StratigrafiaRivist.r ìraliana di PrleontoloEra e Settembre 2001 NOTA BREVE-SHORT NOTE THE FOSSIL VERTEBRATE DATABASE OF THE NATURAL HISTORY MUSEUM OF FLORENCE AND HIGH-RESOLUTION MAGNETIC STRATIGRAPHY IN THE UPPER VALDARNO BASIN, AS A CLUE TO DATE OLD COLLECTIONS ELISABETTA CIOPPI I CE GTOVRNNI NAPOLEONE 2 Receioed. Febrwar lA, 2000; accepted October 1 1, 2A00 Key-words: Fossil vertebrate collections, Data base catalogue, Magnetostratigraphic geochronologl-, Mid-Late Plìocene, Upper Val- darno. Norrh.rn Apennine.. Riassunto. La sequenza del Villafranchiano in Italia venne fissa- ta per una parte abbondante sulie associazioni faunistiche prolenientì dalle collezioni del Museo di Soria Naturale di Firenze. Lc antiche collezioni del Valdarno Superiore (VS) contengono per 1o più raccolte di fossili di provenienza stratigrafica indeterminata, o con qualche pos- sibilità di ricostruire la posizione dalle condizioni geologiche dei din- torni. La recente ricostruzione map;netostratigrafica della sequenza sedimentaria del VS ha permesso di riferire i reperti più antichì a ca. 3.0 Ma nel Pliocene medjo e quelli più recenti (finora) dei siti di Matassi- no e Poggio Rosso ed altri della serie della Successione di Montevarchi, a ca.2.0-1.8 Ma ìn corrispondenza del crono Olduvai che m:rrca il Pliocene finale. Gli ultimi reperti del Villafranchiano del VS costitui- scono I'Unità Faunistica Tasso e sono assegnati al Pleistocene infe- riore, ma non sono calibrati con la magnetostratigrafia: tale cali- brazione diviene ora possibile anche per le collezioni antiche e mal datate, ed è facilitata dalle informazioni controllabili con l'automatiz.- zazione del cataloso del Museo che fornisce una serie di controlli incrociatì di rapida effettuazione. In tal modo, la fauna di Faella e la sezione di Cava Faella sono state le prime ad essere controllate, quan- do è risultata chiara l'ìmporatanza del ruolo che il catalogo può rap- presentare, specialmente per le collezioni di età vicìna all'Olduvai, poiché in questo intorno sono raggiungibili gradi di definizione estremamente elevati. La datazione numerica è in grado di permettere risoluzioni comparabili tra le vecchie e le nuove collezionì giacchè entrambi i tipi di reperti si inquadrano in uno schema unirrrio rappre- sentato dalla cronologia delle faune, dall'evoluzione sedimentaria deì bacino e dallo sviluppo delle variazioni clìmatiche regolato dalla scan- sìone dei ternpi della magnetostratìgrafia. Abstract. The well established biochronologic sequence of the Villafranchian Stage in Italy is mainly based on {aunal associations from the Upper Valdarno (UV), mostly collected since the late 18 hundreds, and housed in the Natural History Museum of Florence. The old collections were assembled from mostly unidentified strati- graphic levels, and their position possibly reconstructed from the sur- rounding geologic features. The recent magnetostratigraphic assess- ment o{ the sequence marked the earliest finds at about 3.0 Ma in the mid Pliocene. The end of the Pliocene was recorded by the Olduvai magnetochron, in the Matassino and Poggio Rosso sites, and by other sparse assemblages. The Tasso Faunal Unit, assembled in the UY is assigned to the Pleistocene, yet to be clarified by magnetostratigraph- ic data. This calibratìon of old, poorly timed faunas was greatly facili- tated by the computer-automated catalogue of the Museum. The pos- sibility of numerous feed-back controls enhanced any contradictory information in fossil collections and made them most fruitful for pale- omagnetic calibration: the Faella fauna and the Faella main outcrop are the ones that will be first reexamined. It is ìn fact now evidenced the potential role of the catalogue for accomplìshing the calibration of old findings timed around the Olduvai chron, with an accuracy depending on the available record of their inferred stratigraphic level. Numerical dates will make the old