120-Million-Year-Old Tectonic Plate Discovered by Geologists
Geologists at Utrecht University in the Netherlands have uncovered details about a tectonic plate that existed 120 million years ago. The plate, known as the Pontus plate, was estimated to be a quarter of the size of the present-day Pacific Ocean. The discovery was made by Suzanna van de Lagemaat, a graduate geologist, and her supervisor Douwe van Hinsbergen, who pieced together geological data from various sources in the Asia-Pacific region.
Initially, the researchers believed they were studying remnants of a known lost plate. However, further analysis revealed that the rocks they studied in northern Borneo originated from a different, previously unknown plate. Magnetic lab research conducted on the rocks indicated that they were originally from a much farther north location.
According to the researchers’ reconstructions going back 160 million years, the Pontus plate existed during a time when a vast ocean separated Eurasia and Australia, which were then connected to Antarctica as part of the supercontinent Pangaea. Over millions of years, as Pangaea broke apart, the Pontus plate was subsumed by surrounding plates that carried Borneo and the Philippines to their current positions.
The investigation focused on the Junction Region, one of the most complex plate tectonic areas globally, which stretches from Japan to New Zealand. The researchers used published data and data from their own field studies in Borneo to reconstruct the movements of tectonic plates from the time of the dinosaurs until the present day.
Unlike previous reconstructions of the Junction Region, the researchers did not use paleogeomagnetic data, which is the ancient record of Earth’s magnetic field preserved in rocks. Instead, they considered the entire western Pacific region and its predecessor, the Panthalassa superocean. By working backward from the current geological arrangement of tectonic plates, the researchers were able to reconstruct plate movements using the simplest plate tectonic scenario that aligned with geological observations.
The discovery of the Pontus plate confirms a prediction made 11 years ago by Douwe van Hinsbergen and his colleagues based on anomalies in seismic data. Fragments of the plate had previously been found on Palawan Island in the Western Philippines and in the South China Sea, which aligns with the findings from van de Lagemaat’s study in Borneo.
The study, which provides valuable insights into Earth’s ancient tectonic processes, has been published in the journal Gondwana Research.