Christof Liebermann, Robert Hall and Amy Gough
The aim of this project is to investigate the Cenozoic evolution and unroofing of the Sumatran volcanic arc using petrological studies of sandstones and their heavy minerals, including zircons, in order to characterise Sumatra as a potential source area for the many hydrocarbon-rich Cenozoic sedimentary basins of the region.
This project will involve a sampling and zircon age-dating program in Sumatra, focusing on sandstones of a wide range of depositional ages, as well as modern river sands, although these may be dominated by detritus derived from the recent volcanic arc. Zircon U-Pb dating will be performed using LA-ICP-MS and possibly SHRIMP analysis. Detrital mineral studies will be coupled with heavy mineral analyses. The project aims to characterise zircon age populations diagnostic of Sumatran basement and will provide an understanding of sedimentary pathways from Sumatra to the Cenozoic sedimentary basins.
Sumatra and its forearc are often cited as an example of a classic accretionary margin, but field-based studies question this model. Paleogene and Neogene sandstones on Nias are derived predominantly from Sumatra and record its unroofing history but little is known about their heavy mineral assemblages and zircon ages. Sumatra is composed of the Cenozoic volcanic arc built on an uplifted basement exposed in the Barisan Mountains. To the north of the Barisan Mountains are basins containing thick (up to 5 km in the North Sumatra Basin) terrestrial to shallow marine siliciclastic sediments. These basins are often interpreted as back-arc basins, although they are older than the volcanic arc and lie on continental crust. The basement includes granitoids, which are likely to have provided detritus to the basins onshore and in the forearc, and may be as old as Devonian in age. There is limited information on the igneous history of the island, and preceding studies are mostly based on K-Ar dating. Detrital U-Pb ages are not available of either basement rocks (including also the younger Permo-Carboniferous metasediments) or from the Cenozoic sedimentary rocks.