Late-Quaternary paleoenvironmental evolution of Lesina lagoon (southern Italy) from subsurface data

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Sedimentary Geology

Late-Quaternary paleoenvironmental evolution of Lesina lagoon

(southern Italy) from subsurface data

Marianna Ricci Lucchi a,*, Flavia Fiorini b,

Maria Luisa Colalongo a, Pietro Vittorio Curzi c

a University of Bologna, Dipartimento di Scienze della Terra e Geologico-Ambientali, Via Zamboni 67, 40127 Bologna, Italyb Dalhousie University, Department of Earth Sciences, Halifax, NS B3H 4J1, Canada

c University of Bologna, Dipartimento di Ingegneria delle Strutture, dei Trasporti, delle Acque, del Rilevamento, del Territorio,

Viale Risorgimento 2, 40136 Bologna, Italy

Received 2 November 2004; received in revised form 1 September 2005; accepted 7 September 2005

Abstract

Integrated sedimentological and micropaleontological (foraminifers and ostracods) analyses of two 55 m long borehole cores

(S3 and S4) drilled in the subsurface of Lesina lagoon (Gargano promontory — Italy) has yielded a facies distribution characteristic

of alluvial, coastal and shallow-marine sediments. Stratigraphic correlation between the two cores, based on strong similarity in

facies distribution and AMS radiocarbon dates, indicates a Late Pleistocene to Holocene age of the sedimentary succession.

Two main depositional sequences were deposited during the last 60-ky. These sequences display poor preservation of lowstand

deposits and record two major transgressive pulses and subsequent sea-level highstands. The older sequence, unconformably

overlying a pedogenized alluvial unit, consists of paralic and marine units (dated by AMS radiocarbon at about 45–50,000 years

BP) that represent the landward migration of a barrier-lagoon system. These units are separated by a ravinement surface (RS1).

Above these tansgressive deposits, highstand deposition is characterised by progradation of the coastal sediments.

The younger sequence, overlying an unconformity of tectonic origin, is a 10 m-thick sedimentary body, consisting of fluvial

channel sediments overlain by transgressive–regressive deposits of Holocene age. A ravinement surface (RS2), truncating the

transgressive (lagoonal and back-barrier) deposits in core S4, indicates shoreface retreat and landward migration of the barrier/

lagoon system. The overlying beach, lagoon and alluvial deposits are the result of mid-Holocene highstand sedimentation and

coastal progradation.

D 2005 Elsevier B.V. All rights reserved.

Keywords: Lesina lagoon (Italy); Late Quaternary; Sea-level changes; Foraminifers; Ostracods

1. Introduction

The Late Quaternary evolution of several coastal and

deltaic systems in the Mediterranean area has been

shown to be controlled mostly by relative sea-level

0037-0738/$ - see front matter D 2005 Elsevier B.V. All rights reserved.

doi:10.1016/j.sedgeo.2005.09.003

* Corresponding author. Fax: +39 51 2094522.

E-mail address: [email protected] (M. Ricci Lucchi).

changes (Oomkens, 1970; Coutellier and Stanley,

1987; Tesson et al., 1990, 1993; Gensous and Tesson,

1996, 1998; Somoza et al., 1998; Amorosi and Milli,

2001). In Italy, high-resolution stratigraphic studies of

the response of the coastal system to Late Quaternary

sea-level fluctuations, obtained from integrated sedi-

mentological and paleontological investigation of bore-

hole cores, have been carried out mainly in the Venice

Lagoon (Massari et al., 2004), in the Po Plain (Amorosi

183 (2006) 1–13

M. Ricci Lucchi et al. / Sedimentary Geology 183 (2006) 1–132

et al., 1999a,b, 2004), in the Tevere delta (Bellotti et al.,

1994; Amorosi and Milli, 2001), and the Ombrone river

plain (Carboni et al., 2002).

To develop a better understanding of the local effects

of past sea-level changes along the Adriatic coast, more

data are required, especially from the southern Adriatic

area, where very few data are available at present. The

Adriatic coast of Apulia, for instance, is marked by

several marine terraces and by undifferentiated strati-

graphic units of uncertain age. Morphological and geo-

logical studies in this area (see Mastronuzzi and Sanso,

2002a,b and references therein), integrated with abso-

lute age determinations through racemization methods,

have attempted to reconstruct the various phases of

coastal evolution.

