Post-Messinian drainage changes triggered by tectonic and climatic events (eastern Southern Alps, Italy)

Sedimentary Geology 239 (2011) 188–198

Contents lists available at ScienceDirect

Sedimentary Geology j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / s e d g e o

Post-Messinian drainage changes triggered by tectonic and climatic events (eastern Southern Alps, Italy) G. Monegato a,⁎, G. Vezzoli b a b

Dipartimento di Geoscienze, Università degli Studi di Padova, Via Gradenigo 6, 35131 Padova, Italy Dipartimento di Scienze Geologiche, Piazza della Scienza, 4, 20126, Università di Milano-Bicocca, Italy

a r t i c l e

i n f o

Article history: Received 6 September 2010 Received in revised form 20 May 2011 Accepted 29 June 2011 Available online 7 July 2011 Editor: G. J. Weltje Keywords: Messinian Pliocene Quaternary Eastern Southern Alps Provenance Compositional data analysis

a b s t r a c t The Messinian–Quaternary history of tectonic and climatic control on sedimentation in the eastern Southern Alps, northern Italy, was reconstructed using an integrated petrographic and sedimentological analysis of five sedimentary successions. These units mainly consist of fluvial conglomerates of the Tagliamento sequence, deposited within the eastern Southern Alps since the Upper Miocene (“Messinian Salinity Crisis”). At that time, the closure of marine gateways between the Atlantic Ocean and the Mediterranean Sea caused a drop in sea level, causing exchanged fluvial erosion and widening of the Alpine catchments. Sediment composition in the Upper Miocene to Lower Pliocene units shows an abrupt change in the source areas: from sediments characterized by carbonate rock fragments to detritus rich in low-grade metamorphic grains. In spite of tectonic activity within the eastern Southern Alps, no major modifications in sediment supply took place during the Pliocene–Early Pleistocene time span. In the Middle Pleistocene the first major expansion of the Alpine glaciers triggered a change in drainage patterns and a marked increase in erosion rates. Predominantly climatic control on sedimentation in the Tagliamento basin and the erosion of the Carnic Alps produced sediments rich in quartz, siltstone and metamorphic rock fragments, deposited in the Upper Pleistocene unit and in modern river sediments. © 2011 Elsevier B.V. All rights reserved.

1. Introduction Evolving drainage patterns and river avulsions provide crucial information on tectonic or climatic events punctuating the evolution of mountain belts and associated foreland basins. Specific attention to this aspect has been given only recently in provenance studies (Najman et al., 2003; Clift and Blusztajn, 2005; Dunkl et al., 2009; Monegato et al., 2010; Garzanti et al., 2011). However, retrieving paleogeodynamic information from orogenic sedimentary successions is not straightforward because of the complexity of basin–fill architectures (e.g., Heller et al., 1988; Jordan and Flemings, 1991; DeCelles and Giles, 1996). Though trends in sediment composition do provide fundamental clues regarding the various factors affecting detrital modes (i.e., parent lithology, chemical weathering, mechanical abrasion, hydraulic sorting, and diagenesis; Johnsson, 1993; Weltje and von Eynatten, 2004) a reliable interpretation of provenance signals requires additional information. In order to reconstruct the sequence of paleotectonic and paleoclimatic events punctuating the evolution of an orogen, full consideration must be given to juxtaposition and superposition of sedimentary bodies deposited in space and time by diverse paleorivers. Paleodrainage analysis of ancient terrigenous wedges of complex valley

⁎ Corresponding author. E-mail address: [email protected] (G. Monegato). 0037-0738/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.sedgeo.2011.06.012

fills (e.g., Dunkl et al., 2005) is a challenge that can be faced by using refined models of quantitative provenance, which consider the structural complexities of diverse orogen types (Weltje and von Eynatten, 2004; Garzanti et al., 2007). Using petrographic and sedimentological analyses linked to structural information (Monegato and Stefani, 2010), we investigate the drainage evolution of a sector of the eastern Southern Alps through two important tectonic and climatic events: (1) the “Messinian Salinity Crisis”, when a significant change in Mediterranean geodynamics triggered a drop in sea level (Duggen et al., 2003), transforming the Mediterranean into the largest saline basin in Earth's history; (2) and the Quaternary glaciations in the Alps, when climate cooled globally causing the reorganization of the Alpine paleodrainage (e.g. Schlunegger and Hinderer, 2003; Garzanti et al., 2011). These new data are used in conjunction with data from the literature to improve our knowledge of the Messinian–Quaternary history of tectonic and climatic control on sedimentation in the Alps. 2. Geological setting The Tagliamento basin is located within the eastern Southern Alps (Fig. 1) and covers an area of about 2500 km 2 (Fig. 2a). On the whole it is composed of two main sub-basins related to the Tagliamento s.s., object of the present work, and to the Fella River, its main tributary. The trunk valley is characterized by roughly E–W oriented reaches linked to the outlet through a narrow N–S reach (Fig. 2a). The

G. Monegato, G. Vezzoli / Sedimentary Geology 239 (2011) 188–198

Fig. 1. Map of the European Alps and surroundings with location of the study area; pale gray: elevation above 500 m; dark gray: elevation above 2500 m (see details in Fig. 2).

189

presence of wind-gaps with fluvial remains testifies to ancient tracks of the main streams (Monegato and Stefani, 2010), such as: the valley of Lake Cavazzo (Fig. 2b), N–S trending and parallel to the present-day trunk upstream of the valley mouth; and the reach of Ampezzo, E–W trending, abandoned during the Late Pleistocene for a southern stream piracy, likely caused by a landslide at “Passo della Morte” (Fig. 2a; Venturini, 2003). The exhumation of the eastern South Alpine Chain from the Miocene to the Present (e.g., Castellarin et al., 1992; Castellarin and Cantelli, 2000) determined the current setting of the mountain belt. Apatite fission track analysis indicates steady uplift at low rates from the Late Miocene onwards (Monegato et al., 2010); in the whole chain the youngest cooling ages related to the main tectonic structures are around 10 Ma, which come from the western sector of the chain (Zattin et al., 2003, 2006). Tectonic activity across the valley has been related to the complex structural setting of the chain (e.g. Bressan et al., 1998; Galadini et al., 2005; Burrato et al., 2008; Ponton, 2010), in which compressional and strike–slip movements occur; these tectonic adjustments produced local subsidence in reaches of the valley (Barnaba et al., 2010), in which remnants of the fluvial succession could have been preserved (Monegato and Stefani, 2011). This fact suggests that the evolution of the drainage basin was driven by other factors. The first was the dramatic sea level drop of the Messinian Salinity Crisis, which triggered deep incision of valleys that were subsequently filled during the Late Zanclean transgression (e.g., Ghielmi et al., 2010; Monegato

Fig. 2. a) Sketched geological map of the Tagliamento drainage basin, whose watershed is drawn in thick dashed line; b): DEM of the lower Tagliamento Valley; in black the extension of the studied units, thin black lines refer to geological sketches of Figs. 4 (C: Cavazzo Carnico; T: Tolmezzo) and 7 (O: Osoppo Hill section; SR: San Rocco Hill section); c) trace of the geological cross section in thin dashed line; main tectonic structures in thick black line, 1: Insubric Line; 2: Fella–Sava Fault; 3: Periadriatic overthrust. Location in black capital letters, A: Ampezzo; C: Cavazzo Carnico; E: Enemonzo; I: Invillino; P: Passo della Morte; O: Osoppo; and T: Tolmezzo. Geological cross section redrawn after Ponton (2010).

