Méditerranée N° 1.2 - 2005 107

Historical and prehistorical evolution of the Fortore River

coastal plain and the Lesina Lake area (southern Italy)

Évolution holocène de la plaine littorale du Fortore et de la lagune de Lesina (Italie du Sud)

Armando GRAVINA* Giuseppe MASTRONUZZI** Paolo SANSÒ ***

Abstract - This paper integrates geomorphological, Résumé - Cette étude géomorphologique et archéologique archaeological and radiometric data to reconstruct the evolution essaye de reconstituer l’évolution paléoenvironnementale de la of the Fortore River coastal plain and the Lesina Lake coastal plaine du Fortore et de la lagune de Lesina (Italie du Sud), en barrier, in relation to the main seismic events, Middle - Late relation avec la séismicité, les changements climatiques Holocene climate changes and the human impact which affected holocènes et les impacts d’origine anthropique. this area. Quatre périodes de mobilité des littoraux sont mises en évidence. The available data set indicates that the evolution of the coastal Elles sont séparées par trois crises séismiques aux époques area can be subdivided into four main phases, separated by three préhistorique et historique. Les changements climatiques et les strong earthquakes that struck this region during prehistorical impacts d’origine anthropique ont surtout affecté le fleuve and historical times. Furthermore, climate changes and human Fortore et n’ont eu que des conséquences modestes sur la impact affected mainly the Fortore River dynamics and morphodynamique de la plaine littorale et le cordon littoral de influenced at a smaller magnitude the evolution of the coastal Lesina. plain and the strictly related coastal barrier.

Introduction Mediterranean basin and its highly populated coastal areas show a long and complex evolution marked by several The growth of a coastal plain is related to the re- phases of deforestation, soil erosion and coastal distribution by waves and tides of the material brought to progradation due to the superimposition of climatic the coast by rivers during floods. Coastal areas close to changes and the continuous human impact during the last high mountains, characterised by high rainfall and fronting millennia (e.g.: BRÜCKNER, 1986; 1997; 1998; JELGERSMA, low energy marine – or lake – basins are the most 1988; BRÜCKNER and HOFFMAN, 1992; PROVANSAL, 1993; favourable sites for the development of deltas and related BOENZI et al., 2000; AMOROSI and MILLI, 2001). However, coastal plains. the influence of strong earthquakes, which are often accompanied by rapid, vertical coseismic movements and Human presence and climatic changes also play an by tsunamis, is generally neglected in the reconstruction of important role in the evolution of deltas and coastal plains the geomorphological evolution of delta areas and coastal (BIRD, 1993; DOUGLAS et al., 2001). In particular, the

* Collaboratore Cattedra di Paleontologia, Università degli Studi “La Sapienza”, Roma, Italy; Dipartimento di Geologia e Geofisica, Università degli Studi, Bari, Italy. ** Dipartimento di Geologia e Geofisica, Università degli Studi, Bari, Italy, Corresponding Author: Via E. Orabona, 4 – 70125 Bari, Italy; e.mail: [email protected] *** Dipartimento di Scienza dei Materiali, Università degli Studi, Lecce, Italy.

108 According to DEL GAUDIO et al. (2002), the structure of the Fortore River valley is the most likely cause of the major historical earthquakes recorded in the area and of the generation of large tsunamis, which struck the northern coast of the Gargano Promontory with a recurrence period of about one thousand years (GIANFREDA et al., 2001). The study area is located at the limit between the Mesoadriatic trench to the north, the Gargano Promontory to the east, the northernmost part of the Tavoliere delle Puglie alluvial plain to the south and the Apenninic chain to the west. It comprises three main units which are, from the west to the east: - the Fortore River coastal plain (Photo 1); - the Punta delle Pietre Nere head (Photo 2); - the Lesina Lake coastal barrier (Photo 3).

