Travertine crystal growth ripples record the hydraulic history of ancient Rome\u2019s Anio Novus aqueduct

Duncan Keenan-Jones,Davide Motta,Mayandi Sivaguru,Ryan K Shosted,Bruce W Fouke,Marcelo H Garcia,Mauricio Perillo

doi:10.1038/s41598-022-05158-2

Abstract

Travertine crystal growth ripples are used to reconstruct the early hydraulic history of the Anio Novus aqueduct of ancient Rome. These crystalline morphologies deposited within the aqueduct channel record the hydraulic history of gravity-driven turbulent flow at the time of Roman operation. The wavelength, amplitude, and steepness of these travertine crystal growth ripples indicate that large-scale sustained aqueduct flows scaled directly with the thickness of the aqueous viscous sublayer. Resulting critical shear Reynolds numbers are comparable with those reconstructed from heat/mass transfer crystalline ripples formed in other natural and engineered environments. This includes sediment transport in rivers, lakes, and oceans, chemical precipitation and dissolution in caves, and melting and freezing in ice. Where flow depth and perimeter could be reconstructed from the distribution and stratigraphy of the travertine within the Anio Novus aqueduct, flow velocity and rate have been quantified by deriving roughness-flow relationships that are independent of water temperature. More generally, under conditions of near-constant water temperature and kinematic viscosity within the Anio Novus aqueduct channel, the travertine crystal growth ripple wavelengths increased with decreasing flow velocity, indicating that systematic changes took place in flow rate during travertine deposition. This study establishes that travertine crystal growth ripples such as those preserved in the Anio Novus provide a sensitive record of past hydraulic conditions, which can be similarly reconstructed from travertine deposited in other ancient water conveyance and storage systems around the world.

Highlights

Travertine crystal growth ripples are used to reconstruct the early hydraulic history of the Anio Novus aqueduct of ancient Rome
The present study evaluates an unexpected new class of well-preserved heat/mass transfer crystalline deposits that formed during travertine precipitation on the floors, walls, and roofs of the main channel of the Anio Novus aqueduct of ancient R ome[19,23,24] These deposits were initially reported as “ripples” in the Anio Novus travertine[19] and later called “ripple-like” morphologies in geographically widespread aqueducts in F rance[13], Istanbul and Jordan9, Germany[15], and Turkey[14]
Travertine crystal growth ripples have been utilized in this study to reconstruct the early hydraulic history of the Anio Novus, the largest and farthest reaching of ancient Rome’s 11 aqueducts

Summary

Introduction

Resulting critical shear Reynolds numbers are comparable with those reconstructed from heat/ mass transfer crystalline ripples formed in other natural and engineered environments This includes sediment transport in rivers, lakes, and oceans, chemical precipitation and dissolution in caves, and melting and freezing in ice. Where flow depth and perimeter could be reconstructed from the distribution and stratigraphy of the travertine within the Anio Novus aqueduct, flow velocity and rate have been quantified by deriving roughness-flow relationships that are independent of water temperature. Another common example of heat/mass transfer crystalline deposits are travertine microterracettes formed in terrestrial spring, river, lake, and cave hydraulic systems In these environments, travertine microterracettes (repeated pond and dam stair-steps) form as a result of complex interactions between crystal precipitation from supersaturated aqueous solutions, changing gravity-dependent low-flow hydraulic regimes, the presence and metabolic activity of microorganisms, and a small amount of downstream sediment transport[2,43,44,45,46,47,48]

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Discussion

Conclusion