190

G. Monegato, G. Vezzoli / Sedimentary Geology 239 (2011) 188–198

et al., 2010; Monegato and Stefani, 2011). A second factor may have been the Quaternary glaciations, which have been documented in the Tagliamento drainage basin (e.g., Gortani, 1935; Venturini, 2003) and most of the evidence indicates that the last glacial advance occurred during the Late Pleistocene (Monegato et al., 2007). The increase of sediment discharge in the Eastern Alps was assessed for the Early Pleistocene (Kuhlemann et al., 2001, 2002; Mancin et al., 2009), and attributed to an early widespread episode of glaciations in the Alps (Mancin et al., 2009), even though the evidence of ice mass expansion are highlighted only for the end of the Early Pleistocene onwards (Muttoni et al., 2003, 2007). The modern Tagliamento basin cuts the portion of the Alps characterized by the strongest earthquakes (eastern South Alpine Chain, Galadini et al., 2005). The main tectonic structures divide the catchment into sectors (Fig. 2c) in which the low-grade metamorphic basement, the Palaeozoic–Cenozoic sedimentary sequences and the volcanites crop out. 2.1. Paleozoic successions The Variscan Chain is confined to the south by the Fella–Sava Fault, and to the north by the Insubric Line (Venturini, 1990). The succession is characterized by low-grade metamorphic units in the northwestern corner, beyond the Val Bordaglia Line (Sassi et al., 1995), which separates the epizonal sequences from the anchizonal one. The non-metamorphic Palaeozoic succession (e.g., Selli, 1963; Venturini, 1990, 2009) starts with Upper Ordovician sandstones and mudrocks, overlain by Silurian pelagic sediments. The Devonian part of the succession is more heterogeneous and is mainly composed of massive reef limestones and heteropic to pelagic limestones; a subsequent phase of subsidence led to the deposition of limestones and radiolarites rich in ammonoids across the Devonian–Carboniferous boundary. Thick siliciclastic to volcaniclastic turbidite wedges and volcanic intercalations accumulated during the climax of the Variscan Orogenic phase in the mid-Carboniferous (Läufer et al., 2001; Brime et al., 2008). The post-Variscan succession of the Pontebba Supergroup (e.g., Venturini, 1990, 2009) includes Upper Carboniferous quartzose conglomerates overlain by Lower Permian marine carbonates, locally interbedded with terrigenous deposits. 2.2. Permian to Middle Triassic cover South of the Fella–Sava Fault the sedimentary covers, related to Permian–Middle Triassic time span, are exposed (Massari et al., 1994; Venturini, 2009). To the west, the Tagliamento trunk valley marks the southern border of this succession (Ponton, 2010); while toward the east, it is merged with younger sedimentary units (Fig. 2a). The succession starts with Upper Permian continental sediments, conglomerates and red sandstones (Massari et al., 1994), overlain by shallow water carbonates and evaporites. The Lower Triassic Werfen Fm. is characterized by limestone and dolostone with thick red sandstones rich in micas. The Anisian–Ladinian cover is composed of reefs, heteropic to pelagic limestones, and terrigenous sediments, along with Ladinian felsic volcanites (Pisa, 1974).

2.4. Paleocene–Eocene flysch and Miocene terrigenous sequences South of the Periadriatic thrust, the Paleogene–Neogene terrigenous successions crop out. These are derived from sedimentation in the Venetian–Friulian Basin during different phases of the Alpine Orogenesis (Stefani et al., 2007). Paleogene–Eocene flysch successions are mainly terrigenous deposits capped by hemipelagic marls (Tunis and Venturini, 1992); whereas the latest Eocene units are biocalcarenites (Carulli et al., 1982). The Miocene, mainly terrigenous, succession is composed of shelf calcarenite and marl, accompanied by sandstone and conglomerate (Massari et al., 1986). 3. Stratigraphy of the Tagliamento Valley fill The Tagliamento Valley fill is bounded by angular unconformities that bracket a Messinian–Quaternary succession (Fig. 3). These deposits are primarily fluvial conglomerates (Monegato and Stefani, 2010), dominated by cobble- to pebble-size clasts, with subordinate sandstones, mudstones and breccias. The most continuous portion of the succession is located along the valley near Tolmezzo (Fig. 2b) in a series of ridges that, taken together, represent a 37 km long, 0.6– 1.2 km wide and 200 m thick belt. Downstream, the succession crops out in the Osoppo Hills (Fig. 2b), which are made of deltaic deposits, the so called Osoppo Conglomerate (Venturini, 1991, 2000), which has been assigned to the Zanclean (Monegato and Stefani, 2010). The chronology of the Tagliamento Valley fill has been drafted from a multidisciplinary study in which palynological analyses made in lacustrine clay levels provided proxy data in the form of characteristic pollen assemblages. Facies and structural analysis established the framework of the succession, while pebble and sandstone composition enabled a distinction between conglomerate units (Monegato and Stefani, 2010). The oldest unit of the succession is the Faeit Unit (Fig. 3), which is preserved at the highest elevation (Fig. 4) and has been heavily deformed by two fold systems. Pebble composition points to a correlation with the Messinian conglomerates that crop out in the foothills (Zanferrari et al., 2008). The Ambiesta Unit is located at a lower elevation than the Faeit (Fig. 4); but it is also heavily deformed by two fold systems. The Gilbert-type marine delta of Osoppo (Monegato et al., 2006) is a subunit (Fig. 3) that marks both the mouth of the valley and the base level for the fluvial sedimentation during the Late Zanclean transgression. The Cesclans Unit is bounded by angular unconformities and is probably Early Pleistocene in age (Monegato and Stefani, 2010); however, no direct chronologic data are available from this unit. The Ampezzo Unit lies on an angular unconformity. It is not folded, but has been faulted by strike–slip fault systems. It has been assigned to the Middle Pleistocene from pollen taken from a lacustrine layer interbedded within the conglomerates (Monegato and Stefani, 2010). The Invillino Unit is nested inside the older units and crops out only in the central part of the trunk valley, upstream of the Tagliamento/But junction. Because of the lack of outcrops in the Tolmezzo area, it has not been considered in the present work. The modern riverbed is nested within the older units, due to deepening of the trunk valley during the last glaciation. It contains post-glacial gravels.

2.3. Upper Triassic to Cretaceous cover 4. Analytical procedures Upper Triassic–Cretaceous cover consists of carbonates that crop out across the Fella–Tagliamento E–W valleys and south of them, including most of the Prealps (Carulli et al., 1987, 2000). The succession begins with Carnian dolostones, overlain by terrigenous and evaporitic units of the Late Carnian. The remainder of the succession derives from the development of the Friulian Shelf from the latest Carnian to the Cretaceous (Bosellini and Sarti, 1978) and the relative slope passing laterally to the pelagic limestone of the Belluno– Tolmino trough (Borsellini et al., 1981).

