Major Explosive Activity in the Monti Sabatini Volcanic District (Central Italy) Over the 800

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1 Major explosive activity in the Monti Sabatini Volcanic District (central Italy) over the 800-

2 390 ka interval: geochronological - geochemical overview and tephrostratigraphic

3 implications

6 Marra, F.(1), Sottili, G.(2), Gaeta, M.(3), Giaccio, B.(2), Jicha, B.(4), Masotta, M.(3), Palladino D.M.(3),

7 Deocampo, D.M.(5)

9 1) Istituto Nazionale di Geofisica e Vulcanologia - Rome - Italy

10 2) Istituto di Geologia Ambientale e Geoingegneria, CNR - Montelibretti, Rome - Italy

11 3) Dipartimento di Scienze della Terra, Sapienza-Università di Roma, Rome - Italy

12 4) Department of Geoscience University of Wisconsin - Madison - USA

13 5) Department of Geosciences, Georgia State University - Atlanta - USA

15 Corresponding author:

16 Fabrizio Marra

17 Istituto Nazionale di Geofisica e Vulcanologia

18 Via di Vigna Murata 605 - 00147 - Rome, Italy

19 e-mail: [email protected]

20 phone: +39 0651860420

21 fax: +39 0651860507

26 1

3 Abstract

5 A review of the existing chronological, stratigraphic and chemo-petrologic data of the major

6 eruptive units from the early phase of activity (800-390 ka) in the Monti Sabatini Volcanic District

7 (MSVD), belonging to the ultra-potassic magmatic region of central Italy, is presented along with

8 new radioisotopic age determinations and geochemical analyses. Through the combined use of

9 electron microprobe glass compositions, selected trace-element compositions, and single-crystal

10 40Ar/39Ar age determinations, we provide a new chrono- and chemo-stratigraphic classification of

11 the products emplaced in the 800-390 ka time interval. Besides giving insights on the petrologic

12 evolution of the Roman Comagmatic Region, the large dataset provides fundamental information

13 that is applicable to tephrostratigraphic studies in the wide region encompassing the Tyrrhenian Sea

14 margin to the Adriatic Sea basin. Distal tephras from this volcanic activity also act as important

15 geochronologic markers for the coastal sedimentary successions deposited in response to glacio-

16 eustatic fluctuations, as well as for successions in the Quaternary tectonic basins of the Central and

17 Southern Apennines. An innovative approach based on the use of discrimination diagrams of Zr/Y

18 vs Nb/Y ratios for fingerprinting altered volcanic rocks - recently developed and successfully

19 employed in archaeometric studies - is here combined to the glass compositions for classifying the

20 MSVD deposits and tested on two distal tephra layers, showing its potentiality for

21 tephrostratigraphic correlation.

23 Key-words: Monti Sabatini Volcanic District, high-K magmatism, geochronology,

24 geochemistry, tephrostratigraphy, central Italy

25 1 1. Introduction

2 The recognition of distal tephra layers deposited in sedimentary successions and their correlation

3 with proximal pyroclastic units are an important stratigraphic method. Tephrostratigraphy is in fact

4 a pinpoint tool for a number of geological, paleoenvironmental and archaeological topics, providing

5 a reliable control of the chronological framework (e.g. Lowe et al., 2011). The applicability and

6 reliability of tephrostratigraphy are, however, subordinated to the depth of knowledge of the

7 stratigraphy, chronology, petrology and major element glass and isotopic compositions of the

8 proximal pyroclastic units. Indeed, without a reliable and robust reference dataset,

9 tephrostratigraphy become an useless or even misleading chrono-stratigraphic tool.

10 The peri-Tyrrhenian high-K magmatic region, developed during the Pleistocene on the Tyrrhenian

11 Sea margin of Central Italy (Peccerillo, 2005, and references therein), represents an important

12 source of tephras due to the occurrence of intense explosive activity. However, with the exception

13 of few notable cases of study (e.g., Colli Albani Volcanic District; Giaccio et al., 2013a), the lack of

14 diagnostic data on proximal pyroclastic units limits most of these potential tephra sources for distal

15 tephrostratigraphic purposes. This is particularly true for the Monti Sabatini Volcanic District

16 (MSVD), whose eruptive history was dominated by frequent, highly explosive events up to at least

17 90 ka (e.g. Sottili et al., 2004, 2010). The mid-distal occurrences of the tephras from this volcanic

18 activity provide important geochronological constraints for the coastal sedimentary successions

19 deposited in response to glacio-eustatic fluctuations, like the Paleo-Tiber aggradational sections,

20 which serve as an independent calibration of the oxygen isotope curves (Karner and Renne, 1998;

21 Karner and Marra, 1998; Marra et al., 1998; Florindo et al., 2007; Marra et al., 2008). However,

22 when dealing with very distal sedimentary successions, the correlation of given tephras to

23 individual MSVD units is hardly tenable and often the correlation is, even if plausible, only

24 hypothetic (e.g., Karner et al., 1999; Munno et al., 2001; Galli et al., 2010; Giaccio et al., 2013b).

25 In order to strengthen the potential use of the MSVD tephras for tephrostratigraphic purposes, in the

26 present work we have combined field, geochronological and geochemical investigations to provide 1 a detailed chrono- and chemo-stratigraphic framework of the main phase of activity spanning the

2 589-389 ka interval, integrating, and in some instances revising, the previous outline. Specifically,

3 here we integrated the existing data (Conticelli et al., 1997; Sottili et al., 2004; Masotta et al., 2010,

4 Galli et al., 2010; Marra et al., 2012; Marra et al., 2011; Lancaster et al., 2010) with new detailed

5 chemo-chronostratigraphic investigations by bulk rock and electron microprobe (EMP) analyses,

6 and 40Ar/39Ar age determinations. Following a recently developed methodology (Marra et al., 2011,

7 2012; Marra and D'Ambrosio, 2012), we also propose a classification of the altered MSVD mid-

8 distal deposits by combining selected trace-element diagrams (i.e.: Zr/Y vs Nb/Y) with major

9 element analysis, thus providing diagnostic criteria for establishing tephrostratigraphic correlations.

10 In particular, we provide two case-histories by testing this method on two distal tephra layers

11 collected in the Sulmona and in the Mercure lacustrine basins, occurring in the central and southern

12 Apennines.

14 2. Stratigraphic setting

16 The MSVD is part of the Roman Comagmatic Province (Peccerillo, 2005, and references therein), a

17 high-K magmatic region that developed during Pleistocene times on the Tyrrhenian Sea margin of

18 Central Italy. The MSVD activity was characterized by K-rich magma composition, feeding

19 dominant explosive eruptions ranging from hydromagmatic to Plinian and large pyroclastic flow

20 forming events (VEI up to 4-5; Sottili et al., 2004), with erupted magma up to 10 km3 for individual

21 events, and subordinate effusive episodes.

22 The subject of the present paper is the MSVD ancient explosive activity, localized at the two source

23 areas of Morlupo and Southern Sabatini. The climactic phases of this activity period spanned the

24 interval 800-390 ka and are separated by a >100 kyr-long, relative dormancy, from the following

25 period occurring at the Bracciano and Sacrofano source areas (315 ka; Sottili et al., 2010). A late 1 hydromagmatic phase, characterized by several monogenetic centers, occurred between 150 and 90

2 ka and represents the most recent volcanic phase in the MSVD (Sottili et al., 2010).

3 The oldest products attributed to the MSVD activity are represented by several tephra layers,

4 sporadically intercalated within late Lower-early Middle Pleistocene fluvial deposits of the Paleo-

5 Tiber River, dated between 802±6 ka and 605±11 ka1 (Karner & Renne, 1998; Marra et al., 1998;

6 Karner et al., 2001; Florindo et al., 2007). The vent area of these products is uncertain. A more

7 continuous, extensive explosive phase of activity is documented by a thick succession of

8 pyroclastic-flow and fallout deposits that constitute the Vulcani Sabatini Products (Scherillo, 1947;

9 Mattias and Ventriglia, 1970: geologic map 1:100.000), cropping out above the Plio-Pleistocene

10 sedimentary substrate over a ca. 1,500 km2 area to the NW of Rome (Figure 1). The early Plinian-

11 style eruptions, emplacing fall levels and accretionary lapilli-rich ash layers (Pyroclastic fall

12 products from the Morlupo edifice, de Rita et al., 1983; 1993), as well as a spatter-flow deposit

13 (Morlupo trachyte, dated at 587±4 ka; Cioni et al., 1993), whose stratigraphic relationship with

14 respect to the other explosive products is unclear, have been attributed by de Rita et al. (1983) to the

15 activity of the Morlupo center (Figure 1). Subsequent explosive activity, responsible for the

16 emplacement of the "Sacrofano lower pyroclastic flow unit" of de Rita et al., 1993 (corresponding

17 to the "Tufo Giallo della Via Tiberina" of Mattias and Ventriglia, 1970; Alvarez, 1972; 1973; Nappi

18 et al., 1979), was instead attributed to the activity of the volcanic center of Sacrofano (Figure 1).

19 A first comprehensive geochronological framework and a revision of the stratigraphy for the

20 MSVD were provided in Karner et al. (2001). Besides verifying an age of 582±2 ka for the earliest

21 fallout deposit (First Ashfall Deposits), these authors recognized a series of large pyroclastic-flow

22 deposits erupted between 561±2 and 514±6 ka (Lower and Upper Tufo Giallo della Via Tiberina,

23 Tufo Giallo di Prima Porta, Grottarossa Pyroclastic Sequence), that were previously grouped with

24 the "Tufo Giallo della Via Tiberina" and the "Tufi stratificati varicolori di Sacrofano" (Mattias and

1 40Ar/39Ar mean weighted ages in this section are reported as they appear in the original publication. All ages are reported with 2analyticaluncertainties. 1 Ventriglia, 1970). Moreover, Karner et al. (2001) introduced the "Tufi Terrosi con Pomici Bianche"

2 pumice and scoria fall succession (488±4 ka), which was investigated in detail by Sottili et al.

3 (2004), who identified 3 major fallout horizons (Fall A, B and C) and attributed them, on the basis

4 of the isopach and isopleth maps, to the Southern Sabatini volcanic center (Figure 1). In the same

5 way, based on the dispersal area of its basal fallout (Fall D, Sottili et al., 2004), also the large

6 pyroclastic-flow forming eruption of the Tufo Rosso a Scorie Nere sabatino (Scherillo, 1940;

7 Alvarez et al., 1975), dated at 449±2 ka (Karner et al., 2001; Cioni et al., 1993), was attributed to

8 this volcanic center. The late activity of the investigated volcanic period is represented by a

9 succession of pumice and scoria fall deposits ("Tufi stratificati varicolori de La Storta", Mattias and

10 Ventriglia, 1970; Corda et al., 1978) that underlie the Tufo Giallo di Sacrofano ("Sacrofano upper

11 pyroclastic flow unit", de Rita et al., 1993) dated at 285±2 ka (Karner et al., 2001). No direct

12 geochronological constraint has been achieved so far for this pyroclastic succession, with the

13 exception of two interbedded pumice fall layers, dated at 416±12 and 410±2 (Bedded Pumice,

14 Karner et al., 2001), both identified in the present work as the Vico fallout deposit (419±3 ka,

15 Laurenzi and Villa, 1987), from Vico volcano (Figure 1). The lack of significant outcropping of

16 deposits above and below the Vico fallout layers, corroborated by the occurrence of a thick paleosol

17 documented by the present work on top of the 389±4 ka San Abbondio ash-fall succession, suggests

18 that a significant dormancy characterized the MSVD till ca. 315 ka, when a new intense explosive

19 phase of volcanic activity took place, causing the emplacement of the Tufo di Bracciano (316±6 ka)

20 and the Tufo Giallo di Sacrofano (286±6 ka) major pyroclastic-flow deposits (Sottili et al., 2010).

22 3. Methods

24 3.1 Field investigations

25 Field investigations were carried out in the whole Monti Sabatini area (Fig. 1) to obtain an updated

26 and comprehensive stratigraphic framework. A detailed description of the newly recognized 1 depositional units is provided along with the revisions of the stratigraphic units already described,

2 for which we adopt the chronology and stratigraphic nomenclature outlined in Karner et al. (2001)

3 and Sottili et al. (2004). The readers are thus addressed to these works for the detailed stratigraphy

4 and correlation therein reported.

5 The reference stratigraphic column showing the geochronologically distinct eruptive events and

6 their relationship with the mid-distal deposits intercalated within fluvio-lacustrine deposits is shown

7 in Figure 2, whereas a historical stratigraphic and geochronologic framework displaying correlation

8 with previous literature is illustrated in Table 1.

10 3.2 Geochronology

11 Eight new 40Ar/39Ar age determinations presented in this paper and three previously published

12 (Marra et al., 2011) (Table 2) were performed at the University of Wisconsin-Madison Rare Gas

13 Geochronology Laboratory. Sanidine samples and standards were fused using a 25 W CO2 laser

14 following the methods of Smith et al. (2008). All analyses are single crystal fusions except for

15 samples FAD-3 and TGCP-3, which were 3 and 4 crystal fusions, respectively. Ages are reported

16 with 2 analytical uncertainties (Table 2; Appendix 1) and are calculated relative to a Fish Canyon

17 Tuff sanidine standard age of 28.201 ± 0.046 Ma (Kuiper et al., 2008) and a value for 40K of 5.463

18 ± 0.107 x 10−10 yr−1 (Min et al., 2000). Full 40Ar/39Ar data for these experiments are reported in

19 Appendix 1.

20 We also provide previously unpublished 40Ar/39Ar ages of two samples determined at the Berkeley

21 Geochronology Center (Table 3, Appendix 2). Finally, we have reviewed and re-calculated

22 according to the age of 28.201 Ma for the Fish Canyon Tuff sanidine standard (Kuiper et al., 2008)

23 the ages of 34 samples previously dated at the Berkeley Geochronology Center following

24 procedures described in Karner and Renne (1998) (Table 3). In light of the new and re-calculated

25 data, we provide a revised interpretation for the previously published ages of four samples (R93- 1 25A, R94-30C, Karner and Renne, 1998, GSA data repository item 9845, and SAX-01, PAL-01,

2 Karner et al. 2001; Table 3; full 40Ar/39Ar data in Appendix 3).

3 In the following text, except when expressly stated, all these ages are reported according to the new

4 age of the standard, with 2 uncertainties.

6 3.3 Geochemistry

8 EMP analyses of matrix glass

9 Electron microprobe (EMP) analyses (Table 4, Appendix 4) were performed on glass from twenty

10 two pyroclastic units at the CNR-IGAG laboratory at Sapienza-University of Rome using a Cameca

11 SX50 EDS-WDS and at Istituto Nazionale di Geofisica e Vulcanologia (Rome, Italy) with a Jeol-

12 JXA8200 EDS–WDS combined electron microprobes. Both instruments are equipped with five

13 wavelength-dispersive spectrometers, using 15 kV accelerating voltage, 10 nA beam current, 2 μm

14 beam size and counting time of 10 and 20 s were used on background and peaks, respectively. The

15 following standards were adopted for the various chemical elements: jadeite (Si and Na), corundum

16 (Al), forsterite (Mg), andradite (Fe), rutile (Ti), orthoclase (K), barite (Ba), celestine (Sr), F-

17 phlogopite (F), apatite (P), spessartine (Mn) and metals (Cr). ZAF correction was used to achieve

18 true element concentrations. The relative analytical uncertainty in the measurements is <1.0%.

20 XRF analyses

21 Seven whole rock analyses (Table 5) of selected pumice and scoria clasts were performed at the

22 Dipartimento di Scienze della Terra of the Università di Perugia, using a Philips PW 1400 X-ray

23 fluorescence spectrometer (XRF). The correction for matrix effects was applied following Franzini

24 et al. (1972) and Kaye (1965). The precision is better than 15% for V, Cr, Ni, better than 10% for

25 Co, Cr, Y, Zr, Ba, and better than 5% for all the other elements. The accuracy was verified with

26 international standards and is better than ±10%. FeO, Na2O and MgO contents and LOI (loss on 1 ignition) were determined through wet chemical analyses by atomic absorption spectrophotometry,

2 using DR-N, NIM-G, GSN, GA, BCR-1, NIM-l international standards.

4 FUS-ICP-MS analyses

5 Forty-nine bulk samples of selected juvenile scoria and pumice (Appendix 5) were analyzed by

6 Lithium Metaborate/Tetraborate Fusion ICP-MS at Activation Laboratories, Ancaster, Ontario,

7 Canada. Fused sample is diluted and analyzed by Perkin Elmer Sciex ELAN 6000, 6100 or 9000

8 ICP/MS. Three blanks and five controls (three before sample group and two after) are analyzed per

9 group of samples. Wet chemical techniques were used to measure the loss on ignition (LOI) at

10 900°C. International rock standards have been used for calibration and the precision is better than

11 5% for Rb and Sr, 10% for Ni, Zr, Nb, Ba, Ce, and La, and 15% for the other elements.

13 3.4 Zr/Y vs Nb/Y discriminating diagram

15 Glass chemistry represents an attested method of magma classification, but can be applied only on

16 unaltered products. To overcome these difficulties and attempt correlation among all the

17 investigated products, we have used a trace-element based discrimination method that has been

18 recently developed and successfully applied to geo-archaeological studies (Marra et al., 2011, 2012;

19 Marra and D'Ambrosio, 2012), which relies on ratios of immobile elements that are relatively

20 insensitive to alteration process like Zr, Y and Nb (Cann, 1970; Pearce and Cann, 1973; Floyd and

21 Winchester, 1975; Pearce, 1996). The abovementioned works show that there is no substantial

22 overlapping among the Zr/Y vs Nb/Y compositional fields of the pyroclastic products of Campania

23 and those of Latium and Roccamonfina (see Figure 3a). Limited overlap occurs among the products

24 of the different Latium districts of Vulsini, Vico, Monti Sabatini, and the Colli Albani, allowing in

25 most instances to identify the source area, and in several cases to identify a specific eruption unit

26 from its Zr/Y vs Nb/Y composition (Marra and D'Ambrosio, 2012). 1 Here, we test the relationships between the distributions in the Zr/Y vs Nb/Y and in the total alkali-

2 silica (TAS) diagrams for all those products of the MSVD for which we obtained both acceptable

3 major element (either obtained by EMP on glass or by XRF and FUS-ICP-MS with LOI<6%) and

4 trace element analyses. Once these relationships are established, we will use the Zr/Y vs Nb/Y

5 diagram to classify those products for which reliable major element analyses are not available, like

6 the most altered distal tephras of the paleo-activity (Figure 3b). In comparing compositions of bulk

7 proximal and distal deposits, however, a possible variation due to the different degree of porfiricity

8 may occur and should be taken into account.

