Stratigraphic architecture of Late Quaternary deposits in the lower Arno Plain (Tuscany, Italy)

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STRATIGRAPHIC ARCHITECTURE OF LATE QUATERNARY DEPOSITS IN THE LOWER ARNO PLAIN (TUSCANY, ITALY)

Margherita Aguzzi, Alessandro Amorosi & Giovanni Sarti**

*Dipartimento di Scienze della Terra e Geologico-Ambientali, Università di Bologna, Via Zamboni 67 - 40126 Bologna e-mail: amorosi@geomin.unibo.it

**Dipartimento di Scienze della Terra, Università di Pisa, Via Santa Maria 53 - I-56126 Pisa

INTRODUCTION

The Arno coastal plain, bounded by the Versilia coastal plain and Pisani Mountains to the north, and Pisa and Leghorn hills to the south (Fig. 1), constitutes the southern, inshore portion of the wider Viareggio Basin (Nagi & Pascucci, 2002), corresponding to the Pisa- Versilia Basin of Mazzanti (2000). This sedimentary basin represents the infill of a half-graben system (Mariani & Prato, 1988; Nagi & Pascucci, 2002) that formed along the Tyrrhenian margin since the Late Tortonian, in response to the opening of the Tyrrhenian Sea and the counter-clockwise migration of the chain- foredeep-foreland system (Malinverno & Ryan 1986;

Sartori, 1989; Patacca et al., 1990; Martini & Sagri, 1993; Meletti et al., 1995; Pascucci et al. 2001). The Pisa-Versilia Basin includes a remarkably thick (up to 3800 m) succession of Neogene to Quaternary deposits, which are subdivided into a series of seismo-stratigraphic sequences (Mariani & Prato, 1988; Nagi & Pascucci, 2002). The Pleistocene sequence, which is deeply fault- ed with the exception of its uppermost portion (Argnani et al., 1997), consists of two sub-units (sequences I and II of Mariani & Prato, 1988, and 6a and 6b of Nagi &

Pascucci, 2002).

The few studies available about subsurface stratigraphy of the Arno coastal plain have been finalized mostly to hydrogeological research (Baldacci et al., 1995;

Baldacci, 1999). The dataset includes almost exclusive- ly logs from boreholes drilled for water research purposes, with scarce detailed stratigraphic, sedimentological and chronologic information. Present knowledge of subsurface stratigraphy in the Arno coastal plain, thus, generally relies upon stratigraphic interpretations of poor- quality data, with scattered high-resolution stratigraphic

analyses only (Gioli, 1894; Trevisan & Tongiorgi, 1953;

Romagnoli, 1957; Mazzanti, 1983; Sartori, 1978;

Baldacci et al., 1995; Della Rocca et al., 1987; Marroni et al., 1990; Mazzanti, 1994; Federici & Mazzanti 1995;

Mazzanti, 2000).

An overall picture of subsurface stratigraphy in the Arno coastal plain has been provided by Fancelli et al.

(1986). On the basis of stratigraphic data from previously described boreholes (Ghelardoni et al., 1968), these authors subdivide the Quaternary succession of the Arno Plain into three tectono-stratigraphic units. The upper unit (substrato superiore), the age of which is younger than early Pleistocene, is made up of an alternation of fine-grained and coarse-grained sediments, which can be summarized, from bottom to top, as follows:

Shallow-marine clays and sands. This unit has been identified at Bigattiera (Sartori 1978) and Saint Gobain (Romagnoli, 1957) boreholes (Fig. 1), between 100 m and 86 m below sea level. It has been attributed to the early Pleistocene (Fancelli et al., 1986), although a middle Pleistocene age has been suggested by Della Rocca et al. (1987).

Arno and Serchio da Bientina conglomerates. This unit was first defined by Segre (1955), and has been interpreted to represent a lithologic marker-bed across the whole Arno coastal plain, for both stratigraphic and hydrogeologic purposes (Baldacci et al., 1995). Depth contours of the bottom of this lithostratigraphic unit, ranging between 15 and 145 m below sea level, depict a complex paleo-topography, suggesting the presence of an incised valley (Fancelli et al., 1986; Della Rocca et al., 1987). The Arno and Serchio da Bientina conglomerates have been correlated, for long time, to Würm II (Ghelardoni et al., 1968; Barsotti et al., 1974; Fancelli et al., 1986; Della Rocca et al., 1987; Federici & Mazzanti,

Geologica Romana 38 (2005), 1-10

ABSTRACT - Detailed sedimentological investigation of two continuously-cored boreholes, up to 106 m deep, combined with stratigraphic analysis of about 300 well logs performed for water research in the area between Cascina and the Tyrrhenian coast, reveal subsurface stratigraphy of Late Quaternary deposits in the lower Arno Plain.