collections comparable îo the new ones, as both fitting into a comprehensive framework of faunal chronologies, sedimentary evolution of the UV basin, and development of the Plio- Pleistocene climate changes. Introduction. The first fossil collection of the Natural History Museum of Florence was catalogued in 1845 with the 356 finds from the Upper Valdarno (UV) vertebrates (Azzaroli et a|.,1992). While the collection continued to grow, its main purposes remained since focused on determination of taxa and exhibition of the best sam- ples, and minor attention was payed to their geograph- ic and stratigraphic distribution. In the mean time pale- ontologists, sedimentologists, and geologists found the UV an apt site for development of their theories in reconstructing bulk structures (Meria, 1951) and sedi- mentary evoiution of subsiding basins (Sestini, 1936). Aì1 reconstructions of that evolution (Fig. t) directly involved the biochronologic succession of the fossil remains assembled in the Museum collections, last for- malized in the Villafranchian Stage by Azzaroh (1,977) and defined in the Mammal Neogene (MN) age classifi- cation for the Western Europe. 1) Museo di Storia Naturale, Sezione di Geologia e Paleontologia, Università di 2) Dipartimento dì Scìenze della Terra, Università di Firenze, Via La Pira 4, I Firenze, Via La Pira 4, I 50121 Firenze, e-mail: cioppi@unifi.it 50121 Firenze, e-mail: napo19@unifi.it 298 E. Cioppi € C. Napoleone New initiatives involved three separate aspecrs: 1 - Development of the computerized data-base catalogue for the more than 2O,O0O individual fossil ver- tebrates in the Museum (Cioppi et aI., 1996) which per- mits automated extraction of data frorn the entire collec- tion, and provides a ready means of integrating new finds such as those retrieved from the Matassino clay pit in 1964-65 and Casa Frata in 1928 (Borselli et al., 19gO), and the latest one ar Poggio Rosso in 1995: sites precisely located and completely excavated (Mazzini et aI., 1.999). 2 - Assessment of the magneric polarity srrarlgira- phy for the UV conrinental sequences, first tested on the sediments containing the Matassino deposits (Torre et al., 1993), and then extended down to the lower sequence ar the onser of the sedimentation; now the entire UV sequence rs going to be analysed, in order to accornplish the other major goal of extending it to the whole 1.5 my rimc span rhere recorded. 3 - Continued discoverics of fossil deposits, mosr- ly made by amateurs, witl.r 'u'hom a more than 2O year collaboratior-r provided quick information and help in identifying and re covering important finds thar in rccenr years mainly came from the clay pits used by brick fac- tories and for lignite exploitation. The Upper Valdarno faunas and their significance to the Villafranchian Stage. The faunas used for setring up rhe biochronologic sequence of the Villafranchian Stage are the classical ones from the Museum collections. The sequence, recenrly updated by Azzaroli et al. (1986) and Gltozzr et Fig. 1 - Geologic sketch map of the Northern Apennines, and tectonic setting of the exten- sionai basins along the belt, since the Late Miocene (rr-rostly marine basins, in the western areas), and Pliocene and Pleistocene (continental basins, to the east). The N\f- SE trend is their typical fea- ture (Modified, after Martinì Er Sagri, 1993). The conti- nental basins were generally activated in more recenr :rges, their deposition having started since the Gauss Chron. aI. (1997), begins with the Faunal Unit (F.U.) of tiver- sa (near Asti, north-wesrern ltaly), which in the UV lacustrine sediments is represented by the local mammal fauna (l.m.f.) of Castelnuovo dei Sabbioni in the homonymous sequence (Fig. 2). The following F.U. of Montopoli (in the Lower Valdarno, downstream from Florence) is not represenr- ed in the UV but has a key position in the Museum col- lection. Also the nexr Sr. Vallier F.U. and