Mesozoic tectonics and volcanism of Tethyan rifted continental margins in western Sicily

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Mesozoic tectonics and volcanism of Tethyan rifted continental margins inwestern Sicily

Luca Basilone 1, Maurizio Gasparo Morticelli ⁎, Gabriele Lena 2

Department of Geology and Geodesy, University of Palermo, Via Archirafi 20/22, C.A.P. 90123 Palermo, Italy

a b s t r a c ta r t i c l e i n f o

Article history:Received 2 November 2009Received in revised form 19 February 2010Accepted 24 February 2010Available online 2 March 2010

Communicated by M.R. Bennett

Keywords:Mesozoic tectonics and volcanismRifted continental marginPaleogeographyWestern Sicily

The paleotectonic and volcanic features of the Jurassic–Cretaceous carbonate successions, outcropping incentral-western Sicily, allow us to restore the tectono-sedimentary evolution of a sector of the Africancontinental margin. These successions consist of shallow-to-deep-water Mesozoic deposits that have formedin the carbonate platform-to- pelagic plateau depositional setting of the so-called Trapanese paleogeographicdomain. Fieldwork, including structural analyses, has indicated the occurrence of lateral facies changes,resedimented materials, volcanic products (pillow lavas and tuffitic deposits), unconformity surfaces andpaleofaults of different trends and age. These data, combined with facies and a physical–stratigraphicanalysis, allow one to distinguish between the different tectono-stratigraphic settings. A structural low, filledwith thick pillow lavas and reworked deposits, appears bordered by two main structural highs: an articulatecarbonate-pelagic platform with a stepped fault margin, and the flank of a structural high, where thevolcanoclastic deposits are interlayered with reworked reef materials, suggest the occurrence of a submarinevolcano, that evolved into an atoll-type carbonate shelf setting. Tectonic and magmatic events punctuatedthe sedimentary evolution during the Early Jurassic, Middle–Late Jurassic, Early and Late Cretaceous.The horst and graben structures connected by steeped margins and the occurrence of distinctive types ofvolcanic products suggest that the study areas could represent a sector of the Jurassic–Cretaceous southernTethyan passive continental margin, situated at the edge of the continental platform bordering those basinalareas where rifting and possible spreading processes were active during the Mesozoic.

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1. Introduction

Western Sicily represents a key area in the Central Mediterraneanfor the understanding of the Mesozoic evolution of Tethyanpaleogeography. The so-called Tethyan realm was a stronglyfragmented area (Biju-Duval and Dercourt, 1980; Dercourt et al.,1986; Ziegler, 1988) with isolated sectors of continental lithosphere,sometimes separated by oceanic crust, passively moving along an E–Wtrend in the western Tethys (according to the transform faults of theAtlantic opening).

A new paleogeographical reconstruction of the central Mediterra-nean supports continental crust rifting and thinning phases duringPermian–Late Triassic to Jurassic as well as the formation of an oceaniccrust flooring the Ionian Sea (Dercourt et al., 1986; Catalano et al.,1991, 2001; Finetti et al., 2005).

Stratigraphic and structural data are consistent with a SicilianTriassic–Jurassic crustal palaeogeography characterized by a wide

carbonate platform (Panormide, Trapanese–Saccense and Iblean) thathas developed on the African continental crust, flanked, to the(present-day) north, by a large basinal area (Imerese and Sicanian),growing on a stretched continental crust.

Rifted continental margins frequently display submarine topo-graphical highs, capped by condensed pelagic sequences withadjacent slope-to-basinal areas with pelagic succession associated tomagmatic rocks (Ziegler, 1988; Alvarez, 1990; Favre and Stampfli,1992; Robertson, 1998; Dercourt et al., 2000; Stampfli et al., 2001;Whitmarsh and Wallace, 2001; Stampfli and Borel, 2002; Robertson,2006, 2007).

During the Jurassic period, the southern Tethyan continentalmargin was affected by extensive tectonics related to the well knownsyn-rift and early post-rift phases. Tectonic control of the pelagicsedimentation, resulting from the Early Jurassic break-up of theoriginal carbonate platforms (Jenkyns, 1970a), was studied on Triassicand Jurassic sequences in the Southern Alps, the Apennines andwestern Sicily (Wendt, 1969; Jenkyns, 1970a, 1971; Wendt, 1971;Bernoulli and Jenkyns, 1974; Castellarin et al., 1978; Catalano andD'Argenio, 1978, 1982a; Winterer and Bosellini, 1981; Lemoine et al.,1986; Eberli, 1988; Alvarez, 1990; Bertotti et al., 1993).

The Mesozoic carbonate and pelagic platform successions (sensuCatalano et al., 1977) of the Trapanese–Saccense domain (Catalano

Sedimentary Geology 226 (2010) 54–70

⁎ Corresponding author. Tel.: +39 3466201778 (mobile).E-mail addresses: [email protected] (L. Basilone), [email protected]

(M.G. Morticelli), [email protected] (G. Lena).1 Tel.: +39 3382674245 (mobile).2 Tel.: +39 3805130811 (mobile).

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and D'Argenio 1978, 1982b), which outcropwidely in central-westernSicily (Fig. 1a), display typical tectonic and volcanic features,particularly in the Jurassic–Cretaceous. These successions consist ofTriassic–Lower Jurassic peritidal limestones, and Jurassic–Eocenecondensed to pelagic deposits, to which Miocene carbonate-clasticand marly deposits, unconformably follow.

Several tectono-sedimentary features of the Triassic–JurassicTrapanese–Saccense carbonate platform have been previouslydescribed from the Monte Kumeta (Fig. 1a, Jenkyns 1970b, 1971;Catalano and D'Argenio, 1990; Di Stefano and Mindszenty, 2000; DiStefano et al., 2002) and Rocca Busambra ridge outcrops (Wendt,1965, 1971; Mascle, 1973; Giunta and Liguori, 1975; Mascle, 1979;Basilone, 2009; Bertok and Martire, 2009). Some of these authorssuggested a Jurassic evolution of the peritidal carbonate platform toa basin and swell system connected by escarpments.

The volcanism of the Tethyan rifted margins, that were formedboth in deep-water (Vianelli, 1970; Laubscher and Bernoulli, 1977;Catalano et al., 1991; Robertson, 2006, 2007) and in an intraplatformbasin setting (Patacca et al., 1979; Reuber et al., 1992; Searleet al., 1997), have been examined in detail in the Mediterraneanregion.

