Scientists have finally solved the mysterious absence of star-shaped sand dunes in the geological record of Earth’s history, managing to date one of these dunes back thousands of years. This study, conducted by scholars from the universities of Aberystwyth, Birkbeck, and UCL, is the first to pinpoint just how long it took for a stellar dune to form and to examine its internal structure.

Star dunes, as their name suggests, are enormous sand dunes that owe their striking appearance to the arms radiating outward from a central peak, resembling a star when viewed from above.

These towering pyramids of sand are a common sight in modern deserts, gracing the sandy expanses of Africa, Arabia, China, and North America. Surprisingly, despite their prevalence today, star dunes have rarely been found in the geological record, leaving scientists puzzled as to why these desert features from the past have seemingly vanished from the rock record.

The research, published in the journal Scientific Reports, has dated the foundations of a star dune in southeastern Morocco, known as Lala Lallia (meaning “highest sacred point” in the Berber language), to around 13,000 years ago. This dune, located in the Erg Chebbi region of the Sahara Desert near the Algerian border, has even graced the screens of television shows like “SAS: Who Dares Wins” and blockbuster movies such as “The Mummy” and “Sahara”.

The study reveals that this colossal sand pyramid, now standing at 100 meters tall and 700 meters wide, achieved its impressive size through rapid growth over the past 1,000 years as it slowly migrated westward. Professor Geoff Duller, from Aberystwyth University’s Department of Geography and Earth Sciences, expressed his amazement, stating, These findings will probably surprise many people, as we can see how rapidly this enormous dune formed and that it moves across the desert at a rate of about 50 cm per year. These fantastic star dunes are one of the natural wonders of the world.

The researchers utilized ground-penetrating radar to peer into the dune’s interior, allowing them to develop a new model for geologists to better identify these remarkable desert features in the rock record. Professor Charlie Bristow, from Birkbeck and UCL, added, Using ground-penetrating radar to look inside this star dune has allowed us to show how these immense dunes form and develop a new model for geologists to know better what to look for in the rock record to identify these amazing desert features.

Intriguingly, the star dune’s formation coincides with the Younger Dryas, a period of abrupt cooling in Earth’s history. The study also reveals that the dune stopped growing for 8,000 years, with pottery found at the site suggesting wetter conditions, perhaps an expanded monsoon, which stabilized the dune before the onset of a prolonged drought.

The researchers employed luminescence dating techniques developed at Aberystwyth University to determine when the sand minerals were last exposed to sunlight, unveiling their age. Professor Duller expressed pride, stating, It’s a privilege to think that the luminescence dating techniques developed here in Aberystwyth are revealing some of the secrets of the world’s harshest climates. They’re giving us insights into geology that could have wider implications, including for geological deposits used for water resources and carbon storage.

This groundbreaking discovery by Professor Duller utilizes the same luminescence dating technique he employed to uncover the world’s oldest wooden structure, research published in the prestigious journal Nature just last year.


Sources

Aberystwyth University | Bristow, C.S., Duller, G.A.T. Structure and chronology of a star dune at Erg Chebbi, Morocco, reveals why star dunes are rarely recognised in the rock record. Sci Rep 14, 4464 (2024). doi.org/10.1038/s41598-024-53485-3


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