Imp.Diligenti& GEOMORPHOSITES IN THE LANDSCAPE OF MONTI DEL FURLO (NORTHERN MARCHE APENNINES) Antonio Diligenti1, Olivia Nesci1 & Daniele Savelli1 1Istituto di Geologia, Università degli Studi “Carlo Bo”, Campus Scientifico, Loc. Crocicchia, 61029 Urbino d.savelli@uniurb.it ABSTRACT: A. Diligenti et al., Geomorphosites in the landscape of Monti del Furlo (northern Marche Apennines). (IT ISSN 0394-3356, 2005). Three geomorphosites pertaining to the Monti del Furlo are taken into consideration. Such area embraces the northernmost sector of an extended anticline ridge and is almost entirely included into a recently created Natural National Reserve. It is therefore clear how important it is in a naturalistic perspective. Moreover, the cultural importance of this site is stressed by the Roman Via Flaminia archaeological remains. This area also benefits from a great geologic/palaeontologic relevance, besides being really notable from a geomorphologic standpoint. In actual fact, the mountain ridge in hand is transversally cut by the Furlo Gorge, one of the most valuable and attractive geomorphosites in the Marche Apennines. Furthermore, this important site can be associated with two other areas which, although not so remarkable as the Furlo Gorge, are worth improving as geomorphosites on account of their peculiar scientific, educational and scenic value. RIASSUNTO: A. Diligenti et al., Geomorfositi nel paesaggio dei Monti del Furlo (Appennino Marchigiano settentrionale). (IT ISSN 0394- 3356, 2005). Il rilievo anticlinale dei Monti del Furlo è conosciuto principalmente per la famosa omonima gola incisa profondamente dal fiume Candigliano attraverso i terreni giurassici-paleogenici della Successione Umbro-marchigiana. Il territorio dei Monti del Furlo possiede un patrimonio geologico (peculiarità strutturali e stratigrafiche e famose località fossilifere), biologico (particolari specie floristiche e fau- nistiche) e geomorfologico (la gola e i paesaggi circostanti) che si integrano felicemente con paesaggi spettacolari, oltre a inserirsi in un contesto di notevole significato storico-archeologico (per esempio la Via Flaminia Romana che attraversa la gola). I Monti del Furlo, anche per questi motivi, sono stati elevati al rango di Riserva Naturale Statale al cui interno sono inseriti anche molti sentieri ed itinerari consigliati per l’osservazione delle caratteristiche naturali più rilevanti. La gola del Furlo rappresenta un magnifico esempio di gola diaclinalica, forma molto caratteristica e abbastanza comune nei paesaggi appenninici marchigiani. Per questo è stata scelta nell’ambito del Progetto Ministeriale “Geositi nel paesaggio italiano” come geo- morfosito da studiare, conservare e valorizzare. Il presente lavoro vuole evidenziare il ruolo fondamentale che tale sito possiede nella comprensione dell’evoluzione del paesaggio marchigiano, in particolare per la genesi delle gole trasversali alle strutture tettoniche. Al suo interno sono localizzati e descritti elementi geomorfologici caratterizzanti e peculiari che sono componenti chiave nella interpreta- zione del paesaggio e contribuiscono inoltre alla bellezza scenica del geomorfosito. Nelle vicinanze della gola, sempre all’interno della Riserva Naturale, sono stati individuati altri due geomorfositi, la valle de “Il Buzzo” e la frana di Ca i Fabbri, che, oltre a costituire individualmente aree di rilevante interesse geomorfologico, contribuiscono contestualmen- te alla conoscenza dell’intero paesaggio dei Monti del Furlo. Keywords: Geomorphosites, Furlo Gorge, Marche Apennines. Parole Chiave: Geomorfositi, Gola del Furlo, Appennino Marchigiano. Il Quaternario Italian Journal of Quaternary Sciences 18(1), 2005 - Volume Speciale, 203-211 1. FOREWORD The anticline mountains of Pietralata-Paganuccio Mts. (respectively 888 and 976 m high, here called “Monti del Furlo”, according to a