hugo delile | Université Lyon (original) (raw)

Papers by hugo delile

Once trapped in ancient harbor basins, sediments form environmental archives that have been widel... more Once trapped in ancient harbor basins, sediments form environmental archives that have been widely studied by geoarcheologists in recent decades, especially to help reconstruct fluvio-marine landscapes of the last millennia. In some cases, classic environmental markers cannot be used for this purpose either because of their scarcity in the sedimentary deposits, or because analytical costs limit the resolution that can be achieved. In order to remedy these shortcomings, and to complement the more commonly used proxies, elemental and isotopic geochemistry has been added to the geoarcheological toolkit. Here we show how to “read” the evolution of the paleo-environmental dynamics in the water column of Ostia Antica (Rome’s first maritime harbor) using the geochemical and isotopic record of a 3000-year-old sediment core drilled in the ancient harbor basin. A comparison of the results obtained from Ostia Antica with those of other ancient Mediterranean harbors reveals the nature of the main environmental processes operating during the formation of sedimentary deposits in harbor basins. From this comparative approach, it appears that the respective weight of each control factor is dependent on the coastal geomorphological context of the sites where the harbors were established. Since the discovery of the harbor of Ostia Antica in 2014, this method has provided the means, for the first time, to identify two distinct harbor basin regimes; an initial marine-dominated regime from the middle of the 4th c. BC to ~ the 3rd c. BC, and a later freshwater-dominated regime up to the 2nd c. BC. More generally, we observe the effects of the dynamics of the deltaic progradation of the Tiber, which very early on was subject to a hydro-climatic component, on the processes of alluviation of the harbor basin. Additionally, and also for the first time in harbor geoarcheology, Pb isotope compositions measured specifically on uncontaminated sediments demonstrate their utility for both identifying the geological sources of the sediments of the Tiber delta and discriminating finer from larger particles. The present study further provides an opportunity to test the validity of two hypotheses recently put forward: (1) that a series of three tsunamis is recorded in the harbor silts, and (2) that an initial lagoon-type harbor was constructed at Ostia Antica, which later evolved into a fluvial harbor. Neither of these hypotheses are supported by the present data.

Isotopic evidence showing that Rome’s lead water pipes were the primary source of lead pollution ... more Isotopic evidence showing that Rome’s lead water pipes were the primary source of lead pollution in the city’s runoff reveals the sedimentary profile of lead pollution in the harbor at Ostia to be a sensitive record of the growth of Rome’s water distribution system and hence, of the city itself. The introduction of this lead pipe network can now be dated to around the second century BC, testifying to a delay of about a century and a half between the introduction of Rome’s aqueduct system and the installation of a piped grid. The diachronic evolution of anthropogenic lead contamination is able to capture the main stages of ancient Rome's urbanization until its peak during the early high empire.

Proceedings of the National Academy of Sciences, 2017

Heavy metals from urban runoff preserved in sedimentary deposits record long-term economic and in... more Heavy metals from urban runoff preserved in sedimentary deposits record long-term economic and industrial development via the expansion and contraction of a city’s infrastructure. Lead concentrations and isotopic compositions measured in the sediments of the harbor of Ostia—Rome’s first harbor—show that lead pipes used in the water supply networks of Rome and Ostia were the only source of radiogenic Pb, which, in geologically young central Italy, is the hallmark of urban pollution. High-resolution geochemical, isotopic, and 14C analyses of a sedimentary core from Ostia harbor have allowed us to date the commissioning of Rome’s lead pipe water distribution system to around the second century BC, considerably later than Rome’s first aqueduct built in the late fourth century BC. Even more significantly, the isotopic record of Pb pollution proves to be an unparalleled proxy for tracking the urban development of ancient Rome over more than a millennium, providing a semiquantitative record of the water system’s initial expansion, its later neglect, probably during the civil wars of the first century BC, and its peaking in extent during the relative stability of the early high Imperial period. This core record fills the gap in the system’s history before the appearance of more detailed literary and inscriptional evidence from the late first century BC onward. It also preserves evidence of the changes in the dynamics of the Tiber River that accompanied the construction of Rome’s artificial port, Portus, during the first and second centuries AD.

