The 20,000-years-long sedimentary record of the Lesina coastal system (southern Italy): From alluvial,to tidal,to wave process regime change

Abstract

The present-day Lesina area (Adriatic coast of southern Italy) preserves in the subsurface the stratigraphic signature of a recent sedimentary process regime change, which was responsible for the conversion of a former alluvial plain into a back-barrier tidal flat and, finally, into the modern barrier island. Facies-based analyses of the first 55 m of the upper Pleistocene–Holocene stratigraphic record, integrated with biostratigraphic sampling, radiocarbon data, and aerial observations of some diagnostic relict morphologies, allowed us to reconstruct the history of the last 20,000 years of this area. The succession investigated is adjacent to a salt dome, which uplifted in recent times, forming the easternmost boundary of the present-day Lesina lagoon. Three main stratigraphic intervals were detected in the subsurface: the lowermost unit is made up of conglomerates, sandstones, and mudstones of terrestrial origin, belonging to a complex system of alluvial plain filling a pre-existing Last Glacial Maximum (LGM) topography. The second interval consists of sands and muds, with subordinate conglomerates of brackish and marine origin, and lies on the previous one through a wide ravinement. Its composing lithofacies exhibit a strong tidal signature preserved in tidal rhythmites belonging to a net of tidal channels, associated with marshes, mud flat, and lagoonal deposits. These sediments record the emplacement of a back-barrier tidal flat, which developed under the strong influence of a tidal influx enhanced by the late post-LGM transgression. The third uppermost interval resulted from the deposition of coastal-marine sands and gravels accumulated during the ensuing modern normal regression, under the dominance of a wave-dominated coastal dynamics, which was responsible for the progradation of the present-day beach barrier and the closure of the Lesina lagoon. The paleogeography of the back-barrier tidal flat preceding the onset of the modern barrier island is thus reconstructed based on the results of our facies analysis, biostratigraphy, and AMS dating. Many of the elements composing this mid-Holocene tide-influenced system were also interpreted from the aerial-photograph observation of several relict morphologies, which are still preserved in many parts of the modern Lesina barrier island. We propose some new interpretation on the origin some of these elements, which possibly developed under sedimentary process regimes different from the modern ones, including some flood-tidal deltas, previously interpreted as tsunami-derived washover fans.

Keywords

Holocene late Pleistocene Lesina coastal system post-LGM transgression process regime change tidal influence

Introduction

Barrier islands are coastal depositional systems which develop where a combination of low wave energy, small tidal excursion with a wide range in tidal prisms, and a broad, gently sloping inner shelf occur (Davies, 1964; Davis and Barnard, 2003; Hayes, 1979). More rare under meso- and macro-tidal regimes (Davis, 1994), barrier islands consist of sand or gravel (shingle) islands elongated parallel to the shore and established from a broadened beach barrier above the high tide level (Bird, 2008; Kjerfve, 1994; Stutz and Pilkey, 2002).

Barrier island process regime and sediment distribution are mostly regulated by waves and longshore currents and, in minor part, by weak tidal currents and neighboring river discharge (Ashley, 1988; Boothroyd et al., 1985; Hayes, 1979; Nichols, 1989; Oertel, 1985; Oertel et al., 1989). However, barrier islands represent just a momentary scenario of a long-lasting evolutionary continuum of a coastal system which, depending on the interplay between relative sea-level fluctuations, sediment supply, and dominant oceanic processes, evolves through different morpho-sedimentological features and process regime changes (Boyd et al., 1992; Daidu, 2013; De Beaumont, 1845; Duck and Da Silva, 2012; Gilbert, 1885; Hoyt, 1967; McGee, 1890; Shepard, 1963).

Barrier islands occur along many coastlines, having developed during and after the last major sea-level rise (Flemming, 2005; Jones, 1977; Pierce and Colquhoun, 1970; Stutz and Pilkey, 2002). Their subsurface represents a formidable stratigraphic record, which possibly includes the various transitorily settings through which a barrier lagoon progressed during its evolution. As a consequence, a multidisciplinary investigation of barrier-island sedimentary successions can reveal important information on the long-term and recent evolution of these depositional systems which, possibly, contrasts with previous interpretations.

This paper presents the results obtained from a sedimentological and biostratigraphic study, integrated with ¹⁴C absolute age determinations, undertaken on the Lesina barrier island, located along the southern Adriatic coast of Italy (Figure 1). Ancient deposits of this area were investigated based on a borehole log dataset drilled to a maximum depth of −55 m from the surface of modern exposure.

Figure 1.

(a) Regional geological setting of the study area in the framework of southern Italy. (b) Structural sketch of the Gargano promontory and location of the study area. (c) General sketch-map of the modern Lesina barrier-island system. Note the location of the boreholes used in the present study and the orientation of the trace (A-A′) whose interpretative profile is reported in Figure 11.

The present-day process regime of the Lesina barrier island is mostly governed by waves, associated with dominant southward-directed longshore currents, which generate important sediment drifts (Brondi et al., 1976; Ferrarin et al., 2014; Poulain, 2001). Previous studies attribute to this dynamics the development of a series of coastal spits, which concurred to the closure of the Lesina lagoon during the Neolithic-Roman period (Boenzi et al., 2006; De Pippo et al., 2001; Gravina, 1999). However, the morpho-sedimentological evidences discussed in the present study suggest a relevant tidal influence on this coast before the onset of a wave-dominated process regime.

Our sequence-stratigraphic analysis of the subsurface of the Lesina system identifies the occurrence of post-Last Glacial Maximum (LGM) alluvial incised-valley fills (IVSs), overlying by a back-barrier tidal flat system. This deposition was the precursor of the modern wave-dominated barrier-island system.

A number of relict forms detectable from aerial photographs of the present-day Lesina area concur to indicate as many environments of these systems were influenced by a tidal influx during their development rather than by a pure wave dominance, and some specific forms can be thus interpreted differently with respect to previous hypotheses.

General geological setting of the study area

The Lesina system is located along the coastline bounding the northern Gargano promontory (Apulia region, southern Italy) (Figure 1a). The Gargano promontory is the northern exposed segment of the Apulia Carbonate Platform. This area represents the foreland for the converging southern Apennine Chain to the West and the Dinaric Chain to the East (D’Argenio et al., 2004; Ortolani and Pagliuca, 1988; Ricchetti et al., 1988; Selli, 1962) (Figure 1b). The sedimentary succession in the Gargano area consists of Permo-Triassic fluvio-deltaic deposits overlain by ca. 6000-m-thick Mesozoic carbonate sediments. The Tertiary succession is represented by discontinuous Miocene–Pliocene bioclastic sediments and by a series of marine terrigenous deposits organized into several orders of terraces (Doglioni et al., 1994; Mastronuzzi and Sansò, 2002a, 2002b; Ricchetti et al., 1988). This terraced sequence is comprised between the middle Pleistocene and the Tyrrhenian age (Cotecchia et al., 1971; Dai Pra and Stearns, 1977; Hearty and Dai Pra, 1992). The Lesina system lies in a relative tectonically unstable area, as the northern Gargano promontory is presently cross-cut by a number of fault systems, many of which were considered active and seismogenetic during the Quaternary (Figure 1b) (Billi et al., 2007; Billi and Salvini, 2000; Patacca and Scandone, 2004). Recent reconstructions based on integrated geomorphological and absolute dating techniques suggest that the Lesina area was repeatedly involved in localized tectonic uplift and subsidence movements because of the co-seismic perturbations induced by strong earthquakes (Mastronuzzi and Sansò, 2012). The same studies also stress the potential role of catastrophic tsunami waves, which struck this shore during the last ca. 5000 years, in the modification of the coastal landscape.

The modern Lesina barrier island

The modern Lesina barrier island consists of a parallel-to-shoreline supratidal beach barrier, which isolates an E-W-elongated shallow-water lagoon from the Adriatic Sea (Figure 1c). The lagoon is connected with the open sea through two narrow artificial inlets, although historical maps dated back to the 16th–17th centuries document other natural entrances in the lagoon. For these features, the Lesina system represents an example of ‘choked’ microtidal lagoon (Duck and Da Silva, 2012).

The Lesina Lagoon, which is the most extended peri-coastal lake of the Italian peninsula after the Venice Lagoon, was widely investigated in the recent past under different aspects. It hosts relevant biological activity and represents an important wetland habitat supporting characteristic flora and fauna (e.g. Breber et al., 2007, 2008; Fabbrocini et al., 2008; Madoni, 2007; Storelli et al., 2007). A great number of archaeological remains found in the Lesina area testify an intense history of commercial and social exchanges, especially during Roman and Aragon times (e.g. Cuda and Gravina, 1998; Pacilio, 2000). The area was particularly investigated in paleoseismic studies, focused on the detection of traces referable to some intense earthquakes that affected the Gargano Promontory and surrounding areas during the last three centuries (e.g. De Martini et al., 2003; Del Gaudio and Pieri, 2000; Gianfreda et al., 2001; Gravina et al., 2005; Mastronuzzi and Sansò, 2012; Tinti and Piatanesi, 1996). Diffuse sinkhole openings recently occurred on the western sector of the Lesina barrier island because of the partial dissolution of the top of a Triassic salt dome, which forms the basement of the Quaternary sediments in this sector (Fidelibus et al., 2011; Refice et al., in press).

Although numerous researches have investigated the Lesina system under different perspectives, studies focused on the sedimentological and stratigraphic aspects of this area are scarce (e.g. De Pippo et al., 2001; Morsilli and Scirocco, 2000). The only stratigraphic reconstruction of the Lesina system was provided by Ricci Lucchi et al. (2006), who distinguished two main upper Pleistocene–Holocene depositional sequences, based on the investigation of two borehole cores drilling the first 55 m of the Lesina subsurface deposits.

Methods

The stratigraphic dataset is based on eight continuously cored boreholes (Figure 1) obtained through a wireline perforation system, which ensured a good recovery percentages. The boreholes were mainly drilled in the modern Lesina beach barrier, following a roughly north–south orientation, down to a maximum depth of −55 m, following a broadly north-south-oriented transect line (Figure 2). Each core was split lengthwise and macroscopically described by using classical facies analysis techniques (e.g. discontinuity surfaces, mean grain size, sedimentary structures, color, and accessory material content, including peat, organic matter, plant and wood fragments, calcareous nodules, mollusk shells, and bioclasts). Facies were subdivided by using ‘chequer plots’ analysis (introduced by Nemec and Muszyński, 1982), which helps to obtain an overview of the vertical facies distribution in the succession (Figure 2). Environmental interpretations were based on the depositional models proposed by Miall (1996) and Bridge (2003, 2006) for alluvial deposits, whereas barrier island and tidal flat deposits were referred to the schemes by Oertel (1985) and Bartholdy (2012).

Figure 2.

Detailed stratigraphies and sedimentary facies vertical distribution (‘chequer plots’) detected in the boreholes analyzed in the present study (see Table 1 for a complete facies framework). Red rectangles indicate absolute radiocarbon dating obtained from selected samples (see complete results in Table 2).