local designation) are well-known primarily for housing the famous Furlo Gorge, a striking canyon deeply cut by the Candigliano River (Metauro River basin) across the Jurassic- Paleogene calcareous and marly-calcareous formations of the autochthon Umbria-Marche Succession. The Furlo Gorge cross-cuts an anticline mountain ridge (Figs. 1, 2): with the Frasassi one (famous for its ama- zing caves above all), it is the best example of such puzzling landforms so characteristic of central Italy. Besides, it is one of the best geomorphosites (sensu Panizza, 2001, i.e. “a site of special geomorphologic interest”) in the Marche Apennines. Although impressi- ve as well as crucial to the unravelling of Plio- Quaternary evolution of this sector of the Apennines, the gorge is not the sole geomorphologic peculiarity of the Monti del Furlo area. Indeed, other valuable areas (worth improving as geomorphosites) do occur in its vicinity (cf. Fig. 2), giving the Gorge itself a surplus value. Hence, in short, the area under discussion can be considered as encompassing more than one geo- morphosite of greater or lesser geomorphologic rele- vance, each contributing to the geomorphologic eva- luation of the whole. In turn, each geomorphosite com- prises several individual, characterising landforms and/or landform associations of either scientific-educa- tional importance or scenic relevance. More to the point, the Monti del Furlo area holds a major geologic- palaeontologic (e.g. structural and stratigraphic peculia- rities and famous fossiliferous sites), naturalistic (e.g. 204 A. Diligenti et al. Fig. 1 - Geologic sketch of the northern Marche region and location of the areas discussed in the text. Schema geologico dell’area nord-marchigiana e ubicazione delle aree trattate nel testo. Fig. 2 - Shaded relief of the Monti del Furlo anticline ridge with the location of the geomorphosites described in the text. The dotted line indicates the boundary of the study area. Modello digitale della dorsale anticlinalica dei Monti del Furlo con l’ubicazione dei geomorfositi descritti nel testo. La linea puntinata indica il limite dell’area considerata nella presente nota. occurrence of floristic and faunal peculiarities), landsca- pe (e.g. the gorge itself and the surrounding scenery) and historical-archaeological (e.g. the Roman Via Flaminia remnants) relevance as well. These very essentials of both the Furlo Gorge and its environs have recently made this area become a National Natural Reserve (Riserva Naturale Statale della Gola del Furlo), thereby arousing a great and renewed interest of both national and international communities. Hence the Monti del Furlo area as a whole can be regarded as a “landscape unit” (cf. Panizza & Piacente, 2003, p. 264), where the geomorphologic constituents integrate into a wider naturalistic and historical-cultural geographic context. Therefore, in the framework of the MIUR co- financed project “The geosites of the Italian landscape: research, evaluation and enhancement” the Urbino Research Group, taking its cue from such basics and allowing for the global geosites inventory outlines (Wimbledon, 1999), has accounted the Monti del Furlo as an area of primary geomorphologic relevance, pro- posing three individual geomorphosites and adopting this sector of the Marche Apennines as a sample-area for a targeted geomorphologic mapping. 205Geomorphosites in the landscape ... 