10 4. Results and discussion

12 4.1 General compositional features

14 Figure 4a shows the glass compositions in the total alkali vs silica (TAS) diagram for all samples

15 analyzed by EMP in this and previous studies (Masotta et al., 2010; Sottili et al., 2004), which are

16 representative of the whole activity period of the Morlupo and Southern Sabatini centers (Table 4).

17 Values reported in Figure 4b are the average composition of each individual sample; the complete

18 range of analytical compositions for the samples analyzed in the present work is provided in

19 Appendix 4. Glass compositions are essentially clustered within the trachytic-phonolitic field (MS-

20 A1 field in Figure 4b) with a minority of samples plotting in the tephriphonolitic-latitic field (MS-

21 A2) and in the phono-tephritic field (MS-B; i.e. Grottarossa Pyroclastic Sequence and Fall F). The

22 less differentiated compositions correspond to samples of poorly vesicular, grey scoria (black

23 symbols), in contrast to the trachy-phonolitic compositions of the highly vesicular, white pumice

24 samples (white symbols). The co-existence of whitish, pumiceous, and dark grey, scoriaceous,

25 juvenile clasts is indeed a common feature of most of the MSVD eruptive units (e.g. Sottili et al.,

26 2004; Masotta et al., 2010). 1 When the distribution in the Zr/Y vs Nb/Y diagram of the homologous samples (Figure 4c) is

2 compared to that in the TAS diagram, a strict correspondence with the compositional fields

3 described above can be established. Most of the analyzed samples plot within a rectangular area in

4 the Zr/Y vs Nb/Y diagram, corresponding to the principal trachyphonolitic compositional field in

5 the TAS diagram (MS-A in Figure 4b, c). A minority of samples displays an offset distribution

6 (MS-B field, bordered by the open dashed line in Figure 4c), corresponding to that defined by the

7 less differentiated samples in the TAS diagram.

8 Consistent with previous observations in Marra et al. (2011, 2012), the distribution of the samples

9 in the Zr/Y vs Nb/Y diagram reflects that in the TAS diagram, with the higher degree of apparent

10 evolution corresponding to the greater distance from the origin of the axes (arrow a in Figure 4b, c),

11 like it is observed for the two compositional sub-groups MS-A2 and MS-A1. Indeed, the

12 distribution coefficients of Zr and Nb for ultrapotassic magmas are similar and up to one order of

13 magnitude smaller than that of Y (e.g.: Pearce and Norry, 1979). Therefore, while the Zr/Nb is

14 slightly affected by fractional crystallization during the differentiation process, leaving the

15 inclination of the trend substantially constant, Zr/Y and Nb/Y increase in a rather homogeneous

16 measure, and the compositions plot farther and farther away from the origin of the axes. Moreover,

17 a slightly higher compatibility of Zr with respect to Nb, in particular in Al-rich clinopyroxene

18 (Foley and Jenner, 2004), explains another apparent differentiation trend represented by the

19 clockwise rotation of the compositional fields in the Zr/Y vs Nb/Y diagram (arrow a'), which also

20 corresponds to increasing differentiation.

22 4.2 Stratigraphy and geochronology

24 The new 40Ar/39Ar data and the petro-stratigraphic investigations integrate the previous literature

25 data and allow us to recognize sixteen stratigraphically and geochronologically distinct eruptive

26 events (informally referred to as "eruptive units") occurred in the MSVD in the study period. In 1 some cases, closely spaced eruptive events, also sharing analogous deposit features and source area,

2 have been grouped in eruption cycles (Figure 2; table 1), as described below. Instead, the fallout

3 deposits spanning 427±5 - 412±5 ka and previously attributed to the MSVD (Bedded Pumice,

4 Karner et al., 2001, are correlated to the activity of the nearby Vico district (Figure 2, Table 1).

6 4.2.1 Paleo-activity (808±6 - 614±3 ka)

8 The evidence of this volcanic phase is represented by ten dated tephra layers out of a dozen

9 occasionally exposed in outcrops or recovered from boreholes within fluvio-lacustrine deposits of

10 the Paleo-Tiber River correlated to marine isotopic stages 19, 17 and 15 (Marra et al., 2008, and

11 references therein). Based on radioisotopic age, trace element signature and stratigraphic

12 relationships, we have identified seven distinct eruptive units, and we have grouped the earliest four

13 into a single eruptive cycle (Paleotiber succession; Figure 2 and 3b). Ages for these eruptions are

14 assessed by combining ages of the samples attributed to the same units (Table 6). In order to make

15 correlations among these volcanic layers we had to rely on their trace-element signature, following

16 criteria described in item #1 of the supplementary material, because they are not suitable for EMP

17 glass analysis due to their high degree of alteration. Figure 3b shows the Zr/Y vs Nb/Y

18 compositions of the products of the Paleo-activity. Most samples plot within or at the margin of the

19 principal MSVD field defined by all the bulk samples of the successive phases of activity (MS-A' in

20 Figure 3a; Marra et al., 2011; 2012; Marra and D'Ambrosio, 2012). Moreover, all the samples,

21 including those of the outlier SC-Unit, are aligned parallel to the trend of this compositional field,

22 implying a roughly constant Zr/Nb ratio (which rules the inclination of the sub-rectilinear

23 compositional fields), and accounting for a common origin from the MSVD.

24 A detailed petrographic description of the tephra layers that constitute the seven eruptive units of

25 the MSVD Paleo-activity and the means of their correlation is provided as online supplementary

26 material (Suppl. Mat. #1). 1

2 4.2.2 Morlupo activity (589±4 - 514±3 ka)

4 Based on geochronologic and stratigraphic data, we infer that the Morlupo center activity (de Rita

5 et al., 1993) developed during three main stages: early (~0.59 Ma), middle (~0.55 Ma) and late

6 (~0.51 Ma) activity phases.

8 4.2.2.1 Early phase: The Tufo Giallo di Castelnuovo di Porto eruptive cycle (589±4 ka)

9 The stratigraphic relationships of the products of this eruptive cycle, along with the position of the

10 samples providing the chemo- and chrono-stratigraphic data presented in this paper are shown in

11 Figure 5a.

13 Morlupo trachyte

14 Locally, a haüyne-bearing phono-trachytic scoria deposit (Morlupo trachyte, Cioni et al., 1993)

15 crops out in the eastern sector of the MSVD, reaching a maximum thickness of 12 m near the town

16 of Morlupo, where it lies on a thermometamorphosed Pliocene clay sedimentary succession. Based

17 on this feature and on the 40Ar/39Ar age of 587±3 ka (Barberi et al., 1994), it has been previously

18 interpreted to be the first eruptive product in the whole MSVD activity. The deposit shows the

19 typical features of a near vent spatter-flow deposit, characterized by the presence of centimeter-

20 sized, poorly vesicular scoria clasts within a dark grey ash matrix. The bulk XRF analysis of one

21 sample (MOR 01, Figure 5 and 6, Appendix 5) confirms the trachytic composition of one sample

22 analyzed in Conticelli et al. (1997).

23 In contrast, a 5 cm thick whitish pumice layer occurring at the base of the deposit (inset a in Figure

24 5) yielded the most alkaline phonolitic composition among all the MSVD products (MG-8, Figure 5

25 and 6, Table 4). Major element composition and mineral assemblage of pumice, with sanidine and 1 idiosyncratic accessory amphibole, coupled to the indistinguishable radiometric age, strongly

2 suggests correlation of this layer to the Tufo Giallo di Castelnuovo di Porto.

4 Tufo Giallo di Castelnuovo di Porto (TGCP)

5 The Tufo Giallo di Castelnuovo di Porto (TGCP) is the largest pyroclastic-flow forming eruption of

6 the Morlupo early phase of activity. It broadly matches the hydromagmatic ashy-pomiceous layers

7 previously grouped into the 'Pyroclastic fall products from Morlupo edifice' unit, cropping out in

8 the Morlupo area (de Rita et al., 1993). It is known in the litterature as 'Tufo di Riano' (Mattias and

9 Ventriglia, 1970) or 'Tufo di Castelnuovo' p.p., which Mattias and Ventriglia (1970) describe to

10 overlie the Morlupo trachyte (see below) and, in other localities, the Tufo Giallo della Via Tiberina.

11 Pumice samples collected in the pyroclastic-flow deposit at Capena (Figure 1, 5) yielded a weighted

12 mean age of 589±4 ka (Table 2). The depositional features from two localities (Castelnuovo di

13 Porto and Morlupo; Figure 1, 5), including a ~1 m thick pumice fallout layer (here defined FAD-1)

14 intercalated in the upper portion of the pyroclastic-flow deposit with no evidence of temporal break,

15 are resumed in Figure 5a. Highly vesicular grey and white pumice in the TGCP pyroclastic-flow

16 deposit is characterized by a mineral assemblage dominated by sanidine and including amphibole,

17 which is quite uncommon in the MSVD products we have analyzed. Due to the pervasive

18 crystallization of leucite (lct>30wt%), matrix glass in pumice, as well as in FAD 1, plots in the

19 latite field (Figure 6a); however, a phonolitic composition for the original magma, similar to that of

20 the MG8 sample, is inferable (Masotta et al., 2010).

21 Geochronologic and stratigraphic data (Figure 7, Table 3) allow us to correlate with the TGCP

22 eruption several mid-distal pumice fall occurrences, matching in part the First Ashfall Deposits

23 (FAD) of Karner et al. (2001), including Cave (591±3 ka; Marra et al., 2009), the INGV borehole

24 (ING-02, 586±3 ka; Karner et al., 2001), and Fosso di Malafede (FoMF-C1, 595±6 ka; Marra et al.,

25 2009) (Figure 1 and 7). The extensive occurrence of a pumice horizon at the base of the volcanic

26 succession in Rome and as far as the eastern sector of the Colli Albani district (Marra et al., 2009), 1 testifies the Plinian character of the eruption responsible for its emplacement. The occurrence of an

2 accretionary lapilli-rich ash deposit, that may be regarded as the distal equivalent of the TGCP

3 pyroclastic-flow deposit, above a 5 cm-thick white pumice fall layer at both the mid- distal sections

4 of GRA/A1 and Trigoria (Karner et al., 2001; Figure 1 and 7), suggests that these pumice fall

5 occurrences may represent the early products of the TGCP eruption (FAD-0, Figure 7). However,

6 their relationship with the main TGCP pyroclastic-flow deposit and with FAD-1 is uncertain.

7 Overall, the strict age concordance of the TGCP pyroclastic-flow deposit with the the distal pumice

8 fall deposits and the Morlupo trachyte, combined to the near-vent facies of the latter, support the

9 identification of the Morlupo center as the vent area of this phase of activity.

11 Trace-element compositional features of the TGCP eruptive cycle

12 The pyroclastic-flow deposit and one FAD 1 pumice sample define, along with one sample of the

13 Morlupo trachyte (BR53, Conticelli et al., 1997), a very clustered and sub-rectilinear Zr/Y vs. Nb/Y

14 compositional field (Figure 6b). In contrast, the pumice at the base of the Morlupo spatter-flow

15 deposit displays very high Zr/Y and Nb/Y (sample MG-8, Figure 6b), a feature which characterizes

16 all the pumices erupted in the early stages of each major eruptive cycle (e.g., samples of FAD-2,

17 FAD-3A and PT2b-S2), and which is suggestive of a high degree of differentiation (Marra et al.,

18 2011).

19 The three dated distal fallout samples, for which reliable major element analyses are not available,

20 define a distinct, narrowly sub-rectilinear Zr/Y vs. Nb/Y field; a bulk sample of the pisolitic ash

21 associated to the distal fallout deposits also yield similar Zr/Y vs. Nb/Y composition (TRIG, Figure

22 7 and 6b). The out-of-trend plotting of sample MOR 01 may reflect an intermediate composition

23 between that of the main TGCP pyroclastic flow and that of the early fallout deposits (FAD 0).

25 4.2.2.2 Later Fallout Deposits: FAD-2 Eruption unit (558±14 ka)

26 1 Figure 5a shows the correlations among the fallout deposits emplaced in the time span 589-546 ka,

2 partially revising those proposed in Karner et al. (2001). In particular, we recognized two different,

3 geochronologically distinct, fallout deposits emplaced above FAD-1, here named FAD-2 (558±14

4 ka) and FAD-3 (546±5 ka). The different mean weighted age, although overlapping at two sigma

5 errors, coupled to the different Zr/Y vs Nb/Y composition of the fallout deposit sampled at Ponte

6 Galeria (Fall PG,) with respect to that sampled at Morlupo and Capena (FAD 3, FAD 3CM, FAD 3-

7 CP) (Figure 6a, b) suggest indeed the occurrence of two distinct eruptive units. Moreover, the age

8 of 546±5 ka yielded by FAD 3A at Capena, where it underlies the LTGVT (Figure 5), demonstrated

9 the stratigraphic inconsistency for the age of 565±3 ka previously attributed to the LTGVT by

10 Karner et al. (2001), and showed that emplacement of the FADs spanned a wider temporal range,

11 with respect to the previously assumed age of 586±3 ka.

12 In an attempt to investigate the causes of the stratigraphic inconsistency of the previously published

13 ages, we have re-evaluated the original data for sample R93-25A of LTGVT (Karner and Renne,

14 1998; GSA Data Repository item 9845) and have noted that it contains two populations of crystals

15 that, due to the large associated errors, were not distinguished with a 2 cutoff principle of

16 exclusion (Karner et al., 1998) (see Appendix 3). Two youngest crystals yield ages of 548±24 and

17 549±24 ka, respectively, whereas the other four have errors spanning 4 to 12 ky, and yield a well-

18 constrained weighted mean age of 565±3 ka. Based on the stratigraphic evidence at the Capena

19 section of an age ≤546±5 ka for the LTGVT, we interpret the older population in sample R92-25A

20 as a xenocrystic contamination, whereas we assume the weighted mean age of the two youngest

21 crystals, here assessed at 549±16 ka, as that attributable to the LTGVT (R93-25A-1, Table 3). This

22 age is undistinguishable from that of 546±5 ka obtained for the underlying FAD-3A, thus

23 eliminating the stratigraphic inconsistency, and it is also consistent with that of 546±3 ka provided

24 for the overlying Upper Tufo Giallo della Via Tiberina in Karner and Renne (1998) (sample R93-

25 02, Figure 5, Table 3). 1 Moreover, the older age yielded by FAD 2 at Ponte Galeria (558±14 ka) is very similar to that

2 yielded by the reworked crystals within the LTGVT (sample R93-25A-2: 565±3 ka, Table 3),

3 suggesting that these crystals may have derived from the magma of the previous eruptive cycle,

4 supporting the inference of two different eruptions emplacing FAD-2 and FAD-3. In particular, we

5 attribute to the earlier event, FAD-2, also the white pumice layer described by Karner et al. (2001)

6 at the base of the km 13 of Via Tiberina section (sample FAD 13, Figure 5), which displays

7 identical TAS composition and similar Zr/Y vs Nb/Y signature to that of Fall PG (Figure 6a and

8 6b). Also, we suggest that the age value of 565±3 ka obtained on the xenocrystals within the

9 LTGVT may constrain better the FAD-2 age with respect to the indistinguishable, but poorly

10 constrained value of 558±14 ka, yielded by the pumice fall deposits sampled at Ponte Galeria. In

11 contrast, according to the very different Zr/Y vs Zr/Y composition (Figure 6b) and the younger

12 weighted mean age of 546±5 ka, we interpret FAD-3A as a distinct, later eruption unit opening the

13 following TGVT eruption cycle.

15 4.2.2.3 Middle phase: The Tufo Giallo della Via Tiberina eruptive cycle (TGVT; 546±5 ka)

17 Based on intervening minor stratigraphic discontinuities and indistinguishable radiometric ages, we

18 consider FAD-3, LTGVT and UTGVT as different eruption units of the same eruptive cycle that we

19 name Tufo Giallo della Via Tiberina Eruptive Cycle (Figure 2, Table 1), and to which we assign the

20 well constrained age of 546±5 ka obtained in this work on the earliest erupted product (FAD-3A,

21 Table 2).

23 FAD-3 eruption unit

24 This unit includes a fallout deposit (FAD-3A) of well-sorted, cm-sized white pumice lapilli, with

25 mm-sized accidental lithics of the Pliocene clay and the meso-Cenozoic carbonate substrates, which

26 opens the major eruptive cycle leading to the emplacement of the Upper Tufo Giallo della Via 1 Tiberina (UTGVT) pyroclastic-flow deposit. The latter is one of the most voluminous eruptions in

2 the whole MSVD activity, with a minimum erupted volume of 10 km3 inferred from isopach maps

3 of the residual outcropping portions (e.g. de Rita et al., 1993). The climactic phase is preceded by at

4 least two eruptive episodes, separated by appreciable quiescence, as evidenced by two intervening,

5 incipient paleosols between the early white pumice fall (FAD-3A), a second fallout deposit made up

6 of grey, poorly vesicular scoria (FAD-3B), and the LTGVT (Figure 5).

7 The occurrence of FAD-3A only at the proximal Capena type-section and at several outcrops within

8 the town of Morlupo indicates its provenance from this vent area. The indistinguishable eruption

9 age, coupled to the pumice and lithic isopleth maps for the UTGVT pyroclastic-flow deposit

10 (Figure 8a), provide evidence of a common vent area corresponding to the Morlupo center for the

11 whole TGVT Eruption Cycle.