The major purpose of this paper is to present new

data on the Late Quaternary evolution of the southern

Adriatic coast, through investigation of the subsurface

sedimentary record. In fact, although geomorphological

evidence can provide useful insights into the past en-

vironmental conditions, a more detailed imprint of

events during the Quaternary can be gained from the

Fig. 1. Location of Lesina lagoon with positio

sedimentary record, which shows good preservation in

the subsurface.

The presence of two lakes (Lesina and Varano, Fig.

1) along the northern coast of the Gargano promontory

offered the chance to preserve lengthy sequences of

virtually undisturbed deposits that can be used for

paleoenvironmental investigations. In particular, our

work is based on integrated sedimentological and

micropaleontological (foraminifers, ostracods) analysis

of two borehole cores from the Lesina lagoon (Fig. 1),

together with radiocarbon dating. Changes in frequency

and distribution of benthic foraminifers and ostracods

play a key role in facies characterisation, and in estab-

lishing the link between sedimentary evolution and Late

Quaternary sea-level fluctuations. In particular, benthic

foraminifers and ostracods occur abundantly in paralic

and marginal marine depositional systems, whereas

ostracods are recorded also in lacustrine and swamp

sediments. Their occurrences and distributions are

strongly linked to environmental parameters, such as

water depth, salinity and type of substrate, and are very

useful for interpreting the complexity of subenviron-

n of the cores mentioned in this paper.

M. Ricci Lucchi et al. / Sedimentary Geology 183 (2006) 1–13 3

ments and microenvironments that characterise margin-

al marine systems and reflect sea-level fluctuations.

2. Site description

Lesina lagoon is located in the southern Adriatic

coast (Apulia region, Italy) on the northern side of

the Gargano promontory (41.888N; 15.458E; Fig. 1).The lagoon, separated from the Adriatic Sea by a 1–

2 km wide beach ridge, extends East–West for about

22 km and is 3 km wide. The average water depth is

0.8 m, while the maximum depth is less than 2 m.

Two channels connect the lagoon to the sea, and

freshwater inflow is ensured by several small rivers

(Fig. 1).

Lesina is an eutrophic lagoon and exhibits strong

seasonal variations of temperature (ranging from 7 8Cin winter to 26 8C in summer) and salinity (between

11 and 34 psu). Moreover, the western part generally

exhibits higher salinity values than the eastern area.

Fig. 2. Geological sketch map of Apulian regio

The low tidal range of southern Adriatic Sea, com-

bined with the moderate freshwater input and the low

efficiency of water exchanges with the sea, suggest that

the hydrological balance in the Lesina lagoon is strongly

affected by atmospheric conditions.

3. Geological and geomorphological setting

The Gargano promontory is the most uplifted area

(1050 m a.s.l.) of the Apulian region, which represents

the foreland of both the Apenninic (to the West) and

Dinaric (to the East) orogens (Fig. 1). The Apulian

foreland (Fig. 2) is made up of a Precambrian crystalline

basement and a 6 km thick Mesozoic sedimentary cover.

This cover comprises a continental Permo-Triassic suc-

cession (fluvio-deltaic terrigenous facies, Verrucano),

overlain by 1 km thick anhydrite–dolomitic Triassic

successions (Burano Anhydrite) and 3–5 km thick Ju-

rassic–Cretaceous carbonate platform sediments. This

succession is capped by thin, discontinuous Tertiary

n (after Mastronuzzi and Sanso, 2002a).


and Quaternary deposits (Ricchetti et al., 1988; Doglioni

et al., 1994).

At the Gargano promontory, late Pliocene–Pleisto-

cene calcarenites unconformably overlie the Mesozoic

carbonate platform sequence. These deposits are

crossed by numerous faults with E–W, WNW–ESE

and NW–SE orientation.

From the Middle Pleistocene onwards, the superposi-

tion of regional uplift and glacio-eustatic sea-level

changes produced a number of marine-terrace deposits,

often associated with aeolianites, along the Apulian coast

(Mastronuzzi and Sanso, 2002a,b). The oldest marine-

terrace deposits contain volcanic products of Monte

Vulture, a volcano that was active in Middle Pleisto-

cene. The youngest deposits are of Tyrrhenian age

(Cotecchia et al., 1971; Dai Pra and Stearns, 1977;

Hearthy and Dai Pra, 1992).

