Contents - Akademi Sains Malaysia

ASM Science Journal, Volume 7(1), 2013The eruption of the Toba Volcano, they argued, had caused a layer of ash of up to 5 metres thick in places to be depositedin Kota Tampan. Today, Kota Tampan is an important archaeological site in Peninsular Malaysia. The volcanic ash occurs“among and above stone artefacts, manufactured by anatomically modern humans” (Storey et al.).However, in an earlier paper byTjia and Fatihah (2008), they quotedwork by a number of researchers whohad worked on samples attributedto four volcanoes in Sumatra, that isfrom Toba, Maninjau, Aekgadang andTanjung Karang (Figure 2). Theyquoted from fission-track age datingconducted on zircons collected fromthe rhyolitic ash of four volcanoesin Sumatra by Nishimura (1980)(Table 1).(Source: .)Figure 1. Location of Lake Toba, Sumatra, and Kota Tampan, Lenggong Valley,Perak, Malaysia.a105ºE–5ºaTobaTobaManinjau andNgarai SianokManinjau andNgarai Sianok95ºE 100ºE95ºE 100ºEQuaternaryRhyoliticash in SumateraQuaternaryRhyoliticash in SumateraAekgadang105ºEAekgadangTanjungkarangTanjungkarangFigure 2. Locations of volcanoes in Sumatra (Tjia & Fatihah 2008).–5º0º0º–5º N–5º NNishimura (1980) reported that theTuba tuffs from three locations gavethree different fission track ages of1.2 million years, 100 000 years and30 000 years (the youngest eruption),none giving an age equivalent to70 000 years. Tjia and Fatihah (2008)reported that there were at least twomore Toba eruptions. An ignimbritefrom the eastern lake shore of theSamosir peninsula, some 700 m belowthe summit surface, gave a K/Ar age of1.9 ±0.4 Ma (Tjia & Kusnaeny 1976)and possibly represent an older andfourth eruption. A fifth catastrophiceruption at Toba was suggested byYokoyama et al. (1980).The only tuffs which gave fissiontrack ages identical or close to Storey,Roberts and Saidin’s40 Ar/ 39 Ar of73 880 years are those from Bukittinggi(70 000 years) and Maninjau (80 000years). The two other volcanic centresof Aekgadang and Tanjung Karang,in the south of Sumatra, gave fissiontrack ages of 3.5 million years and1 million years respectively, rulingout both volcanoes effectively as thesource of the Kota Tampan’s youngishash beds. Maninjau in westernSumatra is some 500 km southsouth-westof Kota Tampan. Tjia andFatihah (2008), when describing theBukittinggi tuffs covering a large areaaround Maninjau, reported that the“extremely great thickness (about 200metres) of the second tuff unit shouldrepresent a paroxysmal event whosetephra was distributed throughout a72