Vegetation variability in Italy at the transition St Germain II to Pleniglacial
by
M. Follieri
Dip. Biologia Vegetale, Università "La Sapienza", Roma
Coauthors: D. Magri, L. Sadori

The St Germain II forest phase is generally known in central Europe as an uninterrupted process of dynamics, followed by a variable number of weak expansions of trees. These have often been given local names, including “Ognon interstadials” at La Grande Pile and the French sites, “third interstadial” in southern Germany, ”Dürnten interstadial” at several Swiss sites. However no cross-correlation of these fluctuations has been suggested because of the lack of clear vegetational signals and unquestionable stratigraphic positions. In southern Europe various oscillations have been recognized during the St Germain II (Tenaghi Philippon, Greece) or soon after (Kopais, Greece; Abric Romaní, Spain). Two long pollen records from central Italy (Lagaccione and Lago di Vico) provide new elements for a definition of the stratigraphic position and relative importance of these vegetational fluctuations. Soon after the open vegetation period following the St Germain I forest phase, three successive expansions of arboreal pollen, locally named Etruria I, Etruria II and Etruria III, are recorded both in the percentage and in the concentration diagrams; they are separated by two periods in which trees, although continuously present, are clearly reduced and only Pinus shows high percentage values. The first two forest phases display very similar vegetation dynamics, starting with deciduous oaks and Corylus, followed by an expansion of Fagus and Carpinus betulus, and ending with an increase of Abies, while the third arboreal oscillation is clearly distinct due to the dominance of deciduous oaks, accompanied by many trees in low percentages, and for the increase of Picea. The stratigraphical position of these forest phases is clear, as they are preceded at Lagaccione by the St Germain I forest expansion and the Melisay II stadial. The chronological setting is defined at Lago di Vico by a tephra layer at the basis of the first oscillation, Ar/Ar dated 87±7 ka. A tephra from the final activity of the Vico volcano is found also at the basis of Etruria I at Lagaccione. However it is not possible to define whether the St Germain II, as it is known in central Europe, should be correlated with Etruria I alone or to Etruria I and Etruria II together, or even include also Etruria III. The recently published pollen record from Lago Grande di Monticchio, although not directly correlated with the sites from central Italy, confirms the variability of the OIS 5 to 4 transition, showing, after the open vegetation following the St Germain I forest phase, two main forest expansions followed by a minor one. Considering the uncertainty of the interpretations of the pollen records so far published for this time period and in the absence of independent evidence for correlation, assignment of any of the three Etruria expansions to any of the oscillations recorded in other European pollen records or to the events punctuating the stage 4 inception in western North Atlantic cores and Greenland ice cores, may only be hypothetical.

Date received: April 27, 2001

Copyright © 2001 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # cahi-32.