Discovery of ancient star dunes reveals 13,000-year-old mystery

Lala Lalia sand dunes in Erg Chebbi, Morocco. Credit: Professor C Bristow

A breakthrough study reveals the age of stellar dunes and the speed of their formation, providing insight into Earth's geological past.

Scientists have solved the mystery of the mysterious absence of star-shaped sand dunes from Earth's geological history for the first time, dating back thousands of years.

The study, conducted by academics from Aberystwyth University, Birkbeck University and University College London, is the first of its kind to date into how long it took sand dunes to form and examine their internal structure.

Star dunes are huge sand dunes that owe their name to arms extending from a central peak. These sand pyramids, which look like stars when viewed from above, are widespread in modern deserts, including the sand seas of Africa, the Arabian Peninsula, China and North America.

Ancient sand dunes and rapid formation

Research reveals that the oldest parts of the base of the Moroccan dunes are 13 thousand years old. However, the discovery that they formed quickly in the past thousand years surprised scientists who had thought the larger dunes were much older.

They are believed to be the tallest sand dunes on Earth – one in the Badin Jaran Desert in China reaches 300 meters high – and they are also found elsewhere in the solar system, including… Mars and on SaturnTitan's moon.

Although common today, star dunes have never been found in the geological record. Their absence has puzzled scientists because past deserts were a common part of Earth's history, preserved in rocks deep underground.

Lala lala dune map

Satellite image of the Lala Lallia star dunes from Google Earth 2023 Maxar Technologies with dune tops marked by dashed lines, GPR profiles as solid lines, and numbered circles indicating sample locations. Credit: Scientific Reports, DOI: 10.1038/s41598-024-53485-3

Published in the magazine Scientific reportsThe new study dated the foundations of the stellar sand dunes in southeastern Morocco known as Lala Lalia, which means “highest sacred point” in the Berber language, to about 13,000 years ago.

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The sand dunes are located in the Erg Chebbi region of the Sahara Desert near the border with Algeria, an area featured in TV series such as SAS Rogue Heroes and blockbuster films such as The mummy And the desert.

Geological importance and technological progress

Research shows that the sand pyramid reached its current height of 100 meters and width of 700 meters due to rapid growth in the past thousand years as it slowly shifted westward.

Professor Geoff Dowler, from the Department of Geography and Earth Sciences at Aberystwyth University, said:

“This research is actually the case of lost sand dunes – it has been a mystery why we haven't been able to see them in the geological record. Only because of new technology can we now begin to uncover their secrets.

“These results will likely surprise a lot of people as we can see how quickly these enormous sand dunes form, and that they are moving across the desert at a speed of about 50 cm per year. These magnificent star dunes are one of the natural wonders of the world.”

Professor Charlie Bristow, from Birkbeck and University College London, added:

“Using ground-penetrating radar to look inside this stellar dune has allowed us to show how these massive dunes formed, and develop a new model so geologists better know what to look for in the rock record to identify these amazing desert features.”

Advanced research by scientists suggests that the star dunes formed around the same time as the Younger Dryas event, a sudden cooling period in Earth's history. It also reveals that the dunes stopped growing for 8,000 years.

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Pottery found at the site also indicates wetter conditions, and perhaps an expanding monsoon, that stabilized the dunes before the onset of the Great Drought.

The study used fluorescence dating techniques developed at Aberystwyth University to discover the last time minerals in the sand were exposed to sunlight to determine their age.

Professor Dowler, from Aberystwyth University, added:

“It is a great privilege to think that the fluorescence dating techniques developed here at Aberystwyth are revealing some of the secrets of the world's most challenging climates. They are giving us an insight into geology that could have wider implications including geological deposits that are used for water resources and carbon storage.

Professor Dowler's latest discovery uses the same luminescent dating technique he used to discover the world's oldest wooden structure – research published in the journal nature last year.

Reference: “Structure and chronology of star dunes at Erg Chebbi, Morocco, reveals why star dunes are rarely recognized in the rock record” by CS Bristow and GAT Duller, 4 March 2024, Scientific reports.
doi: 10.1038/s41598-024-53485-3

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