Late Neogene to Quaternary contractional structures in Crete (Greece)

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<ul><li><p>l s</p><p>, Itataly</p><p>ctogeaitsr coenSSassot-of</p><p>onic evfront</p><p>ecadesLe Pic88; Tho05; Ko</p><p>Tectonophysics 483 (2010) 203213</p><p>Contents lists available at ScienceDirect</p><p>Tectonop</p><p>.e lissues are still open, there is a broad agreement that the tectonicevolution of the island has been strictly related to the progressiveAfricaEurasia convergence that caused rstly the subduction of thePindos oceanic domain, afterwards the continental collision with theAdria microplate and nally the present northward-dipping subduc-tion of the eastern Mediterranean oceanic domain. The overallarchitecture of the island is characterized by a pile of thrust-nappescommonly grouped in two major structural elements separated by a</p><p>Cycladic zone), has been related tomajor exhumation processes givingrise to core-complex geometries (Lister et al., 1984; Fassoulas et al.,1994; Gautier et al., 1999; Ring et al., 2001). Accordingly, in the islandof Crete, the exhumation of the HP rocks of the lower structuralelement was thus mainly accommodated by a major low-angleextensional detachment (the Cretan detachment) that was respon-sible for the crustal thinning of the southern Aegean (Fassoulas et al.,1994; Jolivet et al., 1996, 2003; Fassoulas, 1999; Ring and Reischmann,major shear zone (e.g. Seidel et al., 1982; Fasset al., 1996; Chatzaras et al., 2006). The uincludes, from top to bottom, broken formatiowith ophiolites (Vatos and Arvi nappes), crystnappe) and pelagic and platform carbonates</p><p> Corresponding author.E-mail address: tortoric@unict.it (L. Tortorici).</p><p>0040-1951/$ see front matter 2009 Elsevier B.V. Adoi:10.1016/j.tecto.2009.05.020kkalas et al., 2006; Brunnce in the geodynamicough debates on several</p><p>Seidel, 1991, 1993; Jolivet et al., 1996; Thomson et al., 1998). The shearzone bounding upwards the HP rock-units of the island of Crete, aswell as that occurring in the surroundings of the Aegean domain (e.g.and Faccenna, 2008) because of its signicaevolution of the eastern Mediterranean. Alth1. Introduction</p><p>The Late TertiaryQuaternary tectCrete, that presently is located at thebeen investigated since several d(Aubouin et al., 1976; Angelier, 1979;Hall et al., 1984; Meulenkamp et al., 19et al., 2003; van Hinsbergen et al., 20diffuse normal faulting. While the contractional event was likely due to a stronger coupling along the overallsubduction system, the onset of the new extensional stress conditions was probably related to a suddensouthwards jump of the basal detachment along the lithospheric African subduction that caused a generalstress release in the uppermost crust.</p><p> 2009 Elsevier B.V. All rights reserved.</p><p>olution of the island ofof the Hellenic Arc, hasby many researchers</p><p>hon and Angelier, 1979;mson et al., 1999; Jolivet</p><p>Tripolitsa units, respectively (Bonneau, 1984; Hall et al., 1984). Thelower element, that forms the backbone of the island, consists of aseries of thrust sheets involving the neritic to pelagic carbonatesequences of the Plattenkalk unit and the low-grade metamorphicbasement rocks of the Phyllite-quartzite nappe (Greiling, 1982;Bonneau, 1984; Hall et al., 1984), both affected by a Late Oligoceneto Early Miocene HP/LT metamorphism (Seidel et al., 1982; Theye andGreece extensional regime that was resumed in the island only during Pleistocene when the region was affected by</p><p>Crete intervening between the EarlyMiddle Miocene exhumation phase and the still active upper crustalFoldsNeogene</p><p>a southwards migrating ouand new ones. The new data emphasize the importance and the extent of this contractional eventLate Neogene to Quaternary contractiona</p><p>L. Tortorici a,, R. Caputo b, C. Monaco a</p><p>a Dipartimento di Scienze Geologiche, University of Catania, Corso Italia 55, 95129 Cataniab Dipartimento di Scienze della Terra, University of Ferrara, Via Saragat 1, 44100 Ferrara, I</p><p>a b s t r a c ta r t i c l e i n f o</p><p>Article history:Received 20 November 2008Received in revised form 16 April 2009Accepted 20 May 2009Available online 29 May 2009</p><p>Keywords:Thrust tectonics</p><p>Based on geological and tecentral Crete, southern AeNeogeneQuaternary depostogether with diffuse minosedimentary basins documcharacterized by an NNWcontractional event(s) was</p><p>j ourna l homepage: wwwoulas et al., 1994; Jolivetpper structural elementns andmelange terranesalline rocks (Asteroussiaforming the Pindos and</p><p>ll rights reserved.tructures in Crete (Greece)</p><p>ly</p><p>nic investigations carried out along an NS coast-to-coast transect acrossn (Greece), new meso- and macro-structural data mainly collected fromare presented and discussed. The occurrence of large-scale folds and thrustsntractional structures, as well as the overall geometry of the fault-boundedt the persistence of a TortonianEarly Pleistocene contractional regime,E to NNESSW shortening direction and affecting the upper crust. Thisciated with the ongoing Hellenic subduction and caused the development