Acta Palaeobot. Suppl. 2: 503–511, 1999 — Proceedings 5 th EPPC CHRONOLOGICAL FRAMING OF PLIOCENE TO EARLY PLEISTOCENE PLANT MACROFOSSIL ASSEMBLAGES FROM NORTHERN ITALY EDOARDO MARTINETTO Dipartimento di Scienze della Terra, 5, via Accademia delle Scienze, I – 10123 Torino; e-mail: martinetto@dst.unito.it ABSTRACT. The plant macrofossil documentation of northern Italy has been considerably increased by recent palaeocarpological stud- ies. In this paper twenty rich local carpofloras of the Pliocene and Early Pleistocene are analysed. Some of them are well dated by means of non-palaeobotanical methods, and are exploited as reference points in defining the regional palaeofloristic features of different time in- tervals. The remaining ones are tentatively framed in a chronological sequence thanks to ecostratigraphic (palaeoclimatic) signals. Fi- nally, the floristic data of both types of floras are used to detect the main floral changes: the Pliocene seems to be a crucial epoch for plant extinction, which occurred at least in two successive phases. KEY WORDS: Pliocene, Early Pleistocene, northern Italy, plant macrofossils, biochronology, floristic change, extinction events INTRODUCTION The Pliocene to Early Pleistocene plant macrofossil documentation of northern Italy experienced a consider- able increase in the last decade, both for the discovery of new sites and for the finding of more and more species. This is mainly due to studies on palaeocarpological as- semblages (fruits, seeds and related structures), which are preferentially exploited for the purposes of the pres- ent work. On the other hand, the information deriving from fossil leaves and wood is very scarce in the studied time span, and sometimes in need of revision; therefore it is not treated here.The main purposes of this work are to discuss the geochronologic position of several fossil floras and to the describe the contribution they can pro- vide to the Plio-Pleistocene floral history of southern Europe, e. g. to establish the extinction time of several exotic plant taxa in this area. THE PLANT MACROFOSSIL ASSEMBLAGES We will analyze the elements useful to assess the chronologic position of 21 plant macrofossil assem- blages, gathered both for marine and continental sedi- ments, either from a single layer or from a set of layers in a given succession (which, of course, seem to indicate an homogeneous palaeofloral context). These assem- blages have been selected because they allow to recon- struct local palaeofloras which contain a number species suitable for a comparative floristic analysis (20 or more, apart Leffe: 9 species). Most of them have been directly studied by the author, but additional information has been obtained from papers by Ghiotto (1995), Gregor (1985, 1986, 1990), Mai (1994) and Ravazzi (1993, 1995). These local floras can be divided in two groups: some of them can be constrained in a more or less narrow chronological range by means of non-palaeobotanical dating elements (“dated” floras: Tab. 1); others have been gathered from sediments of uncertain age (“un- dated”: Tab. 2). “DATED” LOCAL FLORAS The possibility to define the geochronologic position of these local floras is undoubtedly fundamental for a correct tuning of the floral development in the study area, therefore the stratigraphic situation and the dating methods employed for each of them are discussed in de- tail. The geographic location of the fossil sites is shown in Fig. 1, and better explained in the cited papers specifi- cally referred to each site, whose age is indicated in Fig. 2. 1) Breolungi. This local flora has been gathered from a single layer of gravely sand (layer 3) in a 100 m thick marine section. Foraminiferal assemblages have been studied (Pavia et al. 1989) both below and above the flora-bearing layer, and all of them include the benthic species Uvigerina rutila (see Rio et al. 1988), which dis- appears at the end of the Lower Pliocene, and Bolivina leonardii, which appears at the beginning of the Plio- cene. The association of the two species allows to assign these sediments to the Zanclean (Lower Pliocene), a con-