Laurentine Shore Project

Rome's maritime façade
Sites & sampling

Two main sites have been examined for palaeoenvironmental analyses on the Laurentine Shore:

  1. A pond hypothesised to be a Roman piscina,

  2. and a seasonally wet marshy area the Pozzo Napoliello further inland but associated with the Roman archaeology.

Following reconstruction of the Roman period shoreline [link to relevant recon on geoarchaeology page] it can be seen that many of the Roman archaeological remains have a close relationship with their contemporary shoreline.

Location of palaeoenvironmental sampling sites
Fig. 1 Location of sampling sites
Geomorphological context of palaeoenvironmental study sites

Chronology of dune development

The piscinae are situated within a series of dune ridges that were believed to have formed with the seaward progradation of the Tiber delta. If this was the case, then the ages of the dune ridges should decrease moving inland to the modern shoreline. Luminescence dating of the dune ridges is shown in figure 2 and an older-younger, inland-to-seaward trend is clearly observed. Samples from the piscinae are around 2000 years old and are the most seaward of the samples shown in Fig 2.

Age model of dune development
Fig. 2 Age model of dune development Primary dunes refer to coastal foredunes, secondary, to remobilised aeolian sand
dune ridges & samples taken from vicinity of <em>piscina</em>e
Fig. 3 sampling of dune ridges & from vicinity of piscinae
1) The development of a Roman piscina

The analysed pond was thought to be a piscina, a pond for farming fish and other aquatic species for the dining table. The examined pond is one of a pair that lies adjacent to each other close to the Roman period shoreline. Geophysical survey (figure 6) and archaeological excavation of key features has identified a recorded a series of boundary walls, tanks and structures positioned around the ponded areas.

Research questions

Sediment cores taken from the base of the SE pond (D6) was analysed for two main reasons.

  • To investigate the development of the ponds in relation to their wider geomorphological context, and,

  • to investigate the use of the ponds and any human impacts upon the natural environment by their construction.

Sediment cores & dating of the geomorphology

Sediment cores were retrieved from the base of the piscina (Fig 3 & 5) and samples removed for radiocarbon dating and a variety of palaeoenvironmental analyses. The lower portion of the sediments records a change from marshy silty sediments to peaty organic-rich sediments. This transition is a classic sea level indicator and was primarily examined to investigate whether this was the case.

Location of archaeological sites & sampling locations
Fig. 4 Location of archaeological sites & sampling locations
DEM of Roman <em>piscina</em> with position of transect points (Fig. 7).
Fig. 5 DEM of Roman piscina with position of transect points (see Fig. 7).
Magnetometer survey of <em>piscina</em>
Fig. 6 Magnetometer survey of piscina.
Cross-section of dune & pond topography at <em>piscina</em> (Bicket 2010)
Fig. 7 Cross-section of dune & pond topography at piscina (Bicket 2010)
Schematic log of <em>piscina</em> sediments
Fig. 8 Schematic log of piscina sediments

Chronology of piscina development

In order to examine research question 1, high-resolution diatom analysis with a variety of sedimentological measurements of grain-size, magnetic susceptibility and basic geochemistry was undertaken. The results are summarised in a stratigraphic diagram below and are focused upon the lower portion of the cored sediment.

The initial development of the piscina ca. 2500 BP

Sediments between 150 – 200 cm dates to around 2500 BP (figure 8) and are characterised by a change from marshy silts to peaty sands i.e. a geomorphological change from an exposed marsh to flooded coastal peats which suggests the initial development of a pond (it may also indicated a past sea level). Palaeoenvironmental results are presented in figure 9.

From this analysis an interpretation of several palaeoenvironmental zones can be made. The dates for these zones are presented in figure 11. In particular the dominance of centric diatoms (planktonic species at 171-173 cm) suggests the development of a flooded pond. With the substantial increase in organic content directly linked to the accumulation of plant material as peat in the upper half of the analysed sediments (< 171 cm).

