8:07f=WðJul162004Þ JQI : 1378 Prod:Type:FTP ED:AnupamaDeviY þ model pp:1219ðcol:fig::NILÞ PAGN:VG SCAN: ARTICLE IN PRESS 1 3 Quaternary International ] (]]]]) ]]]–]]] 5 7 Mid-distal occurrences of the Albano Maar pyroclastic deposits and 9 their relevance for reassessing the eruptive scenarios of the most recent 11 activity at the Colli Albani Volcanic District, Central Italy 13 Biagio Giaccioa,Ã, Andrea Sposatoa, Mario Gaetab, Fabrizio Marrac, Danilo M. Palladinob, c b a d 15 Jacopo Taddeucci , Mario Barbieri , Paolo Messina , Mario F. Rolfo aIstituto di Geologia Ambientale e Geoingegneria, CNR, Via Bolognola 7, 00138 Rome, Italy 17 bDipartimento di Scienze della Terra, Universita` di Roma ‘‘La Sapienza’’, Rome, Italy cIstituto Nazionale di Geofisica e Vulcanologia, Rome, Italy 19 dDipartimento di Storia, Universita` di Roma ‘‘Tor Vergata’’, Rome, Italy 21 23 Abstract 25 The Late Pleistocene Albano Maar hosted the most recent volcanic activity of the Colli Albani Volcanic District, represented at near- vent sections by a thick pyroclastic succession of seven units clustered in two main eruptive cycles dated at around 70–68 and 41–36 ka 27 B.P., respectively. Recent stratigraphic investigations allowed us to recognise a pyroclastic succession comprising four eruptive units widely spread in the northeastern sectors of the Colli Albani volcano, up to 15 km eastward from the Albano Maar. Integrated 29 tephrostratigraphic, morpho-pedostratigraphic, archaeological, petrological and geochemical analyses enable us to recognise them as distal deposits of the first, third, fifth and seventh Albano Maar eruptions, enlarging significantly their previously supposed dispersion area. Further tephrostratigraphic studies in central Apennine area, allowed us to identify the Albano Maar products in Late Pleistocene 31 deposits of several intermountain basins, extending still further the dispersion area of distal ash fallout as far as 100–120 km from the vent. On the basis of the identification and the study of these previously unrecognised mid-distal Albano Maar deposits, a reappraisal of 33 the eruptive scenarios and related energetic parameters is proposed. r 2006 Published by Elsevier Ltd. 35 37 1. Introduction Albani volcanic area should be now reclassified as an 59 active, or at least quiescent, volcano. 39 A growing body of geo-volcanological and geochrono- Crucial as it is in a hazard evaluation prospective, here 61 logical evidence points out that the Albano multiple maar we do not report new relevant, required data to address the 41 (Fig. 1) hosted the most recent eruptive activity in the Colli problem of the time recurrence of the Albano Maar 63 Albani Volcanic District documented up to now (De Rita explosive eruptions. For the purpose of the present study, 43 et al., 1995a; Villa et al., 1999; Karner et al., 2001; we refer to the most complete available chronological 65 Funiciello et al., 2002, 2003; Marra et al., 2003; Soligo et framework recently acquired through 40Ar/39Ar measure- 45 al., 2003; Giordano et al., 2006; Freda et al., 2006a, b). ments (Freda et al., 2006a; Table 1). Indeed, our study 67 Although strong disagreement still subsists on its eruptive principally deals with the identification of the largest 47 history and in particular about the age of the last eruptive eruptive episodes and the reconstruction of related 69 episode, the dating of which flouts between c. 5 14C ka B.P. eruptive/post-eruptive scenarios, intensities and magni- 49 (Funiciello etUNCORRECTED al., 2002, 2003) and c. 36 ka B.P. (Freda et tudes, which PROOF are as much relevant for the hazard 71 al., 2006a, b), according to these recent studies the Colli assessment from possible eruptive unrest in the future. 51 Since relatively distal settings are more suitable than 73 proximal ones in order to recognise higher-intensity 53 explosive events, one of the main aim of this study is the ÃCorresponding author. Tel.: +39 06 8807 0063; fax: +39 06 880 4463. 75 E-mail address: [email protected] (B. Giaccio). improving of the knowledge on the distal occurrences of 55 77 1040-6182/$ - see front matter r 2006 Published by Elsevier Ltd. 57 doi:10.1016/j.quaint.2006.10.013 Please cite this article as: Giaccio, B., et al., Mid-distal occurrences of the Albano Maar pyroclastic deposits and their relevance for reassessing the eruptive scenarios of the most recent activity at the.... Quaternary International (2006), doi:10.1016/j.quaint.2006.10.013 JQI : 1378 ARTICLE IN PRESS 2 B. Giaccio et al. / Quaternary International ] (]]]]) ]]]–]]] 1 59 3 61 5 63 7 65 9 67 11 69 13 71 15 73 17 75 19 77 21 79 23 81 25 Fig. 1. The Albano multiple Maar and its products within the context of the Colli Albani Volcanic District. Shaded area: map of the dispersion area of the Albano pyroclastic deposits, including possibly reworked products, as