Selected stratigraphic intervals were sampled from boreholes S1, S2, and S4, and five carbon-rich samples (organic clay, peat, or well-preserved mollusk shells) were collected and investigated at the Center for Applied Isotope Studies di Georgia (CAIS, US) laboratories for radiocarbon analysis.

Fifteen sediment samples were collected along the cores S1, S2, S3, and S4, and a sub-aliquot of about 50 g of sediment was taken from each sample for micropaleontological analyses. The sample aliquots were dried at 50°C for 24 h and then treated with hydrogen peroxide (10 vol%) for 12 h, in order to remove the organic matter. Samples were then washed through a 63 µm mesh and dried. Benthic foraminifera and ostracods were studied qualitatively and the foraminifera specimens present in the samples were classified following the taxonomic order of Loeblich and Tappan (1987).

The interpretation of the environmental meaning of the benthic foraminifera and ostracods is inferred from the modern benthic communities (Albani and Serandrei-Barbero, 1990; Bonaduce et al., 1975; Donnici and Serandrei-Barbero, 2002; Ruiz et al., 2000; Serandrei-Barbero et al., 1989, 1999; Sgarella and Moncharmont Zei, 1993; Zecchin et al., 2009).

Results

Sedimentology of the Lesina Quaternary subsurface succession

Three main facies associations were identified on the basis of core data (Table 1). The sequence in which each facies association is described and interpreted reflects their order of occurrence in the stratigraphic record, from bottom to top.

Table 1.

List of the facies associations recognized in the succession investigated and possible environmental interpretation.

Facies association	Facies	Sub-facies	Lithofacies description	Fauna and additional features	Depositional environment	Depositional system
AP	Fc		Poorly sorted polygenic gravels in the lower interval, reddish poorly sorted medium-to-fine sand in the middle interval, and brown sandy silt in the upper interval	Quartz fragments, limonite nodules, mica laminae, plant fragments	Fluvial channel	Alluvial plain
	Cs		Yellowish-brown poorly sorted medium-to-fine sand, with silt and clay layers	Quartz fragments, mica laminae, pebble	Crevasse splay
	Fp		Pinkish-yellow-brown well-sorted silt, with some interbedded of brownish clay or yellowish sand; or brownish clay with interbedded yellowish silty	Angular pebbles, calcium carbonate nodules, quartz grains, mica clasts, carbonaceous rhizomes fragments, limonite spherical nodules. Benthic and planktic fossilized foraminifers, shells of terrestrial gastropods (Helicidae)	Floodplain
BF	Tc	Gl	Poorly sorted polygenic gravels, sub-rounded of maximum size of 3 cm	Quartz fragments, mica lamellae, sub-rounded pebbles. Planktic foraminifers, branches of bryozoans	Tidal channel	Back-barrier tidal flat
		Tscf	Yellowish-brown poorly sorted medium-to-coarse sand	Gastropods shells fragments (Turritella vermicularis), hexacorals remains (Cladocora caespitosa), benthic foraminifers (Cribrononion granosum, Bulimina elongata, Quinqueloculina laevigata)
		Tr	Rhythmic alternation of thick laminae of medium-to-fine sand, yellowish, and of thin laminae of silt, whitish
	Mf		Pinkish-brown well-sorted silt, brown clay	Small bivalve shells fragments (not well defined in the species), calcium carbonate nodules, angular pebbles	Mud flat
	Sm	Bs	Blackish poorly sorted silt	Calcium carbonate nodules, plant fragments, fragments of shells, and opercula of pulmonate gastropods	Inner swamp
		Fs	Brown well-sorted fine sands	Sub-rounded pebbles, rare calcium carbonate nodules, small fragments of bivalve shells	Outer swamp
	Bl		Greenish-gray clay, or alternating of laminae of silt and very fine sand	Rounded pebbles, wood fragments, plant fragments, calcium carbonate nodules, quartz fragments, limonite nodules. Lamellimbranches (Cerastoderma sp. and Cerastoderma glaucoma), gastropods (Hydrobia sp.). Abundant foraminifers (Ammonia beccarii, Cribrononion translucens, Valvulineria perlucida, Haynesina paucilocula). Carapaces of ostracods (Cyprideis torosa and Loxoconcha elliptica)	Back-barrier lagoon
BB	Wd		Yellowish well-sorted medium-to-coarse sand with interbedded clayey brown	Poorly sorted polygenic gravels, sub-rounded of maximum size of 3 cm, bivalve shells fragments	Washover	Barrier island
	Bf		Well-sorted medium-to-fine sand, yellowish-brown or gray-black	Rounded pebbles, of maximum size of 4 cm, bivalve shells fragments (not well defined in the species)	Back-barrier flat

Alluvial plain facies association – AP

This association includes three main facies Fc, Cs, and Fp (Table 1). They form stratasets up to 2–3 m thick each, where these facies repeat rhythmically along the succession. This facies association occupies the lowermost interval of the stratigraphic succession investigated in the present study and is separated from the overlying lithofacies by an abrupt discontinuity surface recognized in every borehole.

Facies Fc: Aggradational fluvial channel fill

The facies Fc was detected in all the examined core stratigraphies. It consists of a fining-upward succession whose thickness ranges from a minimum of 2 m, in the borehole S2, to a maximum of 7 m in the borehole S3 (Figure 2). The lowermost interval of the facies association Fc consists of poorly sorted polygenic gravels (up to 8 cm of maximum diameter), sometimes immersed in an abundant yellowish sandy matrix with muddy inclusions (Figure 3a and b). In addition, abundant quartz fragments, limonite nodules, and mica laminae were found. The intermediate interval of this facies shows poorly sorted medium-to-fine reddish sands, mainly structureless, and containing sub-rounded pebbles and plant fragments (Figure 3c and d). The uppermost interval is made up of brownish sandy silts, sometimes laminated, including abundant plant fragments and scattered calcium carbonate nodules (Figure 3e and f). These deposits revealed no relevant biostratigraphic content.

Figure 3.

Core samples of facies Fc (Aggradational fluvial channel fill). (a, b) Basal pebble lags evolve upward to granule and coarse-grained sands (c) following a fining-upward trend which is common in all the analyzed similar facies. (d) Intermediate interval of facies Fc showing poorly sorted medium-to-fine reddish sands, mainly structureless, and containing sub-rounded pebbles and plant fragments. (e and f) Uppermost intervals of facies Fc consisting of a brownish faintly laminated sandy silts, including scattered calcium carbonate nodules. (g and h) Core samples of facies Cs (Crevasse splay) showing yellowish-brown, poorly sorted, medium-to-fine sands, with silt and clay millimeter-thick intercalations. (i) In some intervals, quartz fragments, mica laminae, and pebbles (arrows) also occur.

Interpretation.

The sedimentological features recorded in the facies association Fc suggest rapid depositional processes after a selective streamflow within a channelized sector. In particular, fining-upward grain size trends indicate a progressive decrease of the transport capacity during the deposition (Bridge, 2003, 2006; Colombera et al., 2013; Holbrook, 2001; Miall, 1985, 1996). Therefore, these characteristics record the filling of an aggradational fluvial channel dominated by vertical accretion. The absence of organic accumulation suggests an uninterrupted activity of the channel and an abrupt deactivation because of channel avulsion, rather than a longer term channel abandonment (Bridge, 2006; Collinson, 1996; Lewin et al., 2005; Miall, 1996). This deposit can be referred to as belonging to a wide alluvial plain.

Facies Cs: Crevasse splay

Facies Cs occurs intermittently in all the core stratigraphies investigated (Figure 2). Sediments consist of yellowish-brown, poorly sorted medium-to-fine sands, with silt and clay millimeter-thick intercalations (Figure 3g and h). Quartz fragments, mica laminae, and pebbles, with 2.5 cm of maximum diameter, were also found (Figure 3i). No macro- and microfauna were recognized.

Interpretation.

The general structureless texture and poorly sorted sediment of facies Cs can be indicative of a depositional process related to a rapid accumulation by a high-energy current capable of moving clasts of different grain size (Bridge, 2006; Miall, 1996). The presence of sands, pebbles, muddy inclusions and the high sand/mud ratio allow interpreting this facies as a crevasse splay deposit (e.g. Bristow et al., 1999). Crevasse splays occur when, during high energy fluvial stages, the river flow exceeds the volume of the channel, producing breaching of the levees, and generating a rapid spread-out of sediments of various grain size into the inter-channel areas (Bridge, 2003, 2006; Bristow et al., 1999; Collinson, 1996; Miall, 1996; North and Davidson, 2012). In modern analogues environments, these deposits form characteristic fan-shaped bodies (Bristow et al., 1999; Jones et al., 1995; Mjøs et al., 1993).

Facies Fp: Floodplain

Facies Fp was pervasively detected in all the borehole stratigraphies reconstructed, and its thickness varies from less than 1 m in the borehole S1 to a maximum 7.5 m in the borehole S2. This facies consists of pinkish-yellow-brown, well-sorted silts, with thin (mm) brownish clay or yellowish sandy intercalations (Figure 4a). In the borehole S3, this facies consists of brownish clays with interbedded yellowish silts (Figure 4b). Angular clasts up to 5 cm in diameter, calcium carbonate nodules, quartz grains, mica clasts were also found (Figure 4c). Small carbonaceous and rhizome fragments, ranging in size between 1 and 3 mm, associated with 0.5–1-mm limonite spherical nodules were recognized (Figure 4d). The biogenic content consists of rare, strongly reworked benthic and planktonic fossilized foraminifers, associated with small fragments of thin shells attributable to terrestrial gastropods (Figure 4e). Shells of Helicidae terrestrial gastropods, preserved or in fragments, were also found (Figure 4f).

Figure 4.

Core samples of facies Fp (Floodplain). (a) Pinkish-yellow-brown, well-sorted silts, with thin (mm) brownish clay or yellowish sandy intercalations. (b) Locally, this facies consists of brownish clays with interbedded yellowish silts. (c) Angular clasts up to 5 cm in diameter, calcium carbonate nodules, quartz grains, mica clasts also occur. (d) At the microscale, this facies also reveals small carbonaceous and rhizome fragments, and associated limonite spherical nodules were recognized. (e) The biogenic content consists of rare, strongly reworked benthic and planktonic foraminifers, associated with small fragments of terrestrial gastropods, including (f) Helicidae.

Interpretation.

Based on a general absence of distinctive sedimentary structures, apart from some sandy or clay laminae, and grain size changes, facies Fp is interpreted as the result of massive, very rapid deposition from suspension of fine-grained sediments transported from sheetflows in a floodplain environment (Cain and Mountney, 2009; Hampton and Horton, 2007; Miall, 1996; Miall and Jones, 2003; Nichols, 2005; Olsen, 1989; Sánchez-Moya et al., 1996). This interpretation is supported by the presence of angular pebbles of considerable size, which possibly derive from intra-clast collisions of gravels, previously accumulated at the base of fluvial channels and reprised during subsequent floods. These features indicate a general low-energy floodplain environment, sporadically reached by fluvial current overflows. Terrestrial gastropods suggest the occurrence of local pond areas, which are typical in floodplains (e.g. Fisher et al., 2007).

