Geoscientists Confirm Existence of Crustal ‘Drip’ Under Central Anatolian Plateau in Türkiye

Recent satellite data reveal that the Konya Basin on Turkey’s Central Anatolian Plateau has been continuously reshaped for millions of years, according to a new analysis by University of Toronto geologists.

The researchers say the experimental simulations, combined with geological, geophysical and geodetic data, explain the puzzling sinking of the basin into the rising plateau and further suggest a new class of plate tectonics that has implications for other planets that do not have Earth-like plates, such as Mars and Venus.

The study, published in Nature Communicationsshows that the subsidence of the region is due to multi-stage lithospheric dripping, a phenomenon so named because of the instability of the rocky materials that make up the Earth’s crust and upper mantle. As dense rock fragments from below the surface break off and sink into the more fluid layer of the planet’s mantle, major landforms such as basins and crustal folds form on the surface.

“Looking at the satellite data, we saw a circular structure in the Konya Basin, where the crust is subsiding or the basin is deepening,” says lead author Julia Andersen, a PhD candidate in the Department of Earth Sciences in the Faculty of Arts and Science at the University of Toronto. “That prompted us to look at other geophysical data below the surface, where we saw a seismic anomaly in the upper mantle and thickened crust, which tells us that there is high-density material there and indicates likely lithospheric mantle drainage.”

These results echo a similar study by the researchers on the formation of the Arizaro Basin in the Andes in South America, suggesting that the phenomenon can occur anywhere on the planet and explains tectonic processes typically observed in mountainous plateau regions.

Previous studies show that the Central Anatolian Plateau has risen by up to a kilometer over the last 10 million years due to lithospheric drainage.

“As the lithosphere thickened and drained beneath the region, it formed a basin at the surface that then arose as the weight below broke away and sank into deeper depths of the mantle,” said Russell Pysklywec, a professor in the Department of Earth Sciences and co-author of the study.

“We now see that this process is not a one-off tectonic event and that the initial drip appears to have spawned subsequent secondary events elsewhere in the region, leading to the rapid and curious subsidence of the Konya Basin within the ever-rising plateau of Turkey.”

Andersen adds that the new findings suggest a link between shelf uplift and basin-forming events through the evolution of primary and secondary lithospheric removal. “Essentially, subsidence is occurring in parallel with ongoing shelf uplift.”

Andersen and the study’s co-authors, including colleagues from Istanbul Technical University and Çanakkale Onsekiz Mart University in Turkey, reached their conclusions after recreating the dripping process in laboratory experiments and analyzing their observations.

They built laboratory analogue models to establish how the process might have unfolded based on data from the new measurements, filling a plexiglass tank with polydimethylsiloxane (PDMS) – a silicone polymer fluid about 1,000 times thicker than table syrup – to serve as Earth’s fluid lower mantle, adding a mixture of PDMS and modelling clay to replicate the uppermost solid section of the mantle, and finishing with a sand-like layer on top made of ceramic and silica spheres to serve as Earth’s crust.

The researchers activated the model by inserting a high-density seed into the layer of PDMS and modeling clay to initiate a drip that was then pulled down by gravity. A set of cameras was placed above and next to the reservoir to record any changes over time, capturing a high-resolution image approximately every minute.

“Within 10 hours, we observed an initial phase of dripping, which we call primary dripping. After this first drip hit the bottom of the box, we saw that a second drip had started to flow to the bottom after 50 hours,” Andersen says. “Neither the primary drip nor the secondary drip caused horizontal deformation in our artificial crust, which we believe is typically associated with lithospheric dripping of the mantle.”

The researchers already knew that the primary drip caused changes in the surface topography of the experiment and wanted to know if the secondary drip would have an effect on the surface since it was a smaller drip than the primary drip.

“We found that over time, this second flow pulled the crust down and began to create a basin, despite the absence of horizontal movements in the crust at the surface,” Andersen says. “The results show that these major tectonic events are linked, with one lithospheric flow potentially triggering a multitude of other activities deep in the planet’s interior.”