MIDDLE PLEISTOCENE VERTEBRATE-BEARING FLUVIAL

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Transcript of MIDDLE PLEISTOCENE VERTEBRATE-BEARING FLUVIAL

  • INTRODUCTION

    Ancient fluvial deposits forming aggradational riverterraces can be used as markers of uplift (Maddy, 1997;Van den Berg & Van Hoof, 2001; Westaway, 2001), inparticular if sedimentation took place close to palaeo-coasts (Burbank & Anderson, 2001). In many casesthese deposits are interbedded with shallow marine andtransitional sediments or with volcanites, in generalchronologically well constrained by biostratigraphy orradiometric age data. Moreover, fluvial deposits com-monly bear vertebrate fossil remains (Bridge, 2003),which may constitute local assemblages of biochrono-logic relevance and may be used as correlation tool withmarine isotope stages (Bridgland & Schreve, 2001).

    These three conditions, presence of river terraces,interlayering of fluvial deposits with marine ones andvolcanites, and occurrence of faunal assemblages inriver sediments are present in many Italian Neogene-Quaternary sedimentary basins and in particular in theRoman Basin, along the eastern Tyrrhenian Sea coast(Latium Region) (Fig. 1). Here, in fact, the basin fill ispartly composed of terraced fluvial deposits interbeddedwith coastal marine, volcanic and volcano-sedimentarysuccessions (Conato et al., 1980; Milli, 1997; Karner &Marra, 1998). Moreover, elevation data from top sur-

    faces of the terraces are widely used to estimate the rateof uplift along the Latium coast (Karner et al., 2001a;Giordano et al., 2003; De Rita et al., 2002). Finally, sev-eral vertebrate-bearing fossiliferous sites have been dis-covered within the fluvial-deltaic and coastal sedimentsof the Roman Basin (Milli et al., 2004; Milli & Palombo,2005).

    It is here presented a new site of palaeontologic andbiochronologic interest, the Cerveteri-Monte Li Pozzisite (CMLP site hereafter), where terraced fluvialdeposits crop out, more than 3 km inland from the pres-ent-day coastline and some 5 km NW from Cerveteri(Fig. 1). Paleontologic, sedimentologic and elevationdata of fluvial sediments are used to provide informationon chronostratigraphy and paleoenvironmental aspectsof the site and on local uplift.

    METHODS

    The CMPL palaeontologic site corresponds to an exca-vation conducted by the Soprintendenza Archeologicaper lEtruria meridionale in collaboration with theUniversit degli Studi di Roma La Sapienza and CNR-Istituto di Geologia Ambientale e Geoingegneria. The

    MIDDLE PLEISTOCENE VERTEBRATE-BEARING FLUVIAL DEPOSITS OF THECERITI MTS AREA, LATIUM COAST (CENTRAL ITALY)

    Marco Mancini1, Maria Rita Palombo2,1, Carmelo Petronio2,1, Raffaele Sardella2,1,Claudia Bedetti3, Luca Bellucci4, Emanuele Di Canzio3, Caterina Giovinazzo5,

    Mauro Petrucci6 and Flavia Trucco7

    1 CNR Istituto di Geologia Ambientale e Geoingegneria, Via Bolognola 7, 00138 Rome, Italye-mail: marco.mancini@igag.cnr.it

    2 Dipartimento di Scienze della Terra, Universit degli Studi di Roma La Sapienza, P.le A. Moro 5, 00185 Rome3 Collaboratore scientifico esterno c/o Dipartimento di Scienze della Terra, Universit di Roma La Sapienza

    4 Dottorato di Ricerca in Paleontologia, consorzio tra Universit di Modena e Reggio Emilia, di Bologna e di Roma La Sapienza5 Dottorato di Ricerca in Scienze della Terra, Universit degli Studi di Roma La Sapienza

    6 Dottorato di Ricerca in Scienze della Terra, Universit degli Studi di Torino7 Soprintendenza Archeologica per lEtruria meridionale

    Geologica Romana 39 (2006), 27-38

    ABSTRACT - It is here presented a Middle Pleistocene fossiliferous site, the Cerveteri Monte Li Pozzi(CMLP) site, located in the Ceriti Mts area, within the wider Roman Basin (Latium coast, central Italy). Theoutcropping succession is, from base to top, composed of terrigenous and carbonate fluvial deposits, travertinesand ~ 410 ka old pyroclastites. The fluvial deposits form an aggradational river terrace, belong to an ancientrisen alluvial-coastal plain and sedimented close to the palaeocoast. Two fossiliferous levels have been discov-ered inside: the lower level, where Elephas (Palaeoloxodon) antiquus and Axis sp. ? A. eurygonos were found;the upper level with E. antiquus, Stephanorhinus cf. S. hundsheimensis, Dama cf. D. clactoniana, Arvicola mos-bachensis, Testudo sp.. The faunal assemblage as a whole indicates the middle-late Galerian Mammal Age,approximately 600-500 ka, and may be correlated with the MIS 15 or MIS 13. This fossil assemblage is the firstdiscovery of Galerian fauna in the Ceriti Mts area and thus represents a new Local Fauna.

    On the basis of lithostratigraphic, biochronologic and elevation data, it is possible to estimate an approximate-ly 0.26 mm/a uplift rate in the Ceriti Mts basin.

    KEY WORDS: Middle Pleistocene, Italy, fluvial deposits, mammal fossil assemblage, uplift.