Facies analysis of the cores allows identification of twelve different facies associations, grouped into alluvial and coastal depositional systems. A stratigraphic cross section, roughly parallel to present Arno River and 30 km long, shows the presence of two trangressive-regressive sequences, attributed to the last two interglacial-glacial cycles (base of OIS 1 and 5e, respectively). Despite significant facies variability from proximal to distal locations, the basal transgressive surfaces appear as the most readily identifiable features from both core and borehole data, and constitute a stratigraphic marker that can be physically traced across the entire study area.

The high resolution stratigraphic data shown in this paper are in marked contrast with previous work, and provide a new stratigraphic framework for the upper portion of the Viareggio Basin.

KEY WORDS: transgressive-regressive cycles, facies analysis, Late Quaternary, Viareggio Basin.

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1988; Marroni et al., 1990); only recently, an attribution to Würm I (OIS 4) has been proposed (Federici &

Mazzanti, 1995; Mazzanti, 2000).

Fluvial and swamp silts. These deposits, which over- lie the Arno and Serchio da Bientina conglomerates, have been related to a strong decrease of fluvial dis- charge (Della Rocca et al., 1987) that occurred during the late Würm II or OIS 3 (Mazzanti, 2000).

Isola di Coltano sands - Vicarello sands and silts.

These two units, interpreted as aeolian and fluvial deposits, respectively (Fancelli et al., 1986; Mazzanti, 2000), crop out locally in the present coastal plain. The occurrence in these sediments of musterian artifacts (Menichelli, 1984; Grifoni Cremonesi et al., 1995), indicating an age older than 40.000y. B.P., allows their attribution to the late Pleistocene (Marroni et al., 1990).

Recently, these units have been correlated to the Würm II - Würm I transition or OIS 3 (Federici & Mazzanti, 1995; Mazzanti, 2000).

Alluvial plain silts. This unit represents a significant portion of the present costal plain, with an average thickness of 30 m (Della Rocca et al., 1987). On the basis of pollen analyses, performed on continuous cores recovered near the city of Leghorn (Galletti Fancelli, 1978), these deposits have been attributed to the Holocene,

mostly between the Sub-Atlantic and the Boreal phase.

This chronologic attribution matches a radiocarbon age of 6659±153 y B.P., obtained in the same area, at 22 m depth (Ferrara et al., 1959).

North of Arno coastal plain, in the adjacent Versilia coastal plain (where the Versilian stage has been estab- lished - Blanc, 1942), despite the remarkable amount of stratigraphic studies available (Blanc, 1934; Marchetti &

Tongiorgi, 1936; Blanc et al. 1953; Broker et al., 1956, Tongiorgi, 1956; Ferrara et al., 1959; 1961; Alessio et al., 1964; Pandolfi, 1975; Valli, 1976; 1980; Federici, 1987; 1993; Federici & Mazzanti, 1995), detailed information about subsurface stratigraphy is scarce, with very few exceptions. One of these derives from core ENEA, 90 m long, recovered at Massaciuccoli lake (Antonioli et al., 1999; Nisi et al., 2003) (Figs. 1 and 2). Stratigraphic analysis of this core revealed two transgressive marine surfaces, at 34 m and 70 m depth respectively. The upper transgressive surface, dated to 10,4 ka B.P. (OIS 1), is attributable to the Holocene; on the basis of two

230Th/²³⁴U dates, providing an age between 129.5 and 132.8 ky B.P., the lower transgressive surface has been attributed to OIS 5e (Tyrrhenian). This implies, for the continental deposits between -34 and -70 m, an age assignment to OIS 4 to 2.

Fig. 1 - Geological sketch map of the study area, with indication of the section trace of Figure 4.

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A time-equivalent stratigraphic succession crops out along the Leghorn marine terrace (Bacci et al., 1939;

Barsotti et al., 1974; Mazzanti, 1983; Federici &

Mazzanti, 1988; Nisi et al., 2003), the inner margin of which is located 15 m above the present-day sea level.

This terrace was formed during the Tyrrhenian (OIS 5e) sea-level highstand (Ferranti et al., 2004), as confirmed by the presence of “Senegalese” fauna, with Strombus bubonius, in the basal calcarenite layers (panchina).

Recently, a detailed study of shallow continuously-cored boreholes, drilled on the Leghorn terrace (Dall’Antonia et al., 2004), has shown that Tyrrhenian deposits are under- lain by a marine succession of Santernian-Emilian age.

The major scope of this paper is to provide for the first time a detailed picture of late Quaternary subsurface stratigraphy in the lower Arno Plain, through integration of stratigraphic data from about 300 wells with a set of very high-resolution stratigraphic data deriving from two continuously-cored boreholes (M1 and S2 in Fig.

1), ranging in depth between 40 and 106 m, that were drilled in 2004 beneath present Arno river. Specific aim is to discuss the relationships between the new stratigraphic framework proposed in this paper and previous work.

STRATIGRAPHY OF LATE QUATERNARY DEPOSITS IN THE LOWER ARNO PLAIN

Facies Associations

The detailed sedimentological investigation of the two continuously-cored boreholes (Fig. 3) reveals that Late Quaternary deposits of the lower Arno Plain consist of a cyclic alternation of continental alluvial plain to shallow-marine deposits.

