Sundaland sediments

Provenance of Sundaland sediments: Peninsular Malaysia & Sumatra

Inga Sevastjanova, completed PhD project

This project aims to carry out detailed studies of both modern sediments and thier Mesozic equivalents from across the southern Sundaland region aiming to establish the mineralogical and geochemical character of sediments deriving from these regions. Little is known about the mineralogical character and source of sediments in many SE Asian basins, despite the fact that many of these basins contain abundant hydrocarbons.

Building on recent studies, this project will involve analyses of Mesoozic sedimentary rocks from the Malay Peninsula as well as modern sediments coming off Sumatra.

Understanding of sediment dispersal within various basins at present is important as it has been widely assumed that sediment within Indonesian basins has been derived from distant sources such as the Himalaya rather than local sources. However, recent SE Asia Research Group provenance studies have favoured local sources. Investigating modern sediments is also a fast way of characterising different parts of Sundaland, which may aid provenance interpretation of older Cenozoic sediments. This project will focus on the provenance of Sumatran and Javanese sediments, using modern river sediments from selected drainage basins, sedimentary rocks of different ages from the same areas, and likely basement source rocks.

Analysis of the major detrital constituents or light minerals is routinely used to interpret the provenance and tectonic setting of sandstones. Heavy mineral analysis is useful for making provenance interpretations, as long as the provenance signal is successfully distinguished from the effects of hydraulic sorting and chemical destruction. Heavy mineral fractions in sandstones can also be used to identify sediment pathways, sediment dispersal patterns, sedimentary environments and for correlation of barren strata.

River clays will be analysed with a view to gathering average crustal isotopic values using isotope dilution techniques for a number of systems, focusing on Sm-Nd. The results will be integrated with mineral information to create a comprehensive data set pertaining to erosion products of, and therefore the crust of, the south Sundaland region. Samples of sand and clay from rivers in selected drainage basins on the islands of Sumatra and Java were collected in 2007 and are being processed at RHUL. In addition, material previously collected in Java by Dr Helen Smyth is being analyzed.

Ultimately the aim is to build a model of drainage development in southern Sundaland for the Cenozoic. This will be integrated with tectonic models of the region to better understand the timing of uplift in different parts of Indonesia and to improve models of the tectonic evolution of Indonesia.

Recent Papers –

Max Webb et al., 2020. Isotopic mapping reveals the location of crustal fragments along a long-lived convergent plate boundary. Lithos.

https://doi.org/10.1016/j.lithos.2020.105687

Max Webb et al., 2020. The history of Cenozoic magmatism and collision in NW New Guinea – New insights into the tectonic evolution of the northernmost margin of the Australian Plate. Gondwana Research.

https://doi.org/10.1016/j.gr.2019.12.010

Amy Gough et al., 2020. Mid-Cenozoic fluvio-deltaic to marine environments of the Salin Sub-basin, Central Myanmar. Journal of Asian Earth Sciences.

https://doi.org/10.1016/j.jseaes.2019.104143

Recent News –

Amy Gough and Max Webb attended the Restech 2.0 Virtual Reservoir Conference. Amy Gough presented new SEARG research on the pitfalls of light mineral studies for sedimentary provenance in tropical climates.

Amy Gough was awarded an honorary research fellowship of the British Geological Survey and continues to foster collaborative relationships between SEARG and the BGS.