The upper zones (3 & 4) suggest the sampling site developed into a dune slack environment with the accumulation of organic material and a dominance of epiphytic diatoms (found on plants in and around the fringes of the pond), and also a dominance of diatom species that prefer fresh water and increasingly an abundance of nutrients. From this palaeoenvironmental analysis it can be seen that a coastal but fresh-water dune slack had developed by around 2500 BP. It is in this environment that the Roman construction of the piscinae structures discovered during geophysical survey and excavation (figure 3) developed around 2050 BP. This period is the focus of question 2 (see below).

<em>piscina</em> age/depth model=
Fig. 9 piscina age/depth model
Palaeoenvironmental analysis of lower <em>piscina</em> sediments
Fig. 10 Palaeoenvironmental analysis of lower piscina sediments reflecting the initial development of the ponded environment, linked fundamentally to seawards shoreline shift driven by progradation of the Tiber delta (Bicket, 2010).
Geomorphic zone characterisation
Fig. 11 Geomorphic zone characterisation based on palaeoenvironmental multi-proxy analysisof piscina basal sediments (Bicket, 2010).
Roman period activity around the piscina: impacts upon palaeoecology?

To investigate research question 2, i.e. locate evidence for Roman activity within the piscinae sediment record, sediment from the upper 1.5m of the SE pond (D6) was analysed for several palaeoenvironmental proxies including ostracodae and daphnia (to examine changing hydrological conditions in the piscinae). Assemblages of several plant macrofossils were also analysed as well as measuring organic content (by loss-on-ignition), pollen and the abundance of microscopic charcoal (to investigate the tree and plant communities growing close to the sampling sites.

Ostracods are absent during the Roman period of occupation which may be linked to an increase in eutrophication (high nutrient content). No evidence of fish have been found during detailed examination of the sediments (bones etc).

Organic content of the sediments can be seen to significantly increase during the Roman period which is coeval with a sharp increase in the abundance of microscopic charcoal (Fig 13) which may be linked to an increase in burning activity. Artefactual evidence (primarily pottery evidence) from the excavation of the piscina structures suggests that the buildings were built from around 2050 BP. This evidence also suggests a relatively short period of use (perhaps 50 years), which may also be suggested from the abundance of microcharcoal.

Due to the predominant alkaline geochemistry of the piscina groundwater, preservation of pollen was relatively poor. But some basic discussion of local tree species can be made in conjunction with the presence of some arboreal macrofossils (Fig 14, 15 & table 1).

The spread of woodland species within the coastal strip of Castelporziano appears to have been mostly associated with the period following the abandonment of the area ca. 420 AD. Prior to this time, although the pollen record indicates a mixed oak and evergreen woodland nearby, the plant macrofossil record from fishpond D6 shows only Betula growing locally. A little further inland at Pozzo Napoliello the environmental reconstruction provides a picture of a (potentially) grazed marsh or fen with the presence of Alnus, herbs, grasses and sedges during Roman times developing into a wet woodland after abandonment.

Palaeoenvironmental analysis of Roman period sediments=
Fig. 12 Palaeoenvironmental analysis of Roman period sediments (Brown, in preparation)
Dated abundance of micro-charcoal
Fig. 13 Dated abundance of micro-charcoal (#/cm3).
Pollen analysis of Roman period <em>piscina</em> sediments
Fig. 14 Pollen analysis of Roman period piscina sediments (Brown, in preparation).
Plant macrofossil analysis
Fig. 15 Plant macrofossil analysis (Brown, in preparation).
Summary of arboreal pollen & macrofossils from the <em>piscina</em> before, during & after the Roman period
Table 1 Summary of arboreal pollen & macrofossils from the piscina before, during & after the Roman period.
2) Palaeoenvironmental analysis of the Pozzo Napoliello

The Pozzo Napoliello is a seasonally wet area inland of the piscinae. There are Late Bronze Age/ Early Iron Age (LBA/EIA) archaeological remains nearby dating to around 2700 – 2900 BP based on pottery evidence. The geomorphological development of the site has been examined by luminescence dating of dune ridge development which is linked to the progradation of the Tiber Delta. These LBA/EIA sites can be seen to be located on an earlier expression of the shoreline, when the Tiber delta was smaller (a detail of this can be seen in figure 16.

