Champaign, Illinois — Mineral-rich water from Italy’s Apennine Mountains flowed through the ancient Roman Anio Novus Aqueduct, leaving a detailed rock record of past hydraulic conditions, researchers said. Two of his studies characterizing layered limestone (called travertine) deposits within Anio Novus document the occurrence of antigravity growth ripples for the first time, and these features provide clues to the history of ancient water transport and storage systems. was established to give
Led by Bruce Faulk, professor of geology at the University of Illinois at Urbana-Champaign, and published in Scientific Reports and GSA Special Papers, these interdisciplinary studies apply advanced engineering principles and high-resolution microscopy to create undulating geometries. establishes a controversial new theory about how the travertines of the Falk said.
Flowing waters, sourced from the Anio River and an underground lake near Subiaco, Italy, left a wavy layer of calcium carbonate travertine that accumulated along the inner floor, walls and ceiling of the Anio Novus Aqueduct.
In the field, researchers collected upstream-downstream travertine samples that exhibited two distinguishing features: millimeter-scale light and dark layer patterns and centimeter-scale wavy ripple shapes that persisted throughout those layers. To do.
A hand sample showing the rippled travertine deposits of the Anio Novus Aqueduct in vertical section. The sample length is about 27 cm.
Image credit: Bruce Faulk
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Previous studies had proposed, without evidence, that the Anio Novus travertine layers were the result of changes in flow initiated by seasonal changes or engineering methods introduced by the Romans, the researchers said. rice field. However, similar layered travertines occur worldwide in ancient aqueduct systems, regardless of local climate or operation.
Fouke’s specialty is interpreting how microorganisms breeding in mineral-rich waters influence the crystalline structure of travertine and other similar mineral deposits in nature. His group has worked extensively to uncover the geological history of layered mineral formations, speculating life on Mars, from Yellowstone to Australian coral reefs, and even inside the human body. doing.
“The waters of Subiaco are chemically similar to those of Yellowstone National Park, where aquatic microorganisms form mats and biofilms that are critical to the shape and structure of the famous stepped travertine features of Mammoth Hot Springs. It’s doing its job,” says Fouke. “We also identified fossil microbial and plant remains in the dark layers of the Anio Novus travertine deposit. We now know that we have the knowledge base and experience necessary to unlock the history and mystery of the last stream of Anio Novus.”
Fouke and Marcelo Garcia (I. Professor of Civil and Environmental Engineering at the University and co-author of the study) worked with their team to meticulously shape the wavy layers of Anio Novus travertine. measured and made anomalous interpretations.
“Geologists tell us that the only way ripples can form is through fluid shear and gravity-dependent sediment transport,” says Fouke. “The theory is that water and wind move loose sediment into undulating shapes that slowly move forward, under the influence of gravity, to form familiar sedimentary rocks found in riverbanks, sand dunes, and ancient sedimentary rocks deposited in these environments. to form an asymmetrical ripple shape.”
However, Fouke’s team found that Anio Novus travertine crystals precipitated, grew, and accumulated in running water independent of gravity, aided by the shape and biochemical composition of the microbial colony, making them “travertine.” We speculate that they formed what we call “crystals.” ripples of growth. “
The complex processes that control ripples in travertine crystal growth are distinctly different from, but visually similar to, those that control ripples in sediment transport, the researchers say. The shape of the ripples along the vertical walls of the aqueduct is the same as along the floor. This indicates that the mechanism for forming ripples in crystal growth is gravity independent.
Field photograph showing ripples of growth of travertine crystals on the vertical sidewalls of the Anio Novus Aqueduct of the Empiglione Bridge.
Photo credit: Bruce Faulk
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Convinced that the structures were ripples that reflected flow, Garcia and his team measured the shape of the ripples to reconstruct the volume and speed of water flowing through an ancient Roman aqueduct.
“So far, few researchers have recognized these structures as ripples, so no one has used the forces of ripple shape along with the principles of fluid dynamics to create this kind of reconstruction.” Garcia said.
Using travertine deposited in direct contact with the original flume mortar, the researchers concluded that when the flume was first turned on, water flowed at a rate of about 1 meter per second. faster than previous hypotheses.
The presence of wavy travertine along the canal ceiling indicates that the canal was operating at maximum capacity, researchers said. This observation suggests that previous studies stating that stratification formed when seasonal flow changes, or when the Romans used engineering means to control flow rates, were wrong.
“These aqueducts were much more robust than previously thought,” says Fouke. “The current was bigger than I imagined, and the speed of the current was maintained all the time.”
Researchers are now extracting ancient fossilized microbes and their biomolecules trapped in travertine to learn more about the types of microbes and potential pathogens the Romans drank.
“Historians and archaeologists have a keen interest in what led to the fall of the Roman Empire,” Falk said. “Given the key role the aqueduct played in the success of the Romans, information gleaned from the demise of the aqueduct may aid in this effort.”
The Andrew W. Mellon Foundation, the Italian Government, the British Academy and the British School of Rome, the MT Geoffrey Yeh Endowed Course in Civil Engineering, the Ed and Barbara Weil Foundation for Universal Biomineralization at the University of Iowa, and NASA in support of this research.