reported in previous studies (data from De Rita et al., 1988, 1995a, b; Funiciello et 83 27 al., 2002; Giordano et al., 2002a; Freda et al., 2006a). White dots: investigated sections within the proximal area; black dots: occurrences of mid-distal pyroclastic deposits correlated to the Albano Maar units. Numbers refer to sections mentioned in the text. 85 29 Table 1 87 31 Schematic stratigraphic succession and age of the proximal pyroclastic products of the Albano Maar correlated with their distal equivalent units (DUs) 89 Proximal area Distal area (NE) 33 De Rita et al. (1995a) Freda et al. (2006a, b) (with updating) This study 91 40 39 35 Stratigraphy Ar/ Ar age (ka B.P.) Eruptive cycles Stratigraphy Stratigraphy V Unit Peperino Albano Present, deep soil Present, deep soil 93 35.970.6 Unit f Albano DU4 37 Incipient paleosol Shallow paleosol 36.170.3 Unit e 95 39 40.970.8 Late Lapis Albanus Incipient paleosol 97 41 Unit d Albano DU3 Paleosol Moderately deep paleosol Deep paleosol IV Unit 41.271.1 Unit c 99 43 Paleosol Deep paleosol III Unit 68.671.1 Unit b Albano DU2 101 45 Paleosol Shallow paleosol Shallow paleosol II Unit Early Unit ba 103 Paleosol Shallow paleosol 47 I Unit 69.470.6 Unit a Albano DU1 Very deep paleosol on Faete Very deep paleosol on Faete 105 49 UNCORRECTEDPhase PROOF or Ariccia Maar Phase products products 107 51 A comparison with previous stratigraphic subdivision of De Rita et al. (1995a) is also shown. 109 53 the Albano eruptive products. The recognition and of relevant eruptive parameters (i.e. erupted volumes, 111 55 correlation of the Albano eruptive products, from near eruption column heights, mass discharge rates) for major vent sections to mid-distal area, is in fact a crucial point for explosive events. 113 57 the reconstruction of the areal dispersal and determination Please cite this article as: Giaccio, B., et al., Mid-distal occurrences of the Albano Maar pyroclastic deposits and their relevance for reassessing the eruptive scenarios of the most recent activity at the.... Quaternary International (2006), doi:10.1016/j.quaint.2006.10.013 JQI : 1378 ARTICLE IN PRESS B. Giaccio et al. / Quaternary International ] (]]]]) ]]]–]]] 3 1 In this regard, previous studies focused on the recon- scoria cones within the intra-caldera area. The third Late struction of the Albano Maar stratigraphy mostly in very Hydromagmatic Phase (c. 200–36 ka; Marra et al., 2003) 59 3 proximal (near-vent) locations and revealed a complex was dominated by pyroclastic surge eruptions, with activity history related to multiple eruptive centres formation of several monogenetic or multiple maars and/ 61 5 clustered in the present lake area (e.g. De Rita et al., or tuff rings clustered southwest of the Mt. Faete edifice 1995a; Freda et al., 2006a). Until now, more distal Albano (Fig. 1). 63 7 deposits have been recognised only in limited areas north and south-west of the crater (Fig. 1)(Funiciello et al., 2002, 65 9 2003; Giordano et al., 2002b; Freda et al., 2006a). 2.2. Stratigraphy and chronology Moreover, in this area the Albano deposits are predomi- 67 11 nantly represented by channelled lithofacies, from primary The Albano Maar documented the most voluminous and and secondary volcaniclastic currents, of volcanological, recent activity (70–36 ka; Freda et al., 2006a) of Late 69 13 tephrostratigraphic and tephrochronological controversial Hydromagmatic Phase. It was previously described as a interpretation (e.g. see Funiciello et al., 2003; Marra and multiple tuff ring (De Rita et al., 1995a, b), the activity of 71 15 Karner, 2005 for two different accounts). Therefore, which consisted of five main explosive cycles. The fifth despite the advances in the reconstruction of its recent eruption cycle of Albano emplaced a pyroclastic-flow 73 17 hydromagmatic activity, the present knowledge on the deposit, interpreted as a phreatomagmatic basic ignimbrite mid-distal products of the Albano Maar is still unsatisfac- (Giordano et al., 2002a), which is the most famous deposit 75 19 tory for an adequate assessment of the related eruptive of Albano, as it was quarried since the IV Century B.C. by parameters and scenarios. the ancient Roman builders and extensively used under the 77 21 Here, we present new and re-interpreted data on name of Lapis Albanus; it is known in literature also as previously unrecognised mid-distal occurrence of the ‘‘Peperino di Marino’’ or ‘‘Peperino Albano’’. 79 23 Albano pyroclastic products, which can be now traced More recently, Freda et al. (2006a, b) and Giordano et over a much wider area than previously mapped. These al. (2006) recognised seven eruptive units separated by six, 81 25 data provide the stratigraphic basis, which enables us to more or less developed paleosols (PSs). In particular, Freda assess or reappraise the eruptive dynamics related to the et al.