Tectonic History of the Philippines Region
A Brief Introduction to a Not-So-Brief Topic
Despite the complexity of the tectonic configuration of the Philippines region, workers have developed models for past configurations of the region. Here, an animated reconstruction of the tectonics for all of South East Asia is provided, from Hall (2002). This section will outline Hall’s (2002) model of the Philippines region, in addition to studies by other workers.
Hall (2002) identifies three key periods for tectonics in the broad area of SE Asia. These events include the collision between India and Asia, the collision of the New Guinea passive margin with the East Philippines, and a regime change not well-understood, but possibly related to the arc-collision transition west of Taiwan, or the motion of the Pacific Plate. Despite this model’s drastic simplification of the forces and processes over the last 50 Ma, it provides useful insight into the plausible mechanisms that gives rise to the current configuration in the Philippines region. However, some workers have attempted to constrain paleo-tectonics even earlier in Earth's history. Li (1998) explores the plausible origins of the blocks and plates observed in East Asia through tectonostratigraphic analyses as far back as the mid-Proterozoic. These interpretations will also be explored in this section.
Despite the complexity of the tectonic configuration of the Philippines region, workers have developed models for past configurations of the region. Here, an animated reconstruction of the tectonics for all of South East Asia is provided, from Hall (2002). This section will outline Hall’s (2002) model of the Philippines region, in addition to studies by other workers.
Hall (2002) identifies three key periods for tectonics in the broad area of SE Asia. These events include the collision between India and Asia, the collision of the New Guinea passive margin with the East Philippines, and a regime change not well-understood, but possibly related to the arc-collision transition west of Taiwan, or the motion of the Pacific Plate. Despite this model’s drastic simplification of the forces and processes over the last 50 Ma, it provides useful insight into the plausible mechanisms that gives rise to the current configuration in the Philippines region. However, some workers have attempted to constrain paleo-tectonics even earlier in Earth's history. Li (1998) explores the plausible origins of the blocks and plates observed in East Asia through tectonostratigraphic analyses as far back as the mid-Proterozoic. These interpretations will also be explored in this section.
In the Beginning…
In order to have tectonics, you must first have plates. The onset of the Earth’s tectonic cycle is still a matter of debate amongs earth scientists. In the Archean Eon (4.0 Ga – 2.5 Ga), the Earth already had developed rigid plates (Van Hunen & Moyen, 2012). However, elevated mantle temperatures and hotter, (rheologically-speaking) weaker plates may have prevented the onset of early subduction (Van Hunen & Moyen, 2012). Furthermore, the Earth’s paleogeography in the Archean is not well known, nor is the true onset of subduction as it is observed today. The limited information available for this period means the history of the Philippines’ tectonics can only start being told later in time.
In order to have tectonics, you must first have plates. The onset of the Earth’s tectonic cycle is still a matter of debate amongs earth scientists. In the Archean Eon (4.0 Ga – 2.5 Ga), the Earth already had developed rigid plates (Van Hunen & Moyen, 2012). However, elevated mantle temperatures and hotter, (rheologically-speaking) weaker plates may have prevented the onset of early subduction (Van Hunen & Moyen, 2012). Furthermore, the Earth’s paleogeography in the Archean is not well known, nor is the true onset of subduction as it is observed today. The limited information available for this period means the history of the Philippines’ tectonics can only start being told later in time.
The End of a Supercontinent
Tectonostratigraphic and paleomagnetic evidence synthesized by Li (1998) gives some of the earliest clues to the origin of components of East Asia’s tectonic configuration. To the north of the modern Philippines, the North China Block (NCB) is defined, comprised of Archean cratonic cores and 1800 Ma orogenic belts. Below that lies the South China Block (SCB), which is broadly composed of Precambrian continental blocks including the Yangtze Block and the Cathaysia Block. Li (1998) suggests that, in the mid-Proterozoic, the NCB was grouped with other large continental masses, like Laurentia and Siberia. These components would have been part of Rodinia, the super continent that formed around approximately 1 Ga, and broke apart around 0.8 Ga. This configuration is illustrated by Li (1998) in Figure 1. During the rifting of Rodinia, the SCB migrated northward and became a continental island, while the NCB broke away from Laurentia. From then, there is a period of relative tectonic quiescence until the start of the Paleozoic era. Around this time, a new dataset provides evidence for the proximity: fossil correlation (Li, 1998). The presence of comparable geneses of trilobites on the NCB and SCB blocks and the Siberian craton gives evidence for their proximity to the eventual supercontinent Gondwanaland, but tectonostratigraphic evidence suggests that these two blocks did not collide with that supercontinent (Li, 1998). This is illustrated by Li (1998) in Figure 2. It can be seen that both blocks maintain proximity to Gondwanaland for a significant period of time, as well as Pangea following the collision of Laurussia with Gondwana. |
Following this, in the Late Permian, geologic evidence (including zircon dating, geothermobarometry on greenschist facies rocks, and a transgressive marine sedimentary facies distribution) suggests that continental-continental collision between the blocks and the Mongolian Terranes began (Li, 1998). However, it wasn’t until the Triassic-Jurassic period that the NCB and the SCB became connected, following the closure of a remnant sea. This occurred by a two-step process, including collision on the Sulu Orogen, and later suturing of this orogenic belt with the Qinling-Dabie orogenic belt. By the Early Cretaceous, the NCB and SCB were fully sutured to Eurasia whilst the Tethys Sea grew from the mid ocean ridges to south of Eurasia (Li, 1998). This is shown in Figure 3. This broadly sets the stage for the collision of India with Eurasia (i.e. the onset of escape tectonics) as well as the Cenozoic tectonic modelling proposed by Hall (2002). |
Above is the animated version of the reconstruction of the tectonics of SE Asia for the last 55 Ma, from Hall (2002).