In Sicily theMesozoic volcanism and its stratigraphic position havebeen thoroughly investigated (Fabiani, 1926; Trevisan, 1937; Broquet,1968; Broquet and Mascle, 1968; Caflisch and Crescenti, 1969;Broquet and Mascle, 1970; Catalano and Montanari, 1979; GasparoMorticelli and Lena, 2008). In particular Catalano and D'Argenio(1978, 1982a,b), Lucido et al. (1978), Bellia et al. (1981) and Ferla etal. (2002) have specifically referred the Middle–Late Jurassic Sicilianvolcanism to the Tethyan rifting.

The main aim of the present paper is to illustrate, by means of adetailed stratigraphic and sedimentological analysis, several fea-tures concerning the occurrence of synsedimentary tectonics andvolcanism, identified within the Jurassic–Cretaceous carbonate-pelagic platform successions that outcrop in Western Sicily. Wedeal hereafter with three regions, where the easternmost outcropsof the Trapanese successions are exposed. The investigated regionsare (Fig. 1):

(a) Rocca Busambra, located to the north of the town of Corleone,where field work, supported by detailed facies analysis andlarge-scale mapping ,highlighted widespread facies variabilityin the Jurassic–Cretaceous deposits and the occurrence ofsynsedimentary tectonics.

(b) Monte Balatelle, to the east of the town of Marineo, representsthe eastward termination of the Monte Kumeta ridge, wherelarge, thick basaltic bodies and their stratigraphic relationshipswith the Jurassic–Cretaceous sedimentary succession, havebeen identified.

(c) The large carbonate blocks, exposed near the towns of Vicari andRoccapalumba consist of Jurassic–Cretaceous slope-to-basinsuccessions, which are characterized by metre-thick volcanicmaterials. Our new data reveal the presence of basalts andvolcaniclastic materials interlayered with reworked shallow-water deposits.

A comparative analysis of the collected data permitted us to pointout the common characteristics as the study areas evolved.

2. Geological framework

The successions studied here belong to the Sicilian fold and thrustbelt, a sector of the Maghrebian–Apennine system (Fig. 1b). Thisthrust and fold belt originates from the piling-up of tectonic bodies,deriving from the deformation of the palaeogeographic domains thatdeveloped during the Meso-Cenozoic in the Sicilian sector of thesouthern Tethyan (or African) continental margin. Their tectonicemplacement took place during the Miocene–Middle Pleistocene. It iscommonly assumed that there was a S-SE thrust propagation(Catalano and D'Argenio, 1978; Catalano et al., 2000) accompaniedby clockwise rotations (Channel et al., 1990; Oldow et al., 1990) andtranspressive movements (Ghisetti and Vezzani, 1984; Oldow et al.,1990; Avellone et al., 2010).

The western Sicily fold and thrust belt is a pile of thrust sheets(Fig. 2a) formed, as shown by the several regional seismic lines(Catalano et al., 2000), starting from the bottom, by (Fig. 2b): a) twomain imbricated thrust wedges of carbonate platform tectonic units(Trapanese–Saccense); b) a wedge of deep-water carbonate thrustsheets (Sicanian and Imerese units) and c) the Numidian flysch nappe.In some places these units appear to be sealed, by syntectonic deposits(thrust top basins), consisting ofMiocenemolasse deposits, Messinianevaporites and Pliocene pelagites. In this tectonic framework, thestudied E–W-trending Rocca Busambra, Kumeta–Balatelle and Vicari–Roccapalumba regions appear to pertain to the upper unit of thecarbonate platform thrust wedge. The profile (Fig. 2b) well illustratesthe overthusting of the deep-water carbonate thrusts, above the maincarbonate substrate.

Fig. 1. a) Distribution of the Jurassic–Cretaceous Trapanese pelagic carbonate platform rock successions in central-western Sicily. b) Tectonic map of the central Mediterranean(modified from Catalano et al., 2000), 1 Corsica–Sardinia domain; 2 Calabro–Kabilian Arc, “internal” Flysch sequences, ophiolites; 3 Maghrebian–Sicilian–South Apennine Chain anddeformed foreland; 4 undeformed foreland (Tunisia, Hyblaean Plateau, Apulia); 5 Extensional areas ; 6 Plio-Quaternary volcanics.

55L. Basilone et al. / Sedimentary Geology 226 (2010) 54–70


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3. Mesozoic lithostratigraphy of the Trapanese succession

The Trapanese successions, as previously defined by severalauthors (Catalano and D'Argenio, 1978, 1982b, 1990; Mascle, 1979;Montanari, 1989; Di Stefano et al., 2002), consist of Mesozoic–

Paleogene carbonate platform-to-pelagic deposits, covered by Mio-cene clastics. Upper Triassic–Lower Jurassic peritidal limestones,developed in a Bahamian-type depositional setting (Sciacca andInici Formations) are the substrate of the Jurassic–Cretaceouscondensed pelagic limestones. The latter encompasses (Fig. 3).

Fig. 4. Characteristic facies andmicrofacies of the Jurassic study successions: a) Fe–Mn nodules and dark crusts of the Bositra limestones (lower Rosso Ammonitico mb of the BuccheriFm, Rocca Busambra); b) bioclastic wackestone, with benthic foraminifera, pelagic bivalves and thick-shelled mollusca fragments, often Mn-coated (Bositra limestones, RoccaBusambra, PPL, scale bar 1 mm); c) thick body of basaltic pillow lava interlayered in the Bositra limestones of Monte Balatelle; d) darkish basalts interlayered in the Jurassicsuccession of Monte Balatelle (sample fromwell, PPL, scale bar 1 mm); e) crossed laminated tuffitic sands enclosed between basalts (below) and the Bajocian–Bathonian limestonesof the Vicari succession (above); f) Middle Jurassic red basaltic pillow lavas (Monte Balatelle); g) wackestone–packstone with benthic foraminifera, Aptychus, bryozoans,calpionellids, thin- and thick-shelled bivalve fragments, crinoids (Saccocoma limestones, Pizzo Marabito, Rocca Busambra, PPL, scale bar 1 mm).



3.1. Crinoidal limestones

Red-to-white massive calcareous sandstones, a few metres thick.Crinoid ossicles and plates (Pentacrinus sp.), benthic foraminifera(Involutina liassica Jones) and micritized grains are abundant. Thesedeposits, sporadically outcropping in the Piano Pilato region (RoccaBusambra) mostly as a filling of the neptunian dykes, have been datedby Wendt (1963, 1971) as Toarcian.