Journal of Roman Archaeology Supplement, 2017

Lead isotopic systematics of U-poor minerals, such as sulfides and feldspars, can provide unique ... more Lead isotopic systematics of U-poor minerals, such as sulfides and feldspars, can provide unique insights into the origin and evolution of continents because these minerals ''freeze in'' the Pb isotopic composition of the crust during major tectonothermal events, allowing the history of a continent to be told through Pb isotopes. Lead model ages constrain the timing of crust formation while time-integrated U/ Pb, Th/Pb, and Th/U ratios shed light onto key geochemical processes associated with continent formation. Using 6800 Pb isotope measurements of primarily lead ores and minor K-feldspar, we mapped out the Pb isotope systematics across Europe and the Mediterranean. Lead model ages define spatially distinct age provinces, consistent with major tectonic events ranging from the Paleozoic to the Proterozoic and latest Archean. However, the regions defined by time-integrated U/Pb and Th/Pb ratios cut across the boundaries of age provinces, with high U/Pb systematics characterizing most of southern Europe. Magmatic influx, followed by segregation of dense sulfide-rich mafic cumulates, resulted in foundering of U-and Th-poor lower crust, thereby changing the bulk composition of the continental crust and leading to distinct time-integrated U-Th/Pb provinces. We show that the tectonic assembly of small crustal fragments leaves the crust largely undifferentiated, whereas the formation of supercontinents results in fundamental changes in the composition of the crust, identifiable in time and space by means of Pb isotope systematics. Observations based on Pb isotopes open up a new perspective on possible relationships between crustal thickness and geodynamic processes, in particular the role of crustal foundering into the mantle and the mechanisms responsible for the existence of cratons.

Since the discovery of the ancient harbor of Naples in 2004 during construction work on an underg... more Since the discovery of the ancient harbor of Naples in 2004
during construction work on an underground railway, geoarchaeological
studies undertaken on the archaeological excavation have revealed the
main stratigraphic and paleo-environmental levels of the harbor site near
the Piazza Municipio. However, knowledge of the dynamics and paleoenvironmental
changes in the water column of the harbor, as well as the
processes of transport and deposition of sediments that led to siltation
and infilling of the harbor basin, has been lacking due to the absence of
high-resolution data. To fill these gaps, we have undertaken a threedimensional
study (longitudinal, transverse and vertical) of the harbor
deposits by carrying out geochemical and sedimentological analyses of
four stratigraphic sections of the archaeological excavation. The results
show that after a phase of relative calm during the first half of the 1st
c. AD, siltation of the harbor progressed exponentially up to the 5th c.
AD, when dredging operations were carried out to obtain a water level
sufficient for the development of maritime and harbor activities. We
attribute this acceleration of siltation to a combination of climatic,
anthropic and volcanic factors. Volcanic activity was responsible for a
high-energy, tsunami-type event during the eruption of Vesuvius in 79 AD.
From the 5th c. AD onwards, the harbor basin of Neapolis does not appear
to have been functional as evidenced by its transformation into a lagoon
following coastal progradation. The last stage of infilling was the
development of a flood-dominated fan delta under the combined influences
of climatic cooling in the Early Medieval Cool Period and agro-pastoral
activities in the catchment area of the harbor. Several generations of
paleo-channels, containing flash flood deposits, as well as sheet wash
from sheet floods, are indicative of high environmental instability in
this period.

The influence of a sophisticated water distribution system on urban development in Roman times is... more The influence of a sophisticated water distribution system on urban development in Roman times is tested against the impact of Vesuvius volcanic activity, in particular the great eruption of AD 79, on all of the ancient cities of the Bay of Naples (Neapolis). Written accounts on urbanization outside of Rome are scarce and the archaeological record sketchy, especially during the tumultuous fifth and sixth centuries AD when Neapolis became the dominant city in the region. Here we show that isotopic ratios of lead measured on a well-dated sedimentary sequence from Neapolis’ harbor covering the first six centuries CE have recorded how the AD 79 eruption was followed by a complete overhaul of Neapolis’ water supply network. The Pb isotopic signatures of the sediments further reveal that the previously steady growth of Neapolis’ water distribution system ceased during the collapse of the fifth century AD, although vital repairs to this critical infrastructure were still carried out in the aftermath of invasions and volcanic eruptions.

The geomorphological response of valley bottoms in eastern France to climatic fluctuations of the... more The geomorphological response of valley bottoms in eastern France to climatic fluctuations of the Little Ice Age (LIA) was investigated using sedimentological analysis together with optically stimulated luminescence (OSL) and radiocarbon dating. Diachronic mapping of land use since the beginning of the nineteenth century was also carried out. Since A.D. 1500, the valley bottoms experienced three cycles of aggradation and subsequent incision , each characterized by paired periods of high and low detritic activity. While the impact of human activity on the aggradation of the alluvial plain is observed, the vertical dynamics of the valley bottom deposits seemingly were also linked to the hydroclimatic fluctuations during the LIA. The sensitivity to these fluctuations was increased by human activity at the scale of the basin. Variations of the winter North Atlantic Oscillation (NAO) and solar activity from the last five centuries correlate with wet and cold phases during which valley bottoms accumulated , and dry and warm phases during which the streams incised into the valley floors. This fluvial sensitivity to the meteorological conditions induced temporal variations in sedimentary supply originating from either direct input from remnants of periglacial alluvial sheets or local rocky outcrops and/or from indirect input from the erosion of alluvial and colluvial deposits. These two components, combined with the sheet runoff over the ploughlands, express the complex coupling between hillslopes and valley bottoms in the headwater catchments. This caused a cascade-shaped transit of the sediments characterized by alternating phases of storage and removal.