Three main Holocene aeolian units are recognised

along the southern Adriatic Apulian coasts by Mas-

tronuzzi and Sanso (2002a). A mid-Holocene dune

belt formed by beach progradation during a relative

sea-level highstand. A second dune belt developed

mostly about 2500 years BP. During this time of

general coastal plain progradation, the Fortore River

(Fig. 1) created a cuspate delta and its sediments,

being transported by long-shore current, fed the spits

which definitely closed, in Roman times, the Lesina

lagoon first and then Varano Lake (Fig. 1). A third

discontinuous aeolian belt was deposited during me-

dieval times.

A detailed Upper Quaternary stratigraphy of the

Adriatic subsurface near Gargano Promontory has

been recently reconstructed by Ridente and Trincardi

(2002) and Cattaneo et al. (2003).

4. Material and methods

Two 55 m long borehole cores (S3 and S4) were

collected with a wireline system and sediment samples

stored in plastic liners.

Core S4 is located on the beach ridge between the

Adriatic Sea and Lesina lagoon, whereas core S3 is

on the opposite and landward side of the lagoon

(Fig. 1).

Several sedimentary features (colour, texture, struc-

tures, lamination) and the type and concentration of

accessory materials (including paleosols, plant frag-

ments and organic matter) were used to identify major

facies associations.

Eighty-four sediment samples about 2 cm thick were

taken for micropaleontological study. Positions of the

samples in the cores are shown in Fig. 3. Samples were

labelled with a number that corresponds to the distance

(in metres) from the top of the cores.

The samples were dried in an oven (at about 60

8C), sieved through a 63 Am mesh and dried again.

Benthic foraminifers and ostracods were studied in

order to provide additional data for paleoenvironmen-

tal interpretation. Identifications relied mainly upon

original descriptions and also works by AGIP

(1982), Cimerman and Langer (1991), Sgarrella and

Moncharmont Zei (1993), Yassini and Jones (1995)

and Hayward et al. (1999), Guernet et al. (2003).

Paleoenvironmental interpretation of foraminifer and

ostracod associations was based upon comparison of the

analysed microfauna with recent foraminifers and ostra-

cods described in several studies from the Mediterra-

nean area: Colalongo (1969), von Daniels (1970),

Bonaduce et al. (1975), Albani and Serandrei Barbero

(1982, 1990), Bizon and Bizon (1984), Venec-Peyre

(1984), Jorissen (1987, 1988), Albani et al. (1991),

Murray (1991), Sgarrella and Moncharmont Zei

(1993), Bellotti et al. (1994), Coppa et al. (1994), Masoli

et al. (1995), Melis et al. (1995), Montenegro and Pug-

liese (1995, 1996), Donnici and Serandrei Barbero

(2002) and Samir et al. (2003). Microfaunistic associa-

tions similar to those described in this paper have been

found also in Quaternary subsurface deposits of the Po

Plain (Fiorini and Vaiani, 2001; Amorosi et al., 2004;

Fiorini, 2004) and Tevere delta.

Two mollusc samples were collected for AMS 14C

dating: at 12.36 m depth in core S3, and at 27.47 m

depth in core S4. Dating was carried out by the Na-

tional Ocean Sciences AMS (NOSAMS) of the Woods

Hole Oceanographic Institution, Woods Hole, MA

(USA).

5. Sedimentology and micropaleontology

Lihological features and micropaleontological con-

tent provide the basis for detailed facies characterisa-

tion of the sediment cores. 21 different lithofacies

were identified and grouped into 8 facies associations,

as shown in Table 1. Among these, three are related to

sedimentary environments developing in the back-bar-

rier zone: lagoons, swamps and back-barrier beaches

(Fig. 3). Within the lagoon facies association, slight

paleoenvironmental differences, from inner to open

lagoon/bay, were identified by foraminifer and ostra-

cod assemblages. A 10 m thick bedset of fluvial

channel deposits, occurring in core S4 only, represents

the main distinctive element between the two cores.