1.1. The Fortore River coastal plain The Fortore River is a typical Mediterranean river marked by considerable FIG. 1 – GEODYNAMIC SETTING AND LOCALISATION OF STUDIED AREA discharge during winter, with occasional flooding of the coastal plain, and very small load during summer. At present, the river is plains. To fill this gap, interdisciplinary research has been characterised by low discharge and solid load due to the carried on the Fortore River coastal plain and on the presence of several dams built within its drainage basin Lesina Lake area (southern Italy) (Fig. 1), a region (CALDARA et al., 1998). The latter is shaped in a strongly affected by several earthquakes during the last Paleogenic clayey complex, in Miocene flysch deposits two millennia (TINTI et al., 1995; GIANFREDA et al., 2001; and in Miocene-Plio-Pleistocene clays, sands and MASTRONUZZI and SANSÒ, 2002; DE MARTINI et al., 2003). conglomerates (MELIDORO, 1971). Morphologically, the uppermost part of the basin shows slopes strongly affected by landslides, whereas the lower part is marked by an asymmetric profile. The gentler-sloping left bank is marked by a low staircase of fluvial terraces. 1. Geological and geomorphological setting The coastal plain is elongated E-W for about 30 km, from Marina di (Molise), at the eastern The study area is located along the northern coast side of the Apenninic Chain, and Torre Mileto head on the of the Gargano Promontory. The Gargano area is the most Gargano Promontory (Fig. 2). The plain comprises uplifted area of the region, which is the emerged terrigenous sands drifted NW to SE along the Adriatic part of the Adria plate. The latter, in turn, represents the coast of Italy and mainly discharged by the Fortore and foreland of both the east-verging Apennine and west- Biferno Rivers. These sandy deposits are arranged in a HANNEL et al. verging Dinaric orogens (C , 1979) (Fig. 1). complex of swamps, lagoons, dune belts and beach The Apulian foreland is made up of a Precambrian sediments, cut by relict river channels characterised by a crystalline basement associated with a continental Permo - strong variability in arrangement (MASTRONUZZI et al., Triassic cover. This is overlain by an anhydritic-dolomitic 1989) (Photo 1). Triassic succession and by a 6000 m thick sequence of Jurassic-Cretaceous carbonate platform sediments. The The plain stretches between +6 m of elevation and entire sequence is capped by thin deposits of Neogene and the present-day sea level, at the foot of a low cliff whose Quaternary age (RICCHETTI et al., 1988). top constitutes the outer border of the lowermost marine terrace, locally placed between +25 and +10 m above The distribution of the epicentres of the earthquake present mean sea-level. occurred in this area shows that the seismic activity clustered along two main tectonic alignments (Fig. 2): the According to DE MARTINI et al. (2003), sandy E-W trending Mattinata fault (BILLI and SALVINI, 2000; layers ascribed to three different tsunamis have been VALENSISE et al., 2003), and the tectonic alignment detected in the uppermost part of the coastal plain running in a SSW-NNE direction along the right side of sequence. The youngest one is referred to the 1627 AD the Fortore River valley, which extends offshore up to the strong earthquake whereas the lowermost sandy layer right-lateral transfer zone of the Tremiti Islands. would have been deposited during the interval 3630-3350 yr BC. 109

FIG. 2 – SPATIAL DISTRIBUTION OF SEISMICITY THROUGHOUT THE GARGANO PROMONTORY Black circles represent the focal volumes of damaging earthquakes documented from AD 1000 to 1980 (from DEL GAUDIO and PIERRI, 2001, modified). Bold line indicates main faults; dashed line indicates supposed main faults; dotted line indicates the limit between Apennines Units (to the west) and Bradanic Foredeep Units (to the east).