Back-Barrier Tidal Flat facies association – BF

This facies association includes four main facies Tc, Mf, Sm, and Bl (Table 1). They form an up to 9-m-thick succession, where these facies stack vertically along the stratigraphy. This facies association occupies the intermediate interval of the stratigraphic succession investigated in the present study.

Facies Tc: Tidal channel

Facies Tc represents the deposit most recurrent and volumetrically important of this facies association. It was found in three core stratigraphies, S1, S2, and S3, at an average depth range of −8.65 to −1 m. This facies includes three main sub-facies, Gl, Tscf, and Tr. (1) Sub-facies Gl (gravel lag of base channel) consists of poorly sorted polygenic sub-rounded gravels, up to 3 cm in diameter, immersed in an abundant grayish fine-sandy matrix (Figure 5a). (2) Sub-facies Tscf (tidal sandy channel fill) consists of yellowish-brown poorly sorted medium-to-coarse sands, locally associated with whitish silty laminae (Figure 5b). Abundant quartz fragments, mica laminae, sub-rounded pebbles, with a maximum diameter of 3 cm, and sporadic plant fragment remains also occur. Bivalve shells, whose species was not well defined, planktic foraminifers, fragments of benthic and millimetric branches of bryozoans were found in these deposits. (3) Sub-facies Tr is represented by rhythmic alternation of thick laminae of medium-to-fine sand, yellowish, and thin laminae of silt, whitish, all well-sorted (Figure 5c). Locally, this primary lamina-scale rhythmicity is partially erased by intense bioturbation (Figure 5d). Quartz fragments and up to 2-cm-large rounded pebbles often occur. Gastropods shells fragments, including Turritella vermicularis, hexacorals remains, such as Cladocora caespitosa, and benthic and planktic foraminifers were also recognized. Among the benthic faunal content, Cribrononion granosum, Bulimina elongata, and Quinqueloculina laevigata were found (Figure 5e).

Figure 5.

Core samples of facies Tc (Tidal channels). (a) Basal pebble lags often occur in the very low interval of these deposits. (b, c and d) Low-angle and plain-parallel lamination consisting of rhythmic repetition of fine sands and silts, often including shell remains and scattered small pebbles. The rhythms (arrows) are consistent with a tidal cyclicity of semi-diurnal duration (see Figure 7). (e) Microphotograph of the benthic faunal content, including Cribrononion granosum, Bulimina elongata, and Quinqueloculina levigata.

Interpretation.

Facies Tc exhibits two important features: (1) an overall meter-scale fining-upward sequence, from gravels or medium-to-coarse sands to fine sands and/or silts; and (2) the presence of tidal rhythmites in the upper facies interval, showing bundle cross lamination. These characteristics are in consistence with a tidal depositional dynamics, where selective water currents flow with pulsating energy, or alternating high and low speed periods, along tidal channels (Eisma, 1998; Flemming and Davis, 1994; Hughes, 2012; Jinliang and Zhongjie, 2008; Rinaldo et al., 2004; Steel et al., 2012). Tidal channels were possibly characterized by shallow, 0.5–0.6 m deep incisions, related to a microtidal regime and lying within the intertidal zone of a back-barrier tidal flat (Allen and Homewood, 1984; Coughenour et al., 2009; Longhitano et al., 2012; Tessier and Gigot, 1998). Lamina numbers plotted against their stacking thicknesses (Figure 6) revealed a harmonic correspondence with the succession of cycles induced by tides. Assuming a semi-diurnal tidal regime affecting this coastal area, laminae were grouped in sets of four tidal bundles, as expression of a complete cycle of ebb- and flood-tidal cycle. As it is common in this type of sedimentary record (e.g. Kvale et al., 1998), some interval appeared incomplete because of amalgamation or erosion (e.g. Archer, 1998; Longhitano, 2011).

Figure 6.

Diagrams obtained from the lamina counting performed in selected core interval of facies Tc. Lamina numbers plotted against their thickness revealed sinusoidal cycles which can be referred to as semi-diurnal tidal cycles, which usually include two episodes of high and low tides in a day. One thick and one thin lamina form a tidal bundle. They were counted in order to reconstruct longer tidal cycles of weekly duration.

Facies Mf: Mud flat

Facies Mf was detected only in the borehole S1, between −10 and −8.80 m of depth. This facies includes pinkish-brown silts, containing small bivalve shell fragments, calcium carbonate nodules, and rare scattered 0.5-cm-large angular pebbles (Figure 7a). Structureless brown clay including sub-rounded small pebbles are often associated (Figure 7b).

Figure 7.

Core samples of facies Mf (Mud flat). (a) Pinkish-brown silts, containing small bivalve shell fragments, calcium carbonate nodules, and rare scattered angular pebbles (arrows). (b) Structureless brown clay with sub-rounded small pebbles. (c) Core samples of facies Sm (Salt marsh). Sub-facies Bs (Blackish silt) consists of blackish silts with diffuse calcium carbonate nodules, plant fragments, undifferentiated shell fragments, and opercula of pulmonate gastropods. It passes upward to (d) sub-facies Fs (Fine sands), which is represented by brown well-sorted fine sands, containing sub-rounded pebbles and indistinct low-angle cross lamination.

Interpretation.

This facies records rapid settling of fine-grained material from suspension in a water column. Suspended sediment was possibly induced by turbulent flows of moderate energy. That is suggested from the presence of small angular pebbles, which possibly derive from disintegration after intra-particle collisions of well-rounded clasts, as well as bioclasts, primarily accumulated in adjacent beach areas and reworked during marine storms. This process can be referred to as mud flat depositional environment, which typically develops in back-barrier tidal basins, comprised between tidal channels and adjacent to the open sea (Flemming, 2002, 2012). Calcium carbonate nodules confirm the reiterated conditions of subaerial exposure and subsequent sporadic inundation of such areas. Overflow episodes can be either frequent or rare in such mud flats, depending on the relative distance of these areas from major tidal channels (which receive more frequently the influx of high-energy storms, compared with peripheral or more internal minor tidal channels).

Facies Sm: Salt marsh

Facies Sm was found in the borehole S2, but at different depth intervals, comprised between −7.85 and −9.25 m. Sediments were included into two sub-facies: Bs and Fs. (1) Sub-facies Bs (Blackish silt) consists of blackish poorly sorted silt intervals, containing diffuse calcium carbonate nodules (Figure 7c); plant fragments; 1-to-3-mm-large, undifferentiated shell fragments; and opercula of pulmonate gastropods. (2) Sub-facies Fs (Fine sands) is represented by brown well-sorted fine sands, containing sub-rounded up to 3-cm-large pebbles and indistinct plane-parallel and low-angle cross lamination (Figure 7d). Rare calcium carbonate nodules and small fragments of bivalve shells also occur.

Interpretation.

Facies Sm reflects sedimentation in a salt marsh environment (e.g. Flemming and Ziegler, 1995). The two sub-facies composing this deposit can be referred to as settling processes of fines by a slowly moving shallow-water column. The distinctive dark-blackish color also suggests microbial mats which, associated with calcium carbonate nodules, indicate long-lasting periods of subaerial exposure in wet conditions. Coarser intercalations may advocate proximity to tidal channel sectors, where water laminae can generate little traction on fine sands, having the transport capacity to move small pebbles and bioclasts after occasional fluvial sheetfloods or sea storms (Ashley, 1988).

Facies Bl: Back-barrier lagoon

Deposits classified within Facies Bl occur in only the core stratigraphy S4, in a depth range comprised between −6.50 and −0.60 m beneath the surface of modern exposure. Sediments consist of mostly structureless or faintly laminated brownish-yellow clays (Figure 8a), or silts and very fine sands forming plain-parallel laminae of centimeter to decimeter bed thicknesses (Figure 8b). Rare rounded pebbles, up to 4 cm of diameter, were recognized, as well as plant fragments, calcium carbonate nodules, quartz clasts, and millimetric limonite spherical nodules (Figure 8c and d). The biogenic content is represented by gastropod and lamellibranch shells fragments of Cerastoderma sp., Cerastoderma Glaucoma, and Hydrobia sp. Foraminifers are also abundant, including Ammonia beccarii, Cribrononion translucens, Valvulineria perlucida, and Haynesina paucilocula. In this faunal assemblage, small fragments of ostracod carapaces of Cypride istorosa and Loxoconcha elliptica were also found.

Figure 8.

Core samples of facies Bl (Back-barrier lagoon). (a) Faintly laminated brownish-yellow clays. (b) Silts and very fine sands including a large bivalve shell fragment. (c) Rounded pebbles associated with plant fragments, calcium carbonate nodules, and quartz clasts. (d) Microphotograph of facies Bl showing very well-sorted clasts with millimetric limonite nodules. (e) Core sample of Facies Wd (Washover deposits), consisting of poorly sorted polygenic sub-rounded clasts and fragments of bivalve shells. (f) Core sample of Facies Bf (Barrier flat) showing yellowish-brown, well-sorted, medium-to-fine sands, containing rounded pebbles (black arrows) in an overall structureless texture. Bivalve shells fragments of not-well-defined species also occur (white arrow).

Interpretation.

The general low- to high-energy sedimentary imprint recorded by Facies Bl, and the fossiliferous assemblage content suggest a depositional environment characterized by accumulation processes of variable energy, capable to transport 4-cm-large pebbles, but also to accumulate sands and silt in lamina-sets because of settling or low-energy traction currents. These characteristics concur to outline a coastal area protected from the open sea, such as a back-barrier lagoon (Ashley, 1988; Boothroyd et al., 1985; Flemming, 2012; Galloway and Hobday, 1996). This interpretation is supported by the organisms found in the sediments which indicate low salinity conditions and a moderate-energy habitat (e.g. Cerastoderma Glaucom). The occurrence of bimodal grain size may suggest an outer position of the lagoonal area, close to the inner sandy barrier which, as observed in modern environments, is sporadically reached by washover storm surges transporting coarser material during maximum run-up of the beach (Hennessy and Zarrillo, 1987).

Beach-barrier facies association – BB

This facies association occupies the uppermost stratigraphic interval of the stratigraphic succession investigated in the present study. It was documented in two lithofacies Wd and Bf in the subsurface, but these deposits are actually associated with other sediments, which are presently exposed in the surface, including eolian sand dunes, beachface, and shoreface sands.

Facies Wd: Washover deposits

Facies Wd was recognized in the borehole S3, at a depth comprised between −7.35 and −7 m. This facies consists of yellowish, well-sorted, medium-to-coarse sand, with millimeter-thick interbedded brown clays. Poorly sorted polygenic gravels, consisting of sub-rounded clasts up to 3 cm in diameter, also occur as well as fragments of bivalve shells (Figure 8e). The general texture of the deposit investigated is overall chaotic with no structures or clast orientation.

Interpretation.

The absence of sedimentary structures or other internal textures and the exceptional coarse grain size compared with other lithofacies suggest mass transport by high-energy flows, capable of collecting and transporting large amounts of clastic sediment of different grain size, and to accumulate them without any apparent selection or organization (Foster et al., 1991; Schwartz, 1982; Tuttle et al., 2004). This condition indicates washover processes possibly generated by storm surges outpassing a beach barrier and depositing sediments in a back-barrier basin (Hennessy and Zarrillo, 1987). Bivalve shells fragments and other detrital material support this interpretation.