Stratigraphy of both cores is described in ascending

order.

Fig. 3. Lithology, micropaleontology (foraminifers and ostracods), facies associations and sequence stratigraphic interpretation of cores S3 and S4.

SB1: sequence boundary of the post-Tyrrhenian depositional sequence, TS1: post-Tyrrhenian transgressive surface, RS1: post-Tyrrhenian ravine-

ment surface, SB2: sequence boundary of the Last Glacial to Holocene depositional sequence, TS2: Holocene transgressive surface, RS2: Holocene

ravinement surface, LST: lowstand systems tract, TST: transgressive systems tract, HST: highstand systems tract, IVF: incised-valley fill. Position

of the maximum flooding surfaces (MFS) is approximate.


Table 1

Description and nomenclature of the lithofacies encountered in the Lesina lagoon boreholes

Code Lithofacies description Fauna and accesory features Depositional setting Facies association

A1 Light grey/yellowish brown silty

clays

Scattered reworked benthic and

planktie foraminifers; carbonate

nodules

Flood plain Alluvial plain

A2 Red/brown silts locally overlain by

organic-rich silts clays

Iron–manganese oxides Paleosols

A3 Coarse to fine-grained sands, silty

sands and silts, yellowish brown in

colour, fining upward, with sharp or

cemented bases

Crevasse channels

A4 Quarzose, well-sorted,

medium-grained sands

Channel fill

A5 Laminated calcareous silts Freshwater ostracods; cementation Lake

A6 Brownish silts Vegetal debris, carbonate nodules,

iron–manganese oxides

Emerged floodplain

P Black/brown (organic) clays/silty

clays

Mollusc shell fragments; freshwater

ostracods (Candona spp.); wood

fragments; organic-rich horizons,

peats; Chara oogones

Freshwater ponds Swamp

L1 Light grey/white, calcareous, silts and

sandy silts

Mollusc shell fragments; brackish

ostracods (Cyprideis torosa); rare

foraminifiers (Ammonia tepida and

A. Parkinsoniana); carbonate nodules

Inner lagoon Lagoon

L2 Light grey/white, calcareous,

fine-grained sands

Mollusc shell fragments; carbonate

nodules

Wind/wave reworking

at the lagoon floor

L3 Dark grey, calcareous sandy silts Mollusc shells; brackish ostracods

(Cyprideis torosa); high percentages

of Ammonia tepida and

A. Parkinsoniana, rare

Cribroelphidium spp. and small test

of Miliolinella spp.

Open lagoon/Bay

T1 Grey, calcareous, medium-grained

sands with erosive base

Many bivalve and gastropod shell

fragments; cementation

Lower shoreface,

transgressive sands

Transgressive lags

T2 Cemented calcareous intra-clasts with

erosive base

Gravel lag

M Dark grey silty clays Many bivalve macrofossils and

mollusc shell fragments; marine

ostracods (Loxoconcha stellifera,

L. romboidea, Xestoleberis spp.,

Callistocithere of C. flavidofusca,

C. adriatica and Loxoconcha

tumida); rich foraminiferal

association (Quinqueloculina

stelligera, Adelosina dubia

angulosa-striata, Pseudotriloculina

subgranulata, Quinqueloculina

subpolygona, Miliolinella elongate,

M. dilatata, Quinqueloculina

stelligera, Pseudotriloculina ef.

P. subgranulata, Ammonia tepida,

A. parkinsoniana, A. papillosa,

Cribroelphidium decipens,

C. politum, C. granosion, rare

Bolovina striatula and Nonion

depressuhon)

Shoreface/offshore

transition

Shallow marine

B1 Light brown silty sands Mollusc shell fragments;

brown-yellow oxidation colours;

arbonate nodules

Washover or flood-tidal

delta

Back-barrier beach

B2 Black silty sands Wood fragments; rounded pebbles of

variable size (2 to 8 cm)

Marsh


Table 1 (continued)

Code Lithofacies description Fauna and accesory features Depositional setting Facies association