69 samples of the sand fraction, collected in the main stratigraphic sections of the valley fill near Cavazzo Carnico and of the Osoppo delta (Fig. 2b), were analyzed (Table 1). The entire sand fraction (0.0625– 2 mm) was split and impregnated with an epoxy resin according to the methodology described by Gazzi et al. (1973) to obtain thin sections for analyses. These were subsequently stained with alizarinered solution for the determination of the carbonate phases. Sandstone and sand counts were carried out following Gazzi–Dickinson

G. Monegato, G. Vezzoli / Sedimentary Geology 239 (2011) 188–198

191

Fig. 3. Chronostratigraphic scheme of studied units (modified from Monegato and Stefani, 2011). Chronostratigraphy after Gibbard et al. (2009). Eastern Southern Alps tectonic events from Caputo et al. (2010). Sediment discharge rate from Mancin et al. (2009). Onset of the MSC and Zanclean flood from Roveri et al. (2008). Late Zanclean transgression from Ghielmi et al. (2010). Onset of the Quaternary glaciations in the Alps from Muttoni et al. (2003).

procedures (Gazzi, 1966; Dickinson, 1970). For each section 500 (sandstones) or 300 points (sands) were determined, using a 0.5 mm grid spacing. To improve the information on the source rocks, a separate count of more than 200 rock fragments was performed on each sample. Eight compositional parameters were calculated with the petrographic data (Table 1). To characterize sediments of the modern Tagliamento River, the parameters of 13 samples of sand collected along the river were recalculated from Monegato et al. (2010). Following a simple nomenclature scheme (Crook, 1960; Dickinson, 1970) sediments were classified according to their main components exceeding 10% QFL (e.g. lithofeldsphatoquartzose sand Q N F N L N 10% QFL; Garzanti et al., 2011). An adjective reflecting the most common rock-fragment type was sometimes added (e.g. carbonaticlastic and metamorphiclastic; Ingersoll, 1983).

5. Compositional data analysis Geological data are often presented in percentages that represent relative contributions of the single variables to a whole. This means that the relevant information is contained only in the ratios between variables of the data, hereinafter referred to as compositional data, or compositions (Aitchison, 1986). Compositional data are by definition vectors of which each variable (component) is positive, with all components summing to a constant c usually chosen as 1 or 100, so that the when the variables can be represented as percentages. Unfortunately, the natural properties of compositional data are in contradiction to most of the methods provided by standard multivariate statistics. In practice, standard statistical methods can lead to questionable results if they are directly applied to the original compositional data (e.g. Aitchison, 1986; Pawlowsky-Glahn and

Fig. 4. Geological cross section through the Faeìt and the Tagliamento valleys from Cavazzo Carnico to Tolmezzo (see Fig. 2b for the location).

192

G. Monegato, G. Vezzoli / Sedimentary Geology 239 (2011) 188–198

Table 1 Detrital modes of Neogene–Quaternary sediments; sandstone samples are underlined. Q: quartz; P: plagioclase; Kf: K-feldspar; Lv: volcanic and subvolcanic lithic fragments; Lcc: limestone grains; Lcd: dolostone grains; Ls: shale, siltstone lithic fragments and chert grains; Lm: metamorphic lithic fragments. Samples

P

Kf

Lv

Lcc

Lcd

Ls

Lm

Tot

2.16 5.61 0.62 2.65 0.91 0.61 5.87 1.54 4.80 3.40 4.24 2.44 1.68

0.00 1.25 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.34

0.31 0.00 0.00 0.29 0.00 0.31 1.76 0.00 0.00 2.00 0.28 0.30 2.35

1.85 1.56 1.54 1.76 6.34 4.28 2.64 12.92 14.00 8.20 7.06 5.79 2.35

17.53 18.95 18.52 15.88 18.73 23.85 30.21 33.54 26.30 27.30 18.93 12.20 15.44

71.98 61.58 70.06 68.24 63.14 62.69 35.19 21.85 26.50 25.70 57.34 69.82 58.39

1.23 2.34 8.95 9.41 8.16 7.65 11.14 19.69 13.40 13.90 6.21 5.79 6.71

4.94 8.72 0.30 1.76 2.72 0.61 13.20 10.46 15.00 19.50 5.93 3.66 12.75

100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

049MG121 049GM128 049GM161 049GM165 049GM166 049GM167 049GM 240 049GM180 049GM144 049GM183 049GM182 049GM204 049GM203 525 049GM145 049GM135 049GM136 049GM138 049GM139 049GM158 049GM159 049GM164 049GM162 049GM172 049GM171 049GM168 049GM169 049GM196 049GM197 049GM198 049GM199 049GM241 049GM242 049GM117 049GM118 049GM120 526

18.01 11.11 21.10 19.31 23.87 12.62 8.21 16.33 18.37 14.40 18.64 5.34 5.96 5.90 15.94 12.91 11.27 13.73 12.50 21.87 14.96 15.10 6.38 7.64 8.00 7.04 9.89 5.86 2.39 0.97 5.98 3.48 1.23 6.09 8.33 11.01 8.70

0.00 0.00 0.55 0.29 0.30 0.00 0.00 0.29 0.00 0.51 0.00 0.00 0.00 0.00 0.29 0.00 0.28 0.00 0.00 0.00 0.26 0.00 0.00 0.00 0.33 0.25 0.00 0.00 0.00 0.00 0.00 0.32 0.00 0.00 0.00 0.61 0.00

2.25 1.70 1.10 0.29 0.60 1.23 1.17 0.58 0.52 0.77 1.13 1.78 0.94 0.60 0.58 0.82 1.13 0.33 0.50 1.33 2.36 0.85 0.00 0.64 0.33 0.50 0.80 0.31 1.37 0.32 0.28 0.95 0.31 1.60 0.00 0.61 0.30

15.43 11.11 10.41 5.19 8.76 5.23 6.74 6.41 6.04 6.94 7.63 11.87 10.03 18.40 2.90 4.95 10.70 2.94 2.25 9.63 9.19 8.55 3.95 12.42 14.33 9.30 8.56 7.10 7.85 6.15 5.98 16.14 9.85 12.18 17.67 8.87 16.90

15.11 12.59 23.29 17.00 21.45 28.31 20.53 16.91 22.57 22.11 25.99 15.73 18.50 32.50 23.48 24.45 29.01 13.73 22.25 12.53 20.73 23.36 29.48 29.62 25.00 18.09 23.53 24.69 41.30 23.62 19.37 22.15 30.15 24.36 24.00 27.22 20.90

25.08 30.62 21.92 8.65 5.14 12.92 14.96 16.62 12.86 7.97 10.45 10.98 15.67 8.30 10.14 20.33 18.87 40.20 24.00 17.07 24.67 31.05 28.88 28.03 26.33 34.17 26.74 33.33 26.62 42.72 26.21 27.53 25.23 30.45 28.67 29.36 17.40

10.29 18.02 13.42 29.68 31.72 27.69 20.82 24.20 25.20 25.96 22.32 30.56 31.03 21.00 36.23 18.13 18.31 22.88 24.00 19.77 18.64 12.54 22.49 12.42 16.33 25.13 18.45 16.98 9.22 15.21 23.65 15.51 11.69 12.82 11.33 13.46 15.30

13.83 14.85 8.22 19.60 8.16 12.00 27.57 18.66 14.44 21.34 13.84 23.74 17.87 13.30 10.43 18.41 10.42 6.21 14.50 17.80 9.19 8.55 8.81 9.24 9.33 5.53 12.03 11.73 11.26 11.00 18.52 13.92 21.54 12.50 10.00 8.87 20.50

