Mesozoic-Cenozoic sedimentary rocks, Sarawak, Malaysia

Tim Breitfield – completed PhD project

This project investigated mainly terrestrial sandstones from Sarawak to determine their provenance and improve our understanding of the Cretaceous-Cenozoic evolution of Sundaland.

Sarawak is one of the least well-known and studied parts of the Sundaland region. Since the region was mapped by colonial surveys, oil companies and the Malaysian Geological Survey in the 1950s to 1970s there has been relatively little published work. The early work was completed in the period before plate tectonic concepts and despite the excellence of mapping, some stratigraphy remains confused because of fixist assumptions. Later studies incorporated new thinking and identified sutures but no tectonic models have explained where supposed colliding blocks came from and when they amalgamated – the region is typically missing from reconstructions.

–

From north to south across the Lupar Line there is an abrupt change from terrestrial/marginal marine to deep water sediments. This tectonic boundary has been suggested to be a suture but some of the expected features of a subduction-related collision are missing, such as a clear volcanic arc and compatible deformation histories on each side of the line. The linear character of the boundary and the deformation history on each side of it, in both Sarawak and northern Kalimantan, suggest this could be an important strike-slip boundary active in the early Cenozoic.

South of the Lupar Line many sandstones are poorly dated because they are predominantly terrestrial. Revisions of Cretaceous and Cenozoic palynology dating schemes means that ages remain uncertain. There have been no provenance studies. We propose to investigate the provenance and age of the sandstones using heavy minerals, zircon dating, palynological and micropalaeontological dating, and radiometric dating of igneous rocks. Data acquired by the SE Asia Research Group in recent projects from regions such as the Malay peninsula, Sabah and Kalimantan will help interpret information from Sarawak and improve tectonic models for the region.

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.