2. GEOLOGIC FRAMEWORK The Marche regional territory is characterised by a hilly coastal zone, where slightly deformed Plio- Quaternary terrains predominate, merging to the southeast into a mountain chain area mostly correspon- ding to Meso-Cenozoic folded and thrusted formations of the autochthon Umbria-Marche Apennines domain. It is characterised by two main ridges striking in a c.ca NW-SE direction, the Umbria-Marche Ridge (to the SW) and the Marche Ridge Auct. (Fig. 1), divided from each other by a broad topographic depression (cf. Bisci & Dramis, 1991 and references therein); several minor rid- ges either join the major ones flanks or stand on the inter-ridge depression (cf. Fig. 1). Both the major and the minor ridges consist of Mesozoic-Paleogene mainly carbonate and marly-calcareous units of the Umbria- Marche Succession and correspond to asymmetric, mostly thrusted, NE-vergent anticlinoria (cf. Deiana & Pialli, 1994 and references therein). The Monti del Furlo area overlaps the north- western termination of the Marche Ridge and consists of both the Paganuccio and Pietralata anticline moun- tains, divided by the Furlo Gorge (Figs. 1, 2, 3). The Paganuccio Mt.-Pietralata Mt. (i.e. Monti del Furlo) anticline, characterized by an average N120 axial trend, is a slightly asym- metric box fold lacking in any clear evidence of major emergent thrusts on the forelimb. As a rule, the anticline, plunging both to the NW (anticline periclinal closure) and to the SE (an axial depression), shows a marked local axial culmination in close proximity to the Furlo Gorge. The area at issue consists (cf. Cecca et al., 1999) of carbonates, cherty carbonates, marls and calcareous marls of the Umbria Marche Succession (Figs. 3, 4), unconformably cove- red by a discontinuous and relatively thin mantle of quaternary alluvium and slope depo- sits. The lower-Jurassic Calcare Massiccio for- mation, an over 500 m thick unit in which the Furlo Gorge is entrenched (cf. Figs. 3, 4), con- sists of massive dolomitic limestones of car- bonate platform environment and is the oldest outcropping unit. It is overlain by a c.ca 600- 700 m thick sedimentary “multilayer” exten- ding from the lower Jurassic up to the lower Miocene, consisting of calcareous/marly-cal- careous units alternating with marly/marly-cal- caraeous ones. The Jurassic units, ranging from the Calcare Massiccio up to the base of the Maiolica formation, show rather complex facies associations and significant lateral litho- stratigrafic differentiation (cf. Cecca et al., 1999 and references therein), hinting at local depositional environments matching up with a fault-block seamount slope. On the contrary, the Cretaceous-Miocene units (from the mid- upper part of the Maiolica up to the Scaglia Cinerea and Bisciaro formations), display a significant lateral continuity and rather homo- geneous lithofacies representative of an ove- rall pelagic depositional environment. Local occurrence of slumps and calciturbidites is Fig. 3 - Geomorphologic sketch of the Monti del Furlo sector enclosing the Furlo Gorge and location of the areas described in the text. Schema geomorfologico del settore dei Monti del Furlo comprendente la Gola del Furlo e ubicazioni delle aree descritte nel testo. 206 also noticeable (cf. Alvarez & Lowrie, 1984; Stow et al., 1986) as a clue to topographic irregularities in the palaeo-basin floor. Because of its geographical collocation as well as of the occurrence of both many good outcrops and significant facies differentiation in quite a small zone, the Monti del Furlo area is to be regarded as an impor- tant geologic site. Many of its outcrops allow for detai- led visualization and reconstruction of crucial stages of the Marche Apennines meso-cenozoic geologic history, from the drowning of the lower-Jurassic shallow-water carbonate platform to the establishment of persisting pelagic conditions (cf. Various Authors, 1991; Cecca et al., 1999). Moreover, several fossiliferous sites as well as regional-markers outcrops (e.g. the Bonarelli level or the K/T level) arouse both the scientific community and keen naturalists’ interest in the geologic heritage of this area. 3. THE GEOMORPHOSITES The Monti del Furlo area, corresponding to the northernmost sector of the Marche Ridge (Fig. 1) anti- cline relief, displays such a clear morphostructural