Available online http://amq.aiqua.it ISSN (online): 2279-7335 Alpine and Mediterranean Quaternary, Vol. 31 (QUATERNARY: Past, Present, Future - AIQUA Conference, Florence, 13-14/06/2018), 13 - 16 FIRST RESULTS ON THE COASTAL CHANGES RELATED TO LOCAL SEA LEVEL VARIATIONS ALONG THE PUTEOLI SECTOR (CAMPI FLEGREI, ITALY) DURING THE HISTORICAL TIMES Pietro P.C. Aucelli 1 , Aldo Cinque 2 , Gaia Mattei 1 , Gerardo Pappone 1 , Michele Stefanile 3 1 Dipartimento di Scienze e Tecnologie, Università degli Studi di Napoli Parthenope, Napoli, Italy 2 Dipartimento di Scienze della Terra, dell’Ambiente e delle Risorse, Università di Napoli Federico II, Napoli, Italy 3 Dipartimento Asia Africa e Mediterraneo, Università L’Orientale di Napoli, Napoli, Italy Corresponding author: G. Mattei ABSTRACT: Puteoli coastal sector is located in the Campi Flegrei volcanic area, along the Mediterranean coasts. This sector is rich in archaeological remains here used as sea-level markers useful to reconstruct the vertical ground movements affecting the CF area. Ma- rine surveys by means of an Unmanned Surface Vessel equipped with geophysical instruments were carried out along the coastal sector to reconstruct the seabed morphology and to detect the submerged remains. By analysing geomorphological stratigraphic and archaeo- logical data, the natural and anthropogenic landscape evolution of Puteoli since the Greek-Roman period was evaluated. KEYWORDS: Campi Flegrei volcanic area; vertical ground movements; sea level markers; coastal changes 1. INTRODUCTION The Puteoli coast is located in the central part of Campi Flegrei caldera, an active volcanic system whose activity spans the last 50,000 years (De Vivo et al., 2010 and reference therein). The caldera formation is mainly related to the Campanian Ignimbrite (CI, 37 ky) and the Neapolitan Yellow Tuff (NYT; 15 ky) eruptions. This area is well known for bradyseism crisis char- acterized by alternating phases of intense uplift and subsidence of different duration. These vertical ground movements (hereinafter VGM) have produced strong modification in the coastal landscape since the Early Holocene. La Starza marine terrace is the oldest silent witness of this volcanic behaviour. In fact, this marine terrace uplifted 30-40 m a.s.l. about 5 ky BP (Di Vito et al., 1999 and reference therein). Instead, the more re- cent historical coastal modifications are mainly testified by the submerged structures of Portus Julius and by the Lythophaga perforations on the marble columns of the macellum, the Roman food market so-called Serapis Temple (Morhange et al., 2006 and reference therein). Despite the repeated modifications of the coastal landscape, this sector was extensively inhabited since the Greek time, as testified by the town of Dicearchia (531 BC) and by the neighbouring Greek colony of Kyme (the oldest in the Western Mediterranean, accord- ing to the ancient authors). However, it reached its maximum expansion during the Roman period with the settlement of the Roman colony of Puteoli (194 BC), in the same site of the Samian Dicearchia, where a porto- rium was created during the Second Punic War. During this period, several human adaptations to bradyseismic crisis that affected the Campi Flegrei area were neces- sary (Aucelli et al, 2017a, b and c). The studies have demonstrated that these VGMs are not distributed uni- formly all over the coast and new data can improve the knowledge on the phenomenon. In this short communication, we present the first result of a geoarchaeological study of the area located off the Puteoli coast at the footslope of La Starza marine terrace that still preserves several traces of coastal changes affecting Campi Flegrei area during the Greek- Roman period due to VGMs. 2. METHODS The Greek-Roman sea level changes and its effects on the coasts were deduced by interpreting depositional, erosional, biological and archaeological markers (Vacchi et al., 2016 and references therein). In the first instance, the coastal sector was investigated by means of an Un- manned Surface Vessel (USV) equipped with geophysi- cal systems and underwater cameras as well as by direct underwater surveys. The USV was engineered by our research group to carry out integrated surveys with acoustical and optical methods at the same time in very shallow waters sectors (Giordano et al., 2015; 2016). The analysis of the morpho-acoustic data allowed reconstructing the seabed morphology and the submer- sion of all submerged archaeological structures (Mattei and Giordano 2014; Aucelli et al., 2016), as the pilae well distributed in the study area and probably dated by his- torical sources at Augustan period (31 BC - 14 AD). By https://doi.org/10.26382/AIQUA.2018.AIQUAconference mailto:gaia.mattei@uniparhtenope.it correcting the present submersion with respect to the indicative meaning (the elevation where the marker was built with respect to the palaeo-sea level, Vacchi et al., 2016 and references therein), a new palaeo-sea level was deduced. Three palaeo sea-level dated at Greek-Roman period were identified by reinterpreting a stratigraphic record close to the macellum (Bellucci et al., 2006), taking into account the archaeological constrains pro- vided by the restorations in this complex and by the Portus Julius construction. The main evolutive steps of the coastal sector in the same period were deduced by analysing high- resolution morphologic (LIDAR, single beam