  • excavation is located on the eastern flank of Monte LiPozzi, a N-S oriented hill with planar top surface at 136m a.s.l., at the interfluve between Fosso Sassetara to theeast and Fosso Perazzetta to the west. The excavation isrectangular in plan view and presents two floors, at 118and 121 m, separated by a major step. Each floor corre-sponds to a fossiliferous level. The main front of the exca-vation is 7 m in length and is oriented N20E, with minor

    fronts perpendicular to it. This good exposure enablesphysical stratigraphic analysis and 3D facies reconstruc-tion to be made (Fig. 2), as well as collection of fossilremains and preliminary taphonomic observations.

    Facies analysis has been conducted following the stan-dard methods of field geology (Miall, 1996; 2000). Inparticular for terrigenous fluvial deposits it has been fol-lowed in part the Architectural Element Analysis ofMiall (1996), while environmental models of calcareoustufa from Pedley (1990) have been considered for faciesanalysis on travertines.

    GEOLOGICAL FRAMEWORK

    The Roman Basin and the northern-central Latiumcoastal belt

    The Roman Basin widens for more than 70 km in theNW-SE direction along the coastal region of Latium andis of tectono-sedimentary origin. It was formed after theSW-NE directed extension that affected the western mar-gin of the northern-central Apennines since LateMiocene, in concomitance with the opening of thebackarc Thyrrenian Sea Basin (Funiciello & Parotto,1978; Malinverno & Ryan, 1986; Patacca et al., 1990;Cavinato & De Celles, 1999). The Roman Basin is sub-divided into horsts and minor grabens or half-grabens,

    MANCINI et al.28 Geologica Romana 39 (2006), 27-38

    Fig. 2 - Cerveteri Monte Li Pozzi site: view of the excavation. A-E arethe facies described in the text and featured in fig.4. Bar scale is 2 min height.

    Fig. 1 - Simplified geological map of the Roman Basin, with location of selected fossiliferous sites. Legend: 1) subaeral volcanic and volcano-sed-imentary successions (Late Pliocene-Late Pleistocene); 2) marine and non-marine sedimentary successions (Late Miocene-Holocene); 3) marine, car-bonate and siliciclastic successions (Trias-Middle Miocene); 4) normal fault; 5) buried normal fault.

    12 16

    Tolfa Mts

    CeritiMts

    Rome

    Italy

    15

    1617

    38

    42

    Rome

    APENNINES

    AlbanHillsTibe

    r River

    ROMANBASINTyrrhenian Sea

    CeritiMts

    LATIUM

    LakeBracciano

    1

    Fig. 3a2

    3

    4

    5

    6 7

    8

    910 11

    12 13

    14

    1) Cerveteri-Monte Li Pozzi

    9 ) Monte Mario

    8) Vitinia

    7) San Cosimato

    6) Ponte Galeria5) Malagrotta

    4) Polledrara

    3) Castel di Guido2) Torre in Pietra

    14) Capena

    13) Redicicoli

    12) Cava Nera Molinario

    11) Saccopastore

    10) Sedia del Diavolo

    Cerveteri

    15) Fontana Ranuccio16) Isernia-La Pineta

    17) Notarchirico

    SabatiniMtsN

    10 km

    1

    2

    3

    4

    5

    Selected fossiliferous sites:

    Tolfa Mts

  • mainly bounded by NNW-SSE and NE-SW trendingnormal faults.

    The fill of the Roman Basin (Funiciello & Parotto,1978; Barberi et al., 1994; Funiciello, 1995; Marra et al.,1995), only considering sedimentary successions, iscomposed of: 1) at the base, Lower Pliocene to LowerPleistocene sequences, of shelf marine and coastal envi-ronments and up to 1 km in thickness. They cover withangular unconformity syn-orogenic, Meso-Cenozoicsuccessions and recorded phases of tectonic subsidence,interrupted by short-term phases of localised uplift. 2)Middle Pleistocene to Holocene fluvial, coastal and shal-low marine sediments, which were deposited under atectonic regime of regional uplift.

    Furthermore, in northern and central Latium a wide-spread, subaeral volcanism developed at different timeintervals: Late Pliocene, late Early Pleistocene andMiddle-Late Pleistocene (Locardi et al., 1977; Barberi etal., 1994; Cavinato et al., 1994; Funiciello, 1995; Marraet al., 1998; Karner et al., 2001b). This volcanism ismainly represented by pyroclastic products, interbeddedwith the sedimentary sequences. Related magmatism, asa whole, locally enhanced the regional trend of uplift.

    The regional uplift acted as long term control (> 1Ma) on sedimentation, volcanism and landscape evolu-tion in Latium since the late Early Pleistocene (see alsoMancini & Cavinato, 2005). Uplift rates decrease alongthe NE-SW direction, from the axis of the Apennines tothe coastal belt, i.e. from values in the range of 0.30-0.50 mm/y to 0.10-0.25 mm/y (DAgostino et al., 2001,with references). This uplift was probably due to isosta-tic rebound after the ENE directed compression of theApenninic Chain or to mantle upwelling (Barberi et al.,1994; Cavinato & De Celles, 1999; DAgostino et al.,2001).

    Sedimentation and morphological evolution of thenorthern-central coastal belt of Latium also results fromthe concomitance of glacio-eustatic and climatic con-trols with regional uplift, du