A new upper Paleogene to Neogene stratigraphy for Sarawak and Labuan in northwestern Borneo: Paleogeography of the eastern Sundaland margin

Abstract

The Miri Zone in Sarawak contains thick Paleogene to Neogene sedimentary successions that extend offshore into the Sarawak Basin (Balingian and Central Luconia Provinces) and Sabah Basin. Exploration offshore has shown the Sarawak Basin in the South China Sea contains major hydrocarbon reservoirs. The sediments on land are age equivalents of the offshore successions and can be used to provide insights into their sedimentological and stratigraphic relations. However, because the rocks are found in mountainous regions covered by dense rainforest much of the stratigraphy in the Miri Zone is poorly known, as are timings and causes of major unconformities in the region that are essential for understanding the tectonic history, basin development, and sedimentary pathways. In this study we integrate fieldwork, U-Pb zircon dating, biostratigraphy, and light and heavy mineral analyses to present a revised stratigraphy for the region as well as paleogeographic maps, including major paleo-river systems for the main sedimentary basins. Rocks studied include parts of the Cretaceous to Eocene deep marine Rajang Group, fluvial to marginal marine sediments of the Oligocene to Early Miocene Tatau, Buan, Nyalau and Setap Shale Formations, and the Miocene sediments which are assigned to the Balingian, Begrih and Liang Formations in the Mukah-Balingian province, and the Belait Formation on Labuan. There is still much debate about the timings or even existence of some important unconformities offshore, such as the Middle Miocene Unconformity (MMU) and Deep Regional Unconformity (DRU). We propose to avoid the ambiguous time-based terminology that has been used for different events by different authors. Instead, our results from the on-land stratigraphy show two main unconformities in northern Sarawak; one at c. 37 Ma (Rajang Unconformity), marking the change from deep marine to fluvial-marginal marine sedimentation, and another one at c. 17 Ma (Nyalau Unconformity) which is related to widespread uplift in Borneo and changing river systems.

Adakites without a slab: Remelting of hydrous basalt in the crust and shallow mantle of Borneo to produce the Miocene Sintang Suite and Bau Suite magmatism of West Sarawak

“…A C C E P T E D M A N U S C R I P T Hutchison (1996) introduced the term Sarawak Orogeny to explain a major tectonic change in NW Borneo in the Late Eocene, to which Prouteau et al (2001) attributed the Sintang Suite magmatism, but recent studies have questioned the implied collisional event (Hall, 2012;Hall and Sevastjanova, 2012;Hall and Breitfeld, 2017;Hennig-Breitfeld et al, 2019). Early tectonic models (e.g.…”

“…2) ceased in the Cretaceous at around 90 to 80 Ma (Williams et al, 1988;Moss, 1998;Hall & Spakman, 2015;Breitfeld et al, 2017;Hennig et al, 2017) although deep marine sedimentation continued until the Late Eocene (Galin et al, 2017;. Between the Late Eocene and Early Miocene, to the west of the West Baram Line, NW Borneo was an elevated region (Hall, 2013;Hennig-Breitfeld et al, 2019), and offshore and onshore Sarawak were extensive coastal and shelf areas (e.g. Hageman, 1987;Madon, 1999;Hassan et al, 2013).…”

A tuffaceous volcaniclastic turbidite bed of Early Miocene age in the Temburong Formation of Labuan, North‐West Borneo and its implications for the Proto‐South China Sea subduction in the Burdigalian

“…However, Wilson and Wong (1964) considered them part of the Belait Formation, a view supported by limited geochemical data (Albaghdady et al, 2003; Gou & Abdullah, 2010) which indicates that the Layang‐Layangan Beds have some geochemical similarities to the Belait Formation. Hennig‐Breitfeld et al (2019) followed this interpretation and informally renamed the Layang‐Layangan Beds the Lower Belait Formation. The end of deep water sedimentation in North‐West Sabah, which coincides with the top of the Temburong Formation, is generally considered to be demarked by the Top Crocker Unconformity (TCU) shown as 25 Ma in Hattum et al (2013) and described as 19–20 Ma by Hall (2013a).…”

Supplemental Material: Fingerprinting sand from Asian rivers to the deep central South China Sea since the Late Miocene

“…Compilation of published detrital zircon U-Pb ages along with sampling information and references from the Upper Miocene to Pleistocene samples in the South China Sea region. Samples are grouped according to their geographic locations, including the Western Foothills and Hengchun Peninsula of Taiwan (Chen et al, 2017;Kirstein et al, 2010;Lan et al, 2016;Zhang et al, 2014;Zhang et al, 2017), the Central Depression of the Qiongdongnan Basin (Cao et al, 2015;Chen et al, 2015;Li et al, 2019;Shao et al, 2018), the Central Depression of the Yinggehai Basin (Cao et al, 2015;Jiang et al, 2015;Wang et al, 2018;Wang et al, 2014;Xie et al, 2016;Yan et al, 2011), the Da Lat Zone of Southeast Vietnam (Hennig et al, 2018), South Palawan (Cao et al, 2020;Suggate et al, 2014;Yan et al, 2018b), and the Miri Zone of Northwest Borneo (Hennig-Breitfeld et al, 2019). Published age data, if available, are filtered with a cutoff criterion of 10% discordance and 10% uncertainty (1).…”

“…Compilation of published detrital zircon U-Pb ages along with sampling information and references from drainage sediments and bedrocks of modern potential provenances surrounding the South China Sea. Samples are grouped into 11 source areas, including West Taiwan (Chen et al, 2019;Deng et al, 2017), Coastal Southeast China (Chen et al, 2019;Xu et al, 2014b;Zhang et al, 2017), Pearl River (He et al, 2020;Liu et al, 2017;Xu et al, 2007;Zhao et al, 2015), Hainan (Cao et al, 2015;Wang et al, 2015;Xu et al, 2014a), Red River (Bodet and Schärer, 2000;Clift et al, 2006;Fyhn et al, 2019;Hoang et al, 2009;Wang et al, 2018), North Palawan (Cao et al, 2020Padrones et al, 2017;Shao et al, 2017;Suggate et al, 2014;Walia et al, 2012), East Vietnam (Fyhn et al, 2019Jonell et al, 2017;Usuki et al, 2013;Wang et al, 2018), Mekong River (Bodet and Schärer, 2000;Clift et al, 2006), Northwest Borneo (Breitfeld and Hall, 2018;Breitfeld et al, 2017;Breitfeld et al, 2020;Galin et al, 2017;Hennig-Breitfeld et al, 2019), Malay Peninsula (Sevastjanova et al, 2011), Southeast Sumatra (Zhang et al, 2019). Published age data, if available, are filtered with a cutoff criterion of  10% discordance and  10% uncertainty (1).…”