RICOSTRUZIONE PALEOGEOGRAFICA E PALEOAMBIENTALE DELLA CITTA’ DI NAPOLI: UN’INDAGINE GEOARCHEOLOGICA

The city of Naples (Italy) is densely inhabited and rich in history, the area having been exploited for human settlements since the 7th century BC (Fig.1). Hence examining its geomorphological and palaeoenvironmental history is no simple task. For the last 20 years, archaeological excavations during the construction of the Naples metro have offered the possibility to conduct in-depth geoarchaeological research in the city and initiate fruitful collaboration between the Department of Earth Sciences, Environment and Resources of the University of Naples, the Archaeological Heritage Office of Naples and Pompei, and CEREGE, University of Aix-Marseille. During these years, geoarchaeological studies have sought to clarify the palaeoenvironmental evolution of the coastline to the east (Irollo, 2005; Ruello, 2008; Allevato et al., 2009, 2010; Amato et al., 2009; Carsana et al., 2009) and west of Naples (Romano et al., 2013) during the last 5000 years. Research has also led to speculation about the history of the relative sea level and local ground movements during the last 5000 years (Cinque et al., 2011; Romano et al., 2013) for the area now covered by the modern city. Here we present an overview of the different techniques used and the relative contributions made in reconstructing both the mid-late Holocene landscape evolution of the coastal sector of Naples and the palaeoenvironmental changes which occurred in the recently discovered Graeco-Roman harbour between the Hellenistic period and Late Antiquity. In particular two coastal sectors of Naples are analyzed, called “Bay of Chiaia” and “Municipio” (Fig. 2). The research started by examining the detailed computerized maps (1:1000) available for the city. In order to elaborate a digital elevation model of the topography (DEM), the cartographic base was loaded into specific map management software (ArcGis 9.3). To begin DEM processing it was necessary to extract from the cartography only the elevation points and a few contour lines in order to create and organize a precise dataset. These data were integrated with others obtained from a photogrammetric survey (1:11500) performed during the 1990s commissioned by the Department for Postseismic Intervention in Campania and Basilicata. To obtain a correct DEM, the elevation points of man-made structures like roads and buildings were eliminated from the data input. The procedure chosen for the interpolation was ‘Topo to Raster’, an interpolation method specifically designed for the creation of hydrologically correct digital elevation models. This method uses an iterative finite difference interpolation technique. It is optimized to have the computational efficiency of local interpolation methods, such as inverse distance weighted (IDW) interpolation, without losing the surface continuity of global interpolation methods, such as Kriging and Spline. It is also the only ArcGIS interpolator specifically designed to work with contour inputs. Water is the primary erosive force determining the general shape of most landscapes. ‘Topo to Raster’ uses the knowledge of surfaces and imposes constraints on the interpolation process that results in a connected drainage structure and correct representation of ridges and streams. The obtained DEM was used as input data to obtain a contour map in countering with equidistance between the contour lines of 1m and a slope map. The morphological analysis carried out on DEM and on the topographic base obtained, combined with stratigraphic data from boreholes at various points in the city, was used to recognize and reconstruct the geomorphological setting and the palaeodrainage network in order to speculate about their origin and history. The bibliographic study of the archaeological finds and their relative location in the surrounding area gave the opportunity to obtain information about the evolution of both the topographic surface and the palaeomorphology. Each archaeological find was organized into a geoarchaeological dataset and accompanied by the geographic location in the UTM system, its description, elevation and literary source. Archaeological finds useful for palaeo-topographic reconstruction were plotted in specific geological sections in order to understand their relationship with palaeoenvironmental conditions. The rich and very detailed cartography from the many representations of the city at various periods in its history (i.e. Strozzi, 1473; Lafréry- Du Pérac, 1566; Baratta, 1629; Stopendael, 1663; Duke of Noja, 1775; Russo, 1815) was analysed in order to improve the reconstruction of the palaeodrainage network and the ancient morphologies (marine terraces, fault scarp etc.) deleted from the current very dense urban context. By this approach we were able to view the landscape changes connected with urban development in a time range between the Early Middle Ages and the Modern Era. The palaeoenvironmental reconstructions involved an intense and detailed phase of field surveys in the excavation areas (AM: Arco Mirelli dig, SP: San Pasquale dig; MN: Municipio dig) (Fig. 2). The latter were designed to investigate a large number of vertical sections in detail (scale 1:100/1:10). Sedimentary facies were defined by