3.2. “Rosso Ammonitico” beds

They pertain to the Buccheri Fm (Patacca et al., 1979), that followsa blackish Fe–Mn hardground, marking the top of the so-called IniciFm. In western Sicily, this formation has been subdivided into threemembers (Catalano and D'Argenio, 1990; Di Stefano, 2002; Di Stefanoet al., 2002): a) a lowermember consisting of massive condensed red-to-pink mudstone/wackestone with thin-shelled pelagic bivalves(Bositra buchi Roemer), protoglobigerinids, and dark ferromanganesecrusts, a few metres thick; this lithofacies, called Bositra limestoneshere, is followed by nodular, reddish marly limestones enclosing arich ammonitic fauna (Stephanoceras humpresianum, Garantianagarantiana, Parkinsonia parkinsoni, Hecticoceras (Phroecticoceras)retrocostatum, Reneckeia anceps biozones) that allows these beds tobe dated as Toarcian–Oxfordian (Wendt, 1969); b) an intermediateradiolarite member, consisting of red-greenish radiolarites andbedded cherts alternated by thin shales and clays with radiolarians(UAZ 8–11 biozones of Baumgartner, 1995), calcareous nannofossils(Lotharingius crucicentralis Medd, L. hauffi Grün and Zweili) andammonites from the Late Oxfordian–Early Kimmeridgian (Wendt,1969); c) an upper member of red-to-grey and greenish calcarenites,a few metres thick, (Saccocoma limestones), made of thin nodular-to-pseudonodular beds. These beds contain abundant pelagic crinoidossicles (Saccocoma sp.), echinoid fragments, brachiopods, belem-nites, benthic foraminifera (Protopeneroplis striata Weynschenk),Globochaete sp., Aptychus, radiolarians and ammonites (Divisum toBeckeri biozones) of the Late Kimmeridgian–Early Tithonian (Wendt,1969).

3.3. Lattimusa

Thin-bedded pink-to-white cherty limestones, 5–30 m-thick, richin calpionellids (Crassicolaria, Calpionella, Calpionellopsis and Calpio-nellites biozones of Alleman et al., 1971), suggesting a Late Tithonian–Early Valanginian time interval.

3.4. Greenish calcareous marls and grey calcilutite

Limestone–marl alternations with radiolarians and planktonicforaminifera (Hybla Formation). These, 30–50 m-thick, conformablyfollow the Lattimusa limestone. Based upon the occurrence ofcalcareous nannofossils (CC 2–6 and CC8 biozones of Perch-Nielsen,1985) and planktonic foraminifera (Schackoina cabri, Ticinella primula,Biticinella breggensis, Rotalipora ticinensis, and Globigerinelloidesalgerianus biozones of Caron, 1985) these deposits have been assignedto the Aptian–Albian time interval.

3.5. White and red pelagic limestones

Extremely variable in thickness (1 to 180 m), these limestonesconsist of planktonic foraminifera-bearing wackestone (AmerilloFormation). The fossil content (Rotalipora appenninica, Globotruncanaventricosa, G. aegyptica and Morozovella formosa formosa, M. arago-nensis, Truncorotaloides rohri, and Turborotalia cerroazulensis s.l.biozones of Caron (1985) and Tourmakine and Luterbacher (1985),allows these deposits to be dated as Late Cretaceous to Eocene.

4. Typical sections

4.1. The Rocca Busambra succession

Three main stratigraphic successions have been reconstructedalong the Rocca Busambra ridge (Fig. 2a): Piano Pilato (westernmostsector of the ridge), the Rocca Busambra peak and Pizzo Marabito(eastern side of the ridge), respectively. They have been identified onthe basis of their lateral facies changes and stratigraphic relationships.

The Jurassic–Cretaceous condensed succession of Rocca Busambramay overlie either the Lower Jurassic peritidal limestones, pertainingto the Inici Fm or the Upper Triassic reef deposits of the PizzoMarabito. At Piano Pilato (Fig. 3) a 15 cm-thick blackish Fe–Mn crust,formed by flat-to-undulating laminae, caps the Inici Fm. Massive,reddish-brown Bositra limestones (lowermember of the Buccheri Fm)follow the encrusted peritidal limestones of the Inici Fm. These beds, afew metres thick, consist of wackestone–packstone, with sparsedecimetre-sized dark oncoid, rich in ferromanganese oxides (Fig. 4a)and a few fragments of thick-shelled molluscs, often Mn-coated(Fig. 4b). The Saccocoma limestones (upper mb of the Buccheri Fm)paraconformably overlie the Bositra limestones and rest, in buttressunconformity, above the faulted Lower Jurassic peritidal limestones.In contrast, at Pizzo Marabito, massive Saccocoma limestones (f, inFig. 3) rest with onlap and buttress unconformity relationships abovea dolomitized Upper Triassic sponge-bearing reef boundstone,dissected by synsedimentary faults. In this region, the upper mb ofthe Buccheri Fm consists of reworked grainstone–packstone alternat-ed with pink radiolarian- and ammonite-bearing mudstone thatcontains Fe–Mn oxide-impregnated Aptychus fragments (Fig. 4g). TheLattimusa formation (g, in Fig. 3) paraconformably overlies theSaccocoma limestones at Piano Pilato as well as at Pizzo Marabito. AtPiano Pilato, the pink-to-white, thin-bedded, calpionellid-bearingwackestone (Fig. 5c) displays an upward transition to intraforma-tional breccias and conglomerates; this clastic interval seals thefaulted Inici Fm in buttress unconformity and rests in downlap, withtalus geometries, above both the Tithonian calpionellid limestonesand the underlying deposits of the Buccheri and Inici Formations. AtPizzo Marabito, moreover, the Lattimusa thin-bedded cherty and thenodular mudstone–wackestone (1–15 m-thick) show a buttressunconformity, onlapping, faulted Upper Triassic reef limestones. Thewackestone–marl alternations of the Hybla Fm (h in Fig. 3) outcrop atPizzo Marabito, where they display thick-bedded intercalations ofintraformational bioclastic (Aptychus and mollusca fragments) float-stone. Finally, Upper Cretaceous and Eocene white wackestone(Amerillo Fm, i in Fig. 3), outcropping along the whole carbonateridge, overlies the above-mentioned beds, as onlap or in buttressunconformity. Their thickness varies from 50 m, when they fill uppreviously-formed syntectonic depressions, to a few metres, whenthey form lenticular channelized deposits. At the Rocca Busambrapeak (Fig. 3), a thick body of calcareous megabreccias (j in Fig. 3) isinterlayered in the Campanian–Lower Maastrichtian interval of theAmerillo Fm. The breccia elements are rudstone–floatstone (Fig. 5g),consisting of sub-rounded cobbles and boulders, that derive from theUpper Triassic–Jurassic deposits. The tabular and/or lenticular shapedcarbonate megabreccias cover, in downlap the pelagic deposits and,laterally (towards the peak), abruptly onlap the Lower Jurassicperitidal limestones, filling shallow, channelled gullies (Fig. 6).