(ORTOLANI and PAGLIUCA, 1987). According to BIGAZZI et al. (1996) it is likely that the Triassic carbonate- evaporite sequence at the Punta delle Pietre Nere head was squeezed and pushed upwards by tectonic events occurred in late Pliocene-early Pleistocene times. The Punta delle Pietre Nere head is also marked by the presence of a Holocene bioherm characterised by calcareous tubes of polychaete annelids, calcified Serpulid worms, sponges, Vermetus sp. and coralline algae and marked by large globular colonies of Cladocora caespitosa (Linneo) in living position. U/Th and radiocarbon age determinations fix its age at 8.8+0.1/-0.2 Ka and 5.9±110 conv.Ka respectively. The PHOTO 1 – AERIAL VIEW OF THE FORTORE DELTA AREA detailed study of this bioherm WITH LOCALISATION OF THE SAMPLES OF TAB. 1 indicates that this particular area has (Photo by Aeronautica Militare Italiana, 1956) been affected during the Holocene by 1.2. Punta delle Pietre Nere head an average uplift rate of 1.5 mm/yr. Moreover, younger The Punta delle Pietre Nere head separates the biogenic encrustations detected on the bioherm surface Fortore River coastal plain from the sandy coastal barrier indicate that the general uplift of the area would have of the Lesina Lake (Photo 2). At this head, igneous rocks, occurred in accordance with a «seismic cycle» Upper Triassic black limestones and deformed gypsum characterised by a slow coastal subsidence, rapidly deposits crop out in a limited area. According to increasing shortly before a major earthquake, followed by COTECCHIA and CANITANO (1954) these rocks rose through coseismic vertical displacements with amplitude > 0.5 m the Jurassic-Cretaceous sedimentary sequence as a result (MASTRONUZZI and SANSÒ, 2002). of diapirism; however, other interpretations suggest a 1.3. The Lesina Lake coastal barrier genetic process of tectonic squeezing (GUERRICCHIO, The Lesina Lake is a coastal lake (sensu EMERY and 1983) and wedge expulsion by tectonic compression 110 three distinct tsunamis which struck the barrier about 2430 years BP, in the year 493 AD and the 30th of July 1627 AD, respectively (GIANFREDA et al., 2001). The sedimentary sequence in the Lesina Lake area has been recently revealed by the digging of a channel at the bottom of the lake to facilitate navigation. The sequence is composed of yellow sands with a eurialine fauna marked by abundant Cerastoderma sp.. This level is capped by a 10 cm -thick duricrust marked by mud crack, overlain by two metres of loose, dark silts and clays.

2. Geomorphological features

The detailed geomorphological survey of the coastal area constrained by several radiocarbon age determinations, allowed the identification of six morphological units (namely Unit A to F), each PHOTO 2 – AERIAL VIEW OF THE PUNTA PIETRE NERE AREA of them representing a main phase of coastline (Photo by Aeronautica Militare Italiana, 1956) progradation, and generally bounded by erosive surfaces (Fig. 3). According to GIANFREDA et al. STEVENSON, 1957) completely isolated from the Adriatic (2001) the main morphological discontinuities Sea by a continuous sandy coastal barrier. The barrier is recognisable within the Lesina Lake coastal barrier can be elongated parallel to the shoreline with a length of 22 km ascribed to the action of large tsunamis, which would and it is characterized by a mean elevation of about 3 m separate A/B and C/D units and, to minor extent, E/F. above present MSL, reaching a maximum elevation of However, further minor discontinuities have been detected about 8 m at Gravaglione locality. Its width ranges from in the Fortore River coastal plain (discontinuites B/C and 1400 m at its western tip, to a minimum of 350 m to the D/E) (tab. 2). Since this area is more sensitive to fluvial east. The lake is characterised by a maximum depth of dynamics, they probably record changes in the Fortore about 1.9 m and by brackish waters fed by a number of River load or in the local wave energy. Moreover, fresh water springs. Two artificial channels connect the geomorphological analyses suggest the occurrence of a lake with the . The coastal barrier is number of shifts in the Fortore River thalweg along the characterized by the presence of four wide washover fans coastal plain. In particular, some relict river branches (Photo 3). Geomorphological analyses and radiocarbon running parallel to the shoreline and in a W-E direction age determinations suggest that they would be the result of have been recognised (Fiume Morto, Acquarotta).

PHOTO 3 – AERIAL VIEW OF THE LESINA SANDY BARRIER IN THE AREA OF TORRE SCAMPAMORTE WITH LOCALISATION OF SAMPLES OF TAB. 1 (Photo by Aeronautica Militare Italiana, 1956)

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FIG. 3 – GEOMORPHOLOGICAL SKETCH OF THE FORTORE RIVER COASTAL PLAIN AND OF LESINA SANDY BARRIER Capital letters indicate the morphological Units reported also in Tab.2. Legend: 1: Middle Holocene cliff shaped in pre-Holocene conglomerate; 2: Colle d’Arena – Gravaglione dune belt; 3: Late Holocene dune belts; 4: tsunami washover; 5: sinkholes in the gypsum units; 6: location of dated samples.

