The island of Palawan, the most westerly island of the Philippine Archipelago, lies approximately 400 km to the northeast of northern Borneo along the southern margin of the South China Sea. On a broad scale, these two areas — northern Borneo and Palawan — share many geological and physiographic characteristics.
Geologically, both areas are underlain by a complex basement of continental rocks overthrust by Mesozoic ophiolitic rocks that are intruded by young granitic plutons: the Late Miocene Mt Kinabalu pluton of northern Borneo and the Mt Capoas intrusion of Palawan. Physiographically, both onshore regions share a strong NE-SW orientation, are flanked to the west by significant bathymetric troughs and, in turn, by bathymetric highs.
These shared geological and physiographic characteristics result from a common tectonic history that is linked to the opening of the South China Sea during the Early Cenozoic. Tectonic activity in northern Borneo culminated in the Early Miocene Sabah Orogeny, when continental fragments rifted from the South China margin and collided with the existing land mass. A similar scenario has been proposed for Palawan – material rifted from the South China margin is suggested to have collided with the Cagayan Ridge Arc in the Middle Miocene. Northern Borneo is known to have experienced significant uplift and erosion during the Miocene and Pliocene. It is suggested that this event is of regional significance and that widespread uplift and erosion at this time created a large emergent landmass that encompassed both northern Borneo and Palawan.
Regional Tectonic Setting
The Philippine archipelago lies within a complex tectonic region at the boundary between the Eurasian, Philippine Sea and Indo-Australian plates. The area is characterised by active subduction, island arc volcanism, strike-slip faulting and the accretion of continental and oceanic fragments. One of the most unusual geological regions within the Philippines is the island of Palawan, which differs significantly from the rest of the Philippine island arc system.
Palawan is widely interpreted as a fragment of continental crust derived from the South China margin that rifted away during opening of the South China Sea. As a result, the island preserves a geological history that contrasts with the predominantly volcanic and oceanic rocks of the Philippine island arc. Understanding the origin and evolution of Palawan therefore, provides important insights into the tectonic development of Southeast Asia, particularly the interaction between the South China Sea, northern Borneo and the Philippine island arc system.
Our Previous Research in the Philippines:
Magmatism and Thermal History
One important focus of research has been the study of granitic intrusions within northern Palawan. The Capoas intrusion provides a rare opportunity to investigate the age, origin and thermal history of a single intrusive body using multiple geochronological and thermochronological techniques.
The mineral assemblages within the intrusion allow precise dating using methods such as U–Pb zircon geochronology, ^40Ar/^39Ar dating of mica and feldspar, and (U–Th)/He thermochronology. By combining these techniques it is possible to reconstruct the cooling history of the intrusion and determine the timing of magmatism and subsequent uplift.
These data help address key questions about the tectonic evolution of Palawan, including whether the intrusion formed during a single magmatic event or multiple pulses, and whether it records regional extension or uplift during the Neogene. The thermal history may also reveal whether Palawan experienced significant exhumation during the Late Miocene and Pliocene, similar to patterns observed in northern Borneo.
Sedimentary Provenance and Regional Sediment Pathways
Another area of research has focused on the provenance of sedimentary rocks exposed in Palawan and their relationship to surrounding regions.
Very little is currently known about the sources of sediments within the Palawan stratigraphic succession. Provenance studies aim to determine whether these sediments record erosion of continental crust derived from the South China margin or reflect more local sources within Palawan itself.
Heavy mineral analysis, detrital zircon geochronology and compositional studies of minerals such as garnet are used to identify sediment sources and reconstruct sediment transport pathways. These methods help determine whether metamorphic and granitic rocks of the Palawan microcontinental block contributed sediment to surrounding regions.
Connections with Northern Borneo
Provenance studies of Palawan sediments also have important implications for understanding sediment supply to neighbouring regions, particularly northern Borneo.
Recent work suggests that Palawan may have acted as a major sediment source during the Early Miocene. If confirmed, this would imply significant erosion of the Palawan microcontinental block and transport of sediment into nearby basins of northern Borneo.
Comparing mineral assemblages and zircon age populations between Palawan and Borneo sandstones allows researchers to test whether young sedimentary rocks in Borneo were derived from Palawan’s granitic and metamorphic rocks. These results help reconstruct palaeodrainage systems and improve understanding of tectonic connections between the South China margin and Borneo during the Cenozoic.
Regional Significance
Research in Palawan provides important insights into the tectonic evolution of the Philippine region and its relationship to the South China Sea and northern Borneo. Because Palawan represents a fragment of continental crust within an otherwise volcanic island arc system, it preserves a unique geological record of rifting, magmatism and sediment dispersal.
By combining studies of magmatic intrusions, thermochronology and sediment provenance, these projects aim to reconstruct the uplift history of Palawan and its role within the broader tectonic evolution of Southeast Asia. This work also helps clarify sediment pathways between continental fragments and neighbouring sedimentary basins during the Cenozoic.
Southeast Asia Research Group 