4.2. The Monte Balatelle succession

This succession displays (Fig. 3) Lower Jurassic grey and reddishcrinoidal grainstone (3–4 m-thick) with tabular geometry, which liesabove an erosional unconformity surface, carved into the whiteperitidal limestones of the Inici Fm (INI in Figs. 7 and 8). Darkcalcarenites, rich in crinoidal fragments, ammonites and thin-shelled,pelagic bivalves (Bositra limestones, d, in Figs. 3, 7, 8 and Fig. 4c), and





upwards, red nodular ammonite-bearing wackestone, 15 m-thick,onlap and rest, in buttress unconformity, above the faulted Inici Fm(Fig. 7). Discontinuous red-greenish, thin-bedded cherts and radi-olarites, silicized mudstone with cherty nodules and red nodularammonite-bearing wackestone (radiolarite member of the BuccheriFm), 0–8 m-thick, follow laterally and upwards (e, in Figs. 3 and 8 ).Thick basaltic rock bodies (not previously observed), consisting ofgreenish pillow lavas (Fig. 4c,d,f; and β in Figs. 7 and 8) and igneousdykes, are interlayered in the lower member of the Buccheri Fm. Thevolcanic material outcrops on the southern side of Monte Balatelle(15 m-thick) and at Cozzo Cavallo (100 m-thick), where it isunconformably covered by Saccocoma limestones (f, in Figs. 3 and8). The Jurassic succession is then capped by white marls and chertylimestones (Lattimusa, g, in Figs. 3, and 8 and Fig. 5a), 20–50 m-thick,with frequent turbiditic calcareous sandstone (Fig. 5b), conglomer-ates and calcareous breccias (2–3 m-thick, see Fig. 3). The cm-sizedelements of the breccia, consist of carbonate platform-derivedfragments, welded to form yellow calcareous marls with ammonites,belemnites and crinoidal plates. Locally, pyroclastic layers occur (τ inFig. 3). The 50–70 m-thick greenishmarl and calcilutite alternations ofthe Hybla Fm (h, in Figs. 3 and 8), show thin intercalations of basalticpillow lavas. Bioclastic (mostly crinoidal fragments, belemnites andAptychus) and intraclastic packstone–grainstone, welded in a greenishplanktonic foraminifera-bearing marlstone, frequently occur. TheAmerillo Fm (25–50 m-thick) consists of laminated wackestone–mudstone (i in Figs. 3 and 8) with, cm-thick, calcareous turbiditeintercalations, which are characterized by reworked globotruncanids,echinoids and mollusca fragments (Fig. 5h) of Late Cretaceous age.White and yellowish Eocene cherty limestones, with graded andlaminated siltstones and calcareous sandstone intercalations, para-conformably follow.

4.3. The Vicari succession

Starting from the bottom, this succession displays (Fig. 3): grey-yellowish oolitic grainstone/packstone, forming decimetre to metretabular beds, rich in volcanic fragments (vitreous, quartz, oxides,scoriae and opaque minerals) and bioclasts (benthic foraminifera,such as Protopeneroplis striata Weynschenk and Trocholina aff. alpinaLeupold, crinoids, pelecypods, echinoids and dasycladacean frag-

ments). They regularly alternate with volcanic lavas and pyroclasticlayers and grey breccias, consisting of rounded, carbonate platform-derived fragments. The magmatic bodies form repetitive sequences ofpillow lavas, hyaloclastites, zeolitized lavas and cross-laminatedtuffitic sandstones (Fig. 4e), rich in pelecypods (Trigonia hemisphaer-ica Lycett, Lima pectiniformis Schlotheim, Pinna ampla and manyothers, Trevisan, 1937) and benthic foraminifera (Mesoendothyracroatica Gusic), dating these beds to the Bajocian–Bathonian. Thisunit, 64 m-thick, pertains to the lowermember of the Buccheri Fm (d″,in Fig. 3). The radiolarite member of the Buccheri Fm does not outcrophere. The uppermost member of the Buccheri Fm (f, in Fig. 3)unconformably follows. This unit, 30 m-thick, is well exposed at LaRocca di Vicari, and consists of: a) massive, grey and white-yellowishpackstone (Saccocoma limestones, Fig. 9a) with Globochaete alpina,Globigerina oxfordiana, and Glomospira (Caflisch and Crescenti, 1969);b) thin-bedded, red-yellowish wackestone and intraclastic floatstone(“pseudonodular”) with large reworked ammonites and reef-derivedelements (Cladocoropsis mirabilis Felix), crinoids and bryozoans(Fig. 9a); c) reddish fine conglomerates, with reworked ammoniteshave a lenticular geometry and produce erosion of the underlyingstrata (Fig. 9a).

Grey-to-reddish coarse, packstone and rudstone, informally namedhere “Cladocoropsis breccia” (g′ in Fig. 9a)made up of biogenic, shallow-water carbonate elements (Figs. 9b and 5d) alternated with packstonewith reworked ammonites (Fig. 9b), 4 m-thick, unconformably follow;this unit, not previously observed, displays lenticular geometries,undulated stratification and reverse gradational structures. The fossilcontents, mostly crinoids, echinoids, pelecypod and brachiopod frag-ments, and other shallow-water bioclasts (Cladocoropsis mirabilis Felix),Aptychus sp, Protopeneroplis striata and rare ammonites, constrain thesebeds to the Late Jurassic (younger than the Kimmeridgian)–EarlyCretaceous (?).

4.4. The Roccapalumba succession

This succession, reconstructed from the classical site of Le Rocchequarry (Figs. 2a and 10), displays, starting from the bottom (Fig. 3):white and grey planar, thick-bedded, bioclastic packstone/grainstone,with rounded carbonate grains, rare quartz, volcanic minerals andoolites. The unit, 15 m-thick, pertains to the lower mb of the BuccheriFm (d″ in Figs. 3 and 10) The fossil contents consist of micropro-blematica (Shamovella “Tubiphytes” morronensis, Crescenti), benthicforaminifera (Protopeneroplis striata, Spiraloconulus giganteus Cherchiand Schroeder, Mesoendothyra croatica Gusic), dasycladacean algae(Salpingoporella donzellii Sartori and Crescenti), crinoid, echinoid andbivalve fragments, which date these beds to the Bajocian–Bathonian.These deposits have W-dipping domino-style normal faults (Fig. 10),and are sealed by a volcanoclastic layer (τ in Fig. 10), 2 m-thick,consisting of greenish tuffs with calcareous fragment inclusions andcoarse tuffitic calcarenites.

