Tracing the 'Green Sahara' in Chad's northern desert

Kneeling, armed with a brush and trowel inside the largest rock shelter at the Gaora Hallagana site in the Ennedi West province, Djimet Guemona, 35, meticulously removed every layer of sand.

"It's as if we are turning the pages of a historic book to travel back in time," said Guemona, an archaeologist at the National Center for Research and Development.

His face lit up at the discovery of each fragment of pottery or scrap of charcoal.

The scientific mission, conducted over five days in late July some 30 kilometers (nearly 19 miles) from Fada, the main town in Ennedi West, brought together Chadian and geologists from universities in N'Djamena and Abeche.

It aimed to lay "the first cornerstone" of the chronological framework for ancient settlements in Ennedi, Guemona said.

The Natural and Cultural Reserve of Ennedi (RNCE) was created in 2018 in the Chadian province, which stands at the crossroads with Libya and Sudan and is home to a rich archaeological heritage.

Tens of thousands of engravings and paintings can be found on the rocky walls across the vast reserve's more than 50,000 square kilometers (19,305 square miles).

Since the RNCE was included on the UNESCO World Heritage list in 2016, the Chadian government brought in the South African organization, African Parks, to help run it for 15 years.

The Natural and Cultural Reserve of Ennedi in Chad is home to a rich archaeological heritage.

Archaeologists use a mobile phone application that helps to better detect the pigments in cave paintings.

The Chadian government brought in the South African organisation African Parks to help run the reserve for 15 years.

Frederique Duquesnoy, 61, an archaeologist, joked the Chadian site was 'Lascaux times 100,000', referring to the famous ancient caves in southwest France.

The Chadian authorities are drafting a tourist development plan.

Tens of thousands of engravings and paintings can be found on the rocky walls across the vast reserve.