Geologist unexpectedly finds remains of a lost mega-plate


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The Pontus oceanic plate as reconstructed by Susanna van de Lagemaet: its location in the paleo-Pacific Ocean 120 million years ago, and its present-day remains. An earlier study suggested that a large subduction zone may have passed through the western Paleo-Pacific Ocean, separating the known Pacific plates in the east from a hypothetical Pontus plate in the west. This hypothesis has now been independently demonstrated by the research of Van de Lagemaet. Credit: Susanna van de Lagemaat, Utrecht University

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The Pontus oceanic plate as reconstructed by Susanna van de Lagemaet: its location in the paleo-Pacific Ocean 120 million years ago, and its present-day remains. An earlier study suggested that a large subduction zone may have passed through the western Paleo-Pacific Ocean, separating the known Pacific plates in the east from a hypothetical Pontus plate in the west. This hypothesis has now been independently demonstrated by the research of Van de Lagemaet. Credit: Susanna van de Lagemaat, Utrecht University

Geologist Susanna van de Lagemaat of Utrecht University has reconstructed a vast and previously unknown tectonic plate that was once one-quarter the size of the Pacific Ocean. His colleagues in Utrecht predicted its existence 10 years ago based on fragments of old tectonic plates found deep in the Earth. Van de Lagemaat reconstructed the lost plates through field research and detailed examination of the mountain belts of Japan, Borneo, the Philippines, New Guinea and New Zealand.

To his surprise, he discovered that the marine remains on northern Borneo belonged to a long-suspected plate, which scientists have named Pontus. He has now recreated the entire plate in its full glory. The work has been published gondwana research,

Understanding the movements of the tectonic plates that form Earth’s hard outer shell is essential to understanding the geological history of the planet. The movements of these plates strongly influence how the planet’s paleogeography and climate have changed over time, and even where rare metals are found. But large oceanic plates from the geological past have disappeared into the Earth’s mantle through subduction. They have left behind only fragments of rock hidden in the mountain ranges.

Van de Lagemaet studied the planet’s most complex plate tectonic region: the region around the Philippines. “The Philippines lies at a complex junction of different plate systems. The region is composed almost entirely of oceanic crust, but some fragments are raised above sea level, and show rocks of very different ages.”


Geologist Susanna van de Lagemaat of Utrecht University has reconstructed a giant and previously unknown tectonic plate that was once one-quarter the size of the Pacific Ocean. His colleagues in Utrecht had predicted the plate’s existence years earlier, based on fragments of old tectonic plates found deep in the Earth. Van de Lagemaat reconstructed the lost plates through field research and detailed examination of the mountains of Japan, Borneo, the Philippines, New Guinea and New Zealand. He was surprised to discover that the marine remains on northern Borneo belonged to a long-suspected plate, which scientists have named Pontus. He has now recreated the entire plate in its full glory. Credit: Susanna van de Lagemaat/Utrecht University

Reconstruction

Using geological data, Van de Lagemaat was the first to reconstruct the movements of present-day plates in the area between Japan and New Zealand. This showed how large was the area of ​​plates that would have disappeared into the present-day western Pacific.

“We also did field work on northern Borneo, where we found the most important piece of the puzzle. We thought we were dealing with the remains of a lost plate that we already knew about. But those rocks in our magnetic laboratory Research indicated that our finds were originally from much further north, and should have been the remains of a different, previously unknown plate.”

But the important realization was yet to come. “11 years ago, we thought the remains of Pontus might be in northern Japan, but we have refuted that theory,” said Van de Lagemaat, a Ph.D. Douwe Van Hinsbergen explains. Supervisor. “It was only after Susanna had systematically reconstructed half of the ‘Ring of Fire’ mountain belt from Japan through New Guinea to New Zealand that the proposed Pontus Plate was discovered, and it included the rocks we have seen on Borneo. had studied.”

remains and waves

The remains of Pontus are located not only in northern Borneo, but also in Palawan, an island in the western Philippines, and in the South China Sea. Van de Lagemaat’s research also revealed that a coherent plate tectonic system extended from southern Japan to New Zealand, and that it may have existed for at least 150 million years. This is also a new discovery in this field.

Previous predictions of Pontus’s existence were possible because when a subducted plate ‘sinks’ into the Earth’s mantle it leaves scars: areas of unusual temperature or composition in the mantle. These anomalies can be seen when seismometers capture signals from earthquakes.

Earthquakes send waves through the Earth’s interior, and when they travel through an anomaly, such as a piece of an old plate, the anomaly interferes with the signal. Geologists can trace these disruptions to the existence of events in the mantle, such as fragments of tectonic plates. This allows them to look 300 million years into the past; Fragments of the old plate have ‘disintegrated’ at the boundary between the mantle and the core.

A study 11 years ago suggested that a large subduction zone may have passed through the western Paleo-Pacific Ocean, separating the known Pacific plates in the east from the hypothetical Pontus Plate in the west. This hypothesis has now been independently demonstrated by the research of Van de Lagemaet.

more information:
Susanna HA van de Lagemaat et al, Plate tectonic cross-roads: reconstruction of the Panthalassa-Neotethys junction zone from the Philippine Sea Plate and Australian oceans and orogens, gondwana research (2023). DOI: 10.1016/j.gr.2023.09.013

Journal Information:
gondwana research


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