14 Lower Tufo Giallo della Via Tiberina eruption unit (LTGVT)

15 A 5-7-cm thick, laminated ashy surge layer (a in Figure 5b), followed by a 2-3 cm thick scoria

16 lapilli fall layer (b in Figure 5b), represent the initial stages of the LTGVT eruption in the

17 investigated, proximal sections. A faintly laminated, ash-flow deposit (c in Figure 5b), with

18 abundant, cm-sized white pumice and accretionary lapilli, is present on top with a variable

19 thickness, reaching up to several meters within paleovalleys. This flow-unit, based on a 40Ar/39Ar

20 age of 561±1 ka on a sample collected in the Treja Valley near Calcata, was previously related to a

21 distinct event with respect to the UTGVT (Karner et al., 2001). However, new data discussed in the

22 previous sections evidence that no geochronologically appreciable time break occurred between the

23 emplacement of FAD-3A and UTGVT, despite the occurrence of poorly developed soils above

24 FAD3A and FAD-3B. Moreover, field observation for the present work lacks evidence of any

25 significant discontinuity between the LTGVT and UTGVT pyroclastic-flow deposits, suggesting a

26 co-eruptive origin. 1

2 Upper Tufo Giallo della Via Tiberina eruption unit a, b, c and d (UTGVT)

3 The UTGVT pyroclastic-flow deposit is characterized by a well-lithified, prevalent yellow ash

4 matrix, containing abundant yellow pumice, accretionary lapilli, unmetamorphosed sedimentary

5 lithic clasts, leucite and sanidine crystals, and subordinate lava clasts and clinopyroxene and biotite

6 crystals.

7 Three main horizons corresponding to as many eruptive phases without any significant evidence of

8 temporal break, consistent with the lack of intervening paleosols, are recognizable in the field

9 (Karner et al., 2001). They are represented by two pyroclastic-flow deposits (Unit a and b),

10 followed by alternating ash-, scoria-, and pumice-fall deposits (Unit c; Figure 5). These three units

11 yielded indistinguishable 40Ar/39Ar ages, providing a weighted mean of 552±10 ka (Karner et al.,

12 2001, Table 3), consistent with that of 546±3 ka yielded by the lower pyroclastic-flow unit sampled

13 in the Riano quarries of Via Tiberina (Karner and Renne, 1998, Figure 5, Table 3).

14 A fourth unit (d) has been recognized in this work and interpreted as the deposit of the UTGVT late

15 eruptive phase, based on its stratigraphic position above the main pyroclastic-flow deposit at the

16 locality of Via Casale Francalancia (Figure 1), 4 km south of Morlupo, without any evidence of

17 temporal break, and based on the occurrence of large ballistics (up to 20 cm in diameter), indicating

18 its proximal facies.

20 Compositional features of the TGVT eruptive cycle

21 The compositional features of the TGVT Eruption Cycle have been discussed in detail by Masotta

22 et al. (2010), who reported similar bulk trachy-phonolitic compositions for both white pumices and

23 black grey scoria. The Zr/Y vs Nb/Y diagram allows to recognize a clustering of the different units

24 of the TGVT eruption cycle in distinct compositional fields (Figure 6b). Some of these

25 compositional fields, when represented by three samples at least, have also sub-rectilinear trends

26 (e.g.: LTVT, FAD-3A), as previously outlined for the samples of TGCP and FAD-0 (Figure 6b). 1 However, apart from the least alkaline, dark scoria bulk samples plotting closer to the origin of the

2 axes, the reasons why the white pumice samples of each different eruptive unit plot in different

3 portions of the Zr/Y vs Nb/Y diagram are not easily reconciled with their homogeneous phono-

4 trachytic bulk compositions. In any case, these Zr/Y vs Nb/Y signatures should be regarded as a

5 distinctive feature of each erupted product, and used as a complementary tool for their correlation

6 with distal equivalents.

9 4.2.2.4 Late phase: Prima Porta Eruptive Cycle (514±3 ka)

11 Tufo Giallo di Prima Porta (TGPP; 517±6 ka)

12 The Tufo Giallo di Prima Porta (TGPP) was distinguished by Karner et al. (2001) from the Tufo

13 Giallo della Via Tiberina (to which it was previously attributed, de Rita et al., 1993), based on its

14 stratigraphic position (above the Tufo del Palatino from Colli Albani, dated 530±2 ka, Karner et al.,

15 2001) and 40Ar/39Ar age of 517±6 ka. It is a massive pyroclastic-flow deposit emplaced mainly in

16 the southern MSVD sector within the Paleo-Tiber valley. In the outcrops of Prima Porta (Figure 1),

17 it displays a well-lithified facies (Jackson et al., 2005), very similar to that of the units a and b of the

18 UTGVT, except for a lower pumice clast content. It also contains scarce, although characteristic,

19 grey, poorly vesicular, leucite- and clinopyroxene-bearing scoria clasts, up to 10 cm in diameter,

20 and displays a distinctive grey-greenish color within the semi-lithified facies exposed along the

21 southern tract of the Tiber valley, down to Rome (outcrops of the Capitol and Palatine Hills,

22 Corazza et al., 2004).

23 An accretionary lapilli-rich ash layer, representing the co-ignimbrite ash-cloud deposit, occurs at

24 the top of the pyroclastic flow deposit in several mid-distal sections. At the base of the pyroclastic

25 flow deposit, a Plinian-style fallout deposit, made up of inversely graded, highly vesicular white

26 pumice, lies on top of a mature, dark brown paleosoil and reaches a maximum thickness of 2.5 m in 1 the northern MSVD area. In Figure 8 b, representative pumice and lithic isopleths and isopachs

2 define a SW–NE-trending dispersal axis and indicate the Morlupo center as the source area. The

3 basal fallout pumice is characterized by vitrophyric texture (porphyricity index < 5% vol.) and high

4 vesicularity (vol. < 50%; computed after Carey and Sparks, 1986; Fierstein and Nathenson, 1992).

5 Rare euhedral sanidine (2 mm-sized) characterizes the phenocrysts assemblage, while sanidine and

6 clinopyroxene are frequent in the groundmass.

9 Grottarossa Pyroclastic Sequence (513±3 ka)

10 A sequence of dark grey ashy pyroclastic flow and subordinate fall deposits, essentially constituted

11 by mm- to cm-sized, poorly vesicular, dark grey scoria clasts with leucite, sanidine and

12 clinopyroxene, occurs along the northern Tiber River Valley above the TGPP. Karner et al. (2001)

13 identified four subunits in the Grottarossa Pyroclastic Sequence (GRPS –a through –d), including a

14 characteristic stratigraphic marker represented by a zoned, orange to black scoria-fall layer (subunit

15 b'-b"). The presence of small fossil trees at the base of each of the first three subunits suggests the

16 occurrence of intervening dormancies. However, based on the ages for units a and b of 519±6 ka and

17 511±9 ka, respectively (samples PAL-01 and SAX-01, Table 3, Appendix 2), it is not possible to

18 quantify the corresponding temporal gaps. We assessed the eruption age for the GRPS by the

19 combined weighted mean age of these samples, plus one sample collected at Cava Rinaldi (CR1,

20 510±4 ka, Table 3 and 8) and attributed in this work to this eruption sequence (see below), obtaining

21 513±3 ka. Since this age is not statistically distinguished with respect to that of 517±6 yielded by

22 TGPP, we consider all these deposits as part of a common eruptive cycle (Prima Porta Eruptive

23 Cycle), with a combined weighted mean age of 514±3 ka (Table 6).

24 On top of GRPS subunit d, a faintly pedogenized ash layer is present in the type-section of Via di

25 Grottarossa (Karner et al., 2001), overlain by a widespread lithic-rich breccia deposits, up to ~1 m

26 thick, containing dominantly holocrystalline lithic clasts with mm-sized clinopyroxene and dark 1 mica, and subordinate lava lithic clasts. Juvenile scoria clasts, up to cm-sized, are poorly vesicular

2 and porphyritic with mm-sized crystals of leucite. Although previously interpreted as the initial

3 deposit of the following eruptive cycle (Tufi Terrosi con Pomici Bianche; Karner et al., 2001),

4 dispersal area (Figure 8c) and depositional features (e.g., the occurrence of ballistic sags) suggest

5 the Morlupo center as source area.

7 Compositional features of the Prima Porta Eruptive Cycle

8 One pumice sample of the basal fallout of the TGPP yields TAS composition and Zr/Y vs Nb/Y

9 ratios comparable to those of the phonolitic white pumice of the UTGVT and FAD-2 (Figure 9a and

10 b). In contrast, the composition of one bulk sample of the distinctive coarse greenish scoria (TGPP-

11 ds) may be regarded as relatively primitive, consistent with its high MgO content (Appendix 5) and

12 its lower position in the Zr/Y vs Nb/Y diagram (Figure 9b).

13 Samples of juvenile clasts in the lithic-rich breccia of the GRPS, including one EMP analysis on

14 melt inclusion in clinopyroxene and two bulk XRF analyses on samples with LOI<3.5% (A and B

15 in Figure 9), also display relatively primitive, phonotephritic compositions (Figure 9a).

17 4.2.3 Sella di Corno Fall Layer (523±10 ka, Gaeta et al., 2003)

18 A deeply altered pumice fall deposit, that we tentatively correlate to the Sella di Corno (SdC)

19 Plinian fall layer cropping out in the Apennine mountain range and dated 523±10 ka (Gaeta et al.,

20 2003), is intercalated at several localities between the UTGVT and the TGPP; however its source

21 area remains undetermined.

22 No reliable major element analysis is available for this extremely altered (LOI 33.18%; Appendix

23 5) sample. However, the Zr/Y vs Nb/Y composition of one bulk sample collected at the type-

24 locality, quite similar to that of the earliest Southern Sabatini activity of Fall A1 (Figure 10b),

25 evidences a MSVD provenance for the SdC pumice fall deposit. Based on the age of 523±10 ka and

26 the consistent stratigraphic position below the TGPP (517±6 ka), this deposit may be regarded as an 1 early product of the Southern Sabatini phase of activity, overlapping the late period of the Morlupo

2 activity.

5 4.2.4 Southern Sabatini center (499±3 - 389±4 ka)

7 4.2.4.1 Tufi Terrosi Eruptive Cycle (499±3 - 490±4 ka)

9 The stratigraphy and the compositional features of the Tufi Terrosi con Pomici Bianche (TTPB;

10 Karner et al., 2001) has been described in detail by Sottili et al. (2004), who recognized four

11 eruptive units (A, B, C, D), mainly constituted of fallout deposits. These eruptive units comprise

12 alternating layers of white pumice and grey scoria clasts, grouped into several sub-units, separated

13 by thick, partially reworked and deeply altered ash beds. The fourth unit (Fall D) was emplaced

14 during the early phase of the 452±2 ka Tufo Rosso a Scorie Nere pyroclastic-flow forming eruption,

15 and is therefore treated in the corresponding section. A comprehensive stratigraphic scheme of the

16 complex TTPB succession cropping out at the type localities of Isola Farnese and Casale del Gallo

17 (Sottili et al., 2004) is reported in Figure 11.

19 Fall A, Fall B, Fall C

20 The high degree of alteration that affects the fallout deposits of the TTPB, mainly as a consequence

21 of the prolonged weathering that the deposits underwent during MIS 13 interglacial phase (see

22 Marra et al., 2011 for an in-depth discussion), makes it difficult to obtain high quality

23 geochronological and geochemical data on these products. Here, we discuss age determinations on

24 three samples out of a succession of four primary and two partially reworked pyroclastic deposits

25 (CR1, CR4, CR5, CR6, CR6B, CR7, Figure 11), interbedded within lacustrine sediments of the 1 Valle Giulia Formation (Karner and Marra, 1998), in comparison with two previous ages for the

2 TTPB (sample R93-11M, Karner et al., 2001; sample 08-ISFARNESE-01, Marra et al., 2011).

3 The age obtained for the volcaniclastic deposit CR1 occurring at the base of the Cava Rinaldi

4 succession (510±4 ka), coupled with its lithological and petrographic features and the stratigraphic

5 position above the TGPP, provides strong evidence of its correlation with the GRPS, which is dated

6 511±9 ka at Grottarossa (sample SAX-01, Karner et al., 2001; Figure 11, Table 3, Appendix 2).

7 This age does not overlap those of the overlying TTPB pumice samples at Cava Rinaldi (499±3,

8 496±9 ka), indicating the occurrence of two geochronologically distinct eruption cycles. In contrast,

9 it appears more problematic the correlation of the overlying fallout deposits with the Fall A, B and

10 C units and sub-units identified by Sottili et al. (2004) in the proximal settings, due to the lack of

11 analyzable glasses and to the large error associated with the 40Ar/39Ar age of Fall B at Isola Farnese

12 (494±14 ka). Therefore, to overcome these difficulties, we will rely on trace element compositions,

13 following the approach of Marra et al. (2011). These authors recognized distinct Zr/Y vs Nb/Y

14 compositional fields pertaining to samples of Fall A1, Fall B1 and Fall C1 analyzed by Sottili et al.

15 (2004) and Lancaster et al. (2010), and attributed two samples (GR, VT, Figure 10b) collected in

16 the mid-distal sections of Grottarossa and km 12.6 of Via Tiburtina (Figure 1 and 11), to the lower

17 Fall A1, based on their strict alignment with other four samples of this eruptive unit (CG-1, -2, -3,

18 and IF, Figure 10b). Similarly, we correlate the two lowest pumice layers of Cava Rinaldi (samples

19 CR4 and CR5) to the upper Fall A1 and to the Fall A2 subunits, respectively, based on their

20 alignment in the Zr/Y vs Nb/Y diagram with samples CG5 and CG9 of these eruptive deposits

21 analyzed in Sottili et al. (2004) (Figure 10b). This correlation is supported by the zoned character of

22 the lowest fallout deposit of Cava Rinaldi, with alternating white pumice and grey scoria, a feature

23 consistent with the proximal stratigraphy of upper Fall A1 and Fall A2 at Casale del Gallo (Sottili et

24 al., 2004; Figure 11). In contrast, the petrographic features and the younger age (490±4 ka), which

25 is statistically distinguished from that of CR5 (499±3 ka), strongly suggest correlation of sample

26 R93-11M collected at Ponte Galeria with Fall B. Based on these correlations, we have assessed the 1 age of Fall A at 499±3 ka and that of Fall B at 490±4 ka, since these ages, due to the small

2 associated errors, equate the combined mean weighted ages of the primary deposits attributed to

3 these eruption units (CR5 plus CR6B, and 08-ISFARNESE-01 plus R93-11M, respectively).

4 No age determination is available for the subsequent Fall C deposit. Following the trace-element

5 approach, indeed, we attribute also the upper grey scoria layers of Cava Rinaldi (samples CR6B,

6 CR7) to Fall A2, excluding correlation with Fall C1. Despite a TAS composition similar to that of

7 sample #1 of Fall C1 within or close to the MS-B field (dashed line in Figure 10a), samples CR6B

8 and CR7 display tight Zr/Y vs Nb/Y compositions similar to those of Fall A and within the MS-A

9 field of Figure 10b, corresponding to latitic bulk compositions. In contrast, samples of Fall C1

10 display a wide compositional range within the TAS and Zr/Y vs Nb/Y MS-B fields of Figure 10.

12 Compositional features of the TTPB eruptive cycle

13 The progressive clockwise rotation of the Zr/Y vs Nb/Y compositions from Fall B2 and Fall C1, to

14 upper Fall A1/A2, and to lower Fall A1 in the diagram of Figure 10b is consistent with a

15 phonotephritic-tephriphonolitic composition for the grey scoria and a more evolved, trachy-

16 phonolitic one for the white pumice of these eruptive units. Similarly, the grey scoria clasts of

17 subunit upper A2 plot closer to the origin of the axes with respect to the white pumice samples

18 (Figure 10b), according to the other differentiation trend associated to the Zr/Y vs Nb/Y

19 composition. These observations suggest the contribution of a progressively more primitive feeder

20 magma in the final stages of each eruptive event of the TTPB Eruptive Cycle, i.e., Fall A2 upper

21 (CR6b, CR7), Fall B2, and Fall C (sample #3). In particular, the progressive elongation of the Fall

22 C1 samples in the Zr/Y vs Nb/Y diagram is likely to parallel a progressive contribution of a more

23 primitive magma during eruption, passing from more (basal sample #1) to less evolved (upper

24 sample #3) compositions.

26 4.2.4.2 Tufo Rosso a Scorie Nere Eruptive Cycle (452±2 ka) 1

2 Tufo Rosso a Scorie Nere (TRSN; 452±2 ka), Fall E (450±7 ka), Fall F (447±7 ka)

3 The TRSN Eruption Sequence comprises a basal Plinian fall deposit (Fall D, Sottili et al., 2004) and

4 a voluminous ash and scoria flow deposit, characterized by the presence of coarse (up to 20 cm),

5 highly vesicular black scoria. The strong vapor-phase crystallization of zeolite minerals occurring in

6 the valley-fill portions confers a deep reddish color and strong lithification to the pyroclastic-flow

7 deposit, hence the historical name of "Tufo Rosso a Score Nere" (Red Tuff with Black Scoria)

8 (Mattias and Ventriglia, 1970). The unlithified facies are instead characterized by homogeneous

9 dark grey color ("Tufo Grigio Sabatino", Mattias and Ventriglia, 1970). A certain degree of

10 misplacement occurs in the literature about the identification of the TRSN erupted at 450 ka in the

11 MSVD and the analogous pyroclastic-flow deposit with the same name erupted at 150 ka from the

12 Vico volcano (Vico C; Cioni et al., 1993). Also the lithified facies of the TRSN characterized by the

13 presence of elongated scoria or fiamme, commonly referred to as "Peperini listati", was previously

14 misinterpreted as erupted by the Vico or the Vulsini districts, whereas the local names of "Piperno"

15 and "Nenfro", which are commonly used for different pyroclastic products of these volcanoes, are

16 sometimes attributed to the TRSN cropping out in the northern sector of the MSVD.

