Page 10 - Sumatra Geology, Resources and Tectonic Evolution

Simplified geological map of Sumatra

M. J. CROW & A. J. BARBER

Rock units are separated into time bands based on palaeontological evidence of age for the sediments and radiometric dating for the
intrusives and the volcanics. The main sources for the compilation of this geological map were: 1:250 000 scale quadrangle geology
maps published by the Geological Research and Development Centre between 1975 and 1996; the geological map of Northern Sumatra
at l:l 500 000 by Stephenson & Aspden (1982); the 1:1 000 000 geological maps of Sumatra compiled by Gafoer et al. (1992a, b, d);
the 1:250000 map of Central Sumatra by Hahn & Weber (1981a) and the map of Sumatra in the geological compilation of
Indonesia-West at 1:2 500 000 by M. C. G. Clarke (Land Resources 1990). Earlier sources consulted include the Netherlands East
Indies Geological Survey maps (1927-1931) of southern Sumatra at 1:200 000 and the compilations of parts of Sumatra at 1 : 1 000 000
by Zwierzijcki (1922a, b, 1930a).
Fontaine & Gafoer (1989) presented palaeontological evidence for a medial tectonic dislocation in Sumatra, which was defined by
Hutchison (1994). Outcrops of the Medial Sumatra Tectonic Zone (Barber & Crow 2003), the Kluet and Kuantan Formations, and the
Bohorok and equivalent formations in the Tigapuluh Mountains, shown on the map are based on published and unpublished descriptions
of the deformation, as discussed in Chapter 13 (2005, this volume).
The ages of granitic intrusions for Sumatra are from Chapter 5, and for the Tin Islands from Cobbing et al. (1992). The solid geology of
Bangka Island is taken from Ko (1986).