100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

049GM195 049GM102 049GM103 049GM31 049GM237 049GM147 049GM28 049GM80 049GM81 049GM79 049GM62 049GM68 049GM78 049GM232 049GM99 049GM142 049GM71

5.66 9.24 8.52 14.65 11.25 14.67 11.10 27.46 22.55 27.57 28.93 24.13 18.63 16.57 28.62 27.98 9.74

0.00 0.66 0.32 0.47 0.63 0.00 0.30 0.00 0.00 0.00 0.31 0.32 0.33 0.00 0.64 0.52 0.00

0.94 1.98 1.58 0.47 2.50 0.27 0.30 0.29 0.65 1.33 0.31 0.63 0.98 0.58 1.61 0.26 0.32

9.43 5.94 11.36 12.79 8.44 5.16 16.40 6.94 4.58 11.30 7.23 6.67 3.92 3.20 3.54 1.81 4.87

15.72 19.14 23.66 6.98 21.88 29.62 25.20 18.21 11.11 7.97 14.15 32.38 39.22 6.10 12.22 22.80 19.16

32.08 27.06 24.61 30.23 24.38 10.87 15.30 36.42 46.41 37.54 32.39 14.60 19.61 56.69 31.51 19.17 49.03

19.81 13.86 13.25 17.91 14.69 11.41 15.60 8.67 11.44 7.64 13.21 19.37 16.67 13.37 16.72 25.39 12.01

16.35 22.11 16.72 16.51 16.25 27.99 15.80 2.02 3.27 6.64 3.46 1.90 0.65 3.49 5.14 2.07 4.87

100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

Holocene Tagliamento Tagliamento Tagliamento Tagliamento Tagliamento Tagliamento Tagliamento Tagliamento Tagliamento Tagliamento Tagliamento Tagliamento Tagliamento

S2662 S1512 506 513 504 515 503 517 518 049GM2 514 516 049GM1

Lower–Middle Pleistocene Stratigraphic units Ampezzo Ampezzo Ampezzo Ampezzo Ampezzo Ampezzo Ampezzo Ampezzo Ampezzo Ampezzo Ampezzo Ampezzo Ampezzo Ampezzo Cesclans Cesclans Cesclans Cesclans Cesclans Cesclans Cesclans Cesclans Cesclans Cesclans Cesclans Cesclans Cesclans Cesclans Cesclans Cesclans Cesclans Cesclans Cesclans Cesclans Cesclans Cesclans Cesclans Messinian–Zanclean Stratigraphic units Ambiesta Ambiesta Ambiesta Ambiesta Ambiesta Ambiesta Ambiesta Osoppo C. Osoppo C. Osoppo C. Osoppo C. Osoppo C. Osoppo C. Osoppo C. Osoppo C. Osoppo C. Osoppo C.

Q

G. Monegato, G. Vezzoli / Sedimentary Geology 239 (2011) 188–198

193

Table 1 (continued)

Osoppo Osoppo Osoppo Osoppo Osoppo Osoppo Osoppo Osoppo Osoppo Faéit Faéit Faéit Faéit Faéit Faéit

C. C. C. C. C. C. C. C. C.

Samples

Q

P

Kf

049GM88 049GM69 049GM143 049AZ5 049AZ8 049GM89 049GM93 049GM95 049GM100 049GM105 049GM106 049GM107 049GM123 049GM201 049GM202

1.85 7.62 8.06 2.62 3.40 5.11 8.43 4.59 3.95 2.74 4.25 3.82 4.39 4.52 10.41

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.66 0.30 0.00 0.00 0.00 0.00 0.00

0.31 0.66 0.30 0.00 0.00 1.14 0.29 1.31 0.66 0.91 0.98 0.35 0.00 0.60 0.63

Lv 3.70 3.31 1.49 2.62 1.83 3.98 3.49 9.84 4.93 2.40 2.29 3.82 3.13 3.31 5.05

Lcc

Lcd

Ls

17.90 36.09 56.42 26.89 29.58 10.23 12.50 31.80 30.59 25.91 23.86 21.88 21.94 19.58 11.67

43.52 26.49 14.63 45.25 51.05 40.06 37.79 40.33 51.64 61.44 59.15 62.50 59.87 64.76 62.78

30.86 23.51 17.91 15.41 10.99 34.38 35.47 7.21 6.91 3.90 4.25 4.51 8.46 6.93 5.99

Lm 1.85 2.32 1.19 7.21 3.14 5.11 2.03 4.92 0.66 2.40 5.23 3.13 2.19 0.30 3.47

Tot 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

Q = quartz; P = plagioclase; Kf = K-feldspar; Lv = volcanic and subvolcanic lithic fragments; Lcd = dolostone grains; Lcc = limestone grains; Ls = shale, siltstone lithic fragments and chert grains; Lm = metamorphic lithic fragments.

Egozcue, 2006). As a preferable alternative, a family of log-ratio transformations from the simplex to the standard Euclidean space were introduced (Aitchison, 1986; Egozcue et al., 2003) that make the standard statistical analyses viable. 5.1. Center and compositional biplot Among various descriptive statistics that can be easily computed on a compositional dataset, center and biplot functions provide particularly useful information (Daunis-I-Estadella et al., 2006). Before applying these statistical techniques, it was necessary to group variables with low concentrations that could affect the results and consequently lead to erroneous conclusions. Variables with small values usually incorporate larger errors than the other variables, which can lead, as in the case of principal component analysis, to misleading results. In our data, feldspars generally have concentrations of less than 2% (Table 1) and so were grouped with quartz. Center (Table 2) is the closed geometric mean and represents a measure of central tendency for our compositional dataset. Center is not closed to constant c and expresses information only about the ratios of parts of the center. When displaying three-part compositional data in a ternary diagram, one matter that frequently causes problems is the concentration of data points in a corner (one component dominant) or along a border (two components dominant). As a consequence, it is often difficult to observe any structure (or the lack of it) in the data (e.g. QFL, Fig. 5B1). Ternary Data plotting provides better visual patterns when enhanced by the mechanism of centering (e.g. QFL, Fig. 5b), which is simply a special case of perturbation. Centering consists of perturbing all the data by the same element, usually the inverse of the center of a dataset. This has the effect of moving the center of a dataset (red square) to the barycenter of the simplex, and the set of samples will gravitate around the barycenter, giving an automatic and optimal way of visualizing the data (Buccianti et al., 1999; Martín-Fernández

Table 2 Centers of the composition of petrographic parameters (in %) of each unit. Lcc

