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The Sardic Phase: field evidence of Ordovician tectonics in SE Sardinia, Italy

Published online by Cambridge University Press:  14 September 2017

FABRIZIO COCCO  and
ANTONIO FUNEDDA
FABRIZIO COCCO
Affiliation:
Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari, via Trentino 51, 09127, Cagliari, Italy
ANTONIO FUNEDDA*
Affiliation:
Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari, via Trentino 51, 09127, Cagliari, Italy
*
*Author for correspondence: afunedda@unica.it
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Abstract

Detailed geological mapping, field observations and structural analyses demonstrate that Early Ordovician (‘Sardic’) deformation occurred in the early Palaeozoic successions that are now incorporated in the Variscan Nappe zone of SE Sardinia. This deformation is represented by folds that formed at a shallow depth, lack a significant syn-folding axial planar foliation, and do not affect the overlying Late Ordovician – Devonian sedimentary sequence. These deformation features can be related to the development of the Sardic Unconformity and to calc-alkaline volcanism in several now-scattered terranes of Ordovician northern Gondwana. This reflects a convergent geodynamic setting that in the study sector appears to have failed to reach a continental collisional end-stage. Associating the structural data from this study with those of several published research studies, a preliminary evaluation about which tectonic setting could better fit is proposed. These conditions affected the eastern side of the northern Gondwana margin more or less contemporaneously with the opening of the Rhéic Ocean and the closure of the Qaidam Ocean, before the amalgamation of the Hunia terranes.

Keywords

Gondwana tectonicsstructural analysisQaidam OceanRhéic OceanEarly Ordovician
Type
Original Articles
Information
Geological Magazine , Volume 156 , Issue 1 , January 2019 , pp. 25 - 38
Copyright
Copyright © Cambridge University Press 2017 

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