Sites & sampling
The fundamental geomorphological relationship between the archaeological remains of the Laurentine Shore and their landscape is driven by their location on the southern extent of the Tiber delta. The preservation of the Imperial Roman remains up to 1 km inland of the modern shoreline is due to the progradation (seaward expansion) of the Tiber Delta into the Tyrrhenian Sea during the last 5000 years or so.
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Fig. 1 Dune features within the Castelporziano Estate (Bicket, 2010).
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Reconstructing palaeoshorelines at Castelporziano
Sampling of the dune ridges occurred in transects running from the modern shoreline to several kilometers inland. Luminescence dating of these duneridges has shown that a record of Tiber Delta shoreline progradation is clearly preserved within the Castelporziano Estate (see Bicket, 2010 and Bicket et al., 2009 for further details). Based on the dating of these preserved dune ridge crests an age model was constructed for the last 5000 years. |
Fig. 2 Age model based on luminescence dating of coastal duneridges. Remobilised or laterly formed dunes not associated with tiber delta progradation & remobilised aeolian sand from a dune slack are also included (Bicket, 2010).
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Integrating the topographic survey of dune ridges, GPS measurements and published sea level reconstructions (Lambeck et al., 2004, Bellotti et al., 2007) a georeferenced cross-section of the coastal region of the Castelporziano Estate has been constructed (the modern shoreline is on the extreme left). Basic notes on vegetation and geomorphology are included. |
Fig. 3 Schematic cross-section of coastal zone of Castelporziano Estate. These Tiber delta sediments are characterised by the carbonate dune sediments that abur the older, terrestrial reddened dunes and inland sand sheets (Bicket, 2010).
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Holocene palaeo-shoreline reconstructionspiscina
Several palaeoshoreline reconstructions associated with several archaeologically significant periods have been prepared. Mid-Holocene expansion of the Tiber Delta (ca. 5000 BP) After around 5000 BP the lateral expansion of the Tiber Delta reaches the modern position of Castelpoziano (Fig 5 to Fig 6). Two inland coastal dune ridges from the time prior to the expansion of the delta are preserved as iron oxide, reddened dunes (Fig 5). By around 3000 BP several coastal dune ridges are preserved in the deltaic sediments (Fig 6). Shoreline context of LBA/EIA mounds at Castelporziano The earliest known archaeological sites – low mounds containing LBA/EIA pottery – are located over 1 km inland of the current coastline. Following reconstruction of the shoreline contemporary with the estimated age of the pottery (ca. 2.7 – 2.9 ka BP) it can be hypothesised that these early sites where located very close to the shoreline of the time. It appears that there is an enduring relationship between the archaeology of the Castelporziano Estate and the sea, even earlier than the Roman period. |
Fig. 4 Palaeoshoreline reconstruction prior to expansion of the Tiber delta, ca. 5000 BP (Bicket, 2010).
Fig. 5 Early formation of the Tiber delta at Castelporziano. A relatively narrow strip of deltaic sediments with a series of coastal dune ridges is associated with Late Bronze Age pottery found in earthen mounds adjacent to the palaeo-shoreline of the time (Bicket, 2010).
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The Laurentine Shore - ca. 2000 BP
By around 2000 BP, the Tiber delta has increased in size significantly (Fig 6). The Roman archaeological remains are closely related to the shoreline and a network of roads connects these coastal villas and the Vicus Augustanus to Rome, via Ostia, Portus and inland towards Lavinium. The Tiber delta: Imperial Roman context of the Laurentine Shore Figure 7 highlights the wider relationship of the Laurentine Shore with the key sites of Ostia and Portus. Major road links to Rome are also reconstructed from onsite survey, antiquarian maps and classical sources. |
Fig. 6 Geomorphological development of the southern distal end of the Tiber delta by around 2000 BP - the Laurentine Shore (Bicket, 2010).
Fig. 7 The wider Imperial Roman context of the Laurentine Shore. The Via Severiana connects the sites within the Castelporziano Estate to Ostia and Portus. Further road links are likely, moving directly inland from the SE of the site, but the exact route is not fully preserved. The reconstruction is partly based on SRTM DEM data (srtm.nasa.gov) and published reconstructions of Portus (Keay et al., 2005), Ostia (Heinzelmann, 1998) and bespoke measurements incorporated into Bicket (2010).
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References
Bellotti, P., et al., 2007, Late Quaternary landscape evolution of the Tiber River delta plain (Central Italy): new evidence from pollen data, biostratigraphy and 14C dating, Zeitschrift fur Geomorphologie, 51, pp 505 - 534.
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The geoarchaeology of the Laurentine Shore