Facies association Bf: Barrier flat

Facies Bf (Back-Barrier Flat) occurs in the uppermost interval of all the boreholes investigated, with the exception of the borehole S10, where it is absent. The average thickness ranges from a minimum 0.35 m in the borehole S3 to a maximum of 2.2 m in the borehole S1. Sediments, which develop on the underlying deposits on an erosional surface, consist of yellowish-brown, well-sorted, medium-to-fine sands, containing rounded pebbles up to 0.5 cm large, and an overall structureless texture. Bivalve shells fragments of not-well-defined species also occur (Figure 8f).

Interpretation.

Based on its relative stratigraphic position and on the physical continuity with adjacent modern deposits, Facies Bf is considered the sedimentary record of a barrier flat (Oertel, 1985, his Figure 6 at p. 11). This sub-environment usually occurs in the most internal side of a beach barrier and results from the deposition of sand deriving from landward-directed wind deflation or, in case of a narrow beach barrier, from storm wave washover (Oertel, 1985; Pierce, 1970). These sediments are usually structureless and are adjacent with other additional sub-environments, such as eolian sand dunes, backshore, foreshore, and shoreface. These deposits are currently exposed in a seaward position of the modern Lesina beach-barrier environment and, thus, they were not intercepted by our core stratigraphies.

AMS dating of the investigated Lesina stratigraphic interval

AMS dating was performed on five samples obtained from strategic stratigraphic intervals detected in the boreholes S1, S2, and S4. These boreholes were considered representative of the entire succession drilled in the area investigated, thanks to the good state of preservation of the extracted cores.

The oldest AMS age resulted from the sample 8229, obtained from the borehole S1 at a depth of −26 m (Table 2). This sample consists of structureless or indistinctly laminated silts belonging to the Facies Fp (Floodplain) . The analysis of this sample yielded a δ¹³ C content of −25.3‰, and a ¹⁴C conventional age of 20,070 ± 50 yr BP. Two similar age values were obtained from samples 8230 and 8231 from the borehole S4, which are made up of silts of Facies Bl (Back-barrier lagoon) and Fp (Floodplain). These sediments, collected at −5 m and −10 m, revealed δ¹³ C values of −26.7‰ and −26.8‰ and a ¹⁴C conventional age of 14,300 ± 40 and 13,700 ± 49 yr BP, respectively (Table 2). The first value was then not considered suitable, because it is affected by a strong error possibly because of the reworking, which usually characterizes outer lagoon environments adjacent to sea storm washovers. The two last samples were collected at −8 and −10 m of the borehole S2, from sands and silts belonging to the facies Tc (Tidal channel) and Bl (Back-barrier lagoon), respectively. They yielded a δ¹³ C of −26.7‰ and −26.8‰, with a ¹⁴C conventional age of 7770 ± 30 and 9000 ± 30 yr BP (Table 2).

Table 2.

Radiocarbon dating obtained from selected samples (see their stratigraphic position in Figure 2).

UGAMS	Well and sample depth (m)	Sediment grain size	δ¹³ C, ‰	¹⁴C age, yr BP	±
8229	S1, −26	Silt	−25.3	20,070	50
8230	S2, −8	Very fine sand	−26.7	7770	30
8231	S2, −10	Clay	−26.8	9000	30
8232	S4, −5	Silt	−25.7	14,300	40
8233	S4, −10	Silt	−25.4	13,700	40

Stratigraphic correlations and depositional system interpretation

The stratigraphic correlation obtained in the present study (Figure 9) is based on boreholes grouped in a restricted sector of the Lesina coastal area, corresponding with the westernmost modern beach barrier (see Figure 1c and inset in Figure 9). A wider stratigraphic framework of the subsurface area investigated was obtained by using other additional log stratigraphies available in the area, although not described with detail in this study. This reconstruction is provided in Figure 11.

Figure 9.

Cross-correlation panel obtained from the boreholes S1, S2, S3, and S4 (see the inset in the downright corner for the location). The sketch shows the occurrence of three stratigraphic intervals, sequentially corresponding with a lowermost, fully continental incised-valley fill (IVS), an intermediate transgressive tide-influenced systems tract (TST), and an uppermost wave-dominated highstand systems tract (HST).

The correlation panel of Figure 9 consists of ca. 500-m-long, landward-seaward-oriented cross-section, which displays the architectures reconstructed in the subsurface sector investigated. The section shows the occurrence of a salt dome, whose top was intercepted at a depth of −42 in the borehole S1 (Figure 9). This formation consists of crystalline gypsum with intercalations of black limestones and marls of late Triassic age (Refice et al., in press). These deposits are stratigraphically located at the base of a several-kilometers-thick Mesozoic sequence (Ricchetti et al., 1988). The origin of such dome was interpreted differently in the recent past, invoking diapirism, salt tectonics, and halokinesis. However, it acted as lateral confinement for the development of the Lesina system and represents the western limit of the area, which hosted the back-barrier tidal flat during the mid-Holocene.

Alluvial sediments belonging to the pre-LGM depositional sequence overlie the salt dome unconformably. Ricci Lucchi et al. (2006) intercepted this sequence in a borehole drilled ca. 4.5 km eastwards, in a comparable depth range. On top of this succession, the post-LGM sequence develops. It includes three main vertically stacked stratigraphic intervals, separated by two discontinuity surfaces. These intervals recorded three main depositional systems: (1) an alluvial plain, (2) a back-barrier tidal flat, and (3) a barrier island, which are vertically stacked along the uppermost 30-m-thick stratigraphic succession.

The late Pleistocene alluvial plain system

The lowermost stratigraphic interval includes continental deposits grouped in the facies association AP. These sediments, which mainly resemble fluvial channels, crevasse, and floodplain lithofacies belonging to an alluvial plain (see Table 1), are time-constrained between ca. 20,000 and 10,000 yr BP (see Table 2). The eustatic curve reconstructed for the central Mediterranean area during this time interval (Figure 10) shows a post-LGM dramatic sea-level rise, from −120 to −40 m with respect to the present-day sea level (e.g. Lambeck et al., 2011), with an average velocity of ca. 3 mm/yr (Antonioli and Silenzi, 2000). Stratigraphy-based, high-resolution studies on correlative upper Pleistocene–Holocene records were provided in a number of Italian coastal areas (e.g. Aguzzi et al., 2005, 2007; Amorosi et al., 2004, 2008a, 2008b; Amorosi and Milli, 2001; Bellotti et al., 1994, 1995; Massari et al., 2004; Milli et al., 2008; Rossi et al., 2011; Tropeano et al., 2013; Zecchin et al., 2009, among others). These reconstructions documented subsurface LGM valleys and interfluves formed after the riverine incision occurred during the previous lowstand, which were rapidly filled by bay-head deltas, estuarine, and alluvial plain deposits during the subsequent transgression, forming typical ‘IVS’ (e.g. Dalrymple et al., 1992).

Figure 10.

Relative sea-level curve of the last 20,000 years (from Lambeck et al., 2011). This time span corresponds with the age of the stratigraphic interval analyzed in the present study. Also, the main depositional systems interpreted from the cores were attributed to each interval of the curve. Note the process regime change from tide-influenced to wave-dominated, which occurred during the last 7–6000 years.

The lower stratigraphic interval (Figure 9) can be interpreted as the top of a last generation of IVSs filling a pre-existing topography. This reconstruction is consistent with the model provided by Ricci Lucchi et al. (2006) for the same area. With more detail, the interpreted core stratigraphies of this interval show the occurrence of aggrading fluvial channel fills, at a depth comprised between −32 and −22 m from the modern surface, passing upward to crevasse- and floodplain-dominated lithofacies (Figure 9). This different depositional style recorded in the same unit/system could reflect a first change in the alluvial process regime because of a dramatic increase in the rate of the relative sea-level rise that occurred between 14,000 and 10,000 yr BP (Figure 10). In fact, the response of alluvial and coastal plain environments to transgressive stages is usually a tendency to have more sediment trapped into the valleys, which corresponds to a general reduction in the riverine incision and to an increased floodplain fines aggradation (Cattaneo and Steel, 2003; Schumm, 1993; Shanley and McCabe, 1994; Wescott, 1993). The lowermost unit recognized in our stratigraphic panel shows a marked aggradation, which possibly corresponds to a more general back-stepping of alluvial facies at wider scale (Figure 11). Although not extensively intercepted in our core stratigraphies, the basal limit of this unit records a surface of subaerial exposure formed during the LGM stage and corresponding with the sequence boundary incised in the mid-Pleistocene sediments (Figure 11). This architectural style was recognized in a number of correlative successions detected along the same Adriatic coastline and accumulated during the last Quaternary Transgressive Systems Tract (i.e. the ‘post-LGM TST’), the age of which spans from about 18 ka to about 5.5 ka (e.g. Cattaneo and Trincardi, 1999). During the time interval encompassing the alluvial stratigraphic unit detected in our correlation, the eustatic sea level rose from ca. −120 m up to −40 m with respect to the present-day elevation (Figure 10). As studies based on the reconstruction of the LGM shelf geometry in the Adriatic Sea demonstrate (e.g. Ridente and Trincardi, 2005), the sea level was located ca. 50 km northwards of the study area. This explains the maintenance of fully continental sedimentary conditions in the lowermost stratigraphic interval, although it represents the precursor for the onset of a tide-influenced deposition on this coastal area.

Figure 11.

Reconstructed cross-section (see trace in Figure 1) showing the inferred depositional architectures across the Lesina coastal area. In this profile, additional boreholes were included. The section shows the occurrence of an older pre-LGM depositional sequence, which top surface, coinciding with a sequence boundary, represents the landscape surface during the LGM. The overlying sequence consists of basal IVS accumulated during the last 20,000 years. The full-colored interval represents the stratigraphic record of the transgressive tidal flat deposits, which evolve to the modern normal regressive barrier-island deposits. The salt dome in the right part is projected.

The mid-Holocene, back-barrier tidal flat

The overlying stratigraphic interval, which occurs between a depth of −2 and −10 m from the surface of modern exposure, includes the deposits grouped in the facies association BI (Table 1). They consist of dominant channelized sandbodies, intercalated with fines yielding abundant macro- and microfauna related to transitional, brackish, and shallow-marine environments. A tidal signature dominantly marks this stratigraphic interval in the sandy lithofacies, which are associated with tidal channels, salt marsh, lagoonal, and mud flat deposits separated from the open sea by discontinuous narrow barrier islands (Figure 12).

Figure 12.

Paleogeographic scenario of the Lesina coastal area reconstructed for the time span comprised between during the last ca. 6000 and 2000 years (the dotted red line indicates the present-day coast). Because the residual tidal influx enhanced after the end of the post-LGM transgression, this area underwent relevant tidal influences, resulting in the development of wide back-barrier tidal flats, salt marshes, and lagoons. Inlets, interrupting the narrow beach barrier, amplified flood-tidal currents entering the lagoon and accumulating deltaic deposits. Each of the most relevant environments is compared with a modern analogue.