However, the collated data are still very few and do not with irregular spacing. The innermost and highest one, allow, at present, the integration of these changes in the reaches a maximum elevation of about +22 m (Colle course of the river with the general evolution of the area. d’Arena dune belt), and formed at the foot of a relict cliff. It is characterised by loose terrigenous, well 2.1. Morphological unit A sorted fine sands, with a faunal assemblage of pulmonate gastropods represented by Helix sp. (sample Arena 1, 4340 It constitutes the innermost part of the Fortore ± 80 years BP; Tab.1), and rare Pomatia sp. The dune belt River plain (Photo 1; Fig. 3) and it stretches between runs eastwards forming the innermost part of the sandy +6 m and +3 m above present MSL with a mean width of coastal barrier that closes the Lesina Lake. In locality about 1.5 km. Unit A inner margin runs in a WNW-ESE Gravaglione, it reaches the maximum elevation of about direction at the base of a cliff whose top constitutes the +8 m above present MSL; and the fauna is characterised outer border of the lowermost marine terrace, which is by Pomatia sp and Rumina sp., which yielded an age of locally made up of partly cemented conglomerates. Unit A 4450 ± 40 years BP (sample Grava 1 in Tab.1). is crossed at the innermost part by a small river course which flows eastward up to the Acquarotta area. Within the dune complex laminated sands, gently sloping seawards, are alternated with thin layers of small This unit is marked by a number of dune ridges pebbles and bivalves shells. An association of marine TAB. 1 –- SAMPLES DATED BY AMS 14C AND 14C IN THE STUDIED AREA Age calibration has been performed by means of Calib 4.4 software. Marine samples have been calibrated adopting a deltaR value of 118±60 (STUIVER et al., 2001). Analyses were performed at Geochron Laboratories Krueger Enterprises In., Cambridge, Massachussets, U.S.A. (References: A– GIANFREDA et al., 2001; B – MASTRONUZZI and SANSÒ, 2002) Sample Laboratory Specimen Elevation Conventional age ∆CPDB Calibrated age Calibrated age Ref. N° m a.p.s.l. (yr BP ± σ) % AD/BC AD/BC Atmospheric (1σ) Atmospheric (2σ) Fortore River Coastal Plain Foce Vecchia GX-27752 Helix sp 1,5 1590 ± 190 -7,3 315 – 645AD 47 – 782AD B Arena 2 GX-27751 Lima sp 2 3030 ± 190 -2,4 909 – 418BC 1206 – 206BC B Arena 1 GX-25750 Helix sp 7 4340 ± 80 -8,0 3044 – 2882BC 3138 – 2860BC B Lesina Barrier Cauto 1 GX-28021 Pomatia sp 2 1550 ± 50 -8,6 434 – 544AD 415 – 618AD A AMS Andrea 1 GX-28020 Rumina sp 3 2430 ± 40 -7,4 524 – 407BC 564 – 401BC A AMS Grava 1 GX-28022 Pomatia sp 6 4450 ± 40 -7,2 3314 – 3228BC 3140 – 3008BC -

112 bivalve shells and cuttlebones in the latter deposits are arcuate to indicate the development of a small provides an excellent supralittoral-floatsam indicator cuspidate delta. This unit is closed seaward by a (LABOREL pers. comm.). Samples were collected near the continuous dune ridge. Within the Lesina coastal barrier seaward edge of this unit, just below the contact between this unit merges with the former one and no morphological the beach deposits and the related aeolian sands, at about discontinuity can be recognised. +2 m. In particular, a marine bivalve Lima sp. (sample Arena 2) yielded a conventional 14C age of 3030 ± 190 years BP (Tab.1). 2.4. Morphological unit D Unit A forms a continuous belt from Marina di Unit D is recognizable at the Fortore River delta Chieuti, to the west, up to Torre Mileto, to the east and is characterised by a maximum width of 400 m (Fig. 2). On the contrary, the younger morphological units (Photo 1; Fig. 3). The spatial distribution of the dune developed in two separate parts either side of the Punta ridge outlines a cuspidate delta. A sharp, erosive contact delle Pietre Nere head (Photo 2). separates this unit from the older one (i.e. Unit C). A sample of pulmonate gastropods (Helix sp.) collected near the Foce Vecchia (sample Foce Vecchia) locality indicates 2.2. Morphological unit B an age of 1590 ±190 years BP (Tab. 1). A small morphological step running roughly Unit D is easily recognisable on the seaward part of parallel to the present-day shoreline divides this unit from the Lesina Lake coastal barrier since it has a sharp the older one (i.e. Unit A). Unit B is about 500 m wide and morphological contact with the older morphological unit is located 2 m above the present sea level. The inner part (Photo 3; 4). The first ridge of this unit closes the apex of is marked by a small river course flowing eastward to the Foce Cauto washover fan produced by the strong Torre Fortore; the outer part is marked by a number of tsunami that damaged the barrier also near Torre straight dune ridges with E-W direction (Photo 1; Fig. 3). Scampamorte. Radiocarbon age determinations performed Within the Lesina coastal barrier, this unit closes on Pomatia sp. collected within this first ridge (sample the San Andrea washover fan apex and therefore formed Cauto 1) indicate a conventional age of about 1550 ± soon after the occurrence of the tsunami that produced it 50 yr BP (Tab.1). (GIANFREDA et al., 2001). Gastropod specimens collected within the first dune ridge, formed after the tsunami 2.5. Morphological unit E suggest that the development of this unit started at about 2430 ± 40 years BP (sample Andrea1 in Tab. 1). It constitutes a large cuspidate delta still recognizable on the 1950 aerial photograph survey (Photo 1; Fig. 3). At present, this unit is preserved only 2.3. Morphological unit C on the western flank of the Fortore delta having been Unit C marks the Fortore delta area (Photo 1; completely eroded only during the last 50 years between Fig. 3); it has a maximum width of 300 m and is separated the Fortore River mouth and the Punta delle Pietre Nere from the older Unit B by a sharp dune ridge. Dune ridges head (TESSARI et al., 2003). Within the Lesina costal within Unit C are not straight like the older ones but they barrier this unit merges with the older one (Photo 3 et 4).