17 The TRSN pyroclastic flow was dated at 452±2 ka (Karner et al., 2001), in good agreement with the

18 previous 40Ar/39Ar dating of 449±6 ka (Cioni et al., 1993). Based on the ages obtained in this work,

19 it was rapidly followed by the emplacement of two Plinian-style pumice fall deposits, named Fall E

20 and Fall F, at 450±7 and 447±7 ka, respectively (Figure 13, Table 2). Fall E reaches 50 cm in

21 thickness at the Prima Porta type section with an eastward dispersal smaller than Fall A and B,

22 which are spread southeast through the city of Rome and the Colli Albani area (Sottili et al., 2004;

23 Marra et al., 2009). Fall F possibly shows an even more limited and eastward distribution: up to

24 now it has been only recognized at the Prima Porta type section, in an outcrop located 4 km west of

25 Morlupo, and at two sites along the eastern side of the Tiber River valley (Figures 1, 13).

26 1 Compositional features of the TRSN eruptive cycle

2 Glass compositions of the TRSN black scoria, the white pumice of basal Fall D and later Fall E plot

3 at the transition between the trachyte and the phonolite fields; they define a strictly clustered

4 compositional field (light grey area) in the TAS diagram (Figure 12a) together with the white

5 pumices of Fall A and Fall B1 (short-dashed field). This is a distinct, higher-SiO2 field with respect

6 to that defined by the white pumice of the Morlupo eruption cycles (long-dashed field in Figure

7 12a). No analyzable glass occurs in the deeply altered Fall F deposit; however, EMP analyses of

8 melt inclusions in clinopyroxene suggest a phono-tephritic magma composition.

9 In contrast to the clustered TAS compositions, the Zr/Y vs Nb/Y compositions of Fall D, TRSN and

10 Fall E are spread through the MS-A field in Figure 12b, and overlap those of FAD-2, UTGVT and

11 TGPP. The grey scoria of Fall F has instead a primitive MS-B composition in both diagrams of

12 Figure 12.

14 4.2.4.3 Late Southern Sabatini Succession (389±4 - 379±40 ka)

16 No volumetrically significant eruptive activity occurred in the MSVD from 450 ka until around 315

17 ka, as suggested by the lack of corresponding products within this time span (Sottili et al., 2010),

18 and also supported by the stratigraphy of the Via San Abbondio type-section (near the town of

19 Riano; Figure 13), investigated in this work. At this locality, the late products of the Southern

20 Sabatini activity overlie two pumice fall layers attributed to the early Vico activity (i.e., Vico and

21 Vico of Cioni et al., 1987), based on stratigraphic and geochemical data presented in this paper

22 (Figure 14b, Table 4, and Appendix 5).

23 In order to assess the provenance of the 412±2 ka and 418±6 ka "Bedded Pumice" of Karner et al.

24 (2001), occurring within the fluvial-lacustrine deposits of the San Paolo Formation (Karner and

25 Marra, 1998) at Ponte Galeria and at the Capitoline Hill (Rome), respectively (Figure 14a), we

26 compared their geochemical composition to that of the coeval products from Vico (Vico and Vico 1 , 419±6 - 403±6 ka; Cioni et al., 1993; Barberi et al., 1994; = Rio Ferriera Formation, Perini et al.,

2 2004), that we sampled at the type-locality of San Martino, 2 km south of Civita Castellana, and at

3 Via San Abbondio (Figure 1, Figure 14b, c). The white pumice bulk samples from Ponte Galeria

4 and Capitoline Hill (C7 and 07-FC-SP-01) display trachytic composition alike the bulk samples of

5 the Rio Ferriera Formation analyzed by XRF technique (Perini et al., 2004; light grey field V1a in

6 Figure 14b). The EMP glass compositions provided in the present work for the Vico- samples,

7 collected from the central portion of the deposits at San Martino and Via San Abbondio localities,

8 representing the climactic eruption phase, plot at the rhyolitic extreme of this field. Consistent with

9 the indistinguishable radiometric ages of the "Bedded Pumice" and Vico-(the Vico- deposit at

10 San Martino yielded 412±7 and 419±6 ka; Barberi et al., 1994), their correlation can be thus

11 assumed as reliable.

12 In addition, consistent with the compositional features of Period I of activity at Vico, which is

13 characterized by a continuous mixing of latitic (V1b in Figure 14b) and trachytic magmas (V1a)

14 (Cioni et al., 1987; Perini et al., 2004), we interpret the two dark scoria fall deposits dated at 427±5

15 and 412±5 ka (R94-30C and TDC-DSL) occurring at the sections of Prima Porta and Tenuta di

16 Capannacce (Figure 1 and 13) to represent less differentiated products of the same phase of the

17 Vico activity that emplaced the trachytic pumices. The identical Zr/Y vs Nb/Y signature of these

18 dark scoria samples, plotting close to the Vico- samples analyzed in this work (Figure 14c),

19 strongly supports this correlation.

20 Based on these correlations, no products attributable to the MSVD are found between the TRSN

21 Eruption Cycle and the San Abbondio Ash-lapilli Succession (SAAS), which is a rather

22 homogeneous, more than 7 m thick deposit of alternating dark grey, poorly vesicular scoria lapilli

23 and ash showing incipient pedogenization (Figure 13). Two samples collected at the base and at the

24 top of the succession (SA- C5 and SA-C4) display MS-B magma composition on the Zr/Y vs Nb/Y

25 diagram, and a consistent poorly differentiated TAS bulk composition (Figure 12). The SAAS may

26 be related to a strombolian activity occurred after the end of the Southern Sabatini volcanic phase, 1 since 389±4 ka (Sample SA-C5; Table 2, Figure 13). A poorly constrained upper age of 379±40 ka

2 has been obtained on a sample collected at the top of the SAAS (SA-C4, Figure 13).

4 5. Tephrostratigraphic implications

6 5.1 Compositional characterization of the MSVD eruptive products

7 Figure 15 summarizes the results of the geochemical and geochronological investigations

8 performed in this work, aimed at characterizing the explosive activity occurred in the MSVD in the

9 time span 800-370 ka. At least seven major eruptions emplacing five sub-Plinian to Plinian-style

10 pumice fall horizons and two pyroclastic-flow deposits are recorded in the mid-distal setting during

11 the earliest phase of activity spanning 808-614 ka (Figure 15a). Although no reliable major-element

12 analyses are provided for these tephras, their Zr/Y vs Nb/Y signature indicates that they belong to

13 the MSVD activity (Figure 15b). Nine, geochronologically distinct, major explosive cycles

14 characterized the main MSVD activity between 589 and 447 ka, emplacing at least thirteen

15 widespread fallout deposits, with an eastward to southeastward, far-reaching dispersal. A long,

16 relative dormancy is recorded in the MSVD until ca. 315 ka, when a new volcanic phase started at

17 the Bracciano center.

18 EMP glass compositions of the MSVD products are clustered in the trachy-phonolitic field

19 of the TAS diagram (Figure 15d), except for a minority of products, erupted in the final stages of

20 each large explosive cycle (Fall F, GRPS-e), which display more primitive, phonotephritic

21 composition. This is in good agreement with previous studies on the effusive activity (Conticelli et

22 al., 1987), showing a single series of evolution for the MSVD magma, from tephrites to phonolites.

23 Most of the analyzed products are characterized by Zr/Y vs Nb/Y compositions clearly

24 distinguished from those of the other volcanic districts of Central Italy (Figure 15b-c), attesting that

25 this geochemical signature can be used to identify the provenance from the MSVD of relatively

26 altered deposits, in particular distal tephra layers, such as those of the MSVD Paleo-activity. In this 1 case, the good concordance of the Zr/Y vs Nb/Y compositions of two couples of tephra layers

2 recovered in different boreholes and in different stratigraphic contexts (I9-B and PTS14-A, and I9-

3 A and I7-A, Figure 16a), combined with their stratigraphic position (Figure 16b) allows us to

4 identify them as derived from the same eruptions (Paleotiber Units B and C, respectively). This also

5 allows us to compute a better-constrained mean weighted age for the eruptive events, by combining

6 the ages of the samples (Figure 16a).

7 Although the very similar composition of sample PTS6-A and samples I7-A and I9-A would

8 suggest their correlation (Figure 16a), geochronological and stratigraphic evidence instead suggests

9 to assign the former one to a fourth, distinct unit (Unit d). This points out that the Zr/Y vs Nb/Y

10 signature cannot be considered a unique feature of each eruptive unit. Therefore, other than

11 stratigraphical, chronological or geochemical indicators, it represents an auxiliary tool to verify a

12 possible correlation. Indeed, the following examples demonstrate that when used in combination

13 with other geochemical indexes, e.g. by crossing trace-element and glass compositions, the trace-

14 element dataset provided in this paper can be used to fingerprint the dated MSVD eruption units,

15 allowing the identification of distal tephra layers.

18 5.2 Potential of the Zr/Y vs Nb/Y diagram for tephrostratigraphic purposes

19 We have shown above the potentiality of this method in attributing the mid-distal fallout deposits of

20 Cava Rinaldi to Fall A2 sub-unit: in this case, the application has been used backward to assign the

21 age of the dated mid-distal occurrences to the proximal, undated products. Obviously, the same

22 procedure might be applied to tephra layers in distal settings and thus be used as a potential,

23 additional tool for the broader purposes of tephrostratigraphy. In order to test the reliability of the

24 Zr/Y vs Nb/Y for discriminating individual tephra layers, we applied this method to two distal

25 fallout deposits occurring in the Middle Pleistocene sedimentary successions of central-southern

26 Apennines, for which EMP glass compositions were available. 1 The first test was applied to the tephra layer SC3, from the Middle Pleistocene lacustrine sediments

2 of the Mercure basin, southern Italy. Based on its EMP glass composition and Sr isotope ratio and

3 on the 40Ar/39Ar ages of 516.5±3.6 ka and 493.1±10.9 ka of two sandwiching tephra layers, the

4 SC3 layer has been confidentially attributed to the Plinian Fall A eruption (c 499 ka; Giaccio et al.,

5 2014). The Zr/Y vs Nb/Y composition of the SC3 tephra (Figure 17a) confirms its attribution to the

6 MSVD. In particular, SC3 plots closer to the lower Fall A1 pumice, supporting the correlation with

7 the TTPB. On the other hand, in the Zr/Y vs Nb/Y diagram, the Fall A field overlaps that of the

8 Sella di Corno fall deposit (Figure 17a), and thus it cannot be excluded a possible correlation of

9 SC3 to the Sella di Corno unit. Indeed, only the combination of Zr/Y vs Nb/Y diagram with the

10 ordinary major element glass composition allows us to unambiguously correlate the most

11 differentiated composition (i.e., the phonolitic component) of the SC3 tephra to the basal white

12 pumices of the zoned Fall A unit.

14 The second test has been applied to the SUL1/5-3 layer from the Middle Pleistocene lacustrine

15 succession of the Sulmona basin, central Italy (see Giaccio et al., 2009, 2013a). The stratigraphic

16 position of SUL1/5-3 between the Tufo di Bagni Albule tephra (ca. 530 ka; Giaccio et al., 2013a, b)

17 and the Fall A (ca. 499 ka; SUL5-1c in Giaccio et al., submitted; Figure 15b) and Pozzolane Rosse

18 (ca. 457 ka; Giaccio et al., 2013a) distal tephras, provides age constraints suggesting a possible

19 correlation either with the TGPP (517±6 ka) or the Sella di Corno fallout (523±10 ka). Actually,

20 EMP glass composition of SUL1/5-3 is compatible, yet not identical, to that of the TGPP, while a

21 reference analysis for SdC is not available (Figure 17b). However, Zr/Y vs Nb/Y composition of

22 sample SUL1-3 (Figure 17a), besides confirming the attribution to the MSVD activity, is quite

23 similar to that of the SdC fallout, whereas it is incompatible with that of TGPP. Therefore, even in

24 the lack of EMP data, the Zr/Y vs Nb/Y composition, coupled to the general chronostratigraphic

25 context in which SUL1/5-3 occurs, allow us a confident attribution of this tephra to the SdC unit. 1 We remark that the slightly shifted position of the Zr/Y vs Nb/Y compositions of samples SC3 and

2 SUL 1/5-3 with respect to those of the Fall A and Sella di Corno proximal samples in Figure 15a

3 may reflect a small variation of the ratios, due to the different degree of porfiricity of the distal

4 deposits with respect to the proximal ones.

5 Although the examples provided point out some limits of the Zr/Y vs Nb/Y diagram for

6 tephrostratigraphic purposes, when applied in combination with the EMP glass composition, it may

7 provide a fundamental tool, especially for the developing of the currently barely explored Middle

8 Pleistoce tephrostratigraphy. It is known, in fact, that with exception of the very idiosyncratic Colli

9 Albani volcanic tephras (Giacco et al., 2013b), the products from the intense, broadly

10 contemporaneous, Middle Pleistocene explosive activities of the different ultrapotassic Peri-

11 Tyrrhenian volcanoes (i.e., Vulsini, Sabatini, Vico and Roccamonfina) are compositionally rather

12 monotonous and hardly discriminating each other via EMP composition, being dominated by

13 similar trachy-phonolite/tephri-phonolite compositions (e.g., Peccerillo, 2005). For instance, it has

14 been recently demonstrated that the EMP data alone are not sufficient for discerning the potential

15 sources of a number of trachy-phonolite/tephri-phonolitic tephras of the Middle Pleistocene

16 Mercure lacustrine succession (Giaccio et al., submitted), and this indeed applies to other Middle

17 Pleistocene Italian tephrostratigraphic records (e.g., Acerno basin, Petrosino et al., in press). Only

18 the combination of the EMP and Sr isotope data allowed the source of those Mercure tephra to be

19 identified (Giaccio et al., 2014). In this perspective, the Zr, Y an Nb trace elements might indeed

20 have a great potential, because their concentration in the pyroclastic deposits varies appreciably and

21 significantly from district to district, much more than major elements (Marra and D'Ambrosio,

22 2012). In other words, similarly to what has been shown for the Sr isotopes (Giaccio et al.,

23 submitted), the Zr/Y vs Nb/Y diagram might be suitably used for discriminating the sources of

24 tephras that display major element compositions compatible with different volcanoes and thus are

25 not distinguishable on the basis of the EMP data alone.

26 1

2 Summary and concluding remarks

3 New stratigraphic and 40Ar/39Ar chronological data, major element electron microprobe (EMP)

4 glass compositions, major and trace element XRF bulk compositions, and major and trace element

5 FUS-ICP-MS bulk compositions have been obtained for the major eruptive units from the early

6 phase of explosive activity (800-390 ka) in the Monti Sabatini Volcanic District (MSVD).

7 We have described and chronologically and compositionally characterized seven eruptive units: the

8 Tufo Giallo di Castelnuovo di Porto (TGCP, 589±4 ka); the First Ash Fall Deposit 2 (FAD 2,

9 558±14 ka); the First Ash Fall Deposit 3 (FAD 3, 546±5 ka); the Fall A (499±3 ka – 496±9 ka)

10 from the “Tufi Terrosi con Pomici Bianche” succession; the Fall E (450±6 ka) and Fall F (447±7

11 ka) from the “Tufi Stratificati Varicolori de La Storta”; and the San Abbondio Ash-lapilli

12 Succession (SAAS, 389±4 ka). Moreover, compositional features have been obtained from

13 previously dated MSVD units (Tufo Giallo di Prima Porta, Grotta Rossa Pyroclastic Sequence, Fall

14 B and Fall C) and interbedded Plinian fall deposits from Vico volcanic district (Vico and Vico ).

15 This new dataset substantially improve the general knowledge on the 0.8-0.4 Ma explosive activity

16 of the Sabatini volcanic district and provides crucial and reliable data for tracing the individual

17 investigated unit in distal settings, with significant implications for the development of Middle

18 Pleistocene tephrostratigraphic studies in the Central Mediterranean area, hitherto prevented by the

19 lack of robust reference data.

20 Under this perspective, in addition to provide the commonly used data for tephrostratigraphic

21 purposes (e.g. EMP glass compositions and 40Ar/39Ar chronological data), here we have shown the

22 potential of the trace elements for discriminating the volcanic sources of tephras sharing similar

23 major element compositions.

26 1 Acknowledgements

3 40Ar/39Ar age analyses performed for this work were funded by Istituto Nazionale di Geofisica e

4 Vulcanologia, Italy. FUS-ICP-MS analyses were co-funded by INGV, Dipartimento di Scienze

5 della Terra, Sapienza-Università di Roma, Italy, and Department of Geosciences - Georgia State

6 University - Atlanta, U.S.A. We wish to thank Danilo Chiocchini of the Dipartimento di Scienze

7 della Terra of the University of Perugia, who performed XRF chemical analyses, and Marcello

8 Serracino of CNR-IGAG of Rome, for technical assistance during the EMP analyses.

9 Finally, we acknowledge Gianni Zanchetta for insightful suggestions on a previous version of this

10 manuscript and Gianluca Iezzi for his detailed review; both contributions helped us to improve the

11 quality of this work.

13 Supplementary material provided online

14 Supplementary Material item #1: Petrographic features of the volcanic products of the MSVD 15 Paleo-activity 16 Appendix 1 - Full 40Ar/39Ar data performed at the University of Wisconsin-Madison Rare Gas

17 Geochronology Laboratory.

18 Appendix 2 - Full 40Ar/39Ar data performed at the Berkeley Geochronology Center on the Cava

19 Rinaldi samples.

20 Appendix 3 - Weighted mean ages re-calculated in this work from original reduction data in Karner

21 and Renne, 1998 and Karner et al., 2001a.

22 Appendix 4 - Full EMP analytical compositions of samples analyzed in this work.

23 Appendix 5 - Major and trace element compositions of samples analyzed by Fusion ICP-MS at

24 Activation Laboratories, Ancaster, Ontario, Canada.

25 1 References

3 Alvarez, W., 1972. The Treia valley north of Rome: volcanic stratigraphy, topographic evolution,

4 and geological influences on human settlement. Geologica Romana 11, 153-176.