Lcd

Ls

Lm

Lower–Middle Pleistocene units Ampezzo 14.09 8.64 Cesclans 8.28 7.91

QF

Lv

20.25 23.36

12.94 25.80

22.68 16.99

15.34 11.47

Messinian–Zanclean units Ambiesta 11.81 Osoppo C. 11.26 Faèit 5.27 Global 10.00

18.74 19.55 20.19 20.86

22.15 33.94 61.72 25.69

14.99 15.23 5.45 15.63

18.41 2.68 2.12 7.38

9.25 4.08 3.21 6.30

et al., 1999; von Eynatten et al., 2002). In order to discriminate homogeneous provenance groups within our data set, we applied centered log-ratio (clr) transformations (Aitchison and Greenacre, 2002). We used the compositional biplot (Aitchison and Greenacre, 2002) for graphical display of both multivariate observations (points) and variables (rays; Fig. 5a). More details on the mathematical aspects of exploratory compositional data analysis can be found in Daunis-IEstadella et al. (2006). 6. Results The results of petrographic analysis of sands and sandstones and descriptive statistics are reported in Tables 1, 2 and Fig. 5, while qualitative examples are given in Fig. 6. In all samples, matrix is usually scarce and the framework is clast-supported. Cement is mostly equant calcite filling the pores and, occasionally, columnar isopachous calcite (Fig. 6e). Detritus chiefly consists of carbonate grains (microsparitic to micritic limestones and dolostones), metamorphic lithic fragments (phyllites, metarenites and metavolcanites), sedimentary grains (chert and siltstones) and felsic volcanic lithic fragments. Feldspars are scarce and normally altered. Heavy minerals are negligible. The comparison among centers of five groups and biplot analysis (Fig. 5a) highlighted how the lithic carbonaticlastic sediment of the Faeit Unit is well discriminated from the others by the high value of dolostone grains (microsparite and single crystals) and low quartz and feldspars contents (Fig. 6a). This matches also to the pebble composition, in which carbonate clasts exceed 75%, while volcanic and metamorphic clasts are absent (Monegato and Stefani, 2010). The lithic carbonaticlastic and quartzolithic carbonaticlastic sands of the Osoppo Conglomerate are characterized by abundant chert grains, siltstone fragments, quartz and feldspars. The results reported in Fig. 5a show a high dispersion of the Osoppo samples when compared with the others. In particular the biplot seems to display two subgroups within this unit, one rich in quartz and feldspars, and the other rich in limestone and dolostone grains. On the other hand, quartzolithic carbonaticlastic sediments of the Ambiesta Unit are characterized by abundant metamorphic lithic grains (phyllites, metarenites and minor metavolcanites), siltstone grains, quartz, feldspars and felsic volcanic grains (Fig. 6b). Cesclans Unit is characterized by limestone grains and siltstone lithic grains with minor volcanic grains (Fig. 6c). Ampezzo unit is discriminated by abundant siltstone grains, phyllite and metarenite rock fragments, quartz, feldspars and a scarcity of dolostone grains (Fig. 6d) In addition, the pebble-size composition is similar, with the lowest values in dolostone clasts and the highest in Paleozoic rock fragments (Monegato and Stefani, 2010). Combining information from Table 2 and Fig. 5a, it is possible to select a suitable three-part subcomposition for obtaining a clear discrimination among five units. The variables whose centers are

194

G. Monegato, G. Vezzoli / Sedimentary Geology 239 (2011) 188–198

Fig. 5. Compositional biplot (5a). The first two principal components of the biplot account for 69.40% of total variance. Original (5B1) and perturbed (5b), QFL-diagram (red squares indicate centers of samples). Ternary diagrams of the subcomposition QF, Lcd, and Lm (5c), and Lm, Lcd, and Ls (5d) after centering data (see Table 1 for the meaning of the abbreviations). Pale gray arrows indicate the compositional trend in the modern valley.

different and whose rays form angles higher than 90° in the biplot were chosen. Fig. 5 shows two ternary diagrams of the subcomposition (QF, Lcd, and Lm; Fig. 5c) and (Lm, Lcd, and Ls; Fig. 5d) after centering of the dataset (von Eynatten et al., 2002). In these plots the Faéit, Ambiesta, Cesclans and Ampezzo allostratigraphic units are clearly discriminated whereas Osoppo Conglomerate is characterized by elongate dispersion in two clusters near Lcd–QF vertex of the former and near Lcd–Ls vertex of the latter. This trend could suggest two different provenances for the sediments of the rivers feeding the Osoppo deltaic bodies. 7. Sediment provenance and drainage evolution of Tagliamento Valley The petrographic signature of the sedimentary succession of the Tagliamento basin can be tracked from the Messinian to the Present, showing the sedimentary evolution of the drainage network within the

eastern South Alpine Chain. According to AFT data, the Tagliamento catchment has been developed in a mountain belt characterized by lowrate uplift for the last 16 Ma (Monegato et al., 2010). In spite of this, the different units reveal a more dynamic evolution of the river basin. According to the stratigraphic subdivision, enhanced with chronological data, the succession crossed two important global events: the Messinian Salinity Crisis (e.g. Roveri et al., 2008 and references therein) and the onset of the Quaternary glaciations in the Alps (Muttoni et al., 2003). The lithic carbonaticlastic deposits of the Messinian Faéit Unit, which point to a smaller and confined catchment of the river (Fig. 9I), are well discriminated from the Zanclean units (Ambiesta and Osoppo) by the high dolostone grain content (Fig. 8a). In the Osoppo area, recent studies indicate the presence of two different deltaic bodies (western and eastern units; Fig. 7) related to the Late Zanclean transgression (Ghielmi et al., 2010; Monegato and Stefani, 2010).

G. Monegato, G. Vezzoli / Sedimentary Geology 239 (2011) 188–198

195

Fig. 6. Picture of the sand fraction of the stratigraphic units (scale bar is 140 μ). a) Faeit Unit; b) Ambiesta Unit; c) Cesclans Unit; d) Ampezzo Unit; e) isopach circumgranular calcite cementation on micritic limestone; the remaining porosity was occluded by equant calcite cement (Ampezzo Unit, thin section stained with Alizarine-Red for carbonate distinction); the meaning of the abbreviation of the clast types refers to Table 1.

Results of provenance and statistical analyses show how the western body consists of deltaic lithic carbonaticlastic sands (Figs. 7c and 8a) whereas the eastern body includes quartzolithic carbonaticlastic sediments (Figs. 7d and 8a). In the eastern delta body the palaeocurrents of the foreset beds indicate a feeder system coming from the east, likely flowing along the Periadriatic Thrust (Fig. 9II) that should have been active at that time (Castellarin and Cantelli, 2000). Sand petrography shows high ratios of quartz component as well as Lcd that may be in agreement with a palaeoriver eroding a bedrock mostly made of Lower Miocene terrigenous sandstone and Palaeogene turbidites at the footwall of the thrust (Poli, 2009) and by Upper Triassic dolostones at the hangingwall of the Periadriatic Thrust (Fig. 2c). On the other hand, palaeocurrent analyses and comparison with the modern Tagliamento sediments (Fig. 8a), suggest that the western sedimentary body should be related to the Tagliamento River system. The widening of the Tagliamento catchment, due to the Messinian event, induced a provenance change for the Ambiesta Unit. The

sedimentary succession records the erosion of the low-grade metamorphic rocks of the Carnic Alps (Table 2; Figs. 5c, d and 8a). A change in provenance ascribable to rapid exhumation of the chain is unlikely as AFT datings do not show ages younger than 10 Ma in the whole South Alpine Chain (Zattin et al., 2003, 2006; Monegato et al., 2010). From the Late Pliocene until the Early Pleistocene, no important changes in provenance occurred, although the deformation of the Cesclans Unit points to tectonic activity during this time span. In fact, the strike–slip movements along the Tagliamento Valley (Burrato et al., 2008) created confined subsiding reaches in which sedimentation took place, without significantly altering the drainage network (Monegato and Stefani, 2011). The second considered time span crosses the onset of the Quaternary glaciation in the Alps at the end of the Late Pleistocene (Muttoni et al., 2003). The petrographic signature of the Cesclans and Ampezzo units points to a change in sediment supply from lithic carbonaticlastic to

196

G. Monegato, G. Vezzoli / Sedimentary Geology 239 (2011) 188–198

a W 220

E San Rocco Hill

200 180 m a.s.l.