2.6. Morphological unit F This last unit is a narrow beach that is only recognisable on the 1950 aerial photographs in the Fortore delta area (Photo 1; Fig. 3). At present it has been completely eroded. Within the Lesina coastal barrier this unit closes the Casino La Torre and Foce Schiapparo washover fans and the most recent break in the former dune ridges near Torre Scampamorte. These features were produced by the strong tsunami related to the 30th of July 1627 AD earthquake (GIANFREDA et al., 2001). 3. Settlements dynamics since Neolithic Age

PHOTO 4 - A VIEW OF THE WASHOVER FANS IN THE AREA OF TORRE SCAMPAMORTE The hundreds of prehistorical (Photo by V. RAMOSINI in: Regione Puglia, 1985, modified) and historical sites discovered in the

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Tavoliere area, a region stretching roughly between the centuries of the 6th millennium BC (GRAVINA, 1999). The Fortore River, town and the River, allow plain was gradually abandoned until about 4700 cal. years the characterisation of the dynamics of the settlements BC (Scaloria Bassa phase) because of a long arid phase since the Neolithic (Fig. 4). These dynamics have been locally represented by a thick calcrete horizon, as compared with the occurrence of environmental crisis (i.e. recognised in the Lesina Lake sedimentary sequence. At mainly arid climatic conditions), which affected Southern the southern margin of Gargano Promontory, in the Europe during the Holocene as pointed out by several Siponto area, coastal lagoons developed in overall sabhka authors (i.e. JALUT et al., 2000; MAGNY et al., 2002). In the conditions with associated gypsum deposits (BOENZI et al., Tavoliere area, in particular, the occurrence of severe arid 2001). conditions in the Middle Neolithic Age and in the Middle Improvements in the overall climatic conditions Bronze Age has been recognized on the base of geological during the Late Neolithic - Eneolithic and Early Bronze and archaeological evidence (ALLOCCA et al., 2000; Age promoted the increase in the number of sites CALDARA, 2002). especially along the Fortore River valley and around the The Tavoliere Plain was densely colonized during Lesina Lake (i.e. from the Fortore River mouth to Torre the Ancient Neolithic Age, more precisely in the period Mileto). This period of dense settlement distribution spanning between 5500 cal. years BC and the last spanned from 3700-3600 years BC to 2500-2400 years BC

FIG. 4 - DISTRIBUTION OF PRE-HISTORICAL AND HISTORICAL SETTLEMENTS RELATED TO THE PRESENT LANDSCAPE IN THE AREA OF FORTORE RIVER COASTAL PLAIN AND LESINA LAKE

