic or ground­ dipole array was used to study the artifacts. The penetrating radar. The magnetic method is not study was designed to see whether the geoelectrical possible to be applied in this area due to the presence technique would be useful for identifying and of many man made magnetic disturbances such as locating anomalies of archaeological significance in steel fences and houses. the studied area. Site of investigation is located close to Sg. Muda (ii) Fort of Kuala Kedah, Kedah and covers an area with dimension of approximately The second site is situated in a fisherman's 100 m x 100 m. The area which has relatively flat village on the northern bank of Kedah River mouth topography consists of alluvium and coastal marine and it lies in a coastal lowland area of Kuala Kedah deposit. The resistivity of the soil is low and District. The site is located approximately 7 homogenous. The artifacts represented by old bricks kilometres from Alor Star, northern Kedah. It and rocks were found buried by the soil at relatively covers an area of about 3.5 hectares in the vicinity shallow depth. The resistivity of these artifacts are of the Kedah River side. Remains of partly buried expected to be high and therefore should be easily nineteenth century fort which belong to the former detected by the resistivity survey. Sultan of Kedah was partially excavated by the CEOSEA '98 ProceeoingJ (CSM BuLL. 43) GEOPHYSICAL MEASUREMENTS FOR ARCHAEOLOGICAL INVESTIGATION: CASE STUDIES IN MALAYSIA 485

N= 1

1000.00

N=2 900.00

800.00

700.00

500.00

400.00

300.00

N=3 200.00

100.00

0.00

N=4

Figure 4. Resistivity map over buried r emains of building at Sungai Mas archaeological site.

December 1999 486 ABDUL RAHIM SAMSUDIN AND UMAR HAMZAH Museum Department of Malaysia since early 1996 were carried out along a series of parallel lines of for future conservation plan. The area has been 5 metres apart to detect any possibility of buried gazetted as a museum reserve and would be artifact in the studied area. Plots of isoresistivity developed as a historical tourist spot in Kedah. maps for N = 1 to N = 4 reveal the presence of Geoelectrical imaging and magnetic surveys were several anomalies of high resistivity (Fig. 6) in the conducted on selected sites of the studied area to studied area. The ground at these anomalous locate structures of buried foundation of the fort. locations were not exposed before and further Geoelectrical resistivity imaging and magnetic excavation of the ground was proposed to look for surveys were carried out only on selected areas of artifacts of archaeological significance. the site due to poor ground condition. The A magnetic gradient map indicates two geoelectrical imaging survey using Wenner array anomalous areas. However, these anomalous zones was carried out along a series of parallel profiles had been excavated earlier by the Museum about 6 metres apart to map the lateral and vertical Department of Malaysia where no objects of extent of the fort foundation. Figure 5 shows the archaeological interest were found. isoresistivity maps for horizons (N) = 1, 2, 3 and 4 indicating the locations and lateral distribution of CONCLUSION the anomalies. Field evidence shows that the high resistivity anomalies corresponds to the wall of the The case studies presented in this paper fort foundation which was buried in the low illustrate the potential use of geophysical methods resistivity soil of marine clay. Resistivity model in archaeological intrasite mapping in Malaysia. sections of the survey lines indicate that the zones Results of geoelectrical resistivity and magnetic of high resistivity occurred at depths ranging from surveys demonstrate that the techniques are non­ 0.1 to 5.0 metres below ground. destructive and very useful in providing information Magnetic survey was carried out at the remains about the subsurface content of archaeological sites. of partially buried brick floor and wall of the fort. The success of these techniques depends on the The main objective of the survey was to determine resistivity and magnetic contrasts of the artifacts. the magnetic anomaly of the buried structures and with soils surrounding it. the associated buried artifacts. High magnet~c It is also important to note that anomalies gradient was obtained in the area of the floor obtained through any geophysical method should structure which suggests that the anomaly could not necessarily be associated with objects of possibly be due to the bricks of the floor material or archaeological significance. Subsurface geological other highly magnetic objects of archaeological information as well as geological history of the area significance. However this would requires actual should be thoroughly investigated before a ground excavation for confirmation. meaningful geophysical interpretation could be made. (iii) Pasir Salak, Perak The geophysical techniques, if applicable, can The third archaeological site is located in the delineate archaeological sites and help area of Pasir Salak historical complex in Kampong archaeologists in their initial planning of an Gajah District, south of Perak. The site which excavation programme. The information from the covers an area of about 80 x 60 square metres lies geophysical study would also indirectly safe about 200 metres away from the Perak River. It operating cost on site investigation by reducing was identified to be a site of a former fort built by number of pits and avoiding unnecessary digging. a great Malay warrior (well known as Dato' Maharaja Lela) to fight the British Resident of REFERENCES Perak in the late nineteenth century. The site was developed into a football field for the school nearby AITKEN, M.J., 1974. Physics and archaeology, 2nd ed. Oxford before the land was gazetted as a museum reserve. Univ. Press. The department of museum has conducted three GIBSON, T.H., 1986. Magnetic prospection on prehistoric sites phases of excavation in the studied area but no in western Canada, Geophysics, 51(3), 553-560. GRIFFITHS, D.H. AND BARKER, R.D., 1993. Two dimensional significant artifact was found. Both geoelectrical resistivity imaging and modelling in areas of complex profiling and magnetic surveys were conducted to geology. Journal of applied Geophysics, 29, 211-226. search for the possibility of buried artifacts within NIK HASSAN SHUHAIMI BIN NIl< ABO. RAHMAN AND KAMARUDDIN the identified site of the fort. BIN ZAKARIA, 1993. Recent archaeological discoveries in Geoelectrical resistivity profiling employing Sungai Mas, Kuala Muda, Kedah. JMBRAS, 66, 73-80. dipole-dipole array and magnetic measurements UMAR HAMZAH AND ABDUL RAHIM SAMSUDIN, 1995. Teknik

