The Calabria-Peloritani arc is an intriguing segment of the Apenninic-Maghrebic Chain, formed unlike the rest of the chain by several thrust sheets involving the crystalline basement. It is inserted in the zone of maximum distorsion of the orogenic system. According to the most recent interpretation (BONARDI et al., 1980) two sectors, North and South of the Soverato-Valle del Mesima alignment, can be distinguished in the arc. They arc characterized by rather a different Alpine history. The present paper is an attempt to outline the evolution of the Northern sector by a semiquantitative palyn- spastic restoration of the main stages of the Alpine cycle. Among the proposed explanatory models the one considering the arc as a fragment of the Europe-verging Alpine chain overthrust upon the Africa-verging Apenninic chain was assumed for the only sector of interest as the best fitting the analytical data. However it was necessary to intro- duce some modifications in the model as previously defined and to propose a solution, even if hypo- thetical, to many unsolved problems. The history described can he summarized as follow: after an abortive rifting in the Middle Triassic, a progressive crustal extension, culminating in a true rifting in the Jurassic, individuated different palaeogeographic realms on the future African continental margin. At the opening of the Central Tethys, that in the tract of interest is supposed to have not reached a width more than some hundreds of Kms, a total width of 250 kms is evaluated for the portion of the African continental margin presently represented in the Calabria structure. It includes an Auslroalpine- Insubric domain and the inner border of the Apen- ninic domain. The problem of the beginning of the compression is discussed and in its first stage a contemporaneous subduction of both European and African plates is assumed as the more in agreement with the probable piling-up order of the nappes. This resulted in a consumption of oceanic and African continental lithosphere and in the build up of a chain (Eo-aipine) overturned toward an European foreland and formed by wedges of oceanic and flakes both of oceanic and of Austroalpine material. During the build up of the chain (Cretaceous-Paleogene) an early flysch basin (Cilento-Sicilide basin) individualized by laceration of a zone of crustal weackness possibly extending northward of the given area and between the "Insubric" and the Apenninic domains. After the collision of the two continents the compression continued by subduction of the African continental lithosphere alone and all the nappes were wedges verging toward an African foreland. A fragment of the Eo-alpine chain overthrust the "Insubric" domain that was progressively interested by deformation. In the Early Miocene the Eo- alpine building and the "Insubric" nappes overthrust as an unique tectonic element the inner border of the Apenninic domain. Further almost passive transport during the build up of the Apenninic chain, a partial disrup- tion by the opening of Tyrrhenian sea and a block faulting led to the present day setting. The palynspastic restoration gives also a rough evaluation of the crustal shortage in about 1/2 of the original width during the Europe-verging and between 1/2 and 1/3 during the Africa-verging deformation.

The evolution of the northern sector of the Calabria-Peloritani Arc in a semiquantitative palynspastic restoration.

TURCO, Eugenio;
1982

Abstract

The Calabria-Peloritani arc is an intriguing segment of the Apenninic-Maghrebic Chain, formed unlike the rest of the chain by several thrust sheets involving the crystalline basement. It is inserted in the zone of maximum distorsion of the orogenic system. According to the most recent interpretation (BONARDI et al., 1980) two sectors, North and South of the Soverato-Valle del Mesima alignment, can be distinguished in the arc. They arc characterized by rather a different Alpine history. The present paper is an attempt to outline the evolution of the Northern sector by a semiquantitative palyn- spastic restoration of the main stages of the Alpine cycle. Among the proposed explanatory models the one considering the arc as a fragment of the Europe-verging Alpine chain overthrust upon the Africa-verging Apenninic chain was assumed for the only sector of interest as the best fitting the analytical data. However it was necessary to intro- duce some modifications in the model as previously defined and to propose a solution, even if hypo- thetical, to many unsolved problems. The history described can he summarized as follow: after an abortive rifting in the Middle Triassic, a progressive crustal extension, culminating in a true rifting in the Jurassic, individuated different palaeogeographic realms on the future African continental margin. At the opening of the Central Tethys, that in the tract of interest is supposed to have not reached a width more than some hundreds of Kms, a total width of 250 kms is evaluated for the portion of the African continental margin presently represented in the Calabria structure. It includes an Auslroalpine- Insubric domain and the inner border of the Apen- ninic domain. The problem of the beginning of the compression is discussed and in its first stage a contemporaneous subduction of both European and African plates is assumed as the more in agreement with the probable piling-up order of the nappes. This resulted in a consumption of oceanic and African continental lithosphere and in the build up of a chain (Eo-aipine) overturned toward an European foreland and formed by wedges of oceanic and flakes both of oceanic and of Austroalpine material. During the build up of the chain (Cretaceous-Paleogene) an early flysch basin (Cilento-Sicilide basin) individualized by laceration of a zone of crustal weackness possibly extending northward of the given area and between the "Insubric" and the Apenninic domains. After the collision of the two continents the compression continued by subduction of the African continental lithosphere alone and all the nappes were wedges verging toward an African foreland. A fragment of the Eo-alpine chain overthrust the "Insubric" domain that was progressively interested by deformation. In the Early Miocene the Eo- alpine building and the "Insubric" nappes overthrust as an unique tectonic element the inner border of the Apenninic domain. Further almost passive transport during the build up of the Apenninic chain, a partial disrup- tion by the opening of Tyrrhenian sea and a block faulting led to the present day setting. The palynspastic restoration gives also a rough evaluation of the crustal shortage in about 1/2 of the original width during the Europe-verging and between 1/2 and 1/3 during the Africa-verging deformation.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11581/102896
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