Five facies associations, including fluvial-channel, crevasse splay-levee, floodplain, swamp and lake deposits, were recognized within the alluvial plain depositional system. Fluvial-channel deposits consist of gravel- to sand-dominated sedimentary bodies, with strongly erosional bases and characteristic elementary fining- upward (FU) successions, about 4 m thick. This facies association is locally capped by organic-rich layers, marking phases of channel abandonment.

The crevasse splay/levee facies association, which is commonly intercalated to floodplain deposits, shows the rhythmical alternation, few cm thick (levee deposits), of silty-sand and silt. Crevasse splay deposits are characterized by isolated, fine- to medium grained sand bodies, up to 1 m thick, that commonly display gradational bases and sharp tops. Local CU (coarsening-upward) - FU trends may be observed.

The floodplain facies association consists predominantly of monotonous alternations, up to 10 m thick, of grey to yellowish clay and silt. Locally, clays are stiff and display calcareous nodules, rhizhoconcretions and terrestrial small gastropods, testifying phases of subaer- ial exposure.

STRATIGRAPHIC ARCHITECTURE OF LATE QUATERNARY ... Geologica Romana 38 (2005), 1-10 3

Fig. 2 - Stratigraphy of core ENEA (modified after Antonioli et al., 1999).

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Fig. 3 - Stratigraphic log and facies interpretation of the two cores analyzed in this paper (see Fig. 1, for location).

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Swamp deposits display organic-rich layers made up of bioturbated, dark-grey to black peaty clay and silt.

Freshwater gastropods, woods and leaves remains are frequently observed. This facies association attains a maximum thickness of 3 m. In core M1, swamp deposits are intercalated to thinly laminated clays, with perfect preservation of primary sedimentary structures, interpreted as lake deposits.

Coastal and shallow-marine deposits include a variety of facies associations formed in brackish to normal salinity waters.

Brackish-water deposits consist of soft dark-grey clay, with abundant Cerastoderma and Cerithium. Sand inter- calations, a few cm- to dm-thick, rich in wood fragments and plant debris (flood layers) or mollusc shells (storm layers), are commonly encountered. These layers generally display sharp bases and wave-rippled tops. This facies association is interpreted to have formed in lagoonal (core S2) or estuarine (core M1) environments, depending on the different paleogeography. Sand bodies at the boundary between this facies association and overlying beach deposits, a few dm to 3 m thick and with internal CU trends, are interpreted to have formed as flood-tidal delta or washover deposits. CU sandy successions, 2-3 m thick, at the boundary between brackish- water and freshwater deposits are interpreted as bay- head delta sands.

Among the marine facies associations, transgressive barrier and (regressive) beach barrier deposits consist of fine- to coarse-grained sand, with very abundant shell material. In particular, the beach-barrier sands are about 10 m thick and show well-developed CU tendencies (see core M1 in Fig. 3). Gravels may locally occur in the upper part of this facies association.

Offshore-transition deposits are characterized by grey silty clay, with common intercalation of sharp-based sand layers, generally a few cm thick, with rare marine molluscs. This facies association is transitional to offshore/prodelta deposits, which display only rare sand intercalations and abundant vegetal debris, testifying a significant fluvial influence.

Stratigraphy of cores M1 and S2

The vertical stacking of facies within the late Quaternary deposits of lower Arno Plain, from seaward to relatively landward locations, is best described by detailed stratigraphic analysis of cores M1 and S2 (Fig.

3).

Core M1

This core, 106 m long, has been recovered on the present Tyrrhenian coast, near Tirrenia (Fig. 1). The stratigraphic record at this location is characterized by the presence of two intervals with marine sedimentation, between 0-51 m and 90-101 m core depths, respectively (Fig. 3). These two units, which are bounded by two prominent transgressive surfaces (TS) are separated by

an approximately 40 m thick interval of alluvial plain deposits.

Above about 15 m of fine-grained estuarine/lagoonal clays, the upper marine deposits show a rapid deepen- ing-upward tendency, with vertical superposition of flood-tidal delta, transgressive barrier and offshore-transition deposits. The lower boundary of the transgressive barrier facies association is marked by an erosional- based veneer of mollusc shells (ravinement surface or RS in Fig. 3). The overlying regressive trend is documented by upward transition to a thick CU succession of beach-barrier sands.

The lower marine deposits are thinner, and dominated by a thick beach-barrier facies association that overlie, through a ravinement surface (RS), a thin transgressive suite of lagoonal and washover deposits.

The alluvial plain deposits located in-between are dominated by gravel and sand fluvial bodies, with subordinate floodplain clays. A thick interval of fine-grained, laminated deposits, attributed to a lake/swamp facies association can be identified between 72 and 63 m core depth.

Core S2

This core, 40 m long, has been drilled about 2 km SE of Pisa centre (Fig. 1) and 13 km NE of core M1. Unlike core M1, and consistently with its more landward location, core S2 does not include marine deposits, and consists predominantly of brackish-water (lagoonal) clays, alternating with organic-rich swamp deposits (Fig. 3).