analyzing the external bedding and internal organization concerned with the properties of the clasts such as colour, dimension, degree of rounding, and with the properties of the sediments like sorting, presence or absence of sedimentary structures and global arrangement. Field surveys also helped define the relationship between the geological processes and human pressure in the palaeolandscape. Stratigraphic units were reconstructed and dated by means of their archaeological content. During the field surveys tephrostratigraphic analysis was also carried out. The pyroclastic deposits interbedded in the sequences were measured and described in order to assess their emplacement mechanism. Correlation of these with well-known tephra deposits from the two volcanic districts in proximity to Naples, the Phlegrean Fields and Vesuvius, was made on the basis of their lithology and mineralogy, providing other chronological constraints for the reconstructions. All field surveys were integrated with the palaeoenvironmental information derived from a large number of boreholes drilled in the coastal sector. To improve the palaeoenvironmental reconstructions obtained, laboratory techniques concerned with particle size, palaeontological (macro-microfauna) were conducted on stratigraphic logs. In particular, granulometric analysis was carried out by wet sieving in order to separate coarse, sand and fine (silt+clay) fractions. The results were plotted in vertical-depth diagrams in order to recognize the change in granulometric characteristics along the stratigraphic sequence and in triangular graphs to group sedimentological layers with the same granulometric characteristics. As regards palaeoenvironmental evolution in the area, macrofauna and microfauna (Ostracods) species were grouped according to their palaeoecological environment and plotted in vertical-depth diagrams of taxa distributions. Granulometric and biostratigraphic variables were treated by a statistical approach: for granulometric data, statistical parameters of Folk and Ward (1957) such as mean size, sorting, skewness and kurtosis were calculated in order to obtain precise information about transport capability and degree of sorting of the depositional means; biostratigraphic data were treated with compositional analysis techniques (PCA). In order to combine samples into homogeneous groups, cluster analysis techniques were used. Thanks to the contribution made by all these disciplines and techniques, we are able to offer insights into coastal changes between preprotohistoric times and the Modern Era, and shed light in particular on the actual location of the ancient harbour of Neapolis and its palaeoenvironmental evolution from its foundation to its filling. These results are represented by geological sections and by palaeogeographic scenarios reconstructed on the DEM illustrating the main geomorphological features and the shorelines positions for different temporal steps. Pre-protohistoric Age (Fig. 3) Bay of Chiaia: Throughout the prehistoric period, the Bay of Chiaia, in “Arco Mirelli” and “San Pasquale” digs is characterized by submerged beach environment, affected by sporadic alluvial episodes. It has been possible to show, for the period prehistoric, an high and rocky coast landscape, characterized by a backward paleofalesia with respect to the current coastline. At the end of the prehistoric period we see a paleoenvironmental change of Chiaia coastal sector, caused by the deposition of pyroclastic products of Agnano Monte Spina and Astroni Eruptions. Indeed, field evidences in the studied areas show an intertidal environment abrasion platform, corresponding to the pyroclastic products of Agnano Monte Spina and Astroni Eruptions. Such platform is then covered by the volcanic products of Pomici di Avellino Eruption. Municipio sector The maximum of the post-glacial sea level rise, along the east coast of Naples, extended from Piazza Municipio to Piazza Garibaldi, is well evidenced by the presence of transgressive coastal sediments that fill the torrential incisions onto Neapolitan Yellow Tuff substrate, immediately after its deposition. At the peak of the Versilian marine transgression (c.a. 5ka) the paleo geographical scenario shows an high coast morphology, along the edge of Pendino. The shore line corresponding to the Middle Holocene period describes a bay right in the east of Mount Echia, in the area actually occupied by the dig "MN". Greek -Roman Age (Fig. 4) Bay of Chiaia: The Greek-Roman period shows a progressive change in the coastal paleoenvironmental context, with respect to previous time. Referring to this period sees a submerged marine environment establishing both in ‘San Pasquale’ and ‘Arco Mirelli’ digs. During the First Imperial Age (1st century AD), foreshore deposits alternate with submerged marine environment ones, constituting a bar - troughs system. Like Pre-protohistoric Age, torrential contributions interrupt the fine sand sedimentation typical of submerged environment and produce erosion and strong reduction of the deposits thickness. During the late 1st century AD and throughout the Middle Late Empire, the marine deposition and the upstream contributions determines the progressive progradation of the shoreline and the growth of a narrow beach strip at the foot of the