and multi- beam bathymetry) and geological data as well as by interpreting all submerged archaeological remains lo- cated in the study area. 3. RESULTS Puteoli coastal sector has suffered short-lived sub- sidence phases in the historical times which greatly amplified the effects of the eustatic sea level rise (Lambeck et al., 2011), producing the submersion of wide areas. The sea level deduced by studying the 74 sub- merged pilae, probably built not before the Augustan Age and well distributed off the Southern Puteoli coastal sector are an important evidence of a coastal retreat. As the more preserved pila has the top surface at -1 m bsl and considering an indicative range not higher than 2 m, the 1 st century AD sea level was no lower than -3 m. A previous sea level at -6 m was deduced by the present submersion of the Portus Julius entry channel (Passaro et al., 2013). In fact, this military port was hast- ily built in 37 BC, as a new resource for the war against the pirates, and abandoned in a few years for the rapid submersion of port facilities (Todesco et al., 2014). We can deduce a subsidence about of 3 m that also ex- plains the construction of the pilae as a coastal defence during the Augustan age. Two other relative sea level between the 1 st century BC and 1 st century AD were deduced by reinterpreting a stratigraphic record close to the famous macellum probably built in the I century AD, in a place where also a 1st mosaic floor was discovered, probably dated at mid-II century BC by several authors (i.e. Dvorak & Mastolorenz, 1991; Todesco et al., 2014). A sea level dated at the time of the construction of the first struc- tures in this site was evaluated not higher than - 8 m by Bellucci et al. (2006), thanks to the anthropogenic de- posits (with pottery fragments) on which the first floor lies. Consequently, we have calculated a subsidence phase between ca. 150 BC and 37 BC about of 2 m. The 1 st floor was totally buried by 2 m of coarse sands that can be interpreted as an antrophic interven- tion aimed at the construction of the 2 nd marble floor. The last relative sea level at -2 m b.s.l. was de- duced from the position of the second marble floor (probably dated at Flavian age), the second in the se- quence of the site, at 0.086 m a.s.l. (by supposing 2 m of indicative meaning). 4. DISCUSSION AND CONCLUSION This study has provided new data related to Greek- Roman vertical ground movements affecting the Campi Flegrei, by means of a precise detection of four local palaeo-sea level indicators. In the first instance, a new palaeo-sea level proba- bly dated not before the Augustan period (Camodeca, 1994) was evaluated by sensing the underwater ar- chaeological landscape of this sector by using a USV with geophysical instruments. The corresponding coast- line position at that time was reconstructed by integrat- ing the geophysical, geomorphological and archaeologi- cal interpretations (Figure 1). Thanks to these interpretations, a subsidence oc- curred between 37 BC and the 1st century AD was evaluated for the first time, by overlaying the sea level data deriving from the submersion of the defence struc- tures (pilae) here studied with that of Portus Julius (Passaro et al., 2013) built several years before the pilae. In the second instance, the reinterpretation of the stratigraphic record described by Bellucci et al. (2006) allowed us to evaluate the two other palaeo-sea level as well as the corresponding coastline positions (Figure 1). Two subsidence phases deriving from these interpreta- tions were obtained: one between ca. 150 BC and 37 BC, and another during the of 1 st century AD. Taking into account that the eustatic sea level during this time lapse was constantly at -1.1 m b.s.l. (Aucelli et al., 2017; Lambeck et al., 2011), the subsidence of about 3 m can be ascribed to a volcano tectonic ground movement. The vertical ground movements of metric entity here tentatively proposed between 2 nd century BC and 1 st century AD, can be totally ascribed to a volcano- tectonic origin, taking into account that the eustatic sea level rise during this time lapse ranged between -1.38 m and 1.06 m (Aucelli et al., 2017; Lambeck et al., 2011). Taking into account that the eustatic sea level rise during this time lapse ranged between -1.38 m and - 1.06 m (Aucelli et al., 2017; Lambeck et al., 2011), these vertical ground movements of metric entity can be totally ascribed to a volcano-tectonic origin. At that time, this study provides a first evaluation of the subsidence effects on the Campi Flegrei coastal landscape and coastal settlements during the historical times, thanks to the reconstruction of the local sea level variations between the 2 nd century BC and the 1 st cen- tury AD (Figure 1). In conclusion, the historical coastal evolution of the central part of Campi Flegrei caldera has been charac- terized by a coastal retreating about of 150 m. The coastline positions here reconstructed between 200 BC and 14 AD have enabled us to assess this trend. This study has demonstrated as the Puteoli coastal land- scape was strongly modified by volcano-tectonic move- ments inducing fast sea level variations. These coastal changes were reconstructed by overlaying geomor- phological archaeological and stratigraphic interpreta- tions in order to describe the interaction between land- forms evolution and human adaptations. 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