Graded intra-bioclastic grey rudstone with femic minerals andcross-laminated (ripples) packstone/grainstone (Fig. 5e,f), 8 m-thick, follow (“Dasycladacean breccia”, g″ in Figs. 3, 10, 11). Thefossil content consists of microencrustants (Koskinobullina socialisCherchi and Schroeder, Lithocodium-Bacinella), dasycladacean algae(Macroporella sp. and Pseudocymopolia cf. praturloni, Dragastan),benthic foraminifera (Trocholina spp., Charentia cuvillieri Neumann,Protopeneroplis ultragranulata Gorbatchik), coral, echinoid, crinoid

Fig. 6. Faulted massive Upper Cretaceous megabreccias (AMMm, in light green) andupward thin Upper Cretaceous–Eocene pelagic beds (AMM) that onlap and abut, inbuttress unconformity, the faulted Lower Jurassic peritidal limestones (INI; fault planesare in red, modif. From Basilone 2009).

Fig. 5. Characteristic facies and microfacies of the Cretaceous study successions. a) resedimented bioclastic packstone, with calpionellids, crinoids, Aptychus and pelagic pelecypodfragments (Lattimusa, Monte Balatelle, PPL, scale bar 1 mm); b) bioclastic and intraclastic grainstone, interlayered in the pelagic limestones of the Lattimusa (Monte Balatelle, PPL,scale bar 1 mm); c) wackestone with calpionellids and ammonites (Lattimusa, Rocca Busambra, PPL, scale bar 1 mm). d) Upper Jurassic–Lower Cretaceous coral-boundstone(“Cladocoropsis breccias”, Vicari); e) intra-bioclastic grainstone with volcanoclastic grains (v) and dasycladacean fragments (“Dasycladacean breccias”, Roccapalumba, PPL, scale bar1 mm); f) bioclastic grainstone with coated grains (top of the “Dasycladacean breccias”, Roccapalumba, PPL, scale bar 1 mm); g) rudstone–floatstone with carbonate platformelements, welded in red wackestone with planktonic foraminifera (calcareous megabreccias inserted in the Late Cretaceous pelagic deposits of the Amerillo Fm, Rocca Busambra,PPL, scale bar 1 mm); h) grainstone with oolites, bioclasts and intraclasts interlayered in the Late Cretaceous pelagic deposits of the Amerillo Fm (Monte Balatelle, PPL, scale bar1 mm).



Fig. 8. Panoramic view of the eastern side of Monte Balatelle showing E–Woriented normal faults (red lines), cutting the Lower Jurassic Inici Fm limestones (INI). The conjugate dip–slip fault system, produced an E–W oriented graben structure filled by Middle Jurassic lower Rosso ammonitico mb of the Buccheri Fm, consisting of Bositra limestones (d) andnodular limestones (d′), that onlap in buttress unconformity and rest above the faulted Inici Fm beds. Pillow lava intercalations (β) are also present. The tectonic depression is sealedby the radiolaritic member (e) and by the Saccocoma limestones (f). The calpionellid limestones (g, Lattimusa), the Hybla (h) and the Amerillo (i) Fms seal the above-mentionedstructures.

Fig. 9. Upper Jurassic succession outcropping at Vicari Castle. a) The “Cladocoropsis breccias” (g′) cover, unconformably the eroded uppermost member of the Buccheri Fm:Saccocoma limetsones (f1); wackestone with reworked ammonites and reef-derived elements (f2); fine conglomerates with erosional lower boundary (f3). b) Detail of the same site,which shows the relations of the different lithofacies forming the “Cladocoropsis breccias” unit: packstone with reworked ammonites (g′1); rudstone with large carbonate reef-derived elements (g′2).

Fig. 7. a) Large fracture set on the Inici Fm limestones (INI) filled by basaltic pillow lavas (β; Monte Balatelle). This fracture set cuts an inherited normal fault and is covered, inbuttress unconformity, by the Middle Jurassic Bositra limestones (d); b) details of the buttress unconformity.



and mollusc fragments, which restrict these beds to the Berriasian–Valanginian age. This unit, not previously described, rests uncon-formably above a ferroan oxide crust marking an erosional surfaceor, in buttress unconformity, on the previously described depositsand suggests a large gap. Grey and yellowish tufaceous sands withbioclasts (mostly echinoids, sponge spiculae, gastropods, bryozoansand bivalve fragments), and very fine black and greenish thin-bedded tuffitic shales, with bedded cherts (τ′ in Figs. 10 and 11),8 m-thick, follow. The latter, are, in turn, capped by a fewdecimetre-thick grey packstones (τ″, in Fig. 11).

Laterally, in the isolated blocks outcropping near the Le Rocchequarry, the previous deposits are replaced by Tithonian–Neocomianwhite cherty wackestone with calpionellids and radiolarians (Latti-musa), 10–15 m-thick, Late Cretaceous red and whitish marly lime-stones of the Amerillo Fm, 20 m-thick, paraconformably follow.

5. Rift-related tectonic processes and volcanism

Several tectonic and volcanic features have been observed in thestudied successions.

5.1. Synsedimentary tectonics

The main palaeotectonic features (Fig. 12) are briefly analyzedhere (attitude referred to present-day coordinates):

Lower Jurassic event. This tectonic event is documented by: a)large (mappable) WNW–ESE (presently) oriented neptuniandykes (Fig. 12a), outcropping at Rocca Busambra, mostly filledwith reddish Toarcian crinoidal limestones and Middle JurassicBositra limestones; b) E–W-trending fractures (Figs. 7 and 12a),with a maximum width of about ten metres (Monte Balatelle).These fractures, which show brecciated Inici Fm elements restingon their sides, are draped in buttress unconformity by MiddleJurassic red nodular limestones of the lower member of theBuccheri Fm; c) ENE–WSW- and WNW–ESE-trending faults(Fig. 12a), S-dipping with a small downthrow, cut the UpperTriassic reef limestones; these faults are sealed by Bositralimestones (Pizzo Marabito).Middle Jurassic event. NNE–SSW-oriented subvertical faults(Fig. 12b), with a few metres of downthrow, cut the Bajocian–

Fig. 10. Le Rocche di Roccapalumba quarry. Faulted and tilted Middle Jurassic crinoidal grainstone (d″) pertains to the lower mb of the Buccheri Fm. Bajocian volcanite intercalations(τ) are capped, with erosion, by the massive Lower Cretaceous “Dasycladacean breccias” (g″) and by grey packstone and fine tuffites (τ).