Pre-Protohistoric paleofalesia. Municipio sector During the Greek -Roman Age (late 4th century BC- 4th century AD) it shows better the bay of the Pre-protohistoric Age. The area became the site of an harbour basin, as documented by the discovery of an Augustan Age quay built in mortar and tuff (“pds Line 6” and “Mezzanino San Giacomo” excavation areas in “Municipio dig”), and piers and jetties with orientation perpendicular to the quay (Fig. 5). To the north of the quay (1st century AD), merchant shipwreck are also found (“pds Line 1” in “Municipio dig”). During this time, the ancient harbour basin is characterized by a partially submerged beach, partially sheltered only in its oriental portions, due to the presence of a very pronounced promontory consisting of Neapolitan Yellow Tuff. Field investigations conducted in the “pds Line 6- Municipio dig”, showed traces of anthropogenic origin on the surface of tuffaceous substrate of the ancient harbour, located under the Augustan quay. The seafloor sediments of Greek-Roman harbour basin, covers a time interval between the 4th century BC (Hellenistic period) and the end of the 4th century AD. These sediments consist of medium-coarse sand in the inner zones of the basin that become more silty sediments moving towards the open sea. The functionality of the ancient harbour basin is provided by dredging of the seafloor sediments occurred several times between the 4th century BC and the 1st century AD The significant presence of ceramics, glass, building blocks, pebbles ballast is a further confirmation that the bay in this area is used as trading port. The entire period of functionality of the harbor basin, is also characterized by the presence of infratidal marine species in the sediments, connected with the open sea. Therefore, the faunal information confirm the idea that the Greek-Roman Harbour in Neapolis was not an artificial closed area but, on the contrary, a structure westward protected by a natural promontory and inserted into the open sea dynamics towards NE. During the period between the 2nd century AD and the 4th century AD, there is an increase of the macro-faunal species. Probably, marine species find physico-chemical conditions more favorable than those of the 1st century AD, at the end of both dredging activity and the reshuffle of the volcanic deposits of the 79 AD Vesuvius eruption. From Late Antiquity to the Modern Age (Figg. 6, 7) Bay of Chiaia: The coastal landscape during Late Antiquity consists of a narrow emerged beach characterized by alluvial deposits that cause the gradual burial of paleofalesia and the progradation of the shoreline. In the digs of “Arco Mirelli” and “San Pasquale”, torrential and alluvial deposits of the 4th century AD, deposited in alluvial fans locally cut the beach shore Roman Age units. Probably they are related both to climatic factors and to poor maintenance of the slopes in association with periods of global economic and social crisis. The succession of Late Antiquity closes with an anthropogenic deposit origin at about -1 m slm. The absence of selection and the chaotic distribution of materials lead to interpret this deposit as the result of one or more subsequent stages of discharges and the use of the beach below as a special area of the wast dump. The long hiatus (High Medieval Age) in the stratigraphic sequence at the top of the succession of Late Antiquity, which observed in both digs, shows a period of stability of environment emerged along the coast. Furthermore, it appears to indicate the existence of a significant stasis in the processes of erosion of the slopes behind the bay. With regard to the Modern Age, the profile of the studied coast appears shaped by the developed urban context. Municipio sector: During the first half of the 5th century AD, important paleoecological and paleoenvironmental changes are observed. The significant increase in lagoon and muddy sand species accompanied by a decrease of the infralittoral environment species, is interpretable as an enclosure of the harbor basin and the formation of a lagoon. The latter is favored by the growth of parallel beach ridges at the entrance of the bay. Also, the textural composition of the sediments of the seafloor (characterized by a decrease in grain size), is probably associated to sedimentation processes typical of an environment more sheltered than the previous phases. During the second half of the 5th century AD and the beginning of the 6th century AD occurs the progressive burial and abandonment of harbour basin. The sediments that close the stratigraphic succession of Late Antiquity (second half of the 5th century AD-6th century AD) are very coarse and not selected. Torrential arrivals in the lagoon fill it completely. The evidence of a change in the intended use of the area is evidenced by the widespread presence of paleosoils of the 6th century AD on which they were found accommodations farm. The modest shoreline progradational trend during Late Antiquity will continue until the Modern Age. In the late Medieval poor drainage condition typical of a marshy environment occurs. With regard to the Modern Age, the profile of the studied coast appears shaped by both the developed urban context and the construction of two port basins identified as “Molo Grande” e “Molo Piccolo

