Depositional and diagenetic history of travertine deposited within the Anio Novus aqueduct of ancient Rome

Mayandi Sivaguru, Kyle W. Fouke, Duncan Keenan-Jones, Davide Motta, Marcelo H. Garcia, Bruce W. Fouke

Research output: Chapter in Book/Report/Conference proceedingChapter

Abstract

Travertine deposits preserved within ancient aqueduct channels record information about the hydrology, temperature, and chemistry of the flowing water from which they precipitated. However, travertine is also chemically reactive and susceptible to freshwater diagenesis, which can alter its original composition and impact reconstructions of aqueduct operation, maintenance, and climate. Hydraulic reconstructions, in combination with a suite of high-resolution optical, laser, electron, and X-ray microscopy analyses, have been used to determine the original crystalline structure and diagenetic alteration of travertine deposited in the Anio Novus aqueduct built in A.D. 38–52 at Roma Vecchia. Age-equivalent travertine deposits, precipitated directly on the mortar-covered floor at upstream and downstream sites along a 140-m-long continuous section of the Anio Novus channel, exhibit consistent crystalline textures and stratigraphic layering. This includes aggrading, prograding, and retrograding sets of travertine linguoid, sinuous, and hummocky crystal growth ripples, as well as sand lags with coated siliciclastic grains deposited on the lee slope of ripple crests. The original aqueduct travertine, which is similar to travertine formed in analogous natural environments, is composed of shrub-like, dendritically branching aggregates of 1–3-μm-diameter euhedral calcite crystals. Dark brown organic matter-rich laminae, formed by microbial biofilms and plant debris, create stratigraphic sequences of high-frequency, dark–light layering. This hydraulic and petrographic evidence suggests that large, radiaxial calcites diagenetically replaced the original aqueduct travertine shrubs, forming upward-branching replacement crystals that crosscut the biofilm laminae. While this diagenetic process destroyed the original crystalline fabric of the calcite shrubs, the entombed biofilm laminae were mimetically preserved. These integrated approaches create the type of depositional and diagenetic framework required for future chemostratigraphic analyses of travertine deposited in the Anio Novus and other ancient water conveyance and storage systems around the world, from which ancient human activity and climatic change can be more accurately reconstructed.
Original languageEnglish (US)
Title of host publicationFrom the Guajira Desert to the Apennines, and from Mediterranean Microplates to the Mexican Killer Asteroid
Subtitle of host publicationHonoring the Career of Walter Alvarez
EditorsChristian Koeberl, Philippe Claeys, Alessandro Montanari
PublisherGeological Society of America
ISBN (Electronic)9780813795577
ISBN (Print)9780813725574
DOIs
StatePublished - Jun 21 2022

Publication series

NameGSA Special Papers
Volume557

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