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Suppl. Geogr. Fis. Dinam. Quat. III, T. 2 (1997), 79-103, 19 jigg. FOURTH INTERNATIONAL CONFERENCE ON GEOMORPHOLOGY - Italy 1997 Guide for the excursion GEOMORPHOLOGY AND QUATERNARY EVOLUTION OF CENTRAL ITALY 3 D. ARINGOLI C), C. BISCI (\ A.M. BLUMETTI CO), M. BUCCOLINI (\ S. CICCACCI C), G. CILLA C), M. COLTORTI (4), D. DE RrTA e), M. D'OREFICI (6), F. DRAMIS e), P. FARABOLLINI C), L. FERRELI CI), 2 P. FREDI C), B. GENTILI C), E. ]AURAND (8), A. KOTARBA C), M. MATERAZZI C), A.M. MICHETTI C\ 2 2 G. PAMBIANCHI C), M. PECCI (6), C. PETRONIO C), J. RAFFY (8), M. RASSE C), R. SARDELLA C), G. SCALELLA C), C. SMlRAGLIA C). Eds.: B. GENTILI & F. DRAMIS INTRODUCTION For the above areas, some of the main geomorphologi cal features will be illustrated, such as large-scale gravita The excursion will start from Ancona and will continue tional movements, morphotectonic evolution of both the in the inner portion of the central-southern Marche up to periadritic belt and the intra-Apenninic depressions, hypo the end of the second day. The two fol1owing days will be gean karstic phenomena, stratified slope-waste deposits devoted to the northeastern (Campo Imperatore - Gran and their relation with terraced al1uvial deposits, Holocene Sasso) and southwestern (Fucino basin) sectors of the fluvial dynamics, glacial and periglacial morphogenesis in Abruzzi Apennines. During the last day the Sabatini Mts. the Apennines, and volcanic reliefs. area (Southern Latium) will be illustrated. During the ex cursion, some large areas, on the whole homogeneous from a physiographic point of view (fig. 1), will be crossed: GEOMORPHOLOGICAL FEATURES OF - the low-hills of the periadriatic belt; CENTRAL-SOUTHERN MARCHE - the medium-high to high hills of the central-southern (D. Aringoli, C. Bisci, M. Buccolini, G. Cilla, M. Coltorti, Marche; F. Dramis, P. Farabol1ini, B. Gentili, M. Materazzi, - the mountainous massifs and ridges of the Apennines, G. Pambianchi, M. Rasse & G. Scalel1a) hosting several tectonic depressions; - the volcanic complex of the Sabatini Mts. BEDROCK GEOLOGY (1) Dipartimento di Scienze della Terra, Università di Camerino, ltaly. The geological evolution of the region started from the (2) Dipartimento di Scienze Geologiche, III Università di Roma, ltaly. Tortonian, as a consequence of compressional tectonics as (3) Dipartimento di Scienze della Terra, Università di Chietz; ltaly. sociated to an arc-trench system migrating from the (4) Dipartimento di Scienze della Terra, Università di Siena, ltaly. Tyrrhenian to the Adriatic Sea (CENTAMORE & DEIANA, (5) Faculté de Lettre et Sciences Humaines, Cedex, Paris, France. (6) Servizio Geologico Nazionale, via Vallarsa 31, 00141, Roma, ltaly. 1986). Along the Apennines, compressional tectonics rea (7) Dipartimento di Scienze della Terra, Università di Milano, ltaly. ched its climax during the upper Messinian, resulting in (8) École Normale Superieure, BP81, 31 Avenue Lambert, 92266 Fonte the first emersions, an ended in the Lower Pliocene. More nav-aux-Roses Cedex, France. recently, it continued (even though with limited effects) in (9)" Polisb Academy 0/ Sciences, Department 0/ Geomorphology and Hy drology 0/ Mountains and Uplands, Krakow, 31-018, Poland. the eastern portion of the region, where during the Lower (lO) Servizio Sismico Nazionale, Via Curtatone 3, 00185, Roma, ltaly. Pliocene - Pleistocene a thick (up to 2300 m) marine suc (11) Cnr-Gndt cio Anpa, Via V. Brancati, 48, 00144, Roma, ltaly. cession was deposited, lying unconformably on the older (12) Dipartimento di Scienze della Terra, Università «La Sapienza», Roma, terrains (folded and eroded) and fol1owing a gendy dip ltaly. (13) Dipartimento di Geologia e Geo/isica, Università di Barz; ltaly. ping monocline. Compressional tectonics is still active Tbe excursion has been /inancially supported by the Università di Camerino. along the Adriatic coast (DRAMIS & SORRISO-VALVO, 79 ne, is a consequence of headward fluvial erosion triggered by the uplift (DRAMIS, 1992; BLUMETTI & DRAMIS, 1993). MAIN PHYSIOGRAPHIC AND GEOMORPHOLOGICAL FEATURES The periadriatic belt This area is characterized by low hills, transversally crossed by wide fluvial valleys and delimited to the East by wave-cut diffs, either active or bordered by narrow bea ches. There, Pliocene-Pleistocene marine sediments, made of by alternations of pelitic, pelitic-arenaceous, arenaceous pelitic and arenaceous layers passing to the top to sandy conglomeratic deposits (Sicilian-Crotonian), crop out. On the whole, the layers dip gently towards the sea, even thou gh locally (dose to the shoreline) folded structures (coastal structures) have been found. These deposits are often cros sed by both Apenninic and antiapenninic