Oceanic Plate Breaking Away Beneath Zagros Mountains in Iraq

Oceanic Plate Breaking Away Beneath Zagros Mountains in Iraq
by Robert Schreiber
Berlin, Germany (SPX) Jan 30, 2025

An international team of researchers, led by the University of Gottingen, has uncovered how forces from the Zagros Mountains in Iraq have influenced the deformation of the Earth's surface over the past 20 million years. Their study reveals that deep beneath the surface, the Neotethys oceanic plate, which once lay between the Arabian and Eurasian continents, is breaking away horizontally. The tear is steadily extending from southeastern Turkey to northwestern Iran. This discovery sheds light on how internal planetary processes are driving the evolution of the Earth's surface. The study was published in the journal Solid Earth.

Over millions of years, as two continents converge, the oceanic plate between them is forced to sink beneath the continents. Eventually, the continents collide, and their rocky edges are thrust upward, creating mountain ranges. The colossal weight of these mountains causes the Earth's surface in the surrounding areas to bend downward. This depression fills with sediments washed away from the mountains, forming plains such as Mesopotamia in the Middle East. The research team modeled the deformation of the Earth's surface due to the weight of the Zagros Mountains, which are the result of the ongoing collision between the Arabian and Eurasian plates. Their models, combined with topographic data and mantle characteristics, helped explain the deep depression in the southeastern portion of the study area.

However, the scientists discovered that the mountains alone could not account for the 3-4 km depression that has filled with sediment over the last 15 million years. "Given the moderate topography in the north-western Zagros area, it was surprising to find out that so much sediment has accumulated in the part of the area we studied. This means the depression of the land is greater than could be caused by the load of the Zagros Mountains," said Dr. Renas Koshnaw, lead author and Postdoctoral Researcher at Gottingen University's Department of Structural Geology and Geothermics.

The team suggests that this phenomenon is due to the additional load of the oceanic plate, which is still attached to the Arabian plate. As the plate sinks, it pulls the land downward, creating additional space for sediment accumulation. Towards Turkey, the depression becomes much shallower, implying that the plate has detached in that region, easing the downward pull. "This plate is pulling the region downward from below, making space for more sediment accumulation," Koshnaw explained. "Towards Turkey, the sediment-filled depression becomes much shallower, suggesting that the slab has broken off in this area, relieving the downward pull force."

This research provides a new geodynamic model that can be applied across various fields. "This research contributes to understanding how the Earth's rigid outer shell functions," Koshnaw said. This knowledge could also aid in exploring natural resources such as sedimentary ore deposits and geothermal energy, as well as enhancing earthquake risk assessments.

Research Report:The Miocene subsidence pattern of the NW Zagros foreland basin reflects the southeastward propagating tear of the Neotethys slab