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Pyramids packed with fossil shells

Many of Egypt's most famous monuments, such as the Sphinx and Cheops pyramid at Giza, contain hundreds of thousands of marine fossils, according to a new study.

Most of the fossils are intact and preserved in the monument walls, giving clues to how the monuments were built.

The authors suggest the stones that make up the Giza plateau, Fayum and Abydos monuments must have been carved out of natural stone as they reveal what chunks of the sea floor must have looked like over 4000 years ago, when the buildings were erected.

"The observed random emplacement and strictly homogenous distribution of the fossil shells within the whole rock is in harmony with their initial in situ setting in a fluidal sea bottom environment," write Professor Ioannis Liritzis and his colleagues from the University of the Aegean and the University of Athens.

The researchers analysed the mineralogy, as well as the chemical makeup and structure, of small material samples chiselled from the Sphinx Temple; the Osirion Shaft; the Valley Temple; the Cheops, Khefren and Menkaure pyramids at Giza; Osirion at Abydos; the Temple of Seti I at Abydos; and Qasr el-Sagha at Fayum.

X-ray diffraction and radioactivity measurements, which can penetrate solid materials to help illuminate their composition, were carried out.

Granite, sandstone, limestone

The analysis determined the primary building materials were pinky granites, black and white granites, sandstones and various types of limestones.

The latter contained numerous shell fossils of the genus Nummulites, simple marine organisms whose name means 'little coins'.

"[At Cheops alone they constituted] a proportion of up to 40% of the whole building stone rock," the researchers write in the latest issue of the Journal of Cultural Heritage.

Nummulites that lived during the Eocene period around 55.8-33.9 million years ago are most commonly found in Egyptian limestone.

Fossils have also been unearthed at other sites, such as in Turkey and throughout the Mediterranean.

When nummulites are bisected horizontally they appears as a perfect spiral. Since they were common in ancient Egypt, it's believed the shells were used as coins, perhaps explaining their name.

Fossils of their ancient marine relatives - sand dollars, starfish and sea urchins - were also detected in the Egyptian limestone.

Intact fossils throughout the stone

The fossils are largely undamaged and are distributed in a random manner within the stone, in accordance with their typical distribution at sea floors.

So, Liritzis and his team argue that the large building stones used to construct the monuments must have been carved out of natural stone instead of cast in moulds.

To further their argument, the scientists say the x-ray patterns detect no presence of lime, which would be expected along with the salt natron, which would indicate cast materials.

They also point out there are no references of moulds, buckets or other casting tools in early Egyptian paintings, sculptures or texts.

Carved or cast?

Joseph Davidovits, professor and director of France's Geopolymer Institute, formulated the theory that natural limestone was cast like concrete to build the pyramids.

Davidovits says that Liritzis and his team "should have taken into account the scientific analysis" he and other researchers conducted before backing the carved-not-cast hypothesis.

Robert Temple, co-director of the Project for Historical Dating and a visiting research fellow at universities in the US, Egypt and Greece, has also studied Egypt's monuments.

He agrees with Davidovits about the casting.

"There is no evidence known that suggests the ancient Egyptians had cranes," he says. "Without cranes, it is difficult to imagine how they could have lifted giant stones, some as heavy as 200 tonnes."

Temple, however, agrees about the importance of the fossils.

"Egyptian pyramid blocks of limestone tend to contain fossil shells and nummulites, often huge quantities of them, many of them intact, and many of them of surprisingly large size," he says.

"Frankly, not many people pay attention to the shells, which I have always thought was a shame. 'Seashells in the desert' - a good story."