S1 Fine to medium-grained, well sorted,

calcareous, grey sands, with sharp or

erosive base

Mollusc shell fragments;

brown-yellow oxidation colours;

carbonate nodules

Upper shoreface Beach ridge

S2 Medium-grained, well-sorted,

calcareous, grey sands with silty

lenses

Mollusc shell fragments; rare

brackish ostracods (Cyprideis torosa)

Backshore/lagoon

transition

C1 Medium-grained pebbly sands with

erosive base

Mollusc shell fragments; rounded

pebbles (1 cm size); brown-yellow

oxidation colours

Basal lag Fluvial channel

C2 Reddish/brown, medium-grained

sands

Iron–manganese oxides; carbonate

nodules; local cementation and

pedogenesis

Channel fill

C3 Calcareous silty sands Brown-yellow oxidation colours;

carbonate nodules

Channel abandonment


5.1. Core S3

Stratigraphy of core S3 includes 30 m of alluvial

plain deposits characterized mainly by fine-grained

floodplain facies (lithofacies A1), paleosols (lithofacies

A2) and rare FU sandy sequences (lithofacies A3),

interpreted as either the filling of crevasse channels

associated with a major river channel or the products

of sheet floods. The high frequency of red-mottled

paleosols in the lower part of the alluvial plain facies

association (Fig. 3) suggests an environment with a

good drainage and a fluctuating water-table that oxi-

dized the sediment layers. By contrast, the presence of

organic-rich sediments and immature paleosols in the

upper part of the interval indicates water-logged condi-

tions and the presence of reducing environments

(swamps or ponds). Channel-fill sands (lithofacies A4)

are found at the base of the core, overlain by a lacus-

trine deposit (lithofacies A5) marking the abandonment

of the channel.

A sharp surface (SB1=TS1 in Fig. 4) divides the

alluvial plain deposits from the overlying transgressive

deposits (TST; Fig. 3). These are represented by fine-

grained, calcareous lagoon sediments (lithofacies L1)

overlain by a transgressive sand sheet (lithofacies T1),

which reflects the landward migration of a barrier/la-

goon system by shoreface retreat during a transgressive

phase (see discussion). A ravinement surface (RS1) at

the base of these sands (Fig. 4) indicates rapid sea-level

rise, with erosion of upper shoreface sediments and

their deposition into a lower shoreface environment as

storm-generated beds. Upward transition from brackish

to open marine conditions (lithofacies M) is indicated

by both facies and microfaunal association changes

(Table 1), thus reflecting the maximum marine ingres-

sion. The overlying deposits consist of alternating la-

goon and swamp sediments (Fig. 3) that are cut at the

top by a sharp erosion surface (SB2), representing the

second major unconformity within this core. Above this

surface, beach ridge sands (lithofacies S1) are overlain

by a shallowing upward succession of lagoon, swamp,

and alluvial plain deposits.

5.2. Core S4

Stratigraphy of core S4 shows remarkable similarity

with that described in the previous section for core S3,

but some differences are noteworthy. The succession

includes just 9 m of alluvial plain deposits, mainly

represented by fine-grained floodplain sediments and

paleosols, overlain on a sharply defined surface (SB1 in

Fig. 3) by lagoon and shallow-marine deposits. The

latter are separated by a transgressive gravel lag (litho-

facies T2), consisting of calcareous intraclasts reworked

from the underlying lagoonal unit and concentrated at

the ravinement surface (RS1 in Fig. 3). The overlying

fine-grained shallow-marine sediments are character-

ized by a well diversified foraminiferal association

(Table 1), recording the maximum water depth across

the entire study succession. Beach-ridge sands (lithofa-

cies S1 and S2) and fine-grained lagoon/bay deposits

(lithofacies L1–L3) are observed above the shallow-

marine unit. These coastal deposits are truncated by a

strong erosion surface related to a major unconformity

(SB2 in Fig. 5). A 10 m-thick coarse-grained fluvial

channel unit lies above this surface. This facies associ-

ation has been recorded only in this core (see Fig. 3)

and is represented by a FU sequence interpreted as the

filling of a fluvial channel, with evidence of water-stage

fluctuations (cemented, pedogenized horizons in Table

1). In particular, the basal erosion surface and the

overlying pebbly sands (lithofacies C1) record winnow-

Fig. 4. Representative S3 core (depth: 10.50–21.00 m) photographs of

major facies associations and key surfaces for stratigraphic interpre-

tation of the post-Tyrrhenian depositional sequence. A: alluvial plain,

L: lagoon, T: transgressive sand sheet, M: shallow marine, P: swamp.