La ricostruzione delle antiche linee di riva da evidenze geologiche e archeologiche nella città di Napoli

uso degli indicatori geologici ed archeologici per la ricostruzione delle linee di riv

Ricostruzione paleogeografia paleoambientale della città di Napoli: un'indagine geoarcheologica

Mediante un approccio integrato di analisi geologiche ed archeologiche viene ricostruita la successione stratigrafica e paleoambientale del bacino del porto antico di Neapolis, dal terzo secolo a.C. al quinto secolo d.C. La ricostruzione viene estesa all'area della costa napoletana fra Posillipo e la Piana del Sebeto mediante correlazione con dati di altri scavi e sondaggi ubicati lungo la fascia costiera della città proponendo la ricostruzione delle fasi di progradazione della costa con gli spostamenti della linea di riva nel corso degli ultimi due millenni

The palaeoenvironmental history of the Neapolis (Naples, Italy) harbor basin from the Augustan Age up to the Late Antique period

In the last 20 years, archaeological excavations undertaken during the construction of the new Naples subway have unearthed the harbor basin of the Graeco-Roman town of Parthenope-Neapolis. The opening of a new archaeological dig (Line 6) in 2012 offered the opportunity to improve the previous knowledge about the basin evolution, due to the recovery of huge amounts of archaeological remains as well as of a thick succession of infilling sediments. The latter have been analyzed by means of sedimentological and paleontological analyses whose results have been treated through Compositional Data Analysis (CoDA). This approach has highlighted the palaeoenvironmental changes along the harbor basin infilling, from the Augustan Age up to the Late Antique period. The first infilling phase occurred in a marine infralittoral environment which evolved into a lagoon environment at the beginning of the 5th century AD. This change precedes the final closure of the bay at the end of the 5th century AD, due to increased alluvial inputs from inland, probably connected to both natural and anthropogenic causes

Development and decline of the ancient harbor of Neapolis

International audienceArchaeological excavations, undertaken since 2004 for the construction of the new Naples subway, have unearthed the harbor basin of the Greco–Roman town of Parthenope–Neapolis, furnishing scientists with the opportunity to recover abundant archaeological remains and a thick succession of diverse infill sediments. The latter underwent sedimentological, paleontological, and volcanological analyses. Compositional data analysis, applied to all three data sets, highlighted three main paleoenvironmental changes in the harbor basin from the Augustan Age up to the 6th century A.D. The beginning of harbor activity is recorded during the 3rd century B.C. when sedimentation was interrupted by intensive dredging of the sea‐bottom. The impact of the A.D. 79 Vesuvius eruption, recorded for the first time in the Neapolitan territory, led to a reduction in Posidonia meadows and to an ensuing phase of more restricted water circulation and pollution. At the beginning of the 5th century A.D., an open lagoon environment was established, attesting to coastal progradation. The final closure of this part of the bay occurred at the end of the 5th to the beginning of the 6th century A.D., due to increased alluvial input linked to both natural and anthropogenic causes