faults; moving inland, the dosure deposits are progressively more uplif ted, up to some hundred meters (500 m a.s.I. at Ripatran sone, some 8 km from the shoreline). Almost everywhere, slopes are covered by eluvial collu vial silty-dayey deposits which are particularly thick along the gentlest slopes and at least partially derive from wind carried material (FARABOLLINI, 1995). AB C D 1,<liM'1 Among active morphogenetic processes, the most con 5 6 spicuous are gravitational phenomena, such as flows (abundant along moderately steep slopes), falls and large FIG. 1 - Simplified litho-structural and morphological setting of CentraI slides (typical of wave-cut diffs). The huge Ancona landsli Italy. Eastern area with mainly clayey (1) and torbiditic sediments (2); de, activated on 13th December 1982 (COLTORTI & alii, Apennine chain mainly calcareous (3); western area with chiefly terrige nous and vOlcanic deposits (4). 5): periadriatic belt (A), medium-high 1984), certainly represents the most representative exam and high hills belt (B); Apenninic belt (C); volcanic complex (D); 6) pIe of the latter, set up on a deep-seated slope deformation tectonic depression; 7) normal faults; 8) overthrusts; 9) the Calderone (DRAMIS & SORRISO VALVO, 1994). glacier; lO) main antiapenninic faults. The medium-high to high hills belt In this portion of the Marche, altitudes generally range 1994), as demonstrated by the focal mechanisms of earth between 200 and 700 m a.s.I., even though they may reach quakes recorded offshore (RrGUZZI & alzi, 1989). over 1000 m (1109 m at Mt. Ascensione), with a relief of The compression was followed by an extensional phase some hundred meters (up to 500 m and more). characterized by normal faults, lowering towards the Reliefs are arranged according to alignments trending Tyrrhenian Sea and reactivating at different depths com parallel with the Apennines and are modelled into the al pressional shear planes (PIZZI, 1992; CALAMITA & alii, ternations of the Pliocene and Messinian (Laga Formation) 1994; BIGI & alii, 1996). This second phase was associated turbiditic sediments (pelitic, pelitic-arenaceous, arena with a generalized uplift. Starting from the Lower Pleisto ceous-pelitic, arenaceous and arenaceous-calcarenitic-con cene, the latter strongly increased, involving also the outer glomeratic associations). The structure is rather complex most periadriatic belt (DUFAURE & alii, 1989; DRAMIS, for the oldest terrains, affected by folds having different ra 1992). This phenomenon, connected with a vaster uplift dius, faults and overthrusts; on the other hand, Pliocene responsible for the formation of the whole Apenninic belt deposits (generally in discordance on the previous units) (DEMANGEOT, 1965; DUFAURE & alii, 1989; DRAMIS, 1992), follow a regular monodine with a dip generally ranging gave rise to the overall monodinal structure of the Plioce around 15°-20° and progressively diminishing eastwards, ne-Pleistocene sediments (reaching 1100 m a.s.I. at Mt. doser to the coast. Also the layer direction varies from Ascensione). Also the genesis of the main intra-Apenninic ENE to NE. At the surface, the structure therefore shows depression, whose older filling sediments are referred to the overall configuration of a double flexure with upward the Lower Pleistocene (BLUMETTI & DRAMIS, 1993) is con concavity, whose main and secondary axes trend parallel to nected to the extensional tectonics. The breaching of these the Apennines and EW, respectively (INVERNIZZI, 1992; depressions and their integration in the hydrographic DEIANA & PIALLI, 1994). In the area, low throw normal network, both generall~ referable to the Middle Pleistoce- faults together with two sets of joints connected with the 80 double flexure (N70-N150; N20-N100) are present; a third Adriatic, normal faults trending parallel to the Apennines set of fractures trending ca. NS and EW, generally affec and transversal faults, often transcurrent. ting the stiffer layers, has been attributed to gravitational The bedrock often crops out or is covered by thin phenomena (GENTILI & alii, 1995). layers of superficial deposits, except for some, thick but The area is deeply cut by a hydrographic network for not large, travertine outcrops. Along calcareous slopes med of almost symmetrical major valleys, crossing tran stratified slope-waste deposits are frequent, regularizing sversally to the Apennines and markedly asymmetric minor large areas (COLTORTI & DRAMIS, 1995). The presence of ones. This gives rise to a typical overall morphostructural brittle rocks (limestone and sandstone) overIying plastic settlement with cuestas (GENTILI & aIii, 1995) and wide layers (marI or c1ayey marI), tectonic discontinuities (faults, spread badlands along the steeper slopes facing between