Beneath the deserts of Saudi Arabia lies a hidden record of Earth’s earliest continental history — a geological archive that could reshape our understanding of how Arabia was born.

How and when did the foundations of the Arabian continent form? A new study has traced the geological history of the Ha’il region in northern Saudi Arabia back more than 640 million years, to a time when Arabia was still welded to the supercontinent Gondwanaarticle " id="return-reference-1" href="https://discovery.kaust.edu.sa/en/article/26122/unearthing-arabias-ancient-foundations-new-insights-from-the-hail-terrane/#reference-1">[1]. By analyzing ancient rocks buried beneath the desert, researchers at KAUST have uncovered critical new evidence of how this landmass evolved during one of Earth’s most dynamic tectonic transitions.

The Ha’il terrane, which is the focus of the study, is one of the crustal blocks that make up the Arabian Shield — a vast expanse of exposed Precambrian rock in western Saudi Arabia. Using advanced zircon U-Pb isotope dating and geochemical analysis, researchers traced the formation of rocks within the terrane during a dramatic geological transition that occurred between approximately 650 and 640 million years ago. 

The results show that the Ha’il terrane first experienced intense mountain-building as microcrustal tectonic plates collided, followed by a shift to crustal stretching and magma intrusion. This transition coincided with the final stages of Gondwana’s assembly, when Arabia fused with Africa and India to form one of Earth’s great supercontinents. 

“The rocks of the Ha’il terrane are like a time capsule,” says Om Prakash Pandey, the study’s lead author. “They capture the shift from a world of colliding continents to one where the crust began to relax and evolve into the stable platform we see today.” 

Read more at KAUST Discovery.