imprint (Figs. 2, 5) that it can be included (togheter with Petrano Mt., see Nesci et al., 2005) among the best examples of carbonatic anticline ridges in the Central Apennines. In addition, the geomorphologic interest of the area is greatly increased by an impressive transver- se canyon, namely the Furlo Gorge. The main sectors of the ridge (i.e . Monte Pietralata and Monte Paganuccio, Fig. 2) perfectly display both the rounded geometry of the anticline and its north-west and south-east plunge-out areas. On the anticline flanks well developed homoclinal ridges and flatirons are found (Figs. 2, 6). The morphostructure has developed its peculiar arrangement by different geo- morphic processes, from weathering and mass move- ments to slope-wash and cryonivation. Whatever the occurring process, selective weathering and erosion have often been able to highlight both lithologic contra- sts of the Jurassic-Miocene “multilayer” and structural features, such as fault-zones and bended bedding sur- faces. Since weathering and erosion have been more effective under Pleistocene cold climatic conditions, several structural landforms characterising the modern landscape of the area must be regarded as almost enti- rely derived from past morphogenetic stages. Some peculiar landforms (i.e. broad natural amphitheatres and Ricter slopes), in particular, are relics of past cold climatic conditions. Others, such as those related to mass-wasting or weathering, are still more or less acti- ve, even though they can have experimented stages of more intense activity in the past. The whole area is crossed by several paths and roads, some of which can be of peculiar geomorpholo- gic interest, since they cross both the Furlo Gorge and the nearby geomorphosites. As a matter of fact, they allow people to approach many significant landforms and to have panoramic views on both the Monti del Furlo area and on the Metauro-Candigliano valley and terraces. Two of them match with as many geologic iti- neraries described by Coccioni et al. (1994) and Savelli & Tramontana (2001): since they also cross areas of major geomorphologic interest, they are suitable for educational as well as scientific purposes and worth improving as geomorphologic paths too. A. Diligenti et al. Fig. 4 - Panoramic view of the south-western side of the Monti del Furlo anticline ridge showing the outcropping Jurassic formations. Please note the entrance of the Furlo Gorge and, on the foreground, the flat top-surface of the Holocene terrace alluvium. Veduta panoramica del fianco sud-occidentale della dorsale anticlinalica dei Monti del Furlo con indicate le formazioni giurassiche affioranti. Si notino l’ingresso della Gola del Furlo e, in primo piano, la superficie pianeggiante delle alluvioni terrazzate oloceniche. 207 3.1 The Furlo Gorge Geomorphosite The principal geomorphologic peculiarity of the area is, without any doubt, the Furlo Gorge, a deep canyon cross-cutting the anticline ridge (Figs. 2-5 and 7-8). As a matter of fact, indications which are impor- tant for both scientific and educational standpoint defi- nitely arise from such an attractive and scenic gorge (cf. Bartolini & Peccerillo, 2002). Its sub-vertical walls (Fig. 8), hanging over 500 m high on the present river, have been cut into the dolomitic limestones of the Calcare Massiccio formation by the Candigliano River, the major right tributary of the Metauro River. The evolution of the drai- nage net of the Metauro- Candigliano River basin started, perhaps, as long ago as in lower Messinian time, but only during the upper Pliocene-Quaternary did the net achieve the essen- tials of its modern organization (cf. Mayer et al., 2003). It was just at that time that the anticli- ne ridge bypass was performed according to still largely uncer- tain mechanisms, which are object of a long-lasting debate and of different interpretations (e.g. Mazzanti & Trevisan, 1978, Alvarez, 1999 and references therein). The Furlo Gorge deve- Geomorphosites in the landscape ... Fig. 7 - The upstream sector of the Furlo Gorge. Veduta del tratto iniziale della gola del Furlo. Fig. 6 - Flatirons on the resistant limestones of the lower Miocene Bisciaro formation. North-eastern flank of Pietralata Mt., Monti del Furlo anticline ridge. Flatirons modellati sui calcari della formazione del Bisciaro (Miocene inf.). Fianco nord-orientale di M. Pietralata, dorsale anticlinalica dei Monti del Furlo. Fig. 5 - Panoramic view emphasizing the morphostructural arrangement of the Monti del Furlo anticline ridge. Veduta panoramica che evidenzia l’assetto morfostrutturale della dorsale anticlinalica dei Monti del Furlo. Fig. 8 - Vertical cliffs in the downstream reach of the Furlo Gorge. Le pareti verticali del tratto iniziale della Gola del Furlo. 208 lops along a dominant SW-NE joint direction (Mayer et al., 2003) just corresponding with a pronounced axial culmination of the anticline, as shown both by geologic data and the morphostructural arrangement itself (cf. Fig. 2). Moreover, a second narrow canyon (i.e. the so- called “Il Buzzo”) parallel to the main one cuts the external flank of the anticline ridge less than 1 km to the south-east of the Furlo Gorge (Figs. 2, 3, 5). The unu- sual structural position as well as the occurrence of a second minor canyon, have recently led Mayer et al. (2003) to interpret the Furlo Gorge as the result of cap- ture mechanisms, rather than superposition followed by antecedence as previous Authors asserted. In the geomorphosite area, the youngest (i.e. second half of the middle Pleistocene-Holocene) evolu- tion stages of the valley reach enclosing the gorge, are underlined by fluvial terraces occurring on both flanks of the anticline ridge just outside the gorge (cf. Fig. 3, 4, 9). In fact, several well preserved terraces and some terrace-alluvium outcrops occur close to it, reaching elevations as high as 155 m above the modern stream (Nesci et al., 1990, p. 69), and highlighting the presence of four main cycles of aggradation related to as many Pleistocene cold stages (cf. Nesci et al., 1995 and refe- rences therein). In actual fact, both the presence of ter- races and their altitudinal distribution underline a verti- cal uplift of the structure, but no evidence of terrace deformation relating to active thrusting and folding of the anticline can be alleged (cf. Di Bucci et al., 2003). Besides these major subjects of scientific, educa- tional and scenic value, both in the Furlo Gorge and in its vicinity the geomorphosite includes many other minor -yet noticeable- landforms and landform assem- blages, which contribute to enhance the geomorpholo- gic significance of the site. Some of them are worth mentioning, as follows. Small hanging valleys ending against the edge of the Furlo Gorge cliffs, although dried up for most part of the year, are able to produce impressive waterfalls when heavy storms and/or rapid snow-melt occur (Fig. 10). Narrow potholes can also be observed at the foot of the ephemeral waterfalls. Such suggestive landforms due their origin to a huge difference in down-cutting rates of the Candigliano River and of its small epheme- ral tributaries flowing on the hard dolomitic limestones at the core of the anticline ridge. Small caves (e.g. Grotta del Grano, i.e. “corn cave”, cf. Fig. 11), tens of meters large but only a few metres deep, owing their origin to moderate karst processes associated with cryo- and thermo-clastic processes, characterise the feet of the cliffs. In addition, the Calcare Massiccio walls of the Furlo Gorge bear well-developed weathe- ring landforms both on relatively weak rock-beds and along faults. In detail, a series of weathering niches developed both along strata and along joint systems (Fig. 11). In the first