This depositional system was superimposed on the pre-existing alluvial plain at circa 9000–8000 yr BP. This phase of deposition started during a period of very rapid sea-level rise (29 mm/yr – Antonioli and Silenzi, 2000) and continued for the next thousands of years with an average rate of sea level of 12 mm/yr. It is possible that the initial period of rapid sea-level rise may have acted as the forcing factor for an important process regime change, which induced a strong tidal dominance onto this coastal sector.

The sedimentary features documented in this unit indicate strong differences between this environment and the modern Lesina system. Tidal deposits confined in highly sinuous channels, mud flats, and marshes/lagoons are usually generated in back-barrier tidal flat, separated from the open sea by discontinuous and narrow beach barriers (Figure 12). Tidal inlets, which are a fundamental element in these systems (e.g. Flemming, 2012), where not detected in our subsurface dataset. However, their occurrence is ensured by the presence of tidal channels which, as in most of the modern similar environments, are generated by oscillating ebb- and flood-tidal currents flowing in connection with the open sea (Hughes, 2012).

In sequence-stratigraphic terms, the basal surface of this unit represents a transgressive tidal ravinement (Figure 11), which is usually the erosional surface formed during transgression after the landward migration of tidal channels onto underlying former coastal plain deposits (e.g. Reinson, 1992). The ensuing wave ravinement surface, which is because of the erosional effect of waves on coastal deposits, should occur at the base of the shoreface lithofacies (Figure 11).

The onset of the Lesina back-barrier tidal flat (Figure 12) started between 8000 and 7000 yr BP. Other similar case studies are from the barrier lagoon systems around many world coastlines (e.g. Duck and Da Silva, 2012) or, more regionally, in the Holocene record of some coastal plains of Italy (e.g. Amorosi and Milli, 2001; Bellotti et al., 1994, 1995). Raynal et al. (2009) documented similar synchronous settings for the Holocene Golfe de Lyon barrier islands. These barriers result from longshore progradation of sand spits from inherited topographic highs by East–West coastal drift carrying sand material from the Rhône River (Raynal et al., 2009). According to these authors, the closure of these lagoons began around 7100 cal yr BP, based on the age of the first lagoonal deposit, during the last stages of eustatic stabilization (Sabatier et al., 2010).

It has been widely reported that during marine transgressions, open shelves in basins with a shelf break (e.g. passive margins) experience a landward increase of the tidal action and a decrease in wave energy (Yoshida et al., 2007). As a consequence, coastal depositional systems can be significantly influenced by tidal processes, particularly in microtidal basins, within incised valleys or geographically confined shelf areas (Cattaneo and Steel, 2003; Porebski and Steel, 2006; Pugh, 1987; Shanley and McCabe, 1994).

This condition is favorable to generate elongate, shore-parallel barrier islands, which isolate wide coastal areas where tidal currents excavate sinuous channels also in a microtidal regime as the Mediterranean. A formidable modern analogue of a back-barrier tidal flat is represented by discrete parts of the present-day Venice Lagoon system, which is located along the same Adriatic coastline of the northern Italy. This system, which is considered a modern barrier island, still includes very active tidal channels associated with flats, marsh, and lagoonal areas with morphological features very similar to those reconstructed in our case study (see first left-hand panel in Figure 12). The preservation of such environments in a modern system until today is related to the unusual tidal amplification, which affects the northern Adriatic Sea because of the engulfment of this area and to a very shallow continental shelf.

The modern wave-dominated barrier island

The rate of sea-level change reduced at circa 5500 yr BP (Figure 10), and this stimulated the final process regime change along the Lesina coastal area. The stratigraphic succession investigated in the present study is closed at the top by a 1–2-m-thick stratigraphic interval, which is dominantly formed by well-sorted beach sands and gravels with no evident internal structures (Facies association Bf). This interval, interpreted as the landward environment of a beach-barrier complex (i.e. the ‘barrier flat’ according to Oertel, 1985), corresponds with the early stage of development of a modern beach barrier, which progressively closed the Lesina Lagoon during the last millennia (e.g. De Pippo et al., 2001; Gravina et al., 2005). The basal surface of this interval represents the mid-Holocene maximum flooding surface (Figure 11). The mid-Holocene sea-level stillstand thus favored the onset of a marked progradation tendency, which occurred through the construction of a series of eolian dune ridges (i.e. cheniers) expanding seaward of the beach barrier until its modern dimension. However, this stage marked an important modification in the processes dominating this coast, which evolved from a tide-influenced back-barrier tidal flat to a wave-dominated barrier-island system (Figure 12). As a consequence, the former tidal elements (i.e. channels, flats deltas) were progressively characterized by a reduced dynamics and definitively deactivated after the closure of a series of cheniers built from the combined action of the east-directed littoral drift and dominant waves. This process regime is that which nowadays governs the modern Lesina barrier-island system.

The modern Lesina barrier-island environments: Relicts of an ancient tide-influenced system?

The reconstruction provided in Figure 12 was based on the facies analysis of the subsurface lithofacies intercepted in the boreholes. In addition, evidences detectable from aerial photographs of the modern barrier island (Figure 13a) allowed us to identify possible associated environments, or parts of them, which are witnesses of an ancient tide-influenced regime.

Figure 13.

Aerial photographs of the modern Lesina coastal area (from Google Earth®). In (a), the location of the various panels is indicated. (b) Bird-view perspective of the western sector of the Lesina lagoon (seen from NW) showing dark elongated forms (c) interpretable as relict tidal channels developed on a former tidal flat lying under the modern lagoon. (d) Similar morphologies can be also noted in the eastern sector of the Lesina lagoon, associated with salt marshes. (e) Present-day Lesina western beach barrier. It can be divided into an internal and an external sector, based on the morphological differences that characterize the two sectors. This limit is interpreted as the physical signature of the important regime change that affected the Lesina coasts during the mid-Holocene. (f) Aerial view of the two westernmost fan-shaped bodies interpreted as flood-tidal deltas.

Muddy deposits characterize the present-day lagoon (Molinaroli et al., 2014), which superimposed on to the former, mid-Holocene tidal flat after the stabilization of the relative sea level and the ensuing progradation of the entire coastal sector until today. Conditions of fine-grained sediment deposition in environment usually characterized by low sediment accumulation rate implies a very good preservation potential for former underlying morphologies, including channels, interfluves, and so on.

The western sector of the lagoon hosts relict forms whose geometry and size can be associated with ancient tidal channels (Figure 13b). These highly sinuous incisions are connected, bifurcate, and often terminate with pinch-out geometries (Figure 13c), and may justify the depth anomalies detected in recent bathymetric surveys, which highlight values of 1.2 and 1.6 deeper than the rest of the modern lake (Molinaroli et al., 2014). Similar forms occur in the easternmost lagoon, where they are associated with salt marsh deposits (Figure 13d). These relict morphologies are possibly the remnants of tidal channels similar to the forms detected in the western sector but characterized by smaller dimensions. The sedimentary record of these tidal channels is represented by the facies Tr (see Table 1), which yields rhythmites of semi-diurnal tidal cycles.

Also, the modern beach-barrier complex shows relict forms which possibly recorded the change from tide-influenced to wave-dominated coastal dynamics of the area. This W-E-elongated sandbody (see Figure 13a) can be divided into an internal and an external sector, based on the different morphologies still preserved and visible from aerial photographs. The western beach barrier exhibits evidences for this division, today still preserved, thanks to a scarce anthropogenic influence (Figure 13e). The surface of the internal beach barrier is characterized by a series of forms, which resemble salt marsh and channel relict morphologies, whereas, separated by a marked limit (LPRC in Figure 13e), the external beach barrier shows a series of eolian dune ridges or cheniers aligned roughly parallel to the present-day coastline trend (Figure 13e). The eastern sector of the internal beach barrier also includes the fan-shaped bodies interpreted by previous authors as tsunami-driven washover fans (Gianfreda et al., 2001; Gravina et al., 2005; Mastronuzzi and Sansò, 2002a). Radiocarbon data indicate the fans get progressively younger from the westernmost Sant’Andrea (5th century BC), Foce Cauto (AD 493), to Casino La Torre (1627) in the east (Mastronuzzi and Sansò, 2012).

Based on our reconstruction, we suggest a different interpretative hypothesis for these deposits: these forms resemble the typical features of flood-tidal deltas, which widely develop in tide-influenced microtidal barrier islands (e.g. Oertel, 1985; Oertel et al., 1992).

Flood-tidal deltas are very common in barrier islands, as they consist of fan-shaped, landward-prograding bodies, which usually accumulate in lagoonal areas (Aubrey and Gaines, 1982; Fitzgerald et al., 1984; Hayes, 1980; Sha, 1990, among others). They result from the deposition of sediment transported by flood-driven tidal currents, which are amplified in their strength because of the constriction of the flow along narrow entrances (i.e. inlets) across beach barriers (Longhitano et al., 2010; Morales et al., 2001). According to Davis et al. (2003), flood-tidal deltas represent a primary sediment sink on barrier-island coasts and are among the most preservable depositional environments in the barrier-island systems.

In the Lesina internal beach barrier (Figure 13e), these evident fan-shaped bodies were possibly generated by the amplifying tidal influx into the back-barrier tidal flat during the late stage of sea-level rise, which occurred between 6000 and 2000 yr BP (see again Figure 10). Flood-tidal currents were capable to transport fine-grained sand and mud flowing diurnally through a series of ephemeral tidal inlets (see the reconstruction in Figure 12). This interpretation explains a number of observed features: (1) the progressive eastward migration of these forms through time is the response to the strong influence of the local littoral drift; the E-directed longshore transport caused the closure/deactivation of the oldest, and the opening/activation of newest of the several lagoonal entrances in the same direction, as documented in many modern and ancient analogues systems (e.g. Hubbard et al., 1979); (2) the general decrease of the size of these deltas toward the same direction may record the progressive reduction of the tidal power because of the onset of the sea-level stand, and the switch to wave-dominated coastal processes; (3) the occurrence of several relict channels and swamp areas on top of many of these forms (Figure 13f) suggest former tidal inlets, channels, and interfluves, which are typical elements in flood-tidal deltas prograding in a back-barrier lagoon (Oertel et al., 1992; see their Figure 2).

Therefore, the boundary separating the internal from the external beach barrier (LPRC in Figure 13e and f) can be considered as an important morphological marker that recorded the process regime transition, which changed the Lesina coastal area from a tide-influenced back-barrier tidal flat to a wave-dominated barrier island.

Conclusions

The Lesina system represents one of the modern barrier islands of the Mediterranean coasts. Its upper Pleistocene–Holocene subsurface stratigraphic record and the morphological features preserved in the present-day lagoon were documented and interpreted in the present study. They highlight important process regime changes that have affected the evolution of the Lesina coastal system during the Pleistocene–Holocene, particularly for the role of the tidal influence.