CEOSEA '98 ProceedingJ (CSM BuLL. 45) GEOPHYSICAL MEASURE MENTS FOR ARCHAEOLOGICAL INVESTIGATION: CASE STUDIES IN IA 487

- N=1

-.0

0 ~ \"@) o~ ~ CQ N=2 - ~~ c::::=J 600.00 - 550.00 .s:>. ~C':::" C) 500.00 """" 00 ~ <0 0 450.00 ..., g~ -"'" 400.00 ...0 350.00 300.00 N=3 250.00 d=J - 200.00 ~ ~, 150.00

~ ~D 00 100.00 ~~ 50.00 ~ 0.00

- N=4 -~'--

- ...,

-.0

Figure 5. Resistivity anomalous areas of arch aeological site in Kuala Kedah, Kedah.

Decelllber 1999 488 ABDUL RAH IM SAMSUDIN AND UMAR HAMZAH

600.00

500.00

400.00 ..... 300.00

200.00

100.00

0.00

Figure 6. Pasir Salak arch aeological site showing anomalous resistivity zones.

CEOSEfl '98 Proceedill.fJd (CSJl1 BllLL. 45) GEOPHYSICAL MEASUREMENTS FOR ARCHAEOLOGICAL INVESTIGATION: CASE STUDIES IN MALAYSIA 489

Pengprofilan geoelektrik dalam eksplorasi arkeologi di WEYMOUTH,J.W., 1985. Geophysical Methods of archaeological Sungai Mas, , Kedah. Sains Malaysiana, site surveying. In: Schiffer, M. (Ed.), Advances in 24(1),29-44. archaeological method and theory, 9. Academic Press. WEYMOUTH,J.W.ANOHuGGINs,R,1985. Geophysicalsurveying ZOHOY,AAR, EATON, G.P. AND MAJjEY, D.R., 1974. Application of archaeological sites. In: Rapp, G., and Gifford, J. of surface geophysics to groundwater investigations. U.S. (Eds.), Archaeology geology. Yale University Press. Government printing Office, Washington, D.C.

------.~.-~-+.~.------Manllscript received 26 October 1998

December 1999