The study, led by U-M archaeologist Geoff Emberling, geomorphologist Jan Peeters and El-Hassan Ahmed Mohammed, who along with Emberling directs the Jebel Barkal Archaeological Project, is published in the Proceedings of the National Academy of Sciences. The Napata site is one of The Klinsky Expeditions, a series of five archaeological field projects funded by U-M alum Steve Klinsky.

"Scholars have looked at the association between changes in climate and local environment and their impact on societies, including their political development and economic systems," said Emberling, a research scientist at the U-M Kelsey Museum of Archaeology. "But this hasn't been done in Sudan, and we've missed a key tool to help us not only understand the rise and fall of individual settlements, but also the broader history of the rise and fall of the Empire of Kush. This is really the first systematic geomorphological study in Sudan that relates to these ancient cultures."

Kush was an important player in the ancient world, Emberling said. The empire was mentioned in the Bible, by the Greek historian Herodotus, and interacted with Egypt, the Assyrians, Greeks, Persians and with the Roman Empire. After the Egyptian empire collapsed at around 1200 BCE, the Kushite dynasty came into power, based at what's now called Jebel Barkal, whose ancient name was Napata. There, at the foot of an ancient sandstone outcrop, the Kushites built palaces, pyramids and temples. Now, Jebel Barkal is a UNESCO World Heritage Site.

"They were part of that whole world system, yet because of a history of relatively lower investment in research in Sudan, some very basic questions haven't been addressed," Emberling said. "We might think we know all we need to know about the Nile because there's been a fair amount of research in Egypt. But in Sudan, the way the Nile works is different."

The gentling of the Nile

In Sudan, the geology of the region creates rapids, waterfalls and islands along the Nile that disrupt travel and fragment settlements, according to Emberling. To understand the geology underlying Jebel Barkal, Peeters led a research team including a group of local Sudanese that drilled 26 sediment cores across the river valley in which the city is situated.

The team collected samples every 10 centimeters, with the boreholes eventually reaching between five and 13 meters deep. Using a technique called optically stimulated luminescence dating, which dates samples by determining the last time sand grains were exposed to light, the researchers were able to peer into 12,500 years of Nile history.

Dr. Liz Chamberlain from Wageningen University & Research explains this unique technique: “ Cultural activity can often be well dated with radiocarbon, because people leave behind a lot of organic material such as animal bones, plant seeds and fibers, and even human remains. But river landscapes are made mostly of sand and mud, often lacking suitable organic materials for dating. Luminescence dating is the ideal tool for anchoring established cultural activity to landscape development, because it directly dates the sand and mud that form the landscape. In this study we used luminescence dating to determine how the Nile River changed over time, and how the archaeology connects to the geology at Napata. “


For the first 8,000 years of this period, the Nile carved its own valley, according to geomorphologist Peeters. Then, about 4,000 years ago, the valley leveled out, allowing the river to start depositing sediment and building up the valley floor. From that time period on, the river has been relatively stable—composing a layer of fertile clay and silt about 10 meters thick.

The researchers say another geologic feature, the Nile's Fourth Cataract, also helped the river slow and allowed it to drop sediment at the site where Napata would eventually thrive. The cataracts of the Nile are stretches of islands and fast-moving rapids. The Fourth Cataract lies just upstream of Jebel Barkal, and Peeters surmises that much of the river's energy dissipates over the stretch of this cataract, allowing the river to deposit sediment and become relatively stable for 4,000 years.

"Where sediments accumulate shapes where people can live, farm, and carry out cultural and religious practices,” Peeters said.

The precarity of war

The researchers say this work is ongoing, even as Sudan experiences its current war. Sudanese archaeologists, members of Sudan’s antiquities department, known as the National Corporation for Antiquities and Museums, have been carrying out work at Jebel Barkal, guided by Emberling and others abroad.

"Despite all the difficulties and hardship of Sudan, because of the ongoing war, research is continuing through the efforts of our local collaborators," Peeters said. "Their work is central to the project, which places strong emphasis on community engagement and collaboration with Sudanese researchers."