case, apart from a very crude bed- ding of the dolomitic limestones forming the gorge walls, the occurrence of weaker beds is locally underli- ned by a series of weathering niches arranged along curved lines which follow the bending of the anticline structure cross-cut by the gorge. In the latter case, because of poor re-cementation by carbonates, the rock has been made less resistant to weathering all A. Diligenti et al. Fig. 9 - Upper Pleistocene (uP) and late-middle Pleistocene (mP) fluvial terraces close to the downstream termination of the Furlo Gorge. Terrazzi del Pleistocene superiore (uP) e del Pleistocene medio-finale (mP) in prossimità dello sbocco della Gola del Furlo. Fig. 10 - Waterfalls during a stage of activity of hanging valleys inside the Furlo Gorge. Cascata in un periodo di attività di una delle valli sospese pre- senti all’interno della Gola del Furlo. along the fractured zones, thus improving the produc- tion of niches by cryo- and thermo-clastic processes associated with more or less pronounced carbonate solution. On the contrary, narrow rocky walls and ridges as well as sets of rock-spurs (Figs. 12, 13) align with those major faults along which resistant fault-rocks for- med because of strong calcium-carbonate cementa- tion. Outside the gorge area such fault-related landforms are lacking because of softer terrains occur- rence. They are generally replaced by slopes of fault- line scarps or by fault scarps exhumed by selective ero- sion (cf. Fig. 7.2 in Savelli & Tramontana, 2001). Anthropic modifications performed in more or less recent historical time are also noticeable, although flaw- lessly harmonized with the natural landscape. Specifically, two Roman tunnels (2nd century BC-1st cen- tury AD, cf. Luni, 1993) chiselled out of rock walls of the Furlo Gorge characterise the canyon entrance. Furthermore, a dam built up at the beginning of the 20th century has produced an attractive, narrow and deep artificial lake inside the gorge itself. 3.2 Geomorphosites in the Furlo Gorge vicinity Since the Furlo Gorge is not the one and only significant geomorphologic element of the area under discussion, two sites close to the Gorge and valuable as geomorphosites in their own right, are worth mentio- ning. One of them (i.e. Il Buzzo) is related to the Furlo Gorge geomorphosite, thus contributing to highlight its scientific as well as educational significance. The other one (Ca’ i Fabbri) is to be considered in order to better understand how important mass movements are in shaping the anticline ridge where the Gorge developed. 3.2.1 Il Buzzo The so called “Il Buzzo”, whose geomorphologic importance has just been mentioned, is a very narrow gorge running parallel to the Furlo one (Figs. 2, 3, 5). It consists in a close “V” shaped valley whose bottom is over-deepened by a gorge which in some places is less than two metres wide. The valley, whose head is cove- red by upper Pleistocene stratified slope-waste depo- sits, is excavated in well-bedded Jurassic limestones, whereas its bottom is incised in the massive limestones 209Geomorphosites in the landscape ... Fig. 12 - Fault-related rock-spur produced by weathering in the intermediate left side of the Furlo Gorge. Sperone roccioso prodotto dalla degradazione lungo una zona di faglia, versante di sinistra della Gola del Furlo. Fig. 11 - Small caves and weathering niches aligned along both bedding and fracture-systems close to the Grotta del Grano, intermediate sector of the Furlo Gorge. Nicchie di degradazione lungo sistemi di fratture e superfici di stratificazione in prossimità della Grotta del Grano, settore intermedio della Gola del Furlo. Fig. 13 - Segmented fault-related rock-wall produced by weathering on the intermediate right side of the Furlo Gorge. Please note on the foreground the artificial lake due to dam- ming of the gorge exit. Muro di faglia parzialmente