6 Alvarez, W., 1973. Ancient course of the Tiber river near Rome: an introduction to the Middle

7 Pleistocene volcanic stratigraphy of Central Italy. Geol. Soc. Am. Bull. 84, 749-758.

9 Alvarez, W., Gordon, A., Rashak, E. P., 1975. Eruptive Source of the "Tufo Rosso a scorie Nere", a

10 Pleistocene Ignimbrite North of Rome. Geologica Romana 14, 141-145.

12 Barberi, F., Buonasorte, G., Cioni, R., Fiordelisi, A., Foresi, L., Iaccarino, S., Laurenzi, M.A.,

13 Sbrana, A., Vernia, L., Villa, I.M., 1994. Plio-Pleistocene geological evolution of the geothermal

14 area of Tuscany and Latium. Mem. Descr. Carta Geol. d'It. 49, 77-134.

16 Cann, J.R., 1970. Rb, Sr, Y, Zr, Nb in some ocean floor basaltic rocks. Earth Planet. Sci. Lett. 10, 7-

17 11.

19 Carey, S.N., Sparks, R.S.J., 1986. Quantitative models of the fallout and dispersal of tephra from

20 volcanic eruption columns. Bull. Volcanol. 48, 109-125.

22 Cioni, R., Sbrana A., Bertagnini, A., Buonasorte, G., Landi, P., Rossi, U., Salvati, L., 1987.

23 Tephrostratigraphic correlations in the Vulsini, Vico and Sabatini volcanic successions. Periodico di

24 Mineralogia 56, 137-155.

25 1 Cioni, R., Laurenzi, M.A., Sbrana A., Villa I.M., 1993. 40Ar/39Ar chronostratigraphy of the initial

2 activity in the Sabatini volcanic complex (Italy). Boll. Soc. Geol. It. 112, 251-263.

4 Conticelli, S., Francalanci, L., Manetti, P., Cioni, R., Sbrana, A., 1997. Petrology and geochemistry

5 of the ultrapotassic rocks from the Sabatini Volcanic District, central Italy: the role of evolutionary

6 processes on the genesis of variably enriched alkaline magmas. J. Volcanol. Geotherm. Res. 75,

7 107-136.

9 Corazza, A., Lombardi, L., Marra, F., 2004, La geologia del Colle Capitolino. Il Quaternario 17,

10 413-441.

12 Corda L., de Rita D., Tecce F., Sposato A., 1978. Le piroclastiti del sistema vulcanico sabatino: il

13 complesso dei tufi stratificati varicolori de La Storta. Boll. Soc. Geol. Ital. 27, 353-366.

15 de Rita, D., Funiciello, R., Rossi, U., Sposato, A., 1983. Structure and evolution of the Sacrofano-

16 Baccano caldera, Sabatini Volcanic Complex, Rome: J. Volcanol. Geotherm. Res. 17, 219-236.

18 de Rita, D., Funiciello, R., Corda, L., Sposato, A., Rossi, U., 1993. Volcanic Units. In: Di Filippo,

19 M., (Ed.), Sabatini Volcanic Complex, Quad. Ric. Sci. 114, Progetto Finalizzato Geodinamica

20 C.N.R., Roma, 33-79.

22 Fierstein, J., Nathenson, M., 1992. Another look at the calculation of fallout tephra volumes. Bull.

23 Volcanol. 54, 156-167.

24 1 Florindo, F., Karner, D.B., Marra, F., Renne, P.R., Roberts A.P., Weaver, R., 2007. Radioisotopic

2 age constraints for glacial terminations IX and VII from aggradational sections of the Tiber River

3 delta in Rome, Italy. Earth Planet. Sci. Lett. 256, 61-80.

5 Floyd, P.A., Winchester, J.A., 1975, Magma type and tectonic setting discrimination using

6 immobile elements. Earth Planet. Sci. Lett. 27, 211-218.

8 Franzini, M., Leoni M., Saitta, M., 1972. A simple method to evaluate the matrix effects in X-ray

9 fluorescence analysis. Spectrometry 1, 151-154.

11 Foley, S., Jenner, G., 2004. Trace element partitioning in lamproitic magmas - the Gaussberg

12 olivine leucitite. Lithos 75, 19-38. doi: 10.1016/j.lithos.2003.12.020.

14 Gaeta, M., Palladino, D.M., Karner, D.B., Renne, P.R., 2003. Vulcanoclastiti della Valle del Corno

15 (vvc). In: Centamore E., Dramis F., (Eds.), Note Illustrative della Carta Geologica d'Italia alla scala

16 1:50.000 - foglio 358 Pescorocchiano. Regione Lazio, 34-35.

18 Galli, P., Giaccio, B., Messina, P., 2010. The 2009 central Italy earthquake seen through 0.5 Myr-

19 long tectonic history of the L‟Aquila faults system. Quaternary Science Reviews 29, 3768e3789.

21 Giaccio B, Messina P, Sposato A, et al. 2009. Tephra layers from Holocene lake sediments of the

22 Sulmona basin, central Italy: implications for volcanic activity in peninsular Italy and

23 tephrostratigraphy in the central Mediterranean area. Quaternary Science Reviews 28: 2710–2733.

25 Giaccio, B., Arienzo, I., Sottili, G., Castorina, F., Gaeta, M., Nomade, S., Galli, P., Messina P.,

26 2013a. Isotopic (Sr-Nd) and major element fingerprinting of distal tephras: an application to the 1 Middle-Late Pleistocene markers from the Colli Albani volcano, central Italy. Quaternary Science

2 Reviews 67, 190-206.

4 Giaccio, B., Castorina, F., Nomade, S., Scardia, G., Voltaggio, M., Sagnotti, L., 2013b. Revised

5 chronology of the Sulmona lacustrine succession, central Italy. Journal of Quaternary Science, in

6 print. DOI: 10.1002/jqs.2647.

8 Giaccio, B., Galli, P., Peronace E., Arienzo, I., Nomade, S., Cavinato, G.P., Mancini, M., Messina,

9 P., Sottili, G., 2014. A 560-440 ka tephra record from the Mercure basin, southern Italy:

10 volcanological and tephrochronological implications. Journal of Quaternary Sciences, in print.

12 Jackson, M.D., Marra, F., Hay, R.L., Cawood, C., Winkler, E., 2005. The judicious selection and

13 preservation of tuff and travertine building stone in ancient Rome. Archaeometry 47, 3, 485–510.

15 Karner, D.B., Renne, P.R., 1998. 40Ar/39Ar geochronology of Roman Volcanic Province tephra in the

16 Tiber River Valley: Age calibration of middle Pleistocene sea-level changes. Geol. Soc. Am. Bull.

17 110, 740-747.

19 Karner D.B. & Marra F., 1998. Correlation of Fluviodeltaic Aggradational Sections with Glacial

20 Climate History: A Revision of the Classical Pleistocene Stratigraphy of Rome. Geol. Soc. Am.

21 Bull. 110, 748-758.

23 Karner, D.B., Juvigne´, E., Brancaccio, L., Cinque, A., Russo Ermolli, E., Santangelo, N.,

24 Bernasconi, S., Lirer, L., 1999. A potential early middle Pleistocene tephrostratotype for the

25 Mediterranean Basin: the Vallo di Diano, Campania, Italy. Global and Planetary Change 21, 1–15.

26 1 Karner, D.B., Marra, F., Renne, P., 2001. The history of the Monti Sabatini and Alban Hills

2 volcanoes: groundwork for assessing volcanic-tectonic hazards for Rome. J. Volcanol. Geotherm.

3 Res. 107, 185-219.

5 Kaye, M.J., 1965. X-ray fluorescence determinations of several trace elements in some standard

6 geochemical samples. Geochemistry and Cosmochemistry Acta 29, 139-142.

8 Kuiper, K.F., Deino, A., Hilgen, F.J., Krijgsman, W., Renne, P.F., Wijbrans, J. R., 2008.

9 Synchronizing rock clocks of Earth history. Science 320, 500–504. doi:10.1126/ science.1154339.

11 Lancaster, L.C., Sottili, G., Marra, F., Ventura G., 2010. Provenancing of Light Weight Volcanic

12 Stones Used in Ancient Roman Concrete Vaulting: Evidence from Rome. Archaeometry 53, 707-

13 727. doi: 10.1111/j.1475-4754.2010.00565.x

15 Laurenzi, M.A., Villa, I.M., 1987. 40Ar/39Ar chronostrastigraphy of Vico ignimbrites. Periodico di

16 Mineralogia 56, 285-293.

18 Lowe, D.J., 2011. Tephrochronology and its application: A review. Quaternary Geochronology 6,

19 107-153.

21 Marra, F., Florindo, F., Karner, D.B., 1998. Paleomagnetism and geochronology of early Middle

22 Pleistocene depositional sequences near Rome: comparison with the deep sea O climate record.

23 Earth Planet. Sci. Lett. 159, 147-164.

24 1 Marra, F., Florindo, F., Boschi E., 2008. The history of glacial terminations from the Tiber River

2 (Rome): insights to glacial forcing mechanisms. Paleoceanography 23, PA2205.

3 doi:10.1029/2007PA001543.

5 Marra, F., Karner, D.B., Freda, C., Gaeta, M., Renne, P.R., 2009. Large mafic eruptions at the

6 Alban Hills Volcanic District (Central Italy): chronostratigraphy, petrography and eruptive

7 behavior. Journ. of Volc. and Geoth. Res. 179, 217-232. doi:10.1016/j.jvolgeores.2008.11.009

9 Marra, F., Deocampo, D., Jasckson, M.D., Ventura, G., 2011. The Alban Hills and Monti Sabatini

10 volcanic products used in ancient Roman masonry (Italy): an integrated stratigraphic,

11 archaeological, environmental and geochemical approach. Earth-Science Reviews 108, 115-136.

12 doi:10.1016/j.earscirev.2011.06.005

14 Marra, F., D'Ambrosio, E., Sottili, G., Ventura G., 2012. Geochemical fingerprints of volcanic

15 materials: Identification of a pumice trade route from Pompeii to Rome. Geol. Soc. Am. Bull., in

16 print. doi: 10.1130/B30709.1

18 Marra, F., D'Ambrosio, E., 2012. Trace-element classification diagrams of pyroclastic rocks from

19 the volcanic districts of Central Italy: the case study of the ancient Roman ships of Pisa.

20 Archaeometry, in print. doi: 10.1111/j.1475-4754.2012.00725.x

22 Masotta, M., Gaeta, M., Gozzi, F., Marra, F., Palladino, D.M., Sottili, G., 2010. H2O- and

23 temperature-zoning in magma chambers: the example of the Tufo Giallo della Via Tiberina

24 eruptions (Sabatini Volcanic District, central Italy). Lithos 118, 119-130.

25 1 Mattias, P.P., Ventriglia, U., 1970. La regione vulcanica dei monti Sabatini e Cimini. Mem. Soc.

2 Geol. It. 95, 831-849.

4 Min, K., Mundil, R., Renne, P.R., Ludwig, K.R., 2000. A test for systematic errors in 40Ar/39Ar

5 geochronology through comparison with U/Pb analysis of a 1.1-Ga rhyolite. Geochemical

6 Cosmochemical Acta 64, 73-98.

8 Munno, R., Petrosino, P., Romano, P., Russo Ermolli, E., Juvigne´ , E., 2001. A late Middle

9 Pleistocene climatic cycle in southern Italy inferred from pollen analysis and tefrostratigraphy of

10 the Acerno lacustrine succession. Geographie physique et Quaternaire 55, 87–99.

12 Nappi G., De Casa, G., Volponi, E., 1979. Geologia e caratteristiche tecniche del „Tufo Giallo della

13 Via Tiberina‟. Mem. Soc. Geol. It. 98, 431-445.

15 Pearce J.A., Cann J.R., 1973. Tectonic setting of basic volcanic rocks determined using trace

16 element analyses. Earth. Planet. Sci. Lett. 19, 290-300.

18 Pearce J.A., Norry, M., 1979. Petrogenetic Implications of Ti, Zr, Y, and Nb Variations in Volcanic

19 Rocks. Contrib. Mineral. Petrol. 69, 33-47.

21 Pearce, J.A., 1996. A users guide to basalt discrimination diagrams, Trace Element Geochemistry of

22 Volcanic Rocks: Applications for Massive Sulphide Exploration. Geological Association of

23 Canada, Short Course Notes 12, 79-113.

25 Peccerillo, A., 2005. Plio-Quaternary volcanism in Italy: Petrology, geochemistry, geodynamics.

26 Springer-Verlag, Berlin. 1

2 Perini, G., Francalanci, L., Davidson, J.P., Conticelli, S., 2004, Evolution and genesis of magmas

3 from Vico volcano, Central Italy: multiple differentiation pathways and variable parental magmas.

4 Journal of Petrology 45, 139–182.

6 Petrosino, P., Jicha, B., Mazzeo, F.C., Russo Ermolli, E.A. High resolution tephrochronological

7 record of MIS 14-12 in the Southern Apennines (Acerno basin, Italy). Jour. of Volcanol. and

8 Geotherm. Res., in print.

10 Scherillo, A., 1940, I tufi litoidi a scorie nere della regione Sabazia e Cimina. Periodico di

11 Mineralogia 11, 301-338.

13 Scherillo, A., 1947. I Vulcani Sabatini. Bollettino della Società Naturalista di Napoli 55, 125-130.

15 Smith, M.E., Singer, B.S., Carroll, A.R., Fournelle, J.H., 2008. Precise dating of biotite in distal

16 volcanic ash: Isolating subtle alteration using 40Ar/39Ar laser incremental heating and electron

17 microprobe techniques. American Mineralogy 93, 784-795.

19 Sottili, G., Palladino D.M., Zanon V., 2004. Plinian activity during the early eruptive history of the

20 Sabatini Volcanic District, Central Italy. Jour. of Volcanol. and Geotherm. Res. 135, 361-379.

22 Sottili, G., Palladino, D.M., Marra, F., Jicha, B., Karner, D.B.,and Renne, P.F., 2010.

23 Geochronology of the most recent activity in the Sabatini Volcanic District, Roman Province,

24 central Italy. Jour. of Volcanol. and Geotherm. Res. 196, 20-30.

26 1 FIGURE CAPTIONS

3 Figure 1) Digital elevation map of the studied area showing location of: a) type-sections described

4 in the present work; b) other investigated sites; c) boreholes; d) buried fault.

6 Figure 2) Composite chronostratigraphic log of the Monti Sabatini Volcanic District, showing the

7 relationships with the mid-distal deposits intercalated within the fluvio-lacustrine successions of the

8 Paleo-Tiber River. Location of the samples dated by 40Ar/39Ar method in this and previous work is

9 also shown.

11 Figure 3) a) Zr/Y vs. Nb/Y compositional fields of the different volcanic districts of the Roman

12 Magmatic Province compared to the distribution of all the samples of the Monti Sabatini Volcanic

13 District for which trace-element analyses are provided in the literature (modified from Marra and

14 D'Ambrosio, 2012). One principal compositional field for the MSVD (MS-A') displays very limited

15 overlap with those of all the other districts, allowing for identification of the source area of the

16 products. Compositional fields for the Colli Albani products from Marra et al. 2011: PR: Pozzolane

17 Rosse; PN: Pozzolane Nere; VS: Villa Senni Eruptive Sequence; b) Zr/Y vs. Nb/Y compositions of

18 the samples of the Paleo-activity of the MSVD. Location of the boreholes (PT2b, I9, I7, PTS6,

19 PTS14, ING01), dated tephra occurrences and analyzed samples are shown in Figure 1.

21 Figure 4) a) Total alkali vs. silica (TAS) EMP glass compositions of 22 samples analyzed in this

22 work (Table 4, Appendix 4); b) Average EMP glass compositions to compare with the Zr/Y vs.

23 Nb/Y diagrams for all the bulk and glass samples (c).

25 Figure 5) a) Chrono-stratigraphic relationships of the products of the Tufo Giallo di Castelnuovo di

26 Porto and Tufo Giallo della Via Tiberina eruptive cycles, from the type sections described in this 1 and in previous work (see Figure 1 for location). The location of the dated (Table 2, 3) and analyzed

2 (Table 4, 5, Appendix 4, 5) samples is shown; b) Photographs of the volcanic deposits cropping out

3 at the type-sections of Morlupo and Capena.

5 Figure 6) a) EMP glass and selected bulk compositions in the TAS diagram; b) Zr/Y vs. Nb/Y

6 compositions of samples of the Tufo Giallo di Castelnuovo di Porto and Tufo Giallo della Via

7 Tiberina eruptive cycles, analyzed in this work.

9 Figure 7) Chrono-stratigraphic relationships among the mid-distal exposures of the Tufo Giallo di

10 Castelnuovo di Porto eruptive cycle described in previous literature (see Figure 1 for location), with

11 respect to the proximal exposures described in this work. The location of the dated (Table 2, 3) and

12 analyzed (Table 4, 5, Appendix 4, 5) samples is shown.

14 Figure 8) Isopach and pumice/lithic isopleth maps for different eruptive units of the Tufo Giallo

15 della Via Tiberina, Tufo Giallo di Prima Porta, and Grottarossa Pyroclastic Sequence eruptive

16 cycles, showing a common vent area corresponding to the Morlupo Center.

18 Figure 9) EMP glass and selected bulk compositions in the TAS diagram (a), compared to Zr/Y vs.

19 Nb/Y compositions (b), of samples from the Tufo Giallo di Prima Porta and Grottarossa Pyroclastic

20 Sequence eruptive cycles, analyzed in this work.

22 Figure 10) EMP glass and selected bulk compositions in the TAS diagram (a), compared to Zr/Y vs.

23 Nb/Y compositions (b), of samples from the Tufi Terrosi con Pomici Bianche (TTPB) eruptive

24 cycle, analyzed in this work.

25 1 Figure 11) Chrono-stratigraphic relationships of the products of the Tufi Terrosi con Pomici

2 Bianche (TTPB) eruptive cycle, from type sections described in this and previous work (see Figure

3 1 for location). The position of the dated (Table 2, 3) and analyzed (Table 4, 5, Appendix 4, 5)

4 samples is also shown.