Production and circulation of thin walled pottery from the Roman port of Neapolis, Campania (Italy)

Seventeen samples of thin walled pottery from the Roman port of Neapolis (late II century BC - early III century AD) were studied in order to ascertain the type of clay and temper utilised, and their provenance. Seven samples of thin walled pottery from a homogeneous group (based on mineralogical and chemical characteristics) represent a local production of this ceramic class within the Neapolis area. This group was manufactured with a low-CaO clay, that probably derived from a weathered or alluvial deposit, together with reworked pyroclastic material (e.g., Sorrento area or Sebeto River plain) and volcanic sand from the Neapolitan area, containing both Somma-Vesuvius and Phlegraean Fields products. Two other fragments could be attributed to different Campanian production areas, such as the Pozzuoli area. Eight outlier fragments found in the port of Neapolis probably originate from extra regional production sites (e.g., southern Tuscany or the Arno valley)

Development and decline of the ancient harbor of Neapolis

Archaeological excavations, undertaken since 2004 for the construction of the new Naples subway, have unearthed the harbor basin of the Greco–Roman town of Parthenope–Neapolis, furnishing scientists with the opportunity to recover abundant archaeological remains and a thick succession of diverse infill sediments. The latter underwent sedimentological, paleontological, and volcanological analyses. Compositional data analysis, applied to all three data sets, highlighted three main paleoenvironmental changes in the harbor basin from the Augustan Age up to the 6th century A.D. The beginning of harbor activity is recorded during the 3rd century B.C. when sedimentation was interrupted by intensive dredging of the sea-bottom. The impact of the A.D. 79 Vesuvius eruption, recorded for the first time in the Neapolitan territory, led to a reduction in Posidonia meadows and to an ensuing phase of more restricted water circulation and pollution. At the beginning of the 5th century A.D., an open lagoon environment was established, attesting to coastal progradation. The final closure of this part of the bay occurred at the end of the 5th to the beginning of the 6th century A.D., due to increased alluvial input linked to both natural and anthropogenic causes

The landscape history of Naples (Italy) during the midlate Holocene: results of interdisciplinary research

studio integrato dell'evoluzione paleomabientale del porto di Neapoli

Millennial variability of rates of sea-level rise in the ancient harbour of Naples (Italy, western Mediterranean Sea)

International audienceWe reconstructed the late Holocene relative sea-level (RSL) evolution of the ancient harbour of Naples, one of the largest coastal conurbations in the Mediterranean. We carried out multiproxy investigations, coupling archaeological evidence with biological indicators. Our data robustly constrain 2000 yr of non-monotonic changes in sea level, chiefly controlled by the complex volcano-tectonic processes that characterize the area. Between ∼200 BC and AD ∼0, a subsidence rate of more than ∼1.5 mm/yr enhanced the postglacial RSL rise, while negligible or moderate land uplift < ∼0.5 mm/yr triggered a RSL stabilization during the Roman period (first five centuries AD). This stabilization was followed by a post-Roman enhancement of the sea-level rise when ground motion was negative, attested by a subsidence rate of ∼0.5 to ∼1 mm/yr. Our analysis seems to indicate very minor impacts of this nonmonotonic RSL evolution on the activities of the ancient harbour of Naples, which peaked from the third century BC to the second century AD. After this period, the progressive silting of the harbour basin made it impossible to safely navigate within the basin, leading to the progressive decline of the harbour