Il Quaternario Italian Journal of Quaternary Sciences 18(1), 2005 - Volume Speciale, 93-101 THE MAIN GEOMORPHOSITES IN UMBRIA Lucilia Gregori, Laura Melelli, Silvia Rapicetta & Andrea Taramelli Dipartimento di Scienze della Terra, Università degli Studi di Perugia, Piazza Università 06123 Perugia; email: [email protected] ABSTRACT: L. Gregori et al., The main Geomorphosites in Umbria. (IT ISSN 0394-3356, 2005). The Region of Umbria region is characterised by highly different geological and geomorphological environments, giving the territory a “geomorphodiversity” as well as considerable variability among its ecosystems. The identification of potential geomorphosites is inte- resting, and is aimed not only at protecting them, but also at an appropriate management and use of the territory as well. This work attempts to provide a preliminary analysis by identifying common parameters within those numerous environments that best correspond to the “geomorphosite” model, based on their historical, geomorphological and landscape characteristics. Therefore a review of the Umbria’s environments has been prepared. RIASSUNTO: L. Gregori et al., Principali Geomorfositi in Umbria. (IT ISSN 0394-3356, 2005). La regione Umbria è caratterizzata da ambienti geologico-geomofologici profondamente diversi tra loro che conferiscono al territorio una “geomorfodiversità” e, ovviamente, una profonda variabilità anche nell’ambito degli ecosistemi. L’identificazione dei potenziali geo- morfositi è interessante e finalizzata non solo alla loro tutela, ma anche alla corretta gestione e fruizione del loro territorio. Questo lavoro tenta una preventiva analisi individuando, attraverso parametri comuni, quei numerosi siti che, per caratteristiche stori- che, geomorfologiche e paesaggistiche, meglio rispondono al modello di “geomorfosito”. Si redige pertanto una rassegna dei siti umbri identificabili in tale ambito. I siti individuati sono estremamente rappresentativi ed in buona parte unici nel loro genere. Alcuni hanno un livello di valenza scientifica mondiale, come la “foresta fossile di Dunarobba”, o il sito di Pietrafitta, noto sia i suoi reperti fos- sili (gli elefanti di Pietrafitta) che per il ruolo chiave nella ricostruzione paleogeografia del territorio regionale. Altri siti, come il “colle di Perugia”, importante centro culturale ubicato al top di un paleoconoide, o Civita / Bagnoregio “la città che muore”, sono stati selezio- nati per la presenza, oltre che di forme o associazioni di forme di indubbia qualità didattica e scientifica, anche per la compresenza di alti valori storico-artistici e culturali. Key words : Geomorphology, Geomorphosites, Landscape, Environment, Umbria, Italy. Parole chiave: Geomorfologia, Geomorfositi, Paesaggio, Ambiente, Umbria, Italia. 1. INTRODUCTION Central Italy is characterized by many “geological and geomorphological peculiarities” described in scien- tific literature as landforms, with high scientific or cultu- ral value (Fig. 1). To this end, recent research has developed a new insight that defines these areas as geosites or geo- morphosites (BRANCUCCI & BURLANDO, 2000; PANIZZA, 1992; PANIZZA & PIACENTE, 2002a,b; POLI, 1999). Many research groups (Working Group of the I.A.G. “Geomorphological Sites” and the Italian Research project COFIN 2001-2003 “Geosites in the Italian land- scape” with the UNESCO Working Group) are working on the identification, management and protection of geomorphosites and are organizing workshops to discuss and develop this issue (in example the “Geomorphological Sites: research, assessment and Fig.1 - Location map: main geomorphosites in the Umbria improvement” workshop in Modena, June 2002). region: 1) Gubbio Basin; 2) Trasimeno Lake; 3) Perugia Paleo- Based on the approaches currently available, the Delta; 4) Subasio Mountain; 5) Colfiorito Polye; 6) Pietrafitta aim of this paper is to make an inventory of geo- Mine; 7) Clitunno Springs; 8) Sibillini Mountains / Pian Grande morphosites in and near the region of Umbria. Polye; 9) Orvieto “Mesa”; 10) Civita di Bagnoregio; 11) Dunarobba; 12) Marmore Falls. Some features, well known in literature (CARTON et al., 1994), are used to identify the value of the “natural Localizzazione dell’area di studio: principali geomorfositi in resources.” Others (scientific, cultural and social eco- Umbria: 1) il Bacino di Gubbio; 2) il Lago Trasimeno; 3) il Paleo-Delta di Perugia; 4) il Monte Subasio; 5) il Polye di nomic) are assessed to define the importance of the Colfiorito; 6) la Miniera di Pietrafitta; 7) le Fonti del Clitunno; 8) i sites from a world, national, regional and local perspec- Monti Sibillini / il Polye del Pian Grande; 9) la Mesa di Orvieto; tive (CARTON et al., 1994). Furthermore, there are limita- 10) Civita di Bagnoregio; 11) Dunarobba; 12) la Cascata delle tions in the current approaches in describing and analy- Marmore. 