6 Figure 12) EMP glass and selected bulk compositions in the TAS diagram (a), compared to Zr/Y vs.

7 Nb/Y compositions (b), of samples from the Tufo Rosso a Scorie Nere eruptive cycle and of the

8 following activity in the Southern Sabatini source area, analyzed in this work.

10 Figure 13) Chrono-stratigraphic relationships of the products of the Tufo Rosso a Scorie Nere

11 eruptive cycle and of the following activity in the Southern Sabatini source area, from type sections

12 described in this and previous work (see Figure 1 for location). The position of the dated (Table 2,

13 3) and analyzed (Table 4, 5, Appendix 4, 5) samples is shown.

15 Figure 14) a) Chrono-stratigraphic relationships of the products attributed to Period I of Vico

16 activity, from type sections described in this and previous work (see Figure 1 for location). The

17 position of the dated (Table 2, 3) and analyzed (Table 4, 5, Appendix 4, 5) samples is also shown;

18 b) TAS bulk compositions of pyroclastic products of the two first activity periods of the Vico

19 volcano (Perini et al., 2004; V1, V2: grey shaded areas), compared to the EMP glass and bulk

20 compositions of nine samples attributed to Vico (this work); c) Zr/Y vs. Nb/Y compositions of

21 seven samples of Vico products analyzed in this work

23 Figure 15) Synoptic overview of the chemo- and chronostratigraphic features of the MSVD.

24 a) MSVD eruptive history in the time span 800 - 300 ka For individual eruptive events emplacing

25 pumice and scoria fall deposits, the VEI is qualitatively assessed by comparison with eruptive

26 parameters of Fall A1, B1, C and D reported in Sottili et al. (2004). Volumes of pyroclastic-flow 1 deposits are qualitatively assessed based on thickness and dispersal patterns. Bulk compositions of

2 relatively unaltered samples (LOI <6.0%) are reported to integrate the Nb/Y vs Nb/Y signature, as a

3 mean for identification of distal deposits. b) Zr/Y vs Nb/Y compositions of all the MSVD and Vico

4 samples analyzed in this work compared to those from the other volcanic districts (after the critical

5 review of Marra and D'Ambrosio, 2012). c) Zr/Y vs Nb/Y compositions of the major pumice fall

6 deposits of MSVD and Vico. d) EMP glass compositions of the juvenile eruption products from the

7 Morlupo and Southern Sabatini source areas.

8 9

10 Figure 16) Cross section showing the stratigraphy of the five boreholes in which the tephra layers of

11 the Paleotiber eruptive succession were recovered (see location in Figure 1). See suppl. mat. #1 for

12 criteria of correlation and assessment of the eruption ages.

14 Figure 17) Zr/Y vs Nb/Y (a) and TAS EMP glass (b, c) compositions of two distal tephra layers

15 sampled in the lacustrine successions of the Mercure (SC3) and Sulmona (SUL1/5-3) basins,

16 providing correlation with the MSVD products.

17 Table 1

THIS WORK KARNER ET AL., 2001 DE RITA ET AL., 1993 MATTIAS & VENT ERUPTIVE ERUPTIVE UNIT VENTRIGLIA 1970 CYCLE

Top 379±40 Pyrpoclastic fall products Tufi Stratificati Varicolori di S Late Southern Sabatini Sant'Abbondio Ash-lapilli from Sacrofano and local La Storta O Succession Succession scoria cones U T Bottom 389±4 H V E CAP DSL 412±5 Bedded Pumice I R (1) (1) C Vico (4) 418±6; 412±2 416±6 ; 410±1 O N R94 -30C 427±5 S Tufo Rosso a Scorie Nere Fall F 447±7 A Eruptive Cycle Fall E 450±7 B 452±2 Tufo Rosso a Scorie Nere 452±2 Tufo Rosso a Scorie Nere 449±1(1) Tufo Rosso a Scorie Nere Piperno; Peperini listati A sabatino T Fall D I Tufi Terrosi Fall C Sottili et al. Tufi Terrosi con Pomici Bianche Pyrpoclastic fall products Tufi Stratificati Varicolori di N Eruptive Cycle Fall B 490±4 (2004) 488±2(1) from Sacrofano and local Sacrofano I 499±3 ÷ 490±4 Fall A 499±3 scoria cones Prima Porta Grottarossa Pyroclastic Sequence Grottarossa Pyroclastic Sequence Eruptive Cycle 513±3 514±5(1) 514±3 Tufo Giallo di Prima Porta Tufo Giallo di Prima Porta 514±3(1) Sacrofano lower Tufo di Castelnuovo p.p. M 517±6 pyroclasatic flow unit O Tufo Giallo della Via Tiberina Upper TGdVT 546±3 Upper TGdVT 548±4(1) Tufo Giallo della Via Tiberina R Eruptive Cycle Lower TGdVT Lower TGdVT 561±1(1) Morlupo p.f. unit L 546±3 FAD 3 546±5 Pyroclastic fall products U FAD 2 558±14 (565±3)(5) First Ash-fall Deposit (ING-02) 582±1(1) from Morlupo Edifice P Castelnuovo di Porto FAD 1 O Eruptive Cycle Tufo Giallo di Castelnuovo di Porto Tufo di Riano 589±4 589±4 Tufo di Castelnuovo p.p. (Morlupo Spatter-flow) Trachite di Morlupo (2) (2) P Santa Cecilia Eruption Unit 614±3 614±3 ; 605±11 A Vigna Murata Eruption Unit 653±4 ING-01 Bis 649±4(1) L Ponte Galeria Eruption Unit 760±6 Early airfall tuff, Ponte Galeria 758±4(1) E O Paleotiber Succession Unit D 788±13 PT-S6 783±7(3) Unit C 801±9 M Unit B 805±9 S Unit A 808±6 PT-2bS2 802±3(3)

TABLE 1 - Summary chronostratigraphy of the MSVD provided in this work and correlation to previous nomenclature. Ages performed for this work are calibrated to the Fish Canyon Tuff sanidine standard age of 28.201 Ma (Kuiper et al., 2008) and are reported with 2 uncertainty, those from previous works are at 1 and were calculated according to the following ages for the standard: (1) 27.84 Ma in Karner and Renne, 1998; (2) and (3) 28.02 Ma in Karner et al., 2001, and Florindo et al., 2007, respectively. In regular character are the ages of samples maintained to date the eruption cycles in this work after re-calculation. (4) Vico defined by Cioni et al. (1987) was dated 419±6 ka (Laurenzi and Villa, 1987), and corresponds to the Rio Ferriera Formation of Perini et al. (2004). (5) If assessed at the less conservative age estimation of 565±3 ka (see text for discussion) FAD 2 has to be considered a geochronologically distinct eruptive cycle. Table 2

Table 2. Summary of 40Ar/39Ar data # of Weighted mean Unit Sample Mineral analyses Age (ka) ± 2 MSWD Reference CAP DSL (Vico ) 06-DEO-CAP-12* biotite 10/10 398 ± 19 0.23 Marra et al., 2011 VICO 07-FC-SP-01* sanidine 10/10 418 ± 6 1.15 Marra et al., 2011 Fall B 08-ISFARNES-01* sanidine 10/10 494 ± 14 0.21 Marra et al., 2011 SAAS bottom C5 SA sanidine 12/12 389 ± 4 0.65 This Work Fall F Fall F-PP sanidine 12/12 447 ± 7 1.28 This Work Fall E Fall E-PP sanidine 12/12 450 ± 6 0.96 This Work Fall A2 CR6-B sanidine 14/14 496 ± 9 0.97 This Work FAD 3 FAD-3 sanidine 13/13 546 ± 5 0.83 This Work FAD 2 FALL-PG sanidine 12/12 558 ± 14 0.29 This Work TGCP TGCP-B sanidine 15/15 589 ± 4 1.20 This Work Ages relative to 28.201 Ma for Fish Canyon sanidine (Kuiper et al. 2008) using Min et al. (2000) decay constant. Full 40Ar/39Ar data in Appendix 1. All analyses are single crystal fusions except for samples FAD-3 and TGCP-3, which were 3 and 4 crystal fusions, respectively. Ages of samples marked * from Marra et al. (2011), originally calculated relative to the age of 28.02 Ma for Fish Canyon sanidine standard, have been re-calculated here according to the age of 28.201 Ma (Kuiper et al., 2008). LEGEND: SAAS: Sant'Abbondio Ash-lapilli Succession; TGCP: Tufo Giallo di Castelnuovo di Porto; FAD: First Ashfall Deposit. Table 3

Table 3. Summary of 40Ar/39Ar data UNIT SAMPLE LAB. NUMBER MINERAL No. OF ANALYSESAGE (ka) ±2 MSWD ORIGINAL REFERENCE RECALCULATED AGE (ka) ±2 PT A PT2b-S2 10813 sanidine 6/8 802.4 5.8 1.5 Florindo et al., 2007 807.5 5.8 rel to 28.201 Ma FC PT B I9-B 33180 + 33179 sanidine+leucite 14/15 ^803,7 10.4 0.9 Florindo et al., 2007 808.7 10.5 rel to 1.201 Ma ACS PT B I9-BL 33179 leucite 7/7 ^804.6 10.4 1.3 Florindo et al., 2007 809.3 10.5 rel to 1.201 Ma ACS PT B I9-BS 33180 sanidine 7/8 ^793.6 15.8 0.1 Florindo et al., 2007 798.3 15.9 rel to 1.201 Ma ACS PT B PTS14-A 33178 sanidine 7/8 ^795,2 10.8 1.5 Florindo et al., 2007 800.2 10.8 rel to 1.201 Ma ACS PT C I7-A 33181 sanidine 5/6 ^799,3 12.4 0.2 Florindo et al., 2007 804.3 12.5 rel to 1.201 Ma ACS PT C I9-A 33182 sanidine 7/8 ^783,7 13.4 0.2 Florindo et al., 2007 788.6 13.5 rel to 1.201 Ma ACS PT C PTS6-A 11083 sanidine 13/13 783.1 13.2 0.4 Florindo et al., 2007 788.1 13.3 rel to 28.201 Ma FC PG R93-12F 30189 sanidine 6/6 754 14 Karner and Renne, 1998 758.8 14.1 rel to 28.201 Ma FC PG R95-16A 7576 sanidine 3/15 758 8 Karner and Renne, 1998 762.8 8.1 rel to 28.201 Ma FC VM ING01 10800+10801 sanidine+leucite 6/28 649.3 3.8 0.3 Florindo et al., 2007 653.4 3.8 rel to 28.201 Ma FC SC R93-06N* 8281 sanidine 9/9 611 3 Karner and Renne, 1998 614.9 3.0 rel to 28.201 Ma FC SC R95-06A* 30181 sanidine 5/5 607 6 Karner and Renne, 1998 610.9 6.0 rel to 28.201 Ma FC FAD 0 FoMF-C1 33154 sanidine 6/6 ^591 6 0.6 Marra et al., 2009 594.8 6.1 rel to 1.201 Ma ACS FAD 0 AH20-C6 11378 sanidine 5/6 587 3 Marra et. al., 2009 590.7 3.0 rel to 28.201 Ma FC FAD 0 ING-02 10804+10805 sanidine+leucite 10/12 582 3 1.9 Florindo et al., 2007 585.7 3.0 rel to 28.201 Ma FC FAD-2 rwd R93-25A-1† 7588 sanidine 4/6 561 3 Karner and Renne, 1998 564.6 3.0 rel to 28.201 Ma FC LTGVT R93-25A-2† 7588 sanidine 2/6 545 8 Karner and Renne, 1998 548.5 8.1 rel to 28.201 Ma FC UTGVT R93-02 7589 sanidine 7/7 542 3 Karner and Renne, 1998 545.5 3.0 rel to 28.201 Ma FC UTGVT CAL03-05-06 11072+76+85 sanidine 18/20 548 10 Karner et al., 2001 551.5 10.1 rel to 28.201 Ma FC SdC SdC - ? ? 520 10 Gaeta et al., 2003 523.3 10.1 rel to 28.201 Ma FC TGPP LAB-01 11095 sanidine 4/7 514 5 Karner et al., 2001 517.3 5.0 rel to 28.201 Ma FC GRPS-a PAL-01** 11100 sanidine 5/5 516 6 Karner et al., 2001 519.3 6.0 rel to 28.201 Ma FC GRPS-b SAX-01** 11082 sanidine 5/5 508 9 Karner et al., 2001 511.2 9.1 rel to 28.201 Ma FC GRPS R93-22C 7582 sanidine 7/7 500 6 Karner and Renne, 1998 506.5 6.0 rel to 28.201 Ma FC GRPS CR1 33150 sanidine 5/5 507 4 0.7 previuosly unpublished 510.2 4.1 rel to 28.201 Ma FC FALL A1 upperCR5 33151 sanidine 8/8 496 3 1.4 previously unpublished 499.2 3.0 rel to 28.201 Ma FC FALL B R93-11M*** 7577 sanidine 9/9 487 4 3.3 Karner and Renne, 1998 490.1 4.1 rel to 28.201 Ma FC TRSN R93-26A 7583 sanidine 9/9 449 2 Karner and Renne, 1998 451.9 2.0 rel to 28.201 Ma FC rwd R94-22b 8299 sanidine 8/8 462 7 Karner and Renne, 1998 465.0 7.0 rel to 28.201 Ma FC rwd R95-04H 30175 sanidine 3/3 437 8 Karner and Renne, 1998 439.8 8.1 rel to 28.201 Ma FC VICO ? R94-30C** 8292 sanidine 7/7 422 5 Karner and Renne, 1998 427.4 5.0 rel to 28.201 Ma FC VICO SPQR-51 7108 sanidine 7/7 416 11 Karner et al., 2001 418.7 11.1 rel to 28.201 Ma FC VICO C7 10811 sanidine 8/8 410 2 Karner et al., 2001 412.3 2.0 rel to 28.201 Ma FC 40Ar/39Ar ages from previous works. The ages in the sixth column are the original mean weighted ages calculated according to 28.02 Ma for the Fish Canyon Tuff sanidine or, those marked ^, to 1.194 Ma for the Alder Creek Tuff sanidine. The number of analyses refers to the data included in the mean weighted age with respect to the total number of dated crystal for each sample. All the analyses included in this table are on single crystal. The criterion of exclusion is a 2σ cutoff, with the exception of the sample marked † for which two mean weighted ages are computed on two populations of crystals overlapping at 2σ. Mean weighted ages for samples marked * have been re-calculated in Marra and Florindo (submitted) from original datasheet in Karner and Renne (1998); those marked ** have been recalculated here from original data; full Ar/Ar data in Appendix 3. Sample marked *** was re-processed along with samples CR1 and CR5 from the same sampling site, using the same data reduction method; full Ar/Ar data in Appendix 2. LEGEND: PT: Paleotiber Succession; PG: Ponte Galeria Eruption Unit; VM: Vigna Murata Eruption Unit; SC: Santa Cecilia Eruption Unit; TGCP: Tufo Giallo di Castelnuovo di Porto; FAD: First Ashfall Deposit; LTGVT: Lower Tufo Giallo della Via Tiberina; UTGVT: Upper Tufo Giallo della Via Tiberina; SdC: Sella di Corno; TGPP: Tufo Giallo di Prima Porta; GRPS: Grottarossa Pyroclastic Sequence; TRSN: Tufo Rosso a Scorie Nere; rwd: reworked. Table 4

Table 4 Electron microprobe analyses of glasses occurring in the studied pyroclasts Unit Morlupo spatter TGCP TGCP FAD-2 FAD 3A TGPP Type WP WP GP GP WP WP Sample/ FDC1 upper MG8- FDC1 middle Fall PG FAD2 MG12 Cava Vicoli locality Lct-bearing glass

(6)a (7) (8) (3) (3) (6)

SiO2 53.43 1.16 53.53 1.00 52.39 1.26 56.23 0.80 53.64 1.08 53.61 0.65 TiO2 0.26 0.02 0.52 0.05 0.80 0.12 0.47 0.05 0.24 0.03 0.38 0.05 Al2O3 20.03 0.38 18.97 0.41 17.63 0.93 18.57 0.30 20.52 0.75 19.20 0.16 FeO 2.21 0.11 3.88 0.31 5.63 0.99 2.91 0.09 2.10 0.28 2.62 0.09 MnO 0.22 0.04 0.25 0.07 0.27 0.05 0.16 0.01 0.19 0.11 0.19 0.05 MgO 0.18 0.02 0.59 0.08 1.53 0.66 0.44 0.04 0.18 0.04 0.23 0.02 CaO 3.03 0.23 5.73 0.71 8.43 1.44 2.81 0.10 3.16 0.65 3.44 0.09

Na2O 4.82 0.14 5.32 0.31 4.67 0.35 3.00 0.18 6.65 0.91 3.80 0.15 K2O 9.29 0.20 5.68 0.58 3.75 0.34 10.07 0.22 4.85 1.50 9.85 0.33 P2O5 0.03 0.02 0.17 0.27 0.20 0.05 0.05 0.03 0.04 0.01 0.03 0.02 SO2 0.15 0.05 0.35 0.09 0.28 0.06 0.00 0.00 0.18 0.08 0.21 0.03 F 0.63 0.09 0.61 0.09 0.60 0.12 0.00 0.00 0.78 0.36 0.38 0.08 Cl 0.17 0.19 0.11 0.02 0.10 0.04 0.10 0.04 0.10 0.02 0.09 0.01 Total 94.46 95.71 96.27 94.82 92.63 94.02 WP: white pumice; GP: grey pumice; Lct: leucite; a: number of point analyses used in the average and standard deviation (). Table 4 (continued) Unit GRPS-d FALL A FALL A FALL B1 Fall C Fall D MI in Type MI in BS Cpx WP WP WP Cpx of MI in Cpx of WP BS Sample Mg13 Fall a GR Fall a VT Fall b SPX33 a (5) (5) (6) (4) (2) (3)

SiO2 46.47 1.64 55.75 0.73 56.23 0.33 55.05 0.88 49.11 57.46 0.90

TiO2 0.67 0.11 0.48 0.02 0.46 0.02 0.44 0.01 1.18 0.62 0.13

Al2O3 17.98 0.39 17.89 0.21 18.02 0.07 17.44 0.29 17.39 18.76 0.84 FeO 6.48 1.17 2.88 0.08 3.03 0.12 2.65 0.06 7.72 3.29 0.46 MnO 0.14 0.07 0.15 0.03 0.17 0.13 0.14 0.02 0.38 0.21 0.03 MgO 1.90 0.98 0.47 0.02 0.49 0.06 0.46 0.04 0.63 0.22 0.12 CaO 7.88 0.59 3.16 0.24 2.84 0.08 3.01 0.17 8.79 3.20 1.08

Na2O 1.78 0.37 2.96 0.13 2.76 0.14 2.89 0.18 3.25 2.35 1.39

K2O 9.77 1.17 9.52 0.14 9.55 0.25 9.49 0.23 7.12 10.34 0.77

P2O5 1.10 0.11 0.09 0.04 0.07 0.01 0.05 0.01 0.06 0.23 0.25

SO2 0.74 0.30 0.29 0.40 0.19 0.04 0.16 0.02 0.30 0.27 0.09 F 0.31 0.09 0.31 0.11 0.33 0.08 0.24 0.11 0.48 0.21 0.27 Cl 0.07 0.03 0.12 0.03 0.10 0.02 0.12 0.03 0.10 0.05 0.04 Total 95.28 94.06 94.22 92.14 96.51 97.22 WP: white pumice; MI: melt inclusion; Cpx: clinopyroxene; a: number of point analyses used in the average and in the standard deviation ().