The Cenozoic: A Tale of Many Plates
Hall (2002) has developed a reconstruction of over 55 Ma of tectonic history using computer-generated models that generate conditions which are consistent with observed paleomagnetic data, geochronological data (from both metamorphic and igneous sources), and approximately 120 "fragments" which are allowed motion. Hall (2002) notes that not all plate motions are equally well constrained, and there is still significant need for improvement of the tectonic history through geologic mapping and quantitative analysis. For example, even contemporary motions of the PSP are not well constrained since it is entirely rimmed by subduction zones, and thus not intimately linked with global plate models (Hall, 2002). However, the model provided gives an important first-order insight into how the regional tectonic configuration evolved. What follows is a brief summary of the model put forward by Hall (2002), highlighting the key points relevant for the region of study in this project.
Hall (2002) has developed a reconstruction of over 55 Ma of tectonic history using computer-generated models that generate conditions which are consistent with observed paleomagnetic data, geochronological data (from both metamorphic and igneous sources), and approximately 120 "fragments" which are allowed motion. Hall (2002) notes that not all plate motions are equally well constrained, and there is still significant need for improvement of the tectonic history through geologic mapping and quantitative analysis. For example, even contemporary motions of the PSP are not well constrained since it is entirely rimmed by subduction zones, and thus not intimately linked with global plate models (Hall, 2002). However, the model provided gives an important first-order insight into how the regional tectonic configuration evolved. What follows is a brief summary of the model put forward by Hall (2002), highlighting the key points relevant for the region of study in this project.
The first "big shift" 45 Ma...
Around this time interval, the spreading center between Australia and India becomes defunct, essentially allowing the continents to become part of one plate. This plate continues its northward migration. The PSP underwent significant rotation over the first 10 Ma of the simulation, and arc systems begin to develop along its eastern margin. The South China Sea Basin is hypothesized to have started its subduction beneath the Luzon region at this time. To the east, the overriding of the PSP atop the subducting Pacific Plate slab may have led to the development of the Caroline Sea. |
25 Ma...
Hall (2002) regards this interval as key in understanding the Cenozoic evolution of SE Asia. This is argued on the basis of the merging of the Caroline Arc with the two Philippine (East & West). This changed the PSP to an intra-oceanic subduction zone. The cause of this, while relatively uncertain, could be a result of the collision of the southern arcs with northern New Guinea's margin. Australia's migration thus stopped, and the stress was then accommodated by a large scale strike-slip system. |
5 ma...
This period was marked by many speculated significant events, such as the pull-apart basin formation of the Bismark Sea (attributed to the position of the Manus plume). It was at this time that rifting (and subsequently, spreading) began along the Mariana Trough. This is attributed to the differential motions of the Caroline Sea Plate and the PSP. Furthermore, subduction beneath the Philippine accreted terrane on its west margin began in the opposing direction, leading to the onset of subduction of the South China Sea. |
The Present Day
The key changes from 5 Ma to the present observed configuration include the formation of the Okinawa Trough (from the subduction of the PSP), the collision of Eurasia's continental margin with Taiwan (continental-arc collision), and continued spreading at the Mariana Trough.
Below is the present geometry of the tectonic plates. Their relative motions are explored in more detail on the page General Tectonics.
The key changes from 5 Ma to the present observed configuration include the formation of the Okinawa Trough (from the subduction of the PSP), the collision of Eurasia's continental margin with Taiwan (continental-arc collision), and continued spreading at the Mariana Trough.
Below is the present geometry of the tectonic plates. Their relative motions are explored in more detail on the page General Tectonics.
References Cited
Hall, R.H. (2002). Cenozoic geological and plate tectonic evolution of SE Asia and the SW Pacific: computer-based reconstructions, model and animations. Journal of Asian Earth Sciences. V. 20. Pp. 353 - 431.
Li, Z.X. (1998). Tectonic History of the Major East Asian Lithospheric Blocks Since the Mid-Proterozoic- A Synthesis. American Geophysical Union: Geodynamics. V. 27. Pp. 221 - 243.
North Western University. Accessed at: http://www.earth.northwestern.edu/people/seth/Export/midcontinent/rodinia.pdf Accessed: April 3, 2017.
Van Hunen, J., Moyen, J-F. (2012) Archean Subduction: Fact or Fiction? Annu. Rev. Earth Planet. Sci. V. 40. Pp. 195-219. Doi: 10.1146/annurev-earth-042711-105255.
Hall, R.H. (2002). Cenozoic geological and plate tectonic evolution of SE Asia and the SW Pacific: computer-based reconstructions, model and animations. Journal of Asian Earth Sciences. V. 20. Pp. 353 - 431.
Li, Z.X. (1998). Tectonic History of the Major East Asian Lithospheric Blocks Since the Mid-Proterozoic- A Synthesis. American Geophysical Union: Geodynamics. V. 27. Pp. 221 - 243.
North Western University. Accessed at: http://www.earth.northwestern.edu/people/seth/Export/midcontinent/rodinia.pdf Accessed: April 3, 2017.
Van Hunen, J., Moyen, J-F. (2012) Archean Subduction: Fact or Fiction? Annu. Rev. Earth Planet. Sci. V. 40. Pp. 195-219. Doi: 10.1146/annurev-earth-042711-105255.