Fig. 11. Details of the previous figure, showing the buttress unconformity between the faulted deposits (crinoidal grainstone, d″) and the overlaying Lower Cretaceous“Dasycladacean breccias” (g″). Interlayered red volcaniclastic material (τ) is also evident.



Bathonian limestones, that in turn, are draped by Late Bathoniantuffites andbasalts (RoccapalumbaandVicari, Figs. 10, 11, 12band13).Upper Jurassic event. It consists of several, south dipping, almostsubvertical (60–80° steep, Fig. 12b), WNW–ESE-oriented paleo-faults (with some metres of downthrow), which cut the LowerJurassic Inici Fm deposits, as shown along the Rocca Busambraridge, especially on the western side of Piano Pilato (II in Fig. 14),and the Upper Triassic reef limestones on the easternmost Pizzo

Marabito (IV in Fig. 14). These features are either synsedimentaryfault planes or morphotectonic scarps, which are sealed by UpperJurassic Saccocoma limestone; the latter lies against the foot–wallscarp of the fault with a buttress unconformity;

J/K boundary event. Several paleotectonic features are listed here:a) ENE–WSW, WNW–ESE and E–W oriented (Fig. 12c), normalfaults, with a small downthrow, that cut the uppermost Jurassicwhite calpionellid limestones at Monte Balatelle (Figs. 8 and 12c)and Piano Pilato (Rocca Busambra). These paleofaults are drapedby Lower Cretaceous beds made of reworked Lattimusa deposits;b) NE–SW-trending dextral transtensive faults cut the lowerLattimusa deposits (Balatelle succession, Fig. 12c); c) N–S andNNE–SSW-oriented normal paleofaults (Fig. 12c), which cut theJurassic carbonate and volcanic deposits of Roccapalumba and aresealed by Berriasian–Valanginian “Dasycladacean breccias”, and inturn lie against the foot–wall scarp of the fault plane with abuttress unconformity (Figs. 10 and 11).Cretaceous events. a) WNW–ESE conjugate dip–slip fault planes (Fig.12c), cut the Jurassic substrate, giving rise tohorst andgraben features;the derived morphotectonic depressions (Rocca Busambra–PizzoNicolosi, I in Fig. 14), cut into the Lower Jurassic peritidal limestones,and are filled with a 40 m-thick package of Upper Cretaceous pelagicdeposits (Amerillo Fm); b) ENE–WSW fault planes (Fig. 12d) dissect,with a slight displacement, the Lower Jurassic peritidal limestones inthe central-western regionof theRoccaBusambra ridgeand in turnaresealed by reworked Upper Cretaceous and pelagic deposits (Fig. 6 andIII in Fig. 14). Finally, a Campanian–Maastrichtian carbonate mega-breccia wedge seals the footwall block of the fault planes anddownlaps over the older (Jurassic–Cretaceous) deposits on thehanging wall blocks (III in Fig. 14).

The mesostructural analysis indicates, for the first time, theoccurrence of high-angle faults, mostly E–WandWNW–ESE-oriented,both north and south dipping, with extensional and transtensionalmovements (Fig. 12). The analysis of the infilling and the trend of thesedimentary dykes of Rocca Busambra and Monte Kumeta (Mallarinoet al., 2002) allowed us to evaluate the N–S and NNE–SSW direction ofextension (referred to present-day coordinates).

Fig. 12. Stereographics projection of the main Jurassic–Cretaceous extensional fault inthe study areas.

Fig. 13. Pizzo Falconiere, Vicari. NNE–SSW normal fault filled by basalts (β), that in turn, unconformably cover the Middle Jurassic laminated crinoidal grainstone (d″).



Finally, the several distinguished tectonic events suggest acontinuum tectonics, during the Jurassic–Cretaceous, of an overallextensional rift-related tectonic regime.

5.2. Volcanism

Volcanic products (pillow lavas and pyroclastic flows) have beenrecognized in the Balatelle, Vicari and Roccapalumba areas. They havebeen related to different volcanic episodes:

(1) Middle Jurassic episode. In the Balatelle region, 10 m-thickellipsoidal pillow lavas (≈1 m diameter) are interlayered in theMiddle Jurassic Bositra limestones (Fig. 15). They display avitreous shell, 1 cm-thick, that suggests a submarine volcaniceruption. Locally, they are sealed by a pyroclastic layer; the latter

consists of bedded tuffs, 15 cm-thick and fine floatstone with atuffitic matrix, 25 cm-thick. The conjugate normal faults (Fig. 7),cutting the Inici Fm, have produced a graben structure, filledwithporfiric basalts, that contain abundant phenocrysts (pyroxenes,plagioclase and rare olivine). Topwards, cryptocrystalline basaltsand spherical pillow lavas with a thin vitreous shell (e.g. fissuraleruption), are present. The resulting dyke is draped by UpperJurassic Saccocoma limestones (Figs. 7 and 8).At Cozzo Cavallo sub-spherical and elliptical pillow lavas areinterlayered with Bositra limestones and draped by Upper JurassicSaccocoma limestones. The igneous rock body, 1.5 km-wide and150–200 m-thick (Fig. 14), is progressively onlappedby the Bositralimestones on its lateral slope. The local, densely packed sphericaland elliptical pillow lavas, appear as a flow that hasmoved along agentle slope (Schmincke et al, 1997). On the whole these featuressuggest the presence of a large submarine volcanic complex.In the Vicari succession, alkaline pillow lavas (Bellia et al., 1981)and subaerial volcanic products are interlayered in the Bajocian–Bathonian Pelecypod limestones of the lower member of theBuccheri Formation. The volcanic and sedimentary products areorganized inquasi-cyclic sequences. Starting fromthebottom, theyshow,: a) severalmetres of altered spherical pillow lavawith a thinvitreous shell; b) thin-bedded coarse hyaloclastites, rich incarbonate fragments, formed by the breaking down of pillows; c)aphanitic-to-porphyric massive lavas with pyroxene and plagio-clase phenocrysts and rare olivine; d) thinly laminated and gradedtuffs, with carbonate fragments, mica, magnetite and quartzcrystals; e)weakly cemented and cross-laminated greenish tuffiticsandstones, with calcareous fragments and bioclasts; f) bioclasticsandstones, bearing rounded volcanic fragments. These repetitivesequences are interpreted as the result of different volcanic eventsformed around a submarine-to-subaerial vent, adjacent to thestudy area. Pillow lavas and hyaloclastites were formed duringsubmarine conditions; the following subaerial tuffs duringemersion of the volcanic edifice (e.g. tuff cone). The presence ofvesicular lapillistones and bombs in the tuffitic layers, suggestsshallow-water-to-subaerial conditions (sursteyan activity), in-stead of subaerial lava flows. The several calcareous-tuffitic beds,with reef-derived elements, suggest the development of carbonatebuild-up, during periods of still-stand volcanic activities.At Roccapalumba, tuffs with rounded basaltic fragments, bombsand scoriae (pyroclastic flows), a few metres thick, suggestshallow-water-to-subaerial volcanic eruptions. The Vicari andRoccapalumba volcanic events appear to be all correlatable asthey are interlayered in the Bajocian sandstones.