smantellato dovuto a degradazione selettiva, fianco destro della Gola del Furlo. Si noti in primo piano l’invaso artificiale prodotto dalla costruzione di una diga all’uscita della gola. belonging (according to Cecca et al., 1999) to the lower-Jurassic Corniola Massiccia formation (cf. Fig. 4). “Il Buzzo” valley cuts the anticline ridge extending upstream far enough beyond the axis of the structure, so that the initial valley reach falls in the internal anticli- ne flank (cf. Fig. 2). Therefore, the valley head is fur- rowed in the south-western side of the anticline ridge, yet it does not bypass the mountain massif like the nearby Furlo Gorge does. The gorge is run by a minor stream, presently dry most of the year. Its vertical and overhanging walls display a strong passive structural control by joint systems trending in a SW-NE direction. A particular rock bridge (Fig. 14) occurs in the interme- diate valley reach, where slid rock-blocks only partly reworked by stream obstruct the valley bottom to a degree. 3.2.2 Ca i Fabbri Landslide The Monti del Furlo mountain ridge is a remarka- ble natural example of an exhumed anticline, where the geologic structure is distinctly replicated by the relief topography (cf. Figs. 2, 5). Although the ridge has been shaped by different processes, the role of mass move- ments, as in the past, is today one of the most effective (cf. Fig. 3). Indeed, the flanks of the anticline ridge have been extensively denudated by more or less shallow landsliding, able to highlight both lithologic contrasts and structural features, such as bended bed-surfaces. These processes are generally favoured by the occu- rence of weak marly/clayey-marly interbeds/units as well as by a downslope-dipping of layers prevailing on both the anticline ridge sides. Additional control by intense jointing of rock units can often intervene, emphasizing the local tendency to landsliding. The Ca i Fabbri landslide is the best example of several large landslides which are well recognisable all over the anti- cline flanks (Fig. 3); by the way, it is very close to the Furlo and Il Buzzo gorges and allows for some signifi- cant panoramic views. The landslide originates on the upland flats corresponding with the anticline crest. It is a rock-slump extending c.ca 2 km downslope all over the north-eastern anticline flank. A fresh, marked arcua- te cliff rimmed by tension cracks marks off the landslide head. In the upper part of the slid body, a multitude of characteristic rock-pillars alternating with trenches and counterslopes -although covered by a beech forest- is so evident and distinctive to capture the attention of students as well as of common people walking along the wood paths. The slid mass becomes more and more disrupted and chaotic downslope, where its thick- ness (over 100 m) is appreciable because of deep gully dissection of the landslide body. Moreover, the landforms freshness indicate a very recent mobilization of the upper sector of the landslide, whereas the occur- rence of both deep dissection and smoothing of the sli- ding-related forms hints to an inactivity at the toe. ACKNOWLEDGEMENTS This paper was funded by MIUR to O. Nesci (co- financed project “The geosites of the Italian landscape: research, evaluation and enhancement”, 2001). Special thanks to Nicole Savelli for revising the English text. REFERENCES ALVAREZ W. (1999) - Drainage on evolving fold-thrust belts: a study of transverse canyons in the Apennines - Basin Research, 11, 267-284. ALVAREZ W. & LOWRIE W. (1984) - Magnetic stratigraphy applied to synsedimentary slumps, turbidites and basin analysis: the Scaglia Limestones at Furlo, Italy - Geol Soc. Am. Bull., 95, pp. 324-336. BARTOLINI C. & PECCERILLO A. (2002) - I fattori geologici delle forme del rilievo - Pitagora, Bologna, 216 pp. BISCI C. & DRAMIS F. (1991) - La Geomorfologia delle Marche - In: A. Minetti, T. Nanni, F. Perilli, L. Polonara & M. Principi (eds.), L’Ambiente Fisico delle Marche. Geologia, Geomorfologia, Idro- geologia, Regione Marche, Giunta Regionale, Assessorato Urbanistica-Ambiente, pp. 81-113. CECCA F., CONTE G., CRESTA S., D'ANDREA M., GRAZIANO R., MOLINARI V., PANTALONI M., PICHEZZI R. M., ROSSI M., CATENACCI V., CACOPARDO M., CENSI NERI P., PANNUTI V., BORGIA M. G., ERBA, MENICHETTI M. & RAFFI I. (1999) - Risultati preliminari del rilevamen- to nel settore sud-occidentale del foglio n. 280 Fossombrone della carta geologica d'Italia a scala 210 Fig. 14 - The curious rock-bridge inside the “Il Buzzo” gorge. Il singolare ponte naturale all’interno della gola de “Il Buzzo”. A. Diligenti et al. 1:50.000 -Boll. Serv. Geol. It., 115. COCCIONI R., MORETTI E., NESCI O., SAVELLI D., TRAMONTA- NA M., VENERI F. & WEZEL F.C., with the contribu- tion of CECCA F., CRESTA S. & PASSERI L. (1994) - Da Sansepolcro a Fossombrone (km 122). Assetto stratigrafico e strutturale della Successione umbro-marchigiano-romagnola - In: L. Passeri (ed.), Appennino Umbro-Marchigiano, 15 itinerari, Guide Geologiche Regionali, vol 7, BE-MA, Milano, pp. 103-118. DEIANA G. & PIALLI G. (1994) - The structural provinces of the Umbro-Marchean Apennines - Mem. Soc. Geol. It., 48, pp. 473-484. DI BUCCI D., MAZZOLI S., NESCI O., SAVELLI D., TRAMONTA- NA M., DE DONATIS M. & BORRACCINI F. (2003) - Active deformation in the frontal part of the Northern Apennines: insights from lower Metauro River basin area (northern Marche, Italy) and adja- cent Adriatic off-shore - Journ. Geodynamics, 36, pp. 213-238. LUNI M. (1993) - La Flaminia nelle gole del Furlo e del Burano - ARTI grafiche Editoriali Srl, Urbino, 67 pp. MAYER L., MENICHETTI M., NESCI O. & SAVELLI D. (2003) - Morphotectonic approach to the drainage analysis in the North Marche region, central Italy - Quat. Intern., 101-102, pp. 157-167. MAZZANTI R. & TREVISAN L. (1978) - Evoluzione della rete idrografica nell’Appennino centro-settentrionale - Geogr. Fis. Dinam. Quat., 1, pp. 55-62. NESCI O., SAVELLI D. & MENGARELLI D. (1990) - I terrazzi vallivi del 1° ordine nei bacini dei fiumi Metauro e Foglia (Appennino marchigiano) - Geogr. Fis. Dinam. Quat., 13, pp. 63-73. NESCI O., SAVELLI D., CALDERONI G., ELMI C. & VENERI F. (1995) - Le antiche piane di fondovalle nell’Appennino nord-marchigiano - In: G. B. Castiglioni & P. R. Federici (eds.), Assetto fisico e problemi delle pianure italiane, Mem. Soc. Geogr. It., 53, pp. 293-312. NESCI O., SAVELLI D., DILIGENTI A. & MARINANGELI D. (2005) - Geomorphological sites in the northern Marche (Italy). Examples from autochthon anticline ridges and from Val Marecchia allochthon - Il Qua- ternario, this volume. P ANIZZA M. (2001) - Geomorphosites: concepts, methods and examples of geomorphological sur- vey - Chinese Sci. Bull., 46, pp. 4-6. PANIZZA M. & PIACENTE S. (2003) - Geomorfologia cultu- rale - Pitagora, Bologna, 350 pp. SAVELLI D. & TRAMONTANA M. (2001) - Itinerario 7. Il ver- sante sinistro della Gola del Furlo - In: G. Ciarapica & L. Passeri (eds.), Guide Geologiche Regionali, Appennino Umbro-Marchigiano, BE- MA (Ed.), 7 (2), pp. 59-66. STOW D.A.V., WEZEL F.C., SAVELLI D., RAINEY S.C.R. & ANGELL G. (1986) - Depositional model for calciluti- tes: Scaglia Rossa limestones, Umbro-Marchean Apennines - In: D.A.V. Stow & D.J.W. Piper (eds.), Fine-Grained Sediments: Deep-Water Processes and Facies, Blackwell Publ. Comp., Oxford, pp. 223-243. VARIOUS AUTHORS (1991) - Le emergenze geologiche e geomorfologiche delle Marche. Piano Paesistico Ambientale Regionale - Industrie Grafiche F.lli Aniballi, Ancona, 711 pp. WIMBLEDON W.A.P. (1999) - L’identificazione e la selezio- ne dei siti geologici, una priorità per la geoconser- vazione - In: G. Poli (ed.), Geositi, testimoni del tempo, Edizioni Pendragon, pp. 52-63. 211Geomorphosites in the landscape ...