100 m

W 300 280

E

Osoppo Hill

260 240 220 200 180 m a.s.l. 100 m

Quaternary covers

eastern delta body

western delta body

bedrock (Tortonian sandstones)

b

Ls Lcd Lcd

Ls

Lcc

Lcd

Lcc

Q

Ls

Lcc Q

Lv

Q

Fig. 7. a) Geological sketches of the San Rocco Hill and of the Osoppo Hill; b) pictures of the sand fraction of the western (left) and the eastern (right) delta body (scale bar is 100 µ); the meaning of the abbreviation of the clast types refers to Table 1.

Fig. 8. Ternary diagrams of the subcomposition (QF; Lcd; and Lm). Diagram 8a discriminates well the two delta systems within the Osoppo conglomerates. Eastern delta rich in quartz, and western delta rich in dolostone lithic grains. Ellipses represent 90% of the confidence regions about the geometric mean (Aitchison, 1986; Weltje, 2002).

G. Monegato, G. Vezzoli / Sedimentary Geology 239 (2011) 188–198

197

basin may have increased the uplift of the Carnic Alps during Middle Pleistocene; however the lack of Plio–Pleistocene termochronological data (Monegato et al., 2010) indicate that this effect should have been weak. Another effect of glacier carving might have been some limited stream piracies along the watershed, as suggested by Venturini (2003), increasing the outcrop areas of Palaeozoic terrigenous units. This trend lasted until the Present, as indicated by the petrographic signatures of modern Tagliamento sediments (Fig. 7b). 8. Conclusions Quantitative provenance analysis on five fluvial successions deposited in the Tagliamento Valley, northern Italy, sheds light on the Messinian–Quaternary history of tectonic and climatic control on sedimentation in the eastern Southern Alps. Petrographic and sedimentological analyses indicate that the river has changed its drainage basin, driven by global climatic and eustatic events, as well as geodynamics. During the Messinian Salinity Crisis, the catchment widened and the Upper Miocene–Lower Pliocene units record an abrupt variation in composition, changing from lithic carbonaticlastic detritus (Faéit Unit) to quartzolithic carbonaticlastic sediments (Ambiesta Unit). In the Lower Pliocene, the paleo-Tagliamento delta was in the western Osoppo area, while more eastward, there was a second delta connected to a drainage system presently extinct. During the Upper Pliocene–Early Pleistocene, in spite of tectonic activity within the valley, detrital modes remained constant over time (Cesclans Unit). At the onset of the Quaternary glaciations, the river system (Ampezzo Unit) recorded an increase in contributions from the terrigenous and metamorphic rocks exposed in the most elevated mountains of the catchment. Climatic control on erosion rates predominates into the Present, as the action of Alpine glaciers triggers changes in the watershed and an increase in sediment supply. Acknowledgments The article benefited from constructive discussions with C. Stefani, M. Zattin, E. Garzanti, A. Resentini, M. Malusà are gratefully acknowledged. We thank Editor G.J. Weltje, as well as reviewers D. Fontana and H. v. Eynatten for their constructive and detailed revisions. We are grateful to G.C. Bryant for the revision of the English text. Funding by: CPDR 095351 of Padova University and CARG-FVG project (049 “Gemona del Friuli” sheet). References Fig. 9. Palaeogeographic reconstruction of the main evolution phases of the Tagliamento Valley: (I) during the Messinian the catchment was restricted to the central part of the relief; (II) after the deep incision, as a consequence of the sea-level drop of the Late Messinian, the drainage basin extended northwards, while the river flowed into the sea inlet forming the Osoppo delta; (III) during the Middle Pleistocene, in response to glaciations, the trunk valley was incised and forced to shift northwards (Monegato and Stefani, 2010); the valley mouth shifted southwards and the junction with Fella River was located inside the catchment. The watershed is shown as a dashed black line, the Tagliamento River system is indicated by a blue line. A: Ampezzo; C: Cavazzo Carnico; E: Enemonzo; I: Invillino; O: Osoppo; and T: Tolmezzo.

quartzolithic carbonaticlastic sands with a decrease of dolostone grains and an increase of quartz, siltstone and metamorphic lithic grains (Table 2; Fig. 8b). Detrital modes suggest an enhanced erosion of the Carnic Alps (Fig. 9III), in which terrigenous and metamorphic rocks extensively crop out (Fig. 2a). During the cold periods, ice tongues likely developed from this area at the inception; whereas the southern relief had smaller glaciers, because of the lower elevation, and were affected mainly by the large glacier flowing down the trunk valley. The climate effect on the erosion of the northern portion of the

Aitchison, J., 1986. The Statistical Analysis of Compositional Data. Chapman and Hall, London. Aitchison, J., Greenacre, M., 2002. Biplots of compositional data. Applied Statistics 51, 375–392. Barnaba, C., Marello, L., Vuan, A., Palmieri, F., Romanelli, M., Priolo, E., Breitenberg, C., 2010. The buried shape of an Alpine valley from gravity surveys, seismic and ambient noise analysis. Geophysical Journal International 180, 715–733. Borsellini, A., Masetti, D., Sarti, M., 1981. A Jurassic “Tongue of the Ocean” infilled with oolitic sands: the Belluno trough, Venetian Alps, Italy. Marine Geology 44, 59–95. Bosellini, A., Sarti, M., 1978. Geologia del gruppo M. Cuar–M. Covria. Giornale di Geologia 43, 47–88. Bressan, G., Snidarcig, A., Venturini, C., 1998. Present state of tectonic stress of the Friuli region (eastern southern Alps). Tectonophysics 292, 211–227. Brime, C., Perri, M.C., Pondrelli, M., Spalletta, C., Venturini, C., 2008. Polyphase metamorphism in the eastern Carnic Alps (N Italy–S Austria): clay minerals and Conodont Colour Alteration Index evidence. International Journal of Earth Sciences 97, 1213–1229. Buccianti, A., Pawlowsky-Glahn, V., Barceló-Vidal, C., Jaruata-Bragulat, E., 1999. Visualization and modeling of natural trends in ternary diagrams: a geochemical case study. In: Lippard, S.J., Naess, A., Sinding-Larsen, R. (Eds.), Proceedings of the 5th Annual Conference of the International Association for Mathematical Geology, Trondheim, Norway, pp. 139–144. Burrato, P., Poli, M.E., Vannoli, P., Zanferrari, A., Basili, R., Galadini, F., 2008. Sources of Mw 5+ earthquakes in northeastern Italy and western Slovenia: an updated view based on geological and seismological evidence. Tectonophysics 453, 157–176. Caputo, R., Poli, M.E., Zanferrari, A., 2010. Neogene–Quaternary tectonic stratigraphy of the eastern Southern Alps, NE Italy. Journal of Structural Geology 32, 1009–1027.

