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Nota preliminare su un intervallo sedimentario all’interno del ciclo vulcanico calcalcalino dell’Ordoviciano medio della Sardegna SE: la Formazione di Su Muzzioni
No full textGEOLOGY AND STRUCTURAL SETTING OF THE LOWER FLUMENDOSA VALLEY. GUIDE BOOK TO FIELD TRIP SESSION: "PALYNOLOGICAL RESEARCH IN THE SARDINIAN BASEMENT"
No full textForeland- and hinterland-verging structures in fold-and-thrust belt: an example from the Variscan foreland of Sardinia
No full textIn the Variscan foreland of SW-Sardinia
(Western Mediterranean sea), close to the leading edge of
the nappe zone, nappe emplacement caused folding and
repetition of stratigraphic successions, km-scale offset of
stratigraphic boundaries and an extensive brittle-ductile
shear zone. Thrusts assumed a significant role, accommodating
a progressive change of shortening direction and
forming complicated thrust triangle zones. During thrust
emplacement of the nappes, strong penetrative deformation
affected rocks beneath the basal thrust of the nappe stack
and produced coeval structures with both foreland-directed
and hinterland-directed (backthrusting) shear sense. Crosscutting
and overprinting relationships clearly show that the
shortening direction changed progressively from N–S to E–
W, producing in sequence: (1) E–W trending open folds
contemporaneous with early nappe emplacement in the
nearby nappe zone; (2) recumbent, quasi-isoclinal folds
with axial plane foliation and widespread, ‘‘top-towardsthe-
SW’’, penetrative shearing; (3) N–S trending folds with
axial plane foliation, contemporaneous with late nappe
emplacement; (4) backthrusts and related asymmetrical
folds developed during the final stages of shortening,
postdating foreland-verging structures. Structures at (3)
and (4) occurred during the same tectonic transport ‘‘toptowards-
the-E’’ of the nappe zone over the foreland. The
several generations of folds, thrusts, and foliations with
different orientations developed, result in a complex finite
structural architecture, not completely explicable by the
theoretical model proposed up to date
DEFORMATIONAL FEATURES OF CRYSTAL-RICH RHYOLITIC LAVA FLOWS FROM S. PIETRO ISLAND (ITALY)
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Outline of the Variscan basement of Sardinia
Full text linkIn Sardinia a quasi-complete section of the southern branch of the Variscan orogenic belt crops out, characterized by non-metamorphosed to high-grade rocks, whose age ranges from Early Cambrian to Early Carboniferous, and that are involved in a complex polyphase deformation. The main result of the Variscan orogeny in Sardinia is a tectono-metamorphic partition with, from north to south: an Inner Zone, with medium to high grade metamorphism, thrusted over a Nappe Zone, with green schist metamorphism that overthrusted a Foreland Zone affected by very low grade regional metamorphism. The pre-Variscan succession is well exposed in the Foreland and Nappe zones where four main synthemes can be recognized: i) a Lower Cambrian to Lower Ordovician terrigenous and carbonatic succession deposited in the Gondwana passive margin, sealed by an angular unconformity related to the Sardic Phase, ii) a Middle-Upper Ordovician magmatic complex, both intrusive and effusive, probably related to an Andean-type plate convergence, iii) a terrigenous to carbonatic succession from Late Ordovician to Early Carboniferous, again related to a passive margin evolution; iv) finally a flyschoid Culm-like succession accredited to Early Carboniferous
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