Note the sequence boundary SB1, coinciding with the transgressive

surface TS1, overlying a concretioned level of alluvial plain deposits

and the ravinement surface RS1 separating the transgressive deposits

(lagoon facies association and transgressive sand sheet).


ing of strong currents, whereas lithofacies C2 and C3

represent the filling and the abandonment of the chan-

nel, respectively. A thin, fine-grained lagoon deposit

caps this interval, recording a new marine ingression

and the ultimate stop of fluvial sedimentation. Continu-

ing transgression is indicated by deposition of wash-

over or flood-tidal delta sands (lithofacies B1)

alternating with marsh (lithofacies B2) and lagoon

sandy deposits, both occurring in a back-barrier envi-

ronment along the inner margin of a beach ridge (back-

barrier beach of Kraft, 1971). These deposits, not

recorded in core S3 probably owing to erosional trun-

cation, are overlain through a ravinement surface (RS2

in Fig. 5) by a transgressive winnowed lag (pebble layer

in Fig. 3), marking a disconformity due to shoreface

retreat during a rapid sea-level rise. The upper beach-

ridge sands are upper shoreface deposits of the present

beach–ridge complex, which was built in response to

progradation of the coastal plain during the Holocene

sea-level highstand.

6. Late-Quaternary stratigraphic architecture of

Lesina area

Detailed facies characterisation, based upon litholo-

gy and micropaleontology, together with two AMS

radiocarbon ages, allow reconstruction of the deposi-

tional history of the Lesina lagoon area during the Late

Quaternary.

Two major depositional sequences, with well pre-

served transgressive (TST) and regressive highstand

(HST) deposits, but with poor preservation of lowstand

deposits (LST), are recorded in the study succession.

The two sequence-bounding unconformities are locally

coincident with the transgressive surfaces.

The lower sequence is recorded between 19.50 and

9.00 m in core S3, and between 41.30 and 19.00 m in

core S4 (Fig. 3). Stratigraphic correlations within this

sequence are based upon the strikingly similar facies

architecture observed in the cores and two radiocarbon

ages. Taking into account the wide range of error and

a possible hard-water effect, the two AMS radiocarbon

dates that have given back the ages of 50,900F1300

at 12.36 m in core S3 and 45,700F1100 at 27.47 m

in core S4, allow us to ascribe this lower depositional

sequence to a post-Tyrrhenian sea-level rise (Fig. 6).

The sequence boundary (SB1), also corresponding to

the transgressive surface TS1, is represented by a

sharp unconformity on alluvial plain deposits (LST).

These could be referred to either the Riss glacial

period (OIS 6 in Fig. 6), thus suggesting the occur-

rence of an important stratigraphic hiatus, or the

Wurm glacial period (OIS 4 in Fig. 6). The overlying

transgressive facies (TST) include lagoon, beach and

marine sediments, indicating the rapid landward mi-

gration of a barrier–lagoon system. Shoreface erosion

and retreat resulted in a pronounced ravinement sur-

face (RS1) with deposition of two different transgres-

sive lags: a lower shoreface sand sheet in core S3, and

an in-situ winnowed gravel lag in core S4. Shallow-

marine deposits, with micropaleontological evidence

of a maximum water depth of 20–30 m in core S4,

represent the peak of transgression. The following

Fig. 5. S4 core photographs (depth: 0.00–21.00 m) depicting the Last Glacial to Holocene depositional sequence. a) Note the transgressive surface

TS2 at the base of lagoon (facies association L) and back-barrier deposits (facies association B) of Holocene age, and the ravinement surface RS2

underlying regressive beach-ridge deposits (facies association S). b) This photo shows the thick fluvial-incised sands (facies association C)

overlying lagoon deposits of post-Tyrrhenian age by means of an erosion surface which correspond to the sequence boundary SB2 of the Last

Glacial to Holocene depositional sequence.

Fig. 6. Correlation of the two depositional sequences to the oxygen

isotope curve (after Martinson et al., 1987). The grey colour indicates

a possible major hiatus. OIS: oxygen isotope stages.


regression phase (HST) is marked by the basinward

migration of the depositional environments (Fig. 7).