Costa S. Gia- como F.U. are not represented. The new mammal unit showing a major faunal turnover is the Olivola F.U. (established from the Olivola Locality in the norrh- western Tuscany), which n-rarked the onset of the late Villafranchian: in the U! its affinities with the Matassi- no l.m.f. were recognized by Azzaroli (1977). The last F.U. is that of Tasso, esrablished in the UV by the old findings and roughlv reconstructed by inferences from the geologic notes on the catalogue; it was collected frorn various localities in the upperrnost levels of the Montevarchi sedimenrary sequence, but mostly in unidentified positions. The fossil deposit dis- covered in 1978 ar Casa Frata (Borselli et a1., 1980), was thought to conrain close affinities with the Tasso F.U. (De Giuli Er Masinr, 1986). The biochronologic assessmenr made by Azzaroli e t al. (1986) confirmed the UV Villafranchian succession with its main evenrs, and the menrioned site of Casa Frata was d:rted prior ro the Tasso F.U., while in the next updating by Gliozzi er al. (1997) the Olivola F.U. dif- ferentiated the affinities of the Matassino local fauna by requalifying this latter as transitional betv.een Tasso and Olivola faunas. Although Olivola was retained in the base of the Pleistocene, thc Matassino assemblagc was magnetostratigraphically calibrated as latest Pliocene (Torre et aL., 1,993). Noteworthy for the UV biochronol- ogy and the Museum collections is the significance of the Poggio Rosso large assemblage (recovered in 1995), pending a detailed taxonomic study of this fauna: its stratigraphic position between the Olivola and Tasso faunas identifies it as belonging to the general transition interval between the Pliocene and Pleistocene -an inter- val of particular interest for the UV New magnetochronologic dating of the Upper Valdarno sequence. Briefly, the geochronologic updating of the UV mammalian site ages and the environmental evolution of the main sedimentary units follow the three well-estab- lished tectono-sedimentary phases, Castelnuovo, Mon- tevarchi, and Monticello Cycles (Fig. Z). - The earliest sedimentary cycle contains also the onset of the Villafranchian fauna, whose remains were mainly assembled from the lignite-bearing seam in the Meleto Clay at an age close to 3.0 Ma (Albianelli et al., 1997).The Meleto Clay accumulated at changeable rates of continuous deposition almost until the end of the Gauss chron (Fig. 3), missing its final record until the Gauss-Matuyama (G/M) boundary ^r. 2.58 Ma by only 60 ka, as calculated by the magnetocyclic analysis there applied (Napoleone Ee Albianelli, 1998). During that time the climate underwent a progressive deterioration, from warmer and humid conditions to more temperate ones, starting at about 2.85 Ma, at which spectral analy- sis of the magnetic signature showed a transition from a Fio, 299 Stratigraphic sketch of the UV I illing. r' eraged r[ter thc sections that crop out on borh rir er .ide' (M"dif ie.. after Martini tr Sagrì, 1993) prevailing precessional signal to the onset of obliquity driven climates. No fossil remains in the UV document- ed this climate crisis. In the Lower Valdarno the Apen- nine uplift was less effective and the first fauna, the Triversa F.U., showed there a slow evolution toward the faunal assemblage of the following Montopoli F.U. (Dominici, 1994; Benvenuti et al., i995). This latter, in contrast, was so sharply defined as to represent the onset of the main turnover in the Villafranchian (Azzarol| 1977); the fossil site was caiibrated at the mid/late Piiocene boundary as it was located just some meter passed the G/M magnetochronologic boundary (Lindsay et al., 1980). - In the second sedimentary cycle the Matassino 1.m.f. represented a rather similar variety of species with the Olivola F.U. (AzzaroIi, 1,977), taken sufficient to mark the beginning of the late Viliafranchian and that of the Pleistocene. The Matassino