Apart from recent floodplain deposits, it is remarkable the presence of two intervals of swamp and floodplain deposits (at depths of about 24 and 30 m), sandwiched between the lagoonal strata.

Given the moderate depth at which this borehole was drilled, core S2 is not long enough to reach the basal transgressive surface identified at about 50 m depth in core M1.

Subsurface Architecture

Stratigraphic correlation of cores M1 and S2 (Fig. 3), along with selected stratigraphic data from boreholes between the Tyrrhenian coast and Pontedera, allow the construction of a stratigraphic cross-section depicting subsurface stratigraphy in the lower Arno Plain (Fig. 4).

The two transgressive surfaces identified in core M1 (Fig. 3) constitute two major stratigraphic markers that can be physically traced from seaward to landward locations across the entire study area (Fig. 4). These surfaces, the orientation of which is roughly parallel to present topography, show a high correlation potential to the basin scale, being identifiable on the basis of the following cri- teria: i) abrupt facies change from continental (alluvial plain) to transgressive swamp (coastal plain), brackish- water (lagoonal/estuarine) or and shallow-marine deposits; ii) local presence, above the TSs, of peats, organic-rich clays and abundant mollusc shells; iii) occurrence, just below the TSs, of laterally extensive

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Fig. 4 - Subsurface stratigraphy of lower Arno Plain from integrated core and well data (see Fig. 1, for section trace).

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(sheet-like) fluvial-channel bodies or overconsolidated floodplain horizons.

Recognition of these two TSs across the entire lower Arno Plain results in identification of two transgressive-regressive cycles (T-R sequences in the sense of Embry, 1993; 1995) that thicken in seaward direction.

At seaward locations, the lower parts of these T-R sequences consist of coastal deposits. Maximum shoreline migration related to these two major transgressive pulsations is recorded at least 6 km inland of the present shoreline (see Cotoni well in Fig. 4), with scattered data (see well 6020 in Fig. 1) indicating an even greater (10 km) shoreline migration. At more landward locations, the basal nearshore deposits are laterally replaced by clay-dominated successions formed in brackish water environments. These deposits die away upstream over about 15 km, being replaced by an alluvial succession dominated by fine-grained alluvial deposits.

The coarse-grained fluvial deposits recognized in the lower parts of the T-R sequences are embedded within organic-rich and brackish-water deposits, suggesting their possible interpretation as fluvial-mouth (bay-head delta) deposits within a wave dominated estuarine envi- ronment (Amorosi & Milli, 2001). The local return to freshwater (coastal plain) conditions recorded at top of these coarse-grained bodies is probably related to a minor regressive pulsation within the overall transgressive trend. The upper, regressive, parts of the T-R sequences are characterized by an increasing proportion of alluvial deposits, with laterally-extensive fluvial- channel sedimentary bodies capping the sequences.

DISCUSSION

The stratigraphic framework reconstructed in the subsurface of lower Arno Plain shows strong similari- ties in terms of facies architecture with several works from coeval Quaternary successions of the Mediterranean area (see Amorosi & Milli, 2001, and references therein). Given the obvious physical expres- sion of the TSs in the study area, similarly to what recently reported by Amorosi & Colalongo (2005) from the late Quaternary deposits of the Po Basin, we sug- gest here a possible subdivision of the stratigraphic succession of the Arno coastal plain into two transgressive-regressive (T-R) sequences, instead of the depositional sequences of the classical EXXON models (Posamentier & Vail, 1988; Posamentier & Allen, 1999).

On the basis of their stratigraphic position, we are inclined to assign the upper T-R sequence to the Holocene (Oxygen Isotope Stage 1) and the lower boundary of the underlying T-R sequence to OIS 5e.

Unpublished pollen data from core M1 (M. Ricci Lucchi, pers. comm., 2004) document that both TSs are developed in coincidence of abrupt vertical changes in the type of vegetation, suggesting transition from glacial to interglacial conditions, and thus confirming the

relationships between Quaternary T-R sequences and interglacial-glacial cycles in the order of magnitude of 100 ky (Amorosi et al., 1999; 2004). Attribution of the lower TS to the Tyrrhenian (5e) transgression is fully consistent with data from the Versilian Plain (Antonioli et al., 1999) indicating, on the basis of Th/U dating, the presence of 5e deposits at 70 m depth (Fig. 2). As a consequence, the alluvial plain deposits comprised between the two intervals with marine deposits should be attributed to the last glacial period (OIS 4-2).

Concerning the uppermost T-R sequence, the very high thickness of Holocene sediments observed beneath the present Arno coastal plain appears to be related to a strongly erosional phase that preceded the onset of transgressive sedimentation in the study area.