114 TAB. 2 - SINOPTIC TABLE OF THE RELATION BETWEEN HUMAN PRESENCE, CLIMATE AND GEOLOGICAL PROCESSES IN THE STUDIED AREA Data are related to the entire Tavoliere delle Puglie, an area approximately extended among the Fortore River, Foggia town and the Ofanto River. (*) Indications are inferred from unpublished paletnological and archaeological data and from bibliographic data (ALLOCCA et al., 2000; GRAVINA, 1999; BOENZI et al., 2000; 2001; DE PIPPO et al., 2001; CALDARA et al., 2002); (°) data reported in MASTRONUZZI and SANSÒ (2002); (**) samples reported in Tab. 1. Bold lines indicate major environmental change due to earthquakes and/or tsnamis events; toothed lines indicate minor environmental change due to anthropic and/or climatic factors

115 and continued in the Early Bronze Age until 1800-1700 elevation of this coastline an uplift rate of this area of years BC. Settlements were placed along a former about 1.5 mm/year can be inferred (MASTRONUZZI & coastline at the foot of the Colle D’Arena- Cornone cliff SANSÒ, 2002). The Fortore River was marked during this and around the wide Lesina Bay, which, in this period, was phase by a negligible solid load so that only a narrow progressively closed by the development of a sandy beach formed at the cliff foot. Few kilometers offshore, at coastal barrier. about 5-10 m water depth, a bioherm with Cladocora A new arid phase occurred during the Middle coespitosa developed, whereas in the area of the Lesina Bronze Age between 1800-1700 years BC and 1400-1300 Lake an open lagoon promoted most likely the deposition years BC (corresponding to the arid phase A.4 recognised of sands with Cerastoderma sp. in the Mediterranean area by JALUT et al. (2000) and to the This episode ended during a very arid period, arid period 3 of MAGNY (2002)). It caused a new dramatic between 4800 and 4600 years BC, which caused the area decrease in the number of settlements, which clustered to be abandoned and produced the development of a thick along the Fortore River valley, on the Appenninic Chain duricrust. and on the Gargano Promontory. However, along the Subsequentely, the first progradation of the Fortore Lesina Lake the sites already occupied during the River coastal plain (morphological Unit A) and the Eneolithic were still present during this period. In the development of the high dune belt of Colle d’Arena and Recent and Late Bronze Age, corresponding to the periods Gravaglione started at about 3000 years BC. The coastal th th th th between the 13 and 12 centuries BC and the 11 and 10 barrier which closes the Lesina Lake most likely also centuries BC, respectively, settlements in the Fortore formed in this phase. River coastal plain and around the Lesina Lake area were very few (GRAVINA, 1995). Only the sites of Rivolta, The coastal plain was mainly built by littoral drift, Brecciara, Lesina and Torre Mileto and a number of farms which produced ridges straight and parallel to the cliff foot can be ascribed to the Iron Age (9th to 5th century BC). The at the back, so that a low solid load for the Fortore River latter became more frequent in the Late Republican can be inferred for this period. The lowest course of the Roman Age (from the 4th-3th to the 1st century BC) and in Fortore River is parallel to the coastline flowing in an the Imperial period (from the 2st to the 2sd century AD). eastward direction to the Punta delle Pietre Nere area. During this last phase the Lesina coastal barrier was The number of sites increased during the Eneolithic colonised as testified by occurence of the Porcareccia and age and the Early Bronze Age with numerous settlements Cauto villas. placed along the top of the Middle Holocene cliff and on Finally, sites placed at Foce San Andrea locality, on the small hills around the southern side of the Lesina Lake. the Lesina coastal barrier, near the Lesina railway station, A new, shorter arid period occurred in the Middle Bronze at Lesina Village and Ripalta can be ascribed to the Late Age, from 1700 to 1300 years BC, and caused a decrease Roman Age. These last two sites were inhabited until the in the number of sites, which also remained in the 6th-7th centuries AD (GRAVINA, 1995; 1996). following Recent and Late Bronze Age. A strong seismic event ended this first phase at about 664 years BC. It most likely produced the coseismic uplift of the area to the west of the Fortore River as well as the shaping of the cliff presently at +3 m on the outer 4. Discussion part of morphological Unit A. The landward margin of the Punta delle Pietre Nere head was uplifted above sea level The available data set collated in the area of the becoming, from this moment onward a prominent head, Fortore River plain and the Lesina coastal barrier suggests whereas subsidence occurred to the east, in the Lesina a complex evolution during the Late Holocene influenced Lake area. The coastal barrier was struck by a tsunami, mainly by earthquakes, and related coseismic movements, which produced extensive erosion and the development of tsunamis and, subordinately, by climatic changes and the Sant’Andrea washover fan. anthropic influence (Tab.2). The following model for the Fortore River coastal 4.2. From the strong earthquake of 664 BC to the plain and the Lesina Lake coastal barrier evolution can be 493 AD earthquake reconstructed as follows. The strong earthquake of the year 664 BC was followed by a phase of recovery. During this phase the 4.1. From the maximum postglacial transgression narrow morphological unit B, mostly due to the littoral (about 6500 cal. years BP) to the strong drift, developed. The Fortore River was characterised by a earthquake of ca. 664 BC small solid load and flowed to the east, into the Adriatic During the Middle Holocene, about 6500 cal. years Sea, near Torre Fortore. A new set of dune ridges BP, the postglacial sea-level rise reached its relative developed on the Lesina Lake coastal barrier, closing the maximum position at about 8.5 m above present-day sea apex of the Sant’Andrea washover fan. level, shaping a cliff wtih a W-E direction. Based on the During the Republican Roman Period the Fortore available glacioeustatic sea-level curves and the present River straightened its course and started to build up a

