Oligocene of the Salin sub-basin, Myanmar

Joseph McNeil, Amy Gough, and Robert Hall

Aims
This project will look at defining the siliciclastic sediments from the Salin Sub-basin of the Central Myanmar Basin (CMB), onshore Myanmar. The focus of this project will be on the provenance of the Oligocene Shwezetaw and Padaung formations, which form vital components of the petroleum play. U-Pb dating of detrital zircons will be performed using LA-ICP- MS techniques on samples from multiple horizons within each formation. Point counting of light minerals will also take place. These techniques will aim to characterise the provenance of the Oligocene sediments of the CMB, and will provide an understanding of the sediment outing pathways draining into this Cenozoic sedimentary basin.

Background

Despite recent events in Rahkine State, Myanmar is currently experiencing a phase of relative sociopolitical stability. Hydrocarbon exploration is now encouraged, but little is known about the overall geological framework. The Central Myanmar Basin itself is situated between the Sagiang Fault in the east and the Kabaw Fault in the west. The basement of the Salin Sub-basin is covered by approximately 15000m of Cenozoic sediment as a result of quasicontinuous deposition since the end of the Mesozoic. From Palaeocene to Late Miocene times, shallow marine sedimentation prevailed, although an ephemeral fluvial influence was present. From the late Miocene, continental depositional systems are extant, as a result of the fluviatile Irrawaddy Formation prograding southwards over the Palaeocene-Miocene marine deposits. The Oligocene formations which are the focus of this study were deposited through a series of mixed marine and fluvial environments.

Previous provenance studies have focused on the Indo-Burman Ranges of Western Myanmar (formed from the West Burma Block), as the lithologies are well exposed and the area is easily accessible. In these initial studies, there has been very little heavy mineral analysis. Where limited U-Pb zircon data are available, a combination of Palaeogene–Cretaceous and Cambrian– Precambrian sources are present, which could be attributed to sediment influx from the Himalaya and from western Australia, although this also needs a more comprehensive study. This study is supported by a strong record of ages from the Himalaya, Indonesia, and Malaysia, although ages internal to Myanmar are mostly unknown, especially from the Cenozoic.

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.