Table 4 (continued) TRSN TRSN Unit Fall E Fall E Fall E Fall F (basal fallout) (piroclastic flow) Type WP BP MI in Cpx WP WP MI in Cpx of GS Sample/ Isola Farnese SPX35 Prima Porta S. Abbondio SPX37 locality

a (18) (25) (3) (11) (4) (4)

SiO2 56.18 1.21 59.30 0.95 56.37 0.57 57.49 0.53 56.58 0.77 47.43 0.30

TiO2 0.49 0.04 0.50 0.03 0.49 0.05 0.49 0.08 0.35 0.13 0.73 0.03

Al2O3 17.89 0.17 18.21 0.28 17.79 0.06 18.27 0.41 19.34 0.62 17.66 0.02 FeO 2.74 0.10 2.57 0.13 2.86 0.24 2.50 0.16 2.30 0.15 6.83 0.14 MnO 0.14 0.03 0.16 0.04 0.14 0.01 0.12 0.03 0.20 0.05 0.14 0.01 MgO 0.38 0.02 0.37 0.03 0.47 0.13 0.35 0.07 0.26 0.04 3.79 0.08 CaO 2.63 0.11 2.57 0.28 2.66 0.14 2.52 0.11 2.40 0.23 8.07 0.24

Na2O 3.52 0.09 3.34 0.45 2.49 0.15 3.43 0.21 5.24 0.33 2.03 0.08

K2O 9.56 0.10 9.77 0.66 9.70 0.32 9.57 0.39 8.59 0.12 8.37 0.14

P2O5 0.05 0.03 0.05 0.03 0.04 0.04 0.05 0.03 0.01 0.02 0.50 0.02

SO2 0.00 0.00 0.14 0.06 0.27 0.01 0.07 0.07 0.00 0.00 0.66 0.02 F 0.33 0.10 0.21 0.15 0.32 0.13 0.14 0.17 0.00 0.00 0.30 0.09 Cl 0.08 0.01 0.07 0.02 0.06 0.01 0.09 0.02 0.15 0.04 0.06 0.02 Total 93.58 96.84 93.66 95.09 95.42 96.57 WP: white pumice; BP: black pumice; MI: melt inclusion; Cpx: clinopyroxene; GS: grey scoria; a: number of point analyses used in the average and in the standard deviation ().

Table ? (continued) Unit Vico Vico Vico Vico Type WP WP WP WP Sample/ locality II Fall S. Abbondio San Martino San Martino III Fall S. Abbondio a (4) (4) (4) (4)

SiO2 69.27 0.84 68.01 0.40 54.25 0.19 55.63 1.21

TiO2 0.22 0.09 0.22 0.07 0.51 0.14 0.53 0.08

Al2O3 14.37 0.34 14.28 0.35 19.77 0.20 19.36 0.89 FeO 1.27 0.11 1.23 0.12 3.32 0.11 3.24 0.28 MnO 0.06 0.08 0.10 0.03 0.09 0.06 0.20 0.09 MgO 0.08 0.04 0.10 0.01 0.31 0.06 0.30 0.07 CaO 1.20 0.10 1.17 0.05 4.15 0.37 4.17 0.51

Na2O 3.35 0.23 3.29 0.18 4.37 0.38 5.38 0.46

K2O 6.73 0.15 6.71 0.30 8.91 0.70 7.23 0.46

P2O5 0.00 0.01 0.02 0.02 0.03 0.05 0.04 0.02

SO2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 F 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Cl 0.14 0.01 0.15 0.02 0.09 0.02 0.08 0.03 Total 96.70 95.28 95.80 96.16 WP: white pumice; GP: grey pumice; a: number of point analyses used in the average and in the standard deviation ().

Table 5

Table 5 - XRF analyses of juvenile clasts Morlupo GRPS FAD-1 FAD-1 unit GRPS spatter breccia upper lower

location Morlupo Morlupo Capena Capena breccia

sample MOR 01 MOR 11-DS MG-27GP MG-26GP GRPS-DS SiO2 61.12 48.63 57.87 58.94 49.23 TiO2 0.19 1.01 0.59 0.54 0.92 Al2O3 20.29 16.57 21.90 20.60 16.25 FeOtot 4.16 9.48 4.73 4.30 9.49 MgO 0.13 0.16 0.26 0.27 0.26 MnO 0.15 4.74 0.76 0.60 5.26 CaO 2.46 10.61 4.30 3.67 11.32 Na2O 3.81 0.61 4.79 5.81 4.69 K2O 7.70 7.80 4.64 5.13 1.83 P2O5 0.06 0.60 0.16 0.13 0.75 Total 100.00 100.00 100.00 100.00 100.00

LOI/EMP total 1.54 2.27 6.01 5.03 3.72 Table 6

TABLE 6 - Combined 40Ar/39Ar ages

1 UNIT SAMPLE LAB. NUMBER MINERAL NUMBER OF MEAN WEIGHTED Error ORIGINAL ANALYSES AGE (ka) (±2) REFERENCE Paleotiber succession I-9B+ 33180+33179 leucite+ 21/22 799.7 8.9 Florindo et al., 2007 Unit B PTS14-A +33178 sanidine Paleotiber succession I9-A+ I7-A 33182+33181 sanidine 12/14 801.4 9.4 Florindo et al., 2007 Unit C Ponte Galeria Eruption R93-12F+ 30189+ sanidine 9/21 760.0 6.2 Karner and Renne, Unit R95-16A 7576 1998 Santa Cecilia Eruption R95-06N + 30182+ sanidine 16/16 614.2 2.7 Karner and Renne, Unit R93-06A 8281 1998 Grottarossa SAX-01+PAL-01+ 11082+11100 sanidine 18/23 512.5 3.1 Karner et al., 2001a Pyroclastic Sequence CR1 +33150

(GRPS) 2 ERUPTIVE CYCLE SAMPLE AGES MEAN WEIGHTED Error AGE (ka) (±2) Prima Porta Eruptive SAX-01+PAL-01+ 511±9; 519±6; 510±4; 517±6 513.5 2.8 This work Cycle (TGPP+GRPS) CR1+LAB01 Best eruption ages derived from the joined re-calculation of crystal ages from samples attributed to the same eruptive unit (1), or by combined weighted mean age of samples of the same eruptive cycle (2). All ages are calculated according to 28.201 Ma for the Fish Canyon Tuff sanidine.

*Figure 1

N Vico Bracciano LakeITALY

Civita Castellana Volcanic District San Martino Treja River

Calcata Via San Abbondio

Apennines

Morlupo Center Monti Sabatini Capena Morlupo Bracciano Castelnuovo di Porto Center Sacrofano Center Cas. Francalancia Via Tiberina, km 13 Volcanic District Southern Sabatini Center

Prima Porta Casale del Gallo Isola Farnese GRA/A1 Grottarossa

Acquatraversa PTS14 Tenuta di Capannacce PTS6 I7 PaleotiberVia Tiburtina, km 9.7 PT2b I9 Graben ROME Capitoline Hill a) Casale Basini b) Malagrotta Santa Cecilia Via d. Pisana c) Cava Rinaldi ING01 Cave Ponte Galeria er d) iv R Colli Albani

Malafede

e T i b Trigoria Volcanic District Tyrrhenian Sea 10 km

Figure 1 *Figure 2 ERUPTION CYCLE MONTI SABATINI VOLCANIC DISTRICT TEPHRA INTERBEDDED WITHIN PYROCLASTIC SUCCESSION FLUVIO-LACUSTRINE DEPOSITS

Magliano Romano Plinian Fall (1) SAB-01 310±2

C4 SA 379±40 Late Southern Sabatini Succession 390±4 ÷ 379±40 Sant’Abbondio Ash-Lapilli Succession (Barberi et al, 1994) C5 SA 389±4 San Paolo Formation (MIS 11)

INITABAS NREHTUOS INITABAS Vico β 403 ±6 (2) TDC DSL (4) C7 412±5 Vico α 419 ±6 412±2 (3) Vico Fall F FALL F-PP 447±7 418±9 SPQR-51 α (3) 427±5 R94-30C 418±6 (2) FC-SP-01 Tufo Rosso a Scorie Nere Fall E FALL E-PP 450±7

RETNEC Eruptive Cycle (3) Laminated ash-flow 440±8 R95-04H 452±2 (3) 465±7 R94-22b Tufo Rosso a Scorie Nere sabatino R93-26A 452±2(4) Fall D Valle Giulia Formation (MIS 13) Tufi Terrosi Fall C ISFARNESE-01 (3) Eruptive Cycle Fall B 494±14(2) 490±4* R93-11M 499±3 ÷ 490±4 496±9 CR6B Fall A2 upper Fall A 499±3 CR5 Fall A2 unit e holocrystyalline lithic breccia unit d unit c Grottarossa Prima Porta (4) unit b SAX-01 511 9* CR1 Eruptive Cycle unit b’-b” Pyroclastic ± 510±4 514±3 unit a Sequence PAL-01 519±6*(4) LAB-01 517±6(4) Tufo Giallo di Prima Porta

RETNEC OPULROM fallout (5) unit d 523±10 Sella di Corno pumice fall unit c unit b Upper Tufo Giallo della Via Tiberina (4) (3) Tufo Giallo della Via Tiberina unit a CAL-03+CAL-05+CAL-06 552±10 546±3 R93-02 Eruptive Cycle Lower Tufo Giallo della Via Tiberina 546±5 R93-25A-1 549±16**(3) First Ashfall Deposits-3B First Ashfall Deposits-3A FAD-2 546±5

FAD-2 565±3 (R93-25A-2) First Ashfall Deposits-2 558±14 FALL PG

Tufo Giallo di Castelnuovo First Ashfall Deposits-1 di Porto Eruptive Cycle First Ashfall Deposits-0 (6) 589±4 CAVE-C6 591±3(7) ING 02 586±3 TGCPa 589 4 ± FoMF-C1 (8) Morlupo spatter flow 592±8^ 587±9 (Barberi et al., 1994) Tufo Giallo di Castelnuovo di Porto Santa Cecilia Formation/Paleotiber 4 (MIS 15) 611 6**(3) R95-06A Santa Cecilia Eruption Unit Pliocene Sedimentary Substrate ± 615±3**(3) R93-06 614±3 40 39 (6)

Ar/ Ar dating (ages in ka±2σ ) 653±4 ING01-P1 Vigna Murata Eruption Unit YT I V I TCA OELA P New 40Ar/39Ar datings performed at Rare Gas Laboratory, 653±4 University of Madison, Wisconsin. Ages relative to 28.201 Paleotiber 3A (MIS 18.3) Ma for the Fish Canyon sanidine (Kuiper et al., 2008), using 763±8(3) R95-16A Ponte Galeria E. U. 760±6 Min et al., 2000, decay constant. Full 40Ar/39Ar data in Appendix 1. Paleotiber 2 (MIS 19) Previously unpublished 40Ar/39Ar datings, full data in Appendix 2. Paleotiber Succession: 40Ar/39Ar datings from previous literature: (1) Sottili et al., 2011; 788±13(6) PT-S6 Unit D 788±13 (2) Marra et al., 2011; (3) Karner and Renne, 1998; (4) Karner et al., 799±12^(6) I9-A 2001; (5) Gaeta et al., 2003; (6) Florindo et al., 2007; (7) Marra et al., 2009: (6) 804±12^ I7-A Unit C 801±9 (8) Marra and Florindo (2013). (6) All the ages are re-calculated here from the published mean weighted ages according 809±10^ I9-B Unit B 805±7 to the age of 28.201 Ma for the Fish Canyon Tuff sanidine (Kuiper et al., 2008), or 800±11^(6) PTS14-A (those marked ^) according to the age of 1.201 Ma for the Alder Creek Tuff sanidine, (6) except: * Mean weighted ages re-calculated in this work from unpublished laboratory 808±6 PT-2bS2 Unit A 808±6 run, and ** Mean weighted ages re-calculated in this work from original datasheet provided as GSA Data Repository item 9845 by Karner and Renne, 1998; full 40Ar/39Ar data included in Appendix 3.

. Figure 2 *Figure 3

1 24 PT-Unit A a) MS-A’ b) 22 MS-A’ 20 MS-B 20 18 18 VM-Unit 16 8 5 16 CAMPANIA PT-Unit C 6 PT-Unit D 4 14 14 3

40 39 12 PN (Zr/Y) PG-Unit 7 PT-Unit B SAMPLE Ar/ Ar Age 12 (ka ±2 σ) 2 1) PT2b-S2 808±6 Paleotiber succession Unit A (808±6 ka) 2) I9-B 809±10 10 VULSINI A Paleotiber succession Unit B (805±7 ka) 10 3) PTS14-A 800±11 VS 4) I7-A 804±12 PR Paleotiber succession Unit C (801±9 ka) 5) I9-A 799±12 9 VULSINI B Paleotiber succession Unit D (788±13 ka) 8 8 6) PT-S6 788±13 7) R95-16A 763±8 Ponte Galeria Eruption Unit (760±6 ka) SC-Unit VICO 8) ING01-P1 653±4 Vigna Murata Eruption Unit (653±4 ka) 10 Samples of the Monti Sabatini Volcanic District 6 9) R93-06N 615±3 (Zr/Y) Santa Cecilia Eruption Unit (614±3 ka) 10) R95-06A 611±6

(Nb/Y) (Nb/Y) 0.5 1.0 1.5 0.5 1.0 1.5 2.0

Figure 3 *Figure 4

Vico β 17 Vico α a) TRSN Fall E TRSN Fall F Phonolite TRSN Flow TRSN Fall D TTPB Fall C Foidite TTPB Fall B 13 Tephri- TTPB Fall A phonolite GRPS

wt%) Rhyolite TGPP ( TGVT UPPER O 2 TGVT LOWER Trachyte FAD 3

O+K FAD 2 2 Phono-tephrite TGCP Lct-bearing BS Na 9 TGCP WP MORLUPO SPATTER Latite

Shoshonite

5 45 50 55 60 65 70 75

SiO2 (wt%)

MORLUPO CENTER 589-517 ka SOUTHERN SABATINI CENTER 499-389 ka PRIMA PORTA ERUPTIVE CYCLE 517±6 ka SAA SUCCESSION 390±4 - 370±40 ka San Abbondio top dark grey scoria layer GRPS (A) and TGPP (B) grey scoria TGPP white pumice TRSN ERUPTIVE CYCLE 452±2 ka FALL F grey scoria TGVT ERUPTIVE CYCLE 546±5 ka FALL E white pumice grey scoria TRaSN black pumice white pumice Fall D white pumice FAD 3B grey scoria 546±5 ka FAD 3A white pumice 546±5 ka FAD 2 white pumice 558±14 ka TT ERUPTIVE CYCLE 499±6 ka Fall C grey scoria TGCP ERUPTIVE CYCLE 589±4 ka FAD 1 grey pumice Fall B grey scoria TGCP grey pumice Fall B white pumice TGCP white pumice Fall A white pumice spatter flow white pumice in the spatter flow

EMP analysis on matrix glass or melt 24 inclusion in clinopyroxene c) 16 a’ b) 22 MS-B PHONOLITE MS-A1 14 20 MS-A

FOIDITE TEPHRI a MS-A1 PHONOLITE 18 12 MS-A TRACHYTE MS-A2 16 a 22 MS-A2 Na O+K O 10 MS-B LATITE 14 PHONO TEPHRITE

8 (Zr/Y) SHOSHONITE 10

50 55 60 0.5 (Nb/Y) 1.0 1.5 SiO2 Figure 4 *Figure 5a

SAMPLES FOR GEOCHEMICAL ANALYSES SAMPLES FOR 40 Ar/ 39 Ar DATING (large symbols: EMP glass analyses; (ages in ka ± 2σ) small symbols: bulk XRF and FUS-ICP-MS analyses Massive to laminated, fne-grained Accretionary lapilli for trace and major elements) 589±4 pyroclastic-fow deposit

Ash-lapilli fall deposit Deep paleosol TGVT ERUPTIVE CYCLE (546±5 ka) TGCP ERUPTIVE CYCLE (589±4 ka) upper TGdVT grey scoria FAD 1 upper grey pumice upper TGdVT white pumice Dark grey lapilli fall deposit FAD 1 lower grey pumice Faintly pedogenized ash lower TGdVT grey scoria TGCP grey pumice (upper) lower TGdVT white pumice Dark grey scoria fall deposit Partially reworked, altered TGCP white pumice (lower) ash deposit FAD 3b grey scoria Morlupo Trachytic spatter flow FAD 3a white pumice Pumice within the spatter-flow deposit Grey pumice fall deposit Lacustrine white mud FAD 2 white pumice (558±14 ka) White pumice fall deposit Morlupo spatter-fow deposit