The stratigraphy of the Lesina subsurface reveals three main units, unconformably overlying the pre-LGM deposits and part of a Mesozoic salt dome, which acted as western margin for the coastal systems. Our AMS dating indicate an age of 20,000–10,000 yr BP for the deposits belonging to the lowermost unit. These sediments, which exhibit typical sedimentological features of an alluvial plain, buried pre-existing valleys and interfluves and evolve upward from coarse-grained fluvial channelbelt-dominated to fine-grained floodplain-dominated lithofacies. This vertical facies trend reveals a first process regime change, possibly because of an increase in the rate of sea-level rise that occurred between 12,000 and 10,000 yr BP.

The second younger stratigraphic unit is a 8- to 10-m-thick interval and exhibits a dominant tidal influence in the various composing sand-rich lithofacies. In particular, diffused tidal channellfill deposits bear semi-diurnal rhythmites, associated with tidal flat, marsh, and lagoonal muds. This facies association recorded the development of a back-barrier tidal flat, consisting of high-sinuosity channels separated by interfluves and lagoonal areas. This system developed starting from 8000 to 7000 yr BP, when this area underwent another important process regime change, from an alluvial-dominated to a tidal-dominated coast. Ebb-dominated tidal currents, enhanced by the late post-LGM transgression, shaped the coast until at least the Neolithic-Roman age. After this stage, a general slowing of the relative sea-level rise favored coastal progradation, and the Lesina system transited from a back-barrier tide-influenced flat to the modern wave-dominated barrier island.

The present-day Lesina system preserves distinctive relict morphologies, including sinuous channels in the westernmost and easternmost lagoon, salt marshes, and, possibly, different generations of flood-tidal deltas. In particular, these latter forms, which were differently interpreted in the past as tsunami-induced washover fans, possibly represent tidal deltas prograded into the Lesina tidal flat through inlets. Their occurrence, which is common during the late post-LGM transgression in many modern barrier islands, is another element in supporting the role of an important mid-Holocene tidal influence on the area.

The results of this study highlight the role of tidal-dominated process regime, which controlled the sedimentation mechanisms along many worldwide coastlines, including the Mediterranean, during the late post-LGM transgression. Facies- and morphology-based paleo-environmental interpretations of many sedimentary records detected in the same chronostratigraphic interval along the Holocene coastlines of the central Mediterranean should be thus more focused or revised, paying attention on the possible role that the tidal influx played on the sedimentary processes during sea-level rise late stages, especially in confined basins, engulfed coasts, or shallow-marine shelves.

Footnotes

Acknowledgements

This study includes data collected during the MSc thesis of R. Della Luna and the PhD project of A. Milone spent between 2011 and 2014 at the Basilicata University. The authors are grateful to the insightful comments of two anonymous reviewers.

Funding

This research was financially supported by Regione Basilicata funds - NEOGEO Project 2012-2014, to S.G. Longhitano. Borehole drilling was supported by Comune di Lesina during the project “Piano di Lottizzazione C3”, late 2008. Cores were kindly provided by Geoprospector S.r.l. to the University of Basilicata.

References

Aguzzi

Amorosi

Sarti

(2005) Stratigraphic architecture of Late Quaternary deposits in the lower Arno Plain (Tuscany, Italy). Geologica Romana 38: 1–10.

Aguzzi

Amorosi

Colalongo

. (2007) Late Quaternary climatic evolution of the Arno coastal plain (Western Tuscany, Italy) from subsurface data. Sedimentary Geology 202: 211–229.

Albani

Serandrei-Barbero

(1990) I foraminiferi della Laguna e del Golfo di Venezia. Memorie di Scienze Geologiche 42: 271–341.

Allen

Homewood

(1984) Evolution and mechanism of a Miocene tidal sandwave. Sedimentology 31: 63–81.

Amorosi

Milli

(2001) Late Quaternary depositional architecture of Po and Tevere river deltas (Italy) and worldwide comparison with coeval deltaic succession. Sedimentary Geology 144: 357–375.

Amorosi

Colalongo

Fiorini

. (2004) Palaeogeographic and palaeoclimatic evolution of the Po plain from 150 ky core records. Global and Planetary Change 40: 55–78.

Amorosi

Fontana

Antonioli

. (2008a). Post-LGM sedimentation and Holocene shoreline evolution in the NW Adriatic coastal area. GeoActa 7: 41–67.

Amorosi

Sarti

Rossi

. (2008b) Anatomy and sequence stratigraphy of the late Quaternary Arno valley fill (Tuscany, Italy). In: Amorosi

Haq

Sabato

(eds) Advances in Application of Sequence Stratigraphy in Italy (GeoActa Special Publications 1), pp. 55–66.

Antonioli

Silenzi

(2000) La risalita del mare nel corso dell’Olocene. In: Silenzi

(ed.) Mare e cambiamenti globali, aspetti scientifici e gestione del territorio. Rome: ICRAM, pp. 29–42.

10.

Archer

(1998) Hierarchy of controls on cyclic rhythmite deposition, Carboniferous basins of eastern and mid-continental USA. In: Alexander

Davis

Henry

(eds) Tidalites: Processes and Products (SEPM Special Publications 61), pp. 59–68.

11.

Ashley

(1988) The hydrodynamics and sedimentology of a back-barrier lagoon-salt marsh system, Great Sound, New Jersey. Marine Geology 82: 1–32.

12.

Aubrey

Gaines

Jr (1982) Rapid formation and degradation of barrier spits in areas with low rates of littoral drift. Marine Geology 49: 257–277.

13.

Bartholdy

(2012) Salt mash sedimentation. In: Davis

Jr Dalrymple

(eds) Principles of Tidal Sedimentology. London and New York: Springer, pp. 151–185.

14.

Bellotti

Carboni

Di Bella

. (1994) Benthic foraminiferal assemblages in the depositional sequence of the Tiber Delta. In: Matteucci

(ed.) Studies on Ecology and Palaeoecology of Benthic Communities (Bollettino della Società Paleontologica Italiana, Special Publications 2), pp. 29–40.

15.

Bellotti

Milli

Tortora

. (1995) Physical stratigraphy and sedimentology of the Late Pleistocene-Holocene Tiber Delta depositional sequence. Sedimentology 42: 617–634.

16.

Billi

Salvini

(2000) Sistemi di fratture associati a faglie in rocce carbonatiche: nuovi dati sull’evoluzione tettonica del Promontorio del Gargano. Bollettino della Società Geologica Italiana 119: 237–250.

17.

Billi

Gambini

Nicolai

. (2007) Tettonica neogenica-quaternaria del Gargano ed aree prospicienti. Rendiconti della Società Geologica Italiana 4: 146.

18.

Bird

(2008) Coastal Geomorphology: An Introduction. Chichester: John Wiley, 436 pp.

19.

Boenzi

Caldara

Pennetta

. (2006) Environmental aspects related to the physical evolution of some wetlands along the Adriatic coast of Apulia (Southern Italy): A review. Journal of Coastal Research 39: 170–175.

20.

Bonaduce

Ciampo

Masoli

(1975) Distribution of ostracods in the Adriatic Sea, vol. 40. Napoli: Pubblicazioni della Società Zoologica, 304 pp.

21.

Boothroyd

Friedrich

McGinn

(1985) Geology of microtidal coastal lagoons, Rhode Island. Marine Geology 63: 35–76.

22.

Boyd

Dalrymple

Zaitlin

(1992) Classification of clastic coastal depositional environments. Sedimentary Geology 80: 139–150.

23.

Breber

Cilenti

Scirocco

(2007) Eleven years monitoring of Lesina lagoon (South Italy) using a biotic index. Transitional Waters Bulletin 1: 77–82.

24.

Breber

Povilanskas

Armaitiene

(2008) Recent evolution of fishery and land reclamation in Curonian and Lesina lagoons. Hydrobiologia 611: 105–114.

25.

Bridge

(2003) Rivers and Floodplains: Forms, Processes, and Sedimentary Record. Oxford: Blackwell, 491 pp.

26.

Bridge

(2006) Fluvial facies models: Recent developments. In: Posamentier

Walker

(eds) Facies Models Revisited (SEPM Special Publications 84), pp. 85–170.

27.

Bristow

Skelly

Ethridge

(1999) Crevasse splays from the rapidly aggrading, sand-bed, braided Niobrara River, Nebraska: Effect of base-level rise. Sedimentology 46: 1029–1049.

28.

Brondi

Anselmi

Ferretti

(1976) Studio sulla dispersione dei sedimenti della piattaforma costiera compresa fra Termoli e Barletta mediante l’uso dei detriti della formazione delle ‘pietre nere’ come traccianti naturali. Bollettino della Società Geologica Italiana 95: 1347–1363.

29.

Cain

Mountney

(2009) Spatial and temporal evolution of a terminal fluvial fan system: The Permian Organ Rock Formation, South-East Utah, USA. Sedimentology 56: 1774–1800.

30.

Cattaneo

Steel

(2003) Transgressive deposits: A review of their variability. Earth-Science Reviews 62: 187–228.

31.

Cattaneo

Trincardi

(1999) The late-Quaternary transgressive record in the Adriatic Epicontinental Sea: Basin widening and facies partitioning. In: Bergman

Snedden

(eds) Isolated Shallow Marine Sand Bodies: Sequence Stratigraphic Analysis and Sedimentologic Interpretation (SEPM Special Publications 64), pp. 127–146.

32.

Collinson

(1996) Alluvial sediments. In: Reading

(ed.) Sedimentary Environments: Processes, Facies and Stratigraphy. Oxford: Blackwell Science, pp. 37–82.

33.

Colombera

Mountney

McCaffrey

(2013) A quantitative approach to fluvial facies models: Methods and example results. Sedimentology 60: 1526–1558.

34.

Cotecchia

Dai Pra

Magri

(1971) Sul Tirreniano della costa ionica salentina (Puglia). Datazione di un campione di coralli con il metodo del ²³⁰Th/²³⁴U. Geologia Applicata ed Idrogeologia 6: 105–112.

35.

Coughenour

Archer

Lacovara

(2009) Tides, tidalites, and secular changes in the Earth-Moon system. Earth-Science Reviews 97: 59–79.

36.

Cuda

Gravina

(1998) Il Musteriano del lago di Lesina. In: Cuda

Gravina

(eds) Atti XVII Convegno Nazionale sulla Preistoria, Protostoria e Storia della Daunia, San Severo, pp. 41–64.

37.

Daidu

(2013) Classifications, sedimentary features and facies associations of tidal flats. Journal of Palaeogeography 2: 66–80.

38.

Dai Pra

Stearns

(1977) Sul Tirreniano di Taranto. Datazioni su coralli con il metodo del ²³⁰Th/²³⁴U. Geologica Romana 16: 231–242.

39.

Dalrymple

Zaitlin

Boyd

(1992) Estuarine facies models: Conceptual basis and stratigraphic implications. Journal of Sedimentary Petrology 62: 1130–1146.

40.

D’Argenio

Ferreri

Weissert

. (2004) A multi-disciplinary approach to global correlation and geochronology. The Cretaceous shallow-water carbonates of Southern Appennines, Italy. In: D’Argenio

Fischer

Premoli Silva

. (eds) Cyclostratigraphy, Approaches and Case Histories (SEPM Special Publications 81), pp. 103–122.

41.