Although the ancient site of Utica has been studied since the 19th century, the location of its ... more Although the ancient site of Utica has been studied since the 19th century,
the location of its harbors remains unresolved as they were buried under sediments
as the Mejerda delta prograded and left Utica 10 km inland. Using relief
data and a coring survey with sedimentological analysis, we identify the dynamics
of the delta’s progradation, which produced a double system of alluvial
fans. These show that the ancient bay of Utica silted up faster and earlier than
was thought, probably before the end of the Punic period. Combined with the
radiocarbon dates from coring, this suggests that the harbor lay on the northwestern
side of the Utica promontory, communicating with the sea by a marine
corridor west of the northern compartment of the delta. As the infilling of the
ancient bay progressed, this corridor narrowed until it disappeared completely
in the early 5th/mid-6th century A.D., when a peat bog developed on the
northern side of the promontory, sealing the fate of Utica as a port. This relative
environmental stability ended in the 9th–10th century A.D. when about
4 m of sediment, probably of fluvial origin, covered the peat bog, leaving the
site more than 4.5 m above the local sea level.

The Majerda delta formation has been the subject of many studies since the late XIXe century. The... more The Majerda delta formation has been the subject of many studies since the late XIXe century. The reconstruction of the fluvial palaeo-environments of the lower Majerda valley is significant as it is critical to understand the decline of Utica following the siltation of the harbor,
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which is presently buried under sediments. The progression of the delta across the corridor separating the Southern and the Northern compartments of the ancient Utica bay is the cornerstone of our research on the delta. On the basis of a GIS we propose to identify hydro- and morpho-sedimentary processes of the deltaic progradation dynamics. They lead to innovative ways of considering the initial implantation site of Utica, the conditions of harbor siltation and the Majerda River itself across the Northern compartment. Observations and analysis from the GIS allowed highlighting a double system of alluvial fans over the whole delta. The first component which may be described as “torrential” is present throughout the delta fringe, while the second category of flat alluvial fans occurs at the Majerda defluviation sites, forming coalescing alluvial lobes. The ancient merging of these two morphological systems close to Utica could reflect a process of harbor silting more complex than previously considered, the Majerda River being considered as the unique factor of change so far.

Portus was Rome’s maritime port during the Roman Empire. In AD 42, the harbour location was selec... more Portus was Rome’s maritime port during the Roman Empire. In AD 42, the harbour location was selected about 3 km north of Ostia,
along the Tyrrhenian coast, on the margin of the Tiber River. Portus and its maritime façade are well known, however the fluvial aspects
of Portus are poorly documented. How did Roman engineers preserve a continuous waterway from the basins of Portus to the Tiber
River without accelerating siltation inside the harbour? Were their choices efficient? The present Canale di Comunicazione Traverso is
the only canal attested to link the Tiber River and the harbour basins. The objective of this work is to analyse the Canale Traverso sediments
infill in order to establish the role of this canal in relation to the infill deposits of the harbour basins and to define the functions
of the canal. This study is based primarily on a reinterpretation of the available archaeological data, as well as mainly on sedimentological
analysis and the interpretation of the Passega diagram. A Passega diagram is presented for understanding the deposit processes
for the harbour environments at the entrance to the Trajanic basin (TR-XIV). This diagram is compared to the Passega diagram of the
Canale Traverso (CT-1) which is characterised by a stronger influence of the Tiber River. This study concludes that the Canale Traverso
was a canal that was well protected from the influence of the Tiber River, with the exception of occasional flooding. Also, this paper
presents the patterns of sedimentation at Portus and allows us to define the use of the canal and the maintenance procedures.