Similarly to what documented on the Tyrrhenian margin for the Tevere delta (Bellotti et al., 1995; Milli, 1997), where the last post-glacial depositional sequence attains a maximum thickness of 80 m, the for- mation of an incised valley in response to sea-level fall could account for the anomalous high thickness of brackish-water deposits in the Arno River area. These should be interpreted as transgressive sediments formed in a wave-dominated estuary system during the early stages of sea-level rise (Dalrymple et al., 1992;

Nichol et al., 1994; Amorosi & Milli, 2001). Although the TS is likely to merge locally with the sequence boundary (SB), it appears as a more readily identifiable surface at the basin scale, especially where fluvial deposits belonging to the lowstand systems tract, and flooring the incised valley, are amalgamated with the underlying (falling-stage or even highstand) fluvial deposits, thus hampering a precise positioning of SB.

If compared with previous work, our data contrast markedly with published stratigraphic interpretations.

For instance, several doubts exist about the supposed Lower Middle Pleistocene chronological attribution of the “shallow-marine clays and sands” (Argille e sabbie di mare sottile) observed at Bigattiera and Saint Gobain boreholes, between 100 and 86 m core depth (Romagnoli, 1957; Sartori, 1978; Fancelli et al., 1986;

Della Rocca et al., 1987). The new data from core M1 shown in this paper confirm the presence of shallow- marine deposits at 90-100 m depth (Fig. 3), but our stratigraphic framework (Fig. 4) strongly suggests an age assignment of this interval to the marine ingression that occurred during the Last Interglacial (OIS 5e), i.e.

the late Pleistocene.

Discrepancies between our work and previously published papers are even greater when dealing with stratigraphic interpretation of the Arno and Serchio da Bientina conglomerates (Trevisan & Tongiorgi, 1953;

Segre, 1955; Baldacci et al., 1995; Della Rocca et al., 1987), a supposed hydrogeological and stratigraphic marker horizon extending from Pontedera to the coastal area (Fancelli et al., 1986), and ranging in depth between 15 and 145 m. On the basis of Fancelli et al.

(1986) interpretations, this gravel body seems to correspond in core M1 with the laterally extensive fluvial-

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channel body encountered 50-60 m below sea level (Fig. 4). If we consider, however, the depth at which the same sedimentary body should be encountered at more landward locations according to the map of Fancelli et al. (1986), i.e. at about 90 m depth at Bigattiera and 145 m depth at Cotoni, and compare these data with the correlation panel of Figure 4, it is readily apparent that previous authors have conducted an erroneous stratigraphic correlation of sedimentary bodies located, in fact, at significantly different stratigraphic levels. In previous studies (Federici & Mazzanti 1995; Mazzanti, 2000), the Arno and Serchio da Bientina conglomerates have been assigned to OIS 4. We have documented that this marker bed is inexistent; by contrast, we retain highly plausible the attribution of the laterally extensive fluvial body below the Holocene transgressive surface to the last glacial maximum (OIS 2).

Because of confusing stratigraphic position of the Arno and Serchio da Bientina conglomerates, the attribution of several related lithostratigraphic units becomes uncertain. For instance, the Fluvial and swamp silts (Limi fluvio-palustri di sottosuolo) may correspond to the Holocene in the case of core M1 or, alternatively, to older stratigraphic levels (see, for example, Bigattiera borehole), while the lithologic equivalents of the Isola di Coltano sands - Vicarello sands and silts (Sabbie eoliche dell’Isola di Coltano and Sabbie e limi di Vicarello) have not been detected in core M1. Finally, the Alluvial plain silts (Limi fluvio- palustri di superficie) described in Galletti Fancelli et al. (1978) can be related to the late Holocene deposits identified in core M1, similarly to Unit 7 of Dall’Antonia et al. (2004).

CONCLUSIONS

The detailed study of the uppermost Late Quaternary deposits of lower Arno Plain shows that a modern sedimentological and stratigraphic approach to the analysis of poor-quality borehole data, integrated with new high- resolution core data, may serve efficiently to the construction of a reliable stratigraphic framework to the basin scale.

Stratigraphic architecture of lower Arno Plain consists of two transgressive-regressive (T-R) sequences that are attributed to the last two interglacial-glacial cycles.

Lower parts of these T-R sequences are related to the major transgressive pulsations that took place at the onset of OIS 1 and 5e, respectively.

The transgressive surfaces are the most readily identifiable surfaces for sequence-stratigraphic interpretation.

These marker horizons can: i) mark abrupt facies changes from continental to coastal deposits, ii) be over- lain by transgressive, organic-rich deposits, or iii) overlie laterally extensive fluvial-channel bodies or overconsolidated floodplain clays, formed mostly at lowstand/

falling stage conditions.

The new stratigraphic framework shown in this paper is in contrast with most of previous stratigraphic and chronologic attributions. Particularly, the remarkable differences in terms of stratigraphic correlations and geometry of sedimentary bodies with respect to previous work should be taken into account when attempting a correct estimate of potential water resources.

ACKNOWLEDGEMENTS - We are indebted to Dr. Testa (Provincia di Pisa) for providing access to core S2. Manuscript benefited from comments of reviewers P. Bellotti and S. Milli.

Alessio M., Bella F., Cortesi C. (1964) - University of Rome carbon 14 dates II. Radiocarbon, 6, 77-90.

