Paleobotany

Paleobotany of the archaeological area of Via Neroniana

Via Neroniana is the only area studied in some detail so far. A sequence of deep core samples showed that, during the last Ice Age, in the western portion of the excavation there was a lacustrine environment with thermal waters. In the final stages of the Ice Age (about 10.000 years ago) there was a lowering of the water level, resulting in the emergence of large tracts of those sediments that were deposited within the thermal-lake basin.
A soil began to form on the emerged lake sediments and on the surrounding alluvial deposits; there, the first traces of human presence were found (III millennium B.C., Copper Age). The last fluvial sedimentation phase occurred between V and III millennium B.C., with the arrival of the Brenta of Mezzavia river floodings. The surface of the plain, now stable, was inhabited in the Recent Bronze Age, only to be profoundly reshaped by the actions of the Roman era.

During the last Ice Age, about 20.000 years ago, the archaeological area of Via Neroniana was lapped by a shallow lake basin, which extended into a depression on the north-west. The surrounding vegetation was characterized by plants that live well in wet soils such as alders, bulrushes, sedges and yellow bedstraw. The blackgrass was also present. It is an herbaceous plant that prefers saline soils and that, in the early twentieth century, was abundant around the natural thermal springs of Montegrotto, where the soil had high salt concentration for the stagnation of water. The areas with drier and well exposed soil were however populated by herbaceous plants and shrubs such as juniper, Artemisia, sea-buckthorns, Poaceae and Helianthemum. There were also small wooded areas with mountain pine and/or Scots pine and birch and cold climate plants that are no longer part of the natural flora the Euganean area. The community of fossil diatoms, which was observed in lake sediments, suggests that the basin could be fed by hot springs, that mingled their waters to those of meteoric or ground origin. The species found prefer brackish/ freshwater and pH neutral or greater than 7, both characteristics of the Euganean thermal waters.

At the end of the last Ice Age (about 10.000 years ago), the forest of pine advanced and plants of more temperate, humid climate (which probably survived during the freezing cold in the south-facing slopes, such as spruce, beech and hornbeam trees) and even warmer climate plants that still live on the slopes of the hills, as core, in sunny areas, hornbeam, linden, elm and oak bloomed. The typical aquatic plants disappeared, while plants related to wet soils increased, witnessing a gradual drying of the basin at the end of the last glacial period. This resulted in the emergence of lake sediments in the south-eastern part of the excavation and consequently in the interruption of sedimentation and the development of a soil. Unfortunately soils are formed in sub-aerial conditions and therefore are not suitable for the preservation of organic remains of the vegetation that populated them; there is therefore insufficient evidence for a reconstruction of the environment.

However, brief periods of flooding of the area allowed the development of gastropods communities, of which abundant remains were found. The presence of an indigenous community of Bithynia tentaculata (Linnaeus, 1758) and Heleobia aponensis (Martens, 1858), common species in the waters of the Euganean thermal area, were also recognized. The second is considered of limited distribution to the thermal waters of the Euganean Hills and is also reported in waters with temperatures exceeding 40° Celsius. The fossil fauna suggests that the area was subject to short periods of flooding, with shallow waters and supply of thermal waters.

To the north of the area, after the XIVth century B.C. and before the beginning of the I century A.D. when the Roman villa was built, there were cereal crops (oats, wheat, rye) and vineyards. The natural vegetation was dominated by oak, hazelnut and elm, but there were also beech and hornbeam and fruit trees such as chestnut, walnut and olive. The sediments that preserved the remains of this vegetation and that document the anthropic presence and the agricultural activities were found inside small channels, probably dug to drain the area. On the banks there used to be aquatic plants such as spike-rush, while inside the channel aquatic ranunculus and green algae such as nitella and chara were present.