The wet area of the Pozzo Napoliello then developed, perhaps in a similar way to the development of the piscina driven by the progradation of the Tiber delta in an earlier phase. The results of plant macrofossil analysis from Pozzo Napoliello (Fig 18) show an immediate difference between this and the record at the piscina, with the presence of mosses, in particular Lycopodiella inundata (marsh club moss) and Polytrichum commune (hair-cap moss) suggesting a wet sandy location.

The only arboreal macrofossils were those of Alnus glutinosa in the Roman and post-Roman periods, indicates the presence of local wet woodland or fen. Wet woodlands can also be thought of as swamps, in the same way that wet grassland is a marsh however the boundary between the two may be indistinct. The influx of charcoal to this area in pre-Roman times may be associated with early (Iron Age) settlement. The absence of arboreal plant macrofossils in the pre-Roman period with only A. glutinosa being found later may be indicative of the practice of cutting and burning of forests or woodlands to create fields for agriculture or pasture for livestock, which has been found to improve the nutrient content, and increases digestibility of forage. However, this does not suggest the Romans deforested the area as the pollen record for the piscina showed that trees were present at Castelporziano during this period.

The record of aquatic plant macrofossils is equally sparse, with the presence of Potamageton sp., throughout the record until recent times. This macrofossil, along with the Lycopodiella inundata, Polytrichum commune, and Alnus glutinosa shows the presence of a fen. The dominant species are grasses and sedges with the domination of Poaceae throughout almost all of the three time periods, thus suggesting a sedge fen. Other species, such as Juncus effusus and Schoenus compressus are present during the Roman and post-Roman periods and are also consistent with the presence of a fen environment.

Although no crop remains were found in the core, the presence of Aegilops cylindrica was noted at a depth of 70-65 cm, this plant can be found in wheat fields or other cereal grain fields. This does not demonstrate the presence of agriculture at the site, but it is possible that this is the remains of cattle feed which may suggest possible grazing activity upon the fen, which the other plant macrofossils may also suggest in terms of being either, suitable for grazing or indicators of disturbed ground.

Evidence of ground disturbance or local erosion comes from the presence of the non-pollen palynomorph of glomus c.f. fasciculatum chlamydospores, this fungus was present throughout the Roman period only, which may suggest the Roman impact at the site. It appears that this area started off as a dune slack fen, before becoming a sedge fen in character and then a wet forest. The pre-Roman period may show evidence of “slash and burn” agriculture to improve the pasture of the area for grazing. The Romans may have continued to use the area in a similar way to the pre-Roman settlers, but there is the presence of arboreal species in this period. By the post-Roman period the site was abandoned, allowing the arboreal species to dominate.

Late Bronze Age/ Early Iron Age palaeo-shoreline reconstruction=
Fig. 16 Late Bronze Age/ Early Iron Age palaeo-shoreline reconstruction (Bicket, 2010).
Geomorphological context of Pozzo Napoliello
Fig. 17 Geomorphological context of Pozzo Napoliello
Age model of dune development
Fig. 18 Plant macrofossil analysis from Pozzo Napoliello (Brown, in preparation).


Bicket, A. R., 2010, Reconstructing the Holocene coastal development of the Laurentine Shore, Lazio Italy, Ph.D thesis, Dept. of Geography, Loughborough University.

Brown, F. S. J., In preparation, Late Holocene environmental change at Castelporziano, Ph.D thesis, Dept. of Geography, Loughborough University.

Dept. of Classics, Royal Holloway, University of London, Egham, Surrey TW20 0EX
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