116 small cuspidate delta (morphological Unit C), most likely (morphological Unit F), during the 19th and the 20th in response to an increase in its solid load due to intense centuries, has been replaced during the last 50 years by a deforestation since 400 BC (BOENZI et al., 2000). During phase of strong erosion of the Fortore River delta due to the Imperial Roman period the coastal barrier was sparsly the construction of numerous dams within the Fortore colonised by small farms. River drainage basin.

4.3. From the 493 AD earthquake to the 1087/1223 AD eathquake In 493 AD, a strong earthquake, reported in local Conclusion legends, produced a tsunami responsible for the development of the Foce Cauto washover fan and the This paper is an effort to integrate the available partial erosion of the Lesina Lake coastal barrier geological, climatic, radiometric, archaelogical and (GIANFREDA et al., 2001). Severe erosion most likely also historical data to form an evolutive model of the area. affected the Fortore River cuspidate delta. However, we are aware that the proposed model is not definitive but it could represent a useful tool for the The following recovery phase formed the planning of the future research. morphological Unit D, represented by a new cuspidate delta at the Fortore River mouth and, on the Lesina Lake The data set suggests that the morphological coastal barrier, by a sequence of dune ridges that closed evolution of this coastal region has been deeply influenced the Foce Cauto washover fan apex. by strong earhquakes and rapid, relative sea level changes. The latter are represented mainly by coseismic vertical Eventually, a strong earthquake occurred at the movements and tsunamis which produced rapid and beginning of the second millennium (1087 or 1223 AD) dramatic morphological changes. Climatic changes and which caused a new coseismic uplift of the Punta delle anthropogenic pressure played a subordinate role in the Pietre Nere head and the severe erosion of the Fortore evolution of the area, although still capable of remarkable River delta. modifications of the Fortore river dynamics and of coastal morphology. 4.4. The last millennium During the Little Ice Age (1300 -1800 AD) the area Acknowledgements - This paper is a contribution to of Punta delle Pietre Nere head and of the Lesina Village UNESCO IGCP Project n°437 «Coastal Environmental Change were affected by slow subsidence. The Fortore River was During Sea-Level Highstands» (Project Leader Prof. characterised by a remarkable increase in its solid load, as C. MURRAY-WALLACE). This research has been supported by research projects Miur 60% testified by the construction of a wide cuspidate delta 2002 «Effetti morfologici dell’impatto di tsunami sulle coste (morphological Unit E). della Puglia» and Miur 60% 2003 «Caratterizzazione del The 30th of July 1627 earthquake, produced the potenziale morfogenetico di onde catastrofiche a lungo periodo coseismic uplift of the Punta delle Pietre Nere head. This di ciclicità» (Responsible: Dr. Giuseppe MASTRONUZZI). was preceded by a century of rapid subsidence and a We would like to thank the two anonymous referees for their suggestions which improved the manuscript. A special thank you severe episode of erosion of the Fortore delta and along goes to Antonio LOMBARDI for his friendship and for his the Lesina coastal barrier, where two washover fans, were wonderful love and knowledge of his country and to Drs. formed by a large tsunami. Rossella SBARRA for the improvement of the English form. Finally, the last phase of progradation REFERENCES

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