(2) Uppermost Jurassic episode. It is documented by several metre-long, cm-wide subvertical fractures (Fig. 13), cutting the upper

Fig. 14. NNE–SSW tectonic profiles, showing the depositional setting of different areasof the Rocca Busambra ridge (modified from Basilone, 2009).

Fig. 15. Schematic cross-section along the Monte Balatelle–Cozzo Cavallo E–W alignment, showing the tectonic–stratigraphic relationships between the Jurassic Buccheri Fmdeposits and the interlayered igneous rocks. Lower Jurassic faults have been the origin of the main graben structures, filled by the Jurassic–Lower Cretaceous pelagic deposits of theBuccheri, Lattimusa and Hybla Fms.



member of the Buccheri Fm at Case Falconiere (Vicari). Thesefractures are filled with porfiric basalts, rich in pyroxenes,plagioclases, rare olivine and calcareous fragments derivingfrom the underlying beds.

(3) Lowermost Cretaceous episode. Coarse tuffitic calcareniteswith scoriae and lapillistones, thin-bedded ashes with quartz,pyroxene and micaceous minerals, as well as calcareousfragments, outcrop at Roccapalumba. These materials appearreworked in the Berriasian–Valanginian “Dasycladacean brec-cias” (Figs. 10 and 11). The vesicular lapillistones and ash layerssuggest the presence of a volcanic complex near this area,characterized by explosive activity (shallow-water-to-subaer-ial eruptions). In the calpionellid limestones (Lattimusa),outcropping at Molino Fiaccati (Vicari), large fractures, morethan 10 m-wide, are filled with well-crystallized basaltic rocks.Upwards, pillow lavas and aphanitic basalts with a thinvitreous shell follow. These products are interpreted as beingthe result of fissural eruptions, along inherited Upper Jurassicfractures and fault planes, in a submarine setting, as suggestedby the lack of tuffitic or other volcanoclastic layers.

(4) Lower Cretaceous episode. Coarse pyroclastic levels, withcalcareous fragments, scoriae and femic minerals. Theyfrequently outcrop at Monte Balatelle, where they may befound between the Valanginian calpionellid limestones of theLattimusa Fm and the Aptian–Albian marl–mudstone alterna-tions of the Hybla Fm. In the latter deposits, thin pillow lavaintercalations are also present.

6. Discussion

Based on the several stratigraphic, tectonic and volcanic features,different Jurassic–Cretaceous tectono-stratigraphic settings have beenrestored in the study sectors (Fig. 16):

a) Pelagic carbonate platform margins. They can be recognized alongthe Rocca Busambra ridge (see also Basilone, 2009). Here, fromNW to SE, a structural high, bounded by stepped margins withcondensed sequences passes to a horst and graben system and toslope areas. The latter are characterized by a scalloped upper partpassing to a base-of-slope environment. This “stepped margins”model is, moreover, well documented in other peritidal carbonateand pelagic platform domains (Bourrouilh, 1981; Hurst and Surlyk,1984; Cecca et al., 1990; Santantonio, 1993, 1994; Di Stefano et al.,2002).

b) Pre-Bajocian tectonics. During the Jurassic, the Balatelle regionwas characterized by pelagic sedimentation of “Rosso Ammoni-tico” with nodular beds and radiolarites (Buccheri Fm). Pre-Bajocian tectonics have yielded main graben structures separatedby small horst areas (Figs. 15 and 16). This main graben can beextended to include the “Marineo basin” (Catalano and D'Argenio,1982a,b) recognized in the subsurface of the adjacent region. Inthe Balatelle area, the tectonics were accompanied by importantsubmarine volcanic eruptions, as suggested by the shape andthickness of the Middle Jurassic pillow lava bodies (Figs. 15 and16b). This setting was active up to the Early Cretaceous, at leastwhen, on the western side of the Monte Balatelle region, theLattimusa pelagic deposits draped the ancient stepped margin(already recognized in the adjacent Kumeta ridge, Di Stefano et al.,2002). On the eastern side of the area, in the pelagic deposits,several clastic-carbonate materials are intermixed (Catalano et al.,1973). These clastics, derived from the dismantling and/orshedding outwards of reef-type complex deposits, developed inshallow-water areas, that we envisage in the Vicari region. Such atectonic setting is well known as it is believed to occur in bothancient and modern syn-rift systems as reported for the Jurassic of

Hungary (Galàcz et al., 1985; Galàcz, 1988), the Southern Alps(Jadoul et al., 2005) and in the Monte Kumeta “Jurassicescarpment” (Di Stefano et al., 2002, 20 km north of RoccaBusambra).

c) Vicari and Roccapalumba volcanic features. The volcanics andreworked carbonates in the Vicari and Roccapalumba regions,could have been deposited along a flank of a topographical high,probably corresponding to a submarine volcano. Volcano-sedimentary facies sequences as those seen in the Vicarisuccession were described as related to a submarine volcaniccomplex, when rising to the surface of the sea (Tazieff, 1972).In this frame, the Jurassic and Lower Cretaceous reworkedcarbonate materials, interspersed between the volcanic layers,can be related to the dismantling of shallow-water deposits thatwere capping a volcanic seamount (atoll-type, Fig. 16b and c).These stratigraphic features have also been recognized in theJurassic syn-rift successions of Turkey, where alkaline eruptiveevents are interlayered in reefal deposits (Farinacci, 2002;Farinacci and Ekmekci, 2004). The overlying Cretaceous-to-Eocene thin pelagic deposits of the Amerillo Fm are lacking ofresedimented materials (with the exception of the adjacentRocca Busambra and Monte Balatelle regions). These featuresimply that the Jurassic volcanic seamount, later drowned, wasdraped by pelagic sediments (Fig. 16d).

