Fig 1.
Roman ports being studied in the PortusLimen Project (ERC-RoMP) and the harbours discussed in this paper (Ostia and Portus).
Fig 2.
Ostia and Portus during the 2nd c. AD.
The map shows the location of the harbour basins, the canals that connected the two ports and their relationship to the Tiber.
Fig 3.
Borehole locations in the harbour basin of Ostia (upper) and at Portus (lower).
Only the central harbour pool area of Portus with mixed fluvial and marine influences is taken into account here for Portus. The location of the cores with the best-dated stratigraphic sequences are visible on these two maps.
Fig 4.
PADM of the core PO-2 drilled in the harbour of Ostia.
This figure presents the analytical stages in the development of the Palaeoenvironmental Age-Depth Model (PADM chart) for core PO-2: (1) stratigraphy of four main units including pre-harbour deposits (Unit A), deposits in the harbour (Units B and C); post-harbour deposits (Unit C and D); (2) results of the palaeoenvironmental analysis (sediment texture and palaeoecological context of the ostracod assemblages); (3) stratigraphy and radiocarbon dates; (4) PADM. The PADM proposes an integrated age-depth model that includes stratigraphic and palaeoenvironmental data (hydrodynamism and ecological contexts on the Y-axis), their interpretation in terms of palaeogeography or geoarchaeological significance in a harbour context (X-axis), a reconstructed sedimentation curve, and a reconstructed relative sea-level curve. Core PO-2 located in the middle of the harbour of Ostia, was the most representative and provided the most complete dated sequence. The core sequence PO-2 mainly records sedimentation between the 4th century BC and the 1st century AD.
Fig 5.
Harbour operation and PADM of the core PO-2.
PADM chart based upon core PO-2 that represents how the harbour basin of Ostia may have been used. The chart incorporates stratigraphic data as well as factoring in the dredging level hypothesis and possible ship draughts. The PADM shows different stages of harbour potential through time and proposes different hypotheses relating to levels of dredging.
Fig 6.
PADM cross section through the central sector of the river harbour of Ostia.
It draws together the dating sequences of PO-2 and OST-8 (central area) and OST-3 (south side). The three periods and three areas of the harbour follow Goiran et al., 2014 and Hadler et al., 2015.
Fig 7.
PADM of the core TR-14 drilled in the harbour of Portus.
This figure represent the stages in the development of the PADM chart for core TR-XIV, the most complete dated sequence from Portus. Located at the junction of fluvial and marine influences within the port, core TR-XIV is representative of the water dynamics between the Claudian and Trajanic basins and the Fossa Traiana. The core sequence TR-14 mainly records sedimentation between the 2nd and the 4th century AD.
Fig 8.
Harbour operation and PADM of the core TR-14.
This figure shows the PADM chart of the operating life of the pool of the harbours at Portus as reflected in the sedimentary sequence of core TR-XIV, and expressed by four stratigraphic units. The PADM chart incorporates stratigraphic data as well as factoring in the dredging level hypothesis and possible ship draughts. Deep dredging activities may have occurred in the 3rd -4th c. AD.
Fig 9.
PADM of the accesses around the harbour pool of Portus.
It draws together the dating sequences of CT-1 (Canale Trasverso), TR-XX (Entrance to the Trajanic harbour basin) and TR-IX (Canale di Imbocco al Porto di Traiano, Claudian side) [15–17,56]. This figure suggests deep dredging activity during the 1st to the 2nd c. AD, a continuation of deep dredging and an infilling of the harbour between the 2nd and the 4th c. AD, and a harbour that was possibly maintained for smaller ships from the 4th to the 7th c. AD.
Fig 10.
Sedimentary chrono-envelopes of the harbour sequences of Ostia and the harbour pool of Portus.
The Chrono-envelopes are based on all the dating evidence from deposits related to defined harbour areas. Dating of the core PO-2 (Ostia) and TR-XIV (Pool of Portus) have been reported as part of their respective chrono-envelope. A clear change in harbour potential is evident in the chronological shift of harbour basin at the Tiber mouth, from Ostia to Portus in the 1st c. AD.
Fig 11.
Model of an operating harbour based on the PADM analyses of the harbours of Ostia and Portus.
The left side of the figure shows the harbour from a palaeoenvironmental perspective [4,5]. The right side shows the harbour sedimentation in a new interdisciplinary perspective, including data from ancient ship and boat reconstructions and a more detailed consideration of the dredging phases. This model suggests that as soon as a water column here was available, there was potential for navigation and the possibility of that the harbour continued to operate. However, the correlation of different core sequences is needed for a reconstruction of the accessibility of the harbour and a general understanding of its potential through time. The PADM makes diachronic perspectives of this model possible.