Davies

(1964) A morphogenic approach to world shorelines. Zeitschrift fur Geomorphologie 8: 127–142.

42.

Davis

(1994) Barriers of the Florida Gulf Peninsula. In: Davis

(ed.) Geology of Holocene Barrier Island Systems. Heidelberg: Springer, pp. 167–206.

43.

Davis

Jr Barnard

(2003) Morphodynamics of the barrier-inlet system, west-central Florida. Marine Geology 200: 77–101.

44.

Davis

Jr Cuffe

Kowalski

. (2003) Stratigraphic models for microtidal tidal deltas: Examples from the Florida Gulf coast. Marine Geology 200: 49–60.

45.

De Beaumont

(1845) Leçons de géologie pratique. Parigi: P. Bertrand.

46.

Del Gaudio

Pieri

(2000) Seismicity and seismic hazard of Apulia (Southern Italy). In: Abstract VI Workshop Italy-Romania, Bari, 9–12 May.

47.

De Martini

Burrato

Pantosti

. (2003) Identification of tsunami deposits and liquefaction features in the Gargano area (Italy): Paleoseismological implication. Annals of Geophysics 46: 883–902.

48.

De Pippo

Donadio

Pennetta

(2001) Morphological evolution of Lesina Lagoon (Southern Adriatic, Italy). Geografia Fisica e Dinamica Quaternaria 24: 29–41.

49.

Doglioni

Mongelli

Pieri

(1994) The Puglia uplift (SE Italy): An anomaly in the foreland of the Apenninic subduction due to buckling of a thick continental lithosphere. Tectonics 13: 1309–1321.

50.

Donnici

Serandrei-Barbero

(2002) The benthic foraminiferal communities of the Northern Adriatic continental shelf. Marine Micropaleontology 44: 93–123.

51.

Duck

Da Silva

(2012) Coastal lagoons and their evolution: A hydromorphological perspective. Estuarine, Coastal and Shelf Sciences 110: 2–14.

52.

Eisma

(1998) Intertidal Deposits: River Mouths, Tidal Flat and Coastal Lagoons. New York: CRC Press, 525 pp.

53.

Fabbrocini

Di Matteo

D’Adamo

(2008) Abra segmentum (mollusca: Pelecypoda) of the Lesina lagoon (Southern Adriatic coast, Italy): Observations on variations in the population in relation to the main environmental parameters. Transitory Waters Bulletin 1: 39–44.

54.

Ferrarin

Zaggia

Paschini

. (2014) Hydrological regime and renewal capacity of the micro-tidal Lesina Lagoon, Italy. Estuaries and Coasts 37: 79–93.

55.

Fidelibus

Gutièrrez

Spilotro

(2011) Human-induced hydrogeological changes and sinkholes in the coastal gypsum karst of Lesina Marina area (Foggia province, Italy). Engineering Geology 118: 1–19.

56.

Fisher

Nichols

Waltham

(2007) Unconfined flow deposits in distal sectors of fluvial distributary systems: Examples from the Miocene Luna and Huesca Systems, Northern Spain. Sedimentary Geology 195: 55–75.

57.

FitzGerald

Penland

Nummedal

(1984) Control of Barrier Island shape by inlet sediment bypassing: East Islands, West Germany. Marine Geology 60: 355–376.

58.

Flemming

(2002) Effects of climate and human interventions on the evolution of the Wadden Sea depositional system (Southern North Sea). In: Wefer

Berger

Behre

. (eds) Climate Development and History of the North Atlantic Realm. Berlin: Springer, pp. 399–413.

59.

Flemming

(2005) Tidal environments. In: Schwartz

(ed.) Encyclopedia of Coastal Science. Berlin: Springer, pp. 1180–1185.

60.

Flemming

(2012) Siliciclastic back-barrier tidal flats. In: Davis

Jr Dalrymple

(eds) Principles of Tidal Sedimentology. London and New York: Springer, pp. 231–267.

61.

Flemming

Davis

Jr (1994) Holocene evolution, morphodynamics and sedimentology of the Spiekeroog barrier island system (Southern North Sea). In: Flemming

Hertweck

(eds) Tidal Flats and Barrier Systems of Continental Europe: A Selected Overview (Senckenbergiana maritima 24). Frankfurt am Main: Senckenbergische Naturforschende Gesellschaft, pp. 117–155.

62.

Flemming

Ziegler

(1995) High-resolution grain size distribution patterns and textural trends in the back-barrier tidal flats of Spiekeroog Island (Southern North Sea). Senckenbergiana maritima 26: 1–24.

63.

Foster

IDL

Albon

Bardell

. (1991) High energy coastal sedimentary deposits and evaluation of depositional processes in southwest England. Earth, Surface, Processes and Landforms 16: 341–356.

64.

Galloway

Hobday

(1996) Terrigenous Clastic Depositional Systems: Applications to Fossil Fuel and Groundwater Resources. 2nd Edition: New York: Springer, 489 pp.

65.

Gianfreda

Mastronuzzi

Sansò

(2001) Impact of historical tsunamis on a sandy coastal barrier: An example from the northern Gargano coast, Southern Italy. Natural Hazards and Earth System Sciences 1: 213–219.

66.

Gilbert

(1885) The Topographic Features of Lake Shores (U.S. Geology Survey Annual Report 5: 65–123).

67.

Gravina

(1999) Alcuni insediamenti rurali fra basso Fortore e Gargano settentrionale. Note di tipografia. In: Gravina

(ed.) Atti XVII Convegno Nazionale sulla Preistoria, Protostoria e Storia della Daunia, San Severo, pp. 185–206.

68.

Gravina

Mastronuzzi

Sansò

(2005) Historical and prehistorical evolution of the Fortore River coastal plain and the Lesina Lake area (Southern Italy). Évolution holocène de la plain littorale du Fortore et de la lagune de Lesina (Italie du Sud). Méditerranée 1(2): 107–117.

69.

Hampton

Horton

(2007) Sheetflow fluvial processes in a rapidly subsiding basin, Altiplano plateau, Bolivia. Sedimentology 54: 1121–1148.

70.

Hayes

(1979) Barrier island morphology as a function of tidal and wave regime. In: Latherman

(ed.) Barrier Island from the Gulf of St. Lawrence to the Gulf of Mexico. New York: Academic Press, pp. 1–71.

71.

Hayes

(1980) General morphology and sediment patterns in tidal inlets. Sedimentary Geology 26: 139–156.

72.

Hearty

Dai Pra

(1992) The age and stratigraphy of Middle Pleistocene and younger deposits along the Gulf of Taranto (Southeast Italy). Journal of Coastal Research 8: 82–105.

73.

Hennessy

Zarrillo

(1987) The interrelation and distinction between flood-tidal delta and washover deposits in a transgressive barrier island. Marine Geology 78: 35–56.

74.

Holbrook

(2001) Origin, genetic interrelationships, and stratigraphy over the continuum of fluvial channel-form bounding surfaces: An illustration from Middle Cretaceous strata, Southeastern Colorado. Sedimentary Geology 124: 202–246.

75.

Hoyt

(1967) Barrier island formation. Geological Society of America Bulletin 78: 1125–1136.

76.

Hubbard

Oertel

Nummedal

(1979) The role of waves and tidal currents in the development of tidal inlet sedimentary structures and sand body geometry: Examples from North Carolina, South Carolina and Georgia. Journal of Sedimentary Petrology 49: 1073–1092.

77.

Hughes

(2012) Tidal channels on tidal flats and marshes. In: Davis

Jr Dalrymple

(eds) Principles of Tidal Sedimentology. London and New York: Springer, pp. 269–300.

78.

Jinliang

Zhongjie

(2008) Sedimentary facies of the Silurian tide-dominated paleo-estuary of the Tazhong area in the Tarim Basin. Petroleum Sciences 5: 95–104.

79.

Jones

Guion

Fulton

(1995) Sedimentology and its application within the UK opencast coal mining industry. In: Whateley

MKG

Spears

(eds) European Coal Geology. London: Geological Society (Special Publications 82), pp.115–136.

80.

Jones

(1977) A nested grid for a three-dimensional model of a tropical cyclone. Journal of the Atmospheric Sciences 34: 1528–1553.

81.

Kjerfve

(1994) Coastal lagoons. Elsevier Oceanography Series 60: 1–8.

82.

Kvale

Sowder

Hill

(1998) Modern and Ancient Tides: Poster and Explanatory Notes. Tulsa, OK and Bloomington, IN: Society for Sedimentary Geology (SEPM) and Indiana Geological Survey.

83.

Lambeck

Antonioli

Anzidei

. (2011) Sea level change along the Italian coast during the Holocene and projections for the future. Quaternary International 232: 250–257.

84.

Lewin

Macklin

Johnstone

(2005) Interpreting alluvial archives: Sedimentological factors in the British Holocene fluvial record. Quaternary Sciences Reviews 24: 1873–1889.

85.

Loeblich

Jr Tappan

(1987) Foraminiferal Genera and Their Classification. New York: Van Nostrand Reinhold Company, 970 pp.

86.

Longhitano

(2011) The record of tidal cycles in mixed silici-bioclastic deposits: Examples from small Plio-Pleistocene peripheral basins of the microtidal Central Mediterranean Sea. Sedimentology 58: 691–719.

87.

Longhitano

Mellere

Steel

. (2012) Tidal Depositional systems in the Rock Record: A review and new insights. In: Longhitano

Mellere

Ainsworth

(eds) Modern and Ancient Tidal Depositional Systems: Perspectives, Models and Signatures (Sedimentary Geology Special Issue 279), pp. 2–22.

88.

Longhitano

Sabato

Tropeano

. (2010) A mixed bioclastic–siliciclastic flood-tidal delta in a microtidal setting: Depositional architectures and hierarchical internal organization (Pliocene, Southern Apennine, Italy). Journal of Sedimentary Research 80: 36–53.

89.

McGee

(1890) Encroachment of the sea. Forum 9: 437–449.

90.

Madoni

(2007) Benthic ciliates in Adriatic Sea lagoons. European Journal of Protistology 42: 165–173.

91.

Massari

Rio

Serandrei Barbero

. (2004) The environment of Venice area in the past two million years. Palaeogeography, Palaeoclimatology, Palaeoecology 202: 273–308.

92.

Mastronuzzi

Sansò

(2002a) Holocene coastal dune development and environmental changes in Apulia (Southern Italy). Sedimentary Geology 150: 139–152.

93.

Mastronuzzi

Sansò

(2002b) Pleistocene sea-level changes, sapping processes and development of valley networks in the Apulia region (Southern Italy). Geomorphology 46: 19–34.

94.

Mastronuzzi

Sansò

(2012) The role of strong earthquakes and tsunami in the Late Holocene evolution of the Fortore River coastal plain (Apulia, Italy): A synthesis. Geomorphology 138: 89–99.

95.

Miall

(1985) Architectural-element analysis: A new method of facies analysis applied to fluvial deposits. Earth-Science Reviews 22: 261–308.

96.

Miall

(1996) The Geology of Fluvial Deposits. Berlin: Springer, 582 pp.

97.