Progradation of beach ridges at seaward locations

(core S4) and of a back-barrier lagoon landwards

(core S3) took place during this phase. Small-scale

paleoenvironmental variations are recognised by

means of microfaunal associations within the high-

stand lagoon facies association in core S4 (Fig. 3).

These are characterised by alternating brackish (inner

lagoon) and more open conditions (bay),

corresponding at landward locations (core S3) to

swamp and inner lagoon facies, respectively. These

small-scale sea-level oscillations can be related to

local subsidence or minor climatic changes during a

phase of slow relative sea-level rise or highstand (OIS

3 in Fig. 6).

A major problem in correlating the two cores is

represented by the presence, in core S4, of the 10 m

thick fluvial channel sands (facies association C) that

are lacking in core S3 (Fig. 3). This sedimentary

body, which overlies a pronounced erosion surface

truncating the highstand deposits of post-Tyrrhenian

age, in terms of sequence stratigraphy corresponds to

Fig. 7. Schematic reconstruction of the subsurface facies architecture of the Lesina lagoon during Late Quaternary. Abbreviations are defined in the

text and in previous figures.


an incised-valley fill (IVF)—see discussion in the

next section. The fluvial erosion surface in core S4 at

the base of the IVF is considered as the sequence

boundary of the upper depositional sequence (SB2).

Where IVF deposits are not recorded (core S3), SB2

corresponds also to the transgressive surface (TS2). The

lagoon/back-barrier transgressive deposits that overlie

TS2, as well as the overlying highstand regressive

deposits (Fig. 7) represented by a progradational stack-

ing pattern of beach-ridge, lagoon and alluvial plain

sediments, being located close to the ground surface,

can be assigned to the Holocene (OIS 1 in Fig. 7). As

reported by Mastronuzzi and Sanso (2002a), well-nour-

ished beaches, coastal lagoon and long dune belts

developed along the Adriatic coast of Apulia as a

consequence of coastal plain progradation during a

mid-Holocene sea-level highstand dated by 14C at

about 6000 years BP. At this time, Lesina lagoon started

being isolated by formation of successive beach ridges

in front of a bay. The SB2 unconformity thus matches a

long stratigraphic hiatus, only partially covered by

fluvial channel sedimentation in core S4, corresponding

to the Last Glacial period (OIS 2 in Fig. 6).

7. Major factors controlling sedimentation in the

Lesina lagoon

Our data show that the Late-Quaternary depositional

history of Lesina lagoon was affected by superposed

different factors, such as regional uplift, glacioeustatism

and local subsidence, which are difficult to disentangle.

The study area experienced intense tectonic activity in

the past. Uplift of the Gargano promontory (up to 1000

m high) began in Middle Pleistocene (Doglioni et al.,

1994) or even earlier, in Middle–Late Pliocene (Bertotti

et al., 1999; Chivoli et al., 2000). Since that time, the

Apulian region has been supposed to be characterised

by a constant, low rate of uplift (Dai Pra and Hearty,

1988; Cosentino and Ghiozzi, 1988; Bordoni and

Valensise, 1998). Recent studies, however, show evi-


dence of still active tectonics in the study area, as

documented by (i) tectonic reactivation of pre-existing

structures that have exerted a major control on Neogene

to Quaternary sedimentation (Chivoli et al., 2000), (ii)

rapid coseismic movements, which have been recorded

during the Late Holocene along the northern coast of

Gargano (Mastronuzzi and Sanso, 2002c), and (iii) high

seismicity of the Gargano area (Tinti et al., 1995; Del

Gaudio and Pierri, 2001; Del Gaudio et al., 2002).

