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Metamorphic evolution of the Saka Unit (Central Pontides, Northern Turkey): new implications for the Mesozoic convergence-related processes in the Intra-Pontide suture zone
Get PDFIn Northern Turkey, the Intra-Pontide suture (IPS) zone represents an east-west trending belt of deformed and/or metamorphic rocks bounded by the Istanbul-Zonguldak Terrane (IZ) to the north and the Sakarya Composite Terrane (SK) to the south (e.g. Göncüoğlu et al., 1997). Despite its importance for the geodynamics reconstructions of the Black Sea and Eastern Mediterranean areas during the Mesozoic, the IPS zone has been poorly investigated; only recently the role of its metamorphic units during the syn-collisional evolution was explored (Marroni et al., 2014; Frassi et al., 2016; 2017)
In order to provide new insights on the Mesozoic-Tertiary geodynamic reconstruction of the southern margin of the Laurasia, we present new data from the Saka Unit from the eastern portion of the IPS. Using a multidisciplinary approach that includes lithological, structural, metamorphic and petrographic investigations, we constrained the P-T-t path during the Mesozoic subduction and consequent exhumation and accretion to Laurasia. Following the determination of mesostructures, we analysed a series of samples of metabasite and metapelite. Mineral chemistry of phases at equilibrium in the pervasive S2 foliation was determined, and PT determinations were performed through pseudosection calculation of three samples. PT conditions are within the epidote-amphibolite facies, with pressures of 1.2 ± 0.15 GPa and Temperatures 600 ± 50 °C, thus higher than those determined previously, suggesting that S2 could be a composite foliation where a progressive evolution acquired during onset of exhumation was recorded. A comparison with the PT evolutions of the nearby Daday and Domuz-Dag units, shows that they record lower T at D2 at different ages, and that the pre-D2 conditions, when they are preserved, are different in the three units.
References
Frassi C., Göncüoğlu M.C., Marroni M., Pandolfi L., Ruffini L. Ellero A., Ottria G. & Sayit K. 2016. The Intra-Pontide Suture Zone in the Tosya-Kastamonu area, Northern Turkey. J. of Maps. 12, 211-219
Frassi, C, Marroni, M., Pandolfi, L., Göncüoğlu, M. C., Ellero, A., Ottria, G., Sayit, K., McDonald, C.S., Balestrieri, M.L. & Malasoma, A. 2018. Burial and exhumation history of the Daday Unit (Central Pontides, Turkey): implications for the closure of the Intra-Pontide oceanic basin. Geol. Mag., 155, 356-376.
Göncüoğlu, M. C., Marroni, M., Sayit, K., Tekin, U. K., Ottria, G., Pandolfi, L. & Ellero, A., 2012. The Ayli Dag ophiolite sequence (central-northern Turkey): A fragment of middle Jurassic oceanic lithosphere within the Intra-Pontide suture zone. Ofioliti, 37, 77–91.
Marroni, M., Frassi, C., Göncüoğlu, C. M., Di Vincenzo, G., Pandolfi, L., Rebay, G., Ellero, A. & Ottria, G. 2014. Late Jurassic amphibolite-facies metamorphism in the Intra-Pontide Suture Zone (Turkey): an eastward extension of the Vardar Ocean from the Balkans into Anatolia? J. Geol. Soc., 171, 605–608
Superimposed brittle structures in the Late orogenic extension of the Alpi Apuane (Northern Apennine, Italy)
No full textFault tectonics of the Tuscan Nappe in the eastern sector of the Apuan Alps (Italy)
Get PDFWe present the geological-structural map of the Tuscan Nappe exposed on the eastern border of the Apuan Alps metamorphic dome (Tuscany, Italy). The 1:6,500 scaled Main Map covers an area of about 10 km(2). It contains the first detailed overview of the fault tectonics affecting the Tuscan Nappe during the exhumation and uplift of the Tuscan Metamorphic Units. We documented a polyphase fault tectonics that initially produced low-angle extensional faults and later high-angle faults. The latter started within a transtensional tectonic regime that produced left-lateral strike-slip faults. Lately a pure extensional tensor, indicating a switch of the maximum compression sigma 1 axis from sub-horizontal to sub-vertical, produced faults with a dominant dip-slip component. In our reconstruction the lateral thickness variations documented in several formations of the Tuscan Nappe is mainly controlled by tectonics and not by stratigraphy, as previously suggested
Note illustrative del Foglio 196 "Cabella Ligure" della Carta Geologica d'Italia in scala 1:50.000,
No full textFoglio 196 "Cabella Ligure" della Carta Geologica d'Italia in scala 1:50.000,
No full textCarta Geologica d'Italia alla scala 1:50.00
From brittle exhumation to morpho-neotectonics and gravitational slope movements in the Northern Apennine (Italy): examples from the Alpi Apuane
No full textLe unità Liguri e Subliguri delle Colline del Candia (Alpi Apuane): litostratigrafia ed assetto tettonico
No full textThe Liguride and Subliguride units of the Candia Hills (Apuan Alps): lithostratigraphy and tectonic setting. A detailed field mapping (scale 1:5000) of the area located at the west side of the Apuan Alps (Candia Hills, Massa-Carrara province) has been carried on. The lithostratigraphic features and new findings of calcareous Nannofossils from the units outcropping in this area are reported.