94 L. Gregori et al. sing the degree of hazard and the ex-post recovery and tion. Furthermore, Perugia is one of the most important fruition activities. Thus there is a need to improve exi- cultural and historical towns in central Italy. It is not the sting methods and to develop new approaches. For only example of a town situated on a fluvial paleodelta, each geomorphosite, some aspects, in addition to the but what makes it particular is the good state of preser- literature (BRANCUCCI et al., 1999), are described as con- vation of the landform and the large number of points of ditions of hazard/risk situations. A better understanding observation along the hill recognisable, from top to bot- of the mechanics and statistics of the geological and tom set beds (Fig. 3). geomorphological processes involved, along with Some of the points of observation of paleodelta increased attention to the cultural heritage, has facilita- outcrops are situated near important historical sights in ted the individuation of several geomorphosites already Perugia. Interesting outcrops are found at the Volumni known as important tourist resources in Umbria Hypogeum (2nd century BC), an Etruscan chamber (GREGORI & RAPICETTA, 2001). tomb, belonging to the Velimna family. Geomorphosites are divided into two groups. In Another particular paleodelta outcrop sight is at the first group, morphological characteristics are given the Etruscan well (2nd- 3rd cent. BC), a marvel of engi- together with cultural/historical and scenic values, for neering skill. The many connections between urban example medieval villages near or over landforms; in development and geological-geomorphological eviden- the second, scientific values are predominant. In this ce are the main grounds for defining the Perugia paleo- group the principal attributes are the peculiarities of the delta as a good example of a geomorphosite. geomorphologic processes or the special nature of the landforms and its conditions. 2.2 The Orvieto “mesa” The town of Orvieto is an important tourist attrac- tion in Umbria. It is situated on a mesa derived from 2. GEOMORPHOSITES AND TOWNS morpho-selection processes (Fig. 4). During the Middle Pleistocene/Holocene, erosion 2.1 The hill of Perugia: an example of a paleodelta processes separated the “mesa” from the Alfina high Perugia is an excellent example of a town built plain that was the northern part of the Vulsino over a fluvial paleodelta (Fig. 2). In the Plio-Pleistocene Apparatus. The Orvieto mesa is an erosional “relic”. the paleo-Tiber flowed into the ancient Lake Tiberino The sequence outcropping on these structures is near Perugia. The ancient town centre is built over the in the upper part the pyroclastic series (tuffs) from vol- Tiber paleodelta top set (CATTUTO & GREGORI, 1988). Sand and conglo- merate strata in a hori- zontal setting (top set) are found at the top of the hill along the main roads of the town. Going downward toward the new part of the town, clays, mud/sands and sands outcrop in the middle part of the slope (foreset beds). At the bottom of the hill, these deposits are composed instead of finer particles (mud and clays) in hori- Fig. 2 – Perugia geological section: 1) calcareous bedrock; 2) marly bedrock; 3) arenaceous/marly zontal strata. The lobes bedrock; 4) clayey deposits; 5) sandy deposits; 6) gravel deposits (in Cattuto & Gregori, 1988). of the paleodelta are Sezione geologica del Colle di Perugia: 1) substrato roccioso a composizione calcarea; 2) substrato recognisable from diffe- roccioso a composizione marnosa; 3) substrato roccioso a composizione arenaceo/marnosa; 4) depo- rent observation points. siti argillosi; 5) depositi sabbiosi; 6) depositi conglomeratici (in Cattuto & Gregori, 1988). The Perugia paleodelta is of both scientific and cul- tural interest. According to this hypothesis the hill of Perugia is considered an erosional residue of Lake Tiberino. The reco- gnising of the delta brings to light different neotectonic conditions linked to the evolution of Fig. 3 - Perugia cross section with the three delta sets (in Cattuto et al., 1995). Lake Tiberino and the Sezione longitudinale del colle di Perugia con la ripartizione dei tre sets del delta (in Cattuto et al., paleo-Tiber flow direc- 1995). The main geomorphosites in Umbria 95 canic events during the Pleistocene, and in the lower part of the slope are the Pliocene clays (Fig. 5). Fluvial erosion and mass movement phenomena produced the development of pyroclastic covering with collapse in the upper part of the slope (where the pyro- clastic sequence outcrops) and landslides in the lower part (Fig. 6). In ancient times, local populations chose