Rome and Ephesus are two iconic harbor cities of the ancient Mediterranean; the first was the cen... more Rome and Ephesus are two iconic harbor cities of the ancient Mediterranean; the first was the
center of the Roman Empire and the second became the Roman capital of Asia Minor at the end of the
1st c. BC. The economic and commercial influence of these two ports in the Mediterranean depended
heavily on their harbor systems. The aim of this study is to discern the economic development of
Rome and Ephesus from the geochemical signals of the pollution they were exposed to. To this end,
we drilled cores through the sedimentary archives of the two ancient harbors and measured major and
trace element concentrations and Pb isotope compositions. Both harbors were subject to delta
progradation, Rome by the Tiber and Ephesus by the Caÿster, which changed the aquatic
environments from being initially open and well oxygenated to becoming closed and anoxic. The
harbor basins finally shut down for shipping when an epilimnic system came into place due to too
shallow a depth of the water column. Although changing environmental conditions and multiple
dredgings appear to have altered some parts of the geochemical record, the pollution levels of lead
quite accurately reflect the state of the economic health of Rome and Ephesus, which evolved the most
during periods of prosperity and disorder. Pb isotope data, converted into geological parameters
(Tmod, μ and к), further allowed deducing the provenance of the geological sources of lead ores at the
origin of the pollution. Based on these results, it appears that lead ore supplies during the Roman
period were of local origins, reflecting how Rome and Ephesus dominated the surrounding economic
areas with which they were in contact. However, while the beginning of the Middle Ages is
accompanied by a decline of Rome, Ephesus regains its past prosperity with the importation of
Hercynian lead from western Europe. It was produced massively as a result of the medieval economic
revolution that Europe experienced from the 10th century onward.

At the end of the first century BC, Ephesus became the Roman capital of Asia Minor and the most i... more At the end of the first century BC, Ephesus became the Roman capital of Asia Minor and the most
important commercial, religious, and cultural center of the region. In order to evaluate the status of
anthropogenic fluxes in the port of Ephesus, a 12 m long sediment core drilled in the Roman basin was
investigated to shed light on the paleo-environmental evolution of the harbor using grain size distribution
analysis, 14C ages, major and trace element geochemistry, and Pb isotope compositions. With the
help of complementary sedimentological data and Principal Component Analysis, five distinct units were
identified which, together, reflect the different stages of water history in the harbor. Among the major
disruptive events affecting the port were earthquakes and military events, both of which were particularly
effective at destroying the water distribution system.
Seasonal floods of the Cayster River (Küçük Menderes) were the major source of the silt that progressively
infilled the harbor. Silting inwas further enhanced by the westward migration of the river mouth. A
single major disruptive event located at 550 cm core depth and heralding the development of anoxia in the
harbor marks the end of the dynamic regime that otherwise controlled the harbor water throughout the
RomanEmpire period. This remarkable event maycorrespond to amajor disruption of the aqueduct system
or to a brutal avulsion of the Cayster River bed. It clearly represents amajor disturbance in the history of life
at Ephesus. It is poorly dated, but probably occurred during the reign of Augustus or shortly after. Lead
isotope and trace metal evidence suggest that in the four bottom units pollutionwas subdued with respect
to other Pb metal inputs, presumably those from aqueducts and natural karstic springs. Near the top of the
core, which coincides with harbor abandonment and the more recent period, anthropogenic Pb contamination
is clearly visible in both Pb abundances and isotopic compositions.

Proceedings of the National Academy of Sciences, 2017

Journal of Roman Archaeology Supplement, 2017

Quaternary Science Reviews, 2014

From the 1st century AD and for the duration of the Roman Empire, the Portus complex was the main... more From the 1st century AD and for the duration of the Roman Empire, the Portus complex was the main
harbor of Rome. Its location on the Tiber delta next to the Tyrrhenian Sea produced rapid environmental
changes that, together with historical vicissitudes, largely determined the fate of the harbor. We have
assembled data on the mineralogy, sedimentology, geochemistry, and ostracod populations of a sediment
core drilled in the access channel of the hexagonal basin of Trajan, with the expectation that such a
combined data set will shed new light on how the connections of the inland Trajan basin with the Tiber
river, the earlier Claudius harbor on the nearby shoreline, and the sea evolved through the centuries. The
data define four distinct periods which geochemistry characterizes by different conditions of salinity and
oxygenation. These in turn can be related to historical periods and events by means of 14C data. The early
Imperial Period was dominated by input of well-oxygenated freshwater from the Tiber. During the Late
Empire, harbor water became relatively more influenced by seawater and increasingly oxygen deficient,
which attests to a decommissioning of the Canale Trasverso connecting the harbor to the Tiber. The strong
anthropogenic signal, which is visible very clearly in geochemical parameters, attests to the human
occupation of the harbor area up to the Early Middle Ages, when human activity was brought to an
abrupt end. The simultaneous use in this study of multiple complementary tracers has allowed for the
sedimentary sources of the different classes of particles in the harbor basin to be identified and assigned
to either the freshwater supply from the Canale Trasverso or the seawater of the Claudius harbor.