fauna was calibrated in the paleomagnetically surweyed section (Torre et al., 1,993), and assigned to the late Olduvai (ca. 1.8 Ma). Therefore, in the UV fossil record, some 0.2-0.8 my time span is missing after the G/M boundary, to be added to the almost 0.4 Ma in the late Gauss unfossilif- erous sequence in the upper Meleto Clay. More discus- sion on that will be reported, while new sites in the UV are examined with the aim to fill the gaps in the magne- tostratigraphic reconstruction that presently interrupt the most important continental time series in the Northern Apennines. At the Olduvai time the record of fossil verte- brates became rich. Besides the Matassino fauna (and the impressive Poggio Rosso deposit, recovered on 1.995 higher up in the same clay pit), the nearby Faella area Fossil ,t,ertebrate database and magnetic stratigraplry in Valdarno 300 UPPER E. Cioppi & G. Napoleone VALDARNO SEQUENCE GPTS MAGNETOSTRATIGRAPHY Composite section r.3 4 Fig.3 -Magnetochronologic com- posite of the Pliocene sedi- ments from the UV The S. Barbara section of lacustrine clays, starting frorn the basal gravels (ca. 3.3 Ma), contains fossil remains of the Casteln- uovo dei Sabbioni l.m.f. (1) in rhe ìignire-bearing layer (ca.3.0 Ma); no finds are reported until its end (Modi- fied after Albianelli et al., lqq7r. The contpo.ite sec- tion of Ler-ane and Matassino (Modified, after Torre et al., 1993) yielded the Matassino l.m.f. (3) and the site was cal- ibrated to the initial Olduvai. In the same section the Pog- gio Rosso Locality (4) was recovered in 1995 almost on top of the normal polarìty. The next section at the Fael- la clay pìt contains the first [o'.il [ind 127. dated I nrl later than the last Castelnuo- vo find. It is marked on the 1og, but does not represent the newly fixed assemblage of the Faella l.m.f. because this covered the whole \equence. The section labeled as Tasso has the offi- clàl nJnle or rne T.rrro rail- road tunnel, not to be related to the san.ìe name earlier used for the Tasso F.U. assembled in the Museum. No fossils r.ere there found but it exhibited the split terminal Olduvai. The Casa Frata l.m.f. is not yet calibrated. The or errlì corttpo.ire . 'um- marìzing the present magne- tochronologic assessment of the Upper Valdarno sequence, is reported along u irh rhe CPTS "[ Berggren et aì. (1995). LITHOLOGY i;r -=-= --o I ot,,.tof ;] t"'.I ? li s^"af:!tu - l-atcrilLal- 2 Ura\ (r È :11_ - = =_ol Iol Iol 9I ET q d) - () o- (J a ti - z d I E - I -I|lIl I iRt unio l -. Knenct i.0.t yielded the older collection to which recent finds were added, such as the deer anrler of April 1999. In the Matassino pit, moreover, new finds were recovered stratigraphically above the Poggio Rosso site, until July- August 1.999,They were collected from layer beds which can now be correlated with the ones defined in the Fael- la clay pit, recently surveyed for sedimentology and magnetostratigraphy along new cuts in the section rAlbianelli et al. 2000). The succeding Tasso F.U. still belongs to the last deposits of the Montevarchi sedimentary cycle ìÀ/ith samples collected from the areas around the Tasso creek. But the variety of samples assembled in the Museum old 3 .22 lfannoth collectìons were also with poor paleontological investi- gations. Such fossil remains, as iisted in the catalogue, came from a number of localities whose sediments are generally made by the upper sandy members of the Montevarchi sequence. Whereas some markers suggest that the time span involved could have been rather short, the Tasso F.U. is not as yet calibrated. - The third sedimentary cycle, Monticello, accu- mulated by alluvial fans produced by the Arno river meandering when the sedimentary activity moved towards the basin fill; continuity in deposition is diffi- cult to establish. Most sediments accumulated in the basin upstream, and fossil remains were assembled from Ma o U O@ E1 fl 2I Èl 'lEl 6i oi