A. Tobler

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tagsperson, geologist, dutch, colonial, scholar
aliasesA. TOBLER, Tobler, Tobler (geologist)

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A. Tobler was a Dutch mining geologist of the Netherlands Indies Geological Survey whose 1919 Djambi Verslag (“Jambi Report”) and subsequent reports on the coal and gold-silver occurrences of central and northern Sumatra are among the principal printed sources for the colonial mineralogical literature on the island. In the Atjeh connection, Tobler’s significance is twofold: his 1919 report on the contact-metamorphic origin of the Muara Sipongi iron-ore deposits just south of the Atjeh border established the geological model that Jansen, Lindberg and Wolvekamp would later apply to the Atjeh iron-ore localities, and his general survey of the Sumatran gold-silver belt — including the observation that “Remains of former native gold mining are numerous and have been found in many places from Atjeh in the North to Benkulen in the South” — fixed the geographical frame within which Atjeh’s gold occurrences have subsequently been discussed.

The 1919 Djambi Verslag

Tobler’s Djambi Verslag — cited in the standard form “A. TOBLER, Djambi Verslag. Jb. Mw. 1919 Verh. III: Versl. & Meded. Ind. Delfst., No. 13” — was the Geological Survey’s principal report on the coal and oil occurrences of the Djambi residency in central Sumatra. Van Bemmelen cites it repeatedly in the coal chapter of *The Geology of Indonesia* for the permo-carboniferous coal seams along the Batang Tabir, B. Tembesi and B. Merangin rivers, for the lower-miocene coal beds of the Tigapuluh Mountains, and for the cannel-coal-type paleogene coal of Djambi. The same report is the source for Tobler’s survey of the Djambi oil structures, which Van Bemmelen draws on in the petroleum chapter for his statement that “many anticlines are known in Djambi (TOBLER, 1922)” — Tobler’s later published version of the Djambi survey.

The Muara Sipongi iron-ore report

For the Atjeh connection, Tobler’s most directly relevant contribution is his work on the iron-ore deposits at Muara Sipongi, in the Rawas district of Tapanuli, immediately south of the Atjeh border. Van Bemmelen, citing Hövig (1918) and the Verslagen en Mededeelingen Nr. 7 (p. 21), records that Tobler “explicitly indicated the contact-metamorphic origin of the ore. According to him, contact-metamorphism was effected by the granite and not by the diabase; the slate-formation on the West side, although adjoined by diabase, has not been altered by contact-metamorphism.” This argument — that the magnetite and hematite of the northern-Sumatran slate-formation are contact-metamorphic deposits formed at the granite contact, not at the diabase contact — supplied the geological model that Jansen, Lindberg and Wolvekamp would later apply to the Atjeh iron-ore localities further north (Kr. Geuenteuet, Gle Mon Ampeuet, Kr. Ligan, Kr. Rigaih, Alu Talu).

The Atjeh-to-Benkulen gold-silver belt

Tobler is also the source for the canonical statement on the geographical extent of the Sumatran gold-silver mineral province. Van Bemmelen cites him (alongside Hövig 1914) for the observation that:

“Remains of former native gold mining are numerous and have been found in many places from Atjeh in the North to Benkulen in the South.”

This single sentence fixed, for the colonial mineralogical literature, the framing of the Sumatran gold-silver belt as a continuous mineral province extending from the northern tip of Atjeh to the southern tip of Benkulen — a framing within which the Atjeh occurrences (the S. Assai and S. Meranging quartz-veins, the Meulaboh placers, the West-Atjeh alluvial deposits) take their place as the northern terminus of the belt.

Significance

Tobler is significant for the encyclopedia of Acheh history on three grounds. First, his Djambi Verslag and subsequent reports supplied the geological model — contact-metamorphic origin at the granite contact — that the 1922 Jansen-Lindberg-Wolvekamp survey applied to the Atjeh iron-ore localities. Second, his statement on the Atjeh-to-Benkulen extent of the Sumatran gold-silver belt fixed the geographical frame within which the Atjeh gold occurrences have subsequently been discussed. Third, his work at Muara Sipongi, immediately south of the Atjeh border, provided the immediate geological context for the Atjeh mineralogy: the same slate-formation, the same granite intrusions, the same contact-metamorphic magnetite-hematite deposits run continuously from Tapanuli into Atjeh, and Tobler’s work on the southern side of the border is accordingly indispensable to any understanding of the northern side.

See Also

Source

The Geology of Indonesia, by R. W. van Bemmelen, Vol. II: Economic Geology (The Hague: Government Printing Office; Martinus Nijhoff, 1949), pp. 58–60 (Djambi coals), p. 105 (Atjeh-to-Benkulen gold belt), p. 209 (Muara Sipongi contact-metamorphic origin). Tobler’s own works cited as: Djambi Verslag, in Jaarboek van het Mijnwezen 1919, Verh. III; Verslagen en Mededeelingen Ind. Delfstoffen, No. 13 (Batavia 1921); and “TOBLER, 1922” for the Djambi anticlines (petroleum chapter) and the Sungei Pagu, Sungei Salak and other mercury localities (pp. 463, 465, 466, 467).

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