of-sequence thrust system consisting of both reactivated inherited structures</p><p>hysics</p><p>sev ie r.com/ locate / tecto2002; van Hinsbergen et al., 2005), causing the denudation of thelower nappe pile. The amount of the cumulative displacementinferred for the Cretan detachment strictly depends on the assumedgeodynamic models ranging from about 100 km (Ring et al., 2001;Ring and Reischmann, 2002) to some tens of kilometers (e.g. XypoliasandDoutsos, 2000) and it is still debated in the literature (e.g. Chatzaraset al., 2006). Following these models, the Cretan detachment wouldrepresent the result of the gravitational collapse of the orogenic wedge</p></li><li><p>204 L. Tortorici et al. / Tectonophysics 483 (2010) 203213developed because of the NS directed back-arc extension related tothe continuous southward retreat of the Hellenic subduction zone(Fassoulas et al., 1994; Jolivet et al., 1996; Fassoulas, 1999; Gautieret al., 1999; van Hinsbergen et al., 2005). Alternative models favourthe hypothesis that the Cretan detachment would represent theupper boundary of an extruding wedge developed above the Hellenicsubduction zone during the AfricaEurope convergent processes thatinvolved both oceanic domains and continental terranes belonging tothe fragmented margin of the Adria block (Xypolias and Doutsos,2000; Ring et al., 2007 and references within; Brun and Faccenna,2008). In this case, the consequent exhumation of the HP rocks in theextruded wedge, which was accompanied by important erosion rates,would be related to vertical ductile thinning completely driven bybuoyancy forces (Ring et al., 1999; Thomson et al., 1999) or to crustalduplexing producing a thrust-related sub-horizontal penetrativefoliation developed by the combination of simple and superposedpure-shear deformation (Xypolias and Doutsos, 2000; Ring andKassem, 2007). However, the rapid exhumation of the Cretan rocks iswell documented by ssion-track thermochronology data, whichshow that the Phyllitequartzite unit was uplifted from its maximumdepth of burial (3035 km), occurred between 24 and 19 Ma andcaused by the orogenic nappes stacking, to less than 10 km depthbefore ca. 17 Ma (Thomson et al., 1998, 1999; Brix et al., 2002). On theother hand, structural data show that the deformation progressivelyevolved from a ductile behaviour to a brittle one. It is also commonlysuggested that the remaining 10 km of uplift to bring rocks to thesurface was caused by an extensional regime that was active in theregion fromMiddle Miocene (i.e. post 17 Ma) to present. According tothese models, the normal displacements characterizing the Cretandetachment constrained the deformation history of the island sincethe Middle Miocene causing the development of the NeogeneQuaternary basins inside mainly EW-trending large-scale grabenand/or semi-graben developed on the hanging-wall of the Cretandetachment (Angelier et al., 1982; Fortuin and Peters, 1984;Meulenkamp et al., 1994; ten Veen and Postma, 1999; Ring et al.,2007; van Hinsbergen and Meulenkamp, 2006; Seidel et al., 2007,2008; van Hinsbergen et al., 2008). In this view, the contractionalstructures (thrust faults and folds) affecting the MiddleLateMiocenePliocene sediments of central Crete have been interpretedas local structures related to minor tectonic events (Angelier, 1976,1979; Mercier et al., 1987; Meulenkamp et al., 1988; Fassoulas et al.,1994; Fassoulas, 1999; ten Veen and Postma, 1999; van Hinsbergenand Meulenkamp, 2006). In general, the above mentioned authorsunderestimate the importance of these eld evidences commonlyadvocating the occurrence of short-lived secondary tectonic pulsesand/or local minor-order tectonic stress elds and/or transpressionalregimes. From a geodynamic point of view, the Neogene contractionalstructures of Crete have been, in fact, interpreted as induced bygravitational processes (Meulenkamp et al., 1988), by the westwardextrusion of the Turkish plate (Fassoulas, 1999) or by the activity ofroughly EW oriented left-lateral shear-zones characterizing theeastern sector of the Hellenic Arc (ten Veen and Postma, 1999),among other models.</p><p>Conversely, at the end of the extrusion process (after 19 Ma) themajor tectonic boundaries of the entire nappe-stack, including theCretan detachment, were affected by contractional deformationsdeveloped in semi-brittle to brittle conditions that formed a large-scale southward-migrating fold and thrust system (Chatzaras et al.,2006). The thrust system, that in central Crete involves theSerravallian sediments, was accompanied by the growth of largeantiformal structures affecting the lower structural element of Cretealso causing the development of the Neogene basins (Chatzaras et al.,2006).</p><p>In this paper, we present a structural analysis carried out on the LateNeogeneQuaternary deposits croppingout along anNS coast-to-coast</p><p>20 km-wide transect across the central sector of the island of Crete. Thecollected data regard the geometry and kinematics of the major andminor tectonic features from the outcrop to the basin-scale. The resultsof ourworks provide newdetailed information on the structural patternalonga regional transect of central Crete, documenting theoccurrenceofa Late MioceneQuaternary contractional regime and suggesting apossible alternative to the previously proposed models on the tectonicevolution of this region.