d) Tectonic evolution. On the whole, during the Mesozoic, the studyareas were tectonically unstable, with horst and graben structures,connected by steeped margins and facing deeper or oceanic areas.This articulate morphology of the sea floor is confirmed bydifferent Jurassic successions, characterized by condensed depos-its in the structural highs and thick pelagic successions in thestructural low. The tectonic instability of the area is confirmed,also, by the presence of large volcanic products, that appear strictlyconnected with a crustal extension; their alkaline-to-tholeiticevolving chemistry has been explained by an upwards migratingmagma at the beginning of the spreading process (Lucido et al.,1978; Bellia et al., 1981).Similar tectono-stratigraphic and volcanic settings have beenalready described for other Mediterranean regions, where large-scale palinspastic restorations have provided several models ofpassive continental margin evolution. For example, in Greece, thepassive continental margin of the Pindos Ocean is characterized byan irregular sea floor with intraplatform basins, structural highsand volcanic seamounts capped by carbonates, flooring a transi-tional crust (Degnan and Robertson, 1998; Robertson, 2006).This is consistent with the subsidence history and the style offaulting in the western Mediterranean, where the Triassic–Jurassicrifting between Africa and Europe occurred in an east–westsinistral transtensional kinematic framework (Dewey et al., 1989;Olivet, 1996; Catalano et al., 2001).Similar results have been obtained, also, from the Jurassic–EarlyCretaceous successions of the North African continental margin,outcropping in north and south Tunisia (Bouaziz et al., 2002 andreference therein), where a N–S extension, associated with E–W-trending subsiding basins, is observed.Rifting in the Himalayas and Oman gave rise to a proximal-to-distalramp geometry with scatted seamounts (continental fragments andatolls) located adjacent to the rifted margin (Reuber et al., 1987;Bechennec et al., 1990; Cooper, 1990; Reuber et al., 1992; Robertson,1998, 2007).

e) Regional tectonic and paleogeographic framework. The palinspas-tic restoration of the tectonic wedge in western Sicily (see Fig. 2b)suggests that the deep-water carbonate domains were originallylocated in a more internal (present-day north) palaeogeographicsetting with respect to the carbonate platform, during Mesozoictimes. The study regions are part of the higher carbonate platformunit (see Fig. 2b) indicating the original location in a more distal



Fig. 16. Essay of paleogeographic restoration of the study sectors of the Trapanese domain during the Mesozoic.



sector of the original carbonate platform, nearer to the deep-waterdomains.The reconstruction of Tethys (Ziegler, 1988) suggests that theIonian is part of the western Tethys branch. From recent data(Catalano et al., 1991, 2001; Stampfli et al., 2001; Finetti et al.,2005; Stampfli, 2005) the Ionian Sea is confined to between thePelagian and Apulian platforms. The present-day SE–NW- trend-ing orientation of the Ionian Ocean and the Sicilian and AppennineMesozoic palaeogeography suggest that the oceanic crust couldcontinue to the west-northwest (Catalano et al., 2001).According to large-scale palinspastic restorations of the JurassicTethyan margins (Ziegler, 1988; Dercourt et al., 2000; Stampfli,2005) and the location of the Ionian Ocean (Catalano et al., 2001),the restored paleotectonic setting discussed here fits well into aprofile of a rifted continental margin near or bordering the thinnedcrust deep-water domains not far away from the supposed oceanicareas (Fig. 17).

7. Conclusions

Stratigraphy, facies analysis, volcanic rock reconnaissance andstructural data collected in the Mesozoic shallow-water-to-pelagiccarbonate sequences of Rocca Busambra, Balatelle and Vicari–Roccapalumba in central-western Sicily allow us to distinguish severalnew features, suggesting the occurrence of rifting-related tectonicsand volcanism.

A new tectono-stratigraphic setting of the study areas has beenreconstructed for the Jurassic–Cretaceous Trapanese successions. TheBalatelle region suggests a horst and graben setting; it was the site of alarge submarine volcanic eruption that yielded thick pillow lavabodies and a large amount of resedimented materials and appearsbordered by two main structural highs: whereas the Rocca Busambrais characterized by condensed carbonate Jurassic deposits capping afaulted Triassic–Lower Jurassic carbonate platform substrate laterdeveloped into a stepped fault margin (Late Jurassic). This regionevolved, during the Cretaceous, into a horst and graben system withdepositional slope areas. Also, the eastward located Vicari andRoccapalumba sites, carry evidence of a morphostructural high,where a submarine-to-subaerial volcano (with surge volcanic erup-tions) evolved, during the Late Jurassic–Early Cretaceous interval, intoa carbonate build-up such as an atoll-type or small reef-carbonateshelf.

The morphological and petrographical characteristics of theigneous products (observed for the first time) suggest a submarine

and partly subaerial (e.g. surtseyan phreatomagmatic eruptions)volcanism, related to intraplate magmatic activity.

The Jurassic–Cretaceous synsedimentary tectonics (extensionaland transtensional faults) and the volcanic products (basalts andvolcanoclastic materials) are related and partly coeval with similaroccurrences during the Tethyan rifting.

The present restoration is in agreement with the model of a riftedTriassic–Jurassic carbonate platform, attached to the African craton,and irregularly bordered by a widespread basinal domain. Thetectono-stratigraphic setting suggests that the Jurassic–Cretaceoustectonic events gave rise to a ramp geometry with scattered horst(seamounts and atolls) and graben connected by steeped margins.The rifting-related tectonic and volcanic processes, during theMesozoic, suggest a crustal tectonic instability, for the study areasthat was relatively near to deeper water or oceanic areas.

Acknowledgments

This research work was supported by grants “PRIN” 2006 andMiur(ex 60%) 2005 (resp. Prof. R. Catalano). The authors are grateful toProf. A. Robertson and Prof. B. D'Argenio for their useful commentsand suggestions for the manuscript. We thank Prof. M. Bennett for hisgeneral comments. Special thanks are due to Prof. R Catalano for hissuggestions for the manuscript.

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Mesozoic tectonics and volcanism of Tethyan rifted continental margins in western Sicily

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