Amorosi A., Colalongo M.L., Fusco F., Pasini G., Fiorini F.

(1999) - Glacio-eustatic Control of Continental-Shallow Marine Cyclicity from Late Quaternary Deposits of the Southeastern Po Plain, Northern Italy. Quaternary Research, 52 (1), 1-13.

Amorosi A., Milli S. (2001) - Late Quaternary depositional architecture of Po and Tevere river deltas (Italy) and world- wide comparison with coeval deltaic successions. Sedi- mentary Geology, 144, 357-375.

Amorosi A., Colalongo M.L., Fiorini F., Fusco F., Pasini G., Vaiani S.C., Sarti G. (2004) - Palaeogeographic and palaeo-climatic evolution of the Po Plain from 150-ky core records. Global and Planetary Change, 40, 55-78.

Amorosi A., Colalongo M.L., (2005) - The linkage between alluvial and coeval marginal marine successions: evidence from the Late Quaternary record of the Po River Plain, Italy. In: M. Blum & S. Marriott (Eds), Fluvial Sedimen- tology VII, Spec. Publ. Int. Ass. Sediment., 35, 257-275.

Antonioli F., Girotti O., Impronta S., Nisi M.F., Puglisi C. &

Verrubbi V. (1999) - Nuovi dati sulla trasgressione marina

olocenica e sulla subsudenza della Pianura Versiliese attra- verso in sondaggio di 90 metri. Atti del Convegno “Le Pianure. Conoscenza e salvaguardia”, Ferrara, 214-218.

Argnani A., Bernini M., Di Dio G.M., Papani G., Rogledi S.

(1997) - Stratigraphic record of crustal-scale tectonics in the Quaternary of the northern Apennines. Il Quaternario, 10 (2), 596-602.

Bacci A., Malatesta A., Tongiorgi E. (1939) - Di una formazio- ne glaciale rissiana riscontrata a Livorno nei sedimenti della fase costruttiva del ciclo tirreniano. Atti Soc. Sc. Nat., Proc. Verb., 48, 74-85.

Baldacci F. (1999) - Struttura e piezometria del 1° acquifero artesiano in ghiaie della Pianura Pisana. Atti Soc. Tosc. Sci.

Nat. Mem., 106 (A), 91-101.

Baldacci F., Bellini L., Raggi G. (1995) - Le risorse idriche sot- terranee della Pianura di Pisa. Atti Soc. Tosc. Sci. Nat.

Mem., 101 (A), 241-322.

Barsotti G., Federici P.R., Giannelli L., Mazzanti R., Salvatorini G. (1974) - Studio del Quaternario livornese, con particolare riferimento alla stratigrafia ed alle faune delle formazioni del Bacino di carenaggio della Torre del Fanale. Mem. Soc. Geol. It., 13, 425-495.

REFERENCES

(9)

Bellotti P., Milli S., Tortora P., Valeri P. (1995) - Physical stratigraphy and sedimentology of the Late Pleistocene- Holocene Tiber Delta depositional sequence. Sedimento- logy, 42, 617-634.

Blanc A.C. (1934) - Formazioni Pleistoceniche nel sottosuolo della Versilia. Atti soc. Tosc. Sc. Na. Proc. Verb., 43, 129- 143.

Blanc A.C. (1942) - Variazioni climatiche ed oscillazioni della linea di riva nel Mediterraneo Centrale durante l’era glacia- le. Sond. Geologie d. Meer Binnenengenwasser, 65, 50-90.

Blanc A.C., Settepassi F., Tongiorgi E. (1953) - Excursion au lac de Massaciuccoli. IV Congr. Int. Inqua, Roma-Pisa, 1-29.

Broecker W.S., Kulp J.L., Tucek C.S. (1956) - Lamont natural radiocarbon measurements III. Science, 124, 154-165.

Dall’Antonia B., Ciampalini A., Michelacci L., Zanchetta G., Bossio A., Bonadonna F.P. (2004) - New insights on the Quaternari stratigraphy of the Livorno area as deduced by borehole investigations. Boll. Soc. Paleont. It., 43 (1-2), 141-157.

Dalrymple R.W., Zaitlin B.A., Boyd R. (1992) - Estuarine facies models: conceptual basis and stratigraphic implica- tions. J. Sediment. Petrol., 62, 1130-1146.

Della Rocca R., Mazzanti R., Pranzini E. (1987) - Studio geo- morfologico della Pianura di Pisa (Toscana). Geogr. Fis.

Dinam. Quat., 10, 56-84.

Embry A.F. (1993) - Transgressive-regressive (T-R) sequence analysis of the Jurassic succession of the Sverdrup Basin, Canadian Arctic Arcipelago. Ca. J. Earth. Sci., 30, 301-320.

Embry A.F. (1995) - Sequence boundaries and sequence hierar- chies: problems and proposals. In: Sequence stratigraphy on the Northwest European Margin. In Steel R.J., Felt V.L., Johannesses E.P. and Mathieu C. (Eds), Spec. Publ.