</p><p>2. Geological framework</p><p>In central Crete the structures affecting the Upper MioceneLowerPleistocene sediments have been investigated along a transect thatextends for about 35 km from the Cretan Sea, to the North, to theLibyan Sea, to the South (Fig. 1). In this area, the Upper MioceneLower Pleistocene sedimentary sequences are exposed along themainvalleys at a maximum altitude of about 650 m representing WNWESE trending narrow corridors entrenching themajormountain ridgesof the region (Fig. 1). At a larger scale, these mountain ridges show anoverall south-facing convexity (inset a in Fig. 1) and mainly consist ofcarbonate rocks belonging to both the lower and upper structuralunits.</p><p>In the northern sector of the transect, the major mountain ridgesare the Talea Ori and the Psiloritis mountains with elevations up toabout 1100 m and 2500 m, respectively. They represent tectonicwindows mainly composed of carbonate sequences of the Plattenkalkunit. In the southern part of the transect, the major ridges are indeedrepresented by the about 1800 m-high Kedros and the 1200 m-highAssideroto mountains where the carbonate rocks of the Pindos unitare exposed (Fig. 1).</p><p>The UpperMioceneLower Pleistocene deposits outcropping in thestudy area have been grouped in four major lithostratigraphic unitsranging in age from the Late Tortonian to the Early Pleistocene (vanHinsbergen and Meulenkamp, 2006 and references therein). The baseof this sedimentary succession consists of Tortonian conglomeratesand coarse-grained sands grading upwards to a sequence of clay andsandy-clay with alternating turbiditic sandstones. These coarse-grained deposits belong to the Tefelion Group (van Hinsbergen andMeulenkamp, 2006) and unconformably overlie the different Alpinetectonic units. In stratigraphic continuity are the sediments of theVrysses Group that consist of Tortonian to Messinian (van Hinsbergenand Meulenkamp, 2006) calcarenites, bio-calcarenites and whitishmarls followed in places by the Lower Pliocene marls and marly claysof the Finikia Group (van Hinsbergen and Meulenkamp, 2006). Themost recent deposits of this succession are represented by the MiddlePlioceneLower Pleistocene (ten Veen and Kleinspehn, 2003) AgiaGalini Group consisting of conglomerates and coarse-grained sandsthat crop out in the southernmost part of the study area, where theyunconformably overlie the Finikia Group sediments and the upper-most tectonic units of the orogenic belt (Fig. 1).</p><p>3. Structural features</p><p>The geological mapping of the investigated sector has been carriedout by particularly focusing on all structural and tectonic featuresaffecting the NeogeneQuaternary deposits outcropping within the20 km-wide coast-to-coast transect (Fig. 1). For the sake of clarity, wedescribe separately into four zones, from north to south, the severalcollected data.</p><p>3.1. Zone A</p><p>In the northern part of the transect, along the corridor separatingthe Talea Ori ridge from the northern slope of the Psiloritis mountainrange (Fig. 1), the Upper Miocene sediments of the Perama Basin,mainly represented by the Vrysses Group calcarenites and marls, form</p><p>a regional-scale wide synform (Meulenkamp et al.; 1988) bounded to</p></li><li><p>Fig. 1. Structural sketch map of central Crete. Inset (a) shows the topgraphic pattern of the study area.</p><p>205L. Tortorici et al. / Tectonophysics 483 (2010) 203213</p></li><li><p>the north by the frontal imbricate thrust sheets that extend all along ofthe Talea Ori mountain front (Hall and Audley Charles, 1983;Chatzaras et al.; 2006). The imbricate thrust system disrupts andpartly duplicates the tectonic units forming the Talea Ori ridge,showing a clear out-of-sequence evolution with respect to the majordeformational event that caused the nappe stacking. The majorstructure represented by the Mylopotamos, Anogia and Psiloritisthrust faults (MTF, ATF and PTF in Fig. 1) and described in detail byChatzaras et al. (2006) have been interpreted as a complex thrust-propagation fold system associated, few kilometres east of theinvestigated area, with a footwall syncline cored by Serravalliandeposits (Chatzaras et al., 2006), thus implying a MiddleLateMiocene age for the Talea Ori thrust propagation. Within theinvestigated transect, the regional-scale syncline (Meulenkampet al., 1988) largely coincides with the Perama Basin, which is mainlyrepresented by the Vrysses Group sediments. On the southern borderof this major synform, the Messinian sediments progressively onlapthe northern limb of the Psiloritis antiform showing a typical stratalconvergence geometry (Fig. 2a). According to natural examples andmodels on the geometry of growth strata developing along forelandbasin margins (Rani andMercier, 2002), the Vrysses Group sequencelikely represents the syntectonic deposition occurring at th...</p></li></ul>

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