The fossil forest of Dunarobba (Umbria – Central Italy): palaeoforestry history through a palynological study

B/OGEOGHAPHIA » vol. XVII - 1993 (Pubblicato I131 oltobre 7 994) ll popolamenlo animale e vegetale de||'Appennino Umbro-Marchigiano The fossil forest of Dunarobba (Umbria - Central Italy): palaeoforestry history through a palynological study MONICA MEN EGHINI and ARTURO PAGANELLI Departmem‘ of Biology — Um'versz'ty of Pczdml — Via Trz'en‘e, 75 — I-35 121 Pzzdomz Key words: palynology, Central Italy, «Tiberino Lake», Villafranchian stage, Coast redwood (Seqzzoizz remperuirezzr) SUMMARY The discovery of the Fossil Forest at Dunarobba, situated at about 400 m a.s.l., lead to a project of inter- disciplinary research which is still taking place‘ The trunks from this forest (about 50) were all found in their growing position and were submerged by a considerable clay bank; they were large in size (diameter about 2 metres and up to 8 m tall) and scarcely mineralized. All the trunks studied so far belong to a single species: Taxodiaxylozz gypracezzzzz, with anatomic characte- ristics similar to the present-day Sequoia 5e27zpemz'rcm* (Biondi at £11., 1991). An ancient palynological flora has emerged which is qualitatively rich, with a predominance of AP. Pollen grains of Seqztoza, Sciadapzlyr, Tzzxozz'z‘zm2, Cycadaceae (Stazzgeria type), Nyrra, Celtis, and Encom- mia were found, along with pollens of Tsuga, Cedrus, Carya, Pterocarya, and Zelkova. The predominant taxa were Sequoia and Taxodium which, along with Aim/r, Salix, Cyperaceae, and Po- tamogetonaceae, spores of Omzzmda and Lycapadium types, and of Polypodiaceae, gave evidence of a humid forest with marsh areas, similar to the present-day coastal forests of California, where the presenbday Seqzzoirl remperuz'renr grows. Attention is drawn to the scientific significance of this important plant paleontological record, and the correspondence between the xilological and palynological examinations, is emphasized. Even though the interdisciplinary research project is still being undertaken, an attempt has been made to provide a chronological interpretation for the deposit. INTRODUCTION During an excavation of clay for brick production by the Briziarelli kiln to- wards 198O in the surroundings of the borough of Avigliano Umbro (province of Terni), at Dunarobba (within the geographical coordinates: 42°39’42”— 42°39’53” lat. N and 12°27’O8”—12°27’40” long. E Greenwich, 400 m a.s.l.), nu- merous large—size trunks were uncovered. The trunks had a diameter of about 2 meters and were up to 8 meters tall. The most striking feature of the findings was their low degree of mineralisation and especially the fact that the trunks were found in their growing position — which is really very unusual — though slightly inclined towards NE. A survey undertaken in the surrounding area sho— wed that many more trunks lay buried in clay, also in vertical position, so that 101