The Candia Hills area represents an interesting sector belonging to the Northern Apennine where ligurian (Ottone Unit; Bertotti et al., 1986; Elter et al., 1991, Zanzucchi et al., 1993; Elter et al., in stampa), subligurian (Canetolo and Sanguineto-Marra units; Plesi, 1974; Labaume, 1992, Elter et al., in stampa; Pagani e Zanzucchi, 1970) and non-metamorphic tuscan unit (Tuscan Nappe), overriding the Apuan Metamorphic Complex, are exposed. A good knowledge of this sector could help to understand the complex miocenic tectonic events that led to Apuan Alps exumation (Carmignani et al., 1980; Coli, 1989; Carmignani e Kligfield, 1990).
A tectonic stack of units belonging to the liguride and subliguride domains overlies the Macigno Formation of the Tuscan Nappe.
The sequence of the Ottone Unit consists of thick calcareous turbidites with minor intercalations of ophiolite-bearing polimict pebbly-sandstones and -mudstones.
The Canetolo Unit consists of the Argille and calcari Formation (Early-Middle Eocene) characterized by two lithostratigraphic units ("shaly-calcareous" and "calcareous") whose relationships are connected to an early folding phase.
Between Canetolo Unit and Tuscan Nappe a non-continuous level of silty-marlstones has been recognized; the calcareous Nannofossils assemblage seems indicate a late Oligocene age. This unit has been here called "Mt.Olivero formation" and it can be probably referred to the subliguride domain (Sanguineto and Marra units of the Northern Apennines; Plesi, 1974; Labaume, 1992, Elter et al., in stampa; Pagani e Zanzucchi, 1970; Cerrina Feroni et al., 1990).
Near Case Lazzoni the contact between the Canetolo Unit and the overlying Ottone Unit is characterized by the presence of two tectonic slides; the first tectonic slide is made up of ophiolite-bearing pebbly-mudstones belonging to the Ottone Unit sequence. The second one is represented by medium- to thick-bedded siliciclastic arenites; the meaning of these arenites, still doubtful, would be clarified in other sectors of the Apuan Alps where this lithostratigraphic unit probably crops out.
Along the Candia Hills traverse the tectonic setting is characterized by the hinge zone of a N140 trending wide antiform overturned to SW ("Tyrrenian vergence"); this "post-nappe" structure can be considered the SE longitudinal extension of the Castelpoggio-Ortonovo antiform that has been described northward the study area (Cerrina Feroni et al., 1995).
Key words: Liguride units, Subliguride units, Apuan Alps, lithostratigraphy
Note Illustrative del Foglio 217 Neviano degli Arduini della Carta Geologica d'Italia a scala 1: 50.000
No full textDeformations at shallow structural levels: the example of the eastern sector of the Tertiary Piedmont Basin (Northern Apennines)
No full textPolyphase deformation in sedimentary basins: the case of the eastern sector of the Tertiary Piedmont Basin
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