198

G. Monegato, G. Vezzoli / Sedimentary Geology 239 (2011) 188–198

Carulli, G.B., Zucchi Stolfa, M.L., Pirini, Radrizzani C., 1982. L'Eocene di M. Forcella (Gruppo del M.Amariana–Carnia orientale). Memorie Società Geologica Italiana 24, 65–70. Carulli, G.B., Frizzo, P., Longo Salvador, G., Semenza, E., Bianchin, G., Mantovani, F., Mezzacasa, G., 1987. La geologia della zona fra il T. Chiarzò e il F. Fella (Alpi Carniche). Giornale di Geologia 49, 1–32. Carulli, G.B., Cozzi, A., Longo Salvador, G., Pernarcic, E., Podda, F., Ponton, M., 2000. Carta Geologica delle Prealpi Carniche. Ed. Museo Friulano Storia Naturale, Udine. Castellarin, A., Cantelli, L., 2000. Neo-Alpine evolution of the eastern Southern Alps. Journal of Geodynamics 30, 251–274. Castellarin, A., Cantelli, L., Fesce, A.M., Mercier, J., Picotti, V., Pini, G.A., Prosser, G., Selli, L., 1992. Alpine compressional tectonics in the southern Alps. Relations with the N-Apennines. Annales Tectonicae 6, 62–94. Clift, P.D., Blusztajn, J., 2005. Reorganization of the western Himalayan river system after five million years ago. Nature 438, 1001–1003. Crook, K.A.W., 1960. Classification of arenites. American Journal of Science 258, 419–428. Daunis-I-Estadella, J., Barceló-Vidal, C., Buccianti, A., 2006. Exploratory compositional data analysis. In: Buccianti, A., Mateu-Figueras, G., Pawlowsky-Glahn, V. (Eds.), Compositional data analysis in the geosciences: from theory to practice: Geological Society of London Special Publications, 264, pp. 161–174. DeCelles, P.G., Giles, K.A., 1996. Foreland basin systems. Basin Research 8, 105–123. Dickinson, W.R., 1970. Interpreting detrital modes of graywacke and arkose. Journal of Sedimentary Research 40, 695–707. Duggen, S., Hoernle, K., van den Bogaard, P., Rüpke, L., Morgan, J.P., 2003. Deep roots of the Messinian salinity crisis. Nature 422, 602–605. Dunkl, I., Kuhlemann, J., Reinecker, J., Frisch, W., 2005. Cenozoic relief evolution of the Eastern Alps — constraints from apatite fission track age-provenance of Neogene intramontane sediments. Austrian Journal of Earth Science 98, 92–105. Dunkl, I., Frisch, W., Kuhlemann, J., Brügel, A., 2009. Pebble population dating as an additional tool for provenance studies — examples from the Eastern Alps. Geological Society London Special Publications 324, 125–140. Egozcue, J.J., Pawlowsky-Glahn, V., Mateu-Figueraz, G., Barceló-Vidal, C., 2003. Isometric logratio transformations for compositional data analysis. Mathematical Geology 35, 279–300. Galadini, F., Poli, M.E., Zanferrari, A., 2005. Seismogenic sources potentially responsible for earthquakes with M ≥ 6 in the eastern Southern Alps (Thiene–Udine sector, NE Italy). Geophysical Journal International 161, 739–762. Garzanti, E., Doglioni, C., Vezzoli, G., Andò, S., 2007. Orogenic belts and orogenic sediment provenance. Journal of Geology 115, 315–334. Garzanti, E., Vezzoli, G., Andò, S., 2011. Paleogeographic and drainage changes during Pleistocene glaciations (Po Plain, Northern Italy). Earth Science Reviews 105, 25–48. Gazzi, P., 1966. Le arenarie del flysch sopracretaceo dell'Appennino modenese: correlazioni con il Flysch di Monghidoro. Mineralogica Petrographica Acta 12, 69–97. Gazzi, P., Zuffa, G.G., Gandolfi, G., Paganelli, L., 1973. Provenienza e dispersione litoranea delle sabbie delle spiagge adriatiche fra le foci dell'Isonzo e del Foglia: inquadramento regionale. Memorie della Società Geologica Italiana 12, 1–37. Ghielmi, M., Minervini, M., Nini, C., Rogledi, S., Rossi, M., Vignolo, A., 2010. Sedimentary and tectonic evolution in the eastern Po-Plain and northern Adriatic Sea area from Messinian to Middle Pleistocene (Italy). Rendiconti Fisica Accademia dei Lincei 21 (Suppl. 1), S131–S166. Gibbard, P.L., Head, M.J., Walker, M.J.C., The Subcommission on Quaternary Stratigraphy, 2009. Formal ratification of the Quaternary System/Period and the Pleistocene Series/Epoch with a base at 2.58 Ma. Journal of Quaternary Science 25, 96–102. Gortani, M., 1935. I terrazzi del bacino montano del Tagliamento e nelle valli contigue. Giornale di Geologia 9, 1–41. Heller, P.L., Angevine, C.L., Winslow, N.S., Paola, C., 1988. Two-phase stratigraphic model of foreland–basin sequences. Geology 16, 501–504. Ingersoll, R.V., 1983. Petrofacies and provenance of Late Mesozoic forearc basin, northern and central California. American Association of Petroleum Geologists Bulletin 67, 1125–1142. Johnsson, M.J., 1993. The system controlling the composition of clastic sediments. In: Johnsson, M.J., Basu, A. (Eds.), Processes controlling the composition of clastic sediments: Geological Society America Special Paper, 284, pp. 1–19. Jordan, T.E., Flemings, P.B., 1991. Large-scale stratigraphic architecture, eustatic variation, and unsteady tectonism: a theoretical evaluation. Journal of Geophysical Research 96, 6681–6699. Kuhlemann, J., Frisch, W., Dunkl, I., Székely, B., 2001. Quantifying tectonic versus erosive denudation by the sediment budget: the Miocene core complexes of the Alps. Tectonophysics 330, 1–23. Kuhlemann, J., Frisch, W., Székely, B., Dunkl, I., Kazmer, M., 2002. Post-collisional sediment budget history of the Alps: tectonic versus climatic control. International Journal of Earth Science 91, 818–837. Läufer, A.L., Hubich, D., Loeschke, J., 2001. Variscan geodynamic evolution of the Carnic Alps (Austria/Italy). International Journal Earth Science 90, 855–870. Mancin, N., Di Giulio, A., Cobianchi, M., 2009. Tectonic vs. climate forcing in the Cenozoic sedimentary evolution of a foreland basin (Eastern Southalpine system, Italy). Basin Research 21, 799–823. Martín-Fernández, J.A., Bren, M., Barceló-Vidal, C., Pawlowsky-Glahn, V., 1999. A measure of difference for compositional data based on measures of divergence. In: Lippard, S.J., Naess, A., Sinding-Larsen, R. (Eds.), Proceedings of the 5th Annual Conference of the International Association for Mathematical Geology, Trondheim, Norway, pp. 211–216. Massari, F., Grandesso, P., Stefani, C., Zanferrari, A., 1986. The Oligo-Miocene Molasse of the Veneto–Friuli region, Southern Alps. Giornale di Geologia 48, 235–255. Massari, F., Neri, C., Pittau, P., Fontana, D., Stefani, C., 1994. Sedimentology, palinostratigraphy and sequence stratigraphy of a continental to shallow marine