Facies architecture within the studied succession

reveals that tectonics probably exerted a major control

in the formation of the two sequence boundaries (SB1

and SB2). In particular, by attributing the alluvial

deposits underlying SB1 to OIS 6 (Fig. 6), tectonics

could account for the lack of transgressive deposits of

Tyrrhenian age. Marine terraced deposits of Tyrrhenian

age have been only recognised along the Ionian Apu-

lian coast by a distinctive faunal assemblage containing

the index fossil Strombus bubonius Lmk (Cotecchia et

al., 1971; Dai Pra and Stearns, 1977; Hearthy and Dai

Pra, 1992; Bordoni and Valensise, 1998). In contrast,

marine terraces in the study area (southern Adriatic

coast of Apulia) have been generically referred to the

Middle–Late Pleistocene by Mastronuzzi and Sanso

(2002b). On the second hypothesis, accepting a more

recent, OIS 4 age for the lowstand continental deposits,

a significant contribution by glacioeustacy cannot be

excluded.

A major tectonic control on sequence development

can be also assumed for the lower boundary of the

overlying depositional sequence (SB2). Uplift in the

hinterland (Fig. 7) led to fluvial incision in the adjacent

areas, resulting in seaward tilting of the post-Tyrrhenian

sequence, and deposition of the IVF in the newly created

topographic low. This hypothesis can explain the differ-

ence in depth (about 20 m) at which TS1 and RS1

surfaces are encountered in core S3 and S4 (Fig. 3).

Despite an overall tectonic influence on sequence

boundary formation, a significant eustatic control on

internal facies architecture is testified to within both

sequences by an obvious transgressive–regressive ten-

dency. In particular, the upper sequence of Late Pleisto-

cene to Holocene age displays several features in

common with respect to the eustatically controlled coe-

val sequences of the Mediterranean area (Oomkens,

1970; Coutellier and Stanley, 1987; Somoza et al.,

1998; Amorosi et al., 1999a,b; Amorosi and Milli,

2001). In the lower part of the sequence, these include

the presence of incised-valley fluvial deposits, coupled

with the important stratigraphic hiatus recorded in the

interfluves. Similarly, the retrogradational stacking

pattern of barrier/lagoon sediments followed by pro-

gradation of a coastal plain can be related to the

Holocene sea-level rise and subsequent highstand,

thus suggesting a key role of eustacy on sedimentation

(Fig. 7).

8. Conclusions

Integrated sedimentological and micropaleontologi-

cal investigations of two 50 m-thick cores from the

subsurface of Lesina lagoon show a vertical cyclic

pattern of facies, including continental, paralic and

shallow-marine deposits. Particularly, the lower part

of the study succession is characterised by alluvial

plain sediments, locally pedogenized. In contrast, the

remaining part of the succession was formed in a

variety of depositional environments, from coastal

(swamp, lagoon, bay) to shallow marine.

Vertical distribution of facies associations and the

identification of important stratigraphic surfaces (se-

quence boundaries, transgressive and ravinement sur-

faces) allow us to distinguish two major depositional

sequences representing the last 60 ky. Deposition of

these sequences was controlled by both tectonic and

eustatism.

The older sequence, composed uniquely by trans-

gressive and highstand deposits, has been assigned to a

post-Tyrrhenian sea-level oscillation on the basis of two

radiocarbon dates. Sequence boundary (SB1) formation

can alternatively be considered to be controlled by

either tectonics or eustatism, depending on the age

attribution of the underlying lowstand deposits. Trans-

gressive deposits of this sequence represent the land-

ward migration of a barrier/lagoon system. Small-scale

sea-level changes within this system and the maximum

marine ingression have been distinguished by variations

in microfaunal content. Subsequent highstand deposi-

tion is represented by progradation of the coastal/la-

goon environments.

The overlying sequence of Late Pleistocene to Holo-

cene age displays two distinct phases of deposition. In

particular, formation of sequence boundary (SB2) and

deposition of the overlying incised-valley fluvial sands

have been interpreted to be controlled by tectonic activ-

ity. On the other hand, the upper part of the sequence,

consisting of beach ridge, lagoon and alluvial plain

deposits, can be referred to the Holocene sea-level rise

and highstand, thus enhancing the role of eustacy.

Acknowledgments

This work was supported by COFIN-MURST 1997

funds (coordinator: E. Rabbi). We are grateful to P.


Ferrieri for help in opening and photographing the

cores. Special thanks to A. Amorosi and F. Ricci Lucchi

for their helpful suggestions and careful reading of the

manuscript. We are also grateful to the anonymous

reviewers for their helpful suggestions, and to K.A.W.

Crook for editorial advice.

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