Norwegian Petrol. Soc., 5, 1-11.

Fancelli R., Grifoni R., Mazzanti R., Menchelli S., Nencini C., Pasquinucci M., Tozzi C. (1986) - Evoluzione della Pianura di Pisa. In Mazzanti R., Grifoni Cremonesi R., Pasquinucci M., Pult Quaglia A.M. (Eds), Terre e Paduli.

Reperti, documenti, immagini per la storia di Coltano.

Bandecchi e Vivaldi, Pontedera (Pi), 23-29.

Federici P.R. (1987) - Stato attuale delle conoscenze geomor- fologiche e geologiche del Bacino di Massaciuccoli in Versilia (Toscana) III. Consorzio Idraulico Canali Navigabili Burlamacca, Malfante, Venti e Quindici, Pacini, 27-52.

Federici P.R. (1993) - The Versilian trangression of the Versilia area (Tuscany, Italy) in the light of drillings and radiome- tric data. Mem. Soc. Geol. It., 49, 217-225.

Federici P.R., Mazzanti R. (1988) - L’evoluzione della paleo- geografia e della rete idrografica del Valdarno inferiore.

Boll. Soc. Geogr. It., 11 (5), 573-615.

Federici P.R., Mazzanti R. (1995) - Note sulle pianure costiere della Toscana. Mem. Soc. Geol. It., 53, 165-270.

Ferranti L., Amorosi A., Antonioli F., Dai Prà G., Lezziero A., Mastronuzzi G., Mauz B., Monaco C., Orrù P., Pappalardo M., Radtke U., Renda P., Romano P., Sansò P. (2004) - Altitude and spatial distribution of the MIS 5.5 highstand marker in Italy: relation with active tectonic processes.

32^ndInternational Geological Congress, Florence, August 20-28 2004.

Ferrara G., Reinharz M., Tongiorgi E. (1956) - Carbon-14 dating in Pisa. I. Am. Journ. Sci. Radioc. Supp., 1, 103-110.

Ferrara G., Fornaca Rinaldi G., Tongiorgi E. (1961) - Carbon- 14 dating in Pisa II. Radiocarbon, 3, 99-104.

Galletti Fancelli M.L. (1978) - Ricerche sulla subsidenza della pianura pisana. Analisi polliniche di sedimenti quaternari della pianura costiera tra Pisa e Livorno. Boll. Soc. Geol.

It., 98, 197-245.

Ghelardoni R., Giannini E., Nardi R. (1968) - Ricostruzione paleogeografica dei bacini neogenici e quaternari della bassa valle dell’Arno sulla base dei sondaggi e rilievi sismici. Mem. Soc. Geol. It., 7, 91-106.

Gioli G. (1894) - Il sottosuolo della pianura di Pisa. Boll. Soc.

Geol. It., 13, 210-233.

Grifoni Cremonesi R., Tozzi C. (1995) - Gli insediamenti dal Paleolitico all’età del Bronzo. In: Mazzanti R. (Ed), La Pianura di Pisa ed i rilievi contermini, Provincia di Pisa, 153-182.

Malinverno A., Ryan W.B.F. (1986) - Extension in the Tyrrhenian sea and shortening in the Apennines as a result of arc migration driven by sinking of the lithosphere.

Tectonics, 5, 227-245.

Marchetti M., Tongiorgi E. (1936) - Ricerche sulla vegetazio- ne dell’etruria Marittima, VII. Una torba glaciale del Lago Massaciuccoli (Versilia). Nuovo Giornale botanico It., 43.

Mariani M., Prato R. (1988) - I bacini Neogenici costieri del margine tirrenico: approccio sismico-stratigrafico. Mem.

Soc. Geol. It., 41, 519-531.

Marroni M., Mazzanti R., Mencini C. (1990) - Geologia e mor- fologia delle colline Pisane. Quad. Mus. Stor. Nat. di Livorno, 11 (1), 1-40.

Martini I.P., Sagri M. (1993) - Tectono-sedimentary characteristic of late Miocene-Quaternary extensional basin of Northern Appennines. Earth Science Reviews, 34, 197-233.

Mazzanti R. (1983) - Il punto sul quaternario della fascia costiera e dell’Arcipelago della Toscana. Boll. Soc. Geol.

It., 102, 419-556.

Mazzanti R. (1994) - La Pianura di Pisa ed i rilievi contermini.

In: Mazzanti R. (Eds), Provincia di Pisa.

Mazzanti R. (2000) - Geomorfologia del bacino Versiliese- Pisano con particolare riferimento alla “Gronda dei Lupi”, scarpata fossile che separa le Colline Livornesi, con i loro terrazzi eustatici, dalla pianura alluvionale pisana. Atti Soc.

Tosc. Sci. Nat., Mem., A, 165-189.

Meletti C., Patacca E., Scandone P. (1995) - Il sistema com- pressione-distensione in Appennino. In. Bonari G, De Vito B., Gasparini P., Vallario A. (Eds): Cinquanta anni di atti- vità didattica del Prof. Felice Ippolito, Liguori, Napoli, 361-370.