VIA TIBERINA, km 13 (Karner et al., 2001)

MG-11C Via Cas. Francalancia unit d MG-11; MG-11/2 MG-10/2; UTGVT-c unit c a) MG-10; MG-10/2 CAPENA+MORLUPO unit b MG-2 546±3

COMBINED TYPE SECTION SCALE TO NOT unit a UTGVT R93-02 MG-1 MORLUPO - CASTELNUOVO DI PORTO 4 TYPE SECTIONS MG-30 MG-7 LTGVT LTGVT MG-29; LTGWP-CAL MG-29

LTGVT 2 3 FAD-3B FAD 13B; FAD-3 DS FAD-3B FAD 3-CP; FAD 3-CM; FAD-3 FAD 13B 2 FAD 2-CP FAD-3A 546±5 FAD-3 PONTE GALERIA (Via d. Pisana) 1 2 FAD-1 MG27 1 TGCP FAD-2 FALL-PG PG TGCP-A ds FAD-1 m FAD km 13 FAD 13 WP 558±14 FAD-2 Fall PG SP Fm MG26 FALL-PG wp FdC1 upper 1 Spatter FdC1 middle TGCP-B wp 589±4 TGCP-B m 587±9 TGCP-WP MOR 01 Laurenzi and Villa, 1987 TGCP NOT TO SCALE TO NOT MG-8 a) m

FAD-0 ? Figure 5a *Figure 5b 4 LTGVT c

3 b a FAD 3A FAD 3B 2 FAD 1

1 TGCP

FAD 3A FAD 1 m

MORLUPO TYPE TGCP SECTION

LTGVT 3 FAD 3B LTGVT FAD 3B FAD 3A 2 FAD 3A FAD 1 upper 1 FAD 1 TGCP FAD 1 lower

m CAPENA TYPE SECTION

Figure 5b *Figure 6

MG-8

TGVT ERUPTIVE CYCLE (546±5 ka) TGCP ERUPTIVE CYCLE (589±4 ka) upper TGdVT grey scoria FAD 1 grey pumice upper TGdVT white pumice TGCP grey pumice

lower TGdVT grey scoria TGCP white pumice lower TGdVT white pumice Morlupo spatter flow

FAD 3b grey scoria Pumice at the base of the spatter-flow deposit FAD 3a white pumice TRIG pisolitic ashfall FAD 0 ING-02 white pumice FAD 2 white pumice (565±3 ka) FAD 0 Cave-C6 white pumice 16 EMP analysis on matrix glass FAD 0 FoMF-C1 white pumice

small symbol: bulk XRF with LOI< 6% (Zr/Y) FAD 3A MG-8 20 MS-A PHONOLITE 14 Fall PG 18 FAD 2 Fall PG Fall PG

FOIDITE FAD 13 FAD 13

FAD 3A TEPHRI TRACHYTE UTGVT PHONOLITE 16 MS-B 12 BR53

BR53 LTGVT

MOR 01

22 14 TGCP Na O + K MOR 01 10 PHONO FAD 0 LATITE TEPHRITE 12

8 10 SHOSHONITE FUS-ICP-MS analysis smaller symbol: XRF analysis a) b)

50 55 60 65 0.5 (Nb/Y) 1.0 1.5 SiO2 Figure 6 *Figure 7

SAMPLES FOR GEOCHEMICAL ANALYSES (FUS-ICP-MS analyses for trace elements)

TRIG pisolitic ashfall Massive to laminated, fne-grained Accretionary lapilli FAD 0 ING-02 white pumice pyroclastic-fow deposit FAD 0 Cave-C6 white pumice Ash-lapilli fall deposit Deep paleosol FAD 0 FoMF-C1 grey pumice

Dark grey lapilli fall deposit Faintly pedogenized ash SAMPLES FOR 40 Ar/ 39 Ar DATING (ages in ka ± 2σ) Dark grey scoria fall deposit Fluvial-lacustrine clay 589±4 *ages re-calculated from Marra et al., 2009 Grey pumice fall deposit Partially reworked, altered ash deposit White pumice fall deposit CAPENA+MORLUPO COMBINED TYPE SECTION

LTGVT

FAD-3B

FAD-3 GRA/A1 INGV Borehole Malafede Trigoria Cave FAD-3A 546±5 (Karner et al., 2001) (Karner et al., 2001) (Marra et al., 2009) (Karner et al., 2001) (Marra et al., 2009)

TPT TPT TPT TPT FAD-1 LTGVT 565±3* TPT MORLUPO 589±4 CAVE-C6 591±3 FAD-0 TGCP-B TGCP FAD-0 612±2* TFC ING-02 586±3 FAD-0 FAD-0 FoMF-C1 595±6 FAD-0 ?

Figure 7 *Figure 8

TGPP basal fall Faleria UTGVT pyroclastic fow a) lithic clasts; pumice clasts (cm) b) 2.3; 1.6 Rignano Flaminio

3.8; 1.4

4.4; 2.1

6.4; 3.0

Morlupo

Via Casale Francalancia Sacrofano 10.3; 3.9 Caldera 4,0; 2,5

Sacrofano

lithic clasts; pumice clasts (cm)

b’) TGPP basal fall Tiber river N 56

1.9; 1.1

Outcrops of UTGVT

MSVD volcanic deposits c) GRPS-e lithic breccia

Figure 8 *Figure 9

larger symbol: EMP analysis on matrix glass or melt Tufo Giallo di Prima Porta - a) 16 inclusion in clinopyroxene; Grottarossa Pyroclastic sequence 514±3 ka small symbols: bulk XRF analysis with LOI<3.5%, GRPS lithic breccia dark scoria except when indicated

TGPP-wp TGPP dark scoria TGPP basal white pumice fall 14 PHONOLITE

FOIDITE

TEPHRI 12 PHONOLITE TRACHYTE

22 18 c) MS-A1 Na O+K O MS-B (Zr/Y) 10 PHONO 16 TEPHRITE LATITE MS-A2 TGPP-ds 14 LOI: 8.98 8 B A GRPS-ds 12 A SHOSHONITE 6 10 50 55 60 SiO2 (Nb/Y) 0.5 1.0 1.5

Figure 9 *Figure 10

TTPB ERUPTIVE CYCLE 499±3 - 490±4 ka 30 upper Fall C1 grey scoria 1 Fall B2 grey scoria Fall B1 white pumice 494±14 ka; 490±4 ka Fall A2 grey scoria 496±9 ka 28 upper Fall A1/A2 white pumice 499±3 ka lower Fall A1 white pumice

Sella di Corno bulk sample 523±10 ka 26

FUS-ICP-MS and XRF bulk analyses 24 (LOI >5% <8%, except when indicated) large symbol: EMP analyses on matrix glass 14 PHONOLITE 22 GR FALL C1

VT IF 20 2 12 TEPHRI FALL B2 PHONOLITE FALL A MS-A

TRACHYTE CG9 CR4 VT LOI: 8.75 18 FALL B1 MS-B upper FALL A1/A2 3 3 CG 5 CG 1-3 LATITE CG 5 CR4 CG 3 10 1 CG9 2 1 CG 2 PHONO CR6B LOI: 11.28 16 TEPHRITE CR5 FALL B1 3 lower FALL A1

22 CR7 CG 1 1 CR5 VT Na O+K O LOI: 3.27 2 FALL B2 LOI: 8.71 14 GR 8 IF 2 CR6B SHOSHONITE GR LOI: 11.39 CR7 FALL C1 12 upper A2

6 TRACHY BASALT 10 3 a) b) (Zr/Y) 50 55 SiO2 60 65 0.5 (Nb/Y) 1.0 1.5

Figure 10 *Figure 11

ISOLA FARNESE CAVA RINALDI PONTE GALERIA GROTTAROSSA VIA TIBUTINA, km 9.7 (Sottili et al., 2004) (This work) (Casale Basini) (Karner et al., 2001) (Marra et al., 2011) (Karner & Renne, 1998) CASALE DEL GALLO (Sottili et al., 2004) TRSN 452±2 FALL D

3 2 FALL C upper C1 1 CR7 upper A2 496±9 CR6B B4 TRSN 452±2 FALL B PR 459±4* B3 B2 R93-11M 1 2 494±14 B1 490±4 08-ISFARNESE-01 TP 532±2* FALL A CG9 GR VT FALL A 499±3 CR5 Fall A2 A2 lower A1 TPT 565±2* upper A1 GRPS CR4 CG5 upper A1

TGPP holocrystalline lithics layer

510±4 CR1 d CG1-3 lower A1 lower c

SAX-01 511±9 b 1m b” b’ GRPS TGPP a Tree holes 0 Accretionary lapilli 517±5 LAB-01

Deep paleosol TGPP pyroclastic-fow deposit Faintly pedogenized ash Dark grey and light grey lapilli fall deposit Partially reworked, altered ash deposit

Dark grey lapilli fall deposit Lacustrine white mud

Dark grey scoria fall deposit Eolian sand Lagoon clay White pumice fall deposit Gravel and sand Figure 11 *Figure 12

bulk samples (LOI <6%, except when indicated) large symbol: EMP on matrix glass or melt inclusion in clionopyroxene FAD-3A

16 20 MS-A MS-B

PHONOLITE 18 TGPP 14 TGCP UTGVT FAD-2 TGVT FAD-2 FOIDITE TGPP 16 12 TEPHRI PHONOLITE TGCP PP TRACHYTE PP LTGVT 14

10 PHONO TEPHRITE LATITE (Zr/Y) 22 8 7.23 Na O+K O SHOSHONITE 10 b)

0.5 (Nb/Y) 1.0 1.5 6 6.04

8.69 LATE SOUTHERN SABATINI SUCCESSION 4 SAAS C4 379±40 ka SAAS C5 389±4 ka 7.15 VICO PERIOD I TDC dark scoria layer 412±5 ka 2 a) Ponte Galeria grey lapilli R94-30C 427±5 ka 12.76 TRSN ERUPTIVE CYCLE 452±2 ka 50 55 SiO2 60 65 FALL F grey scoria 447±7 ka

FALL E white pumice 450±7 ka

TRSN black pumice 452±2 ka Fall D white pumice

Figure 12 *Figure 13 11 PRIMA PORTA TYPE SECTION VIA SAN ABBONDIO TYPE SECTION PN Magliano Romano plinian pumice fall 310±2 ka 10 (Sottili et al., 2010) FALL F

9 12 FALL E

TRSN 8 SAAS C4 379±40 11

6 PRIMA PORTA Tenuta di Capannacce 7 SAAS C5 389±4 TYPE SECTION (Marra et al., 2011)

5 PN 409±2* PN 409±2*

4 VICO β 403±6 Scoriaceous VICO α 419±6 DSL 412±5 Ash-lapilli fall deposit

Dark grey scoria fall deposit 3 Fall F 447±7 Grey pumice fall deposit

White pumice fall deposit Partially reworked, altered Fall E ash deposit 2 Laminated, matrix supported pyroclastic deposit Fall E 450±7 deposit 1 Deep paleosol PR 459±4*

Faintly pedogenized ash TRSN 452±2 TRSN 452±2 m Figure 13 *Figure 14 PONTE GALERIA ROME TENUTA DI CAPANNACCE

SANTA CECILIA

412±2 C7 TDC-DSL 412±5 65 m a.sl.. 60 m a.sl.. CAPITOLINE HILL TRSN ? FC-SP-01 SPQR-51 PR ? 418±6 418±9 30 m a.sl.. MALAGROTTA

25 m a.sl.. 427±5 R94-30C a) PR 459±4*

VICO Period I (419±6 - 403±6 ka)

Vico β grey pumice 403±6 ka

TDC dark scoria layer 412±5 ka Vico α white pumice 419±6 ka

San Paolo Fm Ponte Galeria white pumice C7 413±2 ka (=Vico α) San Paolo Fm Capitoline Hill white pumice 418±6 ka (=Vico α) San Paolo Fm Ponte Galeria dark lapilli R94-30C 427±5 ka 16 bulk samples (LOI <6%, except when indicated) small symbol: glass

22 PHONOLITE 14 FOIDITE 20 MS-A’ SA V2 TEPHRI 18 12 PHONOLITE

RHYOLITE LOI 6.17 16 TRACHYTE V1a

10 PHONO V1b SA TEPHRITE C7 14 MS-B V1b

22 LATITE LOI 7.23 Na O+K O 8 V1a C7 SHOSHONITE 10

TRACHYBASALT (Zr/Y)

4 6

LOI 7.15 b) c) 50 55 60 65 70 0.5 (Nb/Y) 1.0 1.5 SiO2

Figure 14 *Figure 15 MSVD a) Southern Sabatini MSVD Bracciano MSVD - Paleo-activity MSVD - Morlupo VICO 5 Period I FALL A1 FALL FALL B1 FALL FALL D FALL β 4 α FALL C FALL MRPF TRSN VICO VICO FAD 1 FAD VICO VICO Fallout deposit Fallout 10 2 FAD 3 E FALL FAD 3A FAD TdB TGPP PG FALL B2 FALL PT-c PT-d FALL F FALL FALL A2 FALL 3

2 PT-a GRPS TGVT TGCP SC VM TDC-DSL 1 R94-30C SAAS 1 0 FAD PT-b SdC VOLUME (km ) VOLUME VEI FAD 3B FAD 0.1 Mo SF 800 700 600 500 400 300 Age (ka) TAS bulk compositon: MONTI SABATINI VOLCANIC DISTRICT trachyte TAS glass compositon phonolite MOR-PU Paleo-activity (808-614 ka) latite 16 Morlupo and Southern Sabatini (589-447 ka) phonotephrite d) VICO Period I (419-403 ka) trachybasalt Mo-WP undetermined (LOI > 6.0)

PT-a TGPP FALL E PHONOLITE 14 FALL D

(Zr/Y) TRSN

20 FOIDITE FALL B1

(Zr/Y) FAD 2 FALL A1

20 FAD 3A TEPHRI FAD 3A 18 VULSINI FALL D TGVT 12 PHONOLITE TRACHYTE FALL A1 upper FAD 3B 16 18 FAD 2 FALL C FALL F FALL B1

14 TGPP FALL A1 lower 22 GRPS-e 16 LATITE Na O+K O 10 12 VICO β PHONO Morlupo TEPHRITE white pumice 14 TGCP/FAD 1 dark scoria 10 FAD 0 Southern Sabatini C O L L I A L B ACAMPANIA N I 12 white pumice 8 VICO α 8 SHOSHONITE black pumice 10 dark scoria 6 FALL F c) 50 55 60 4 b) SiO2 0.5 (Nb/Y) 1.0 1.5 0.5 1.0 1.5 (Nb/Y) Figure 15 *Figure 16 Paleotiber Succession ERUPTION AGE SAMPLE 40 Ar/ 39 Ar Age 1 24 PT-Unit A (ka ±2σ) 788±13 Unit d 6) PTS6-A 783±13 22 MS-A’ 5) I9-A 799±12 801±9 Unit c 4) I7-A 804±12 20 3) PTS14-A 800±11 805±7 Unit b 2) I9-B 809±10

18 808±6 Unit a 1) PT2b-S2 808±6 PTS14

5 16 PT-Unit C/D 6 Pyroclastic-fow deposits of 4

the paroxismal Colli Albani activity 14 3

PT-Unit B (Zr/Y) 12

2 30 10 a) (Nb/Y) 1.0 1.5 I9 565±2 PTS2 800±11 PTS14-A 565±2 I7

20 20

PTS6

799±12 I9-A 10 10 804±12 I7-A

809±10 I9-B 788±13 PTS6-A

808±6 PT2b-S2 m a.s.l. m a.s.l.

0 0 HORIZONTAL NOT TO SCALE

Sedimentary deposits Volcanic deposits (ages in ka)

Sandy silt scoria- and lapilli-fall deposit Sand and Clay with carbonatic concretions Peat layers pumice-fall deposit Clay Sand distal pyroclastic-fow deposit Fine gravel/Coarse sand b) Coarse gravel

Figure 16 *Figure 17 (Zr/Y)

20 FAD 3A

FALL D FALL A1 upper 18 FAD 2 FALL C

FALL B1 VULSINI TGPP 16 SdC SC3 SUL1/5-3

14 TGCP/FAD 1 FALL A1 lower

FAD 0 12

CAMPANIA 10 FALL F a)

0.5 (Nb/Y) 1.0 1.5

16 SUL51c 1.6 SabatiniFallA(499ka) 15 b) c) MercureSC3 1.4 16 14 TGPP (517 ka) Phonolite 1.2 15 SUL1/5-3 13 1.0 Phonolite 14

(wt%) 12 (wt.%)

O 0.8 2 13 11 TrachyteTrachite MgO O+K 2

0.6 (wt%) O 2

Na 12 10 0.4 O+K Trachyte Latite 2

Na 11 9 0.2

8 0.0 10 53 54 55 56 57 58 59 60 61 62 5650 51 57 52 53 58 54 55 59 56 57 60 58 59 61 60 61 62 62 SiO2 (wt%) 4.5 SiO2 (wt%) 5.5 11.0 b’) c’) 5.0 10.54.0

4.5 3.5 10.0 Figure 17 4.0 9.53.0 (wt.%) (wt.%)

3.5 (wt%) FeO O CaO 2

K 9.02.5 3.0

8.5 2.5 2.0

8.0 2.0 1.5 56 57 58 59 60 61 62 56 57 58 59 60 61 62 23SiO456(wt%) 7 SiO2(wt%) 2 CaO (wt%)

Supplementary Material #1 Click here to download Supplementary Data: Supplementary material #1.doc Appendix 1 Click here to download Supplementary Data: Appendix 1.xls Appendix 2 Click here to download Supplementary Data: Appendix 2.xls Appendix 3 Click here to download Supplementary Data: Appendix 3.doc Appendix 4 Click here to download Supplementary Data: APPENDIX 4.xls Appendix 5 Click here to download Supplementary Data: Appendix 5.doc