rift-related succession: Upper Permian of the eastern Southern Alps (Italy). Memorie Scienze Geologiche 46, 119–243. Monegato, G., Stefani, C., 2010. Stratigraphy and evolution of a long-lived fluvial system in the southeastern Alps (NE Italy): the Tagliamento conglomerate. Austrian Journal Earth Science 103, 33–49. Monegato, G., Stefani, C., 2011. Preservation of a long-lived fluvial system in a mountain chain: the Tagliamento Valley (Southeastern Italian Alps). In: Davidson, S.K., Leleu, S., North, C.P. (Eds.), From river to rock record: The preservation of fluvial sediments and their subsequent interpretation: SEPM Spec. Publ., 97, pp. 359–374. Monegato, G., Zanferrari, A., Gliozzi, E., 2006. Stratigraphy, sedimentology and age of the Osoppo Hill deposits. In: Melis, R., Romano, R., Fonda, G. (Eds.), Giornate di Paleontologia 2006, guida alle escursioni. EUT, Trieste, pp. 81–83. Monegato, G., Ravazzi, C., Donegana, M., Pini, R., Calderoni, G., Wick, L., 2007. Evidence of a two-fold glacial advance during the Last Glacial Maximum in the Tagliamento end moraine system (eastern Alps). Quaternary Research 68, 284–302. Monegato, G., Stefani, C., Zattin, M., 2010. From present rivers to old terrigenous sediments: the evolution of the drainage system in the eastern Southern Alps. Terra Nova 22, 218–226. Muttoni, G., Carcano, C., Garzanti, E., Ghielmi, M., Piccin, A., Pini, R., Rogledi, S., Sciunnach, D., 2003. Onset of major Pleistocene glaciations in the Alps. Geology 31, 989–992. Muttoni, G., Ravazzi, C., Breda, M., Pini, R., Laj, C., Kissel, C., Mazaud, A., Garzanti, E., 2007. Magnetostratigraphic dating of an intensification of glacial activity in the southern Italian Alps during Marine Isotope Stage 22. Quaternary Research 67, 161–173. Najman, Y., Garzanti, E., Pringle, M., Bickle, M., Stix, J., Khan, I., 2003. Early–Middle Miocene paleodrain-age and tectonics in the Pakistan Himalaya. Geological Society of America Bulletin 115, 1265–1277. Pawlowsky-Glahn, V., Egozcue, J.J., 2006. Compositional data and their analysis: an introduction. In: Buccianti, A., Mateu-Figueras, G., Pawlowsky-Glahn, V. (Eds.), Compositional data analysis in the geosciences: from theory to practice: Geological Society of London Special Publications, 264, pp. 1–10. Pisa, G., 1974. Tentativo di ricostruzione paleoambientale e paleostrutturale dei depositi di piattaforma carbonatici medio triassica delle Alpi Carniche sudoccidentali. Memorie Società Geologica Italiana 13, 35–83. Poli, M.E., 2009. La carta geologica del massiccio della Bernadia (Prealpi Giulie meridionali, Friuli, Italia NE). Rendiconti online Società Geologica Italiana 5, 168–171. Ponton, M., 2010. Architettura delle Alpi Friulane. Edizioni Museo Friulano di Storia Naturale 52, 1–80. Roveri, M., Bertini, A., Cosentino, D., Di Stefano, A., Gennari, R., Gliozzi, E., Grossi, F., Iaccarino, S.M., Lugli, S., Manzi, V., Taviani, M., 2008. A high-resolution stratigraphic framework for the latest Messinian events in the Mediterranean area. Stratigraphy 5, 323–342. Sassi, R., Arkai, P., Lantai, C., Venturini, C., 1995. On the boundary between the epimetamorphic South Alpine basement and the anchimetamorphic Paleozoic sequences of the Carnic Alps: illite crystallinity and vitrinite reflectance data. Schweizerische Mineralogische und Petrographische 75 (3), 399–412. Schlunegger, F., Hinderer, M., 2003. Pleistocene/Holocene climate change, reestablishment of fluvial drainage network and increase in relief in the Swiss Alps. Terra Nova 15, 88–95. Selli, R., 1963. Schema geologico delle Alpi Carniche e Giulie occidentali. Giornale di Geologia 30, 1–136. Stefani, C., Fellin, M.G., Zattin, M., Zuffa, G.G., Dalmonte, C., Mancin, N., Zanferrari, A., 2007. Provenance and paleogeographic evolution in a multisource foreland: the Cenozoic Venetian–Friulian Basin (NE Italy). Journal of Sedimentary Research 77, 867–887. Tunis, G., Venturini, S., 1992. Evolution of the southern margin of the Julian Basin with emphasis on the megabeds and turbidite sequence of the southern Julian Prealps (NE Italy). Geologia Croatica 45, 127–150. Venturini, C., 1990. Geologia delle Alpi Carniche centro-orientali. Museo Friulano Storia Naturale, Udine. Venturini, C., 1991. Il conglomerato di Osoppo. Gortania, Atti Museo Friulano Storia Naturale 13, 31–49. Venturini, C., 2000. Significato dei conglomerati. In: Carulli, G.B. (Ed.), Guida alle escursioni. 80° Riunione Soc. Geol. Ital., Trieste, 6–8 settembre 2000. Ediz. Univ, Trieste, pp. 118–120. Venturini, C., 2003. Il Friuli nel Quaternario: l'evoluzione del territorio. In: Muscio, G. (Ed.), Glacies. Comune di Udine-Museo Friulano Storia Naturale, pp. 23–106. Venturini, C., 2009. Note illustrative della Carta Geologica d'Italia alla scala 1:50.000: Foglio 031 “Ampezzo”. APAT-Servizio Geologico d'Italia. LAC, Firenze. von Eynatten, H., Pawlowsky-Glahn, V., Egozcue, J., 2002. Understanding perturbation on the simplex: a simple method to better visualise and interpret compositional data in ternary diagrams. Mathematical Geology 34, 249–257. Weltje, G.J., 2002. Quantitative analysis of detrital modes: statistically rigorous confidence methods in ternary diagrams and their use in sedimentary petrology. Earth Science Reviews 57, 211–253. Weltje, G.J., von Eynatten, H., 2004. Quantitative provenance analysis of sediments: review and outlook. Sedimentary Geology 171, 1–11. Zanferrari, A., Avigliano, R., Grandesso, P., Monegato, G., Paiero, G., Poli, M.E. and Stefani, C., 2008. Note illustrative della Carta Geologica d'Italia alla scala 1:50.000: Foglio 065 “Maniago”. APAT-Servizio Geologico d'Italia — Regione Autonoma Friuli Venezia Giulia, GraphicLinea, Udine. Zattin, M., Stefani, C., Martin, S., 2003. Detrital fission-track analysis and petrography as keys of Alpine exhumation: the example of the Veneto foreland (Southern Alps, Italy). Journal of Sedimentary Research 7, 1051–1061. Zattin, M., Cuman, A., Fantoni, R., Martin, S., Scotti, P., Stefani, C., 2006. From Middle Jurassic heating to Neogene cooling: the thermochronological evolution of the Southern Alps. Tectonophysics 414, 192–202.