Menchelli S. (1984). Contributo allo studio del territorio pisa- no: Coltano e l’ex Padule di Stagno. Studi classici orienta- li, 32, 255-270.

Milli S. (1997) - Depositional setting and high-frequency sequence stratigraphy of the Middle-Upper Pleistocene to Holocene deposits of the Roman Basin. Geol. Rom., 33, 99-136.

Nagi A., Pascucci V. (2002) - Alternating extensional phases in post collisional basin: the Neogene Viareggio basin (Tuscany, Italy). GIS 2002, IX riunione annuale del STRATIGRAPHIC ARCHITECTURE OF LATE QUATERNARY ... Geologica Romana 38 (2005), 1-10 9

(10)

Gruppo Informale di Sedimentologia, Pescara 21-22 Ottobre, 67-68.

Nichol S.L., Boyd R., Penland S. (1994) - Stratigraphic response of wave-dominated estuaries to different relative sea-level and sediment supply histories: Quaternary case studies from Nova Scotia, Louisiana and Eastern Australia.

In: Dalrymple, W., Boyd, R., Zaitlin, B.A. (Eds), Incised- Valley Systems: Origin and Sedimentary Sequences. Soc.

Econ. Paleontol. Mineral. Spec. Publ., 51, 265-283.

Nisi M., Antonioli F., Dai Pra G., Leoni G., Silenzi S. (2003) - Coastal deformation between the Versilia and the Garigliano plains (Italy) since the last interglacial stage.

Journal Of Quaternary Science, 18 (8), 709-721.

Pandolfi D. (1975) - La sabbia silicea della bassa Versilia ed i suoi impieghi. Ed. S.E.A., Carrara.

Pascucci V., Fontanesi G., Merlini S., Martini I.P. (2001) - Neogene Tuscany shelf-western Tuscany exetension of the early post-compressional deposits (Tyrrhenian Sea - Northern Appennines, Italy). Ofioliti, 26/2a, 187-196.

Patacca E., Sartori R., Scandone P. (1990) - Tyrrhenian basin and Apenninic arcs: kinematic relations since late Tortonian times. Mem. Soc. geol. Ital., 45, 425-451.

Posamentier H.R., Vail P.R. (1988) - Eustatic controls on clas- tic deposition II - Sequence and systems tract models. In:

WILGUS C.K., Hastings B.S., C.G St.C. Kendall, Posamentier H.V., Ross C.A., Van Wagoner (Eds), Sea level changes: An Integreted Approach, Soc. Econ.

Paleont. Miner., Spec. Publ., 42, 125-154.

Posamentier H.W, Allen G.P. (1999) - Siliciclastic Sequence Stratigraphy - Concepts and Applications. SEPM Concepts in Sedimentology and Paleontology, 7.

Romagnoli L. (1957) - Sondaggi a 200 m di profondità nel Quaternario recente presso Pisa. Studio delle facies attra- versate e considerazioni sulla sedimentazione costiera a carattere ciclico, Boll. Soc. Geol. Ital., 76, 21-35.

Sartori F. (1978) - Studi sedimentologici e mineralogici delle alluvioni recenti della pianura pisana. I sedimenti del son- daggio della Bigattiera, presso S. Piero a Grado (Pisa ). Atti Soc. Tosc. Sci. Nat., Mem., 85 (A), 61-93.

Sartori R. (1989) - Evoluzione neogenico-recente del bacino tirrenico e i suoi rapporti con la geologia delle aree circo- stanti. G. Geol., 51 (3), 1-30.

Segre A.G. (1955) - Nota sull’idrografia continentale e marina.

Note illustrative del C.G.I., scala 1:100000, Foglio 111, Livorno, Serv. Geol. It., Roma, 20-26.

Tongiorgi E. (1956) - Le variazioni climatiche della serie Fiandriana nella pianura della bassa Versilia presso il lago di Massaciuccoli. N. Gior. Bot. It., 43, 762-764.

Trevisan L., Tongiorgi E. (1953) - Le acque del sottosuolo della pianura pisana. La Provicia Pisana, 9-10.

Valli S. (1976) - Il giacimento malalcologico di Migliarino Pisano. Nota preliminare. Boll. Inf., Gruppo A.C. Blanc, Viareggio, 14, 12-15.

Valli S. (1980) - Indagini sulle zone umide della Toscana. VIII.

Il giacimento malacologico del padule di Massaciuccoli.

In: Il bacino di Massaciuccoli, 1, Pacini, Pisa.

Accettato per la stampa: Giugno 2005

Stratigraphic architecture of Late Quaternary deposits in the lower Arno Plain (Tuscany, Italy)

STRATIGRAPHIC ARCHITECTURE OF LATE QUATERNARY DEPOSITS IN THE LOWER ARNO PLAIN (TUSCANY, ITALY)

Margherita Aguzzi*, Alessandro Amorosi* & Giovanni Sarti**

Margherita Aguzzi, Alessandro Amorosi & Giovanni Sarti**