Miall

Jones

(2003) Fluvial architecture of the Hawkesbury Sandstone (Triassic), near Sydney. Australia. Journal of Sedimentary Research 73: 531–545.

98.

Milli

Moscatelli

Palombo

. (2008) Incised valley, their filling and mammal fossil record: A case study from Middle-Upper Pleistocene deposits of the Roman Basin (Latium, Italy). In: Amorosi

Haq

Sabato

(eds) Advances in Application of Sequence Stratigraphy in Italy (GeoActa Special Publications 1), pp. 67–87.

99.

Mjøs

Walderhaug

Prestholm

(1993) Crevasse splay sandstone geometries in the Middle Jurassic Ravenscar Group of Yorkshire. In: Marzo

Puigdefábregas

(eds) Alluvial Sedimentation. Gent: International Association of Sedimentologists (Special Publications 17), pp. 167–184.

100.

Molinaroli

Sarretta

Ferrarin

. (2014) Sediment grain size and hydrodynamics in Mediterranean coastal lagoons: Integrated classification of abiotic parameters. Journal of the Earth System Sciences 123: 1097–1114.

101.

Morales

Borrego

Jiminez

. (2001) Morphostratigraphy of an ebb-tidal delta system associated with a large spit in the Piedras estuary mouth Huelva Coast, Southwestern Spain. Marine Geology 172: 225–241.

102.

Morsilli

Scirocco

(2000) Le lagune di Lesina e Varano (Promontorio del Gargano): introduzione alla geologia dei sistemi isola barriera-laguna. Verso il piano del parco. Le lagune di Lesina e Varano. Qualità ambientale e sviluppo sostenibile. In: Atti del convegno nazionale, Lesina, 11–12 Novembre.

103.

Nemec

Muszyński

(1982) Volcaniclastic alluvial aprons in the Tertiary of Sofia district (Bulgaria). Annales Societatis Geologorum Poloniae 52: 239–303.

104.

Nichols

(2005) Sedimentary evolution of the Lower Clair Group, Devonian, West of Shetland: Climate band sediment supply controls on fluvial, aeolian and lacustrine deposition. In: Dore

Vinning

(eds) Petroleum Geology: North-West Europe and Global Perspectives, Proceedings of the Sixth Petroleum Geology Conference. London: Geological Society, pp. 957–967.

105.

Nichols

(1989) Sediment accumulation rates and relative sea-level rise in lagoons. Marine Geology 88: 201–219.

106.

North

Davidson

(2012) Unconfined alluvial flow processes: Recognition and interpretation of their deposits, and the significance for palaeogeographic reconstructions. Earth-Science Reviews 111: 199–223.

107.

Oertel

(1985) The barrier island system. Marine Geology 63: 1–18.

108.

Oertel

Kearney

Leatherman

. (1989) Anatomy of a barrier platform: Outer Barrier Lagoon, Southern Delmarva Peninsula, Virginia. Marine Geology 88: 303–318.

109.

Oertel

Kraft

Kearney

. (1992) A rational theory for barrier-lagoon development. In: Fletcher CH and Wehmiller JF (eds) Quaternary Coasts of the United States: Marine and Lacustrine Systems (SEPM Special Publications 48), pp. 78–87.

110.

Olsen

(1989) Sandstone-body structures and ephemeral stream processes in the Dinosaur Canyon Member, Moenave Formation (Lower Jurassic), Utah, U.S.A. Sedimentary Geology 61: 207–221.

111.

Ortolani

Pagliuca

(1988) Il Gargano (Italia meridionale): un settore di ‘avampaese’ deformato tra le catene appenninica e dinarica. Memorie della Società Geologica Italiana 41: 1245–1252.

112.

Pacilio

(2000) La risorsa archeologica: gli scavi sull’isolotto di San Clemente. In: Scirocco

Murano

(eds) Verso il piano del parco. Le lagune di Lesina e Varano. Qualità ambientale e sviluppo sostenibile. Atti del convegno nazionale Lesina, 11–12 Novembre 2000, pp. 70–71.

113.

Patacca

Scandone

(2004) The 1627 Gargano earthquake (Southern Italy): Identification and characterization of the causative fault. Journal of Seismology 8: 259–273.

114.

Pierce

(1970) Tidal inlets and washover fans. Journal of Geology 78: 230–234.

115.

Pierce

Colquhoun

(1970) Holocene evolution of a portion of the North Carolina coast: Reply. Geological Society of America Bulletin 12: 3527–3528.

116.

Porebski

Steel

(2006) Deltas and sea-level change. Journal of Sedimentary Research 76: 1–14.

117.

Poulain

(2001) Adriatic Sea surface circulation as derived from drifter data between 1990 and 1999. Journal of Marine Systems 29: 3–32.

118.

Pugh

(1987) Tides, Surges and Mean Sea Level. Chichester and New York: Wiley, 472 pp.

119.

Raynal

Bouchette

Certain

. (2009) Control of alongshore-oriented sand spits on the dynamic of a wave-dominated coastal system (Holocene deposits, Northern Gulf of Lions, France). Marine Geology 264: 242–257.

120.

Refice

Pasquariello

Bovenga

. (in press) Investigating uplift in Lesina Marina (Southern Italy) with the aid of persistent scatterers SAR interferometry and in situ measurements. Environmental Earth Sciences.

121.

Reinson

(1992) Transgressive barrier island and estuarine systems. In: Walker

James

(eds) Facies Models. St. John’s: Geological Association of Canada, pp. 179–194.

122.

Ricchetti

Ciaranfi

Luperto Sinni

. (1988) Geodinamica ed evoluzione sedimentaria e tettonica dell’avampaese Apulo. Memorie della Società Geologica Italiana 41: 57–82.

123.

Ricci Lucchi

Fiorini

Colalongo

. (2006) Late-Quaternary paleoenvironmental evolution of Lesina lagoon (Southern Italy) from subsurface data. Sedimentary Geology 183: 1–13.

124.

Ridente

Trincardi

(2005) Pleistocene muddy forced-regression deposits on the Adriatic shelf: A comparison with prodelta deposits of the late Holocene highstand mud wedge. Marine Geology 222–223: 213–233.

125.

Rinaldo

Belluco

D’Alpeos

. (2004) Tidal networks: Form and function. In: Fangherazzi

Marani

Blum

(eds) The Ecogeomorphology of Tidal Marshes. Washington, DC: American Geophysical Union, pp. 75–91.

126.

Rossi

Amorosi

Sarti

. (2011) Influence of inherited topography on the Holocene sedimentary evolution of coastal systems: An example from Arno coastal plain (Tuscany, Italy). Geomorphology 135: 117–128.

127.

Ruiz

Gonzalez Regalado

Baceta

. (2000) Los ostrácodos actuales da la laguna de Venecia (NE de Italia). Geobios 33: 447–454.

128.

Sabatier

Dezileau

Barbier

. (2010) Late-Holocene evolution of a coastal lagoon in Gulf of Lions (South of France). Bulletin de la Societé Géologique Française 1: 27–36.

129.

Sánchez-Moya

Sopeña

Ramos

(1996) Infill architecture of a non-marine half-graben Triassic basin (Central Spain). Journal of Sedimentary Research 66: 1122–1136.

130.

Schumm

(1993) River response to baselevel change: Implications for sequence stratigraphy. Journal of Geology 101: 279–294.

131.

Schwartz

(1982) Beach process. In: Schwartz

(ed.) Encyclopedia of Peaches and Coastal Environments. Stroudsburg, PA: Hutchison Ross Publishing Company, pp. 153–157.

132.

Selli

(1962) Il Paleogene nel quadro della geologia dell’Italia meridionale. Memorie della Società Geologica Italiana 3: 737–790.

133.

Serandrei-Barbero

Albani

Favero

(1989) Distribuzione dei foraminiferi recenti nella laguna a Nord di Venezia. Bollettino della Società Geologica Italiana 108: 279–288.

134.

Serandrei-Barbero

Carbognin

Taroni

. (1999) Distribution of recent benthic foraminifera in the southern basin of the Venice lagoon (Italy): Statistical evaluation of taxa significance. Micropaleontology 45: 99–111.

135.

Sgarella

Moncharmont Zei

(1993) Benthic foraminifera of the Gulf of Naples (Italy): Systematics and autoecology. Bollettino della Società Paleontologica Italiana 32: 145–264.

136.

Sha

(1990) Preservation potential of ebb-tidal delta and tidal inlets systems in response to sea level rise: Examples from the Dutch Wadden Sea. In: Sha

(ed.) Sedimentological studies of the ebb-tidal delta along the West Friesian Islands the Netherlands (Geological Ultraiectina No. 64). Utrecht: Instituut voor Aardwetenschappen der Rijksuniversiteit te Utrecht.

137.

Shanley

McCabe

(1994) Perspectives on the sequence stratigraphy of continental strata. American Association of Petroleum Geologists Bulletin 78: 544–568.

138.

Shepard

(1963) 35000 years of sea level. In: Clement

(ed.) Essay in Marine Geology. Los Angeles, CA: University of Southern California Press, pp. 1–10.

139.

Steel

Plink-Bjorklund

Ashoff

(2012) Tidal deposits of the Campanian Western Interior Seaway, Wyoming, Utah and Colorado, USA. In: Davis

Jr Dalrymple

(eds) Principles of Tidal Sedimentology. London and New York: Springer, pp. 437–471.

140.

Storelli

Barone

Garofalo

. (2007) Metals and organochlorine compounds in eel (Anguilla anguilla) from the Lesina lagoon, Adriatic Sea (Italy). Food Chemistry 100: 1337–1341.

141.

Stutz

Pilkey

(2002) Global distribution and morphology of deltaic barrier island systems. Journal of Coastal Research 36: 694–707.

142.

Tessier

Gigot

(1998) A vertical record of different cyclicities: An example from the Miocene Marine Molasse of Digne (Haute Provence, France). Sedimentology 36: 767–776.

143.

Tinti

Piatanesi

(1996) Numerical simulations of the tsunami induced by the 1627 earthquake affecting Gargano, southern Italy. Journal of Geodynamics 2: 141–160.

144.

Tropeano

Cilumbriello

Sabato

. (2013) Surface and subsurface of the Metaponto Coastal Plain (Gulf of Taranto – Southern Italy): Present-day- vs LGM-landscape. Geomorphology 203: 115–131.

145.

Tuttle

Ruffman

Anderson

. (2004) Distinguishing tsunami deposits from storm deposits along the coast of northeastern North America: Lessons learned from the 17 1929 Grand Banks tsunami and the 1991 Halloween storm. Seismic Research Letters 75: 117–131.

146.

Wescott

(1993) Geomorphic thresholds and complex response of fluvial systems some implications for sequence stratigraphy. American Association of Petroleum Geologists Bulletin 77: 1208–1218.

147.

Yoshida

Steel

Dalrymple

(2007) Changes in depositional processes – An ingredient in a new generation of sequence-stratigraphic models. Journal of Sedimentary Research 77: 447–460.

148.

Zecchin

Brancolini

Tosi

. (2009) Anatomy of the Holocene succession of the southern Venice lagoon revealed by very high-resolution seismic data. Continental Shelf Research 29: 1343–1359.